THERMO INSTRUMENT SYSTEMS INC
8-K, 1998-01-16
MEASURING & CONTROLLING DEVICES, NEC
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<PAGE>
 
                      SECURITIES AND EXCHANGE COMMISSION

                            Washington, D.C.  20549

                  ___________________________________________


                                   FORM 8-K


                                CURRENT REPORT

                      Pursuant to Section 13 or 15(d) of
                      the Securities Exchange Act of 1934



                                Date of Report
                      (Date of earliest event reported):

                               January 15, 1998

                   ________________________________________


                        THERMO INSTRUMENT SYSTEMS INC.
            (Exact name of Registrant as specified in its charter)


    Delaware                  1-9786                           04-2925809
(State or other             (Commission                     (I.R.S. Employer
jurisdiction of             File Number)                 Identification Number)
incorporation or
organization)


860 West Airport Freeway, Suite 301
Hurst, Texas                                                        76054
(Address of principal executive offices)                         (Zip Code)


                                 (817)485-6663
                        (Registrant's telephone number
                             including area code)
<PAGE>
 
Item 5.   Other Events
          ------------

          On January 15, 1998, Thermo Instrument Systems Inc. (the "Company")
executed an Underwriting Agreement and related Terms Agreement by and among
the Company, Thermo Electron Corporation ("Thermo Electron"), Lehman Brothers
Inc., Goldman, Sachs & Co. and Smith Barney Inc. in connection with the public
offering of $250,000,000 aggregate principal amount of the Company's 4%
Convertible Subordinated Debentures due 2005 (the "Debentures") pursuant to the
Company's and Thermo Electron's shelf registration statement on Form S-3 (Reg.
Nos. 333-32031 and 333-32031-01). The Debentures will be convertible into shares
of the Company's Common Stock at a price of $35.65 per share. The Debentures
will be issued pursuant to a Subordinated Indenture (the "Indenture") by and
among the Company, Thermo Electron, as guarantor, and Bankers Trust Company, as
trustee.

     In the prospectus supplement for the offering of the Debentures, the 
Company reported the following recent developments:

     The Company has settled the post-closing adjustment with Fisons plc over 
the purchase price the Company paid for its acquisition of a substantial portion
of the businesses comprising the scientific instruments division of Fisons plc. 
See Note 4 to the Company's Consolidated Financial Statements for the fiscal 
year ended December 28, 1996. In the settlement, the purchase price was reduced 
by 22,150,000 British pounds sterling, and the Company received interest of 
2,331,783 British pounds sterling with respect to the purchase price refund.

     Earl R. Lewis, President and Chief Operating Officer, has been promoted to 
Chief Executive Officer of the Company.

     The Company's previously disclosed arbitration proceeding with five 
employees of its Epsilon Industrial, Inc. subsidiary is expected to conclude in 
the first quarter of 1998. See Note 8 to the Company's Consolidated Financial 
Statements for the fiscal year ended December 28, 1996. The employees are now 
claiming actual damages of $60 million, punitive damages of twice the actual 
damages, attorneys' fees and expenses, and pre-judgment and post-judgment 
interest.

Item 7.   Financial Statements, Pro Forma Financial Information and Exhibits
          ------------------------------------------------------------------

          (a)    Financial Statements of Business Acquired: not applicable.

          (b)    Pro Forma Financial Information: not applicable.

          (c)    Exhibits

                 1.1    Underwriting Agreement and related Terms Agreement,
dated January 15, 1998, by and among the Company, Thermo Electron, Lehman
Brothers Inc., Goldman, Sachs & Co. and Smith Barney Inc.

                 1.2    Terms Agreement, dated January 15, 1998, by and among 
the Company, Thermo Electron, Lehman Brothers Inc., Goldman, Sachs & Co. and 
Smith Barney Inc.

                 4.1    Subordinated Indenture, dated January 15, 1998, by and
among the Company, Thermo Electron, and Bankers Trust Company.

                 4.2    Officers' Certificate dated January 15, 1998, pursuant
to Sections 301 and 303 of the Indenture.

                 4.3    Form of Definitive Registered Debentures.

                 4.4    Form of Global Registered Debenture.

                 4.5    Form of Definitive Bearer Debentures and Coupons.
     
                 4.6    Form of Temporary Global Bearer Debenture.

                12.1    Computation of Ratio of Earnings to Fixed Charges of the
Company.

                12.2    Computation of Ratio of Earnings to Fixed Charges of 
Thermo Electron.
<PAGE>
 
                                   SIGNATURE



     Pursuant to the requirements of the Securities Exchange Act of 1934, the
Registrant has duly caused this report to be signed on its behalf by the
undersigned, thereunto duly authorized, on this 15th day of January, 1998.



                                   THERMO INSTRUMENT SYSTEMS INC.


                                   By: /s/ Melissa F. Riordan
                                       ______________________
                                       Melissa F. Riordan

                                       Treasurer
<PAGE>
 
                                 EXHIBIT INDEX

Exhibit No.            Description

     1.1       Underwriting Agreement and related Terms Agreement, dated January
15, 1998, by and among the Company, Thermo Electron, Lehman Brothers Inc.,
Goldman Sachs & Co. and Smith Barney Inc.

     1.2       Terms Agreement, dated January 15, 1998, by and among the 
Company, Thermo Electron, Lehman Brothers Inc., Goldman, Sachs & Co. and Smith 
Barney Inc.

     4.1       Subordinated Indenture, dated January 15, 1998, by and among the
Company, Thermo Electron, and Bankers Trust Company.

     4.2       Officers' Certificate dated January 15, 1998, pursuant to
Sections 301 and 303 of the Indenture.

     4.3       Form of Definitive Registered Debentures.

     4.4       Form of Global Registered Debenture.

     4.5       Form of Definitive Bearer Debentures and Coupons.

     4.6       Form of Temporary Global Bearer Debenture.

    12.1       Thermo Instrument Systems Inc. Ratio of Earnings to Fixed
Charges.

    12.2       Thermo Electron Corporation Ratio of Earnings to Fixed Charges.


<PAGE>
 
                                                                     EXHIBIT 1.1
                                 $250,000,000

                        THERMO INSTRUMENT SYSTEMS INC.
                          THERMO ELECTRON CORPORATION

                            UNDERWRITING AGREEMENT
                            ----------------------
                                        

                                                           January 15, 1998
Lehman Brothers Inc.
Three World Financial Center
New York, New York 10285

Goldman, Sachs & Co.
85 Broad Street
New York, New York 10004

Smith Barney Inc.
Seven World Trade Center
New York, New York 10048

Dear Sirs:

     Thermo Instrument Systems Inc., a Delaware corporation (the
"Company"), proposes to issue and sell up to $250,000,000 of a combination of
 -------                                                                     
the Company's (i) debt securities, consisting of debentures, notes or other
unsecured evidences of indebtedness which may be either senior debt securities
(the "Senior Debt Securities") or subordinated debt securities (the
"Subordinated Debt Securities"), and (ii) shares of common stock, $.10 par value
(the "Common Stock"), in one or more offerings on terms and conditions
      -------------                                                   
determined at the time of sale.  Debt Securities that may be issued by the
Company will be guaranteed (the "Guarantees"), on either a senior or
                                 ----------                         
subordinated basis, by Thermo Electron Corporation, a Delaware corporation and
the corporate parent of the Company ("Thermo Electron").  The Debt Securities,
                                      ---------------                         
the Common Stock and the Guarantees are sometimes referred to herein as the
                                                                           
"Offered Securities."  The Senior Debt Securities will be issued pursuant to an
- -------------------                                                            
indenture (the "Senior Indenture") among the Company, Thermo Electron and
                ----------------                                         
Bankers Trust Company, as trustee (the "Trustee") and the Subordinated Debt
                                        -------                            
Securities will be issued pursuant to an indenture (the "Subordinated
Indenture") among the Company, Thermo Electron and the Trustee (the Senior
Indenture and Subordinated Indenture are sometimes hereinafter collectively
referred to as the "Indentures" and individually as an "Indenture").

     From time to time, the Company and Thermo Electron may enter into one
or more terms agreements in substantially the form attached hereto as Schedule I
(each a "Terms Agreement") that provide for the sale of such designated Offered
         ---------------                                                       
Securities to, and the purchase and offering thereof by, either or both of you,
as applicable, and the underwriter or underwriters named 
<PAGE>
 
                                      -2-



therein (the "Underwriters" or "you", which terms shall include the underwriter
              ------------      --- 
or underwriters named therein whether acting alone in the sale of Offered
Securities or as members of an underwriting syndicate), and the provisions set
forth herein (except for provisions which relate to securities other than
Offered Securities designated in the applicable Terms Agreement) shall be
incorporated by reference in any such Terms Agreement.  The applicable Terms
Agreement, including the provisions incorporated therein by reference, is herein
referred to as "this Agreement."
                --------------  

     1.   Representations, Warranties and Agreements of the Company and
          ------------------------------------------------- -----------
Thermo Electron. The Company and Thermo Electron, jointly and severally,
- ---------------                                                         
represent and warrant as to the Company (and its Subsidiaries) as follows,
Thermo Electron represents and warrants as to itself (and its Subsidiaries) as
follows, and the Company and Thermo Electron, jointly and severally, agree with
each Underwriter as follows:

          (a)  A registration statement on Form S-3 (No. 333-32031 and -32031-
01), including a prospectus relating to the Offered Securities of the Company
and Thermo Electron for the registration of such securities under the United
States Securities Act of 1933, as amended (the "Securities Act"), has (i) been
                                                --------------                
prepared by the Company and Thermo Electron in material conformity with the
requirements of the Securities Act and the rules and regulations (the "Rules
                                                                       -----
and Regulations") of the United States Securities and Exchange Commission (the
    -----------                                                               
"Commission") thereunder, (ii) been filed with the Commission under the
- -----------                                                            
Securities Act and (iii) become effective under the Securities Act; and each
Indenture has been qualified under the Trust Indenture Act of 1939, as amended
(the "Trust Indenture Act").  Copies of such registration statement and any
      ----- -------------                                                  
amendments thereto have been delivered by the Company and Thermo Electron to
you.  As used in this Agreement, "Effective Date" means the date and the time as
                                  --------------                                
of which such registration statement, or the most recent post-effective
amendment thereto, if any, was declared effective by the Commission;
                                                                    
"Registration Statement" means the registration statement in the form it became
- -----------------------                                                        
or becomes, as the case may be, effective (including, if the Company omitted
information from the registration statement pursuant to Rule 430A(a) or files a
term sheet pursuant to Rule 434 of the Rules and Regulations, the information
deemed to be a part of the registration statement at the time it became
effective pursuant to Rule 430A(b) or Rule 434(d) of the Rules and Regulations),
including all documents incorporated by reference or deemed to be incorporated
by reference therein and the exhibits thereto and, in the event of any amendment
thereto or the filing of any abbreviated registration statement pursuant to Rule
462(b) of the Rules and Regulations relating thereto after the effective date of
such registration statement, shall also mean (from and after the effectiveness
of such amendment or the filing of such abbreviated registration statement) such
registration statement as so amended, together with any such abbreviated
registration statement; "Base Prospectus" means the prospectus included in the
                         ---------------                                      
Registration Statement; "Preliminary Prospectus" means any preliminary form of
                         ----------------------                               
prospectus supplement specifically relating to designated Offered Securities in
the form filed with, or transmitted for filing to the Commission pursuant to
Rule 424 of the Rules and Regulations, together with any accompanying
prospectus; "Prospectus Supplement" means any prospectus supplement specifically
             ---------------------                                              
relating to designated Offered Securities in the form filed with, or transmitted
for filing to, the Commission pursuant to Rule 424 under the Securities Act;
                                                                            
"Prospectus" means the Base Prospectus together with the Prospectus Supplement
- -----------                                                                   
specifically 
<PAGE>
 
                                      -3-

relating to designated Offered Securities in the form first filed with, or
transmitted for filing to, the Commission pursuant to Rule 424 under the
Securities Act following the execution of a Terms Agreement with respect to such
Offered Securities, except that if such Base Prospectus is amended or
supplemented on or prior to the date on which such Prospectus Supplement was
first filed pursuant to Rule 424, the term "Prospectus" shall refer to the Base
Prospectus as so amended or supplemented and as supplemented by such Prospectus
Supplement; "Base Prospectus," "Prospectus," "Preliminary Prospectus" and 
             ---- ----------    ----------    ----------------------      
"Prospectus Supplement" shall include in each case the documents, if any, filed 
 ---------- ---------- 
by the Company or Thermo Electron with the Commission pursuant to the United
States Securities Exchange Act of 1934, as amended (the "Exchange Act"), and
                                                         -------- ---
incorporated by reference therein; and "supplement" and "amendment", shall be
                                        ----------       ---------
deemed to refer to and include any documents incorporated by reference pursuant
to Item 12 of Form S-3 under the Securities Act that are filed subsequent to the
date of the Base Prospectus by the Company or Thermo Electron with the
Commission pursuant to the Exchange Act. Any reference to any amendment to the
Registration Statement shall be deemed to include any annual report of the
Company or Thermo Electron, as the case may be, filed with the Commission
pursuant to Section 13(a) or 15(d) of the Exchange Act after the Effective Date
that is incorporated by reference in the Registration Statement. Any reference
herein to information "contained in," "contemplated by," "described in,"
                       --------- --    ------------ --    --------- --
"disclosed in," "included in" or "set forth in" any of the foregoing documents,
 --------- --    -------- --      --- ----- --
or words of similar effect, shall be deemed to include the documents
incorporated or deemed to be incorporated by reference therein.

          (b)  The Registration Statement complies as to form in all material
respects, and the Prospectus and any further amendments or supplements to the
Registration Statement or the Prospectus will, when they become effective or are
filed with the Commission, as the case may be, comply as to form in all material
respects to the requirements of the Securities Act and the Rules and Regulations
and do not and will not, as of the applicable Effective Date (as to the
Registration Statement and any amendment thereto) and as of the applicable
filing date and applicable Closing Date (as to the Prospectus and any amendment
or supplement thereto) contain an untrue statement of a material fact or omit to
state a material fact required to be stated therein or necessary to make the
statements therein (in the case of the Prospectus, in light of the circumstances
in which they were made), not misleading; provided, however, that no
representation or warranty is made as to information contained in or omitted
from the Registration Statement or the Prospectus in reliance upon and in
conformity with written information furnished to the Company by or on behalf of
any Underwriter specifically for use in the Registration Statement or the
Prospectus.  To the extent applicable, the copies of the Registration Statement
and each other document referred to in subparagraph (a) above that have been or
will be furnished to the Underwriters have been and will be identical to the
electronically transmitted copies thereof filed with the Commission pursuant to
the Commission's Electronic Data Gathering, Analysis and Retrieval System
("EDGAR"), except to the extent permitted by Regulation S-T.
 -------                                                     

          (c)  If the Offered Securities are Debt Securities:  Each Indenture
conforms in all material respects to the requirements of the Trust Indenture Act
and the applicable rules and regulations thereunder.
<PAGE>
 
                                      -4-

          (d)  The documents incorporated or deemed to be incorporated by
reference in the Prospectus, when they were filed with the Commission, conformed
in all material respects with the requirements of the Securities Act or the
Exchange Act, as applicable, and the rules and regulations of the Commission
thereunder, and none of such documents contained an untrue statement of a
material fact or omitted to state a material fact required to be stated therein
or necessary to make the statements therein, not misleading; and any further
documents so filed and incorporated or deemed to be incorporated by reference in
the Prospectus, when such documents become effective or are filed with the
Commission, as the case may be, will conform in all material respects to the
requirements of the Securities Act or the Exchange Act, as applicable, and the
rules and regulations of the Commission thereunder and will not contain an
untrue statement of a material fact or omit to state a material fact required to
be stated therein or necessary to make the statements therein not misleading.

          (e)  The Company and Thermo Electron and each of their respective
Subsidiaries have been duly incorporated and are validly existing as
corporations in good standing under the laws of their respective jurisdictions
of incorporation. The Company, Thermo Electron and each of their respective
Subsidiaries are duly qualified to do business and are in good standing as
foreign corporations in each jurisdiction in which their respective ownership or
lease of property or the conduct of their respective businesses requires such
qualification, except where the failure to be so qualified and in good standing
would not have a material adverse effect on the consolidated financial
condition, shareholders' equity, results of operations or business of such
corporation (meaning herein the Company or Thermo Electron, as the case may be)
and its Subsidiaries taken as a whole, and where so qualified have all corporate
power and authority necessary to own, lease or operate their respective
properties and to conduct the businesses in which they are engaged as described
in the Prospectus.  Except as described in the Prospectus, the Company, Thermo
Electron and their respective Subsidiaries hold all material licenses,
certificates and permits from governmental authorities necessary for the conduct
of their respective businesses as described in the Prospectus.

          (f)  The Company and Thermo Electron had an authorized and issued
capitalization as set forth in the Prospectus (as of the date specified
therein), and all of the issued and outstanding shares of capital stock of the
Company and Thermo Electron have been duly and validly authorized and issued,
are fully paid and non-assessable and conform in all material respects to the
description thereof contained in the Prospectus; and all of the issued and
outstanding shares of capital stock of each Subsidiary of the Company have been
duly and validly authorized and issued and are fully paid and non-assessable and
(except for directors' qualifying shares, as set forth in the Prospectus and
certain shares owned by Thermo Electron or any of its Subsidiaries) are owned
directly or indirectly by the Company, free and clear of all liens,
encumbrances, equities or claims, except that certain of such shares are
reserved for transfer pursuant to stock option and other benefit plans under
which options to purchase common stock of such corporation owned by its
corporate parent or Thermo Electron or any of its Subsidiaries are granted to
certain employees, directors or consultants of Thermo Electron, the Company and
their Subsidiaries.
<PAGE>
 
                                      -5-

          (g)  If the Offered Securities are Debt Securities:  The Debt
Securities have been duly and validly authorized by the Company and, when duly
executed, issued and delivered by the Company, and authenticated by the Trustee
pursuant to the provisions of the Senior Indenture or the Subordinated
Indenture, as the case may be, against payment therefor as provided in this
Agreement, will constitute valid and legally binding obligations of the Company
entitled to the benefits of the Indenture and enforceable against the Company in
accordance with their terms, subject to the effects of bankruptcy, insolvency,
fraudulent conveyance and transfer, reorganization, moratorium, or other similar
laws now or hereafter in effect relating to creditors' rights generally
("applicable bankruptcy laws") and general equitable principles (whether
 ----------------------------                                            
considered in a proceeding in equity or at law); and the Debt Securities, when
issued and delivered, will conform in all material respects to the description
thereof contained in the Prospectus.  The Guarantees have been duly and validly
authorized by Thermo Electron and, when duly executed, issued and delivered by
Thermo Electron, and, if required, authenticated by the Trustee pursuant to the
provisions of the Indenture, against payment for the Debt Securities as provided
in this Agreement, will constitute valid and legally binding obligations of
Thermo Electron entitled to the benefits of such Indenture and enforceable
against Thermo Electron in accordance with their terms, subject to the effects
of applicable bankruptcy laws and general equitable principles (whether
considered in a proceeding in equity or at law); and the Guarantees, when issued
and delivered, will conform in all material respects to the description thereof
contained in the Prospectus.

          (h)  If the Offered Securities are Debt Securities: Each Indenture has
been duly authorized by the Company and Thermo Electron, and when duly executed
by the proper officers of the Company and Thermo Electron (assuming due
execution and delivery by the Trustee) and delivered by the Company and Thermo
Electron will constitute a valid and legally binding obligation of the Company
and Thermo Electron enforceable against them in accordance with its terms,
subject to the effects of applicable bankruptcy laws and general equitable
principles (whether considered in a proceeding in equity or at law); and each
Indenture conforms in all material respects to the description thereof contained
in the Prospectus.

          (i)  If the Offered Securities are shares of Common Stock:  The
unissued shares of Common Stock have been duly and validly authorized and, when
issued and delivered against payment therefor as provided in this Agreement,
such shares will be duly and validly issued, fully paid and non-assessable and
will conform in all material respects to the description thereof contained in
the Prospectus.

          (j)  If the Offered Securities are convertible into shares of Common
Stock: The shares of Common Stock reserved for issuance upon conversion of
convertible Debt Securities have been validly authorized and reserved for such
purpose; and, if and when any of such convertible Debt Securities are converted
into shares of Common Stock in accordance with the conversion rights so
provided, such shares of Common Stock will be validly  issued, fully paid and
non-assessable and delivered in accordance with the terms of the Company's
corporate charter and by-laws; and when issued and delivered, such Common Stock
will conform in all material respects to the description thereof contained in
the Prospectus.
<PAGE>
 
                                      -6-

          (k)  If the Offered Securities are shares of Common Stock: There are
no preemptive or other rights to subscribe for or to purchase, nor any
restrictions upon the voting or transfer of any shares of the Common Stock,
including any Common Stock issuable upon conversion of any Offered Securities,
in each case, pursuant to the Company's corporate charter or by-laws or any
agreement or other instrument to which the Company is a party.

          (l)  This Agreement has been duly authorized, executed and delivered
by the Company and Thermo Electron.

          (m)  The execution, delivery and performance of this Agreement by the
Company and Thermo Electron, the execution, delivery and performance of each
Indenture (if the Offered Securities are Debt Securities) by the Company and
Thermo Electron, and the consummation of the transactions contemplated hereby
and thereby, and the issuance and delivery of the Offered Securities will not
conflict with or result in a breach or violation of any of the terms or
provisions of, or constitute a default under any indenture, lien, charge or
encumbrance upon any property or mortgage, deed of trust, loan agreement, or
other agreement or instrument to which the Company or Thermo Electron or any of
their respective Subsidiaries is a party or by which it or any of them is bound
or to which any of the property or assets of the Company or Thermo Electron or
any of their respective Subsidiaries is subject, except in each case for such
conflicts, breaches, violations or defaults which would not have a material
adverse effect on the consolidated financial condition, shareholders' equity,
results of operations or business of such corporation and its Subsidiaries taken
as a whole, nor will such action result in any violation of the provisions of
the charter or by-laws of any of such corporation or any of their respective
Subsidiaries or any statute or any order, rule or regulation of any court or
governmental agency or body having jurisdiction over the Company or Thermo
Electron or any of their respective Subsidiaries or any of their respective
material properties or assets; and except for the registration of the Offered
Securities under the Securities Act, the qualification of each Indenture under
the Trust Indenture Act, and such consents, approvals, authorizations,
registrations or qualifications as may be required under the Exchange Act or
applicable state or foreign securities laws or by the National Association of
Securities Dealers, Inc.  in connection with the purchase and distribution of
the Offered Securities by the Underwriters, no consent, approval, authorization
or order of, or filing, registration or qualification of or with, any such court
or governmental agency or body is required for the execution, delivery and
performance of this Agreement and the Indentures (if the Offered Securities are
Debt Securities) by the Company or Thermo Electron and the consummation by the
Company and Thermo Electron of the transactions contemplated hereby and thereby.

          (n)  Except as described in the Registration Statement or the
Prospectus there are no agreements or understandings between the Company and any
person granting such person the right to require the Company to file a
registration statement under the Securities Act with respect to any securities
of the Company owned or to be owned by such person or to require the Company to
include such securities in the securities registered pursuant to the
Registration Statement or in any securities being registered pursuant to any
other registration statement filed by the Company under the Securities Act.
<PAGE>
 
                                      -7-

          (o)  Neither the Company nor any of its Subsidiaries, nor Thermo
Electron nor any of its Subsidiaries has sustained, since the date of the latest
financial statements included or incorporated by reference in the Prospectus,
any loss or interference with its business from fire, explosion, flood or other
calamity, whether or not covered by insurance, or from any labor
dispute or court or governmental action, order or decree, which is material to
the Company and its Subsidiaries taken as a whole, or to Thermo Electron and its
Subsidiaries taken as a whole, as the case may be, otherwise than as set forth
or contemplated in the Prospectus; except as contemplated by or disclosed in the
Prospectus, since such date, neither the Company nor Thermo Electron has
incurred any material liability or obligation, or entered into any material
transaction, or declared or paid any dividend on its capital stock or issued or
granted any securities; and except as contemplated by or disclosed in the
Prospectus, since such date, there has not been any material change in the
capital stock of the Company or any of its Subsidiaries or of Thermo Electron or
any of its Subsidiaries or any material change in the consolidated long-term
debt of the Company or of Thermo Electron, or any material adverse change, or
any development involving a prospective material adverse change, in or affecting
the business, management, financial condition, shareholders' equity or results
of operations of the Company and its Subsidiaries taken as a whole, or of Thermo
Electron and its Subsidiaries taken as a whole, otherwise than as set forth or
contemplated in the Prospectus.

          (p)  Arthur Andersen LLP, which has certified the financial statements
of the Company and Thermo Electron included in the Registration Statement, and
any other accounting firm which has certified any financial statements contained
in the Registration Statement, and whose reports appear in the Prospectus or are
incorporated by reference therein, are independent public accountants as
required by the Securities Act and the Rules and Regulations.

          (q)  The financial statements (including the related notes and
supporting schedules) filed as part of the Registration Statement or included or
incorporated by reference in the Prospectus present fairly in all material
respects the financial condition and results of operations of the entities
purported to be shown thereby at the dates and for the periods indicated; and
have been prepared in conformity with United States generally accepted
accounting principles or International Accounting Standards, as the case may be,
applied on a consistent basis throughout the periods involved, except as
otherwise expressly set forth therein.

          (r)  Except as described in the Prospectus, there are no legal or
governmental proceedings pending or threatened by or against the Company or
Thermo Electron or any of their respective Subsidiaries or of which any material
property or assets of the Company or Thermo Electron or any of their respective
Subsidiaries is the subject which are required to be disclosed in the
Registration Statement or the Prospectus.

          (s)  There are no contracts or other documents which are required to
be described in the Prospectus or filed as exhibits to the Registration
Statement by the Securities Act or by the Rules and Regulations which have not
been described in the Prospectus or filed as exhibits to the Registration
Statement or incorporated therein by reference under the Rules and Regulations.

          (t)  Neither the Company, Thermo Electron nor any of their respective
Subsidiaries is
<PAGE>
 
                                      -8-

               (i)   in violation in any material respect of its corporate
charter or by-laws, or

               (ii)  except as described in the Prospectus, in default in any
material respect, and no event has occurred which, with notice or lapse of time
or both, would constitute such a default, in the due performance or observance
of any term, covenant or condition contained in any material indenture,
mortgage, deed of trust, loan agreement or other agreement to which the Company
or Thermo Electron or any of their respective Subsidiaries is a party or by
which it or any of them is or may be bound or to which any of the properties or
assets of the Company or Thermo Electron or any of their respective Subsidiaries
is subject, except for such defaults which would not have a material adverse
effect on the consolidated financial condition, shareholders' equity, results of
operations or business of the Company and its Subsidiaries taken as a whole and
Thermo Electron and its Subsidiaries taken as a whole, as the case may be; or

               (iii) except as described in the Prospectus, in violation in any
material respect of any law, ordinance, governmental rule, regulation or court
decree to which the Company or Thermo Electron or any of their respective
Subsidiaries or its or any of their respective property or assets may be subject
or has failed to obtain any material license, permit, certificate, franchise or
other governmental authorization or permit necessary to the ownership of its or
their property or to the conduct of its or their business, except for such
violations or failures which would not reasonably be expected to have a material
adverse effect on the consolidated financial condition, shareholders' equity,
results of operations or business of the Company and its Subsidiaries taken as a
whole and Thermo Electron and its Subsidiaries taken as a whole, as the case may
be.

          (u)  Except as described in the Prospectus, the Company and Thermo
Electron and their respective Subsidiaries own, or have valid rights to use, all
items of real and personal property which are material to the business of the
Company and its Subsidiaries taken as a whole and Thermo Electron and its
Subsidiaries taken as a whole, as the case may be, free and clear of all liens,
encumbrances and claims which may materially interfere with the consolidated
financial condition, shareholders' equity, results of operations or business of
such corporation and its Subsidiaries taken as a whole.

          (v)  Except as described in the Prospectus, the Company and Thermo
Electron and their respective Subsidiaries own or possess adequate licenses or
other rights to use all intellectual property rights, including patents,
trademarks, service marks, trade names, copyrights or know-how, necessary to
conduct their respective businesses as described in the Prospectus, except where
such failure, singularly or in the aggregate, would not have a material adverse
effect on the consolidated financial condition, shareholders' equity, results of
operations or business of the Company and its Subsidiaries taken as a whole and
Thermo Electron and its Subsidiaries taken as a whole, as the case may be, and,
except as described in the Prospectus, none of the Company or Thermo Electron or
their respective Subsidiaries has received any notice of infringement of or
conflict with (or knows of any such infringement of or conflict with) rights or
claims of others with respect to any patents, patent applications, trademarks,
service marks, trade names, copyrights or know-how, that is reasonably likely to
result in a material adverse effect on the consolidated financial condition,
shareholders' equity, results of operations 
<PAGE>
 
                                      -9-

or business of the Company and its Subsidiaries taken as a whole and Thermo
Electron and its Subsidiaries taken as a whole, as the case may be.

          (w)  Neither the Company, nor Thermo Electron, nor any of their
respective Subsidiaries,  is an "investment company" within the meaning of such
term under the Investment Company Act of 1940 and the rules and regulations of
the Commission thereunder.

          (x)  Since the date which is three months prior to this Agreement, no
debt rating assigned to Thermo Electron by any "nationally recognized
statistical rating organization," as that term is defined by the Commission for
purposes of Rule 436(g)(2) of the Rules and Regulations, has been lowered or, to
Thermo Electron's knowledge, threatened to be lowered by any such rating
organization nor, to Thermo Electron's knowledge, has it been placed under
surveillance or review by any such rating organization.

          (y)  Any certificate signed by any officer of the Company or Thermo
Electron and delivered to the Underwriters or to counsel for the Underwriters
pursuant to this Agreement shall be deemed a representation and warranty
hereunder by the Company or Thermo Electron, as the case may be, to each
Underwriter as to the matters covered thereby.

     2.   Purchase of the Offered Securities by the Underwriters.  On the
          ------------------------------------------------------         
basis of the representations and warranties contained in, and subject to the
terms and conditions set forth herein, the Company agrees to sell to the
Underwriters and each of the Underwriters, severally and not jointly, agrees to
purchase from the Company, at the price and/or principal amount, as the case may
be, set forth in the applicable Terms Agreement and in the respective amounts
and number of shares, as the case may be, of the designated Offered Securities
set forth opposite the name of each such Underwriter in Exhibit A to such Terms
                                                        ---------              
Agreement.  In addition, the Company may specify in any Terms Agreement relating
to any offering that the Company thereby grants to the Underwriters an option to
purchase up to the number of shares or principal amount of additional Offered
Securities (the "Option Securities," and if so purchased shall also be "Offered
                 -----------------                                      -------
Securities" herein) in the amount set forth in such Terms Agreement.  The option
- ----------                                                                      
thereby granted is exercisable as provided in Section 4 hereof, shall expire at
the close of business on the 30th day after the date of the applicable Terms
Agreement (unless otherwise specified therein) and will be granted solely for
the purpose of covering over-allotments which may be made in connection with the
applicable offering.  The Option Securities shall be purchased severally for the
account of the Underwriters in proportion to the number or amount of Offered
Securities set opposite the name of such Underwriters in Exhibit A of the
                                                         ---------       
applicable Terms Agreement.  The respective purchase obligations of each
Underwriter with respect to the Option Securities shall be adjusted by the
managing Underwriter so that no Underwriter shall be obligated to purchase
Option Securities in amounts other than in 100 share or $1,000 principal amount
increments.

     3.   Offering of the Offered Securities by the Underwriters.  
          ----------------------------------------- ------------          
          (a)  The several Underwriters propose to offer the Offered
Securities for sale upon the terms and conditions set forth in the Prospectus
and any amendment or supplement thereto relating to the Offered Securities.
<PAGE>
 
                                      -10-

          (b)  Each Underwriter severally agrees to comply with the
following restrictions in the offering and sale of any Debt Securities:

               (i)   except to the extent permitted under U.S. Treasury
Regulation (S)1.163-5(c)(2)(i)(D) (the  "D Rules"), (A) the Underwriters have 
                                         ------- 
not offered or sold, and during the restricted period will not offer or sell,
Debt Securities in bearer form to a person who is within the United States or
its possessions or to a United States person, and (B) the Underwriters have not
delivered, and will not deliver, within the United States or its possessions
definitive Debt Securities in bearer form that are sold during the restricted
period;

               (ii)  The Underwriters and each of their affiliates that is
acquiring from them Debt Securities in bearer form for the purposes of offering
or selling such Debt Securities during the restricted period, presently have in
effect, and throughout the restricted period will have in effect, procedures
reasonably designed to ensure that such Underwriters and such affiliates and
their respective employees or agents who are directly engaged in selling Debt
Securities in bearer form are aware that such Debt Securities may not be offered
or sold during the restricted period to a person who is within the United States
or its possessions or to a United States person, except as permitted by the D
Rules;

               (iii) Each Underwriter that is a United States person, if
any, is acquiring, either as agent or on its own behalf, the Debt Securities in
bearer form for purposes of resale in connection with their original issuance,
and if it retains Debt Securities in bearer form for its own account, it will
only do so in accordance with the requirements of U.S. Treasury Regulation
(S)1.163-5(c)(2)(i)(D)(6); and

               (iv)  With respect to each of the Underwriters' affiliates
that acquires from such Underwriter Debt Securities in bearer form for the
purpose of offering or selling such Debt Securities during the restricted
period, such Underwriter agrees that it will obtain from such affiliate for the
benefit of the Company the representations, warranties, covenants and agreements
contained in clauses (i), (ii) and (iii).

Terms used in this Section 3(b) have the meanings given to them by the U.S.
Internal Revenue Code and regulations thereunder, including the D Rules.

          (c)  Each Underwriter severally represents and agrees that (i) it has
not offered or sold and will not offer or sell in the United Kingdom any Offered
Securities except to persons whose ordinary activities involve them in
acquiring, holding, managing or disposing of investments (as principal or agent)
for the purpose of their businesses or otherwise in circumstances which have not
resulted and will not result in an offer to the public in the United Kingdom
within the meaning of the Public Offers of Securities Regulations 1995 (the
"Regulations") or the Financial Services Act 1986, (ii) it has complied and will
 ------------
comply with all applicable provisions of the Financial Services Act 1986 and the
Regulations with respect to anything done by it in relation to the Offered
Securities in, from or otherwise involving the United Kingdom and (iii) it has
only issued or passed on, and will only issue or pass on, in the United Kingdom
any document 
<PAGE>
 
                                      -11-

received by it in connection with the issue of the Offered Securities if that
person is of a kind described in Article 11(3) of the Financial Services Act
1986 (Investment Advertisements) (Exemptions) Order 1996, as amended by article
4 of the Financial Services Act 1986 (Investment Advertisements) (Exemptions)
Order 1997, or is a person to whom the document may otherwise lawfully be issued
or passed on.

          (d)  Each Underwriter, jointly and severally, represents and warrants
that they have not entered into, and agree that they will not enter into, any
contractual arrangement with respect to the distribution or delivery of the Debt
Securities in bearer form, except with their respective affiliates, without the
prior written consent of the Company or pursuant to a form of selling agreement
containing restrictions substantially to the effect set forth in paragraph (b)
above.

     4.   Delivery of and Payment for the Offered Securities.  Delivery of
          --------------------------------------------------
and payment for the Offered Securities shall be made at the headquarters office
of the managing Underwriter, or at such other location as may be agreed upon by
the Underwriters and the Company, at 10:00 a.m., Eastern time, on the third
business day (or on the fourth business day, if permitted by the Rules and
Regulations) following the date of this Agreement, or at such other time and
date as shall be agreed upon (each such date and time of payment and delivery
being herein called the "Closing Date") in the manner set forth in the
                         ------------                                 
applicable Terms Agreement.  Time shall be of the essence, and delivery at the
time and place specified pursuant to this Agreement is a further condition of
the obligation of each Underwriter hereunder. Upon delivery, the Offered
Securities shall be registered in such names and in such denominations as the
Underwriters shall request in writing not less than two full business days prior
to the Closing Date.  For the purpose of expediting the checking and packaging
of the certificates for the Common Stock, the Company shall make the
certificates representing the Common Stock available for inspection by the
Underwriters in New York, New York, not later than 2:00 p.m., Eastern time, on
the business day prior to the Closing Date.  The Debt Securities of a series may
be issued in whole or in part in the form of one or more global securities that
will be deposited with, or on behalf of, one or more depositories, or a nominee
thereof, identified in the Prospectus relating to such series.  In such a case,
the manner of delivery of such global securities will be set forth in the
applicable Terms Agreement, or if not so set forth, as described in the
applicable Prospectus.  At any time on or before the thirtieth day after the
date of any Terms Agreement relating to Option Securities, if applicable, the
option granted in Section 2 may be exercised by written notice being given to
the Company by or on behalf of the Underwriters.  Such notice shall set forth
the aggregate number or amount of Option Securities as to which the option is
being exercised, the names in which the Option Securities are to be registered
if not in global form as set forth above, the denominations in which the shares
of Option Securities are to be issued and the date and time, as determined by
the Underwriters, when the Option Securities are to be delivered; provided,
however, that this date and time shall not be earlier than the Closing Date nor
earlier than the second business day after the date on which the option shall
have been exercised nor later than the third business day after the date on
which the option shall have been exercised.  The date and time the Option
Securities are delivered are sometimes referred to as the "Option Closing Date".
                                                           -------------------
Delivery of and payment for the Option Securities shall be made at the place
specified in the first sentence of the first paragraph of this Section 4 (or at
such other place as shall be determined by agreement between the Underwriters
and the Company at 10:00 a.m., Eastern time, on the Option Closing Date).  On
<PAGE>
 
                                      -12-

the Option Closing Date, the Company shall deliver or cause to be delivered the
certificates representing the Option Securities to the Underwriters for the
account of each Underwriter against payment to or upon the order of the Company
of the purchase price in the manner set forth in the applicable
Terms Agreement.  Time shall be of the essence, and delivery at the time and
place specified pursuant to this Agreement is a further condition of the
obligation of each Underwriter hereunder.  Upon delivery, the Option Securities
shall be registered in such names (if other than in global form) and in such
denominations as the Underwriters shall request in the aforesaid notice.  For
the purpose of expediting the checking and packaging of certificates for the
Option Securities that are Common Stock, the Company shall make the certificates
representing such Common Stock available for inspection by the Underwriters in
New York, New York, not later than 2:00 p.m., Eastern time, on the business day
prior to the Option Closing Date.

     5.   Further Agreements of the Company and Thermo Electron.  The Company 
          -----------------------------------------------------
and Thermo Electron each agree:

          (a)  To prepare the Prospectus in a form reasonably approved by the
Underwriters and to file such Prospectus pursuant to Rule 424(b) under the
Securities Act not later than the Commission's close of business on the second
business day following the execution and delivery of the applicable Terms
Agreement or, if applicable, such earlier time as may be required by Rule
430A(a)(3) under the Securities Act; after the date of  the applicable Terms
Agreement, to make no further amendment or supplement to the Registration
Statement or to the Prospectus prior to the applicable Closing Date except as
permitted herein; to advise the Underwriters, promptly after it receives notice
thereof, of the time when any amendment to the Registration Statement has been
filed or becomes effective or any supplement to the Prospectus or any amended
Prospectus has been filed and to furnish the Underwriters with copies thereof;
to file promptly all reports and any definitive proxy or information statements
required to be filed by the Company or Thermo Electron with the Commission
pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act subsequent to
the date of the Prospectus and for so long as the delivery of a prospectus is
required in connection with the offering or sale of the Offered Securities; to
advise the Underwriters, promptly after it receives notice thereof, of the
issuance by the Commission of any stop order or of any order preventing or
suspending the use of any Preliminary Prospectus or the Prospectus, of the
suspension of the qualification of the Offered Securities for offering or sale
in any jurisdiction, of the initiation or threatening of any proceeding for any
such purpose, of any request by the Commission for the amending or supplementing
of the Registration Statement or the Prospectus or for additional information;
and, in the event of the issuance of any stop order or of any order preventing
or suspending the use of any Preliminary Prospectus or the Prospectus or
suspending any such qualification, to use promptly its best efforts to obtain
its withdrawal;

          (b)  To furnish, promptly upon request by the representatives of the
Underwriters named in any applicable Terms Agreement (the "Representatives" and
                                                           ---------------     
if no Representatives are so named, then any references herein to the
Representatives shall be deemed to refer to the Underwriters), to the
Underwriters and to counsel for the Underwriters a copy of the Registration
Statement as originally filed with the Commission, and each amendment thereto
filed with the Commission, including all consents and exhibits filed therewith;
<PAGE>
 
                                      -13-

          (c)  To deliver promptly to the Underwriters such number of the
following documents as the Representatives shall reasonably request:

               (i)   conformed copies of the Registration Statement as
originally filed with the Commission and each amendment thereto (in each case
excluding exhibits other than this Agreement and the Indentures and such other
exhibits as the Underwriters may reasonably request),

               (ii)  each Preliminary Prospectus, the Prospectus and any amended
or supplemented Prospectus; and

               (iii) any document incorporated or deemed incorporated by
reference in the Prospectus (excluding exhibits thereto); and, if the delivery
of a prospectus is required at any time after the Effective Date in connection
with the offering or sale of the Offered Securities and if at such time any
events shall have occurred as a result of which the Prospectus as then amended
or supplemented would include an untrue statement of a material fact or omit to
state any material fact necessary in order to make the statements therein, in
the light of the circumstances under which they were made when such Prospectus
is delivered, not misleading, or, if for any other reason it shall be necessary
to amend or supplement the Prospectus (or to file under the Exchange Act any
document incorporated by reference in the Prospectus) in order to comply with
the Securities Act or the Exchange Act, to notify the Underwriters and, upon the
reasonable request of the Representatives, to file such document and to prepare
and furnish without charge to each Underwriter as many copies as the
Representatives may from time to time reasonably request of an amended or
supplemented Prospectus which will correct such statement or omission or effect
such compliance;

          (d)  To file promptly with the Commission any amendment to the
Registration Statement or the Prospectus or any supplement to the Prospectus
that may, in the judgment of the Company, Thermo Electron and the Underwriters,
be required by the Securities Act, or requested by the Commission;

          (e)  Prior to filing with the Commission any amendment to the
Registration Statement or supplement to the Prospectus, and promptly after
filing with the Commission (or, if between the signing of any applicable Terms
Agreement and the Closing Date thereunder, prior to filing with the Commission)
any document incorporated or deemed incorporated by reference in the Prospectus
or any Prospectus pursuant to Rule 424 of the Rules and Regulations, to furnish
a copy thereof to the Underwriters and counsel for the Underwriters;

          (f)  As soon as practicable after the date of this Agreement and every
Terms Agreement relating to designated Offered Securities, to make generally
available to its security holders an earnings statement of the Company and its
Subsidiaries, and if the applicable Offered Securities include Guarantees, an
earnings statement of Thermo Electron and its Subsidiaries (which, in each case,
need not be audited) complying with Section 11(a) of the Securities Act and 
<PAGE>
 
                                      -14-

the Rules and Regulations (including, at the option of the Company or Thermo
Electron, as the case may be, Rule 158);

          (g)  For a period of five years following the applicable Closing Date,
to furnish to the Underwriters, copies of all materials furnished by the Company
or Thermo Electron to all of its shareholders and all public reports and all
reports and financial statements furnished by the Company or Thermo Electron to
the principal national securities exchange upon which the Common Stock and any
other Offered Securities may be listed pursuant to requirements of or agreements
with such exchange or to the Commission pursuant to the Exchange Act or any
rules or regulations of the Commission thereunder;

          (h)  Promptly from time to time to take such action as the
Underwriters may reasonably request to qualify the Offered Securities for
offering and sale under the securities laws of such jurisdictions as the
Underwriters may reasonably request and to comply with such laws so as to permit
the continuance of sales and dealings therein in such jurisdictions for as long
as may be necessary to complete the distribution of the Offered Securities;
provided, however, that in connection therewith the Company and Thermo Electron
shall not be required to qualify as a foreign corporation or to file a general
consent to service of process in any jurisdiction where it is not so qualified;

          (i)  For a period of 90 days after the date of the Prospectus relating
to designated  Common Stock, or Offered Securities convertible into Common Stock
but only if specified in the applicable Terms Agreement (unless a different time
period is set forth in the applicable Terms Agreement), the Company and Thermo
Electron will not, directly or indirectly, offer for sale, sell or otherwise
dispose of (or enter into any hedging transaction or device which is designed
to, or could be expected to, result in the disposition by any person at any time
in the future of) any shares of Common Stock or any security convertible or
exchangeable for Common Stock (other than shares sold to Thermo Electron or its
Subsidiaries or shares issuable pursuant to employee benefit plans, stock option
plans or other compensation plans existing on the date thereof or pursuant to
then currently outstanding options, warrants or rights and other than the
issuance of shares of Common Stock as consideration for the acquisition of one
or more businesses provided that such Common Stock may not be resold prior to
the expiration of the 90-day period referenced above), or sell or grant options,
rights or warrants with respect to any shares of Common Stock (other than the
grant of options pursuant to option plans existing on the date thereof)
otherwise than in accordance with this Agreement without the prior written
consent of the Representatives;

          (j)  In the event designated Offered Securities are to be listed on a
securities exchange, to apply for any listing of such designated Offered
Securities on such securities exchange and to use its best efforts to complete
and maintain that listing, subject only to official notice of issuance, prior to
the relevant Closing Date, or if not so listed by such date, as soon as
practical thereafter. In the case of Offered Securities that are Debt Securities
to be listed on a foreign securities exchange, if the Company is not able to
effect or maintain such listing, it will use its best efforts to obtain and
maintain the quotation for, or listing of, such Debt Securities on 
<PAGE>
 
                                      -15-

such other stock exchange or exchanges as the Company may, with the approval of
the Representatives, determine;

          (k)  To apply the net proceeds from the sale of the Offered
Securities being sold by the Company as set forth in the Prospectus; and

          (l)  If the Offered Securities include Debt Securities, not to offer
or sell such Debt Securities in bearer form during the restricted period to a
person who is within the United States or its possessions or to a United States
person (each as defined in the U.S. Internal Revenue Code and regulations
thereunder, including the D Rules).

     6.   Expenses.  The Company agrees to pay:
          --------                     

          (a)  the costs incident to the authorization, issuance, sale and
delivery of the Offered Securities and any taxes payable in that connection
(other than taxes based on income);

          (b)  the costs incident to the preparation, printing and filing under
the Securities Act of the Registration Statement and any amendments and exhibits
thereto;

          (c)  the costs of distributing the Registration Statement as
originally filed and each amendment thereto and any post-effective amendments
thereof (including, in each case, exhibits), any Preliminary Prospectus, the
Prospectus and any amendment or supplement to the Prospectus or any document
incorporated or deemed incorporated by reference therein, all as provided in
this Agreement;

          (d)  the costs, if any, of printing this Agreement and any other
related documents in connection with the offering, purchase, sale and delivery
of the Offered Securities;

          (e)  any applicable listing or other fees;

          (f)  the filing fee of the National Association of Securities Dealers,
Inc. and the fees and expenses of qualifying the Offered Securities under the
securities laws of the several jurisdictions as provided in Section 5(h) and of
preparing, printing and distributing a Blue Sky Memorandum and a Legal
Investment Survey (including related fees and expenses of counsel to the
Underwriters);

          (g)  any fees charged by securities rating services for rating any
Offered Securities; and

          (h)  all other costs and expenses incident to the performance of the
obligations of the Company and Thermo Electron under this Agreement; provided
that, except as provided in this Section 6 and in Section 8 and Section 11, the
Underwriters shall pay the costs and expenses of their counsel, any transfer
taxes on the Offered Securities which they may sell, the expenses of advertising
any offering of the Offered Securities made by the Underwriters and all other
costs and expenses of the Underwriters and their counsel not enumerated in this
Section 6.
<PAGE>
 
                                      -16-

     7.   Conditions of Underwriters' Obligations.  The obligations of the
          ---------------------------------------                         
Underwriters to purchase and pay for any Offered Securities are subject to the
accuracy, when made, and on each Closing Date, of the representations and
warranties of the Company and Thermo Electron contained herein, to the
performance by the Company and Thermo Electron of their respective
obligations hereunder and under any Terms Agreement, and to each of the
following additional terms and conditions:

          (a)  At the applicable Closing Date, the Prospectus shall have been
timely filed with the Commission in accordance with Section 5(a); no stop order
suspending the effectiveness of the Registration Statement or any part thereof
shall have been issued and no proceeding for that purpose shall have been
initiated or threatened by the Commission; and any request of the Commission for
inclusion of additional information in the Registration Statement or the
Prospectus or otherwise shall have been complied with to the Representatives'
reasonable satisfaction.

          (b)  No Underwriter shall have discovered and disclosed to the Company
on or prior to any Closing Date that the Registration Statement or the
Prospectus or any amendment or supplement thereto contains an untrue statement
of a fact that, in the opinion of counsel for the Underwriters, is material or
omits to state a fact that, in the opinion of such counsel, is material and is
required to be stated therein or is necessary to make the statements therein (in
the case of the Prospectus, in light of the circumstances in which they were
made), not misleading.

          (c)  All corporate proceedings and other legal matters incident to the
authorization, form, validity and enforceability of this Agreement, any Terms
Agreement, the Indentures, the Offered Securities, the Registration Statement
and the Prospectus, and all other legal matters relating to this Agreement and
any Terms Agreement and the transactions contemplated hereby and thereby shall
be reasonably satisfactory in all material respects to counsel for the
Underwriters, and the Company and Thermo Electron shall have furnished to such
counsel all documents and information that they may reasonably request to enable
them to pass upon such matters.

          (d)  Seth H. Hoogasian, Esq., General Counsel to the Company and
Thermo Electron, shall have furnished to the Underwriters his opinion, in such
capacities, addressed to the Underwriters and dated the Closing Date, in form
and substance reasonably satisfactory to counsel for the Underwriters, to the
effect that:

               (i)   The Company and Thermo Electron and each of their
respective Significant Subsidiaries have been duly incorporated and are validly
existing as corporations in good standing under the laws of their respective
jurisdictions of incorporation. The Company, Thermo Electron and each of their
respective Significant Subsidiaries are duly qualified to do business and are in
good standing as foreign corporations in each jurisdiction in which their
respective ownership or lease of property or the conduct of their respective
businesses requires such qualification except where the failure to be so
qualified and in good standing would not have a material adverse effect on the
consolidated financial condition, shareholders' equity,
<PAGE>
 
                                      -17-

results of operations or business of such corporation and its Subsidiaries taken
as a whole, and have all corporate power and authority necessary to own, lease
or operate their respective properties and to conduct the businesses in which
they are engaged as described in the Prospectus;

               (ii)  The Company and Thermo Electron have an authorized
capitalization as set forth in the Prospectus (as of the date such information
is given). All of the outstanding shares of capital stock of each of the
Company, Thermo Electron and their respective Significant Subsidiaries are duly
authorized and validly issued, and, to the best of such counsel's knowledge,
fully paid and non-assessable; to the best of such counsel's knowledge, the
Company and Thermo Electron own, directly or indirectly through Subsidiaries,
the amount of the outstanding capital stock of their respective Significant
Subsidiaries, as described in the Prospectus (as of the date such information is
given), and to the best of such counsel's knowledge, such ownership is free and
clear of any lien, claim or encumbrance or any other claim of any third party
(except for certain obligations of the Company, Thermo Electron or their
Subsidiaries, as the case may be, pursuant to their stock and employee benefit
plans). To the best of such counsel's knowledge, except as described in the
Prospectus, including options granted or to be granted pursuant to stock and
employee benefit plans described therein, there are no outstanding warrants or
options to purchase any shares of the capital stock of the Company from the
Company and there are no outstanding warrants or options to purchase any shares
of capital stock of Thermo Electron from Thermo Electron to persons other than
Subsidiaries of Thermo Electron. There are no preemptive or other rights to
subscribe for or to purchase, nor any restriction upon the voting or transfer
of, any shares of the Common Stock, including any Common Stock issuable upon
conversion of any Offered Securities, in each case pursuant to the Company's
corporate charter or by-laws or any agreement or other instrument to which the
Company is a party known to such counsel;

               (iii) To the best of such counsel's knowledge, there are no
contracts or other documents which are required to be described in the
Prospectus or filed as exhibits to the Registration Statement by the Securities
Act or by the Rules and Regulations which have not been described in the
Prospectus or filed as exhibits to the Registration Statement or incorporated
therein by reference under the Rules and Regulations;

               (iv)  The documents incorporated by reference in the Prospectus
(other than the financial statements and related schedules therein, as to which
such counsel need express no opinion), when they were filed with the Commission
complied as to form in all material respects with the requirements of the
Exchange Act and the rules and regulations of the Commission thereunder;

               (v)   Except as described in Section 1(o) hereof, to the best of
such counsel's knowledge and except as described in the Prospectus, there are no
agreements or understandings between the Company and any person granting such
person the right to require the Company to file a registration statement under
the Securities Act with respect to any securities of the Company owned or to be
owned by such person or to require the Company to include such securities in the
securities registered pursuant to the Registration Statement or in 
<PAGE>
 
                                      -18-



any securities being registered pursuant to any other registration statement
filed by the Company under the Securities Act;

               (vi) To the best of such counsel's knowledge, and other than as
set forth in the Registration Statement or the Prospectus, there are no legal or
governmental proceedings pending or threatened by or against the Company or
Thermo Electron or any of their respective Subsidiaries or of which any material
property or assets of the Company or Thermo Electron or any of their respective
Subsidiaries is the subject which are required to be disclosed in the
Registration Statement or the Prospectus;

              (vii) If the Offered Securities are Debt Securities:  The Debt
Securities have been duly and validly authorized by the Company and, when duly
executed, issued and delivered by the Company, and authenticated by the Trustee
pursuant to the provisions of each Indenture, against payment therefor as
provided in this Agreement, will constitute valid and legally binding
obligations of the Company entitled to the benefits of such Indenture and
enforceable against the Company in accordance with their terms, except as the
enforceability thereof may be limited by applicable bankruptcy laws and by
general equitable principles (regardless of whether the issue of enforceability
is considered in a proceeding in equity or at law), and the Debt Securities
conform as to legal matters in all material respects to the description thereof
contained in the Prospectus. The Guarantees have been duly and validly
authorized by Thermo Electron and, when duly executed, issued and delivered by
Thermo Electron, against payment for the Debt Securities as provided in this
Agreement, will constitute valid and legally binding obligations of Thermo
Electron entitled to the benefits of the Indenture and enforceable against
Thermo Electron in accordance with their terms, subject to the effects of
applicable bankruptcy laws and to general equitable principles (whether
considered in a proceeding in equity or at law); and the Guarantees conform as
to legal matters in all material respects to the description thereof contained
in the Prospectus.

               (viii) If the Offered Securities are Debt Securities:  Each
Indenture has been duly authorized, executed and delivered by the Company and
Thermo Electron, and (assuming due execution and delivery by the Trustee)
constitutes a valid and legally binding obligation of the Company and Thermo
Electron enforceable against the Company and Thermo Electron in accordance with
its terms, except as the enforceability thereof may be limited by applicable
bankruptcy laws and by general equitable principles (regardless of whether the
issue of enforceability is considered in a proceeding in equity or at law); and
each Indenture conforms as to legal matters in all material respects to the
description thereof contained in the Prospectus;

               (ix)   If the Offered Securities are shares of Common Stock:  The
unissued shares of the Common Stock have been duly and validly authorized and,
when issued and delivered against payment therefor as provided in this
Agreement, such shares will be duly and validly issued, fully paid and non-
assessable; and the Common Stock conforms as to legal matters in all material
respects to the description thereof contained in the Prospectus;

               (x)    If the Offered Securities are convertible into shares of
Common Stock: The Common Stock reserved for issuance upon conversion of
convertible Debt Securities
<PAGE>
 
                                      -19-

has been validly authorized and reserved for such purpose; and, if and when any
of such convertible Debt Securities are converted into shares of Common Stock in
accordance with the conversion rights so provided, such shares of Common Stock
will be validly issued, fully paid and non-assessable and delivered in
accordance with the terms of the Company's corporate charter and by-laws;

               (xi) This Agreement has been duly authorized, executed and
delivered by the Company and Thermo Electron;

               (xii) The issue and sale of the Offered Securities being
delivered on the Closing Date by the Company and the compliance by the Company
and Thermo Electron with all of the provisions of this Agreement and each
Indenture, and the consummation of the transactions contemplated hereby and
thereby, will not conflict with or result in a breach or violation of any of the
terms or provisions of, or constitute a default under, any material indenture,
mortgage, deed of trust, loan agreement or other agreement known to such counsel
to which the Company or Thermo Electron or any of their respective Subsidiaries
is a party or by which the Company or Thermo Electron or any of such
Subsidiaries is bound or to which any of the property or assets of the Company
or Thermo Electron or any of their respective Subsidiaries is subject except for
such conflicts, breaches, violations or defaults which would not have a material
adverse effect on the consolidated financial condition, shareholders' equity,
results of operations or business of such corporation and its Subsidiaries taken
as a whole, nor will such actions result in any violation of the charter or by-
laws of the Company or Thermo Electron or any provisions of any State or Federal
statute or any order, rule or regulation known to such counsel of any court or
governmental agency or body having jurisdiction over the Company or Thermo
Electron or any of their respective Subsidiaries or any of their respective
material properties or assets (other than statutes, orders, rules and
regulations pertaining to securities laws matters, which are addressed elsewhere
in such opinion).

               (xiii) Except for the registration of the Offered Securities
under the Securities Act and such consents, approvals, authorizations,
registrations or qualifications as may be required under the Exchange Act, the
Trust Indenture Act and applicable state securities laws or by the National
Association of Securities Dealers, Inc., in connection with the purchase and
distribution of the Offered Securities by the Underwriters, no consent,
approval, authorization or order of, or filing or registration with, any such
court or governmental agency or body is required for the execution, delivery and
performance of this Agreement or the Indentures by the Company and Thermo
Electron and the consummation by the Company and Thermo Electron of the
transactions contemplated hereby and thereby.

               (xiv) The Registration Statement was declared effective under the
Securities Act and each Indenture was qualified under the Trust Indenture Act as
of the date specified in such opinion, the Prospectus was filed with the
Commission pursuant to the subparagraph of Rule 424 specified in such opinion on
the date specified therein and no stop order suspending the effectiveness of the
Registration Statement has been issued and, to the best of such counsel's
knowledge, no proceeding for that purpose is pending or threatened by the
Commission;
<PAGE>
 
                                      -20-

               (xv) The statements contained in the Prospectus under the
captions relating to the Offered Securities, insofar as they describe federal
statutes, rules and regulations, or portions thereof (other than those
pertaining to tax matters, as to which such counsel need not express any
opinion), constitute accurate descriptions thereof in all material respects; and

               (xvi) The Registration Statement, as of the Effective Date, and
the Prospectus, as of the date it was filed with the Commission and as of the
Closing Date, and any further amendments or supplements thereto made by the
Company or Thermo Electron prior to the applicable Closing Date (other than the
financial statements and related schedules therein and all other financial and
statistical data included therein or omitted therefrom and other than the Form
T-1, as to which such counsel need express no opinion) complied as to form in
all material respects with the requirements of the Securities Act and the Rules
and Regulations; and each Indenture conforms in all material respects to the
requirements of the Trust Indenture Act and the applicable rules and regulations
thereunder.

          In rendering the foregoing opinions, such counsel may state that his
opinion is limited to matters governed by the federal laws of the United States
of America, the Delaware General Corporation Law and the laws of the
Commonwealth of Massachusetts.

          In addition, such counsel shall also have furnished to the
Underwriters a written statement, addressed to the Underwriters and dated the
Closing Date, in form and substance satisfactory to the Underwriters, to the
effect that such counsel has acted as counsel to the Company in connection with
the preparation of the Registration Statement, and based on the foregoing, such
counsel does not believe that (i) the Registration Statement (other than the
financial statements and related schedules and all other financial and
statistical data included or incorporated by reference therein or omitted
therefrom, the statements under the heading, "United States Taxation for Non-
U.S. Persons," and  the Form T-1, as to which such counsel need not express any
belief), as of the Effective Date, contained any untrue statement of a material
fact or omitted to state a material fact required to be stated therein or
necessary in order to make the statements therein not misleading, or that the
Prospectus (other than the financial statements and related schedules and all
other financial and statistical data included or incorporated by reference
therein or omitted therefrom, the statements under the heading, "United States
Taxation for Non-U.S. Persons," and  the Form T-1, as to which such counsel need
not express any belief), as of its date and the applicable Closing Date,
contains any untrue statement of a material fact or omits to state a material
fact required to be stated therein or necessary in order to make the statements
therein, in light of the   circumstances under which they were made, not
misleading or (ii) any document incorporated by reference in the Prospectus
(other than the financial statements and related schedules and all other
financial and statistical data included or incorporated by reference therein or
omitted therefrom and other than the Form T-1, as to which such counsel need not
express any belief) contained an untrue statement of a material fact or omitted
to state a material fact necessary in order to make the statements therein, in
light of the circumstances under which they were made, not misleading.  The
foregoing opinion and statement may be qualified by statements to the effect
that  such counsel does not assume any responsibility for the accuracy,
completeness or fairness of the statements contained
<PAGE>
 
                                      -21-

in the Registration Statement or the Prospectus except for the statements made
in the Prospectus under the captions relating to the designated Offered
Securities and insofar as such statements relate to the Offered Securities and
concern legal matters (other than tax matters).

          (e) If the applicable Prospectus Supplement refers to an opinion of
tax counsel for the Company relating to tax matters concerning the Offered
Securities, the Company shall have furnished to the Underwriters an opinion of
such counsel, addressed to the Underwriters, dated the Closing Date, to the
effect that the opinion of such counsel referred to in the Prospectus is
confirmed.

          (f) At the Closing Date, counsel for the Underwriters shall have been
furnished with such documents and opinions as they may reasonably require for
the purpose of enabling them to pass upon the issuance and sale of the Offered
Securities as contemplated herein and in each Terms Agreement and related
proceedings, or in order to evidence the accuracy of any of the representations
or warranties, or the fulfillment of any of the conditions, herein and therein
contained; and the Underwriters shall have received from counsel for the
Underwriters, such opinion or opinions, dated the Closing Date, with respect to
the issuance and sale of the Offered Securities, the Registration Statement, the
Prospectus and other related matters as the Underwriters may reasonably require.

          (g) At the time of execution of  each Terms Agreement, the
Underwriters shall have received from each of Arthur Andersen LLP, with respect
to the Company and if the Offered Securities include Debt Securities, Thermo
Electron, and any other accounting firm which has audited financial statements
included in the Registration Statement, letters, in form and substance
satisfactory to the Underwriters, addressed to the Underwriters and dated the
date of such Terms Agreement (i) confirming that they are independent public
accountants with respect to the Company, Thermo Electron or such other
corporation, and their respective Subsidiaries, as the case may be, within the
meaning of the Securities Act and are in compliance with the applicable
requirements relating to the qualification of accountants under Rule 2-01 of
Regulation S-X of the Commission, (ii) stating as of the date thereof (or with
respect to matters involving changes or developments since the respective dates
as of which specified financial information is given in the Prospectus, as of a
date not more than five days prior to the date thereof), the conclusions and
findings of such firm with respect to the financial information and other
matters ordinarily covered by "accountants' comfort letters" to underwriters in
connection with registered public offerings in accordance with Statement of
Auditing Standards No. 72.

          (h) With respect to the letters of the accounting firms referred to in
the preceding paragraph and delivered to the Underwriters concurrently with the
execution of each Terms Agreement (the "initial letters"), the Company shall
                                        ---------------                     
have furnished to the Underwriters letters (the "bring-down letters") of such
                                                 ------------------          
accountants, addressed to the Underwriters and dated the Closing Date (i)
confirming that they are independent public accountants within the meaning of
the Securities Act and are in compliance with the applicable requirements
relating to the qualification of accountants under Rule 2-01 of Regulation S-X
of the Commission, (ii) stating, as of the date of the bring-down letter (or,
with respect to matters involving changes or developments since the respective
dates as of which specified financial information is given in
<PAGE>
 
                                      -22-

the Prospectus, as of a date not more than five business days prior to the date
of the bring-down letter), the conclusions and findings of such firm with
respect to the financial information and other matters covered by the initial
letters and (iii) confirming in all material respects the conclusions and
findings set forth in the initial letters.

          (i) At each Closing Date, there shall not have been, since the
respective dates as of which information is given in the Registration Statement,
the Base Prospectus and any Preliminary Prospectus as in effect at the time of
execution of the applicable Terms Agreement, any material adverse change in the
consolidated financial condition, stockholders' equity, results of operations or
business of the Company and its Subsidiaries taken as a whole, or of Thermo
Electron and its Subsidiaries taken as a whole, whether or not arising in the
ordinary course of business, except as set forth in or contemplated by such
documents.

          (j) The Company shall have furnished to the Representatives a
certificate of the Company, signed by the Chairman of the Board, Chief Executive
Officer, the President or a Vice President and the Treasurer, Secretary or an
Assistant Secretary of the Company, dated the Closing Date, to the effect that
the signers of such certificate have carefully examined the Registration
Statement, the Prospectus, any supplements to the Prospectus and this Agreement
and that, to the best of such person's knowledge:

               (i) the representations and warranties of the Company in this
     Agreement are true and correct on and as of the date of the certificate
     with the same effect as if made on the date of the certificate, and the
     Company has complied with all the agreements and satisfied all the
     conditions on its part to be performed or satisfied at or prior to the
     Closing Date;

               (ii) no stop order suspending the effectiveness of the
     Registration Statement has been issued and no proceedings for that purpose
     have been instituted or, to such person's knowledge, threatened; and

               (iii)  since the respective dates as of which information is
     given in the Registration Statement, the Base Prospectus and any
     Preliminary  Prospectus as in effect at the time of execution of the
     applicable Terms Agreement, there has been no material adverse change in
     the consolidated financial condition, stockholders' equity, results of
     operations or business of the Company and its Subsidiaries taken as a
     whole, whether or not arising from transactions in the ordinary course of
     business, except as set forth in or contemplated by such documents.

     (k) Thermo Electron shall have furnished to the Representatives a
certificate of the Company, signed by the Chairman of the Board, Chief Executive
Officer, the President or a Vice President and the Treasurer, Secretary or an
Assistant Secretary of Thermo Electron, dated the Closing Date, to the effect
that the signers of such certificate have carefully examined the Registration
Statement, the Prospectus, any supplements to the Prospectus and this Agreement
and that, to the best of such person's knowledge:
<PAGE>
 
                                      -23-

               (i) the representations and warranties of Thermo Electron in this
     Agreement are true and correct on and as of the date of the certificate
     with the same effect as if made on the date of the certificate, and Thermo
     Electron has complied with all the agreements and satisfied all the
     conditions on its part to be performed or satisfied at or prior to the
     Closing Date;

               (ii) no stop order suspending the effectiveness of the
     Registration Statement has been issued and no proceedings for that purpose
     have been instituted or, to such person's knowledge, threatened; and

               (iii)  since the respective dates as of which information is
     given in the Registration Statement, the Base Prospectus and any
     Preliminary  Prospectus as in effect at the time of execution of the
     applicable Terms Agreement, there has been no material adverse change in
     the consolidated financial condition, stockholders' equity, results of
     operations or business of Thermo Electron and its Subsidiaries taken as a
     whole, whether or not arising from transactions in the ordinary course of
     business, except as set forth in or contemplated by such documents.

          (l)  (i)  Neither the Company, Thermo Electron, nor any of their
respective Subsidiaries shall have sustained since the respective dates as of
which information is given in the Registration Statement, the Base Prospectus
and any Preliminary Prospectus as in effect at the time of execution of the
applicable Terms Agreement, any loss or interference with its business from
fire, explosion, flood or other calamity, whether or not covered by insurance,
or from any labor dispute or court or governmental action, order or decree,
which is material to the Company and its Subsidiaries taken as a whole, or
material to Thermo Electron and its Subsidiaries taken as a whole, as the case
may be, otherwise than as set forth in or contemplated by such documents, or

               (ii) since the date of the most recent financial statements of
the Company and Thermo Electron, as the case may be, contained in the
Registration Statement, the Base Prospectus and any Preliminary Prospectus as in
effect at the time of execution of the applicable Terms Agreement, there shall
not have been any change in the capital stock or consolidated long-term debt of
the Company or Thermo Electron, except as set forth in the letters described in
paragraphs (g) or (h) of this Section 7, or any material adverse change in the
general affairs, operations, business, prospects, key personnel, capitalization,
financial condition, shareholders' equity or results of operations of the
Company and its Subsidiaries taken as a whole, or of Thermo Electron and its
Subsidiaries taken as a whole, otherwise than as set forth in or contemplated by
the Registration Statement, the Base Prospectus and any Preliminary Prospectus
as in effect at the time of execution of the applicable Terms Agreement, the
effect of which, in any such case described in clause (i) or (ii), is, in the
judgment of the Representatives or a majority in interest of the Underwriters,
so material and adverse as to make it impracticable or inadvisable to proceed
with the public offering or the delivery of the Offered Securities being
delivered on such Closing Date on the terms and in the manner contemplated in
the Prospectus.
<PAGE>
 
                                      -24-


          (m)  Subsequent to the execution and delivery of this Agreement and
prior to the Closing Date, (i) no downgrading shall have occurred in the rating
accorded Thermo Electron's or the Company's securities by any "nationally
recognized statistical rating organization", as that term is defined by the
Commission for purposes of Rule 436(g)(2) of the Rules and Regulations and (ii)
no such organization shall have publicly announced that it has under
surveillance or review, with possible negative implications, its rating of any
of Thermo Electron's or the Company's securities.

          (n)  Subsequent to the execution and delivery of this Agreement there
shall not have occurred any of the following:

               (i) trading in securities generally on the New York Stock
Exchange, the American Stock Exchange, the NASDAQ National Market or in the
over-the-counter market, or trading in any securities of the Company or Thermo
Electron on any exchange or in the over-the-counter market, shall have been
suspended or minimum prices shall have been established on any such exchange or
such market by the Commission, by such exchange or by any other regulatory body
or governmental authority having jurisdiction,

               (ii) a general banking moratorium shall have been declared by
federal or New York state authorities;

               (iii) the United States shall have become engaged in hostilities,
there shall have been an escalation in hostilities involving the United States
or there shall have been a declaration of a national emergency or war by the
United States; or

               (iv) there shall have occurred such a material adverse change in
general economic or financial conditions (or such a material adverse change in
international conditions the effect of which on the financial markets in the
United States shall be such) as to make it, in the judgment of the
Representatives or a majority in interest of the several Underwriters,
impracticable or inadvisable to proceed with the public offering or delivery of
the Offered Securities being delivered on such Closing Date on the terms and in
the manner contemplated in the Prospectus.

     All opinions, letters, evidence and certificates mentioned above or
elsewhere in this Agreement shall be deemed to be in compliance with the
provisions hereof only if they are in substance reasonably satisfactory to
counsel for the Underwriters.  The Company and Thermo Electron may rely on any
waiver of such conditions given by the Underwriters or counsel to the
Underwriters as if given by the Underwriters.

     8.   Indemnification and Contribution. (a) The Company and Thermo Electron,
          --------------------------------                                      
jointly and severally, shall indemnify and hold harmless each Underwriter, its
officers and employees and each such person, if any, who controls any
Underwriter, within the meaning of the Securities Act, from and against any and
all loss, claim, damage or liability, joint or several, or any action in respect
thereof (including, but not limited to any losses, claims, damages, liabilities
or actions relating to purchases and sales of the Offered Securities), to which
that Underwriter, officer,
<PAGE>
 
                                      -25-

employee or controlling person may become subject, under the Securities Act or
otherwise, insofar as such loss, claim, damage, liability or action arises out
of, or is based upon,

          (i)  any untrue statement or alleged untrue statement made by the
Company or Thermo Electron in Section 1 hereof ; or

          (ii) any untrue statement or alleged untrue statement of a material
fact contained in any Preliminary Prospectus, the Registration Statement or the
Prospectus or in any amendment or supplement thereto; or

          (iii)  the omission or alleged omission to state in any Preliminary
Prospectus, the Registration Statement or the Prospectus, or in any amendment or
supplement thereto, any material fact required to be stated therein or necessary
to make the statements therein (in the case of the Prospectus or any Preliminary
Prospectus, in light of the circumstances in which they were made) not
misleading; or

          (iv)  any act or failure to act or any alleged act or failure to act
by any Underwriter in connection with, or relating in any manner to, the Offered
Securities or the offering contemplated hereby, and which is included as part of
or referred to in any loss, claim, damage, liability or action arising out of or
based upon matters covered by clause (ii) or (iii) above (provided that the
Company and Thermo Electron shall not be liable under this clause (iv) to the
extent that it is determined in a final judgment by a court of competent
jurisdiction that such loss, claim, damage, liability or action resulted
directly or indirectly from any such acts or failures to act undertaken or
omitted to be taken by such Underwriter through its gross negligence or willful
misconduct or breach of this Agreement); and shall reimburse each Underwriter
and each such officer, employee or controlling person within 30 days after
receiving written demand therefor for any legal or other expenses reasonably
incurred by that Underwriter, officer, employee or controlling person in
connection with investigating or defending or preparing to defend against any
such loss, claim, damage, liability or action; provided, however, that the
Company and Thermo Electron shall not be liable in any such case to the extent
that any such loss, claim, damage, liability or action arises out of, or is
based upon, any untrue statement or alleged untrue statement or omission or
alleged omission in any Preliminary Prospectus, the Registration Statement or
the Prospectus, or in any such amendment or supplement in reliance upon and in
conformity with written information concerning such Underwriter furnished to the
Company through any Underwriter by or on behalf of any Underwriter specifically
for inclusion therein; and provided, further, that the Company and Thermo
Electron shall not be liable to any Underwriter under the indemnity agreement in
this subsection with respect to any Preliminary Prospectus to the extent that
any such loss, claim, damage, liability or any action in respect thereof of such
Underwriter results from the fact that such Underwriter sold Offered Securities
to a person as to whom it shall be established that there was not sent or given,
at or prior to the written confirmation of such sale, a copy of the Prospectus
or of the Prospectus as then amended or supplemented in any case where such
delivery is required by the Securities Act if the Company has previously
furnished copies thereof in sufficient quantity to such Underwriter and the
loss, claim, damage or liability of such

<PAGE>
 
                                      -26-

Underwriter results from an untrue statement or omission of a material fact
contained in the Preliminary Prospectus which was (i) identified to such
Underwriter at or prior to the earlier of the filing with the Commission or the
furnishing to such Underwriter of the Prospectus and (ii) corrected in the
Prospectus or in the Prospectus as then amended or supplemented. The foregoing
indemnity agreement is in addition to any liability which the Company or Thermo
Electron may otherwise have to any Underwriter or to any officer, employee or
controlling person of that Underwriter.

     (b) Each Underwriter, severally and not jointly, shall indemnify and hold
harmless the Company and Thermo Electron and their respective officers and
employees, each of their respective directors, and each person, if any, who
controls the Company or Thermo Electron within the meaning of the Securities
Act, from and against any loss, claim, damage or liability, joint or several, or
any action in respect thereof (including, but not limited to, any losses,
claims, damages, liabilities or actions relating to the purchases and sales of
Offered Securities), to which the Company or Thermo Electron or any such
director, officer or controlling person may become subject, under the Securities
Act or otherwise, insofar as such loss, claim, damage, liability or action
arises out of, or is based upon,

          (i) any untrue statement or alleged untrue statement of a material
fact contained in any Preliminary Prospectus, the Registration Statement or the
Prospectus or in any amendment or supplement thereto or

          (ii) the omission or alleged omission to state in any Preliminary
Prospectus, the Registration Statement or the Prospectus, or in any amendment or
supplement thereto, any material fact required to be stated therein or necessary
to make the statements therein not misleading, but in each case only to the
extent that the untrue statement or alleged untrue statement or omission or
alleged omission was made in reliance upon and in conformity with written
information concerning such Underwriter furnished to the Company through the
Underwriters by or on behalf of that Underwriter specifically for inclusion
therein, and shall reimburse, within 30 days after receiving written demand
therefor, the Company, Thermo Electron and any such director, officer or
controlling person for any legal or other expenses reasonably incurred by the
Company, Thermo Electron or any such director, officer or controlling person in
connection with investigating or defending or preparing to defend against any
such loss, claim, damage, liability or action.  The foregoing indemnity
agreement is in addition to any liability which any Underwriter may otherwise
have to the Company or Thermo Electron or any such director, officer, employee
or controlling person.

     (c) Promptly after receipt by an indemnified party under this Section 8 of
notice of any claim or the commencement of any action, the indemnified party
shall, if a claim in respect thereof is to be made against the indemnifying
party under this Section 8, notify the indemnifying party in writing of the
claim or the commencement of that action; provided, however, that the failure to
notify the indemnifying party shall not relieve it from any liability which it
may have under this Section 8 except to the extent it has been materially
prejudiced by such failure and, provided further, that the failure to notify the
indemnifying party shall not relieve it from any liability which it may have to
an indemnified party otherwise than under
<PAGE>
 
                                      -27-

Section 8 (a) or (b). If any such claim or action shall be brought against an
indemnified party, and it shall notify the indemnifying party thereof, the
indemnifying party shall be entitled to participate therein and, to the extent
that it wishes, jointly with any other similarly notified indemnifying party, to
assume the defense thereof with counsel reasonably satisfactory to the
indemnified party. After notice from the indemnifying party to the indemnified
party of its election to assume the defense of such claim or action, the
indemnifying party shall not be liable to the indemnified party under this
Section 8 for any legal or other expenses subsequently incurred by the
indemnified party in connection with the defense thereof other than reasonable
costs of investigation; provided that the Representatives shall have the right
to employ counsel to represent you and those other Underwriters who may be
subject to liability arising out of any claim in respect of which indemnity may
be sought by the Underwriters against the Company or Thermo Electron hereunder
if, in your reasonable judgment, it is advisable for you and those Underwriters
to be represented by separate counsel, and in that event the fees and expenses
of such separate counsel shall be paid by the indemnifying party or parties, and
provided, further, in no event, shall the indemnifying party or parties be
responsible for the expenses of more than one separate counsel for all such
indemnified parties.

     No indemnifying party shall (i) without the prior written consent of the
indemnified parties (which consent shall not be unreasonably withheld), settle
or compromise or consent to the entry of any judgment with respect to any
pending or threatened claim, action, suit or proceeding in respect of which
indemnification or contribution may be sought hereunder (whether or not the
indemnified parties are actual or potential parties to such claim or action)
unless such settlement, compromise, consent or judgment (A) includes an
unconditional release of each indemnified party from all liability arising out
of such claim, action, suit or proceeding, and (B) does not include a statement
as to or an admission of fault, culpability or failure to act by or on behalf of
any indemnified party, or (ii) be liable for any settlement of any such action
effected without its written consent, but if settled with the consent of the
indemnifying party or if there be a final judgment for the plaintiff in any such
action, the indemnifying party agrees to indemnify and hold harmless any
indemnified party from and against any loss or liability by reason of such
settlement or judgment.

     (d) If the indemnification provided for in this Section 8 shall for any
reason be unavailable to or insufficient to hold harmless an indemnified party
under Section 8(a) or 8(b) in respect of any loss, claim, damage or liability,
or any action in respect thereof, referred to therein, then each indemnifying
party shall, in lieu of indemnifying such indemnified party, contribute to the
amount paid or payable by such indemnified party as a result of such loss,
claim, damage or liability, or action in respect thereof,

          (i) in such proportion as shall be appropriate to reflect the relative
benefits received  by the Company and Thermo Electron on the one hand and the
Underwriters on the other from the offering of the Offered Securities or

          (ii) if the allocation provided by clause (i) above is not permitted
by applicable law, in such proportion as is appropriate to reflect not only the
relative benefits referred to in clause (i) above but also the fault of the
Company and Thermo Electron on the one
<PAGE>
 
                                      -28-

hand and the Underwriters on the other with respect to the statements or
omissions which in such loss, claim, damage or liability, or action in respect
thereof, as well as any other relevant equitable considerations. The relative
benefits received by the Company and Thermo Electron on the one hand and the
Underwriters on the other with respect to such offering shall be deemed to be in
the same proportion as the total net proceeds from the offering of the Offered
Securities purchased under this Agreement (before deducting expenses) received
by the Company on the one hand, and the total underwriting discounts and
commissions received by the Underwriters with respect to the Offered Securities
purchased under this Agreement, on the other, bear to the total gross proceeds
from the offering of the Offered Securities under this Agreement in each case as
set forth in the table on the cover page of the Prospectus. The relative fault
shall be determined by reference to whether the untrue or alleged untrue
statement of a material fact or omission or alleged omission to state a material
fact relates to information supplied by the Company or Thermo Electron, on the
one hand, or the Underwriters on the other, the intent of the parties and their
relative knowledge, access to information and opportunity to correct or prevent
such statement or omission. The Company, Thermo Electron and the Underwriters
agree that it would not be just and equitable if contributions pursuant to this
Section were to be determined by pro rata allocation (even if the Underwriters
were treated as one entity for such purpose) or by any other method of
allocation which does not take into account the equitable considerations
referred to herein. The amount paid or payable by an indemnified party as a
result of the loss, claim, damage or liability, or action in respect thereof,
referred to above in this Section 8 shall be deemed to include, for purposes of
this Section 8(d), any legal or other expenses reasonably incurred by such
indemnified party in connection with investigating or defending any such action
or claim. Notwithstanding the provisions of this Section 8(d), no Underwriter
shall be required to contribute any amount in excess of the amount by which the
total price at which the Offered Securities underwritten by it and distributed
to the public was offered to the public exceeds the amount of any damages which
such Underwriter has otherwise paid or become liable to pay by reason of any
untrue or alleged untrue statement or omission or alleged omission. No person
guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of
the Securities Act) shall be entitled to contribution from any person who was
not guilty of such fraudulent misrepresentation. The Underwriters' obligations
to contribute as provided in this Section 8(d) are several in proportion to
their respective underwriting obligations and not joint. The provisions of this
Section 8(d) shall be applied separately to each offering of Offered Securities.

     (e) The Underwriters severally confirm that the following statements are
correct and constitute information concerning such Underwriters furnished in
writing to the Company by or on behalf of the Underwriters specifically for
inclusion in the Registration Statement and the Prospectus: (i) the legend in
the Prospectus concerning stabilization and over-allotment by the Underwriters,
(ii) the statements with respect to the public offering of the Offered
Securities by the Underwriters set forth on the cover page of the Prospectus and
(iii) the statements  concerning concessions, allowances and reallowances and
stabilization and over-allotment set forth under the caption "Underwriting" in
the Prospectus.

     9.    Defaulting Underwriters.  If on the applicable Closing Date, any
           -----------------------                                         
Underwriter defaults in the performance of its obligations under this Agreement,
the remaining non-defaulting Underwriters shall be obligated to purchase (in
addition to the amount of Offered Securities
<PAGE>
 
                                      -29-

which such Underwriters are obligated to purchase pursuant to Section 2) the
Offered Securities which the defaulting Underwriter agreed but failed to
purchase on such Closing Date in the respective proportions to the amount of
Offered Securities set opposite the names of each remaining non-defaulting
Underwriter in Exhibit A to the applicable Terms Agreement bears to the amount
               ---------       
of the Offered Securities set opposite the names of all the remaining non-
defaulting Underwriters in Exhibit A to the applicable Terms Agreement;
                           ---------       
provided, however, that the remaining non-defaulting Underwriters shall not be
obligated to purchase any of the Offered Securities on such Closing Date if the
total number of Offered Securities which the defaulting Underwriter or
Underwriters agreed but failed to purchase on such date exceeds 10% of the total
amount of the Offered Securities to be purchased on such Closing Date. If the
foregoing maximum percentage is exceeded, the remaining non-defaulting
Underwriters, or those other underwriters satisfactory to the Underwriters who
so agree, shall have the right, but shall not be obligated, to purchase, in such
proportion as may be agreed upon among them, all the Offered Securities to be
purchased on such Closing Date. If the non-defaulting Underwriters or the other
underwriters satisfactory to the Underwriters do not elect to purchase the
Offered Securities which the defaulting Underwriter or Underwriters agreed but
failed to purchase, this Agreement shall. terminate without liability on the
part of any non-defaulting Underwriter or the Company or Thermo Electron, except
that the Company, Thermo Electron and the Underwriters will continue to be
liable for the payment of expenses to the extent set forth in Sections 6 and 11
and continue to be liable under Section 8. As used in this Agreement, the term
"Underwriter" includes, for all purposes of this Agreement unless the context
 -----------           
requires otherwise, any party not listed in Exhibit A to any applicable Terms
                                            ---------
Agreement who, pursuant to this Section 9, purchases Offered Securities which a
defaulting Underwriter agreed but failed to purchase. Nothing contained herein
shall relieve a defaulting Underwriter of any liability it may have to the
Company for damages caused by its default. If other underwriters are obligated
or agree to purchase the Offered Securities of a defaulting or withdrawing
Underwriter, either the Underwriters or the Company may postpone the applicable
Closing Date for up to seven full business days in order to effect any changes
that in the reasonable opinion of counsel for the Company or counsel for the
Underwriters may be necessary in the Registration Statement, the Prospectus or
in any other document or arrangement necessary to consummate the transactions
described herein.

     10.  Termination.  The obligations of the Underwriters under this Agreement
          -----------                                                           
may be terminated by the Representatives or by Underwriters which have agreed to
purchase in the aggregate 50% or more of the aggregate amount of Offered
Securities by notice given to and received by the Company prior to delivery of
and payment for the Offered Securities if, prior to that time, any of the events
described in Sections 7(i), (l), (m) or (n) (but as to subsection (m) only, only
if the offering is of Debt Securities) shall have occurred or if the
Underwriters shall decline to purchase the Offered Securities for any reason
permitted under this Agreement.

     11.  Reimbursement of Underwriters' Expenses.  If the Company shall fail to
          ---------------------------------------                               
tender the Offered Securities for delivery to the Underwriters by reason of any
failure, refusal or inability on the part of the Company or Thermo Electron to
perform any agreement on its part to be performed, or because any other
condition of the Underwriters' obligations hereunder required to be fulfilled by
the Company or Thermo Electron is not fulfilled, the Company will reimburse
<PAGE>
 
                                      -30-

the Underwriters for all reasonable out-of-pocket expenses (including fees and
disbursements of counsel) incurred by the Underwriters in connection with this
Agreement and the proposed purchase of the Offered Securities, and upon demand
the Company shall pay the full amount thereof to the Underwriters. If this
Agreement is terminated pursuant to Section 9 by reason of the default of one or
more Underwriters, the Company shall not be obligated to reimburse any
defaulting Underwriter for any of its expenses incurred in connection with this
Agreement.

     12.  Notices, etc.  All statements, requests, notices and agreements
          ------------                                                   
hereunder shall be in writing, and:

          (a) if to the Underwriters, shall be delivered or sent by mail, telex
or facsimile transmission, if Lehman Brothers Inc. is one of the Underwriters,
c/o Lehman Brothers Inc., Three World Financial Center, New York, New York
10285, Attention: Syndicate Department (Fax: 212-526-6588), with a copy, in the
case of any notice pursuant to Section 8(c), to the Director of Litigation,
Office of the General Counsel, Lehman Brothers Inc., World Financial Center,
10th Floor, New York, NY 10285, if Goldman, Sachs & Co. is one of the
Underwriters, c/o Goldman, Sachs & Co., 85 Broad Street, New York, NY 10004,
Attention:  Registration Department (Fax:  212-357-0926) and if Smith Barney
Inc. is one of the Underwriters, c/o Seven World Trade Center, New York, NY
10048 (Fax:  212-783-4548; and

          (b) if to the Company or Thermo Electron, shall be delivered or sent
by mail, telex or facsimile transmission to the address of the Company or Thermo
Electron set forth in the Registration Statement, Attention: General Counsel
(Fax: (617) 622-1283).

Any such statements, requests, notices or agreements shall take effect at the
time of receipt thereof.  The Company and Thermo Electron shall be entitled to
act and rely upon any request, consent, notice or agreement given or made on
behalf of the Underwriters by the Representatives.

     13.  Persons Entitled to Benefit of Agreement.  This Agreement shall inure
          ----------------------------------------                             
to the benefit of and be binding upon the Underwriters, the Company and Thermo
Electron and their respective successors.  This Agreement  and the terms and
provisions hereof are for the sole benefit of only those persons, except that
(A) the representations, warranties, indemnities and agreements of the Company
and Thermo Electron contained in this Agreement shall also be deemed to be for
the benefit of the person or persons, if any, who control any Underwriter within
the meaning of Section 15 of the Securities Act and (B) the indemnity agreement
of the Underwriters contained in Section 8(b) of this Agreement shall be deemed
to be for the benefit of the directors of the Company and Thermo Electron,
officers of the Company and Thermo Electron and any person controlling the
Company or Thermo Electron within the meaning of Section 15 of the Securities
Act.  Nothing in this Agreement is intended or shall be construed to give any
person, other than the persons referred to in this Section 13, any legal or
equitable right, remedy or claim under or in respect of this Agreement or any
provision contained herein.

     14.  Survival.  The respective indemnities, representations, warranties and
          --------                                                              
agreements of the Company, Thermo Electron and the Underwriters contained in
this Agreement or made by
<PAGE>
 
                                      -31-

or on behalf of them, respectively, pursuant to this Agreement, shall survive
the delivery of and payment for any Offered Securities and shall remain in full
force and effect, regardless of any investigation made by or on behalf of any of
them or any person controlling any of them.

     15.  Definition of the Terms "Business Day," "Significant Subsidiary" and
          --------------------------------------------------------------------
"Subsidiary."   For purposes of this Agreement, (a) "business day" means any day
- -----------                                          ------------               
on which the New York Stock Exchange, Inc. is open for trading, (b) "Subsidiary"
                                                                     ---------- 
has the meaning set forth in Rule 405 of the Rules and Regulations and (c)
                                                                          
"Significant Subsidiary" has the meaning set forth in Item 1-02(w) of the
- -----------------------                                                  
Regulation S-X of the Rules and Regulations.

     16.  Performance by the Company.  Thermo Electron agrees to cause the
          --------------------------                                      
Company to perform each of the agreements and obligations of the Company
contained in this Agreement.

     17.  Governing Law.  This Agreement shall be governed by and construed in
          -------------                                                       
accordance with the laws of Massachusetts.

     18.  Counterparts.  This Agreement may be executed in counterparts and, if
          ------------                                                         
executed in more than one counterpart, the executed counterparts shall each be
deemed to be an original but all such counterparts shall together constitute one
and the same instrument.

     19.  Headings.  The headings herein are inserted for convenience of
          --------                                                      
reference only and are not intended to be part of, or to affect the meaning or
interpretation of, this Agreement.



                  [Remainder of page intentionally left blank]
<PAGE>
 
                                      -32-



     If the foregoing correctly sets forth the agreement between the Company,
Thermo Electron and the Underwriters, please indicate your acceptance in the
space provided for that purpose below.

                              Very truly yours,

                              Thermo Instrument Systems Inc.

                              By: /s/ Melissa F. Riordan
                                  _________________________
                                  Name:  Melissa F. Riordan
                                  Title: Treasurer
 
 
                              Thermo Electron Corporation

                              By: /s/ Melissa F. Riordan
                                  _________________________
                                  Name:  Melissa F. Riordan
                                  Title: Treasurer

Accepted:

Lehman Brothers Inc.
Goldman, Sachs & Co.
Smith Barney Inc.

By: Lehman Brothers Inc.

By: /s/ Kevin Davies
    ____________________________________
    Name:  Kevin Davies
    Title: Associate, Investment Banking
<PAGE>
 
 
                                                                      SCHEDULE I

                                TERMS AGREEMENT


                                                January __, 1998

To each of the Underwriters
named on Exhibit A hereto

Dear Sirs:

       Thermo Instrument Systems Inc., a Delaware corporation (the "Company"),
                                                                    -------   
proposes to issue and sell $___ million aggregate principal amount of its debt
securities with the terms set forth below (the "Offered Securities").  Subject
                                                ------------------            
to the terms and conditions set forth herein or incorporated by reference
herein, the underwriters named on Exhibit A hereto (the "Underwriters") offer to
                                  ---------              ------------           
purchase, severally and not jointly, the principal amount of Offered Securities
set forth therein opposite their respective names at __% of the principal amount
thereof.  

     The Offered Securities shall have the following terms:

     Title: ___% Convertible Subordinated Debentures due 200_

     Maturity:

     Interest rate: ___% per annum

     Interest payment dates:  ___ and ______, commencing ____, 199_

     Redemption provisions:  Redeemable at the option of the Company, in whole
     or in part, at any time on or after ____________ at 100% of the principal
     amount thereof, together with accrued interest to the date of redemption.

     Repayment provisions:  Subject to repayment at the option of the holder at
     100% of the principal amount thereof, together with accrued interest to the
     date of repayment, in the event the Common Stock is neither listed for
     trading on a United States national securities exchange, Nasdaq National
     Market nor approved for trading on an established automated over-the-
     counter trading market in the United States.

<PAGE>
                                                                       Exhibit A
                                      -2-

     Conversion provisions: Convertible at any time (except that Offered
     Securities issued in bearer form will not be convertible until the date 40
     days after the Closing Date) into shares of Common Stock of the Company at
     an initial conversion price of $____.

     Guarantee:  Guaranteed on a subordinated basis by Thermo Electron
     Corporation.

     Form:    To be issued in registered form and bearer form.  The Offered
     Securities issued in bearer form will be initially represented by a
     temporary global bearer Offered Security exchangeable for definitive
     Offered Securities commencing on the date 40 days after the Closing Date.

     The Closing Date shall be January __, 1998.

     All the provisions contained in the Underwriting Agreement dated January
__, 1998 among Lehman Brothers Inc., Goldman, Sachs & Co., Smith Barney Inc.,
the Company and Thermo Electron Corporation, and in the Joint Officers'
Certificate dated January __, 1998, executed by the Company and Thermo Electron,
copies of which you have previously received, are herein incorporated by
reference (except for provisions that relate to securities other than Offered
Securities designated herein) in their entirety and shall be deemed to be a part
of this Terms Agreement to the same extent as if such provisions had been set
forth in full herein.  Terms defined in the Underwriting Agreement are used
herein as therein defined.

     The Company agrees to be bound by the provisions of Section 5(i) of the
Underwriting Agreement.

     Payment for the Offered Securities shall be made to or upon the order of
the Company on the Closing Date by wire transfer in immediately available funds.


                  REMAINDER OF PAGE INTENTIONALLY LEFT BLANK

<PAGE>
 
                                      -3-

     Please accept this offer by signing a copy of this Terms Agreement in the
space set forth below.

                                                 Very truly yours,

Accepted on January __, 1998                     THERMO INSTRUMENT SYSTEMS INC.

LEHMAN BROTHERS INC.
GOLDMAN, SACHS & CO.                             By:___________________________
SMITH BARNEY INC.                                Name:
                                                   Title:

By:  LEHMAN BROTHERS INC.                        THERMO ELECTRON CORPORATION

 
By: ____________________                         By:___________________________
    Name:                                           Name:
    Title:                                          Title:

<PAGE>
 
  EXHIBIT A
  ---------

  LIST OF UNDERWRITERS
 
 
<TABLE> 
<CAPTION> 
                                                           Principal Amount
Underwriter                                                 of Debentures
- -----------                                                ----------------

<S>                                                           <C> 
Lehman Brothers Inc......................................
Goldman, Sachs & Co......................................
Smith Barney Inc.........................................
                                      Total..............
 
</TABLE>


<PAGE>
 
                                                                     EXHIBIT 1.2

                                                                     

                                TERMS AGREEMENT


                                                January 15, 1998

To each of the Underwriters
named on Exhibit A hereto

Dear Sirs:

       Thermo Instrument Systems Inc., a Delaware corporation (the "Company"),
                                                                    -------   
proposes to issue and sell $250,000,000 million aggregate principal amount of 
its debt securities with the terms set forth below (the "Offered Securities"). 
                                                         ------------------
Subject to the terms and conditions set forth herein or incorporated by 
reference herein, the underwriters named on Exhibit A hereto (the 
                                            --------- 
"Underwriters") offer to purchase, severally and not jointly, the principal 
 ------------           
amount of Offered Securities set forth therein opposite their respective names
at 97.75% of the principal amount thereof.


     The Offered Securities shall have the following terms:

     Title: 4% Convertible Subordinated Debentures due 2005

     Maturity: January 15, 2005

     Interest rate: 4% per annum

     Interest payment dates:  January 15 and July 15, commencing July 15, 1998

     Redemption provisions:  Redeemable at the option of the Company, in whole
     or in part, at any time on or after January 15, 2001 at 100% of the
     principal amount thereof, together with accrued interest to the date of
     redemption.

     Repayment provisions:  Subject to repayment at the option of the holder at
     100% of the principal amount thereof, together with accrued interest to the
     date of repayment, in the event the Common Stock is neither listed for
     trading on a United States national securities exchange, Nasdaq National
     Market nor approved for trading on an established automated over-the-
     counter trading market in the United States.

<PAGE>
 
                                      -2-

     Conversion provisions: Convertible at any time (except that Offered
     Securities issued in bearer form will not be convertible until the date 40
     days after the Closing Date) into shares of Common Stock of the Company at
     an initial conversion price of $35.65.

     Guarantee:  Guaranteed on a subordinated basis by Thermo Electron
     Corporation.

     Form:    To be issued in registered form and bearer form.  The Offered
     Securities issued in bearer form will be initially represented by a
     temporary global bearer Offered Security exchangeable for definitive
     Offered Securities commencing on the date 40 days after the Closing Date. 

     The Closing Date shall be January 21, 1998.

     All the provisions contained in the Underwriting Agreement dated January
15, 1998 among Lehman Brothers Inc., Goldman, Sachs & Co., Smith Barney Inc.,
the Company and Thermo Electron Corporation, and in the Joint Officers'
Certificate dated January 15, 1998, executed by the Company and Thermo Electron,
copies of which you have previously received, are herein incorporated by
reference (except for provisions that relate to securities other than Offered
Securities designated herein) in their entirety and shall be deemed to be a part
of this Terms Agreement to the same extent as if such provisions had been set
forth in full herein.  Terms defined in the Underwriting Agreement are used
herein as therein defined.

     The Company agrees to be bound by the provisions of Section 5(i) of the
Underwriting Agreement.

     Payment for the Offered Securities shall be made to or upon the order of
the Company on the Closing Date by wire transfer in immediately available funds.


                  REMAINDER OF PAGE INTENTIONALLY LEFT BLANK

<PAGE>
 
                                      -3-

     Please accept this offer by signing a copy of this Terms Agreement in the
space set forth below.

                                                 Very truly yours,

Accepted on January 15, 1998                     THERMO INSTRUMENT SYSTEMS INC.

LEHMAN BROTHERS INC.
GOLDMAN, SACHS & CO.                             By:/s/ Melissa F. Riordan 
SMITH BARNEY INC.                                ___________________________ 
                                                 Name:  Melissa F. Riordan 
                                                 Title: Treasurer 
By:  LEHMAN BROTHERS INC.                        THERMO ELECTRON CORPORATION

 
By:/s/ Kevin Davies 
   _____________________________________           By:/s/ Melissa F. Riordan 
    Name:  Kevin Davies                            ___________________________ 
    Title: Associate, Investment Banking           Name:  Melissa F. Riordan  
                                                   Title: Treasurer  
<PAGE>
 
  EXHIBIT A
  ---------

  LIST OF UNDERWRITERS
 
 
<TABLE> 
<CAPTION> 
                                                           Principal Amount
Underwriter                                                 of Debentures
- -----------                                                ----------------

<S>                                                        <C> 
Lehman Brothers Inc......................................    $ 83,400,000
Goldman, Sachs & Co......................................      83,300,000 
Smith Barney Inc.........................................      83,300,000
                                                              -----------
                                      Total..............    $250,000,000
 
</TABLE>


<PAGE>
 
                                                                     EXHIBIT 4.1

================================================================================


                        THERMO INSTRUMENT SYSTEMS INC.,
                                    ISSUER

                                        
                                      and
                                        

                         THERMO ELECTRON CORPORATION,
                                   GUARANTOR

                                      TO


                            BANKERS TRUST COMPANY,
                                    TRUSTEE

                                        

                                        



                                   INDENTURE
                                        

                         DATED AS OF JANUARY 15, 1998



                         SUBORDINATED DEBT SECURITIES


================================================================================
<PAGE>
 
                        Reconciliation and Tie between
     Trust Indenture Act of 1939 (the "Trust Indenture Act") and Indenture

<TABLE> 
<CAPTION> 
     Trust Indenture Act Section                          Indenture Section
     ---------------------------                          -----------------
     <S>                                                  <C> 
     Section 310(a)(1)........................................  607
      (a)(2)..................................................  607
      (b).....................................................  608
     Section 311..............................................  611
     Section 312(a)...........................................  701
      (b).....................................................  702
      (c).....................................................  702
     Section 313(a)...........................................  703
      (b)(2)..................................................  703
      (c).....................................................  703
      (d).....................................................  703
     Section 314(a)...........................................  704
      (c)(1)..................................................  102
      (c)(2)..................................................  102
      (e).....................................................  102
      (f).....................................................  102
     Section 315(a)...........................................  601
      (b).....................................................  602
      (c).................................................601,  602
      (d).....................................................  601
      (e).....................................................  515
     Section 316(a)...........................................  101
      (a)(1)(A)...........................................502,  512
      (a)(1)(B)...............................................  513
      (b).....................................................  508
      (c).....................................................  104
     Section 317(a)(1)........................................  503
      (a)(2)..................................................  504
      (b)..................................................... 1003
     Section 318(a)...........................................  108
      (c).....................................................  108 
</TABLE>

Note:  This reconciliation and tie shall not, for any purpose, be deemed to be
part of the Indenture.

Attention should also be directed to Section 318(c) of the Trust Indenture Act,
which provides that the provisions of Sections 310 to and including 317 are a
part of and govern every qualified indenture, whether or not physically
contained herein.
<PAGE>
 
                               TABLE OF CONTENTS

<TABLE> 
<S>                                                                     <C>  
ARTICLE ONE:  DEFINITIONS AND OTHER PROVISIONS OF GENERAL 
               APPLICATION...........................................    2

  Section 101.  Definitions..........................................    2
  Section 102.  Compliance Certificates and Opinions.................   14
  Section 103.  Form of Documents Delivered to Trustee...............   15
  Section 104.  Acts of Holders......................................   16
  Section 105.  Notices, Etc. to Trustee, Company and Guarantor......   18
  Section 106.  Notice to Holders of Securities; Waiver..............   18
  Section 107.  Language of Notices..................................   19
  Section 108.  Conflict with Trust Indenture Act....................   19
  Section 109.  Effect of Headings and Table of Contents.............   20
  Section 110.  Successors and Assigns...............................   20
  Section 111.  Separability Clause..................................   20
  Section 112.  Benefits of Indenture................................   20
  Section 113.  Governing Law........................................   20
  Section 114.  Legal Holidays.......................................   20
  Section 115.  Taxes................................................   21

ARTICLE TWO:  SECURITIES AND GUARANTEE FORMS.........................   22

  Section 201.  Forms Generally......................................   22
  Section 202.  Guarantee by Guarantor; Form of Guarantee............   22
  Section 203.  Form of Trustee's Certificate of Authentication......   23
  Section 204.  Securities in Global Form............................   23
  Section 205.  Form of Conversion Notice............................   24

ARTICLE THREE:  THE SECURITIES.......................................   24

  Section 301.  Amount Unlimited; Issuable in Series.................   24
  Section 302.  Currency; Denominations..............................   28
  Section 303.  Execution, Authentication, Delivery and Dating.......   28
  Section 304.  Temporary Securities.................................   30
  Section 305.  Registration, Transfer and Exchange..................   33
  Section 306.  Mutilated, Destroyed, Lost and Stolen Securities.....   37
  Section 307.  Payment of Interest and Certain Additional Amounts;
                  Rights to Interest and Certain Additional Amounts 
                  Preserved..........................................   38
  Section 308.  Persons Deemed Owners................................   41
  Section 309.  Cancellation.........................................   41
  Section 310.  Computation of Interest..............................   42
  Section 311.  CUSIP Numbers........................................   42
  Section 312.  Notification of Withholding..........................   42

ARTICLE FOUR:  SATISFACTION AND DISCHARGE OF INDENTURE...............   42

  Section 401.  Satisfaction and Discharge...........................   42
  Section 402.  Defeasance and Covenant Defeasance...................   44
</TABLE> 
<PAGE>

<TABLE> 
<S>                                                                     <C>  
  Section 403.  Application of Trust Money...........................   48

ARTICLE FIVE:  REMEDIES..............................................   48

  Section 501.  Events of Default....................................   48
  Section 502.  Acceleration of Maturity; Rescission and Annulment...   50
  Section 503.  Collection of Indebtedness and Suits for 
                  Enforcement by Trustee.............................   52
  Section 504.  Trustee May File Proofs of Claim.....................   52
  Section 505.  Trustee May Enforce Claims Without Possession of 
                  Securities or Coupons..............................   53
  Section 506.  Application of Money Collected.......................   54
  Section 507.  Limitations on Suits.................................   54
  Section 508.  Unconditional Right of Holders to Receive Principal 
                  and Any Premium, Interest and Additional Amounts...   55
  Section 509.  Restoration of Rights and Remedies...................   55
  Section 510.  Rights and Remedies Cumulative.......................   55
  Section 511.  Delay or Omission not Waiver.........................   56
  Section 512.  Control by Holders of Securities.....................   56
  Section 513.  Waiver of Past Defaults..............................   56
  Section 514.  Waiver of Usury, Stay or Extension Laws..............   57
  Section 515.  Undertaking for Costs................................   57

ARTICLE SIX: THE TRUSTEE.............................................   58

  Section 601.  Certain Rights of Trustee; Certain Duties and 
                  Responsibilities...................................   58
  Section 602.  Notice of Defaults...................................   59
  Section 603.  Not Responsible for Recitals or Issuance of 
                  Securities.........................................   60
  Section 604.  May Hold Securities; Act as Trustee Under Other 
                  Indenture..........................................   60
  Section 605.  Money Held in Trust..................................   60
  Section 606.  Compensation and Reimbursement.......................   61
  Section 607.  Corporate Trustee Required; Eligibility..............   61
  Section 608.  Resignation and Removal; Appointment of Successor....   62
  Section 609.  Acceptance of Appointment by Successor...............   63
  Section 610.  Merger, Conversion, Consolidation or Succession to 
                  Business...........................................   65
  Section 611.  Preferential Collection of Claims Against Company....   65
  Section 612.  Appointment of Authenticating Agent..................   65
  Section 613.  Conflicting Interests................................   67
  Section 614.  Protection of Agents.................................   67

ARTICLE SEVEN: HOLDERS LISTS AND REPORTS BY TRUSTEE, COMPANY AND 
                GUARANTOR............................................   68

  Section 701.  Company and Guarantor to Furnish Trustee Names and 
                  Addresses of Holders...............................   68
  Section 702.  Preservation of Information; Communications to 
                  Holders............................................   68
  Section 703.  Reports by Trustee...................................   69
  Section 704.  Reports by Company and Guarantor.....................   69

ARTICLE EIGHT: CONSOLIDATION, MERGER, CONVEYANCE OR TRANSFER.........   70
</TABLE> 

                                      ii
<PAGE>

<TABLE> 
<S>                                                                     <C>  
  Section 801.  Company or Guarantor May Consolidate, Etc., Only 
                   on Certain Terms..................................   70
  Section 802.  Successor Corporation Substituted....................   71

ARTICLE NINE:  SUPPLEMENTAL INDENTURES...............................   71

  Section 901.  Supplemental Indentures Without Consent of Holders...   71
  Section 902.  Supplemental Indentures With Consent of Holders......   73
  Section 903.  Execution of Supplemental Indentures.................   74
  Section 904.  Effect of Supplemental Indentures....................   74
  Section 905.  Reference in Securities to Supplemental Indentures...   75
  Section 906.  Conformity with Trust Indenture Act..................   75

ARTICLE TEN: COVENANTS...............................................   75

  Section 1001.  Payment of Principal, Any Premium, Interest and 
                   Additional Amounts................................   75
  Section 1002.  Maintenance of Office or Agency.....................   75
  Section 1003.  Money for Securities Payments to be Held in Trust...   77
  Section 1004.  Additional Amounts..................................   79
  Section 1005.  Statement as to Compliance..........................   82
  Section 1006.  Corporate Existence.................................   82

ARTICLE ELEVEN:  REDEMPTION OF SECURITIES............................   82

  Section 1101.  Applicability of Article............................   82
  Section 1102.  Election to Redeem; Notice to Trustee...............   82
  Section 1103.  Selection by Trustee of Securities to be Redeemed...   84
  Section 1104.  Notice of Redemption................................   85
  Section 1105.  Deposit of Redemption Price.........................   86
  Section 1106.  Securities Payable on Redemption Date...............   87
  Section 1107.  Securities Redeemed in Part.........................   88

ARTICLE TWELVE:  CONVERSION OF SECURITIES............................   88

  Section 1201.  Conversion Privilege and Conversion Price...........   88
  Section 1202.  Exercise of Conversion Privilege....................   89
  Section 1203.  Fractions of Shares.................................   90
  Section 1204.  Adjustment of Conversion Price......................   90
  Section 1205.  Notice of Adjustments of Conversion Price...........   93
  Section 1206.  Notice of Certain Corporate Action..................   93
  Section 1207.  Company to Reserve Common Stock.....................   94
  Section 1208.  Taxes on Conversions................................   94
  Section 1209.  Covenant as to Common Stock.........................   94
  Section 1210.  Cancellation of Converted Securities................   95
  Section 1211.  Provision in Case of Consolidation, Merger or Sale 
                   of Assets.........................................   95
  Section 1212.  Compliance with Governmental Requirements...........   95

ARTICLE THIRTEEN:  SINKING FUNDS.....................................   96

  Section 1301.  Applicability of Article............................   96
  Section 1302.  Satisfaction of Sinking Fund Payments With 
                   Securities........................................   96
</TABLE> 

                                      iii
<PAGE>

<TABLE> 
<S>                                                                    <C>  
  Section 1303.  Redemption of Securities for Sinking Fund...........   97

ARTICLE FOURTEEN:  GUARANTEES........................................   97

  Section 1401.  Guarantees..........................................   97
  Section 1402.  Execution and Delivery of Guarantees................   98
  Section 1403.  Guarantees Optional.................................   99

ARTICLE FIFTEEN:  REPAYMENT AT THE OPTION OF HOLDERS.................  100

  Section 1501.  Applicability Of Article............................  100
  Section 1502.  Repayment Of Securities.............................  100
  Section 1503.  Notice of Repayment.................................  100
  Section 1504.  Exercise Of Option..................................  101
  Section 1505.  When Securities Presented For Repayment Become Due 
                   And Payable.......................................  102
  Section 1506. Securities Repaid In Part............................  103

ARTICLE SIXTEEN:  MEETINGS OF HOLDERS OF SECURITIES..................  103

  Section 1601.  Purposes for Which Meetings May Be Called...........  103
  Section 1602.  Call, Notice and Place of Meetings..................  103
  Section 1603.  Persons Entitled to Vote at Meetings................  104
  Section 1604.  Quorum; Action......................................  104
  Section 1605.  Determination of Voting Rights; Conduct and 
                   Adjournment of Meetings...........................  105
  Section 1606.  Counting Votes and Recording Action of Meetings.....  106

ARTICLE SEVENTEEN:  SUBORDINATION OF SECURITIES......................  106

  Section 1701.  Securities Subordinate to Senior Indebtedness.......  106
  Section 1702.  Payment Over of Proceeds Upon Dissolution, Etc......  107
  Section 1703.  No Payment When Senior Indebtedness in Default......  108
  Section 1704.  Payment Permitted If No Default.....................  109
  Section 1705.  Subrogation to Rights of Holders of Senior 
                   Indebtedness......................................  109
  Section 1706.  Provisions Solely to Define Relative Rights.........  109
  Section 1707.  Trustee to Effectuate Subordination.................  110
  Section 1708.  No Waiver of Subordination Provisions...............  110
  Section 1709.  Notice to Trustee...................................  110
  Section 1710.  Reliance on Judicial Order or Certificate of 
                   Liquidating Agent.................................  111
  Section 1711.  Trustee Not Fiduciary for Holders of Senior 
                   Indebtedness......................................  111
  Section 1712.  Rights of Trustee as Holder of Senior Indebtedness; 
                   Preservation of Trustee's Rights..................  112
  Section 1713.  Article Applicable to Paying Agents.................  112

ARTICLE EIGHTEEN:  SUBORDINATION OF GUARANTEES.......................  112

  Section 1801.  Guarantees Subordinate to Senior Guarantor 
                   Indebtedness......................................  112
  Section 1802.  Payment Over of Proceeds Upon Dissolution, Etc......  112
  Section 1803.  No Payment When Senior Guarantor Indebtedness in 
                   Default...........................................  114
  Section 1804.  Payment Permitted If No Default.....................  114
</TABLE> 

                                      iv
<PAGE>

<TABLE> 
  <S>                                                                  <C> 
  Section 1805.  Subrogation to Rights of Holders of Senior Guarantor 
                   Indebtedness......................................  115
  Section 1806.  Provisions Solely to Define Relative Rights.........  115
  Section 1807.  Trustee to Effectuate Subordination.................  115
  Section 1808.  No Waiver of Subordination Provisions...............  116
  Section 1809.  Notice to Trustee...................................  116
  Section 1810.  Reliance on Judicial Order or Certificate of 
                   Liquidating Agent.................................  117
  Section 1811.  Trustee Not Fiduciary for Holders of Senior 
                   Guarantor Indebtedness............................  117
  Section 1812.  Rights of Trustee as Holder of Senior Guarantor 
                   Indebtedness; Preservation of Trustee's Rights....  118
  Section 1813.  Article Applicable to Paying Agents.................  118
</TABLE> 

EXHIBITS

EXHIBIT A   Form of Guarantee
EXHIBIT B   Form of Trustee's Certificate of Authentication
EXHIBIT C   Conversion Notice
EXHIBIT D   Form of Certificate of Beneficial Ownership for Bearer Securities to
            be Provided to the Euroclear Operator or to Cedel Bank, societe
            anonyme
EXHIBIT E   Form of Certificate to be Given by the Euroclear Operator and Cedel
            Bank, societe anonyme
EXHIBIT F   Option to Elect Repayment upon a Repayment Event

                                       V

     
<PAGE>
 
     INDENTURE, dated as of January 15, 1998 (the "Indenture"), among Thermo
                                                   ---------                
Instrument Systems Inc., a corporation duly organized and existing under the
laws of the State of Delaware (hereinafter called the "Company"), having its
                                                       -------              
principal executive office located at 860 West Airport Freeway, Suite 301,
Hurst, Texas 76054; Thermo Electron Corporation, a corporation duly organized
and existing under the laws of the State of Delaware (hereinafter called the
"Guarantor"), having its principal executive office located at 81 Wyman Street,
 ---------                                                                     
Waltham, Massachusetts 02254-9046; and Bankers Trust Company, a banking
corporation duly organized and existing under the laws of the State of New York
(hereinafter called the "Trustee"), having its principal Corporate Trust Office
                         -------                                               
located at Four Albany Street, 4th Floor, New York, New York 10006.


                                   RECITALS:

     The Company has duly authorized the execution and delivery of this
Indenture to provide for the issuance from time to time of its unsecured
subordinated debentures, notes or other evidences of indebtedness (hereinafter
called the "Securities"), unlimited as to principal amount, to bear such rates
            ----------                                                        
of interest, to mature at such time or times, to be issued in one or more series
and to have such other provisions as shall be fixed as provided in this
Indenture.

     The Guarantor has duly authorized the execution and delivery of this
Indenture to provide for the Guarantees (as herein defined) by it with respect
to the Securities as set forth in this Indenture.

     The Guarantor desires to make the Guarantees provided for herein, and has
determined that such Guarantees are necessary and convenient to the conduct of
the business of the Company, which is a subsidiary of the Guarantor.

     All things necessary to make the Securities and any Coupons (as herein
defined), when executed by the Company and authenticated and delivered
hereunder, the valid obligations of the Company, and to make this Indenture a
valid agreement of the Company in accordance with its terms have been done.

     All things necessary to make the Guarantees, when executed by the Guarantor
and endorsed on the Securities authenticated and delivered hereunder, the valid
obligations of the Guarantor, and to make this Indenture a valid agreement of
the Guarantor in accordance with its terms have been done.

     This Indenture is subject to the provisions of the Trust Indenture Act of
1939, as amended, and the rules and regulations of the Securities and Exchange
Commission promulgated thereunder that are required to be part of this Indenture
and, to the extent applicable, shall be governed by such provisions.
<PAGE>
 
     NOW, THEREFORE, THIS INDENTURE WITNESSETH:

     For and in consideration of the premises and the purchase of the Securities
by the Holders (as herein defined) thereof, it is mutually covenanted and
agreed, for the equal and proportionate benefit of all Holders of the Securities
or of any series thereof and any Coupons (as herein defined), as follows:

                                  ARTICLE ONE

            DEFINITIONS AND OTHER PROVISIONS OF GENERAL APPLICATION

Section 101.  Definitions.
              -----------     

     Except as otherwise expressly provided in or pursuant to this Indenture or
unless the context otherwise requires, for all purposes of this Indenture:

          (1)  the terms defined in this Article have the meanings assigned to
     them in this Article and include the plural as well as the singular;

          (2)  all other terms used herein which are defined in the Trust
     Indenture Act, either directly or by reference therein, have the meanings
     assigned to them therein;

          (3)  all accounting terms not otherwise defined herein have the
     meanings assigned to them in accordance with generally accepted accounting
     principles in the United States of America and, except as otherwise herein
     expressly provided, the terms "generally accepted accounting principles" or
                                    ----------------------------------------    
     "GAAP" with respect to any computation required or permitted hereunder
      ----                                                                 
     shall mean such accounting principles as are generally accepted in the
     United States of America, consistently applied, at the date of such
     computation;

          (4)  the words "Article" and "Section" refer to an Article and
                          -------       -------                         
     Section, respectively, of this Indenture;

          (5)  the words "herein," "hereof," "hereto" and "hereunder" and other
                          ------    ------    ------       ---------           
     words of similar import refer to this Indenture as a whole and not to any
     particular Article, Section or other subdivision; and

          (6)  the word "or" is always used inclusively (for example, the phrase
                         --                                                     
     "A or B" means "A or B or both", not "either A or B but not both"); and

          (7)  the term "pursuant to this Indenture" shall include matters
     covered in an Officers' Certificate issued pursuant to Section 301 or in
     the Securities.

     Certain terms used principally in certain Articles hereof are defined in
those Articles.

     "Act," when used with respect to any Holders, has the meaning specified in
      ---                                                                      
Section 104.

                                       2
<PAGE>
 
     "Additional Amounts" has the meaning specified in Section 1004.
      ------------------                                            

     "Affiliate" of any specified Person means any other Person directly or
      ---------                                                            
indirectly controlling or controlled by or under direct or indirect common
control with such specified Person.  For the purposes of this definition,
"control," when used with respect to any specified Person, means the power to
direct the management and policies of such Person, directly or indirectly,
whether through the ownership of voting securities, by contract or otherwise;
and the terms "controlling" and "controlled" have meanings correlative to the
foregoing.

     "Authenticating Agent" means any Person authorized by the Trustee pursuant
      --------------------                                                     
to Section 612 to act on behalf of the Trustee to authenticate Securities of one
or more series.

     "Authorized Newspaper" means a newspaper, in an official language of the
      --------------------                                                   
place of publication or in the English language, customarily published on each
day that is a Business Day in the place of publication, whether or not published
on days that are Legal Holidays in the place of publication, and of general
circulation in each place in connection with which the term is used or in the
financial community of each such place. Where successive publications are
required to be made in Authorized Newspapers, the successive publications may be
made in the same or in different newspapers in the same city meeting the
foregoing requirements and in each case on any day that is a Business Day in the
place of publication.

     "Bankruptcy Law" has the meaning specified in Section 501.
      --------------                                           

     "Bearer Security" means any Security established pursuant to Section 201
      ---------------                                                        
which is payable to bearer.

     "Board of Directors," when used with reference to the Company or the
      ------------------                                                 
Guarantor, means either the board of directors or any duly authorized committee
of such board of directors of the Company or the Guarantor, as the case may be.

     "Board Resolution," when used with reference to the Company or the
      ----------------                                                 
Guarantor, means a copy of one or more resolutions, certified by the Corporate
Secretary or an Assistant Corporate Secretary of the Company or the Guarantor,
as the case may be, to have been duly adopted by its respective Board of
Directors and to be in full force and effect on the date of such certification,
and delivered to the Trustee.

     "Business Day," with respect to any Place of Payment, Place of Conversion
      ------------                                                            
or other location, means, unless otherwise specified with respect to any
Securities pursuant to Section 301, any day other than a Saturday, Sunday or
other day on which banking institutions in such Place of Payment, Place of
Conversion or other location are authorized or obligated by law, regulation or
executive order to close.

     "Cedel" has the meaning specified in Section 304(c).
      -----                                              

                                       3
<PAGE>
 
     "Closing Price Per Share" means, with respect to Common Stock for any day,
      -----------------------                                                  
the reported last sales price regular way per share or, in case no such reported
sale takes place on such day, the average of the reported closing bid and
reported closing asked prices regular way or, if more than one in either case,
the average of the average reported closing bid and average reported closing
asked prices, as reported on the principal national or regional United States
securities exchange on which such Common Stock is listed or admitted to trading
or, if such Common Stock is not listed or admitted to trading on a United States
national or regional securities exchange, as reported by the National
Association of Securities Dealers Automated Quotation System or by the National
Quotation Bureau Incorporated. In the absence of such quotations, the Closing
Price Per Share shall be reasonably determined on the basis of such quotations
or other data as the Company considers appropriate.

     "Commission" means the Securities and Exchange Commission, as from time to
      ----------                                                               
time constituted, created under the Exchange Act or, if at any time after the
execution of this Indenture such Commission is not existing and performing the
duties now assigned to it under the Trust Indenture Act, then the body
performing such duties at such time.

     "Common Depository" means the Person specified as such pursuant to Section
      -----------------                                                        
301.

     "Common Stock" means the Common Stock, par value $.10 per share, of the
      ------------                                                          
Company authorized at the date of this instrument as originally executed.
Subject to the provisions of Section 1201 and 1211, shares issuable on
conversion of Securities shall include only shares of Common Stock or shares of
any class or classes of common stock resulting from any reclassification or
reclassifications thereof; provided, however, that if at any time there shall be
                           --------  -------                                    
more than one such resulting class, the shares so issuable on conversion of
Securities shall include shares of all such classes, and the shares of each such
class then so issuable shall be substantially in the proportion that the total
number of shares of such class resulting from all such reclassifications bears
to the total number of shares of all such classes resulting from all such
reclassifications.

     "common stock" includes any stock of any class of capital stock which has
      ------------                                                            
no preference in respect of dividends or of amounts payable in the event of any
voluntary or involuntary liquidation, dissolution or winding up of the issuer
thereof and which, by its terms, is not subject to redemption by the issuer
thereof.

     "Company" means the Person named as the "Company" in the first paragraph of
      -------                                 -------                           
this Indenture until a successor Person shall have become such pursuant to the
applicable provisions of this Indenture, and thereafter "Company" shall mean
                                                         -------            
such successor Person.

     "Company Request" and "Company Order" mean, respectively, a written request
      ---------------       -------------                                       
or order, as the case may be, signed in the name of the Company by any two
Officers or by any Officer and either an Assistant Treasurer or an Assistant
Corporate Secretary, of the Company and delivered to the Trustee.

     "Conversion Agent" means any Person authorized by the Company to convert
      ----------------                                                       
Securities in accordance with Article Twelve.

                                       4
<PAGE>
 
     "Conversion Date" means the date on which any Security, which is
      ---------------                                                
convertible by the terms and provisions of such Security established pursuant to
Section 301, and the duly signed and completed conversion notice shall have been
delivered to any Place of Conversion in accordance with the provisions of
Article Twelve.

     "Conversion Price" has the meaning specified in Section 1201.
      ----------------                                            

     "Corporate Secretary" or "Assistant Corporate Secretary" means the person
      -------------------      -----------------------------                  
elected by an entity's Board of Directors to hold the title of "Secretary" or
"Clerk" or "Assistant Secretary" or "Assistant Clerk," as the case may be, as
provided for by the applicable corporate law of an entity's jurisdiction of
incorporation.

     "Corporate Trust Office" means the principal corporate trust office of the
      ----------------------                                                   
Trustee at which at any particular time its corporate trust business shall be
administered, which office at the date of original execution of this Indenture
is located at Four Albany Street, 4th Floor, New York, New York 10006.

     "Corporation" and "corporation" includes corporations, associations,
      -----------       -----------                                      
companies and business trusts.

     "Coupon" means any interest coupon appertaining to a Bearer Security.
      ------                                                              

     "Currency," with respect to any payment, deposit or other transfer in
      --------                                                            
respect of the principal of or any premium or interest on or any Additional
Amounts with respect to any Security, means Dollars, and, with respect to any
other payment, deposit or transfer pursuant to or contemplated by the terms
hereof or such Security, also means Dollars.

     "CUSIP Number" means the alphanumeric designation assigned to a Security by
      ------------                                                              
Standard & Poor's Ratings Services, CUSIP Service Bureau.

     "Custodian" has the meaning specified in Section 501.
      ---------                                           

     "Default" means any event or condition the occurrence of which would, with
      -------                                                                  
the lapse of time or the giving of notice, or both, constitute an Event of
Default.

     "Defaulted Interest" has the meaning specified in Section 307.
      ------------------                                           

     "Definitive Security" means any Security that is a Bearer Security (other
      -------------------                                                     
than a temporary global Bearer Security) or a Registered Security (other than a
temporary Registered Security).

     "Dollars" or "$" means a dollar or other equivalent unit of legal tender
      -------      -                                                         
for payment of public or private debts in the United States.

     "EUROCLEAR" has the meaning specified in Section 304(c).
      ---------                                              

                                       5
<PAGE>
 
     "Event of Default" has the meaning specified in Section 501.
      ----------------                                           

     "Exchange Act" means the Securities Exchange Act of 1934, as amended.
      ------------                                                        

     "Exchange Date" means the date specified as such pursuant to Section 301.
      -------------                                                           

     "Foreign Entity" has the meaning specified in Section 801.
      --------------                                           

     "GAAP" means such accounting principles as are generally accepted in the
      ----                                                                   
United States of America as of the date or time of any computation required
hereunder.

     "Government Obligations" means securities which are (i) direct obligations
      ----------------------                                                   
of the United States or (ii) obligations of a Person controlled or supervised by
and acting as an agency or instrumentality of the United States where the timely
payment or payments thereunder are unconditionally guaranteed as a full faith
and credit obligation by the United States, and which, in the case of (i) or
(ii), are not callable or redeemable at the option of the issuer or issuers
thereof, and shall also include a depository receipt issued by a bank or trust
company as custodian with respect to any such Government Obligation or a
specific payment of interest on or principal of or other amount with respect to
any such Government Obligation held by such custodian for the account of the
holder of a depository receipt, provided that (except as required by law) such
                                -------- ----                                 
custodian is not authorized to make any deduction from the amount payable to the
holder of such depository receipt from any amount received by the custodian in
respect of the Government Obligation or the specific payment of interest on or
principal of or other amount with respect to the Government Obligation evidenced
by such depository receipt.

     "Guarantee" means any guarantee of the Guarantor endorsed on a Security
      ---------                                                             
authenticated and delivered pursuant to this Indenture and shall include the
guarantee attached to this Indenture as Exhibit A.
                                        --------- 

     "Guarantor" means the Person named as "Guarantor" in the first paragraph of
      ---------                             ---------                           
this Indenture until a successor corporation shall have become such pursuant to
the applicable provisions of this Indenture, and thereafter "Guarantor" shall
                                                             ---------       
include such successor corporation.

     "Guarantor Request" and "Guarantor Order" mean, respectively, a written
      -----------------       ---------------                               
request or order, as the case may be, signed in the name of the Guarantor by any
two Officers or by any Officer and either an Assistant Treasurer or an Assistant
Corporate Secretary, of the Guarantor and delivered to the Trustee.

     "Holder," in the case of any Registered Security, means the Person in whose
      ------                                                                    
name such Security is registered in the Security Register and, in the case of
any Bearer Security, means the bearer thereof and, in the case of any Coupon,
means the bearer thereof.

     "Indenture" means this instrument as it may from time to time be
      ---------                                                      
supplemented or amended by one or more indentures supplemental hereto entered
into pursuant to the applicable provisions hereof and, with respect to any
Security, by the terms and provisions of such Security 

                                       6
<PAGE>
 
and any Coupon appertaining thereto established pursuant to Section 301 (as such
terms and provisions may be amended pursuant to the applicable provisions
hereof).

     "Independent Public Accountants" means accountants or a firm of accountants
      ------------------------------                                            
that, with respect to the Company, the Guarantor and any other obligor under the
Securities or the Coupons, are independent public accountants within the meaning
of the Securities Act, and the rules and regulations promulgated by the
Commission thereunder, who may be the independent public accountants regularly
retained by the Company or the Guarantor or who may be other independent public
accountants. Such accountants or firm shall be entitled to rely upon any Opinion
of Counsel as to the interpretation of any legal matters relating to this
Indenture or certificates required to be provided hereunder.

     "Indexed Security" means a Security the terms of which provide that the
      ----------------                                                      
principal amount thereof payable at Stated Maturity may be more or less than the
principal face amount thereof at original issuance.

     "Interest" or "interest," with respect to any Original Issue Discount
      --------      --------                                              
Security, which by its terms bears interest only after Maturity, means interest
payable after Maturity and, when used with respect to a Security which provides
for the payment of Additional Amounts pursuant to Section 1004, includes such
Additional Amounts.

     "Interest Payment Date," with respect to any Security, means the Stated
      ----------------------                                                
Maturity of an installment of interest on such Security.

     "Interest Record Date" means any Regular Record Date or Special Record
      --------------------                                                 
Date.

     "Internal Revenue Code"  means the United States Internal Revenue Code of
      ---------------------                                                   
1986, as amended.

     "Investment Company Act" means the Investment Company Act of 1940, as
      ----------------------                                              
amended.

     "Legal Holidays" has the meaning specified in Section 114.
      --------------                                           

     "Maturity," with respect to any Security, means the date on which the
      --------                                                            
principal of such Security or an installment of principal becomes due and
payable as provided in or pursuant to this Indenture, whether at the Stated
Maturity or by declaration of acceleration, notice of redemption or repayment,
notice of option to elect repayment or otherwise, and includes the Redemption
Date.

     "Office" or "Agency", with respect to any Securities, means an office or
      ------      ------                                                     
agency of the Company maintained or designated as a Place of Payment for such
Securities pursuant to Section 1002 or any other office or agency of the Company
maintained or designated for such Securities pursuant to Section 1002 or, to the
extent designated or required by Section 1002 in lieu of such office or agency,
the Corporate Trust Office of the Trustee.

                                       7
<PAGE>
 
     "Officer" means the Chairman of the Board, the President, any Vice
      -------                                                          
President (whether or not designated by a number or word added before or after
the title vice president), the Treasurer or the Corporate Secretary of the
Company or the Guarantor, as the case requires.

     "Officers' Certificate" of the Company or the Guarantor, as the case may
      ---------------------                                                  
be, means a certificate signed by two Officers or by any Officer and either an
Assistant Treasurer or an Assistant Corporate Secretary of the Company or the
Guarantor, as the case may be, that complies with the requirements of Section
314(e) of the Trust Indenture Act and is delivered to the Trustee.

     "Opinion of Counsel" means a written opinion of counsel, who (unless
      ------------------                                                 
otherwise provided herein) may be an employee of or counsel for the Company or
the Guarantor, as the case may be, or other counsel that, if required by the
Trust Indenture Act, complies with the requirements of Section 314(e) of the
Trust Indenture Act.

     "Original Issue Discount Security" means any Security issued pursuant to
      --------------------------------                                       
this Indenture which provides for an amount less than the principal face amount
thereof to be due and payable upon acceleration of the Maturity thereof pursuant
to Section 502.

     "Outstanding," when used with respect to any Securities, means, as of the
      -----------                                                             
date of determination, all such Securities theretofore authenticated and
delivered under this Indenture, except:

          (1)  any such Security theretofore canceled by the Trustee or the
     Security Registrar or delivered to the Trustee or the Security Registrar
     for cancellation;

          (2)  any such Security for whose payment at the Maturity thereof money
     in the necessary amount has been theretofore deposited pursuant hereto
     (other than pursuant to Section 402) with the Trustee or any Paying Agent
     (other than the Company or the Guarantor) in trust or set aside and
     segregated in trust by the Company or the Guarantor, as the case may be (if
     the Company or Guarantor shall act as its own Paying Agent), for the
     Holders of such Securities and any Coupons appertaining thereto, provided
                                                                      --------
     that, if such Securities are to be redeemed, notice of such redemption has
     ----                                                                      
     been duly given pursuant to this Indenture or provision therefor
     satisfactory to the Trustee has been made;

          (3)  any such Security with respect to which the Company has effected
     defeasance or covenant defeasance pursuant to Section 402, except to the
     extent provided in Section 402; and

          (4)  any such Security which has been paid pursuant to Section 306 or
     in exchange for or in lieu of which other Securities have been
     authenticated and delivered pursuant to this Indenture, unless there shall
     have been presented to the Trustee proof satisfactory to it that such
     Security is held by a bona fide purchaser in whose hands such Security is a
     valid obligation of the Company,

                                       8
<PAGE>
 
     provided, however, that in determining whether the Holders of the requisite
     --------  -------                                                          
     principal amount of Outstanding Securities have given any request, demand,
     authorization, direction, notice, consent or waiver hereunder or are
     present at a meeting of Holders of Securities for quorum purposes, (i) the
     principal amount of an Original Issue Discount Security that may be counted
     in making such determination and that shall be deemed to be Outstanding for
     such purposes shall be equal to the amount of the principal thereof that
     pursuant to the terms of such Original Issue Discount Security would be
     declared (or shall have been declared to be) due and payable upon a
     declaration of acceleration thereof pursuant to Section 502 at the time of
     such determination, and (ii) the principal amount of any Indexed Security
     that may be counted in making such determination and that shall be deemed
     outstanding for such purpose shall be equal to the principal face amount of
     such Indexed Security at original issuance, unless otherwise provided in or
     pursuant to this Indenture, and (iii) Securities beneficially owned by the
     Company, the Guarantor or any other obligor upon the Securities or any
     Affiliate of the Company or the Guarantor or such other obligor shall be
     disregarded and deemed not to be Outstanding, except that, in determining
     whether the Trustee shall be protected in making any such determination or
     relying upon any such request, demand, authorization, direction, notice,
     consent or waiver, only Securities which a Responsible Officer of the
     Trustee actually knows to be so owned shall be so disregarded. Securities
     so owned which shall have been pledged in good faith shall be regarded as
     Outstanding if the pledgee establishes to the satisfaction of the Trustee
     (a) the pledgee's right so to act with respect to such Securities and (b)
     that the pledgee is not the Company, the Guarantor or any other obligor
     upon the Securities or any Coupons appertaining thereto or an Affiliate of
     the Company, the Guarantor or such other obligor.

     "Paying Agent" means any Person authorized by the Company or the Guarantor
      ------------                                                             
to pay the principal of, or any premium or interest on, or any Additional
Amounts with respect to, any Security or any Coupon or take any other actions
specifically provided in this Indenture on behalf of the Company or the
Guarantor, as the case may be.

     "Person" means any individual, corporation, partnership, association, joint
      ------                                                                    
venture, joint-stock company, limited liability company, trust, estate,
unincorporated organization or government or any agency or political subdivision
thereof.

     "Place of Conversion" means any city in which any Conversion Agent is
      -------------------                                                 
located.

     "Place of Payment," with respect to any Security, means the place or places
      ----------------                                                          
where the principal of, or any premium or interest on, or any Additional Amounts
with respect to, such Security are payable as provided in or pursuant to this
Indenture or such Security.

     "Predecessor Security" of any particular Security means every previous
      --------------------                                                 
Security evidencing all or a portion of the same indebtedness as that evidenced
by such particular Security; and, for the purposes of this definition, any
Security authenticated and delivered under Section 306 in exchange for or in
lieu of a lost, destroyed, mutilated or stolen Security or any Security to which
a mutilated, destroyed, lost or stolen Coupon appertains shall be deemed to

                                       9
<PAGE>
 
evidence the same indebtedness as the lost, destroyed, mutilated or stolen
Security or the Security to which a mutilated, destroyed, lost or stolen Coupon
appertains.

     "Redemption Date," with respect to any Security or portion thereof to be
      ---------------                                                        
redeemed, means the date fixed for such redemption by or pursuant to this
Indenture or such Security.

     "Redemption Price," with respect to any Security or portion thereof to be
      ----------------                                                        
redeemed, means the price at which it is to be redeemed as determined by or
pursuant to this Indenture or such Security.

     "Registered Security" means any Security established pursuant to Section
      -------------------                                                    
201 which is registered in the Security Register.

     "Regular Record Date" for the interest payable on any Registered Security
      -------------------                                                     
on any Interest Payment Date therefor means the date, if any, specified in or
pursuant to this Indenture or such Security as the "Regular Record Date."

     "Repayment Date" has the meaning specified in Section 1502.
      --------------                                            

     "Repayment Event" has the meaning specified in Section 1502.
      ---------------                                            

     "Repayment Notice" has the meaning specified in Section 1503.
      ----------------                                            

     "Repayment Price" has the meaning specified in Section 1502.
      ---------------                                            

     "Responsible Officer," shall mean when used with respect to the Trustee,
      -------------------                                                    
any officer within the Corporate Trust Office including any Vice President,
Managing Director, Assistant Vice President, Corporate Secretary, Assistant
Corporate Secretary, Treasurer or Assistant Treasurer or any other officer of
the Trustee customarily performing functions similar to those performed by any
of the above designated officers and also, with respect to a particular matter,
any other officer to whom such matter is referred because of such officer's
knowledge and familiarity with the particular subject.

     "Security" or "Securities" means any note or notes, bond or bonds,
      --------      ----------                                         
debenture or debentures, or any other evidences of indebtedness, as the case may
be, authenticated and delivered under this Indenture; provided, however, that,
                                                      --------  -------       
if at any time there is more than one Person acting as Trustee under this
Indenture, "Securities," with respect to any such Person, shall mean Securities
            ----------                                                         
authenticated and delivered under this Indenture, exclusive, however, of
Securities of any series as to which such Person is not Trustee.

     "Securities Act" means the Securities Act of 1933, as amended.
      ---------------                                              

     "Security Register" and "Security Registrar" have the respective meanings
      -----------------       ------------------                              
specified in Section 305.

                                       10
<PAGE>
 
  "Senior Indebtedness" of the Company means the principal of, premium, if any,
   -------------------                                                         
and interest on and all other amounts due on or with respect to the following,
whether outstanding at the date of execution of this Indenture or thereafter
incurred or created:

          (i)    indebtedness of the Company for money borrowed by the Company
(excluding the Securities being issued or to be issued pursuant to this
Indenture, which will rank pari passu with the obligations represented by all
other Securities issued pursuant to this Indenture in right of payment, but
including, without limitation, purchase money obligations and money borrowed
from Guarantor or any Affiliate of Guarantor), whether or not evidenced by
debentures, bonds, notes or other corporate debt securities or similar
instruments issued by the Company (including the Company's obligations with
respect to its 3 3/4% Senior Convertible Debentures due 2000, and its 4 1/2%
Senior Convertible Debentures due 2003);

          (ii)   obligations to reimburse any bank or other person in respect of
amounts paid under letters of credit;

          (iii)  leases of real property, equipment or other assets, which
leases are capitalized in the Company's financial statements in accordance with
GAAP;

          (iv)   commitment, standby and other fees due and payable to financial
institutions with respect to credit facilities available to the Company;

          (v)    obligations of the Company under interest rate and currency
swaps, floors, caps or other similar arrangements intended to hedge interest
rates or currency exposure;

          (vi)   obligations secured by any mortgage, pledge, lien or other
encumbrance on property which is owned or held by the Company subject to such
mortgage, pledge, lien or other encumbrance, whether or not the obligations
secured thereby shall have been assumed by the Company;

          (vii)  obligations of the Company constituting guarantees of
indebtedness of or joint obligations with another or others which would be
included in the preceding clauses (i), (ii), (iii), (iv), (v) or (vi); and

          (viii) modifications, renewals, extensions or refundings of any of the
indebtedness, leases, fees or obligations referred to in the preceding clauses
(i), (ii), (iii), (iv), (v), (vi) or (vii), or debentures, notes or other
evidences of indebtedness issued in exchange therefor;

provided that Senior Indebtedness shall not include any particular indebtedness,
- -------- ----                                                                   
lease, fee, obligation, modification, renewal, extension, refunding or exchanged
securities if, under the express provisions of the instrument creating or
evidencing the same, or pursuant to which the same is outstanding, such
indebtedness, lease, fee or obligation or such modification, renewal, extension,
refunding or exchanged security is stated to be not superior in right to payment
to the Securities.

                                       11
<PAGE>
 
     "Senior Guarantor Indebtedness" means the principal of, premium, if any,
      -----------------------------
and interest on and all other amounts due on or with respect to the following,
whether outstanding at the date hereof or hereafter created or incurred:

          (i)    indebtedness of the Guarantor for money borrowed by the
Guarantor (excluding the Guarantees being issued, which will rank pari passu
with the obligations represented by all other Guarantees issued pursuant to this
Indenture in right of payment, but including, without limitation purchase money
obligations and money borrowed from any Affiliate of the Guarantor) whether or
not evidenced by debentures, bonds, notes or other corporate debt securities or
similar instruments issued by the Guarantor; provided, however, that Senior
                                             --------  -------
Guarantor Indebtedness shall not include the Guarantor's subordinated guarantee
of the obligations to redeem the common stock of Thermo Fibergen Inc.,
ThermoLyte Corporation and ThermoLase Corporation, the obligations represented
by which shall rank pari passu with the obligations represented by the
Guarantees issued pursuant to this Indenture;

          (ii)   obligations to reimburse any bank or other person in respect of
amounts paid under letters of credit;

          (iii)  leases for real property, equipment or other assets,
which leases are capitalized in the Guarantor's consolidated financial
statements in accordance with generally accepted accounting principles;

          (iv)   commitment, standby and other fees due and payable to financial
institutions with respect to credit facilities available to the Guarantor;

          (v)    obligations of the Guarantor under interest rate and currency
swaps, floors, caps or other similar arrangements intended to fix or hedge
interest rate obligations or currency exposure;

          (vi)   obligations secured by any mortgage, pledge, lien or other
encumbrance on property which is owned or held by the Guarantor subject to such
mortgage, pledge, lien or other encumbrance, whether or not the obligations
secured thereby shall have been assumed by the Guarantor;

          (vii)  obligations of the Guarantor constituting guarantees of
indebtedness of or joint obligations with another or others which would be
included in the preceding clauses (i), (ii), (iii), (iv), (v) or (vi) (including
the Guarantor's guarantee of the principal, premium, if any, and interest on the
4-1/2% Senior Convertible Debentures due 2003 and the 3-3/4% Senior Convertible
Debentures due 2000 of the Company); or

          (viii) modifications, renewals, extensions or refundings of any of the
indebtedness, leases, fees or obligations referred to in the preceding clauses
(i), (ii), (iii), (iv), (v), (vi) and (vii), or debentures, notes or other
evidences of indebtedness issued in exchange therefor;

                                       12
<PAGE>
 
provided that Senior Guarantor Indebtedness shall not include any particular
- -------- ----                                                               
indebtedness, lease, fee, obligation, modification, renewal, extension,
refunding or exchanged security if, under the express provisions of the
instrument creating or evidencing the same, or pursuant to which the same is
outstanding, such indebtedness, lease, fee or obligation or such modification,
renewal, extension, refunding or exchanged security is stated to be not superior
in right of payment to the Guarantees.

     "Senior Lender" means any holder of Senior Indebtedness or Senior Guarantor
      -------------                                                             
Indebtedness.

     "Special Record Date" for the payment of any Defaulted Interest on any
      -------------------                                                  
Registered Security means a date fixed as such by the Trustee pursuant to
Section 307.

     "Stated Maturity," with respect to any Security or any installment of
      ---------------                                                     
principal thereof or interest thereon or any Additional Amounts with respect
thereto, means the date established by or pursuant to this Indenture or such
Security or Coupon as the fixed date on which the principal of such Security or
such installment of principal or interest is, or such Additional Amounts are,
due and payable.

     "Subsidiary" means a corporation or other entity, a majority of the
      ----------                                                        
outstanding voting securities or other ownership interests having ordinary
voting power to elect a majority of the corporate directors or other Persons
performing similar functions of which is owned, directly or indirectly, by the
Company, the Guarantor or by one or more other Subsidiaries, or by the Company,
the Guarantor and one or more other Subsidiaries.

     "Tax" has the meaning specified in Section 1004.
      ---                                           

     "Tax Affected Security" means any Security held by a non-United States
      ---------------------                                                
person to whom Additional Amounts have or will become payable.

     "Tax Law Change" means any change in, or amendment to, the laws (including
      --------------                                                           
any regulations or rulings promulgated thereunder) of the United States or any
political subdivision or taxing authority thereof or therein affecting taxation,
or any change in, or amendment to, the application or official interpretation of
such laws, regulations or rulings.

     "Trading Days" means (i) if the Common Stock is quoted on any system of
      ------------                                                          
automated dissemination of quotations of securities prices (other than a
national securities exchange), days on which trades may be effected through such
system and on which at least one trade of the Common Stock has occurred, (ii) if
the Common Stock is listed or admitted for trading on any national securities
exchange, days on which such national securities exchange is open for business
and on which at least one trade of the Common Stock  has occurred or (iii) if
the Common Stock is not quoted on an automated quotation system or listed or
admitted to trading on any national securities exchange, days on which the
Common Stock is traded regular way in the over-the-counter market and for which
a closing bid and a closing asked price for the Common Stock are available.

                                       13
<PAGE>
 
     "Trust Indenture Act" means the Trust Indenture Act of 1939, as amended,
      -------------------                                                    
and any reference herein to the Trust Indenture Act or a particular provision
thereof shall mean such Act or provision, as the case may be, as amended or
replaced from time to time or as supplemented from time to time by rules or
regulations adopted by the Commission under or in furtherance of the purposes of
such Act or provision, as the case may be.

     "Trustee" means the Person named as the "Trustee" in the first paragraph of
      -------                                 -------                           
this instrument until a successor Trustee shall have become such with respect to
one or more series of Securities pursuant to the applicable provisions of this
Indenture, and thereafter "Trustee" shall mean or include each Person who is
                           -------                                          
then a Trustee hereunder; provided, however, that if at any time there is more
                          --------  -------                                   
than one such Person, "Trustee" as used with respect to the Securities of any
                       -------                                               
series shall mean the Trustee with respect to Securities of such series.

     "United States," except as otherwise provided in or pursuant to this
      -------------                                                      
Indenture or any Security, means the United States of America (including the
states thereof and the District of Columbia), its territories and possessions
and other areas subject to its jurisdiction.

     "United States person" is a person that is, for United States Federal
      --------------------                                                
income tax purposes, (a) a citizen or resident of the United States, (b) a
corporation, partnership or other entity created or organized in or under the
laws of the United States or any political subdivision thereof, (c) an estate,
the income of which is subject to United States Federal income taxation
regardless of source, (d) any trust if a court within the United States is able
to exercise primary supervision of the administration thereof and one or more
United States persons has the authority to control all substantial decisions
thereof, or (e) any other person included within the definition of United States
person under the Internal Revenue Code and the regulations thereunder.

     "U.S. Depository" or "Depository" means, with respect to any Security
      ---------------      ----------                                     
issuable or issued in the form of one or more global Registered Securities, the
Person designated as U.S. Depository or Depository by the Company in or pursuant
to this Indenture, which Person must be, to the extent required by applicable
law or regulation, a clearing agency registered under the Exchange Act, and, if
so provided with respect to any Security, any successor to such Person.  If at
any time there is more than one such Person, "U.S. Depository" or "Depository"
                                              ---------------      ---------- 
shall mean, with respect to any Securities, the qualifying entity which has been
appointed with respect to such Securities.

     "Vice President," when used with respect to the Company, the Guarantor or
      --------------                                                          
the Trustee, means any vice president, whether or not designated by a number or
a word or words added before or after the title "Vice President."
                                                 --------------  

Section 102.  Compliance Certificates and Opinions.
              ------------------------------------     

     Except as otherwise expressly provided in this Indenture, upon any
application or request by the Company or the Guarantor to the Trustee to take
any action under any provision of this Indenture, the Company or the Guarantor,
as the case may be, shall furnish to the Trustee an Officers' Certificate
stating that all conditions precedent, if any, provided for in this Indenture

                                       14
<PAGE>
 
relating to the proposed action have been complied with and an Opinion of
Counsel stating that, in the opinion of such counsel, all such conditions
precedent, if any, have been complied with, except that in the case of any such
application or request as to which the furnishing of such document is
specifically required by any provision of this Indenture relating to such
particular application or request, no additional certificate or opinion need be
furnished.

     Every certificate or opinion with respect to compliance with a condition or
covenant provided for in this Indenture shall include:

          (1)  a statement that each individual signing such certificate or
opinion has read such condition or covenant and the definitions herein relating
thereto;

          (2)  a brief statement as to the nature and scope of the examination
or investigation upon which the statements or opinions contained in such
certificate or opinion are based;

          (3)  a statement that, in the opinion of each such individual, he has
made such examination or investigation as is necessary to enable him to express
an informed opinion as to whether or not such condition or covenant has been
satisfied or complied with; and

          (4)  a statement as to whether, in the opinion of each such
individual, such condition or covenant has been satisfied or complied with.

Section 103.  Form of Documents Delivered to Trustee.
              --------------------------------------     

     In any case where several matters are required to be certified by or
covered by an opinion of any specified Person, it is not necessary that all such
matters be certified by or covered by the opinion of only one such Person, or
that they be so certified or covered by only one document, but one such Person
may certify or give an opinion with respect to some matters and one or more
other such Persons as to other matters, and any such Person may certify or give
an opinion as to such matters in one or several documents.

     Any certificate or opinion of an officer of the Company or the Guarantor
may be based, insofar as it relates to legal matters, upon an Opinion of
Counsel, unless such officer knows, or in the exercise of reasonable care should
know, that the opinion with respect to the matters upon which his certificate or
opinion is based is erroneous.  Any such Opinion of Counsel may be based,
insofar as it relates to factual matters, upon a certificate or opinion of, or
representations by, an officer or officers of the Company or the Guarantor
stating that the information with respect to such factual matters is in the
possession of the Company or the Guarantor unless such counsel knows, or in the
exercise of reasonable care should know, that the certificate or opinion or
representations with respect to such matters are erroneous.

     Where any Person is required to make, give or execute two or more
applications, requests, consents, certificates, statements, opinions or other
instruments under this Indenture or any Security, they may, but need not, be
consolidated and form one instrument.

                                       15
<PAGE>
 
Section 104.  Acts of Holders.
              ---------------     

          (1)  Any request, demand, authorization, direction, notice, consent,
     waiver or other action provided by or pursuant to this Indenture to be
     given or taken by Holders may be embodied in and evidenced by one or more
     instruments of substantially similar tenor signed by such Holders in person
     or by an agent duly appointed in writing.  If, but only if, Securities of a
     series are issuable as Bearer Securities, any request, demand,
     authorization, direction, notice, consent, waiver or other action provided
     in or pursuant to this Indenture to be given or taken by Holders of
     Securities of such series may, alternatively, be embodied in and evidenced
     by the record of Holders of Securities of such series voting in favor
     thereof, either in person or by proxies duly appointed in writing, at any
     meeting of Holders of Securities of such series duly called and held in
     accordance with the provisions of Article Sixteen, or a combination of such
     instruments and any such record.  Except as herein otherwise expressly
     provided, such action shall become effective when such instrument or
     instruments or record or both are delivered to the Trustee and, where it is
     hereby expressly required, to the Company or the Guarantor, as the case may
     be. Such instrument or instruments and any such record (and the action
     embodied therein and evidenced thereby) are herein sometimes referred to as
     the "Act" of the Holders signing such instrument or instruments or so
          ---                                                             
     voting at any such meeting.  Proof of execution of any such instrument or
     of a writing appointing any such agent, or of the holding by any Person of
     a Security, shall be sufficient for any purpose of this Indenture and
     (subject to Section 315 of the Trust Indenture Act) conclusive in favor of
     the Trustee, the Company and the Guarantor and any agent of the Trustee,
     the Company, or the Guarantor, if made in the manner provided in this
     Section. The record of any meeting of Holders of Securities shall be proved
     in the manner provided in Section 1606.

          Without limiting the generality of this Section 104, unless otherwise
     provided in or pursuant to this Indenture, a Holder, including a Depository
     that is a Holder of a global Security, may make, give or take, by a proxy,
     or proxies, duly appointed in writing, any request, demand, authorization,
     direction, notice, consent, waiver or other Act provided in or pursuant to
     this Indenture or the Securities to be made, given or taken by Holders, and
     a Depository that is a Holder of a global Security may provide its proxy or
     proxies to the beneficial owners of interests in any such global Security
     through such Depository's standing instructions and customary practices.

          (2)  The fact and date of the execution by any Person of any such
     instrument or writing may be proved in any reasonable manner which the
     Trustee deems sufficient and in accordance with such reasonable rules as
     the Trustee may determine; and the Trustee may in any instance require
     further proof with respect to any of the matters referred to in this
     Section 104.

          (3)  The ownership, principal amount and serial numbers of Registered
     Securities held by any Person, and the date of the commencement and the
     date of the termination of holding the same, shall be proved by the
     Security Register.

                                       16
<PAGE>
 
          (4)  The ownership, principal amount and serial numbers of Bearer
     Securities held by any Person, and the date of the commencement and the
     date of the termination of holding the same, may be proved by the
     production of such Bearer Securities or by a certificate executed, as
     depository, by any trust company, bank or other depository reasonably
     acceptable to the Company and the Guarantor, wherever situated, if such
     certificate shall be deemed by the Company, the Guarantor and the Trustee
     to be satisfactory, showing that at the date therein mentioned such Person
     had on deposit with such depository, or exhibited to it, the Bearer
     Securities therein described; or such facts may be proved by the
     certificate or affidavit of the Person holding such Bearer Securities, if
     such certificate or affidavit is deemed by the Company, the Guarantor and
     the Trustee to be satisfactory.  The Trustee, the Company and the Guarantor
     may assume that such ownership of any Bearer Security continues until (i)
     another certificate or affidavit bearing a later date issued in respect of
     the same Bearer Security is produced, or (ii) such Bearer Security is
     produced to the Trustee by some other Person, or (iii) such Bearer Security
     is surrendered in exchange for a Registered Security, or (iv) such Bearer
     Security is no longer Outstanding.  The ownership, principal amount and
     serial numbers of Bearer Securities held by the Person so executing such
     instrument or writing and the date of the commencement and the date of the
     termination of holding the same may also be proved in any other manner
     which the Company, the Guarantor and the Trustee deem sufficient.

          (5)  If the Company shall solicit from the Holders of any Registered
     Securities any request, demand, authorization, direction, notice, consent,
     waiver or other Act, the Company may at its option (but is not obligated
     to), by a Company Board Resolution, fix in advance a record date for the
     determination of Holders of Registered Securities entitled to give such
     request, demand, authorization, direction, notice, consent, waiver or other
     Act. Notwithstanding Trust Indenture Act Section 316(c), such record date
     shall be the record date specified in or pursuant to such Board
     Resolutions, which shall be a date not earlier than the date 30 days prior
     to the first solicitation of Holders generally in connection therewith and
     not later than the date such solicitation is completed. If such a record
     date is fixed, such request, demand, authorization, direction, notice,
     consent, waiver or other Act may be given before or after such record date,
     but only the Holders of Registered Securities of record at the close of
     business on such record date shall be deemed to be Holders for the purpose
     of determining whether Holders of the requisite proportion of Outstanding
     Securities have authorized or agreed or consented to such request, demand,
     authorization, direction, notice, consent, waiver or other Act, and for
     that purpose the Outstanding Securities shall be computed as of such record
     date; provided that no such authorization, agreement or consent by the
     Holders of Registered Securities shall be deemed effective unless it shall
     become effective pursuant to the provisions of this Indenture not later
     than six months after the record date.

          (6)  Any request, demand, authorization, direction, notice, consent,
     waiver or other Act by the Holder of any Security shall bind every future
     Holder of the same Security and any Coupon appertaining thereto and the
     Holder of every Security or Coupon issued upon the registration of transfer
     thereof or in exchange therefor or in lieu thereof in respect of anything
     done or suffered to be done by the Trustee, any Security Registrar, any
     Paying

                                       17
<PAGE>
 
     Agent, the Company or the Guarantor in reliance thereon, whether or not
     notation of such Act is made upon such Security.

          (7)  Without limiting the foregoing, a Holder entitled hereunder to
     give or take any action hereunder with regard to any particular Security
     may do so with regard to all or any part of the principal amount of such
     Security or by one or more duly appointed agents each of which may do so
     pursuant to such appointment with regard to all or any different part of
     such principal amount.

Section 105.  Notices, Etc. to Trustee, Company and Guarantor.
              -----------------------------------------------     

     Any request, demand, authorization, direction, notice, consent, waiver or
other Act of Holders or other document provided or permitted by this Indenture
to be made upon, given or furnished to, or filed with,

          (1)  the Trustee by any Holder, the Company or the Guarantor shall be
     sufficient for every purpose hereunder if made, given, furnished or filed
     in writing to or with the Trustee at its Corporate Trust Office, or

          (2)  the Company or the Guarantor by the Trustee or any Holder shall
     be sufficient for every purpose hereunder (unless otherwise herein
     expressly provided) if in writing and mailed, first-class postage prepaid,
     to the Company or the Guarantor addressed to the attention of its Treasurer
     at the address of its principal office specified in the first paragraph of
     this instrument or at any other address previously furnished in writing to
     the Trustee by the Company or the Guarantor. 

Section 106.  Notice to Holders of Securities; Waiver.
              ---------------------------------------     

     Except as otherwise expressly provided in or pursuant to this Indenture,
where this Indenture provides for notice to Holders of Securities of any event,

          (1)  such notice shall be sufficiently given to Holders of Registered
     Securities if in writing and mailed, first-class postage prepaid, to each
     Holder of a Registered Security affected by such event, at his address as
     it appears in the Security Register, not later than the latest date, and
     not earlier than the earliest date, prescribed for the giving of such
     notice; and

          (2)  such notice shall be sufficiently given to Holders of Bearer
     Securities, if any, if published in an Authorized Newspaper in The City of
     New York and, if such Securities are then listed on any stock exchange
     outside the United States, in an Authorized Newspaper in such city as the
     Company shall advise the Trustee that such stock exchange so requires, on a
     Business Day at least once, such publication to be not earlier than the
     earliest date and not later than the latest date prescribed for the giving
     of such notice; provided that any additional notice to Holders of
                     -------------                                    
     Securities of any event may be provided at any time upon the request of the
     Company and shall provided in the manner set forth above.

                                       18
<PAGE>
 
     In any case where notice to Holders of Registered Securities is given by
mail, neither the failure to mail such notice, nor any defect in any notice so
mailed, to any particular Holder of a Registered Security shall affect the
sufficiency of such notice with respect to other Holders of Registered
Securities or the sufficiency of any notice to Holders of Bearer Securities
given as provided herein.  Any notice which is mailed in the manner herein
provided shall be conclusively presumed to have been duly given or provided. In
the case by reason of the suspension of regular mail service or by reason of any
other cause it shall be impracticable to give such notice by mail, then such
notification as shall be made with the approval of the Trustee shall constitute
a sufficient notification for every purpose hereunder.

     In case by reason of the suspension of publication of any Authorized
Newspaper or Authorized Newspapers or by reason of any other cause it shall be
impracticable to publish any notice to Holders of Bearer Securities as provided
above, then such notification to Holders of Bearer Securities as shall be given
with the approval of the Trustee shall constitute sufficient notice to such
Holders for every purpose hereunder.  Neither failure to give notice by
publication to Holders of Bearer Securities as provided above, nor any defect in
any notice so published, shall affect the sufficiency of any notice mailed to
Holders of Registered Securities as provided above.

     Where this Indenture provides for notice in any manner, such notice may be
waived in writing by the Person entitled to receive such notice, either before
or after the event, and such waiver shall be the equivalent of such notice.
Waivers of notice by Holders of Securities shall be filed with the Trustee, but
such filing shall not be a condition precedent to the validity of any action
taken in reliance upon such waiver.

Section 107.  Language of Notices.
              -------------------     

     Any request, demand, authorization, direction, notice, consent, election or
waiver required or permitted under this Indenture shall be in the English
language, except that, if the Company so elects, any published notice may be in
an official language of the country of publication.

Section 108.  Conflict with Trust Indenture Act.
              ---------------------------------     

     This Indenture is subject to the provisions of the Trust Indenture Act that
are required to be part of this Indenture and shall, to the extent applicable,
be governed by such provisions.  If any provision hereof limits, qualifies or
conflicts with any duties under any required provision of the Trust Indenture
Act imposed hereon by Section 318(c) thereof, such required provision shall
control.

Section 109.  Effect of Headings and Table of Contents.
              ----------------------------------------     

     The Article and Section headings herein and the Table of Contents are for
convenience only and shall not affect the construction hereof.

                                       19
<PAGE>
 
Section 110.  Successors and Assigns.
              ----------------------     

     All covenants and agreements in this Indenture by the Company or the
Guarantor shall bind its successors and assigns, whether so expressed or not.

Section 111.  Separability Clause.
              -------------------     

     In case any provision in this Indenture, any Security or any Coupon or
Guarantee shall be invalid, illegal or unenforceable, the validity, legality and
enforceability of the remaining provisions shall not in any way be affected or
impaired thereby.

Section 112.  Benefits of Indenture.
              ---------------------     

     Nothing in this Indenture, any Security, any Coupon, or in the Guarantees
shall give to any Person, other than the parties hereto, any Security Registrar,
any Paying Agent or Conversion Agent and their successors hereunder and the
Holders of Securities, Coupons or Guarantees, any benefit or any legal or
equitable right, remedy or claim under this Indenture.

Section 113.  Governing Law.
              -------------     

     This Indenture, the Securities, any Coupons and the Guarantees shall be
governed by and construed in accordance with the laws of the Commonwealth of
Massachusetts applicable to agreements made or instruments entered into and, in
each case, performed in said state, except that the rights, protections,
obligations, indemnities and immunities of the Trustee under this Indenture
shall be governed by the laws of the State of New York, without regard to the
principles of conflicts of laws of either state.

Section 114.  Legal Holidays.
              --------------     

     Unless otherwise specified in or pursuant to this Indenture or any
Securities, in any case where any Interest Payment Date, Conversion Date,
Redemption Date, Repayment Date, Stated Maturity or Maturity of any Security
shall not be a Business Day at any Place of Payment or any Place of Conversion,
as the case may be, then (notwithstanding any other provision of this Indenture,
any Security, Coupon or Guarantee other than a provision in any Security, Coupon
or Guarantee that specifically states that such provision shall apply in lieu of
this Section) payment of interest or principal (and premium or Additional
Amounts, if any) or delivery for conversion of such Security need not be made at
such Place of Payment or Place of Conversion on such date, but such payment may
be made on the next succeeding Business Day at such Place of Payment or Place of
Conversion with the same force and effect as if made on the Interest Payment
Date, Conversion Date, Redemption Date, Repayment Date or at the Stated Maturity
or Maturity or by such last day for conversion, and no interest shall accrue on
the amount payable on such date or at such time for the period from and after
such Interest Payment Date, Redemption Date, Repayment Date, Conversion Date,
Stated Maturity or Maturity or last day for conversion, as the case may be, to
the next succeeding Business Day.

                                       20
<PAGE>
 
Section 115.  Taxes.
              -----     

     The Company will pay all stamp taxes and other similar duties, if any, that
may be imposed by the United States or the United Kingdom, or any state or
political subdivision thereof or taxing authority therein, with respect to the
execution or delivery of this Indenture, or the issuance of the Securities,
Coupons or the Guarantees, or the exchange from time to time of the temporary or
permanent Securities in global form for Registered Securities or Bearer
Securities, or with respect to the issue or delivery of shares of Common Stock
on conversion of Securities; provided, however, that the Company shall not be
                             --------  -------                               
required to pay any tax or duty which may be payable in respect of the
registration of transfer or exchange of Securities and any transfer involved in
the issue or delivery of shares of Common Stock in a name other than that of the
Holder of the Security or Securities to be converted in accordance with the
provisions of Article Twelve, and no such issue or delivery shall be made unless
and until the person requesting such issue has paid to the Company the amount of
any such tax or duty or has established to the satisfaction of the Company that
such tax or duty has been paid; and provided further, that the Company shall not
                                    -------- -------                            
be required to pay any tax or duty that may be payable in respect of any accrued
interest paid in connection with the conversion of the Securities.

                                       21
<PAGE>
 
                                  ARTICLE TWO

                        SECURITIES AND GUARANTEE FORMS

Section 201.  Forms Generally.
              ---------------     

     Each Registered Security, Bearer Security, Coupon and temporary or
permanent global Security issued pursuant to this Indenture shall be in the form
established by or pursuant to a Company Board Resolution or in one or more
indentures supplemental hereto, shall have such appropriate insertions,
omissions, substitutions and other variations as are required or permitted by or
pursuant to this Indenture or any indenture supplemental hereto, and the
Guarantees, if any, shall be in substantially the form attached to this
Indenture as Exhibit A or in such other form as shall be established pursuant to
             ---------                                                          
a Guarantor Board Resolution or in one or more indentures supplemental hereto,
in each case with such appropriate insertions, omissions, substitutions and
other variations as are required or permitted by this Indenture, and may have
such letters, numbers or other marks of identification and such legends or
endorsements placed thereon as may be required to comply with the rules of any
securities exchange or as may, consistently herewith, be determined by the
officers executing such Security, Coupon or Guarantee as evidenced by their
execution of such Security, Coupon or Guarantee.  If the form of Registered
Security, Bearer Security, Coupon, temporary or permanent global Security or
Guarantee is established by action taken pursuant to a Board Resolution of the
Company and the Guarantor, a copy of an appropriate record of such action shall
be certified by the Corporate Secretary or an Assistant Corporate Secretary of
the Company and the Guarantor, respectively, and delivered to the Trustee at or
prior to the delivery of the Company Order contemplated by Section 303 for the
authentication and delivery of such Registered Security, Bearer Security,
Coupon, temporary or permanent global Security or Guarantee.

     Definitive Securities, definitive Coupons and the Guarantees shall be
printed, lithographed or engraved on steel engraved borders or may be produced
in any other manner, all as determined by the officers of the Company executing
such Securities, Coupons or Guarantees, as evidenced by their execution of such
Securities, Coupons or Guarantees.

     Unless otherwise specified pursuant to Section 301 and except for temporary
global Bearer Securities (as contemplated by Section 304 hereof), Bearer
Securities shall have Coupons attached.

Section 202.  Guarantee by Guarantor; Form of Guarantee.
              -----------------------------------------     

     Subject to Section 1403, the Guarantor by its execution of this Indenture
hereby agrees with each Holder of a Security authenticated and delivered by the
Trustee, and with the Trustee on behalf of each such Holder, to be
unconditionally bound by the terms and provisions of the Guarantee substantially
in the form attached to this Indenture as Exhibit A and authorizes the Chairman
                                          ---------                            
of the Board, President or a Vice President or the Treasurer of the Guarantor to
execute, manually or by facsimile signature in the name and on behalf of the
Guarantor, and to confirm such Guarantee to the Holder of each such Security by
the execution and delivery of

                                       22
<PAGE>
 
each such Security, with such Guarantee endorsed thereon, authenticated and
delivered by the Trustee. When delivered pursuant to the provisions of Section
303 hereof, the Guarantee so set forth on the Security shall bind the Guarantor
notwithstanding the fact that such Guarantee does not bear the signature of the
Guarantor.

     Each Guarantee shall be dated the date of the Security upon which it is
endorsed.  Reference is made to Articles Fourteen and Eighteen for further
provisions with respect to the Guarantees.

Section 203.  Form of Trustee's Certificate of Authentication.
              -----------------------------------------------      

     Subject to Section 612, the Trustee's certificate of authentication shall
be in substantially the form attached to this Indenture as Exhibit B.
                                                           ----------

Section 204.  Securities in Global Form.
              -------------------------     

     Unless otherwise provided in or pursuant to this Indenture, the Securities
initially shall be issued in global form.  Securities issued in temporary or
permanent global form may provide that it or any number of such Securities shall
represent the aggregate principal amount of all Outstanding Securities of such
series (or such lesser amount as is permitted by the terms thereof) from time to
time endorsed thereon and may also provide that the aggregate amount of
Outstanding Securities represented thereby may from time to time be increased or
reduced to reflect exchanges.  Any global Security authenticated and delivered
hereunder may bear any legend or other statement required to comply with the
requirements of any Depository or Common Depository.  Any endorsement of any
global Security to reflect the amount, or any increase or decrease in the
amount, or changes in the rights of Holders, of Outstanding Securities
represented thereby shall be made in such manner and by such Person or Persons
as shall be specified therein.  Subject to the provisions of Section 303 and, if
applicable, Section 304, the Trustee shall deliver and redeliver any Security in
permanent global form in a manner mutually acceptable to the Company and the
Trustee and upon instructions given by an Officer.  If a Company Order pursuant
to Section 303 or 304 has been, or simultaneously is, delivered, any
instructions by the Company with respect to a Security in global form shall be
in writing but need not be accompanied by or contained in a Company Officers'
Certificate and need not be accompanied by an Opinion of Counsel.

     Notwithstanding the provisions of Section 307, unless otherwise specified
in or pursuant to this Indenture or any Securities, payment of principal of, any
premium and (except for temporary global Bearer Securities (as contemplated by
Section 304 hereof)) interest on, and any Additional Amounts in respect of, any
temporary or permanent global Security shall be made to the Person or Persons
specified therein.

     Notwithstanding the provisions of Section 308 and except as provided in the
preceding paragraph, the Company, the Trustee and any agent of the Company and
the Trustee shall treat as the Holder of such principal amount of Outstanding
Securities represented by a global Security (i) in the case of a global Security
in registered form, the Holder of such global Security in

                                       23
<PAGE>
 
registered form, or (ii) in the case of a temporary global Security in bearer
form, the Person or Persons specified pursuant to Section 301.

Section 205.  Form of Conversion Notice.
              -------------------------     

     At the time of conversion of a Security in accordance with Article Twelve,
the Holder of such Security shall deliver to the Trustee, the Conversion Agent,
the Company and the Guarantor a notice of conversion in substantially the form
attached to this Indenture as Exhibit C.
                              --------- 


                               ARTICLE THREE

                              THE SECURITIES

Section 301.  Amount Unlimited; Issuable in Series.
              ------------------------------------     

     The aggregate principal amount of Securities which may be authenticated and
delivered and outstanding under this Indenture is unlimited. The Securities may
be issued in one or more series.

     With respect to any Securities to be authenticated and delivered hereunder,
there shall be established in or pursuant to one or more Company Board
Resolutions and Guarantor Board Resolutions, or pursuant to authority granted by
one or more Company Board Resolutions and Guarantor Board Resolutions and,
subject to Section 303, set forth or determined in the manner provided in a
Company and Guarantor Officers' Certificate, or established in one or more
indentures supplemental hereto prior to the issuance of any Securities of a
series any or all of the following; provided that if any of the following are
                                    -------- ----                            
already provided for in this Indenture, then such provisions shall be applicable
to each series established hereunder unless otherwise provided pursuant to the
Company and Guarantor Board Resolutions establishing such series and set forth
in the applicable Company and Guarantor Officers' Certificate or unless
otherwise provided in any Indenture or Indentures supplemental hereto pertaining
to such series of Securities:

          (1)  the title or designation of such Securities and the series in
     which such Securities shall be included;

          (2)  any limit upon the aggregate principal amount of the Securities
     of such title or designation or the Securities of such series which may be
     authenticated and delivered under this Indenture (except for Securities
     authenticated and delivered upon registration or transfer of, or in
     exchange for, or in lieu of, other Securities of such series pursuant to
     Section 304, 305, 306, 905 or 1107, upon repayment in part of any Security
     of such series pursuant to Article Fifteen, or upon surrender in part of
     any Security for conversion or exchange into other securities pursuant to
     its terms, or pursuant to the terms of such Securities);

                                       24
<PAGE>
 
          (3)  if such Securities are to be issuable as Registered Securities,
     as Bearer Securities or alternatively as Bearer Securities and Registered
     Securities, and whether the Bearer Securities are to be issuable with
     Coupons, without Coupons or both, and any restrictions applicable to the
     offer, sale or delivery of the Bearer Securities and the terms, if any,
     upon which Bearer Securities may be exchanged for Registered Securities and
     vice versa;

          (4)  if any of such Securities are to be issuable in global form, when
     any of such Securities are to be issuable in global form and (i) whether
     such Securities are to be issued in temporary or permanent global form or
     both, (ii) the extent to which, or the manner in which, any interest
     payment or Additional Amounts on a global Security on an Interest Payment
     Date will be paid and the manner in which any principal of or premium, if
     any, on any global Security will be paid, (iii) whether beneficial owners
     of interests in any such global Security may exchange such interests for
     Securities of the same series and of like tenor and of any authorized form
     and denomination, and the circumstances under which any such exchanges may
     occur, if other than in the manner specified in Section 305, (iv) the name
     of the Depository or the U.S. Depository, as the case may be, with respect
     to any global Security, (v) the name of the Common Depository, if
     applicable, and (vi) the Exchange Date, if applicable;

          (5)  if any of such Securities are to be issuable as Bearer Securities
     or in global form, the date as of which any such Bearer Security or global
     Security shall be dated (if other than the date of original issuance of the
     first of such Securities to be issued);

          (6)  if any of such Securities are to be issuable as Bearer
     Securities, whether interest in respect of any portion of a temporary
     Bearer Security in global form payable in respect of an Interest Payment
     Date therefor prior to the Exchange Date, shall be paid to any clearing
     organization with respect to the portion of such temporary Bearer Security
     held for its account and, in such event, the terms and conditions
     (including any certification requirements) upon which any such interest
     payment received by a clearing organization will be credited to the Persons
     entitled to interest payable on such Interest Payment Date, if other than
     as provided in Section 304;

          (7)  the date or dates, or the method or methods, if any, by which
     such date or dates shall be determined, on which the principal of such
     Securities is payable;

          (8)  the rate or rates at which such Securities shall bear interest,
     if any, or the method or methods, if any, by which such rate or rates are
     to be determined, the date or dates, if any, from which such interest shall
     accrue or the method or methods, if any, by which such date or dates are to
     be determined, the Interest Payment Dates, if any, on which such interest
     shall be payable and the Regular Record Dates, if any, for the interest
     payable on Registered Securities on any Interest Payment Date, whether and
     under what circumstances Additional Amounts on such Securities or any of
     them shall be payable, the notice, if any, to Holders regarding the
     determination of interest on a floating rate Security and the manner of
     giving such notice, and the basis upon which interest shall be calculated
     if other than that of a 360-day year of twelve 30-day months;

                                       25
<PAGE>
 
          (9)  if in addition to or other than the Borough of Manhattan, The
     City of New York (or, in the case of Bearer Securities, except as otherwise
     provided herein, London, England), the place or places where the principal
     of, any premium and interest on or any Additional Amounts with respect to
     such Securities shall be payable, any of such Securities may be surrendered
     for registration of transfer and exchange, any of such Securities may be
     surrendered for transfer, exchange or conversion in the circumstances
     described herein and notices or demands to or upon the Company or the
     Guarantor in respect of such Securities and this Indenture may be served;

          (10) whether any of such Securities are to be redeemable at the option
     of the Company and, if so, the date or dates on which, the period or
     periods within which, the price or prices at which and the other terms and
     conditions upon which such Securities may be redeemed, in whole or in part,
     at the option of the Company and, if other than by a Company Board
     Resolution, the manner in which any election by the Company to redeem the
     Securities shall be evidenced;

          (11) if the Company is obligated to redeem or purchase any of such
     Securities pursuant to any sinking fund or analogous provision or at the
     option of any Holder thereof and, if so, the date or dates on which, the
     period or periods within which, the price or prices at which and the other
     terms and conditions upon which such Securities shall be redeemed or
     purchased, in whole or in part, pursuant to such obligation, and any
     provisions for the remarketing of such Securities so redeemed or purchased;

          (12) the denominations in which any of such Securities that are
     Registered Securities shall be issuable if other than denominations of
     $1,000 and any integral multiple thereof, and the denominations in which
     any of such Securities that are Bearer Securities shall be issuable if
     other than the denominations of $1,000 and $10,000;

          (13) if other than the principal amount thereof, the portion of the
     principal amount of any of such Securities that shall be payable upon
     declaration of acceleration of the Maturity thereof pursuant to Section 502
     or the method by which such portion is to be determined;

          (14) if the amount of payments of principal of, any premium or
     interest on or any Additional Amounts with respect to such Securities may
     be determined with reference to an index, indices, formula or other method
     or methods (which index, indices, formula or method or methods may be
     based, without limitation, on one or more currencies, commodities, equity
     indices or other indices), and, if so, the terms and conditions upon which
     and the manner in which such amounts shall be determined and paid or
     payable;

          (15) any deletions from, modifications of or additions to the Events
     of Default or covenants of the Company with respect to any of such
     Securities, whether or not such Events of Default or covenants are
     consistent with the Events of Default or covenants set forth herein;

                                       26
<PAGE>
 
          (16) if either or both of Section 402(2) relating to defeasance or
     Section 402(3) relating to covenant defeasance shall  be applicable to the
     Securities of such series, or any covenants in addition to those specified
     in Section 402(3) relating to the Securities of such series which shall be
     subject to covenant defeasance, and any deletions from, or modifications or
     additions to, the provisions of Article Four in respect of the Securities
     of such series shall apply;

          (17) the terms, if any, on which such Securities may be converted into
     or exchanged for other securities of the Company;

          (18) if any of such Securities are to be issuable in global form and
     are to be issuable in definitive form (whether upon original issue or upon
     exchange of a temporary Security) only upon receipt of certain certificates
     or other documents or satisfaction of other conditions, then the form and
     terms of such certificates, documents or conditions;

          (19) if there is more than one Trustee, the identity of the Trustees
     and, if not the Trustee, the identity of each Security Registrar, and the
     identity of each Paying Agent, Conversion Agent or Authenticating Agent
     with respect to such Securities;

          (20) the subordination provisions with respect to the Securities and
     Guarantees if other than as set forth in Article Seventeen or Eighteen,
     respectively; and

          (21) any other terms of such Securities and any deletions from or
     modifications or additions to this Indenture in respect of such Securities
     (which terms shall not be inconsistent with the provisions of this
     Indenture, except as permitted by Section 901).

     All Securities (and Guarantees endorsed thereon) of any one series and all
Coupons, if any, appertaining to Bearer Securities of such series shall be
substantially identical except as to denomination and Maturity and except as may
otherwise be provided by the Company in or pursuant to the Company Board
Resolution and (subject to Section 303) set forth in the Company Officers'
Certificate or in any indenture or indentures supplemental hereto pertaining to
such series of Securities.  The terms of the Securities of any series (as set
forth in or pursuant to the applicable Board Resolution) may provide, without
limitation, that the Securities shall be authenticated and delivered by the
Trustee on original issue from time to time upon telephonic or written order of
persons designated in the Company Officers' Certificate or supplemental
indenture (telephonic instructions to be promptly confirmed in writing by such
person) and that such persons are authorized to determine, consistent with such
Company Officers' Certificate or any applicable supplemental indenture, such
terms and conditions of the Securities of such series as are specified in such
Company Officers' Certificate or supplemental indenture.  All Securities of any
one series need not be issued at the same time and, unless otherwise so provided
by the Company, a series may be reopened for issuances of additional Securities
of such series.

     If any of the terms of the Securities of any series shall be established
and approved by action taken by or pursuant to Board Resolutions of the Company
and the Guarantor, respectively, copies of appropriate records of such actions
shall be certified by the Secretary or an Assistant Secretary of the Company and
the Guarantor, respectively, and delivered to the

                                       27
<PAGE>
 
Trustee at or prior to the delivery of the Officers' Certificates setting forth
the terms of such series.

Section 302.  Currency; Denominations.
              -----------------------     

     The principal of, any premium and interest on and any Additional Amounts
with respect to the Securities shall be payable in Dollars. Unless otherwise
provided in or pursuant to this Indenture, Registered Securities shall be
issuable in registered form without Coupons in denominations of $1,000 and any
integral multiple thereof, and Bearer Securities shall be issuable in
denominations of $1,000 and $10,000 (or any other authorized denominations) with
Coupons attached.

Section 303.  Execution, Authentication, Delivery and Dating.
              ----------------------------------------------     

     Securities shall be executed on behalf of the Company by any Officer under
its corporate seal reproduced thereon and attested by its Corporate Secretary
(provided that the Corporate Secretary shall not attest his or her own signature
as an Officer) or one of its Assistant Corporate Secretaries.  Coupons shall be
executed on behalf of the Company by any Officer.  The signature of any of these
officers on the Securities or any Coupons appertaining thereto may be manual or
facsimile.

     Securities, Coupons appertaining thereto and Guarantees bearing the manual
or facsimile signatures of individuals who were at any time the proper Officers
of the Company or the Guarantor shall bind the Company and the Guarantor,
respectively, notwithstanding that such individuals or any of them have ceased
to hold such offices prior to the authentication and delivery of such
Securities, Coupons or Guarantees or did not hold such offices at the date of
such Securities, Coupons or Guarantees.

     At any time and from time to time after the execution and delivery of this
Indenture, the Company may deliver Securities, together with any Coupons
appertaining thereto, executed by the Company, having endorsed thereon
Guarantees of the Guarantor, to the Trustee for authentication and, provided
that the Company and Guarantor Board Resolutions, Company and Guarantor
Officers' Certificate (if the terms of such Securities are provided therein
pursuant to authority granted by Company and Guarantor Board Resolution) or
supplemental indenture or indentures with respect to such Securities referred to
in Section 301 and a Company Order for the authentication and delivery of such
Securities and a Guarantor Order (which may be included as part of the Company
Order for the authentication and delivery of the Securities) approving the
delivery of the Guarantees endorsed thereon have been delivered to the Trustee,
the Trustee in accordance with the Company and Guarantor Orders and subject to
the provisions hereof and of such Securities shall authenticate and deliver such
Securities having such Guarantees; provided, however, that, in connection with
                                   -----------------                          
its original issuance, no Bearer Security shall be mailed or otherwise delivered
to any location in the United States; and provided, further, that a Bearer
                                          -----------------               
Security (other than a temporary global Bearer Security) may be delivered
outside the United States in connection with its original issuance only if the
certifications described in Section 304 are provided in accordance with the
provisions of Section 304.  If any Security shall be represented by a permanent
global Security, then, for purposes of this Section and Section 304,

                                       28
<PAGE>
 
the notation of a beneficial owner's interest therein upon original issuance of
such Security or upon exchange of a portion of a temporary global Security shall
be deemed to be delivery in connection with the original issuance of such
beneficial owner's interest in such permanent global Security. Except as
permitted by Section 306, the Trustee for the Securities of a series shall not
authenticate and deliver any Bearer Security (or related Guarantee) unless all
appurtenant Coupons for interest then matured other than matured coupons in
default have been detached and canceled. If all the Securities of any one series
are not to be issued at one time and if a Board Resolution relating to such
Securities or Officers' Certificate shall so permit, such Officers' Certificate
may include provisions for the issuance of such Securities, including, without
limitation, provisions with respect to interest rate, Stated Maturity, date of
issuance and date from which interest, if any, shall accrue.

     In authenticating such Securities, and accepting the additional
responsibilities under this Indenture in relation to such Securities and any
Coupons appertaining thereto, the Trustee shall be entitled to receive, and
(subject to Sections 315(a) through 315(d) of the Trust Indenture Act) shall be
fully protected in relying upon:

          (1)  an Opinion of Counsel to the effect that:

          (a)  the form or forms and terms of such Securities and Coupons, if
     any, and Guarantees have been established or approved by or pursuant to
     Board Resolutions of the Company and the Guarantor in conformity with
     Sections 201 and 301 of this Indenture;

          (b)  all conditions precedent to the authentication and delivery of
     such Securities and Coupons, if any, appertaining thereto, and to the
     delivery of such Guarantees have been complied with and that such
     Securities, Coupons and Guarantees, when completed by appropriate
     insertions, executed under the Company's corporate seal and attested by
     duly authorized officers of the Company (in the case of the Securities or
     Coupons) or when completed by appropriate insertions, executed under the
     Guarantor's corporate seal and attested by duly authorized officers of the
     Guarantor (in the case of the Guarantees), delivered by duly authorized
     officers of the Company or the Guarantor, as the case may be, to the
     Trustee for authentication pursuant to this Indenture, and authenticated
     and delivered by the Trustee and issued by the Company and the Guarantor in
     the manner and subject to any conditions specified in such Opinion of
     Counsel, will constitute legally valid and binding obligations of the
     Company and of the Guarantor, respectively, enforceable in accordance with
     their terms, subject, in the case of the Securities to bankruptcy,
     insolvency, reorganization, moratorium, arrangement, fraudulent conveyance,
     fraudulent transfer or other similar laws of general applicability to the
     Company and relating to or affecting creditors' rights and to general
     principles of equity (regardless of whether enforcement is sought in a
     proceeding in equity or at law), and subject, in the case of the
     Guarantees, to bankruptcy, insolvency, reorganization, moratorium,
     arrangement, fraudulent conveyance, fraudulent transfer or other similar
     laws of general applicability to the Guarantor and relating to or affecting
     creditors' rights and to general principles of equity (regardless of
     whether enforcement is sought in a proceeding in equity or at law); and

                                       29
<PAGE>
 
          (c)  this Indenture has been qualified under the Trust Indenture Act;
     and

          (2)  a Company Officers' Certificate and Guarantor Officer's
     Certificate, each stating that, to the best knowledge of the Persons
     executing such certificate, no Default or Event of Default with respect to
     any of the Securities shall have occurred and be continuing.

     If all of the Securities of any series are not to be issued at one time,
unless requested by the Trustee, it shall not be necessary to deliver an Opinion
of Counsel at the time of issuance of each Security, but such opinion, with such
modifications as counsel shall deem appropriate, shall be delivered at or before
the time of issuance of the first Security of such series. After any such first
delivery, any separate request by the Company that the Trustee authenticate
additional Securities of such series for original issue will be deemed to be a
certification by the Company that all conditions precedent provided for in this
Indenture relating to authentication and delivery of such Securities continue to
have been complied with.

     The Trustee shall not be required to authenticate or to cause an
Authenticating Agent to authenticate any Securities if the issue of such
Securities pursuant to this Indenture will affect the Trustee's own rights,
duties or immunities under the Securities and this Indenture or otherwise in a
manner which is not reasonably acceptable to the Trustee or if the Trustee,
being advised by counsel, determines that such action may not lawfully be taken.

     Each Security shall be dated as of the date specified in or pursuant to
this Indenture.

     No Security or Guarantee endorsed thereon or Coupon appertaining to such
Security shall be entitled to any benefit under this Indenture or be valid or
obligatory for any purpose, unless there appears on such Security a certificate
of authentication substantially in the form provided for in Section 203 or 612
executed by or on behalf of the Trustee or by the Authenticating Agent by the
manual signature of one of its authorized officers.  Such certificate upon any
Security shall be conclusive evidence, and the only evidence, that such Security
has been duly authenticated and delivered hereunder.  Except as permitted by
Section 306 or 307, the Trustee shall not authenticate or deliver any Bearer
Security (or related Guarantee) unless all Coupons appertaining thereto then
matured have been detached and canceled.

Section 304.  Temporary Securities.
              --------------------     

     (a)  Pending the preparation of Definitive Securities, the Company may
execute and deliver to the Trustee and, upon Company Order and a Guarantor Order
for authentication and delivery, the Trustee shall authenticate and deliver, in
the manner provided in Section 303, temporary Securities in lieu thereof which
are printed, lithographed, typewritten, mimeographed or otherwise produced, in
any authorized denomination, substantially of the tenor of the Definitive
Securities in lieu of which they are issued, in registered form or, if
authorized in or pursuant to this Indenture, in bearer form with one or more
Coupons or without Coupons, and having endorsed thereon Guarantees of the
Guarantor substantially of the tenor of the definitive Guarantees, with such
appropriate insertions, omissions, substitutions and other variations as the
officers executing such Securities or Guarantees may determine, as conclusively
evidenced

                                       30
<PAGE>
 
by their execution of such Securities or Guarantees. Such temporary Securities
may be in global form.

     (b)  Except in the case of temporary global Bearer Securities, which shall
be exchanged in accordance with the provisions of clause (c) of this Section
304, if temporary Securities are issued, the Company shall cause Definitive
Securities to be prepared without unreasonable delay. After the preparation of
Definitive Securities of the same series and containing terms and provisions
that are identical to those of any temporary Securities, such temporary
Securities shall be exchangeable for such Definitive Securities with Guarantees
of the Guarantor endorsed thereon upon surrender of such temporary Securities at
an Office or Agency for such Securities, without charge to any Holder thereof.
Upon surrender for cancellation of any one or more temporary Securities
(accompanied by any unmatured Coupons appertaining thereto), the Company shall
execute and the Trustee shall authenticate and deliver in exchange therefor a
like principal amount of Definitive Securities of authorized denominations of
the same series and containing identical terms and provisions which have
endorsed thereon the Guarantees of the Guarantor; provided, however, that no
                                                  --------  -------
definitive Bearer Security, except as provided in or pursuant to this Indenture,
shall be delivered in exchange for a temporary Registered Security; and
provided, further, that a definitive Bearer Security shall be delivered in
- --------  -------
exchange for a temporary global Bearer Security only in compliance with the
conditions set forth in or pursuant to this Indenture. Unless otherwise provided
in or pursuant to this Indenture with respect to a temporary global Bearer
Security, until so exchanged the temporary Securities of any series shall in all
respects be entitled to the same benefits under this Indenture as Definitive
Securities of such series.

     (c)  All or a portion of the Securities constituting Bearer Securities may
be initially issued as temporary global Bearer Securities without Coupons or
conversion rights, having endorsed thereon the Guarantees. Such temporary global
Bearer Securities shall be deposited on the applicable closing date on behalf of
the subscribers for the Securities represented thereby with the Common
Depository, for credit to their respective accounts (or to such other accounts
as they may direct) at Morgan Guaranty Trust Company of New York, Brussels
Office, as operator of the Euroclear Clearance System ("Euroclear"), or Cedel
Bank, Societe Anonyme ("Cedel").

     On or before the Exchange Date, the Company shall deliver to the Paying
Agent in London at its principal London office or to its designated agent
outside the United States, definitive Bearer Securities with Guarantees of the
Guarantor endorsed thereon.  On or after the applicable Exchange Date, the
temporary global Bearer Securities may  be surrendered by the Common Depository
to the Trustee, to be exchanged, in whole or from time to time in part, for
definitive Bearer Securities without charge to Holders, and the Trustee or the
Paying Agent in London or other Paying Agent outside the United States shall
authenticate and deliver (at an office or agency outside the United States), in
exchange for the temporary global Bearer Securities or the portions thereof to
be exchanged, an equal aggregate principal amount of definitive Bearer
Securities, as shall be specified by the Holders thereof; provided, however,
                                                          --------  ------- 
that upon such presentation by the Common Depository, the temporary global
Bearer Securities are accompanied by a certificate dated the Exchange Date or a
subsequent date and signed by Euroclear as to the portion of the temporary
global Bearer Securities held for its account then to be exchanged and a
certificate dated the Exchange Date or a subsequent date and signed by Cedel

                                       31
<PAGE>
 
as to the portion of the temporary global Bearer Securities held for its account
then to be exchanged, each substantially in the form of Exhibit E hereto to the
                                                        ---------
effect that it has received a certificate or certificates substantially in the
form of Exhibit D hereto dated no earlier than 15 days prior to the Exchange
        ---------    
Date and signed by the person appearing in its records as the owner of the
temporary global Bearer Securities or portions thereof being exchanged. The
Company hereby appoints the principal office of the Paying Agent in London,
England, or its designated agent, as its agent outside the United States where
definitive Bearer Securities may be delivered in exchange for the temporary
global Bearer Securities or portions thereof. Each beneficial owner of any
portion of the temporary global Bearer Securities shall be entitled to take
delivery of definitive Bearer Securities only at such office. Upon the exchange
of the temporary global Bearer Security in whole for definitive Bearer
Securities or for Registered Securities (if permitted by the rules and
procedures then in effect of Cedel and Euroclear), the temporary global Bearer
Security shall be canceled in accordance with Section 309 of this Indenture.

     Temporary global Bearer Securities will be exchangeable for Registered
Securities in denominations of $1,000 or an integral multiple thereof at any
time without the certification requirements set forth in the preceding
paragraph; provided that such exchange is permitted by the rules and procedures
           -------- ----                                                       
then in effect of Cedel and Euroclear, and provided, further, that if and so
                                           --------- -------                
long as Registered Securities of a series are represented solely by a permanent
global Registered Security, the temporary global Bearer Security will only be
exchangeable for an interest in the permanent global Registered Security as set
forth in Section 305 herein.

     Notwithstanding any other provision hereof or of the Securities, no Bearer
Security initially represented by a temporary global Bearer Security will be
mailed to or otherwise delivered in connection with its original issuance to any
location within the United States.  The Trustee agrees that it will cause the
Paying Agent in London (if any) to retain each certificate provided by Euroclear
or Cedel for a period of four calendar years following the year in which the
certificate is received and not to destroy or otherwise dispose of any such
certificate without first offering to deliver it to the Company.

     Upon any such exchange of a portion of the temporary global Bearer Security
for definitive Bearer Securities, or for Registered Securities (if permitted by
the rules and procedures then in effect of Cedel and Euroclear), the existing
temporary global Bearer Security shall be canceled by the Trustee in accordance
with Section 309 of this Indenture.  The Company shall deliver to the Trustee
for authentication, and the Trustee shall authenticate and deliver (at an office
or agency located outside the United States), a temporary global Bearer Security
representing the portion of the temporary global Bearer Security not so
exchanged.  Until so exchanged in full, the temporary global Bearer Security
shall in all respects be entitled to the same benefits under, and subject to the
same terms and conditions of, this Indenture as definitive Bearer Securities
authenticated and delivered hereunder, except that none of Euroclear, Cedel or
the beneficial owners of the temporary global Bearer Security shall be entitled
to receive payment of interest or other payments thereon or to convert the
temporary global Bearer Security, if applicable, or any portion thereof, as set
forth in Article Twelve, except as otherwise permitted pursuant to this
Indenture or the Securities.

                                       32
<PAGE>
 
Section 305.  Registration, Transfer and Exchange.
              -----------------------------------     

     With respect to the Registered Securities of each series, if any, the
Company shall cause to be kept a register (each such register being herein
sometimes referred to as the "Security Register") at an Office or Agency for
                              -----------------                             
such series in which, subject to such reasonable regulations as it may
prescribe, the Company shall provide for the registration of the Registered
Securities of such series and of transfers of the Registered Securities of such
series. Such Office or Agency shall be the "Security Registrar" for that series
                                            ------------------                 
of Securities.  Unless otherwise specified in or pursuant to this Indenture or
the Securities, the Trustee shall be the initial Security Registrar for each
series of Securities.  The Company shall have the right to remove and replace
from time to time the Security Registrar for any series of Securities; provided
                                                                       --------
that no such removal or replacement shall be effective until a successor
- ----                                                                    
Security Registrar with respect to such series of Securities shall have been
appointed by the Company and shall have accepted such appointment.  In the event
that the Trustee shall not be or shall cease to be Security Registrar with
respect to a series of Securities, it shall have the right to examine the
Security Register for such series at all reasonable times. There shall be only
one Security Register for each series of Securities.

     Upon surrender for registration of transfer of any Registered Security of
any series at any Office or Agency for such series, the Company shall execute,
and the Trustee shall authenticate and deliver, in the name of the designated
transferee or transferees, one or more new Registered Securities of the same
series denominated as authorized in or pursuant to this Indenture, of a like
aggregate principal amount bearing a number not contemporaneously outstanding
and containing identical terms and provisions, having endorsed thereon the
Guarantee duly executed by the Guarantor.

     At the option of the Holder, Registered Securities of any series may be
exchanged for other Registered Securities of the same series containing
identical terms and provisions, in any authorized denominations, and of a like
aggregate principal amount, upon surrender for cancellation of the Securities to
be exchanged at any applicable Office or Agency for such series. Whenever any
Registered Securities are so surrendered for exchange, the Company shall
execute, and the Trustee shall authenticate and deliver, the Registered
Securities which the Holder making the exchange is entitled to receive, having
endorsed thereon Guarantees of the Guarantor which the Holder is entitled to
receive. Registered Securities of any series may not be exchanged for Bearer
Securities.

     At the option of the Holder, definitive Bearer Securities of such series
may be exchanged at any time (except as otherwise provided in this Indenture)
for Registered Securities or Bearer Securities of such series containing
identical terms, denominated as authorized in or pursuant to this Indenture and
in the same aggregate principal amount, upon surrender for cancellation of the
Bearer Securities to be exchanged at any applicable Office or Agency for such
series located outside the United States, with any and all unmatured Coupons and
any and all matured Coupons in default thereto appertaining; provided that if
                                                             -------- ----   
and so long as Registered Securities of a series are represented solely by a
permanent global Registered Security, such definitive Bearer Securities will
only be exchangeable for an interest in the permanent global Registered Security
as set forth in this Section 305.  If the Holder of a Bearer Security is unable
to produce any such unmatured Coupon or Coupons or matured Coupon or Coupons in
default, such exchange may

                                       33
<PAGE>
 
be effected if the Bearer Securities are accompanied by payment in funds
acceptable to the Company, the Guarantor and the Trustee in an amount equal to
the face amount of such missing Coupon or Coupons, or the surrender of such
missing Coupon or Coupons may be waived by the Company, the Guarantor and the
Trustee if there is furnished to them such security or indemnity as they may
require to save each of them and any Paying Agent harmless. If thereafter the
Holder of such Bearer Security shall surrender to any Paying Agent any such
missing Coupon in respect of which such a payment shall have been made, such
Holder shall be entitled to receive the amount of such payment; provided,
                                                                --------
however, that, except as otherwise provided in Section 1002, interest
- -------
represented by Coupons shall be payable only upon presentation and surrender of
those Coupons at an applicable Office or Agency for such series located outside
the United States. Notwithstanding the foregoing, in case a Bearer Security of
any series is surrendered at any such Office or Agency for such series in
exchange for a Registered Security of such series and like tenor after the close
of business at such Office or Agency on (i) any Regular Record Date and before
the opening of business at such Office or Agency on the relevant Interest
Payment Date, or (ii) any Special Record Date and before the opening of business
at such Office or Agency on the related date for payment of Defaulted Interest,
such Bearer Security shall be surrendered without the Coupon relating to such
Interest Payment Date or proposed date for payment of Defaulted Interest, as the
case may be (or, if such Coupon is so surrendered with such Bearer Security,
such Coupon shall be returned to the Person so surrendering the Bearer
Security), and interest or Defaulted Interest, as the case may be, shall not be
payable on such Interest Payment Date or proposed date for payment of Defaulted
Interest, as the case may be, in respect of the Registered Security issued in
exchange for such Bearer Security, but shall be payable only to the Holder of
such Coupon when due in accordance with the provisions of this Indenture.

     Whenever any Securities are surrendered for exchange as contemplated by the
immediately preceding two paragraphs, the Company shall execute, and the Trustee
shall authenticate and deliver, the Securities (with all Coupons, in the case of
the issuance of Bearer Securities), having endorsed thereon Guarantees of the
Guarantor, which the Holder making the exchange is entitled to receive.

     If the Holder of definitive Bearer Securities or definitive Registered
Securities requests in writing that such Securities be exchanged for an interest
in the applicable permanent global Registered Security, such Bearer Securities
or Registered Securities (as the case may be) will be exchangeable into an equal
aggregate principal amount of beneficial interest in the permanent global
Registered Security; provided that in the case of definitive Bearer Securities,
                     -------- ----                                             
such Bearer Securities are only exchanged in the manner set forth in this
Section 305 with respect to the exchange of definitive Bearer Securities for
Registered Securities and in the case of Registered Securities, such exchange is
made in accordance with the rules and procedures then in effect of the
Depository.  Upon any exchange as provided in the immediately preceding
sentence, the Trustee shall cancel such Bearer Securities or Registered
Securities (as the case may be) and cause, or direct any custodian for the
permanent global Registered Security to cause, in accordance with the standing
instructions and procedures existing between the Depository and any such
custodian, the aggregate principal amount of Securities represented by the
permanent global Registered Security to be increased accordingly.  If no
permanent global Registered Securities are then outstanding, the Company shall
issue and the Trustee shall authenticate a new

                                       34
<PAGE>
 
permanent global Registered Security in the appropriate principal amount, having
endorsed thereon a Guarantee duly executed by the Guarantor.

     Notwithstanding the foregoing, except as otherwise provided in or pursuant
to this Indenture, any permanent global Registered Security shall be
exchangeable for Definitive Securities in registered form only if (i) the
Depository is at any time unwilling, unable or ineligible to continue as
Depository or ceases to be a clearing agency registered under the Exchange Act
(if so required by applicable law or regulation) and a successor depository is
not appointed by the Company within 90 days of the date the Company is so
informed in writing, (ii) the Company executes and delivers to the Trustee a
Company Order to the effect that such permanent global Registered Security shall
be so exchangeable or (iii) an Event of Default has occurred and is continuing
with respect to the Securities.  If the beneficial owners of interests in a
permanent global Registered Security are entitled to exchange such interests for
Definitive Securities in registered form as the result of an event described in
clause (i), (ii) or (iii) of the preceding sentence, then without unnecessary
delay but in any event not later than the earliest date on which such interests
may be so exchanged, the Company shall deliver to the Trustee Definitive
Securities in such form and denominations as are required by or pursuant to this
Indenture, and of the same series, containing identical terms and in aggregate
principal amount equal to the principal amount of such permanent global
Registered Security, executed by the Company. On or after the earliest date on
which such interests may be so exchanged, such permanent global Registered
Security shall be surrendered from time to time by the U.S. Depository or such
other Depository as shall be specified in the Company Order with respect
thereto, and in accordance with instructions given to the Trustee and the U.S.
Depository or such other Depository, as the case may be (which instructions
shall be in writing but need not be contained in or accompanied by an Officers'
Certificate or be accompanied by an Opinion of Counsel), as shall be specified
in the Company Order with respect thereto to the Trustee, as the Company's agent
for such purpose, to be exchanged, in whole or in part, for Definitive
Securities as described above without charge. The Trustee shall authenticate and
make available for delivery, in exchange for each portion of such surrendered
permanent global Registered Security, a like aggregate principal amount of
Definitive Securities of the same series of authorized denominations and of like
tenor as the portion of such permanent global Registered Security to be
exchanged, which shall be in the form of Registered Securities; provided,
however, that no such exchanges may occur during a period beginning at the
opening of business 15 days before any selection of Securities of the same
series to be redeemed and ending at the close of business on the day of such
selection. Promptly following any such exchange in part, a permanent global
Registered Security for the portions not exchanged shall be returned by the
Trustee to such Depository or the U.S. Depository, as the case may be, or such
other Depository or U.S. Depository referred to above in accordance with the
instructions of the Company referred to above. If a Registered Security is
issued in exchange for any portion of a permanent global Registered Security
after the close of business at the applicable Office or Agency for such Security
where such exchange occurs on or after (i) any Regular Record Date for such
Security and before the opening of business at such Office or Agency on the next
Interest Payment Date, or (ii) any Special Record Date for such Security and
before the opening of business at such Office or Agency on the related proposed
date for payment of Defaulted Interest, as the case may be, interest shall not
be payable on such Interest Payment Date or proposed date for payment of
Defaulted Interest, as the case may be, in respect of such Registered Security,
but shall be

                                       35
<PAGE>
 
payable on such Interest Payment Date or proposed date for payment of Defaulted
Interest, as the case may be, only to the Person to whom interest in respect of
such portion of such permanent global Registered Security shall be payable in
accordance with the provisions of this Indenture.

     All Securities issued upon any registration of transfer or exchange of
Securities, and all Guarantees endorsed thereon, shall be the valid obligations
of the Company or the Guarantor, as the case may be, evidencing the same debt
and entitling the Holders thereof to the same benefits under this Indenture as
the Securities and all the Guarantees endorsed thereon surrendered upon such
registration of transfer or exchange.

     Every Registered Security presented or surrendered for registration of
transfer or for exchange or redemption shall (if so required by the Company or
the Security Registrar for such Security) be duly endorsed, or be accompanied by
a written instrument of transfer in form satisfactory to the Company and the
Security Registrar for such Security duly executed by the Holder thereof or his
attorney duly authorized in writing.

     No service charge shall be made for any registration of transfer or
exchange, or redemption of Securities, but the Company may require payment of a
sum sufficient to cover any stamp or similar tax or other governmental charge
and any other expenses (including fees and expenses of the Trustee) that may be
imposed in connection with any registration of transfer or exchange of
Securities, other than exchanges pursuant to Section 304, 905, 1107 or 1202, or
upon repayment in part of any Registered Security pursuant to Article Fifteen,
in each case not involving any transfer.

     Except as otherwise provided in or pursuant to this Indenture, the Company
shall not be required (i) to issue, register the transfer of or exchange any
Securities during a period beginning at the opening of business 15 days before
the day of the selection for redemption of Securities of like tenor and the same
series under Section 1103 and ending at the close of business on the day of such
selection, or (ii) to register the transfer of or exchange any Registered
Security so selected for redemption in whole or in part, except in the case of
any Security to be redeemed in part, the portion thereof not to be redeemed, or
(iii) to exchange any Bearer Security so selected for redemption except, to the
extent provided with respect to such Bearer Security, that such Bearer Security
may be exchanged for a Registered Security of like tenor and the same series,
provided that such Registered Security shall be immediately surrendered for
redemption with written instruction for payment consistent with the provisions
of this Indenture or (iv) to issue, register the transfer of or exchange any
Security which, in accordance with its terms, has been surrendered for repayment
at the option of the Holder, except the portion, if any, of such Security not to
be so repaid.

Section 306.  Mutilated, Destroyed, Lost and Stolen Securities.
              ------------------------------------------------     

     If any mutilated Security or a Security with a mutilated Coupon
appertaining to it is surrendered to the Trustee, subject to the provisions of
this Section 306, the Company shall execute and the Trustee shall authenticate
and deliver in exchange therefor a new Security of the same series containing
identical terms and of like principal amount, having endorsed thereon the
Guarantee of the Guarantor, and bearing a number not contemporaneously
outstanding, with

                                       36
<PAGE>
 
Coupons appertaining thereto corresponding to the Coupons, if any, appertaining
to the surrendered Security; provided, however, that any Bearer Security or any
                             --------  -------
Coupon shall be delivered only outside the United States and, if the Securities
of such series are listed on the London Stock Exchange or the Luxembourg Stock
Exchange or any other stock exchange located outside the United States and such
stock exchange shall so require, such delivery shall occur at the Office or
Agency located in London, Luxembourg or any other required city located outside
the United States, as the case may be, so long as Securities of such series are
listed on such exchange; and provided, further, that all Bearer Securities shall
                             --------  -------
be delivered and received in person.

     If there be delivered to the Company, the Guarantor and the Trustee (i)
evidence to their satisfaction of the destruction, loss or theft of any Security
or Coupon, and (ii) such security or indemnity as may be required by them to
save each of them and any agent of either of them harmless, then, in the absence
of notice to the Company, the Guarantor or the Trustee that such Security or
Coupon has been acquired by a bona fide purchaser, the Company shall execute
and, upon the Company's request the Trustee shall authenticate and deliver, in
exchange for or in lieu of any such mutilated, destroyed, lost or stolen
Security or in exchange for the Security to which a destroyed, lost or stolen
Coupon appertains with all appurtenant Coupons not destroyed, lost or stolen, a
new Security of the same series containing identical terms and of like principal
amount, having endorsed thereon the Guarantee of the Guarantor, and bearing a
number not contemporaneously outstanding, with Coupons corresponding to the
Coupons, if any, appertaining to such destroyed, lost or stolen Security or to
the Security to which such destroyed, lost or stolen Coupon appertains;
provided, however, that any Bearer Security or any Coupon shall be delivered
- --------  -------
only outside the United States and, if the Securities of such series are listed
on the London Stock Exchange or the Luxembourg Stock Exchange or any other stock
exchange located outside the United States and such stock exchange shall so
require, such delivery shall occur at the Office or Agency located in London,
Luxembourg or any other required city located outside the United States, as the
case may be, so long as Securities of such series are listed on such exchange;
and provided, further, that all Bearer Securities shall be delivered and
    --------  ------
received in person.

     Notwithstanding the foregoing provisions of this Section 306, in case any
mutilated, destroyed, lost or stolen Security or Coupon has become or will
become due and payable within seven (7) days, the Company in its discretion, but
subject to any conversion rights, may, instead of issuing a new Security, pay
such Security or Coupon; provided, however, that payment of principal of, any
                         --------  -------                                   
premium or interest on or any Additional Amounts with respect to any Bearer
Securities shall, except as otherwise provided in Section 1002, be payable only
at the applicable Office or Agency for such Securities located outside the
United States and, unless otherwise provided in or pursuant to this Indenture,
any interest on Bearer Securities and any Additional Amounts with respect to
such interest shall be payable only upon presentation and surrender of the
Coupons appertaining thereto.

     Upon the issuance of any new Security under this Section, the Company may
require the payment of a sum sufficient to cover any stamp or similar tax or
other governmental charge that may be imposed in relation thereto and any other
expenses (including the fees and expenses of the Trustee) connected therewith.

                                       37
<PAGE>
 
     Every new Security with any Coupons appertaining thereto, and the Guarantee
of the Guarantor endorsed thereon, issued pursuant to this Section 306 in lieu
of any mutilated, destroyed, lost or stolen Security, or in exchange for a
Security to which a mutilated, destroyed, lost or stolen Coupon appertains shall
constitute a separate obligation of the Company and the Guarantor, respectively,
whether or not the mutilated, destroyed, lost or stolen Security and Coupons
appertaining thereto or the mutilated, destroyed, lost or stolen Coupon shall be
at any time enforceable by anyone, and shall be entitled to all the benefits of
this Indenture equally and proportionately with any and all other Securities of
such series and any Coupons, and related Guarantees, duly issued hereunder.

 

     The provisions of this Section, as amended or supplemented pursuant to this
Indenture with respect to particular Securities or generally, shall be exclusive
and shall preclude (to the extent lawful) all other rights and remedies with
respect to the replacement or payment of mutilated, destroyed, lost or stolen
Securities or Coupons.

 

Section 307.  Payment of Interest and Certain Additional Amounts; Rights to
              -------------------------------------------------------------
Interest and Certain Additional Amounts Preserved.
- ------------------------------------------------- 


     (a) Unless otherwise provided in or pursuant to this Indenture, any
interest on and any Additional Amounts with respect to any Registered Security
which shall be payable, and are punctually paid or duly provided for, on any
Interest Payment Date shall be paid to the Person in whose name such Security
(or one or more Predecessor Securities) is registered as of the close of
business on the Regular Record Date for such interest.

     Unless otherwise provided as contemplated by Section 301 with respect to
the Securities of any series, payment of interest may be made (i) by check
mailed or delivered, in the case of Registered Securities, to the address of the
Person entitled thereto as such address shall appear in the Security Register
or, in the case of Bearer Securities, upon presentation and surrender of the
appropriate Coupon appertaining thereto, or (ii) at the option of the Company
with the consent of any Paying Agent, (1) in the case of a Bearer Security, upon
presentation and surrender of the applicable Coupon at an applicable Office or
Agency for such series outside the United States, except as otherwise provided
in Section 1002, by transfer to an account maintained by the payee with a bank
located outside the United States, or (2) in the case of a Registered Security,
by transfer to an account maintained by the payee with a bank located inside the
United States.

     Unless otherwise provided in or pursuant to this Indenture, in case a
Bearer Security is surrendered in exchange for a Registered Security after the
close of business at the applicable Office or Agency for such Security on any
Regular Record Date therefor and before the opening of business at such Office
or Agency on the next succeeding Interest Payment Date therefor, such Bearer
Security shall be surrendered without the Coupon relating to such Interest
Payment Date and interest shall not be payable on such Interest Payment Date in
respect of the Registered Security issued in exchange for such Bearer Security,
but shall be payable only to the Holder of such Coupon when due in accordance
with the provisions of this Indenture.

                                       38
<PAGE>
 
     Unless otherwise provided in or pursuant to this Indenture, any interest on
and any Additional Amounts with respect to any Bearer Security shall, except as
otherwise provided in Section 1002, be payable only at an Office or Agency for
such Securities located outside the United States.

     Interest on any temporary global Bearer Security shall be payable only
after the issuance of a Definitive Security for which it is exchangeable as
provided in Section 304, except as otherwise provided pursuant to this Indenture
or the Securities.

     (b) Unless otherwise provided in or pursuant to this Indenture, any
interest on and any Additional Amounts with respect to any Registered Security
which shall be payable, but shall not be punctually paid or duly provided for,
on any Interest Payment Date for such Registered Security (herein called
"Defaulted Interest") shall forthwith cease to be payable to the Holder thereof
 ------------------                                                            
on the relevant Regular Record Date by virtue of having been such Holder; and
such Defaulted Interest may be paid by the Company, at its election in each
case, as provided in Clause (1) or (2) below:

     (1) The Company may elect to make payment of any Defaulted Interest to the
Person in whose name such Registered Security (or a Predecessor Security
thereof) shall be registered at the close of business on a Special Record Date
for the payment of such Defaulted Interest, which shall be fixed in the
following manner.  The Company shall notify the Trustee in writing of the amount
of Defaulted Interest proposed to be paid on such Registered Security and the
date of the proposed payment, and at the same time the Company shall deposit
with the Trustee an amount of money equal to the aggregate amount proposed to be
paid in respect of such Defaulted Interest or shall make arrangements
satisfactory to the Trustee for such deposit on or prior to the date of the
proposed payment, such money when so deposited to be held in trust for the
benefit of the Person entitled to such Defaulted Interest as in this clause
provided. Thereupon, the Trustee shall fix a Special Record Date for the payment
of such Defaulted Interest which shall be not more than 15 days and not less
than 10 days prior to the date of the proposed payment and not less than 10 days
after receipt by the Trustee of the notice of the proposed payment. The Trustee
shall promptly notify the Company of such Special Record Date and, in the name
and at the expense of the Company, shall cause notice of the proposed payment of
such Defaulted Interest and the Special Record Date therefor to be mailed,
first-class postage prepaid, to the Holder of such Registered Security (or a
Predecessor Security thereof) at his address as it appears in the Security
Register not less than 10 days prior to such Special Record Date.  The Trustee
may, in its discretion, in the name and at the expense of the Company cause a
similar notice to be published at least once in an Authorized Newspaper of
general circulation in the Borough of Manhattan, The City of New York, but such
publication shall not be a condition precedent to the establishment of such
Special Record Date.  Notice of the proposed payment of such Defaulted Interest
and the Special Record Date therefor having been mailed as aforesaid, such
Defaulted Interest shall be paid to the Person in whose name such Registered
Security (or a Predecessor Security thereof) shall be registered at the close of
business on such Special Record Date and shall no longer be payable pursuant to
the following clause (2). In case a Bearer Security is surrendered at the
applicable Office or Agency for such Security in exchange for a Registered
Security after the close of business at such Office or Agency on any Special
Record Date and before the opening of business at such Office or Agency on the
related proposed date for 

                                       39
<PAGE>
 
payment of Defaulted Interest, such Bearer Security shall be surrendered without
the Coupon relating to such Defaulted Interest and Defaulted Interest shall not
be payable on such proposed date of payment in respect of the Registered
Security issued in exchange for such Bearer Security, but shall be payable only
to the Holder of such Coupon when due in accordance with the provisions of this
Indenture.

     (2) The Company may make payment of any Defaulted Interest in any other
lawful manner not inconsistent with the requirements of any securities exchange
on which such Security may be listed, and upon such notice as may be required by
such exchange, if, after notice given by the Company to the Trustee of the
proposed payment pursuant to this clause, such manner of payment shall be deemed
practicable by the Trustee.

     (c) In the case of any Registered Security which is converted into Common
Stock pursuant to Article Twelve after any Regular Record Date and on or prior
to the next succeeding Interest Payment Date (other than any Registered Security
whose Maturity is prior to such Interest Payment Date), interest whose Stated
Maturity is on such Interest Payment Date shall be payable on such Interest
Payment Date notwithstanding such conversion, and such interest (whether or not
punctually paid or duly provided for) shall be paid to the Person in whose name
such Registered Security (or one or more Predecessor Securities) is registered
at the close of business on such Regular Record Date.  Except as otherwise
expressly provided in the immediately preceding sentence, in the case of any
Security which is converted pursuant to Article Twelve, accrued interest from
the immediately preceding Interest Payment Date until the Conversion Date shall
be payable to the converting Holder within five Business Days after the
Conversion Date.  Upon presentment for conversion of any Securities pursuant to
Article Twelve, the Paying Agent shall promptly notify the Company of the amount
of any accrued interest due and owing thereon and the Company shall pay to the
Paying Agent an amount sufficient to pay the accrued interest due on such
Securities and Additional Amounts, if any, thereon, and the Paying Agent shall
apply the amounts so paid to it to the payment of such accrued interest and
Additional Amounts, if any, thereon in accordance with the terms of the
Securities.

     (d) Subject to the foregoing provisions of this Section 307 and Section
305, each Security delivered under this Indenture upon registration of transfer
of or in exchange for or in lieu of any other Security shall carry the rights to
interest accrued and unpaid, and to accrue, which were carried by such other
Security.

Section 308.  Persons Deemed Owners.
              --------------------- 

     Title to any Bearer Security or Coupon shall pass by delivery.  The
Company, the Guarantor, the Trustee, the Paying Agent and any other agent of the
Company, the Guarantor, the Trustee or the Paying Agent may treat the bearer of
any Bearer Security or the temporary global Bearer Security and the bearer of
any Coupon as the absolute owner of such Security or Coupon, as the case may be,
for the purpose of receiving payment thereof or on account thereof and for all
other purposes whatsoever, whether or not such Security or Coupon be overdue,
and neither the Company, the Guarantor, the Trustee, the Paying Agent nor any
other agent of the Company, the Guarantor, the Trustee or the Paying Agent shall
be affected by notice to the contrary.

                                       40
<PAGE>
 
     Prior to due presentment of a Registered Security for registration of
transfer, the Company, the Guarantor, the Trustee and any agent of the Company,
the Guarantor or the Trustee shall treat the Person in whose name such
Registered Security is registered in the Security Register as the absolute owner
of such Registered Security for the purpose of receiving payment of principal
of, any premium and (subject to Sections 305 and 307) interest on and any
Additional Amounts with respect to such Registered Security and for all other
purposes whatsoever, whether or not any payment with respect to such Registered
Security shall be overdue, and neither the Company, the Guarantor, the Trustee
or any agent of the Company, the Guarantor or the Trustee shall be affected by
notice to the contrary.

     No holder of any beneficial interest in any global Security held on its
behalf by a Depository or Common Depository shall have any rights under this
Indenture with respect to such global Security, and such Depository or Common
Depository may be treated by the Company, the Guarantor, the Trustee, and any
agent of the Company, the Guarantor or the Trustee as the owner of such global
Security for all purposes whatsoever.  None of the Company, the Guarantor, the
Trustee, any Paying Agent, any Conversion Agent or the Security Registrar will
have any responsibility or liability for any aspect of the records relating to
or payments made on account of beneficial ownership interests of a global
Security or for maintaining, supervising or reviewing any records relating to
such beneficial ownership interests.

Section 309.  Cancellation.
              ------------ 

     All Securities and Coupons surrendered for payment, redemption,
registration of transfer, exchange or conversion or for credit against any
sinking fund payment shall, if surrendered to any Person other than the Trustee,
be delivered to the Trustee, and any such Securities and Coupons, as well as
Securities and Coupons surrendered directly to the Trustee for any such purpose,
shall be canceled promptly by the Trustee.  The Company or the Guarantor may at
any time deliver to the Trustee for cancellation any Securities or Coupons
previously authenticated and delivered hereunder which the Company or the
Guarantor may have acquired in any manner whatsoever, and all Securities or
Coupons so delivered shall be canceled promptly by the Trustee. No Securities or
Coupons shall be authenticated in lieu of or in exchange for any Securities or
Coupons canceled as provided in this Section 309, except as expressly permitted
by or pursuant to this Indenture.  All canceled Securities and Coupons held by
the Trustee shall be destroyed by the Trustee, unless by a Company Order the
Company directs their return to it.

Section 310.  Computation of Interest.
              ----------------------- 

     Except as otherwise provided in or pursuant to this Indenture or in the
Securities of any series, interest on the Securities shall be computed on the
basis of a 360-day year of twelve 30-day months.

Section 311.  CUSIP Numbers.
              ------------- 

     The Company in issuing Registered Securities may use "CUSIP" numbers (if
then generally in use) in addition to serial numbers, and in issuing Bearer
Securities may use "ISIN" 

                                       41
<PAGE>
 
numbers (if then generally in use); if so, the Trustee shall use such "CUSIP"
and "ISIN" numbers in addition to serial numbers in notices of redemption and
repayment as a convenience to Holders; provided that any such notice may state
                                       -------- ----
that no representation is made as to the correctness of such CUSIP and ISIN
numbers either as printed on the Securities or as contained in any notice of a
redemption or repayment and that reliance may be placed only on the serial or
other identification numbers printed on the Securities, and any such redemption
or repayment shall not be affected by any defect in or omission of such CUSIP or
ISIN numbers.

Section 312.  Notification of Withholding.
              --------------------------- 

     The Company shall notify the Trustee in writing of the necessity, if any,
to withhold any amounts from payments to Holders (and the amount of any such
withholding).


                                 ARTICLE FOUR


                    SATISFACTION AND DISCHARGE OF INDENTURE

Section 401.  Satisfaction and Discharge.
              -------------------------- 

     Upon the direction of the Company by a Company Order, this Indenture shall
cease to be of further effect with respect to any series of Securities specified
in such Company Order and any Coupons appertaining thereto (except as to any
surviving rights of conversion, or registration of transfer or exchange or
replacement of Securities herein expressly provided for and any right to receive
Additional Amounts and the Company's obligations to the Trustee pursuant to
Section 606), and the Trustee, on receipt of a Company Order, at the expense of
the Company, shall execute proper instruments acknowledging satisfaction and
discharge of this Indenture as to such series, when

     (1)  either

          (A) all Securities of such series theretofore authenticated and
     delivered and all Coupons appertaining thereto (other than (i) Coupons
     appertaining to Bearer Securities of such series surrendered in exchange
     for Registered Securities of such series and maturing after such exchange
     whose surrender is not required or has been waived as provided in Section
     305, (ii) Securities and Coupons of such series which have been destroyed,
     lost or stolen and which have been replaced or paid as provided in Section
     306, (iii) Coupons appertaining to Securities of such series called for
     redemption and maturing after the relevant Redemption Date whose surrender
     has been waived as provided in Section 1106, and (iv) Securities and
     Coupons of such series for whose payment money has theretofore been
     deposited in trust or segregated and held in trust by the Company or the
     Guarantor and thereafter repaid to the Company or the Guarantor or
     discharged from such trust, as provided in Section 1003) have been
     delivered to the Trustee for cancellation; or

                                       42
<PAGE>
 
          (B) all Securities of such series and any Coupons appertaining thereto
     not theretofore delivered to the Trustee or the Paying Agent for
     cancellation (other than Securities or Coupons referred to in clauses (i)
     through (iii) of clause (A) above)

          (i)    have become due and payable, or

          (ii)   will have become due and payable at their Stated Maturity
     within one year and such Securities are not convertible into or
     exchangeable for other securities, or

          (iii)  if redeemable at the option of the Company, such Securities are
     not convertible into or exchangeable for other securities and are to be
     called for redemption within one year under arrangements satisfactory to
     the Trustee for the giving of notice of redemption by the Trustee in the
     name, and at the expense, of the Company,

     and the Company or the Guarantor, in the case of (i), (ii), or (iii) above,
     has irrevocably deposited or caused to be deposited with the Trustee as
     trust funds (immediately available to the Holders in the case of clause (i)
     above) in trust for such purpose, money in the Currency in which such
     Securities are payable in an amount sufficient to pay and discharge the
     entire indebtedness on such Securities and any Coupons appertaining thereto
     not theretofore delivered to the Trustee for cancellation, including the
     principal of, any premium and interest on, and, to the extent that the
     Securities of such series provide for the payment of Additional Amounts
     thereon and the amount of any such Additional Amounts is at the time of
     deposit reasonably determinable by the Company (in the exercise by the
     Company of its sole and absolute discretion), any Additional Amounts with
     respect to such Securities and any Coupons appertaining thereto, to the
     date of such deposit (in the case of Securities which have become due and
     payable) or to the Maturity thereof, as the case may be;

     (2)  the Company or the Guarantor, as the case may be, has paid or caused
     to be paid all other sums payable hereunder by the Company or the Guarantor
     with respect to the Outstanding Securities of such series and any Coupons
     appertaining thereto; and

     (3)  the Company has delivered to the Trustee an Officers' Certificate and
     an Opinion of Counsel, each stating that all conditions precedent herein
     provided for relating to the satisfaction and discharge of this Indenture
     as to such series have been complied with.

     In the event there are Securities of two or more series hereunder, the
Trustee shall be required to execute an instrument acknowledging satisfaction
and discharge of this Indenture only if requested to do so with respect to
Securities of such series as to which it is Trustee and if the other conditions
thereto are met.

     Notwithstanding the satisfaction and discharge of this Indenture with
respect to any series of Securities, the obligations of the Company and the
Guarantor to the Trustee under Section 606, the obligations of the Company and
the Guarantor to any Authenticating Agent under Section 612, and, if money shall
have been deposited with the Trustee pursuant to clause (1)(B) of this Section,
the obligations of the Company, the Guarantor and the Trustee with

                                       43
<PAGE>
 
respect to the Securities of such series under Sections 305, 306, 403, 1002 and
1003, and with respect to the payment of Additional Amounts, if any, with
respect to such Securities as contemplated by Section 1004 (but only to the
extent that the Additional Amounts payable with respect to such Securities
exceed the amount deposited in respect of such Additional Amounts pursuant to
Section 401(B)), shall survive.

Section 402.  Defeasance and Covenant Defeasance.
              ---------------------------------- 

     (1) Unless, pursuant to Section 301, provision is made for either or both
of (i) defeasance of the Securities of or within a series under clause (2) of
this Section 402 or (ii) covenant defeasance of the Securities of or within a
series under clause (3) of this Section 402, such provisions, together with the
other provisions of this Section 402, shall not be applicable to such Securities
and any Coupons appertaining thereto.

     (2) Upon the Company's exercise of the above option applicable to this
Section 402(2) with respect to any Securities of or within a series, the Company
and the Guarantor shall be deemed to have been discharged from their respective
obligations with respect to such Outstanding Securities and any Coupons
appertaining thereto, and with respect to the corresponding Guarantees on the
date the conditions set forth in clause (4) of this Section 402 are satisfied
(hereinafter, "defeasance").  For this purpose, such defeasance means that the
               ----------                                                     
Company and the Guarantor shall be deemed to have paid and discharged the entire
indebtedness represented by such Outstanding Securities and Guarantees and any
Coupons appertaining thereto, which shall thereafter be deemed to be
"Outstanding" only for the purposes of clause (5) of this Section 402 and the
other Sections of this Indenture referred to in clauses (i) and (ii) below, and
to have satisfied all of its other obligations under such Securities and any
Coupons appertaining thereto and under such corresponding Guarantees and this
Indenture insofar as such Securities and any Coupons appertaining thereto and
such Guarantees are concerned (and the Trustee, at the expense of the Company,
shall execute proper instruments acknowledging the same), except for the
following which shall survive until otherwise terminated or discharged
hereunder: (i) the rights of Holders of such Outstanding Securities and
Guarantees and any Coupons appertaining thereto to receive, solely from the
trust fund described in clause (4) of this Section 402 and as more fully set
forth in such Section, payments in respect of the principal of (and premium, if
any) and interest, if any, on, and Additional Amounts, if any, with respect to,
such Securities and Guarantees and any Coupons appertaining thereto when such
payments are due, (ii) the obligations of the Company and the Trustee with
respect to such Securities under Sections 304, 305, 306, 403, 1002 and 1003,
with respect to the payment of Additional Amounts, if any, on such Securities as
contemplated by Section 1004 (but only to the extent that the Additional Amounts
payable with respect to such Securities exceed the amount deposited in respect
of such Additional Amounts pursuant to Section 402(4)(a) below), and any
obligation of the Guarantor relating to a surviving obligation of the Company,
(iii) the rights, powers, trusts, duties and immunities of the Trustee
hereunder, (iv) any rights of conversion or exchange of such Securities and (v)
this Section 402.  The Company may exercise its option under this Section 402(2)
notwithstanding the prior exercise of its option under clause (3) of this
Section 402 with respect to such Securities and any Coupons appertaining
thereto.

                                       44
<PAGE>
 
     (3) Upon the Company's exercise of the above option applicable to this
Section 402(3) with respect to any Securities of or within a series, the Company
and the Guarantor, as the case may be, shall be released from its obligations
under Sections 1005 and Section 102 and, to the extent specified pursuant to
Section 301, any other covenant applicable to such Securities, with respect to
such Outstanding Securities and any Coupons appertaining thereto on and after
the date the conditions set forth in clause (4) of this Section 402 are
satisfied (hereinafter, "covenant defeasance"), and such Securities and any
                         -------------------                               
Coupons appertaining thereto shall thereafter be deemed to be not "Outstanding"
for the purposes of any direction, waiver, consent or declaration or Act of
Holders (and the consequences of any thereof) in connection with any such
covenant, but shall continue to be deemed "Outstanding" for all other purposes
hereunder.  For this purpose, such covenant defeasance means that, with respect
to such Outstanding Securities and any Coupons appertaining thereto, the Company
and the Guarantor may omit to comply with, and shall have no liability in
respect of, any term, condition or limitation set forth in any such Section or
such other covenant, whether directly or indirectly, by reason of any reference
elsewhere herein to any such Section or such other covenant or by reason of
reference in any such Section or such other covenant to any other provision
herein or in any other document and such omission to comply shall not constitute
a default or an Event of Default under Section 501(4) or otherwise, as the case
may be, but, except as specified above, the remainder of this Indenture and such
Securities and Coupons appertaining thereto, and the Guarantees endorsed
thereon, shall be unaffected thereby.

     (4) The following shall be the conditions to application of clause (2) or
(3) of this Section 402 to any Outstanding Securities of or within a series and
any Coupons appertaining thereto, or to any Guarantees endorsed thereon:

     (a) The Company shall irrevocably have deposited or caused to be deposited
with the Trustee (or another trustee satisfying the requirements of Section 607
who shall agree to comply with the provisions of this Section 402 applicable to
it) as trust funds in trust for the purpose of making the following payments,
specifically pledged as security for, and dedicated solely to, the benefit of
the Holders of such Securities and any Coupons appertaining thereto, (i) an
amount in Dollars, or (ii) Government Obligations applicable to such Securities
and Coupons appertaining thereto (determined on the basis of the Currency in
which such Securities and Coupons appertaining thereto are then specified as
payable at Stated Maturity) which through the scheduled payment of principal and
interest in respect thereof in accordance with their terms will provide, not
later than one day before the due date of any payment of principal of (and
premium, if any) and interest, if any, on such Securities and any Coupons
appertaining thereto, money in an amount, or (iii) a combination thereof, in any
case, in an amount, sufficient, without consideration of any reinvestment of
such principal and interest, in the opinion of a nationally recognized firm of
independent public accountants expressed in a written certification thereof
delivered to the Trustee, to pay and discharge, and which shall be applied by
the Trustee (or other qualifying trustee) to pay and discharge, (y) the
principal of (and premium, if any) and interest, if any, on, and, to the extent
that such Securities provide for the payment of Additional Amounts thereon and
the amount of any such Additional Amounts is at the time of deposit reasonably
determinable by the Company, any Additional Amounts with respect to, such
Outstanding Securities and any Coupons appertaining thereto on the Stated
Maturity of such principal or installment of principal or interest and (z) any
mandatory sinking fund payments or analogous 

                                       45
<PAGE>
 
payments applicable to such Outstanding Securities and any Coupons appertaining
thereto on the day on which such payments are due and payable in accordance with
the terms of this Indenture and of such Securities and any Coupons appertaining
thereto.

     (b) Such defeasance or covenant defeasance shall not result in a breach or
violation of, or constitute a default under, this Indenture or any other
material agreement or instrument to which the Company or the Guarantor is a
party or by which it is bound.
 
     (c) No Default or Event of Default with respect to such Securities and any
Coupons appertaining thereto shall have occurred and be continuing on the date
of such deposit and, with respect to defeasance only, at any time during the
period ending on the 91st day after the date of such deposit (it being
understood that this condition shall not be deemed satisfied until the
expiration of such period).

     (d) In the case of an election under clause (2) of this Section 402, the
Company shall have delivered to the Trustee an Opinion of Counsel stating that
(i) the Company has received from the Internal Revenue Service a letter ruling,
or there has been published by the Internal Revenue Service a revenue ruling, or
(ii) since the date of execution of this Indenture, there has been a change in
the applicable Federal income tax law, in either case to the effect that, and
based thereon such opinion shall confirm that, the Holders of such Outstanding
Securities and any Coupons appertaining thereto will not recognize income, gain
or loss for Federal income tax purposes as a result of such defeasance and will
be subject to Federal income tax on the same amounts, in the same manner and at
the same times as would have been the case if such defeasance had not occurred.

     (e) In the case of an election under clause (3) of this Section 402, the
Company and the Guarantor shall have delivered to the Trustee an Opinion of
Counsel to the effect that the Holders of such Outstanding Securities and any
Coupons appertaining thereto will not recognize income, gain or loss for Federal
income tax purposes as a result of such covenant defeasance and will be subject
to Federal income tax on the same amounts, in the same manner and at the same
times as would have been the case if such covenant defeasance had not occurred.

     (f) The Company and the Guarantor shall have delivered to the Trustee an
Officers' Certificate and an Opinion of Counsel, each stating that all
conditions precedent to the defeasance or covenant defeasance under clause (2)
or (3) of this Section 402 (as the case may be) have been complied with.

     (g) Each of the Company and the Guarantor shall have delivered to the
Trustee an Officers' Certificate to the effect that neither such Securities nor
any other Securities of the same series, if then listed on any securities
exchange, will be delisted as a result of such deposit.

     (h) Such defeasance or covenant defeasance shall not cause the Trustee to
have a conflicting interest within the meaning of the Trust Indenture Act
(assuming all Securities are in default within the meaning of such Act).

                                       46
<PAGE>
 
     (i) Such defeasance or covenant defeasance shall not result in the trust
arising from such deposit constituting an investment company within the meaning
of the Investment Company Act unless such trust shall be registered under such
Act or exempt from registration thereunder.

     (j) Notwithstanding any other provisions of this Section 402(4), such
defeasance or covenant defeasance shall be effected in compliance with any
additional or substitute terms, conditions or limitations which may be imposed
on the Company or the Guarantor in connection therewith pursuant to Section 301.

     (5) Subject to the provisions of the last paragraph of Section 1003, all
money and Government Obligations (or other property as may be provided pursuant
to Section 301) (including the proceeds thereof) deposited with the Trustee (or
other qualifying trustee-- collectively for purposes of this Section 402(5) and
Section 403, the "Trustee") pursuant to clause (4) of Section 402 in respect of
                  -------                                                      
any Outstanding Securities of any series and any Coupons appertaining thereto
shall be held in trust and applied by the Trustee, in accordance with the
provisions of such Securities and any Coupons appertaining thereto and this
Indenture, to the payment, either directly or through any Paying Agent
(including the Company acting as its own Paying Agent) as the Trustee may
determine, to the Holders of such Securities and any Coupons appertaining
thereto of all sums due and to become due thereon in respect of principal (and
premium, if any) and interest and Additional Amounts, if any, but such money
need not be segregated from other funds except to the extent required by law.

     The Company and the Guarantor shall pay and indemnify the Trustee and its
officers, directors, employees and agents against any tax, fee or other charge,
imposed on or assessed against the Government Obligations deposited pursuant to
this Section 402 or the principal or interest received in respect thereof other
than any such tax, fee or other charge which by law is for the account of the
Holders of such Outstanding Securities and any Coupons appertaining thereto.

     Anything in this Section 402 to the contrary notwithstanding, the Trustee
shall deliver or pay to the Company from time to time upon Company Request any
money or Government Obligations (or other property and any proceeds therefrom)
held by it as provided in clause (4) of this Section 402 which, in the opinion
of a nationally recognized firm of independent public accountants expressed in a
written certification thereof delivered to the Trustee, are in excess of the
amount thereof which would then be required to be deposited to effect a
defeasance or covenant defeasance, as applicable, in accordance with this
Section 402.

Section 403.  Application of Trust Money.
              -------------------------- 

     Subject to the provisions of the last paragraph of Section 1003, all money
and Government Obligations deposited with the Trustee pursuant to Section 401 or
402 shall be held in trust and applied by it, in accordance with the provisions
of the Securities, the Coupons appertaining thereto, the Guarantees and this
Indenture, as applicable, to the payment, either directly or through any Paying
Agent (including the Company or the Guarantor acting as its own Paying Agent) as
the Trustee may determine, to the Persons entitled thereto, of the principal,

                                       47
<PAGE>
 
premium, interest and Additional Amounts for whose payment such money has or
Government Obligations have been deposited with or received by the Trustee; but
such money and Government Obligations need not be segregated from other funds
except to the extent required by law.



                                 ARTICLE FIVE


                                   REMEDIES



Section 501.  Events of Default.
              ----------------- 

     "Event of Default," wherever used herein with respect to Securities of any
      ----------------                                                         
series, means any one of the following events (whatever the reason for such
Event of Default and whether it shall be voluntary or involuntary or be effected
by operation of law or pursuant to any judgment, decree or order of any court or
any order, rule or regulation of any administrative or governmental body) unless
such event is specifically deleted or modified in or pursuant to the
supplemental indenture, Company and Guarantor Board Resolutions or Company and
Guarantor Officers' Certificate establishing the terms of such series pursuant
to this Indenture:

     (1) default in the payment of any interest on, or any Additional Amounts
payable in respect of any interest on, any Security of such series when such
interest or such Additional Amounts, as the case may be, become due and payable,
and continuance of such default for a period of 10 days, whether or not such
payment is prohibited by the subordination provisions of Article Seventeen or
Article Eighteen; or

     (2) default in the payment of the principal of or premium, if any, on, or
any Additional Amounts payable in respect of the principal of or premium, if
any, on any Security of such series when due upon Maturity (whether upon
redemption or otherwise), whether or not such payment is prohibited by the
subordination provisions of Article Seventeen or Article Eighteen; or

     (3) default in the payment of any sinking fund payment, or analogous
payment, when and as due by the terms of a Security of such series, whether or
not such payment is prohibited by the subordination provisions of Article
Seventeen or Article Eighteen; or

     (4) default in the performance, or breach, of any covenant or warranty of
the Company or the Guarantor in this Indenture or any Security of such series
(other than a covenant or warranty for which the consequences of breach or
nonperformance are addressed elsewhere in this Section 501 or in the Securities
or in a covenant or warranty which has expressly been included in this Indenture
or a Security of that series, whether or not by means of a supplemental
Indenture, solely for the benefit of Securities of a series other than such
series), and continuance of such default or breach for a period of 60 days after
there has been given, by registered or certified mail, to the Company and the
Guarantor by the Trustee or to the Company, the Guarantor and the Trustee by the
Holders of at least 25% in principal amount of the Outstanding 

                                       48
<PAGE>
 
Securities of such series a written notice specifying such default or breach and
requiring it to be remedied and stating that such notice is a "Notice of
Default" hereunder; or

     (5) the Company or the Guarantor pursuant to or under or within the meaning
of any Bankruptcy Law:

          (a) commences a voluntary case or proceeding;

          (b) consents to the entry of an order for relief against it in an
     involuntary case or proceeding or the commencement of any case against it;

          (c) consents to the appointment of a Custodian of it or for any
     substantial part of its property;

          (d) makes a general assignment for the benefit of its creditors;

          (e) files a petition in bankruptcy or answer or consent seeking
     reorganization or relief; or

          (f) consents to the filing of such petition or the appointment of or
     taking possession by a Custodian; or

     (6)  a court of competent jurisdiction enters an order or decree under any
Bankruptcy Law that:

          (a) is for relief against the Company or the Guarantor in an
     involuntary case or proceeding, or adjudicates the Company or the Guarantor
     insolvent or bankrupt;

          (b) appoints a Custodian of the Company or the Guarantor or for any
     substantial part of their respective property; or

          (c) orders the winding up or liquidation of the Company or the
     Guarantor;

          and the order or decree remains unstayed and in effect for 60
     consecutive days; or

     (7)  a default by the Company (including a default with respect to
Securities of any series other than that series) under any indenture, including
this Indenture, or instrument evidencing, or under which the Company has at the
date of this Indenture or shall hereafter have, any indebtedness for money
borrowed with a principal amount then outstanding in excess of $25,000,000 or
such other amount as may be specified in the Company's Board Resolutions or
Officers' Certificate establishing the series (or the equivalent in any other
currency) shall happen and be continuing and such indebtedness shall have been
accelerated so that the same shall be or become due and payable prior to the
date on which the same would otherwise have become due and payable, or a default
in payment of such indebtedness at its stated maturity shall have occurred, and
such indebtedness shall not have been discharged or such acceleration shall not
be rescinded or annulled within 20 days after written notice thereof shall have
been given, by 

                                       49
<PAGE>
 
registered or certified mail, to the Company and the Guarantor by the Trustee,
or to the Company, the Guarantor and the Trustee by the Holders of at least 25%
in aggregate principal amount of the Outstanding Securities of that series;
provided, however, that if such default under such indenture or instrument shall
- --------  -------
be remedied or cured by the Company or waived by the holders of such
indebtedness, then the Event of Default hereunder by reason thereof shall be
deemed likewise to have been thereupon remedied, cured or waived without further
action upon the part of either the Trustee or any of the Holders; provided,
                                                                  --------
further, however, that subject to the provisions of Section 601, the Trustee
- -------    
will not be considered to have knowledge of any default by the Company under
this Section 501 unless the Trustee shall have received written or actual notice
of such default; or

     (8) any other Event of Default provided in or pursuant to this Indenture
with respect to Securities of such series.

     "Bankruptcy Law" means Title 11, United States Code, or any similar Federal
      --------------                                                            
or state law for the relief of debtors.  "Custodian" means any receiver,
                                          ---------                     
trustee, assignee, liquidator, sequestrator, custodian or similar official under
any Bankruptcy Law.

Section 502.  Acceleration of Maturity; Rescission and Annulment.
              -------------------------------------------------- 

     If an Event of Default with respect to Securities of any series at the time
Outstanding occurs and is continuing throughout the period permitted under this
Indenture or any supplemental indenture to cure such default, then the Trustee
or the Holders of not less than 25% in principal amount of the Outstanding
Securities of such series may declare the principal (or, if any Securities are
Original Issue Discount Securities or Indexed Securities, such portion of the
principal as may be specified in the terms thereof) of all the Securities of
such series, or such lesser amount as may be provided for in the Securities of
such series, to be due and payable immediately, by a notice in writing to the
Company and the Guarantor (and to the Trustee if given by the Holders), and upon
any such declaration such principal or such lesser amount shall become
immediately due and payable.

     Notwithstanding any other provision of this Section 502, if an Event of
Default specified in Section 501(5) or 501(6) occurs, all principal of, any
premium and interest on, and any Additional Amounts on the Securities then
Outstanding shall be immediately due and payable without any declaration or
other act on the part of the Trustee or the Holders.

     At any time after Securities of any series have been accelerated and before
a judgment or decree for payment of the money due has been obtained by the
Trustee as hereinafter in this Article Five provided, the Holders of not less
than a majority in principal amount of the Outstanding Securities of such
series, by written notice to the Company, the Guarantor and the Trustee, may
rescind and annul such declaration and its consequences if:

     (1) the Company or the Guarantor has paid or deposited with the Trustee a
sum of money sufficient to pay

                                       50
<PAGE>
 
     (a) all overdue installments of any interest on any Securities of such
series and any Coupons appertaining thereto and any Additional Amounts with
respect thereto,

     (b) the principal of and any premium on any Securities of such series which
have become due otherwise than by such declaration of acceleration and any
Additional Amounts with respect thereto and, to the extent the payment of such
interest is lawful, interest thereon at the rate or rates borne by or provided
for in such Securities,

     (c) to the extent that payment of such interest is lawful, interest upon
overdue installments of any interest and any Additional Amounts with respect
thereto at the rate or rates borne by or provided for in such Securities, and

     (d) all sums paid or advanced by the Trustee hereunder and the reasonable
compensation, expenses, disbursements and advances of the Trustee, its agents
and counsel and all other amounts due the Trustee under Section 606; and

     (2)  all Events of Default with respect to Securities of such series, other
than the non-payment of the principal of, any premium and interest on, and any
Additional Amounts with respect to Securities of such series which shall have
become due solely by such declaration of acceleration, shall have been cured or
waived as provided in Section 513.

     No such rescission shall affect any subsequent default or impair any right
consequent thereon.

Section 503.  Collection of Indebtedness and Suits for Enforcement by Trustee.
              --------------------------------------------------------------- 

     The Company covenants that if

     (1) default is made in the payment of any installment of interest on or any
Additional Amounts with respect to any Security or any Coupon appertaining
thereto when such interest or Additional Amounts shall have become due and
payable and such default continues for a period of 10 days, or

     (2) default is made in the payment of the principal of or any premium on
any Security at its Maturity,

the Company shall, upon demand of the Trustee, pay to the Trustee, for the
benefit of the Holders of such Securities and any Coupons appertaining thereto,
the whole amount of money then due and payable with respect to such Securities
and any Coupons appertaining thereto, with interest upon the overdue principal,
any premium and, to the extent that payment of such interest shall be legally
enforceable, upon any overdue installments of interest and Additional Amounts at
the rate or rates borne by or provided for in such Securities, and, in addition
thereto, such further amount of money as shall be sufficient to cover the costs
and expenses of collection, including the reasonable compensation, expenses,
disbursements and advances of the Trustee, its agents and counsel and all other
amounts due to the Trustee under Section 606.

                                      51
<PAGE>
 
     If the Company fails to pay the money it is required to pay the Trustee
pursuant to the preceding paragraph, forthwith upon the demand of the Trustee,
the Trustee, in its own name and as trustee of an express trust, may institute a
judicial proceeding for the collection of the money so due and unpaid, and may
prosecute such proceeding to judgment or final decree, and may enforce the same
against the Company, the Guarantor or any other obligor upon such Securities and
any Coupons appertaining thereto and collect the monies adjudged or decreed to
be payable in the manner provided by law out of the property of the Company, the
Guarantor or any other obligor upon such Securities and any Coupons appertaining
thereto, wherever situated.

     If an Event of Default with respect to Securities of any series occurs and
is continuing, the Trustee may in its discretion proceed to protect and enforce
its rights and the rights of the Holders of Securities of such series and any
Coupons appertaining thereto by such appropriate judicial proceedings as the
Trustee shall deem most effectual to protect and enforce any such rights,
whether for the specific enforcement of any covenant or agreement in this
Indenture or such Securities or in aid of the exercise of any power granted
herein or therein, or to enforce any other proper remedy.

Section 504.  Trustee May File Proofs of Claim.
              --------------------------------     

     In case of the pendency of any receivership, insolvency, liquidation,
bankruptcy, reorganization, arrangement, adjustment, composition or other
judicial proceeding relative to the Company, the Guarantor or any other obligor
upon the Securities or the property of the Company, the Guarantor, or such other
obligor or their creditors, the Trustee (irrespective of whether the principal
of the Securities shall then be due and payable as therein expressed or by
declaration or otherwise and irrespective of whether the Trustee shall have made
any demand on the Company or the Guarantor for the payment of any overdue
principal, premium, interest or Additional Amounts) shall be entitled and
empowered, by intervention in such proceeding or otherwise, to take any and all
actions authorized under the Trust Indenture Act in order to have claims of the
Holders and the Trustee allowed in any such proceeding, including:

     (1)  to file and prove a claim for the whole amount, or such lesser amount
as may be provided for in the Securities of such series, of the principal and
any premium, interest and Additional Amounts owing and unpaid in respect of the
Securities and any Coupons appertaining thereto and to file such other papers or
documents as may be necessary or advisable in order to have the claims of the
Trustee (including any claim for the reasonable compensation, expenses,
disbursements and advances of the Trustee, its agents or counsel) and of the
Holders of Securities or any Coupons allowed in such judicial proceeding, and

     (2)  to collect and receive any monies or other property payable or
deliverable on any such claims and to distribute the same;

and any custodian, receiver, assignee, trustee, liquidator, sequestrator or
other similar official in any such judicial proceeding is hereby authorized by
each Holder of Securities or any Coupons to make such payments to the Trustee
and, in the event that the Trustee shall consent to the making of such payments
directly to the Holders of Securities or any Coupons, to pay to the Trustee any
amount due to it for the reasonable compensation, expenses, disbursements and

                                       52
<PAGE>
 
advances of the Trustee, its agents and counsel and any other amounts due the
Trustee under Section 606.

     Nothing herein contained shall be deemed to authorize the Trustee to
authorize or consent to or accept or adopt on behalf of any Holder of a Security
or any Coupon any plan of reorganization, arrangement, adjustment or composition
affecting the Securities or Coupons or the rights of any Holder thereof, or to
authorize the Trustee to vote in respect of the claim of any Holder of a
Security or any Coupon in any such proceeding; provided, however, that the
                                               --------  -------          
Trustee may, on behalf of the Holders of Securities or any Coupons, vote for the
election of a trustee in bankruptcy or similar official and be a member of a
creditors or other similar committee.

Section 505.  Trustee May Enforce Claims Without Possession of Securities or
              --------------------------------------------------------------
Coupons.
- -------     

     All rights of action and claims under this Indenture or any of the
Securities or Coupons may be prosecuted and enforced by the Trustee without the
possession of any of the Securities or Coupons or the production thereof in any
proceeding relating thereto, and any such proceeding instituted by the Trustee
shall be brought in its own name as trustee of an express trust, and any
recovery or judgment, after provision for the payment of the reasonable
compensation, expenses, disbursements and advances of the Trustee, its agents
and counsel, shall be for the ratable benefit of each and every Holder of a
Security or Coupon in respect of which such judgment has been recovered.

Section 506.  Application of Money Collected.
              ------------------------------     

     Subject to Articles Seventeen and Eighteen, any money collected by the
Trustee pursuant to this Article Five shall be applied in the following order,
at the date or dates fixed by the Trustee and, in case of the distribution of
such money on account of principal, or any premium, interest or Additional
Amounts, upon presentation of the Securities or Coupons, or both, as the case
may be, and the notation thereon of the payment if only partially paid and upon
surrender thereof if fully paid:

     FIRST: To the payment of all amounts due the Trustee and any predecessor
Trustee under Section 606;

     SECOND: To the payment of the amounts then due and unpaid upon the
Securities and any Coupons for principal and any premium, interest and
Additional Amounts in respect of which or for the benefit of which such money
has been collected, ratably, without preference or priority of any kind,
according to the aggregate amounts due and payable on such Securities and
Coupons for principal and any premium, interest and Additional Amounts,
respectively;

     THIRD: The balance, if any, to the Person or Persons entitled thereto.

Section 507.  Limitations on Suits.
              --------------------     

     No Holder of any Security of any series or any Coupons appertaining thereto
shall have any right to institute any proceeding, judicial or otherwise, with
respect to this Indenture, the 

                                       53
<PAGE>
 
Guarantees, the Securities of any series or any Coupons appertaining thereto, or
for the appointment of a receiver or trustee, or for any other remedy hereunder,
unless:

     (1)  such Holder has previously given written notice to the Trustee of a
continuing Event of Default with respect to the Securities of such series;

     (2)  the Holders of not less than 25% in principal amount of the
Outstanding Securities of such series shall have made written request to the
Trustee to institute proceedings in respect of such Event of Default in its own
name as Trustee hereunder;

     (3)  such Holder or Holders have offered to the Trustee reasonable
indemnity against the costs, expenses and liabilities to be incurred in
compliance with such request;

     (4)  the Trustee for 60 days after its receipt of such notice, request and
offer of indemnity has failed to institute any such proceeding; and

     (5)  no direction inconsistent with such written request has been given to
the Trustee during such 60-day period by the Holders of a majority in principal
amount of the Outstanding Securities of such series;

it being understood and intended that no one or more of such Holders shall have
any right in any manner whatever by virtue of, or by availing of, any provision
of this Indenture or any Security to affect, disturb or prejudice the rights of
any other such Holders or Holders of Securities of any other series, or to
obtain or to seek to obtain priority or preference over any other Holders or to
enforce any right under this Indenture, except in the manner herein provided and
for the equal and ratable benefit of all such Holders.

Section 508.  Unconditional Right of Holders to Receive Principal and Any
              -----------------------------------------------------------
Premium, Interest and Additional Amounts.
- ----------------------------------------     

     Notwithstanding any other provision in this Indenture, the Holder of any
Security or Coupon shall have the right, which is absolute and unconditional, to
receive payment of the principal of, any premium and (subject to Section 307)
interest on, and any Additional Amounts with respect to such Security or such
Coupon, as the case may be, on the respective Stated Maturity or Maturities
therefor specified in such Security or Coupon (or, in the case of redemption, on
the Redemption Date or, in the case of repayment at the option of such Holder if
provided in or pursuant to this Indenture, on the Repayment Date) and to convert
such Security in accordance with Article Twelve (if conversion is permitted by
the terms of such Security), and to institute suit for the enforcement of any
such payment and right to convert, and such rights shall not be impaired without
the consent of such Holder.

Section 509.  Restoration of Rights and Remedies.
              ----------------------------------     

     If the Trustee or any Holder of a Security or a Coupon has instituted any
proceeding to enforce any right or remedy under this Indenture and such
proceeding has been discontinued or abandoned for any reason, or has been
determined adversely to the Trustee or to such Holder, 

                                       54
<PAGE>
 
then and in every such case the Company, the Guarantor, the Trustee and each
such Holder shall, subject to any determination in such proceeding, be restored
severally and respectively to their former positions hereunder, and thereafter
all rights and remedies of the Trustee and each such Holder shall continue as
though no such proceeding had been instituted.

Section 510.  Rights and Remedies Cumulative.
              ------------------------------     

     Except as otherwise provided with respect to the replacement or payment of
mutilated, destroyed, lost or stolen Securities or Coupons in the last paragraph
of Section 306, no right or remedy herein conferred upon or reserved to the
Trustee or to each and every Holder of a Security or a Coupon is intended to be
exclusive of any other right or remedy, and every right and remedy, to the
extent permitted by law, shall be cumulative and in addition to every other
right and remedy given hereunder or now or hereafter existing at law or in
equity or otherwise.  The assertion or employment of any right or remedy
hereunder, or otherwise, shall not, to the extent permitted by law, prevent the
concurrent assertion or employment of any other appropriate right or remedy.

Section 511.  Delay or Omission not Waiver.
              ----------------------------     

     No delay or omission of the Trustee or of any Holder of any Security or
Coupon to exercise any right or remedy accruing upon any Event of Default shall
impair any such right or remedy or constitute a waiver of any such Event of
Default or an acquiescence therein.  Every right and remedy given by this
Article Five or by law to the Trustee or to any Holder of a Security or a Coupon
may be exercised from time to time, and as often as may be deemed expedient, by
the Trustee or (subject to the limitations contained in this Indenture) by such
Holder, as the case may be.

Section 512.  Control by Holders of Securities.
              --------------------------------     

     The Holders of a majority in principal amount of the Outstanding Securities
of any series shall have the right to direct the time, method and place of
conducting any proceeding for any remedy available to the Trustee or exercising
any trust or power conferred on the Trustee with respect to the Securities of
such series and any Coupons appertaining thereto, provided that
                                                  -------- ----

     (1)  such direction shall not be in conflict with any rule of law or with
this Indenture or with the Securities of such series,

     (2)  the Trustee may take any other action deemed proper by the Trustee
which is not inconsistent with such direction, and

     (3)  such Holders have offered the Trustee an indemnity reasonably
satisfactory to it against any loss, cost, liability or expense that might been
incurred by the Trustee in following such direction.

                                       55
<PAGE>
 
Section 513.  Waiver of Past Defaults.
              -----------------------     

     The Holders of not less than a majority in principal amount of the
Outstanding Securities of any series on behalf of the Holders of all the
Securities of such series and any Coupons appertaining thereto may waive any
past default hereunder with respect to such series and its consequences, except
a default

     (1)  in the payment of the principal of, any premium or interest on, or
any Additional Amounts with respect to, any Security of such series or any
Coupons appertaining thereto, or

     (2)  in respect of a covenant or provision hereof which under Article Nine
cannot be modified or amended without the consent of the Holder of each
Outstanding Security of such series affected.

     Upon any such waiver, such default shall cease to exist, and any Event of
Default arising therefrom shall be deemed to have been cured, for every purpose
of this Indenture; but no such waiver shall extend to any subsequent or other
default or impair any right consequent thereon.

Section 514.  Waiver of Usury, Stay or Extension Laws.
              ---------------------------------------     

     Each of the Company and the Guarantor covenants that (to the extent that it
may lawfully do so) it will not at any time insist upon, or plead, or in any
manner whatsoever claim or take the benefit or advantage of, any usury, stay or
extension law wherever enacted, now or at any time hereafter in force, which may
affect the covenants or the performance of this Indenture; and each of the
Company and the Guarantor expressly waives (to the extent that it may lawfully
do so) all benefit or advantage of any such law and covenants that it will not
hinder, delay or impede the execution of any power herein granted to the
Trustee, but will suffer and permit the execution of every such power as though
no such law had been enacted.

Section 515.  Undertaking for Costs.
              ---------------------     

     All parties to this Indenture agree, and each Holder of any Security by his
acceptance thereof shall be deemed to have agreed, that any court may in its
discretion require, in any suit for the enforcement of any right or remedy under
this Indenture, or in any suit against the Trustee for any action taken or
omitted by it as Trustee, the filing by any party litigant in such suit of any
undertaking to pay the costs of such suit, and that such court may in its
discretion assess reasonable costs, including reasonable attorneys' fees,
against any party litigant in such suit having due regard to the merits and good
faith of the claims or defenses made by such party litigant; but the provisions
of this Section 515 shall not apply to any suit instituted by the Trustee, to
any suit instituted by any Holder, or group of Holders, holding in the aggregate
more than 10% in principal amount of Outstanding Securities of any series, or to
any suit instituted by any Holder for the enforcement of the payment of the
principal of (or premium, if any) or interest, if any, on or Additional Amounts,
if any, with respect to any Security on or after the respective Stated
Maturities expressed in such Security (or, in the case of redemption, on or
after the Redemption Date, and, in the case of repayment, on or after the date
for repayment) or for the enforcement of the right to convert any Security in
accordance with Article Twelve.

                                       56
<PAGE>
 
                                  ARTICLE SIX

                                  THE TRUSTEE

Section 601.  Certain Rights of Trustee; Certain Duties and Responsibilities.
              ---------------------------------------------------------------

     Subject to Sections 315(a) through 315(d) of the Trust Indenture Act:

     (1)  the Trustee may conclusively rely and shall be fully protected in
acting or refraining from acting upon any resolution, certificate, statement,
instrument, opinion, report, notice, request, direction, consent, order, bond,
debenture, note, coupon, other evidence of indebtedness or other paper or
document reasonably believed by it to be genuine and to have been signed or
presented by the proper party or parties;

     (2)  any request or direction of the Company or the Guarantor mentioned
herein shall be sufficiently evidenced by a Company Request or a Company Order
or Guarantor Request or Guarantor Order, as the case may be (in each case, other
than delivery of any Security, together with any Coupons appertaining thereto,
to the Trustee for authentication and delivery pursuant to Section 303 which
shall be sufficiently evidenced as provided therein) and any resolution of the
Board of Directors of the Company or the Guarantor, as the case may be, shall be
sufficiently evidenced by a Board Resolution of the Company or the Guarantor, as
the case may be;

     (3)  whenever in the administration of this Indenture the Trustee shall
deem it desirable that a matter be proved or established prior to taking,
suffering or omitting any action hereunder, the Trustee (unless other evidence
shall be herein specifically prescribed) may, in the absence of bad faith on its
part, rely upon an Officers' Certificate;

     (4)  the Trustee may consult with counsel of its selection and the advice
of such counsel or any Opinion of Counsel shall be full and complete
authorization and protection in respect of any action taken, suffered or omitted
by it hereunder in good faith and in reliance thereon;

     (5)  the Trustee shall be under no obligation to exercise any of the rights
or powers vested in it by or pursuant to this Indenture at the request or
direction of any of the Holders of Securities of any series or any Coupons
appertaining thereto pursuant to this Indenture, unless such Holders shall have
offered to the Trustee reasonable security or indemnity against the costs,
expenses and liabilities which might be incurred by it in compliance with such
request or direction;

     (6)  the Trustee shall not be bound to make any investigation into the
facts or matters stated in any resolution, certificate, statement, instrument,
opinion, report, notice, request, direction, consent, order, bond, debenture,
note, coupon, other evidence of indebtedness or other paper or document, but the
Trustee, in its discretion, may make such further inquiry or investigation into
such facts or matters as it may see fit, and, if the Trustee shall determine to

                                       57
<PAGE>
 
make such further inquiry or investigation, it shall be entitled to examine,
during business hours and upon reasonable notice, the books, records and
premises of the Company and the Guarantor, personally or by agent or attorney;

     (7)  the Trustee may execute any of the trusts or powers hereunder or
perform any duties hereunder either directly or by or through agents or
attorneys and the Trustee shall not be responsible for any misconduct or
negligence on the part of any agent or attorney appointed with due care by it
hereunder;

     (8)  the Trustee undertakes to perform such duties and only such duties as
are specifically set forth in this Indenture, and no implied covenants or
obligations shall be read into this Indenture against the Trustee; and

     (9)  no provision of this Indenture shall be construed to relieve the
Trustee from liability for its own negligent action, its own negligent failure
to act, or its own willful misconduct, except that:

          (a)  the Trustee shall not be liable for any error of judgment made in
          good faith by a Responsible Officer, unless it shall be proved that
          the Trustee was negligent in ascertaining the pertinent facts;

          (b)  the Trustee shall not be liable with respect to any action taken
          or omitted to be taken by it in good faith in accordance with the
          direction of the Holders of a majority in principal amount of the
          Securities at the time Outstanding relating to the time, method and
          place of conducting any proceeding for any remedy available to the
          Trustee, or exercising any trust or power conferred upon the Trustee,
          under this Indenture and;

          (c)  this paragraph (9) shall not be construed to limit the effect of
          paragraph (8) of this Section 601.

     The duties and responsibilities of the Trustee shall be as provided by the
Trust Indenture Act and this Indenture.  Notwithstanding the foregoing, no
provision of this Indenture shall require the Trustee to expend or risk its own
funds or otherwise incur any financial liability in the performance of any of
its duties hereunder, or in the exercise of any of its rights or powers, if it
shall have reasonable grounds for believing that repayment of such funds or
indemnity reasonably satisfactory to it against such risk or liability is not
reasonably assured to it.  Whether or not therein expressly so provided, every
provision of this Indenture relating to the conduct or affecting the liability
of or affording protection to the Trustee shall be subject to the provisions of
this Section 601.

Section 602.  Notice of Defaults.
              ------------------     

     Within 90 days after the occurrence of any Default (actually known to a
Responsible Officer of the Trustee) hereunder with respect to the Securities of
any series, the Trustee shall transmit by mail to all Holders of Securities of
such series entitled to receive reports pursuant to

                                       58
<PAGE>
 
Section 703(3), notice of such Default hereunder known to the Trustee, unless
such Default shall have been cured or waived; provided, however, that, except in
                                              --------  -------                 
the case of a default in the payment of the principal of (or premium, if any),
or interest, if any, on, or Additional Amounts or any sinking fund or purchase
fund installment with respect to, any Security of such series, the Trustee shall
be protected in withholding such notice if and so long as the board of
directors, the executive committee or a trust committee of directors and/or
Responsible Officers of the Trustee in good faith determine that the withholding
of such notice is in the best interest of the Holders of Securities and Coupons
of such series, and provided, further, that in the case of any Default of the
                    --------  -------                                        
character specified in Section 501(4) with respect to Securities of such series,
no such notice to Holders shall be given until at least 60 days after the
occurrence thereof.

Section 603.  Not Responsible for Recitals or Issuance of Securities.
              ------------------------------------------------------     

     The recitals contained herein and in the Securities, except the Trustee's
certificate of authentication, and in any Coupons shall be taken as the
statements of the Company or the Guarantor, as the case may be, and neither the
Trustee nor any Authenticating Agent assumes any responsibility for their
correctness.  The Trustee makes no representations as to the validity or
sufficiency of this Indenture or of the Securities or Coupons appertaining
thereto or the Guarantees or the Common Stock issuable upon the conversion of
Securities in accordance with the provisions of Article Twelve, except that the
Trustee represents that it is duly authorized to execute and deliver this
Indenture, authenticate the Securities and perform its obligations hereunder and
that the statements made by it in a Statement of Eligibility and Qualification
on Form T-1 supplied to the Company are true and accurate, subject to the
qualifications set forth therein.  Neither the Trustee nor any Authenticating
Agent shall be accountable for the use or application by the Company of the
Securities or the proceeds thereof.

Section 604.  May Hold Securities; Act as Trustee Under Other Indenture.
              ---------------------------------------------------------     

     The Trustee, any Authenticating Agent, any Paying Agent, any Security
Registrar or any other Person that may be an agent of the Trustee, the Company,
or the Guarantor, in its individual or any other capacity, may become the owner
or pledgee of Securities or Coupons and, subject to Sections 310(b) and 311 of
the Trust Indenture Act, may otherwise deal with the Company and the Guarantor
with the same rights it would have if it were not Trustee, Authenticating Agent,
Paying Agent, Security Registrar or such other agent.

     Subject to Section 310(b) and 311 of the Trust Indenture Act, the Trustee
may become and act as trustee under other indentures under which other
securities, or certificates of interest or participation in other securities, of
the Company, the Guarantor or any Subsidiary thereof are outstanding in the same
manner as if it were not Trustee hereunder.

Section 605.  Money Held in Trust.
              -------------------     

     Except as provided in Section 403 and Section 1003, money held by the
Trustee in trust hereunder need not be segregated from other funds except to the
extent required by law and shall be held uninvested.  The Trustee shall be under
no liability for interest on any money received by 

                                       59
<PAGE>
 
it hereunder except as otherwise agreed in writing with the Company or the
Guarantor, as the case may be.

Section 606.  Compensation and Reimbursement.
              ------------------------------     

     Each of the Company and the Guarantor agrees:

     (1)  to pay to the Trustee from time to time reasonable compensation as
shall be agreed in writing between the Company on the one hand and the Trustee
on the other for all services rendered by the Trustee hereunder (which
compensation shall not be limited by any provision of law in regard to the
compensation of a trustee of an express trust);

     (2)  except as otherwise expressly provided herein, to reimburse the
Trustee upon its request for all reasonable expenses, disbursements and advances
incurred or made by the Trustee in accordance with any provision of this
Indenture (including the reasonable compensation and the expenses and
disbursements of its agents and counsel), except any such expense, disbursement
or advance as may be attributable to the Trustee's negligence or bad faith; and

     (3)  to indemnify the Trustee and its officers, directors, employees and
agents for, and to hold them harmless against, any loss, liability or expense
incurred without negligence or bad faith on their part, arising out of or in
connection with the acceptance or administration of the trust or trusts
hereunder, including the costs and expenses of defending themselves against any
claim or liability in connection with the exercise or performance of any of
their powers or duties hereunder, except to the extent that any such loss,
liability or expense was due to the Trustee's negligence or bad faith.  The
indemnification provided for herein shall survive the termination of this
Indenture or the earlier resignation or removal of the Trustee.

     As security for the performance of the obligations of the Company under
this Section 606, the Trustee shall have a lien prior to the Securities of any
series upon all property and funds held or collected by the Trustee as such,
except funds held in trust for the payment of principal of, and premium or
interest on or any Additional Amounts with respect to Securities or any Coupons
appertaining thereto.

     Any compensation or expense incurred by the Trustee after a default
specified by Section 501 is intended to constitute an expense of administration
under any then applicable bankruptcy or insolvency law.  "Trustee" for purposes
                                                          -------              
of this Section 606 shall include any predecessor Trustee but the negligence or
bad faith of any Trustee shall not affect the rights of any other Trustee under
this Section 606.

Section 607.  Corporate Trustee Required; Eligibility.
              ---------------------------------------     

     There shall at all times be a Trustee hereunder that is a Corporation,
organized and doing business under the laws of the United States, eligible under
Section 310(a)(1) of the Trust Indenture Act to act as trustee under an
indenture qualified under the Trust Indenture Act and that has a combined
capital and surplus (computed in accordance with Section 310(a)(2) of the Trust
Indenture Act) of at least $50,000,000 and subject to supervision or examination
by Federal 

                                       60
<PAGE>
 
or state authority. If at any time the Trustee shall cease to be eligible in
accordance with the provisions of this Section, it shall resign immediately in
the manner and with the effect hereinafter specified in this Article.

Section 608.  Resignation and Removal; Appointment of Successor.
              -------------------------------------------------     

     (1)  No resignation or removal of the Trustee and no appointment of a
successor Trustee pursuant to this Article shall become effective until the
acceptance of appointment by the successor Trustee pursuant to Section 609.

     (2)  The Trustee may resign at any time with respect to the Securities of
one or more series by giving written notice thereof to the Company.  If the
instrument of acceptance by a successor Trustee required by Section 609 shall
not have been delivered to the Trustee within 30 days after the giving of such
notice of resignation, the resigning Trustee may petition any court of competent
jurisdiction for the appointment of a successor Trustee with respect to the
Securities of such series.

     (3)  The Trustee may be removed at any time with respect to the Securities
of any series by Act of the Holders of a majority in principal amount of the
Outstanding Securities of such series, delivered to the Trustee and to the
Company and the Guarantor.

     (4)  If at any time:

          (a)  the Trustee shall fail to comply with the obligations imposed
     upon it under Section 310(b) of the Trust Indenture Act with respect to
     Securities of any series after written request therefor by the Company, the
     Guarantor or any Holder of a Security of such series who has been a bona
     fide Holder of a Security of such series for at least six months, or

          (b)  the Trustee shall cease to be eligible under Section 607 and
     shall fail to resign after written request therefor by the Company, the
     Guarantor or any such Holder, or

          (c)  the Trustee shall become incapable of acting or shall be adjudged
     to be bankrupt or insolvent or a receiver of the Trustee or of its property
     shall be appointed or any public officer shall take charge or control of
     the Trustee or of its property or affairs for the purpose of
     rehabilitation, conservation or liquidation,

     then, in any such case, (i) the Company, by or pursuant to a Board
Resolution, may remove the Trustee with respect to all Securities or the
Securities of such series, or (ii) subject to Section 315(e) of the Trust
Indenture Act, any Holder of a Security who has been a bona fide Holder of a
Security of such series for at least six months may, on behalf of himself and
all others similarly situated, petition any court of competent jurisdiction for
the removal of the Trustee with respect to all Securities of such series and the
appointment of a successor Trustee or Trustees.

                                       61
<PAGE>
 
     (5)  If the Trustee shall resign, be removed or become incapable of acting,
or if a vacancy shall occur in the office of Trustee for any cause, with respect
to the Securities of one or more series, the Company, by or pursuant to a Board
Resolution, shall promptly appoint a successor Trustee or Trustees with respect
to the Securities of that or those series (it being understood that any such
successor Trustee may be appointed with respect to the Securities of one or more
or all of such series and that at any time there shall be only one Trustee with
respect to the Securities of any particular series) and shall comply with the
applicable requirements of Section 609. If, within one year after such
resignation, removal or incapability, or the occurrence of such vacancy, a
successor Trustee with respect to the Securities of any series shall be
appointed by Act of the Holders of a majority in principal amount of the
Outstanding Securities of such series delivered to the Company and the retiring
Trustee, the successor Trustee so appointed shall, forthwith upon its acceptance
of such appointment in accordance with the applicable requirements of Section
609, become the successor Trustee with respect to the Securities of such series
and to that extent supersede the successor Trustee appointed by the Company. If
no successor Trustee with respect to the Securities of any series shall have
been so appointed by the Company or the Holders of Securities and accepted
appointment in the manner required by Section 609, any Holder of a Security who
has been a bona fide Holder of a Security of such series for at least six months
may, on behalf of himself and all others similarly situated, petition any court
of competent jurisdiction for the appointment of a successor Trustee with
respect to the Securities of such series.

     (6)  The Company shall give notice of each resignation and each removal of
the Trustee with respect to the Securities of any series and each appointment of
a successor Trustee with respect to the Securities of any series by mailing
written notice of such event by first-class mail, postage prepaid, to the
Holders of Registered Securities, if any, of such series as their names and
addresses appear in the Security Register and, if Securities of such series are
issued as Bearer Securities, by publishing notice of such event once in an
Authorized Newspaper in each Place of Payment located outside the United States.
Each notice shall include the name of the successor Trustee with respect to the
Securities of such series and the address of its Corporate Trust Office.

     (7)  The retiring Trustee shall not be liable for any of the acts or
omissions of any successor Trustee appointed hereunder.

     (8)  No appointment of a successor Trustee shall be effective until all
fees, charges and expenses of the retiring Trustee not subject to any good faith
dispute have been paid.

Section 609.  Acceptance of Appointment by Successor.
              --------------------------------------     

     (1)  Upon the appointment hereunder of any successor Trustee with respect
to all Securities, such successor Trustee so appointed shall execute,
acknowledge and deliver to the Company, the Guarantor and the retiring Trustee
an instrument accepting such appointment, and thereupon the resignation or
removal of the retiring Trustee shall become effective and such successor
Trustee, without any further act, deed or conveyance, shall become vested with
all the rights, powers, trusts and duties hereunder of the retiring Trustee;
but, on the request of the Company, the Guarantor or such successor Trustee,
such retiring Trustee, upon payment of its 

                                       62
<PAGE>
 
charges, shall execute and deliver an instrument transferring to such successor
Trustee all the rights, powers and trusts of the retiring Trustee and, subject
to Section 1003, shall duly assign, transfer and deliver to such successor
Trustee all property and money held by such retiring Trustee hereunder, subject
nevertheless to its claim, if any, provided for in Section 606.

     (2)  Upon the appointment hereunder of any successor Trustee with respect
to the Securities of one or more series, the Company, the Guarantor, the
retiring Trustee and such successor Trustee shall execute and deliver an
indenture supplemental hereto wherein each successor Trustee shall accept such
appointment and which (a) shall contain such provisions as shall be necessary or
desirable to transfer and confirm to, and to vest in, such successor Trustee all
the rights, powers, trusts and duties of the retiring Trustee with respect to
the Securities of that or those series to which the appointment of such
successor Trustee relates, (b) if the retiring Trustee is not retiring with
respect to all Securities, shall contain such provisions as shall be deemed
necessary or desirable to confirm that all the rights, powers, trusts and duties
of the retiring Trustee with respect to the Securities of that or those series
as to which the retiring Trustee is not retiring shall continue to be vested in
the retiring Trustee, and (c) shall add to or change any of the provisions of
this Indenture as shall be necessary to provide for or facilitate the
administration of the trusts hereunder by more than one Trustee, it being
understood that nothing herein or in such supplemental indenture shall
constitute such Trustees co-trustees of the same trust, that each such Trustee
shall be trustee of a trust or trusts hereunder separate and apart from any
trust or trusts hereunder administered by any other such Trustee and that no
Trustee shall be responsible for any notice given to, or received by, or any act
or failure to act on the part of any other Trustee hereunder, and, upon the
execution and delivery of such supplemental indenture, the resignation or
removal of the retiring Trustee shall become effective to the extent provided
therein, such retiring Trustee shall have no further responsibility for the
exercise of rights and powers or for the performance of the duties and
obligations vested in the Trustee under this Indenture with respect to the
Securities of that or those series to which the appointment of such successor
Trustee relates other than as hereinafter expressly set forth, and such
successor Trustee, without any further act, deed or conveyance, shall become
vested with all the rights, powers, trusts and duties of the retiring Trustee
with respect to the Securities of that or those series to which the appointment
of such successor Trustee relates; but, on request of the Company, the Guarantor
or such successor Trustee, such retiring Trustee, upon payment of its charges
with respect to the Securities of that or those series to which the appointment
of such successor relates and subject to Section 1003 shall duly assign,
transfer and deliver to such successor Trustee, to the extent contemplated by
such supplemental indenture, the property and money held by the retiring Trustee
hereunder with respect to the securities of that or those series to which the
appointment of such successor Trustee relates, subject to its claim, if any,
provided for in Section 606.

     (3)  Upon request of any Person appointed hereunder as a successor Trustee,
the Company or the Guarantor shall execute any and all instruments for more
fully and certainly vesting in and confirming to such successor Trustee all such
rights, powers and trusts referred to in paragraph (1) or (2) of this Section,
as the case may be.

                                       63
<PAGE>
 
     (4)  No Person shall accept its appointment hereunder as a successor
Trustee unless at the time of such acceptance such successor Person shall be
qualified and eligible under this Article Six.

Section 610.  Merger, Conversion, Consolidation or Succession to Business.
              -----------------------------------------------------------     

     Any Corporation into which the Trustee may be merged or converted or with
which it may be consolidated, or any Corporation resulting from any merger,
conversion or consolidation to which the Trustee shall be a party, or any
Corporation succeeding to all or all of the corporate trust business of the
Trustee, shall be the successor of the Trustee hereunder, provided such
Corporation shall be otherwise qualified and eligible under this Article Six,
without the execution
or filing of any paper or any further act on the part of any of the parties
hereto.  In case any Securities shall have been authenticated but not delivered
by the Trustee then in office, any successor by merger, conversion or
consolidation to such authenticating Trustee may adopt such authentication and
deliver the Securities so authenticated with the same effect as if such
successor Trustee had itself authenticated such Securities.

Section 611.  Preferential Collection of Claims Against Company.
              -------------------------------------------------     

     If and when the Trustee shall be or become a creditor of the Company, the
Guarantor or any other obligor upon the Securities, the Trustee shall be subject
to the provisions of the Trust Indenture Act regarding the collection of claims
against the Company, the Guarantor or any such other obligor.

Section 612.  Appointment of Authenticating Agent.
              -----------------------------------     

     The Trustee may appoint one or more Authenticating Agents acceptable to the
Company with respect to one or more series of Securities which shall be
authorized to act on behalf of the Trustee to authenticate Securities of that or
those series issued upon original issue, exchange, registration of transfer,
partial redemption or partial repayment, or pursuant to Section 306, and
Securities so authenticated shall be entitled to the benefits of this Indenture
and shall be valid and obligatory for all purposes as if authenticated by the
Trustee hereunder.  Except in the case of an original issuance or in the case of
replacement of lost, stolen or destroyed securities, wherever reference is made
in this Indenture to the authentication and delivery of Securities by the
Trustee or the Trustee's certificate of authentication, such reference shall be
deemed to include authentication and delivery on behalf of the Trustee by an
Authenticating Agent and a certificate of authentication executed on behalf of
the Trustee by an Authenticating Agent.

     Each Authenticating Agent shall be acceptable to the Company and, except as
provided in or pursuant to this Indenture, shall at all times be a corporation
that would be permitted by the Trust Indenture Act to act as trustee under an
indenture qualified under the Trust Indenture Act, is authorized under
applicable law and by its charter to act as an Authenticating Agent and has a
combined capital and surplus (computed in accordance with Section 310(a)(2) of
the Trust Indenture Act) of at least $50,000,000.   If at any time an
Authenticating Agent shall cease to be eligible in accordance with the
provisions of this Section, it shall resign immediately in the manner and with
the effect specified in this Section.

                                       64
<PAGE>
 
     Any corporation into which an Authenticating Agent may be merged or
converted or with which it may be consolidated, or any corporation resulting
from any merger, conversion or consolidation to which such Authenticating Agent
shall be a party, or any corporation succeeding to all or substantially all of
the corporate agency or corporate trust business of an Authenticating Agent,
shall be the successor of such Authenticating Agent hereunder, provided such
corporation shall be otherwise eligible under this Section, without the
execution or filing of any paper or any further act on the part of the Trustee
or the Authenticating Agent.

     An Authenticating Agent may resign at any time by giving written notice
thereof to the Trustee, the Company and the Guarantor.  The Trustee may at any
time terminate the agency of an Authenticating Agent by giving written notice
thereof to such Authenticating Agent, the Company and the Guarantor. Upon
receiving such a notice of resignation or upon such a termination, or in case at
any time such Authenticating Agent shall cease to be eligible in accordance with
the provisions of this Section, the Trustee may appoint a successor
Authenticating Agent which shall be acceptable to the Company and shall (i) mail
written notice of such appointment by first-class mail, postage prepaid, to all
Holders of Registered Securities, if any, of the series with respect to which
such Authenticating Agent shall serve, as their names and addresses appear in
the Security Register, and (ii) if Securities of the series are issued as Bearer
Securities, publish notice of such appointment at least once in an Authorized
Newspaper in the place where such successor Authenticating Agent has its
principal office if such office is located outside the United States. Any
successor Authenticating Agent, upon acceptance of its appointment hereunder,
shall become vested with all the rights, powers and duties of its predecessor
hereunder, with like effect as if originally named as an Authenticating Agent.
No successor Authenticating Agent shall be appointed unless eligible under the
provisions of this Section.

     The Company agrees to pay each Authenticating Agent from time to time
reasonable compensation for its services under this Section.  If the Trustee
makes such payments, it shall be entitled to be reimbursed for such payments,
subject to the provisions of Section 606.

     The provisions of Sections 308, 603 and 604 shall be applicable to each
Authenticating Agent.

     If an Authenticating Agent is appointed with respect to one or more series
of Securities pursuant to this Section, the Securities of such series may have
endorsed thereon, in addition to or in lieu of the Trustee's certificate of
authentication, an alternate certificate of authentication in substantially the
following form:

                                       65
<PAGE>
 
     This is one of the Securities of the series designated therein referred to
in the within-mentioned Indenture.


Dated:____________________            [NAME OF TRUSTEE],
                                      As Trustee


                                      By: [NAME OF AUTHENTICATION AGENT]
                                          As Authenticating Agent


                                      By:_______________________
                                         Authorized Officer


     If all of the Securities of any series may not be originally issued at one
time, and if the Trustee does not have an office capable of authenticating
Securities upon original issuance located in a Place of Payment where the
Company wishes to have Securities of such series authenticated upon original
issuance, the Trustee, if so requested in writing (which writing need not be
accompanied by or contained in an Officers' Certificate by the Company), shall
appoint in accordance with this Section 612 an Authenticating Agent having an
office in a Place of Payment designated by the Company with respect to such
series of Securities.

Section 613.  Conflicting Interests.
              ---------------------     

     If the Trustee has or shall acquire any conflicting interest within the
meaning of the Trust Indenture Act, the Trustee shall either eliminate such
interest or resign, to the extent and in the manner provided by, and subject to
the provisions of the Trust Indenture Act and this Indenture.  To the extent
permitted by such Act, the Trustee shall not be deemed to have a conflicting
interest by virtue of being a trustee under this Indenture with respect to
Securities of more than one series or a trustee under other indentures between
the Company, the Guarantor or a Subsidiary thereof and the Trustee that have not
been satisfied and discharged and that may be excluded by the proviso to Section
310(b)(1) of the Trust Indenture Act.

Section 614.  Protection of Agents. 
              --------------------

     Any Authenticating Agent, Conversion Agent, Paying Agent or Securities
Registrar hereunder shall be entitled to all of the rights, immunities,
indemnities and protections afforded to the Trustee hereunder.

                                       66
<PAGE>
 
                                 ARTICLE SEVEN

          HOLDERS LISTS AND REPORTS BY TRUSTEE, COMPANY AND GUARANTOR

Section 701.  Company and Guarantor to Furnish Trustee Names and Addresses of
              ---------------------------------------------------------------
Holders.
- -------     

     In accordance with Section 312(a) of the Trust Indenture Act, with respect
to each series of the Securities, the Company and the Guarantor shall furnish or
cause to be furnished to the Trustee:

     (1)  semi-annually, not later than 15 days after the Regular Record Date or
upon such other dates as are set forth in or pursuant to the Board Resolution,
Officers' Certificate or indenture supplemental hereto authorizing such series,
a list for each series of Securities, in such form as the Trustee may reasonably
require, of the names and addresses of Holders of Registered Securities as of
the applicable date, and

     (2)  at such other times as the Trustee may request in writing, within 30
days after the receipt by the Company or the Guarantor of any such request, a
list of similar form and content as of a date not more than 15 days prior to the
time such list is furnished, excluding from any such list names and addresses
received by the Trustee in its capacity as Security Registrar.

Section 702.  Preservation of Information; Communications to Holders.
              ------------------------------------------------------     

     The Trustee shall preserve, in as current a form as is reasonably
practicable, the names and addresses of Holders contained in the most recent
list furnished to the Trustee as provided in Section 701 and the names and
addresses of Holders received by the Trustee in its capacity as Security
Registrar.  The Trustee may destroy any list furnished to it as provided in
Section 701 upon receipt of a new list so furnished.

     The rights of the Holders to communicate with other Holders with respect to
their rights under this Indenture or under the Securities, and the corresponding
rights, privileges and obligations of the Trustee, shall be as provided by the
Trust Indenture Act.

     Every Holder of Securities or Coupons, by receiving and holding the same,
agrees with the Company, the Guarantor and the Trustee that neither the Company,
the Guarantor nor the Trustee, nor any agent of any of them, shall be held
accountable by reason of the disclosure of any such information as to the names
and addresses of the Holders of Securities in accordance with Section 312(c) of
the Trust Indenture Act, regardless of the source from which such information
was derived, and that the Trustee shall not be held accountable by reason of
mailing any material pursuant to a request made under Section 312(b) of the
Trust Indenture Act.

Section 703.  Reports by Trustee.
              ------------------     

          (1)  Within 60 days after July 15 of each year commencing with the
     first July 15 following the first issuance of Securities pursuant to
     Section 301, if required by Section 313(a) of the Trust Indenture Act, the
     Trustee shall transmit, pursuant to 

                                       67
<PAGE>
 
     Section 313(c) of the Trust Indenture Act, a brief report dated as of such
     July 15 with respect to any of the events specified in said Section 313(a)
     which may have occurred since the later of the immediately preceding July
     15 and the date of this Indenture.

          (2)  The Trustee shall transmit to Holders the reports concerning the
     Trustee and its actions under this Indenture as may be required pursuant to
     the Trust Indenture Act at the times and in the manner specified therein.

          (3)  Reports pursuant to this Section shall be transmitted in the
     manner and to the Persons required by Sections 313(c) and 313(d) of the
     Trust Indenture Act.

Section 704.  Reports by Company and Guarantor.
              --------------------------------     

     The Company and the Guarantor, pursuant to Section 314(a) of the Trust
Indenture Act, shall:

          (1)  file with the Trustee, within 15 days after the Company and the
     Guarantor are required to file the same with the Commission, copies of the
     annual reports and of the information, documents and other reports (or
     copies of such portions of any of the foregoing as the Commission may from
     time to time by rules and regulations prescribe) which the Company and the
     Guarantor may be required to file with the Commission pursuant to Section
     13 or Section 15(d) of the Exchange Act; or, if the Company or the
     Guarantor is not required to file information, documents or reports
     pursuant to either of said Sections, then they shall file with the Trustee
     and the Commission, in accordance with rules and regulations prescribed
     from time to time by the Commission, such of the supplementary and periodic
     information, documents and reports which may be required pursuant to
     Section 13 of the Exchange Act in respect of a security listed and
     registered on a national securities exchange as may be prescribed from time
     to time in such rules and regulations;

          (2)  file with the Trustee and the Commission, in accordance with
     rules and regulations prescribed from time to time by the Commission, such
     additional information, documents and reports with respect to compliance by
     the Company and the Guarantor with the conditions and covenants of this
     Indenture as may be required from time to time by such rules and
     regulations; and

          (3)  transmit within 30 days after the filing thereof with the
     Trustee, in the manner and to the extent provided in Section 313(c) of the
     Trust Indenture Act, such summaries of any information, documents and
     reports required to be filed by the Company and the Guarantor pursuant to
     paragraphs (1) and (2) of this Section as may be required by rules and
     regulations prescribed from time to time by the Commission.

                                       68
<PAGE>
 
                                 ARTICLE EIGHT

                 CONSOLIDATION, MERGER, CONVEYANCE OR TRANSFER

Section 801.  Company or Guarantor May Consolidate, Etc., Only on Certain
              -----------------------------------------------------------
Terms.
- -----

     Neither the Company nor the Guarantor shall consolidate with or merge into
any other Person or convey, transfer or lease all or substantially all of its
properties and assets to any Person, and neither the Company nor the Guarantor
shall permit any Person to consolidate with or merge into the Company or the
Guarantor, as the case may be, or convey, transfer or lease all or substantially
all of its properties and assets  to the Company or the Guarantor, as the case
may be, unless either:

          (a)  in case the Company or the Guarantor, as the case may be, shall
     consolidate with or merge into another Person or convey, transfer or lease
     all or substantially all of its properties and assets  to any Person, the
     Person formed by such consolidation or into which the Company or the
     Guarantor, as the case may be, is merged or the Person which acquires by
     conveyance or transfer, or which leases, all or substantially all of the
     properties and assets of the Company or the Guarantor, as the case may be,
     shall be (i) a corporation, limited liability company, partnership or trust
     organized and validly existing under the laws of the United States or (ii)
     a corporation, limited liability company, partnership or trust organized
     and validly existing under the laws of a jurisdiction other than the United
     States (a "Foreign Entity") that shall expressly assume, by an indenture
                --------------                                               
     supplemental hereto executed and delivered to the Trustee, in form
     reasonably satisfactory to the Trustee, in the case of the Company, the due
     and punctual payment of the principal of (and premium, if any) and interest
     and Additional Amounts on all the Securities and Coupons and the
     performance and observance of every covenant of this Indenture on the part
     of the Company to be performed or observed and shall have provided for
     conversion rights in accordance with Article Twelve, and, in the case of
     the Guarantor, the due and punctual performance of the Guarantees and the
     performance and observance of every covenant of this Indenture on the part
     of the Guarantor to be performed or observed.  In the event that such
     Person is a Foreign Entity, it shall expressly agree to make payments under
     the Securities and Coupons free of any deduction or withholding for any and
     all then existing or future withholding taxes, levies, imposts and charges
     whatsoever imposed by or for the account of the jurisdiction where such
     Foreign Entity is generally subject to taxation (or any political
     subdivision or taxing authority thereof or therein) in a manner equivalent
     to that set forth herein, subject to the exceptions contained elsewhere
     herein;

          (b)  immediately after giving effect to such transaction and treating
     any indebtedness which becomes an obligation of the Company or one of its
     Subsidiaries or of the Guarantor or one of its Subsidiaries as a result of
     such transaction as having been incurred by the Company, the Guarantor or
     such Subsidiary at the time of such transaction, no Event of Default, and
     no event which, after notice or lapse of time or both, would become an
     Event of Default, shall have happened and be continuing; and

                                       69
<PAGE>
 
          (c)  the Company or the Guarantor, as the case may be, has delivered
     to the Trustee an Officers' Certificate and an Opinion of Counsel, each
     stating that such consolidation, merger, conveyance, transfer or lease and,
     if a supplemental indenture is required in connection with such
     transaction, such supplemental indenture comply with this Article and that
     all conditions precedent herein provided for relating to such transaction
     have been complied with.

Section 802.  Successor Corporation Substituted.
              ---------------------------------     

     Upon any consolidation by the Company or the Guarantor, as the case may be,
with or merger by the Company or the Guarantor, as the case may be, into any
other Person or any conveyance, transfer or lease of all or substantially all of
the properties and assets of the Company or the Guarantor, as the case may be,
in accordance with Section 801, the successor Person formed by such
consolidation or into which the Company or the Guarantor, as the case may be, is
merged or to which such conveyance, transfer or lease is made, shall succeed to,
and be substituted for, and may exercise every right and power of, the Company
or the Guarantor, as the case may be, under this Indenture with the same effect
as if such successor Person had been named as the Company or the Guarantor, as
the case may be, herein, and thereafter, except in the case of a lease, the
predecessor Person shall be relieved of all obligations and covenants under this
Indenture and the Securities.


                                 ARTICLE NINE

                            SUPPLEMENTAL INDENTURES

Section 901.  Supplemental Indentures Without Consent of Holders.
              --------------------------------------------------     

     Without the consent of any Holders of Securities or Coupons, the Company,
when authorized by or pursuant to a Board Resolution, the Guarantor, when
authorized by a Board Resolution, and the Trustee, at any time and from time to
time, may enter into one or more indentures supplemental hereto, in form
satisfactory to the Trustee, for any of the following purposes:

     (1)  to evidence the succession of another Person to the Company or the
Guarantor, as the case may be, and the assumption by any such successor of the
covenants of the Company or the Guarantor, as the case may be, contained herein
and in the Securities or the Guarantees; or

     (2)  to add to the covenants of the Company or the Guarantor for the
benefit of the Holders of all or any series of Securities (as shall be specified
in such supplemental indenture or indentures and if such covenants are to be for
the benefit of less than all series of Securities, stating that such covenants
are being included solely for the benefit of such series) or to surrender any
right or power herein conferred upon the Company or the Guarantor; or

     (3)  to add to or change any of the provisions of this Indenture to provide
that Bearer Securities may be registrable as to principal, to change or
eliminate any restrictions on the 

                                       70
<PAGE>
 
payment of principal of, any premium or interest on or any Additional Amounts
with respect to Securities, to permit Bearer Securities to be issued in exchange
for Registered Securities, to permit Bearer Securities to be exchanged for
Bearer Securities of additional authorized denominations or to permit or
facilitate the issuance of Securities in uncertificated form, provided any such
action shall not adversely affect the interests of the Holders of Securities of
any series or any Coupons appertaining thereto in any material respect; or

     (4)  to establish the form or terms of Securities of any series and any
Coupons appertaining thereto as permitted by Sections 201 and 301 or of the
related Guarantees as permitted by Section 202; or

     (5)  to evidence and provide for the acceptance of appointment hereunder by
a successor Trustee with respect to the Securities of one or more series and to
add to or change any of the provisions of this Indenture as shall be necessary
to provide for or facilitate the administration of the trusts hereunder by more
than one Trustee, pursuant to the requirements of Section 609; or

     (6)  to cure any ambiguity or to correct or supplement any provision herein
which may be defective or inconsistent with any other provision herein, or to
make any other provisions with respect to matters or questions arising under
this Indenture which shall not adversely affect the interests of the Holders of
Securities of any series then Outstanding or any Coupons appertaining thereto in
any material respect; or

     (7)  to add any additional Events of Default with respect to all or any
series of Securities (as shall be specified in such supplemental indenture and
if such additional Events of Default are to be for the benefit of less than all
series of Securities, stating that such additional Events of Default are
expressly being included solely for the benefit of such series); or

     (8)  to supplement any of the provisions of this Indenture to such extent
as shall be necessary to permit or facilitate the defeasance and discharge of
any series of Securities pursuant to Article Four, provided that any such action
shall not adversely affect the interests of any Holder of a Security of such
series and any Coupons appertaining thereto or any other Security or Coupon in
any material respect; or

     (9)  to secure the Securities and Guarantees; or

     (10) to amend or supplement any provision contained herein or in any
supplemental indenture (which amendment or supplement may apply to one or more
series of Securities or to one or more Securities within any series as specified
in such supplemental indenture or indentures), provided that such amendment or
supplement does not apply to any Outstanding Security issued prior to the date
of such supplemental indenture and entitled to the benefits of such provision or
modify the rights of the Holder of any such Security with respect to such
provision.

                                       71
<PAGE>
 
Section 902.  Supplemental Indentures With Consent of Holders.
              -----------------------------------------------     

     With the consent of the Holders of not less than a majority in principal
amount of the Outstanding Securities of each series affected by such
supplemental indenture, by Act of said Holders delivered to the Company, the
Guarantor and the Trustee, the Company, when authorized by or pursuant to a
Board Resolution, the Guarantor, when authorized by or pursuant to a Board
Resolution, and the Trustee may enter into an indenture or indentures
supplemental hereto for the purpose of adding any provisions to or changing in
any manner or eliminating any of the provisions of this Indenture or of the
Securities of such series or of modifying in any manner the rights of the
Holders of Securities of such series under this Indenture; provided, however,
                                                           --------  ------- 
that no such supplemental indenture, without the consent of the Holder of each
Outstanding Security affected thereby, shall

          (1)  change the Stated Maturity of the principal of, or any premium or
     installment of principal or interest on or any Additional Amounts with
     respect to, any Security, or any sinking fund or analogous payment in
     respect thereof, or reduce the principal amount thereof or the rate (or
     modify the calculation of such rate) of interest thereon or any Additional
     Amounts with respect thereto, or any premium payable upon the redemption
     thereof or otherwise, or change the obligation of the Company to pay
     Additional Amounts pursuant to Section 1004, or reduce the amount of the
     principal of any Security that would be due and payable upon a declaration
     of acceleration of the Maturity thereof pursuant to Section 502 or the
     amount thereof provable in bankruptcy pursuant to Section 504, adversely
     affect the right of repayment at the option of any Holder as contemplated
     by Article Fifteen, or change the provisions of Article Ten relating to
     Place of Payment for Bearer Securities being located outside the United
     States, or the Currency in which the principal of, any premium or interest
     on, or any Additional Amounts with respect to any Security or any sinking
     or analogous fund payment in respect thereof, is payable, or impair the
     right to institute suit for the enforcement of any such payment on or after
     the Stated Maturity thereof (or, in the case of redemption, on or after the
     Redemption Date or, in the case of repayment at the option of the Holder,
     on or after the Repayment Date), or

          (2)  reduce the percentage in principal amount of the Outstanding
     Securities of any series, the consent of whose Holders is required for any
     such supplemental indenture, or the consent of whose Holders is required
     for any waiver (of compliance with certain provisions of this Indenture or
     certain defaults hereunder and their consequences) provided for in this
     Indenture, or reduce the requirements of Section 1604 for quorum or voting,
     or

          (3)  modify any of the provisions of this Section or Section 513,
     except to increase any such percentage or to provide that certain other
     provisions of this Indenture cannot be modified or waived without the
     consent of the Holder of each Outstanding Security affected thereby; or

          (4)  change in any manner adverse in any material respect to the
     interests of the Holders of any Outstanding Securities the terms and
     conditions of the obligations of 

                                       72
<PAGE>
 
     the Guarantor in respect of the due and punctual payment of the principal
     thereof and any premium or interest thereon or any sinking or analogous
     fund payments provided in respect thereof.

     A supplemental indenture which changes or eliminates any covenant or other
provision of this Indenture which shall have been included expressly and solely
for the benefit of one or more particular series of Securities, or which
modifies the rights of the Holders of Securities of such series with respect to
such covenant or other provision, shall be deemed not to affect the rights under
this Indenture of the Holders of Securities of any other series.

     It shall not be necessary for any Act of Holders of Securities under this
Section to approve the particular form of any proposed supplemental indenture,
but it shall be sufficient if such Act shall approve the substance thereof.

Section 903.  Execution of Supplemental Indentures.
              ------------------------------------     

     As a condition to executing, or accepting the additional trusts created by,
any supplemental indenture permitted by this Article Nine or the modifications
thereby of the trust created by this Indenture, the Trustee shall be entitled to
receive, and (subject to Section 315 of the Trust Indenture Act) shall be fully
protected in relying upon, an Opinion of Counsel stating that the execution of
such supplemental indenture is authorized or permitted by this Indenture and an
Officers' Certificate stating that all conditions precedent to the execution of
such supplemental indenture have been fulfilled.  The Trustee may, but shall not
be obligated to, enter into any such supplemental indenture which affects the
Trustee's own rights, duties or immunities under this Indenture or otherwise.

Section 904.  Effect of Supplemental Indentures.
              ---------------------------------     

     Upon the execution of any supplemental indenture under this Article, this
Indenture shall be modified in accordance therewith, and such supplemental
indenture shall form a part of this Indenture for all purposes; and every Holder
of a Security theretofore or thereafter authenticated and delivered hereunder
and of any Coupon appertaining thereto shall be bound thereby.

Section 905.  Reference in Securities to Supplemental Indentures.
              --------------------------------------------------     

     Securities of any series authenticated and delivered after the execution of
any supplemental indenture pursuant to this Article may, and shall if required
by the Trustee, bear a notation in form approved by the Trustee as to any matter
provided for in such supplemental indenture.  If the Company and the Guarantor
shall so determine, new Securities of any series so modified as to conform, in
the opinion of the Trustee, the Company and the Guarantor, to any such
supplemental indenture may be prepared and executed by the Company, the
Guarantees of the Guarantor may be endorsed thereon and such securities
authenticated and delivered by the Trustee in exchange for Outstanding
Securities of such series.

                                       73
<PAGE>
 
Section 906.  Conformity with Trust Indenture Act.
              -----------------------------------     

     Every supplemental indenture executed pursuant to this Article shall
conform to the requirements of the Trust Indenture Act as then in effect.


                                  ARTICLE TEN

                                   COVENANTS

Section 1001.  Payment of Principal, Any Premium, Interest and Additional
               ----------------------------------------------------------
Amounts.
- -------     

     The Company covenants and agrees for the benefit of each series of
Securities that it will duly and punctually pay the principal of, any premium
and interest on and any Additional Amounts with respect to the Securities of
each series in accordance with the terms thereof, any Coupons appertaining
thereto and this Indenture.  Any interest due on any Bearer Security on or
before the Maturity thereof, and any Additional Amounts payable with respect to
such interest, shall be payable only upon presentation and surrender of the
Coupons appertaining thereto for such interest as they severally mature.

Section 1002.  Maintenance of Office or Agency.
               -------------------------------     

     The Company and the Guarantor shall maintain in each Place of Payment for
any series of Securities, an Office or Agency where Securities of such series,
and Guarantees with respect thereto (but not Bearer Securities, except as
otherwise provided below, unless such Place of Payment is located outside the
United States) may be presented or surrendered for payment, where Securities of
such series may be surrendered for registration of transfer or exchange, where
Registered Securities may be surrendered for conversion, where Bearer Securities
may be surrendered for conversion in the circumstances described below (and not
otherwise) and where notices and demands to or upon the Company and the
Guarantor in respect of the Securities of such series relating thereto and this
Indenture may be served.  If Securities of a series are issuable as Bearer
Securities, the Company shall maintain, subject to any laws or regulations
applicable thereto, an Office or Agency in a Place of Payment and Place of
Conversion for such series which is located outside the United States where
Securities of such series and any Coupons appertaining thereto, and Guarantees
with respect thereto, may be presented and surrendered for payment or
conversion; provided, however, that if the Securities of such series are listed
            --------  -------                                                  
on the London Stock Exchange or the Luxembourg Stock Exchange or any other stock
exchange located outside the United States and such stock exchange shall so
require, the Company shall maintain a Paying Agent and a Conversion Agent in
London, Luxembourg or any other required city located outside the United States,
as the case may be, so long as the Securities of such series are listed on such
exchange.  The Company and the Guarantor will give prompt written notice to the
Trustee of the location, and any change in the location, of such Office or
Agency.  If at any time the Company or the Guarantor shall fail to maintain any
such required Office or Agency or shall fail to furnish the Trustee with the
address thereof, such presentations, surrenders, notices and demands may be made
or served at the Corporate Trust Office of the Trustee, except that Bearer
Securities of such series and any Coupons appertaining thereto, and Guarantees
with 

                                       74
<PAGE>
 
respect thereto, may be presented and surrendered for payment or conversion at
the place specified for that purpose with respect to such Securities as provided
in or pursuant to this Indenture, and the Company and the Guarantor hereby
appoint the Trustee as their agent to receive all such presentations,
surrenders, notices and demands.

     Except as otherwise provided in or pursuant to this Indenture, no payment
of principal, premium, interest or Additional Amounts with respect to Bearer
Securities (including payments by reason of the conversion thereof) shall be
made at any Office or Agency in the United States or by check mailed to any
address in the United States or by transfer to an account maintained with a bank
located in the United States; provided, however, that if amounts owing with
                              --------  -------
respect to any Bearer Securities shall be payable in Dollars, payment of
principal of, any premium or interest on and any Additional Amounts with respect
to any such Security, or Guarantees with respect thereto, may be made, and any
Bearer Securities may be surrendered for conversion, at the Corporate Trust
Office of the Trustee or any Office or Agency designated by the Company in the
Borough of Manhattan, The City of New York, if (but only if) payment of the full
amount of such principal, premium, interest or Additional Amounts, or surrender
of Bearer Securities for conversion, at all offices outside the United States
maintained for such purpose by the Company in accordance with this Indenture is
illegal or effectively precluded by exchange controls or other similar
restrictions on the full payment or receipt of such amounts in Dollars as
determined by the Company, or on surrender of any Bearer Securities for
conversion.

     The Company and the Guarantor may also from time to time designate one or
more other Offices or Agencies where the Securities of one or more series, and
Guarantees endorsed thereon, may be presented or surrendered for any or all such
purposes and may from time to time rescind such designations; provided, however,
                                                              --------  ------- 
that no such designation or rescission shall in any manner relieve the Company
or the Guarantor of its obligation to maintain an Office or Agency in each Place
of Payment and Place of Conversion for Securities of any series for such
purposes.  The Company and the Guarantor shall give prompt written notice to the
Trustee of any such designation or rescission and of any change in the location
of any such other Office or Agency.  Unless otherwise provided in or pursuant to
this Indenture, the Company and the Guarantor hereby designate as the Place of
Payment and the Place of Conversion for each series of Securities (other than
those issued as Bearer Securities) and the Guarantees endorsed thereon, the
Borough of Manhattan, The City of New York, and initially appoint the Corporate
Trust Office of the Trustee as the Company's and the Guarantor's Office or
Agency in the Borough of Manhattan, The City of New York for such purpose.  The
Company and the Guarantor may subsequently appoint a different Office or Agency
in the Borough of Manhattan, The City of New York for the Securities of any
series, and the Guarantees endorsed thereon.  Unless otherwise provided in or
pursuant to this Indenture, the Company and the Guarantor hereby designate as
the Place of Payment and the Place of Conversion for Bearer Securities and the
Guarantees endorsed thereon, to be London, England, and initially appoint the
office of the Trustee in London as the Office or Agency for such purpose and
initially appoint the office of the Trustee in London as its Paying Agent and
Conversion Agent in London.

     If at any time the Company shall fail to maintain any such required office
or agency, or shall fail to furnish the Trustee with the address thereof,
presentations and surrenders may be made and notices and demands may be served
on the Corporate Trust Office of the Trustee, 

                                       75
<PAGE>
 
except that Bearer Securities and Coupons may be presented and surrendered for
payment and conversion to the Paying Agent in London at its office in the City
of London, England or other Paying Agent or Conversion Agent outside the United
States, and the Company hereby appoints the Paying Agent in London as its agent
to receive such respective presentations, surrenders, notices and demands.

Section 1003.  Money for Securities Payments to be Held in Trust.
               -------------------------------------------------     

     If the Company or the Guarantor, as the case may be, shall at any time act
as its own Paying Agent with respect to any series of Securities, it shall, on
or before each due date of the principal of, any premium or interest on or
Additional Amounts with respect to any of the Securities of such series,
segregate and hold in trust for the benefit of the Persons entitled thereto a
sum in Dollars sufficient to pay the principal or any premium, interest or
Additional Amounts so becoming due until such sums shall be paid to such Persons
or otherwise disposed of as herein provided, and shall promptly notify the
Trustee of its action or failure so to act.

     Whenever the Company or the Guarantor, as the case may be, shall have one
or more Paying Agents for any series of Securities, it shall, on or prior to
each due date of the principal of, any premium or interest on or any Additional
Amounts with respect to any Securities of such series, deposit with any Paying
Agent a sum in Dollars sufficient to pay the principal or any premium, interest
or Additional Amounts so becoming due, such sum to be held in trust for the
benefit of the Persons entitled thereto, and (unless such Paying Agent is the
Trustee) the Company or the Guarantor, as the case may be, will promptly notify
the Trustee of its action or failure so to act.

     The Company or the Guarantor, as the case may be, shall cause each Paying
Agent for any series of Securities other than the Trustee to execute and deliver
to the Trustee an instrument in which such Paying Agent shall agree with the
Trustee, subject to the provisions of this Section, that such Paying Agent
shall:

          (1)  hold all sums held by it for the payment of the principal of, any
     premium or interest on or any Additional Amounts with respect to Securities
     of such series in trust for the benefit of the Persons entitled thereto
     until such sums shall be paid to such Persons or otherwise disposed of as
     provided in or pursuant to this Indenture;

          (2)  give the Trustee notice of any default by the Company or the
     Guarantor (or any other obligor upon the Securities of such series) in the
     making of any payment of the principal of, any premium or interest on or
     any Additional Amounts with respect to the Securities of such series;

          (3)  at any time during the continuance of any such default, upon the
     written request of the Trustee, forthwith pay to the Trustee all sums so
     held in trust by such Paying Agent; and

          (4)  indemnify the Trustee for any loss, cost, liability, or expense
     caused by any error, act or omission of the Paying Agent.

                                       76
<PAGE>
 
     The Company or the Guarantor, as the case may be, may at any time, for the
purpose of obtaining the satisfaction and discharge of this Indenture or for any
other purpose, pay, or by Company Order of the Company or the Guarantor direct
any Paying Agent to pay, to the Trustee all sums held in trust by the Company,
the Guarantor or such Paying Agent, such sums to be held by the Trustee upon the
same terms as those upon which such sums were held by the Company, the Guarantor
or such Paying Agent; and, upon such payment by any Paying Agent to the Trustee,
such Paying Agent shall be released from all further liability with respect to
such sums.

     Except as otherwise provided herein or pursuant hereto, any money deposited
with the Trustee or any Paying Agent, or then held by the Company or the
Guarantor, as the case may be, in trust for the payment of the principal of, any
premium or interest on or any Additional Amounts with respect to any Security of
any series or any Coupon appertaining thereto and remaining unclaimed for two
years after such principal or any such premium or interest or any such
Additional Amounts shall have become due and payable shall, unless otherwise
required by mandatory provisions of applicable escheat or abandoned or unclaimed
property law, be paid to the Company or the Guarantor, as the case may be, on
Company Request, or (if then held by the Company or the Guarantor) shall be
discharged from such trust; and the Holder of such Security or any Coupon
appertaining thereto, or Guarantees endorsed thereon, shall thereafter, as an
unsecured general creditor, look only to the Company or the Guarantor (pursuant
to the Guarantee) for payment thereof, and all liability of the Trustee or such
Paying Agent with respect to such trust money, and all liability of the Company
or the Guarantor as trustee thereof, shall thereupon cease; provided, however,
                                                            --------  ------- 
that the Trustee or such Paying Agent, before being required to make any such
repayment, may at the expense of the Company cause to be published once, in an
Authorized Newspaper in each Place of Payment for such series or to be mailed to
Holders of Registered Securities of such series, or both, notice that such money
remains unclaimed and that, after a date specified therein, which shall not be
less than 30 days from the date of such publication or mailing, any unclaimed
balance of such money then remaining will be repaid to the Company or the
Guarantor, as the case may be.

Section 1004.  Additional Amounts.
               ------------------     

     All payments of principal of, premium, if any, and interest on Securities
of any series to a Holder thereof who is not a United States person, and all
payments on the Guarantees to a Holder thereof who is not a United States person
shall be made without set-off, counterclaim, fees, liabilities or similar
deductions (including payments on redemption and repayment), and free and clear
of, and without deduction or withholding for, taxes, levies, imposts, duties,
assessments, charges or fees of whatsoever nature now or hereafter imposed,
levied, collected, deducted, withheld or assessed by or on behalf of the
Government of the United States, or any state or other political subdivision or
taxing authority thereof or therein ("Taxes").  If the Company, the Guarantor,
                                      -----                                   
or any agent of either is required by law or regulation to make any deduction or
withholding for or on account of Taxes, the Company or Guarantor, as the case
may be, shall pay such additional amounts ("Additional Amounts") as shall be
                                            ------------------              
necessary in order that the net amounts received by the Holders of the
Securities of any series who are not United States persons after such deduction
or withholding shall equal the amount that would have been 

                                       77
<PAGE>
 
receivable thereunder in the absence of such deduction or withholding, except
that no such Additional Amounts shall be payable on account of:

         (a) any Tax which would not have been so imposed but for (i) the
  existence of any present or former connection between such Holder (or between
  a fiduciary, settlor, beneficiary, member, shareholder of or possessor of a
  power over such Holder, if such Holder is an estate, a trust, a partnership or
  a corporation) and the United States or any political subdivision or taxing
  authority thereof or therein, including, without limitation, such Holder (or
  such fiduciary, settlor, beneficiary, member, shareholder or possessor) being
  or having been a citizen or resident of the United States or treated as a
  resident thereof, or being or having been engaged in trade or business or
  present therein, or having had a permanent establishment therein, (ii) such
  Holder's present or former status as a personal holding company, a foreign
  personal holding company with respect to the United States, a controlled
  foreign corporation, a passive foreign investment company, or a foreign
  private foundation or foreign tax exempt entity for United States tax
  purposes, or a corporation which accumulates earnings to avoid United States
  Federal income tax, or (iii) such holder's status as a bank extending credit
  pursuant to a loan agreement entered into in the ordinary course of business;

         (b) any Tax which would not have been so imposed but for the
  presentation by the Holder of such Security or any Coupon appertaining thereto
  for payment on a date more than 15 days after the date on which such payment
  became due and payable or the date on which payment thereof is duly provided
  for, whichever occurs later;

         (c) any estate, inheritance, gift, sales, transfer, personal property
  or similar Tax;

         (d) any Tax which would not have been imposed but for the failure to
  comply with any certification, identification or other reporting requirements
  concerning the nationality, residence, identity or connection with the United
  States of the Holder or beneficial owner of such Security or any Coupon
  appertaining thereto, if compliance is required by statute or by regulation or
  ruling of the United States Treasury Department as a precondition to exemption
  from such Tax;

         (e) any Tax which is payable otherwise than by deduction or withholding
  from payments of principal of, premium, if any, or interest on such Security;

         (f) any Tax imposed as a result of a Person's past or present actual or
  constructive ownership, including by virtue of the right to convert
  Securities, of 10% or more of the total combined voting power of all classes
  of stock of the Company entitled to vote;

         (g) any Tax required to be withheld by any Paying Agent from any
  payment of the principal of, premium, if any, or interest on such Security, if
  such payment can be made without such withholding by any other Paying Agent in
  Western Europe;

         (h) any Tax imposed on a Holder that is a partnership or a fiduciary,
  but only to the extent that any beneficial owner or member of the partnership
  or beneficiary or settlor

                                       78
<PAGE>
 
  with respect to the fiduciary would not have been entitled to the payment of
  Additional Amounts had the beneficial owner, member, beneficiary or settlor
  directly received its beneficial or distributive share of payments on such
  Security;

         (i) any Tax which would not have been imposed but for the fact that
  such Security constitutes a "United States real property interest," as defined
  in Section 897(c)(1) of the Internal Revenue Code and the regulations
  thereunder, with respect to the beneficial owner of such Security; or

         (j) any combination of items (a), (b), (c), (d), (e), (f), (g), (h) and
  (i).

         Notwithstanding the foregoing, if and so long as a certification,
identification or other information reporting requirement referred to in the
third paragraph of Section 1102 of this Indenture would be fully satisfied by
payment of a backup withholding tax or similar charge, the Company may elect, by
so stating in the Determination Notice (as hereinafter defined), to have the
provisions of this paragraph apply in lieu of redeeming the Security pursuant to
such Section 1102.  In such event, the Company will pay as Additional Amounts
such amounts as may be necessary so that every net payment made, following the
effective date of such requirements, outside the United States by the Company or
any Paying Agent of principal and premium, if any, due in respect of a Security,
or interest represented by any Coupon, the beneficial owner of which is not a
United States person (but without any requirement that the nationality,
residence or identity of such beneficial owner be disclosed to the Company, any
Paying Agent or any governmental authority), after deduction or withholding for
or on account of such backup withholding tax or similar charge, other than a
backup withholding tax or similar charge which is (a) the result of a
certification, identification or information reporting requirement described in
the first parenthetical clause of such third paragraph of Section 1102, (b)
imposed as a result of the fact that the Company or any Paying Agent has actual
knowledge that the beneficial owner of the Security or such Coupon is within the
category of Persons described in clause (a) of the preceding paragraph or (c)
imposed as a result of presentation of the Security or such Coupon for payment
more than 15 days after the date on which such payment becomes due and payable
or on which payment thereof is duly provided for, whichever occurs later, will
not be less than the amount provided for in the Security or such Coupon to be
then due and payable.

         Except as specifically provided in this Indenture, the Company shall
not be required to make any payment with respect to any Taxes.

     If the Company, the Guarantor or any successor to either of them under this
Indenture shall be incorporated under the laws of a jurisdiction other than the
United States, the Company or its successor will pay, and the Guarantor or its
successor will jointly and severally guarantee the payment of, and the Company
or the Guarantor shall provide notice to the Trustee of the payment of, such
additional amounts ("Other Additional Amounts") as may be necessary in order
                     ------------------------                               
that every net payment on each Security, after withholding for or on account of
any present or future tax, assessment or other governmental charge imposed upon
or as a result of such payment by such other jurisdiction (or any political
subdivision or taxing authority thereof or therein), will be not less than the
amount provided for in such Security to be then due and payable; provided,
                                                                 -------- 
however, that (i) the Other Additional Amounts payable to a Holder of a Security
- -------                                                                         
will be reduced

                                       79
<PAGE>
 
to the extent that such withholding reduces any tax liability to which such
Holder of the Security was and is subject both prior to and after such
incorporation in another jurisdiction and (ii) the exceptions listed in the
third preceding paragraph shall apply, substituting for the United States the
relevant jurisdiction that imposes the tax giving rise to the payment of Other
Additional Amounts.

     Whenever in this Indenture there is mentioned, in any context, the payment
of the principal of or any premium or interest on, or in respect of, any
Security of any series or any Coupon or the net proceeds received on the sale or
exchange of any Security of any series, such mention shall be deemed to include
mention of the payment of Additional Amounts provided by the terms of this
Indenture or by the terms of such series established hereby or pursuant hereto
to the extent that, in such context, Additional Amounts are, were or would be
payable in respect thereof pursuant to such terms, and express mention of the
payment of Additional Amounts (if applicable) in any provision hereof shall not
be construed as excluding Additional Amounts in those provisions hereof where
such express mention is not made.

     Except as otherwise provided in or pursuant to this Indenture or the
Securities of any series, if the Securities of a series provide for the payment
of Additional Amounts, at least 10 days prior to each date of payment of
principal or interest if any Additional Amounts will be payable in connection
therewith, the Company shall furnish to the Trustee and the principal Paying
Agents, if other than the Trustee, an Officers' Certificate which shall specify
by country the amount, if any, required to be withheld on such payments to such
Holders of Securities or Coupons, and the Company agrees to pay to the Trustee
or such Paying Agent the Additional Amounts required hereby or by the terms of
such Securities.  The Company covenants to indemnify the Trustee and any Paying
Agent and other officers, directors, employees and agents for, and to hold them
harmless against, any loss, liability or expense reasonably incurred without
negligence or bad faith on their part arising out of or in connection with
actions taken or omitted by any of them in reliance on any Officers' Certificate
furnished pursuant to this Section.

Section 1005.  Statement as to Compliance.
               -------------------------- 

     Each of the Company and the Guarantor will deliver to the Trustee, within
120 days after the end of each fiscal year of the Company and the Guarantor, as
the case may be, an Officers' Certificate, stating as to each signer, that

     (1) a review of the activities of the Company or the Guarantor, as the case
may be, during such year and of performance under this Indenture has been made
under his or her supervision; and

     (2) to the best of his or her knowledge, based on such review, (a) the
Company or the Guarantor, as the case may be, has fulfilled all its obligations
under this Indenture throughout such year, or, if there has been a material
default in the fulfillment of any such obligation, specifying each such default
known to him or her and the nature and status thereof, and (b) no event has
occurred and is continuing which is, or after notice or lapse of time or both
would become, an Event of Default, or, if such an event has occurred and is
continuing, specifying each such event known to him or her and the nature and
status thereof.

                                       80
<PAGE>
 
Section 1006.  Corporate Existence.
               ------------------- 

     Subject to Article Eight, the Company and the Guarantor will do or cause to
be done all things necessary to preserve and keep in full force and effect its
corporate existence.

                                ARTICLE ELEVEN

                           REDEMPTION OF SECURITIES

Section 1101.  Applicability of Article.
               ------------------------ 

     Redemption of Securities of any series at the option of the Company as
permitted or required in or pursuant to this Indenture or by the terms of such
Securities shall be made in accordance with the terms of this Indenture or such
Securities and (except as otherwise provided herein or pursuant hereto) this
Article Eleven.

Section 1102.  Election to Redeem; Notice to Trustee.
               ------------------------------------- 

     The election of the Company to redeem any Securities shall be evidenced by
or pursuant to a Board Resolution.  In case of any redemption at the election of
the Company of the Securities of any series, the Company shall, at least 75 days
prior to the Redemption Date fixed by the Company (unless a shorter notice shall
be satisfactory to the Trustee), notify the Trustee of such Redemption Date and
of the principal amount of Securities of such series to be redeemed.

         In addition, notwithstanding the above, if as a result of a Tax Law
Change, the Company has or will become obligated to pay to the Holder of any
Security or Coupon Additional Amounts, and such obligation cannot be avoided by
the Company taking reasonable measures available to it, then the Company may, at
its option, redeem the Tax Affected Securities as a whole, but not in part, upon
not less than 20 nor more than 60 days' notice to the Holders prior to the
Redemption Date therefor, at a Redemption Price equal to 100% of the principal
amount plus interest accrued to the Redemption Date, and any Additional Amounts
then payable; provided that (i) no such notice of redemption shall be given
              -------- ----                                                
earlier than 90 days prior to the earliest date on which the Company would be
obligated to pay any such Additional Amounts were a payment in respect of the
Tax Affected Securities then due and (ii) at the time such notice of redemption
is given, such obligation to pay such Additional Amounts remains in effect.
Prior to the publication of any notice of redemption pursuant to this paragraph,
the Company shall deliver to the Trustee (a) an Officers' Certificate stating
that the Company is entitled to effect such redemption and setting forth a
statement of facts showing that the conditions precedent to the right of the
Company so to redeem have occurred and (b) an Opinion of Counsel selected by the
Company to the effect that the Company has or will become obligated to pay such
Additional Amounts as a result of such Tax Law Change.  The Company's right to
redeem the Tax Affected Securities shall continue as long as the Company is
obligated to pay 

                                       81
<PAGE>
 
such Additional Amounts, notwithstanding that the Company shall have made
payments of Additional Amounts specified in Section 1004.

     In addition, if the Company determines, based upon an Opinion of Counsel,
that, as a result of a Tax Law Change, any payment made outside the United
States by the Company or any of its Paying Agents of the full amount of
principal, premium, if any, or interest due with respect to any Bearer Security
or Coupon appertaining thereto would be subject to any certification,
identification or other information reporting requirement of any kind, the
effect of which requirement is the disclosure to the Company, any Paying Agent
or any governmental authority of the nationality, residence or identity of a
beneficial owner of such Bearer Security or Coupon who is not a United States
person (other than such a requirement (a) which would not be applicable to a
payment made by the Company or any one of its Paying Agents (i) directly to the
beneficial owner or (ii) to any custodian, nominee or other agent of the
beneficial owner, (b) which can be satisfied by the custodian, nominee or other
agent certifying that such beneficial owner is not a United States person,
provided that, in each case referred to in clauses (a) (ii) and (b), payment by
- -------- ----                                                                  
such custodian, nominee or agent to such beneficial owner is not otherwise
subject to any such requirement, or (c) which would not be applicable but for
the fact that such Bearer Security constitutes a "United States real property
interest," as defined in Section 897(c)(1) of the Internal Revenue Code, with
respect to the beneficial owner of such Bearer Security), the Company at its
election will either (x) redeem the Bearer Securities, as a whole but not in
part, upon not less than 20 nor more than 60 days' notice prior to the
Redemption Date, at a Redemption Price equal to 100% of the principal amount
thereof plus interest accrued to the Redemption Date and any Additional Amounts,
or (y) if and so long as the certification, identification or other information
reporting requirement referred to above would be fully satisfied by payment of a
backup withholding tax or similar charge, pay the Holder the Additional Amounts
specified in Section 1004.  The Company will make such determination and
election and notify the Trustee and the Paying Agent in London, England thereof
in writing as soon as practicable, and the Trustee will promptly give notice of
such determination in the manner provided in Section 106 (the "Determination
                                                               -------------
Notice"), in each case stating the effective date of such certification,
- ------                                                                  
identification or information reporting requirement, whether the Company will
redeem the Bearer Securities or will pay the Additional Amounts specified in the
second paragraph of Section 1004 and (if applicable) the last date by which the
redemption of the Bearer Securities must take place.  If the Company elects to
redeem the Bearer Securities pursuant to clause (x) above, such redemption shall
take place on a date, not later than one year after the publication of the
Determination Notice, as the Company elects by notice in writing to the Trustee
and the Paying Agent in London at least 75 days before the Redemption Date,
unless shorter notice is acceptable to the Trustee.  Notwithstanding the
foregoing, the Company will not so redeem the Bearer Securities if the Company,
based upon an Opinion of Counsel which counsel shall be reasonably acceptable to
the Trustee, subsequently determines, not less than 20 days prior to the
Redemption Date, that subsequent payments would not be subject to any such
requirement, in which case the Company will notify the Trustee in writing of its
determination not to so redeem the Securities, and the Trustee will promptly
give notice to the Holders of the Bearer Securities of that determination and
any earlier redemption notice will thereupon be revoked and of no further
effect.  If the Company elects as provided in clause (y) above to pay Additional
Amounts, the Company may, as long as the Company is obligated to pay such
Additional Amounts, subsequently redeem the Bearer Securities, at any time, as a
whole but not 

                                       82
<PAGE>
 
in part, upon not less than 20 nor more than 60 days' notice prior to the
Redemption Date, at a Redemption Price equal to 100% of the principal amount
thereof plus interest accrued to the Redemption Date, and any Additional
Amounts.

Section 1103.  Selection by Trustee of Securities to be Redeemed.
               ------------------------------------------------- 

     If any Securities of any series are to be redeemed in part, the particular
Securities to be redeemed shall be selected not more than 60 days prior to the
Redemption Date by the Trustee from the Outstanding Securities of such series
not previously called for redemption, in compliance with the requirements of the
principal national securities exchange, if any, on which the Securities are
listed, or, if the Securities are not so listed, on a pro rata basis, by lot or
such other method as the Trustee shall deem fair and appropriate, under
circumstances intended not to discriminate between Registered and Bearer
Securities to be redeemed, and which may provide for the selection for
redemption of portions of the principal amount of Registered Securities of such
series; provided, however, that no such partial redemption shall reduce the
        --------  -------                                                  
portion of the principal amount of a Registered Security of such series not
redeemed to less than the minimum denomination for a Security of such series
established herein or pursuant hereto.  The Trustee shall have no liability in
connection with any selection of securities to redemption made in good faith and
without negligence.

     If any Registered Security selected for partial redemption, which is
convertible by the terms of such Security established pursuant to Section 301,
is converted in part before termination of the conversion right with respect to
the portion of the Security so selected, the converted portion of such Security
shall be deemed (so far as may be) to be the portion selected for redemption.
Securities which have been converted during a selection of Securities to be
redeemed may be treated by the Trustee as Outstanding for the purpose of such
selection.

     The Trustee shall promptly notify the Company and the Security Registrar
(if other than itself) in writing of the Securities selected for redemption and,
in the case of any Securities selected for partial redemption, the principal
amount thereof to be redeemed.

     For all purposes of this Indenture, unless the context otherwise requires,
all provisions relating to the redemption of Securities shall relate, in the
case of any Securities redeemed or to be redeemed only in part, to the portion
of the principal of such Securities which has been or is to be redeemed.

                                       83
<PAGE>
 
Section 1104.  Notice of Redemption.
               -------------------- 

     Notice of redemption shall be given by the Trustee in the manner provided
in Section 106, not less than 20 nor more than 60 days prior to the Redemption
Date, unless a different period is specified in the Securities to be redeemed.
All such redemption notices (except, in the case of a redemption specified in
the penultimate paragraph of Section 1102) shall be irrevocable.  Failure to
give notice by mailing in the manner herein provided to the Holder of any
Registered Securities designated for redemption as a whole or in part, or any
defect in the notice to any such Holder, shall not affect the validity of the
proceedings for the redemption of any other Securities or portion thereof.

     Any notice that is mailed to the Holder of any Registered Securities in the
manner herein provided shall be conclusively presumed to have been duly given,
whether or not such Holder receives the notice.

     All notices of redemption shall identify the Securities to be redeemed and
shall state:

     (1)  the Redemption Date,

     (2)  the Redemption Price, and accrued interest, if any,

     (3)  if less than all Outstanding Securities of any series are to be
redeemed, the identification (and, in the case of partial redemption, the
principal amount) of the particular Security or Securities to be redeemed,

     (4)  in case any Security is to be redeemed in part only, the notice which
relates to such Security shall state that on and after the Redemption Date, upon
surrender of such Security, the Holder of such Security will receive, without
charge, a new Security or Securities of authorized denominations for the
principal amount thereof remaining unredeemed,

     (5)  that, on the Redemption Date, the Redemption Price shall become due
and payable upon each such Security or portion thereof to be redeemed, and, if
applicable, that interest thereon shall cease to accrue on and after said date,

     (6)  if applicable, the Conversion Price, the date on which the right to
convert the Securities to be redeemed will terminate and the places where such
Securities, together with all unmatured Coupons and any matured Coupons in
default appertaining thereto, may be surrendered for conversion,

     (7)  the place or places where such Securities, together (in the case of
Bearer Securities) with all Coupons appertaining thereto, if any, maturing after
the Redemption Date, are to be surrendered for payment of the Redemption Price
and any accrued interest and Additional Amounts pertaining thereto,

     (8)  that the redemption is for a sinking fund, if such is the case,

                                       84
<PAGE>
 
     (9)  that, unless otherwise specified in such notice, Bearer Securities of
any series, if any, surrendered for redemption must be accompanied by all
Coupons maturing subsequent to the date fixed for redemption or the amount of
any such missing Coupon or Coupons will be deducted from the Redemption Price,
unless security or indemnity satisfactory to the Company, the Trustee and any
Paying Agent is furnished,

     (10) if Bearer Securities of any series are to be redeemed and any
Registered Securities of such series are not to be redeemed, and if such Bearer
Securities may be exchanged for Registered Securities not subject to redemption
on the Redemption Date pursuant to Section 305 or otherwise, the last date, as
determined by the Company, on which such exchanges may be made, and

     (11) the CUSIP number, ISIN number or the Euroclear or the Cedel reference
numbers of such Securities, if any (or any other numbers used by a Depository or
Common Depository to identify such Securities).

     Notice of redemption of Securities to be redeemed at the election of the
Company shall be given by the Company or, at the Company's request, by the
Trustee in the name and at the expense of the Company.

Section 1105.  Deposit of Redemption Price.
               --------------------------- 

     On or prior to 10:00 a.m., Eastern Time, on any Redemption Date, the
Company shall deposit, in immediately available funds, with respect to the
Securities of any series called for redemption pursuant to Section 1104, with
the Trustee or with a Paying Agent (or, if the Company is acting as its own
Paying Agent, segregate and hold in trust as provided in Section 1003) an amount
of money in Dollars sufficient to pay the Redemption Price of, and (except if
the Redemption Date shall be an Interest Payment Date, unless otherwise
specified pursuant to Section 301 for or in the Securities of such series) any
accrued interest on and Additional Amounts with respect thereto, all such
Securities or portions thereof which are to be redeemed on that date.

     If any Security called for redemption, which is convertible by the terms of
such Security established pursuant to Section 301, is converted, any money
deposited with the Trustee or with a Paying Agent or so segregated and held in
trust for the redemption of such Security shall (subject to any right of the
Holder of such Security or any predecessor Security to receive interest as
provided in Section 307) be paid to the Company on Company Request or, if then
held by the Company, shall be discharged from such trust.

Section 1106.  Securities Payable on Redemption Date.
               ------------------------------------- 

     Notice of redemption having been given as aforesaid, the Securities so to
be redeemed shall, on the Redemption Date, become due and payable at the
Redemption Price therein specified, and from and after such date (unless the
Company shall default in the payment of the Redemption Price and accrued
interest) such Securities shall cease to bear interest and the Coupons for such
interest appertaining to any Bearer Securities so to be redeemed, except to the

                                       85
<PAGE>
 
extent provided below, shall be void.  Upon surrender of any such Security for
redemption in accordance with said notice, together with all Coupons, if any,
appertaining thereto maturing after the Redemption Date, such Security shall be
paid by the Company at the Redemption Price, together with any accrued interest
and Additional Amounts to the Redemption Date; provided, however, that, except
                                               --------  -------              
as otherwise provided in or pursuant to this Indenture or the Bearer Securities
of such series, installments of interest on Bearer Securities whose Stated
Maturity is on or prior to the Redemption Date shall be payable only upon
presentation and surrender of Coupons for such interest (at an Office or Agency
located outside the United States except as otherwise provided in Section 1002),
and provided, further, that, except as otherwise specified in or pursuant to
    --------  -------                                                       
this Indenture or the Registered Securities of such series, installments of
interest on Registered Securities whose Stated Maturity is on or prior to the
Redemption Date shall be payable to the Holders of such Securities, or one or
more Predecessor Securities, registered as such at the close of business on the
Regular Record Dates therefor according to their terms and the provisions of
Section 307.

     If any Bearer Security surrendered for redemption shall not be accompanied
by all appurtenant Coupons maturing after the Redemption Date, such Security may
be paid after deducting from the Redemption Price an amount equal to the face
amount of all such missing Coupons, or the surrender of such missing Coupon or
Coupons may be waived by the Company and the Trustee if there be furnished to
them such security or indemnity as they may require to save each of them and any
Paying Agent harmless.  If thereafter the Holder of such Security shall
surrender to the Trustee or any Paying Agent any such missing Coupon in respect
of which a deduction shall have been made from the Redemption Price, such Holder
shall be entitled to receive the amount so deducted; provided, however, that any
                                                     --------  -------          
interest or Additional Amounts represented by Coupons shall be payable only upon
presentation and surrender of those Coupons at an Office or Agency for such
Security located outside of the United States except as otherwise provided in
Section 1002.

     If any Security called for redemption shall not be so paid upon surrender
thereof for redemption, the principal and any premium, until paid, shall bear
interest from the Redemption Date at the rate prescribed therefor in the
Security and each Security shall remain convertible (if applicable) until the
principal of such Security (or portion thereof, as the case may be) shall have
been paid or duly provided for.

Section 1107.  Securities Redeemed in Part.
               --------------------------- 

     Any Security which is to be redeemed only in part shall be surrendered at
any applicable Office or Agency for such Security (with, if the Company or the
Trustee so requires, due endorsement by, or a written instrument of transfer in
form satisfactory to the Company and the Trustee duly executed by, the Holder
thereof or his attorney duly authorized in writing) and the Company shall
execute, the Guarantees of the Guarantor shall be endorsed on and the Trustee
shall authenticate and deliver to the Holder of such Security without service
charge, a new Security or Securities of the same series, containing identical
terms and provisions, of any authorized denomination as requested by such Holder
in aggregate principal amount equal to and in exchange for the unredeemed
portion of the principal of the Security so surrendered.  If a Security in
global form is so surrendered, the Company shall execute, and the Trustee shall

                                       86
<PAGE>
 
authenticate and deliver to the U.S. Depository or other Depository or Common
Depository for such Security in global form as shall be specified in the Company
Order with respect thereto to the Trustee, without service charge, a new
Security in global form in a denomination equal to and in exchange for the
unredeemed portion of the principal of the Security in global form so
surrendered.


                                ARTICLE TWELVE


                           CONVERSION OF SECURITIES


Section 1201.  Conversion Privilege and Conversion Price.
               ----------------------------------------- 

     Conversion of Securities of any series at the option of the Holder thereof
as permitted by the terms of such Securities shall be made in accordance with
the terms of such Securities and (except as otherwise provided herein or
pursuant hereto) this Article Twelve. Each reference in this Article Twelve to
"a Security" or "the Securities" refers to the Securities of the particular
series that are convertible into shares of Common Stock. At the option of the
Holder any Security other than the temporary global Bearer Security may be
converted into fully paid and nonassessable shares (calculated as to each
conversion to the nearest 1/100th of a share) of Common Stock of the Company at
the Conversion Price (as defined below) in effect at the time of conversion. The
period for conversion shall be set forth in the terms of the Securities. In case
a Security or portion thereof is called for redemption or is delivered for
repayment, such conversion right in respect of the Security or portion so called
or delivered shall expire at the close of business on the fifth Business Day
preceding the Redemption Date or the second Business Day preceding a repayment
on the Securities Repayment Date (as set forth in Article Fifteen), as the case
may be, unless the Company defaults in making the payment due upon redemption or
repayment, as the case may be.

     The price at which shares of Common Stock shall be delivered upon
conversion (herein called the "Conversion Price") shall be as set forth in the
                               ----------------                               
terms of the Securities.  The Conversion Price shall be adjusted in certain
instances as provided in this Article Twelve.

     Upon presentment for conversion of any Securities pursuant to this Section
1201, the applicable Conversion Agent shall that day notify the Company of such
presentment. The Company shall deliver to such Holder, through the Conversion
Agent, as promptly as practicable on or after the Conversion Date, the
certificates representing the number of shares of Common Stock to be delivered,
and cash in lieu of any fractional shares. No payment or adjustment shall be
made upon any conversion on account of any dividends on the Common Stock issued
upon conversion.

Section 1202.  Exercise of Conversion Privilege.
               -------------------------------- 

     In order to exercise the conversion privilege, the Holder of any Definitive
Security to be converted shall surrender such Security, duly endorsed or
assigned to the Company or in blank (in the case of any Registered Security), at
any applicable Place of Conversion, accompanied by a duly signed and completed
conversion notice substantially in the form attached hereto as 

                                       87
<PAGE>
 
Exhibit C stating that the Holder elects to convert such Security or, if less
- ---------
than the entire principal amount thereof is to be converted, the portion thereof
to be converted. Each Bearer Security surrendered for conversion must be
surrendered together with all Coupons appertaining thereto that mature after the
Conversion Date. If any Bearer Security surrendered for conversion shall not be
accompanied by all such appurtenant Coupons, the surrender of any or all of such
missing Coupons may be waived by the Company, the Guarantor and the Trustee, if
there be furnished to them such security or indemnity as they may require to
save each of them and any Paying Agent harmless. Matured Coupons not in default
(including Coupons maturing on the Conversion Date) will be payable against
surrender thereof, and matured Coupons previously surrendered and in default
will continue to be payable, notwithstanding the exercise of the right of
conversion by the Holder of the Security to which the Coupon appertains. Accrued
interest from the immediately preceding Interest Payment Date until the
Conversion Date (and Additional Amounts, if any, thereon) will be paid, through
the Paying Agent, in the same manner as regular payments of interest and as
provided in Section 307, within five Business Days after the Conversion Date.
The Company's delivery to the Holder of the fixed number of shares of Common
Stock into which a Definitive Security is convertible will be deemed to satisfy
the Company's obligation to pay the principal amount of the Security.

     Definitive Securities shall be deemed to have been converted immediately
prior to the close of business on the day of surrender of such Securities for
conversion (accompanied by a duly signed and completed conversion notice as
contemplated above) in accordance with the foregoing provisions, and at such
time the rights of the Holders of such Securities as Holders shall cease, and
the Person or Persons entitled to receive the Common Stock issuable upon
conversion shall be treated for all purposes as the record holder or holders of
such Common Stock at such time. Subject to Section 1201, as promptly as
practicable on or after the Conversion Date, the Company shall issue and deliver
to the Trustee, for delivery to the Holder, a certificate or certificates for
the number of full shares of Common Stock issuable upon conversion, together
with payment in lieu of any fraction of a share, as provided in Section 1203.

     In the case of any Security which is converted in part only, upon such
partial conversion the Company shall execute, the Guarantees of the Guarantor
shall be endorsed thereon and the Trustee shall authenticate and deliver to the
Holder thereof, at the expense of the Company, a new Security or Securities of
authorized denominations in an aggregate principal amount equal to and in
exchange for the unconverted portion of the principal amount of such Security. A
Security may be converted in part, but only if the principal amount of such
Security to be converted is any integral multiple of U.S. $1,000 and the
principal amount of such security to remain Outstanding after such conversion is
equal to U.S. $1,000 or any integral multiple of $1,000 in excess thereof.

Section 1203.  Fractions of Shares.
               ------------------- 

     No fractional shares of Common Stock shall be issued upon conversion of any
Definitive Security. If more than one Definitive Security shall be surrendered
for conversion at one time by the same Holder, the number of full shares which
shall be issuable upon conversion thereof shall be computed on the basis of the
aggregate principal amount of the Definitive Securities (or specified portions
thereof) so surrendered. Instead of any fractional share of Common Stock 

                                       88
<PAGE>
 
which would otherwise be issuable upon conversion of any Definitive Security or
Securities (or specified portions thereof), the Company shall calculate and pay
a cash adjustment in respect of such fraction (calculated to the nearest 1/100th
of a share) in an amount equal to the same fraction of the Closing Price Per
Share at the close of business on the Conversion Date. Such cash payments shall,
in the case of a conversion of Bearer Securities, be made to an address outside
of the United States.

Section 1204.  Adjustment of Conversion Price.
               ------------------------------ 

     The Conversion Price shall be subject to adjustment from time to time as
follows:


          (1)  In case the Company shall pay or make a dividend or other
distribution on any class of capital stock of the Company in shares of Common
Stock, the Conversion Price in effect at the opening of business on the day
following the date fixed for the determination of stockholders entitled to
receive such dividend or other distribution shall be reduced so that the same
shall equal the price determined by multiplying such Conversion Price by a
fraction of which the numerator shall be the number of shares of Common Stock
outstanding at the close of business on the date fixed for such determination
and the denominator shall be the sum of such number of shares and the total
number of shares of Common Stock constituting such dividend or other
distribution, such reduction to become effective at the opening of business on
the day following the date fixed for such determination. For the purposes of
this paragraph (1), the number of shares of Common Stock at any time outstanding
shall not include shares held in the treasury of the Company but shall include
shares issuable in respect of scrip certificates issued in lieu of fractions of
shares of Common Stock.

          (2)  In case at any time the Company shall issue rights, options or
warrants to all holders of its Common Stock entitling them to subscribe for or
purchase shares of Common Stock at a price per share less than the then current
market price per share (determined as provided in paragraph (6) of this Section)
of the Common Stock on the date fixed for the determination of stockholders
entitled to receive such rights, options or warrants, the Conversion Price in
effect at the opening of business on the day following the date fixed for such
determination shall be reduced so that the same shall equal the price determined
by multiplying such Conversion Price by a fraction of which the numerator shall
be the number of shares of Common Stock outstanding at the close of business on
the date fixed for such determination plus the number of shares of Common Stock
which the aggregate of the offering price of the total number of shares of
Common Stock so offered for subscription or purchase would purchase at such
current market price and the denominator shall be the number of shares of Common
Stock outstanding at the close of business on the date fixed for such
determination plus the number of shares of Common Stock so offered for
subscription or purchase, such reduction to become effective at the opening of
business on the day following the date fixed for such determination; provided,
                                                                     -------- 
however, that if an adjustment to the Conversion Price is made and any or all of
- -------                                                                         
such rights, options and warrants are not exercised, then a corresponding
reversing adjustment of the Conversion Price shall be made, on an equitable
basis, to take account of such event.  For the purposes of this paragraph (2),
the number of shares of Common Stock at any time outstanding shall not include
shares held in the treasury of the Company but shall include shares issuable in
respect of scrip certificates issued in lieu of fractions of shares of Common
Stock.

                                       89
<PAGE>
 
          (3)  In case outstanding shares of Common Stock shall be subdivided
into a greater number of shares of Common Stock, the Conversion Price in effect
at the opening of business on the day following the day upon which such
subdivision becomes effective shall be proportionately reduced, and, conversely,
in case outstanding shares of Common Stock shall each be combined into a smaller
number of shares of Common Stock, the Conversion Price in effect at the opening
of business on the day following the day upon which such combination becomes
effective shall be proportionately increased, such reduction or increase, as the
case may be, to become effective at the opening of business on the day following
the day upon which such subdivision or combination becomes effective.

          (4)  In case the Company shall, by dividend or otherwise, distribute
to all holders of its Common Stock evidences of its indebtedness, shares of any
class of capital stock, cash or assets (including securities, but excluding any
(i) rights, options or warrants referred to in paragraph (2) of this Section,
(ii) any dividend or distribution paid exclusively in cash out of the
consolidated retained earnings of the Company, (iii) any dividend or
distribution referred to in paragraph (1) of this Section and (iv) shares issued
upon any merger or consolidation to which Section 1211 applies), the Conversion
Price shall be adjusted so that the same shall equal the price determined by
multiplying the Conversion Price in effect immediately prior to the close of
business on the date fixed for the determination of stockholders entitled to
receive such distribution by a fraction of which the numerator shall be the
current market price per share (determined as provided in paragraph (6) of this
Section) of the Common Stock on the date fixed for such determination less the
then fair market value (as determined by the Board of Directors of the Company,
whose determination shall be conclusive and described in a Company Board
Resolution filed with the Trustee) of the portion of the assets, shares or
evidences of indebtedness so distributed applicable to one share of Common Stock
and the denominator shall be such current market price per share of the Common
Stock, such adjustment to become effective at the opening of business on the day
following the date fixed for the determination of stockholders entitled to
receive such distribution. If the Conversion Price is adjusted because of the
distribution of rights, options or warrants, then, upon the expiration of any
such unexercised right, option or warrant, the Conversion Price shall be
adjusted to equal the Conversion Price that would have applied had such right,
option or warrant never been distributed.

          (5)  The reclassification of Common Stock into securities including
other than Common Stock (other than any reclassification upon a consolidation or
merger to which Section 1211 applies) shall be deemed to involve (a) a
distribution of such securities other than Common Stock to all holders of Common
Stock (and the effective date of such reclassification shall be deemed to be
"the date fixed for the determination of stockholders entitled to receive such
distribution" and "the date fixed for such determination" within the meaning of
paragraph (4) of this Section), and (b) a subdivision or combination, as the
case may be, of the number of shares of Common Stock outstanding immediately
prior to such reclassification into the number of shares of Common Stock
outstanding immediately thereafter (and the effective date of such
reclassification shall be deemed to be "the day upon which such subdivision
becomes effective" or "the day upon which such combination becomes effective,"
as the case may be, and "the day upon which such subdivision or combination
becomes effective," within the meaning of paragraph (3) of this Section).

                                       90
<PAGE>
 
          (6)  For the purpose of any computation under paragraphs (2) and (4)
of this Section 1204, the current market price per share of Common Stock on any
date shall be calculated by the Company and be deemed to be the average of the
daily Closing Prices Per Share for the five consecutive Trading Days selected by
the Company commencing not more than 10 Trading Days before, and ending not
later than, the earlier of the day in question and the day before the "ex date"
with respect to the issuance or distribution requiring such computation. For
purposes of this paragraph, the term "ex date," when used with respect to any
issuance or distribution, means the first date on which the Common Stock trades
regular way in the applicable securities market or on the applicable securities
exchange without the right to receive such issuance or distribution.

          (7)  No adjustment in the Conversion Price shall be required unless
such adjustment (plus any adjustments not previously made by reason of this
paragraph (7)) would require an increase or decrease of at least one percent in
such Conversion Price; provided, however, that any adjustments which by reason
                       --------  -------                                      
of this paragraph (7) are not required to be made shall be carried forward and
taken into account in any subsequent adjustment.  All calculations under this
Article shall be made to the nearest cent or to the nearest one-thousandth of a
share, as the case may be.

          (8)  The Company may make such reductions in the Conversion Price, for
the remaining term of any series of Securities or any shorter term, in addition
to those required by paragraphs (1), (2), (3) and (4) of this Section 1204, as
it considers to be advisable in order to avoid or diminish any income tax to any
holders of shares of Common Stock resulting from any dividend or distribution of
stock or issuance of rights or warrants to purchase or subscribe for stock or
from any event treated as such for income tax purposes.

Section 1205.  Notice of Adjustments of Conversion Price.
               ----------------------------------------- 

               Whenever the Conversion Price is adjusted as herein provided:

               (1)  the Company shall compute the adjusted Conversion Price in
accordance with Section 1204 and shall prepare a certificate signed by the
Treasurer of the Company setting forth the adjusted Conversion Price and showing
in reasonable detail the facts upon which such adjustment is based, and such
certificate shall promptly be filed with the Trustee and with each Conversion
Agent; and

               (2)  a notice stating that the Conversion Price has been adjusted
and setting forth the adjusted Conversion Price shall forthwith be required, and
as soon as practicable after it is required, such notice shall be provided by
the Company to all Holders in accordance with Section 106.

     Neither the Trustee nor any Conversion Agent shall be under any duty or
responsibility with respect to any such certificate or the information and
calculations contained therein, except to exhibit the same to any Holder of
Securities desiring inspection thereof at its office during normal business
hours.

                                       91
<PAGE>
 
Section 1206.  Notice of Certain Corporate Action.
               ---------------------------------- 

     In case:

               (a)  the Company shall declare a dividend (or any other
     distribution) on its Common Stock payable otherwise than exclusively in
     cash out of the consolidated retained earnings of the Company; or

               (b)  the Company shall authorize the granting to the holders of
     its Common Stock of rights, options or warrants to subscribe for or
     purchase any shares of capital stock of any class or of any other rights
     (other than rights, options or warrants to subscribe for or purchase any
     shares of capital stock of any class or of any other rights of a
     corporation, a majority of each class of common stock of which is owned,
     directly or indirectly, by the Company or the Guarantor); or

               (c)  of any reclassification of the Common Stock of the Company
     (other than a subdivision or combination of its outstanding shares of
     Common Stock), or of any consolidation or merger to which the Company is a
     party and for which approval of the stockholders of the Company is required
     pursuant to applicable corporate law, or of the sale or transfer of all or
     substantially all of the assets of the Company; or

               (d)  of the voluntary or involuntary dissolution, liquidation or
     winding up of the Company;

then the Company shall cause to be filed at each office or agency maintained for
the purpose of conversion of Securities pursuant to Section 1002, and shall
cause to be provided to all Holders in accordance with Section 106, at least 20
days (or 10 days in any case specified in clause (a) or (b) above) prior to the
applicable record or effective date hereinafter specified, a notice stating (y)
the date on which a record is to be taken for the purpose of such dividend,
distribution, rights, options or warrants, or, if a record is not to be taken,
the date as of which the holders of Common Stock of record to be entitled to
such dividend, distribution, rights, options or warrants are to be determined,
or (z) the date on which such reclassification, consolidation, merger, share
exchange, conveyance, transfer, sale, lease, dissolution, liquidation or winding
up is expected to become effective, and the date as of which it is expected that
holders of Common Stock of record shall be entitled to exchange their shares of
Common Stock for securities, cash or other property deliverable upon such
reclassification, consolidation, merger, share exchange, conveyance, transfer,
sale, lease, dissolution, liquidation or winding up.  If at the time the Trustee
shall not be the Conversion Agent, a copy of such notice and any notice referred
to in the following paragraph shall also forthwith be filed by the Company with
the Trustee.

Section 1207.  Company to Reserve Common Stock.
               ------------------------------- 

     The Company shall at all times reserve and keep available, free from
preemptive rights, out of its authorized but unissued Common Stock, for the
purpose of effecting the conversion of 

                                       92
<PAGE>
 
Securities of any series, the full number of shares of Common Stock then
issuable upon the conversion of all Outstanding Securities of such series.

Section 1208.  Taxes on Conversions.
               -------------------- 

     The Company will pay any and all stamp and similar taxes and duties that
may be payable in respect of the issue or delivery of shares of Common Stock on
conversion of Securities pursuant hereto.  The Company shall not, however, be
required to pay any tax which may be payable in respect of any transfer involved
in the issue and delivery of shares of Common Stock in a name other than that of
the Holder of the Security or Securities to be converted, and no such issue or
delivery shall be made unless and until the Person requesting such issue has
paid to the Company the amount of any such tax, or has established to the
satisfaction of the Company that such tax has been paid.

Section 1209.  Covenant as to Common Stock.
               --------------------------- 

     The Company agrees that all shares of Common Stock which may be delivered
upon conversion of Securities, upon such delivery, will have been duly
authorized and validly issued and will be fully paid and nonassessable and,
except as provided in Section 1208, the Company will pay all stamp and similar
taxes, liens and charges with respect to the issue thereof.

Section 1210.  Cancellation of Converted Securities.
               ------------------------------------ 

     All Securities delivered for conversion shall be delivered to the Trustee
or the Paying Agent or its agent to be canceled by or at the direction of the
Trustee, which shall dispose of the same as provided in Section 309.

Section 1211.  Provision in Case of Consolidation, Merger or Sale of Assets.
               ------------------------------------------------------------ 

     In case of any consolidation of the Company with, or merger of the Company
into, any other Person, any merger of another Person into the Company (other
than a merger which does not result in any reclassification, conversion,
exchange or cancellation of outstanding shares of Common Stock of the Company)
or any sale or transfer of all or substantially all of the assets of the
Company, the Person formed by such consolidation or resulting from such merger
or which acquires such assets, as the case may be, shall execute and deliver to
the Trustee a supplemental indenture providing that the Holder of each Security
then Outstanding shall have the right thereafter, during the period such
Security shall be convertible as specified in Section 1201, to convert such
Security only into the kind and amount of securities, cash and other property
receivable upon such consolidation, merger, sale or transfer by a holder of the
number of shares of Common Stock of the Company into which such Security might
have been converted immediately prior to such consolidation, merger, sale or
transfer (assuming such holder of Common Stock failed to exercise any rights of
election and that such Security was then convertible). Such supplemental
indenture shall provide for adjustments which, for events subsequent to the
effective date of such supplemental indenture, shall be as nearly equivalent as
may be practicable to the adjustments provided for in this Article Twelve.  If
in the case of any such consolidation, merger, sale or transfer, the stock or
other securities and property receivable 

                                       93
<PAGE>
 
by a Holder of the Securities includes stock or other securities and property of
a corporation other than the successor or purchasing corporation, then such
supplemental indenture shall also be executed by such other corporation and
shall contain such additional provisions to protect the interests of the Holders
of the Securities as the Board of Directors of the Company shall reasonably
consider necessary. The above provisions of this Section 1211 shall similarly
apply to successive consolidations, mergers, sales or transfers. Notice of the
execution of such a supplemental indenture shall be given by the Company to the
Holder of each Security as provided in Section 106 promptly upon such execution.
 

Section 1212.  Compliance with Governmental Requirements.  The Company covenants
               -----------------------------------------                        
that if any shares of Common Stock required to be reserved for purposes of
conversion of Securities hereunder require registration or listing with or
approval of any governmental authority under any Federal or State law, pursuant
to the Securities Act or the Exchange Act , or any national or regional
securities exchange or other trading market on which the Common Stock is listed
at the time of delivery of any Common Stock, before such shares may be issued
upon conversion, the Company will use its best efforts to cause such shares to
be duly registered, listed or approved, as the case may be.


                               ARTICLE THIRTEEN


                                 SINKING FUNDS


Section 1301.  Applicability of Article.
               ------------------------ 

     The provisions of this Article Thirteen shall be applicable to any sinking
fund for the retirement of Securities of a series, except as otherwise permitted
or required in or pursuant to this Indenture or any Security of such series
issued pursuant to this Indenture.

     The minimum amount of any sinking fund payment provided for by the terms of
Securities of any series is herein referred to as a "mandatory sinking fund
payment," and any payment in excess of such minimum amount provided for by the
terms of Securities of such series is herein referred to as an "optional sinking
fund payment."  If provided for by the terms of Securities of any series, the
cash amount of any sinking fund payment may be subject to reduction as provided
in Section 1302.  Each sinking fund payment shall be applied to the redemption
of Securities of any series as provided for by the terms of Securities of such
series and this Indenture.

Section 1302.  Satisfaction of Sinking Fund Payments With Securities.
               ----------------------------------------------------- 

     The Company or the Guarantor may, in satisfaction of all or any part of any
sinking fund payment with respect to the Securities of any series to be made
pursuant to the terms of such Securities (1) deliver Outstanding Securities of
such series (other than any of such Securities previously called for redemption
or any of such Securities in respect of which cash shall have been released to
the Company), together in the case of any Bearer Securities of such series with

                                       94
<PAGE>
 
all unmatured Coupons appertaining thereto, and (2) apply as a credit Securities
of such series which have been redeemed either at the election of the Company
pursuant to the terms of such series of Securities or through the application of
permitted optional sinking fund payments pursuant to the terms of such
Securities, provided that such Securities have not been previously so credited.
            -------- ----                                                      

     Such Securities shall be received and credited for such purpose by the
Trustee at the Redemption Price specified in such Securities for redemption
through operation of the sinking fund and the amount of such sinking fund
payment shall be reduced accordingly. If as a result of the delivery or credit
of Securities of any series in lieu of cash payments pursuant to this Section
1302, the principal amount of Securities of such series to be redeemed in order
to exhaust the aforesaid cash payment shall be less than $100,000, the Trustee
need not call Securities of such series for redemption, except upon Company
Request, and such cash payment shall be held by the Trustee or a Paying Agent
and applied to the next succeeding sinking fund payment, provided, however, that
                                                         --------  -------      
the Trustee or such Paying Agent shall at the request of the Company from time
to time pay over and deliver to the Company any cash payment so being held by
the Trustee or such Paying Agent upon delivery by the Company to the Trustee of
Securities of that series purchased by the Company having an unpaid principal
amount equal to the cash payment requested to be released to the Company.

Section 1303.  Redemption of Securities for Sinking Fund.
               ----------------------------------------- 

     Not less than 75 days prior to each sinking fund payment date for any
series of Securities, the Company shall deliver to the Trustee an Officers'
Certificate specifying the amount of the next ensuing mandatory sinking fund
payment for that series pursuant to the terms of that series, the portion
thereof, if any, which is to be satisfied by payment of cash and the portion
thereof, if any, which is to be satisfied by delivering and crediting of
Securities of that series pursuant to Section 1302, and the optional amount, if
any, to be added in cash to the next ensuing mandatory sinking fund payment, and
will also deliver to the Trustee any Securities to be so credited and not
theretofore delivered. If such Officers' Certificate shall specify an optional
amount to be added in cash to the next ensuing mandatory sinking fund payment,
the Company shall thereupon be obligated to pay the amount therein specified.

     Not more than 75 days or less than 45 days before each such sinking fund
payment date the Trustee shall select the Securities to be redeemed upon such
sinking fund payment date in the manner specified in Section 1103 and cause
notice of the redemption thereof to be given in the name of and at the expense
of the Company in the manner provided in Section 1104. Such notice having been
duly given, the redemption of such Securities shall be made upon the terms and
in the manner stated in Sections 1106 and 1107.

                                       95
<PAGE>
 
                               ARTICLE FOURTEEN


                                  GUARANTEES


Section 1401.  Guarantees.
               ---------- 

     Except as otherwise contemplated by Section 1403 below and subject to
Article Eighteen, the Guarantor hereby unconditionally guarantees to each Holder
of a Security authenticated and delivered by the Trustee, and to the Trustee on
behalf of such Holder, the due and punctual payment of the principal of and any
premium and interest on and any Additional Amounts, if any, on such Security and
the due and punctual payment of any sinking fund or analogous payments provided
for pursuant to the terms of such Security, when and as the same shall become
due and payable, whether at the Stated Maturity, by declaration of acceleration,
call for redemption, repayment at the option of the Holder or otherwise, in
accordance with the terms of such Security and of this Indenture, and whether or
not such payment is prohibited by the subordination provisions of Article
Seventeen and any and all other amounts owed by the Company to the Trustee under
the terms of this Indenture.  The Guarantor further unconditionally guarantees
to the Trustee the Company's obligations under Section 606 herein.  In case of
the failure of the Company punctually to make any such payment, the Guarantor
hereby agrees to cause such payment to be made punctually when and as the same
shall become due and payable, whether at the Stated Maturity or by declaration
of acceleration, call for redemption, repayment at the option of the Holder or
otherwise, and whether or not such payment is prohibited by the subordination
provisions of Article Seventeen and as if such payment were made by the Company,
subject to Article Eighteen.

     The Guarantor hereby agrees that its obligations hereunder shall be
unconditional (subject to Article Eighteen), irrespective of the validity,
regularity or enforceability of such Security or this Indenture, the absence of
any action to enforce the same, any waiver or consent by the Holder of such
Security or by the Trustee with respect to any provisions thereof or of this
Indenture (subject to Article Nine), the obtaining of any judgment against the
Company or any action to enforce the same or any other circumstances which might
otherwise constitute a legal or equitable discharge or defense of a guarantor.
The Guarantor hereby waives the benefits of diligence, presentment, demand of
payment, filing of claims with a court in the event of insolvency or bankruptcy
of the Company, any right to require a proceeding first against the Company,
protest or notice with respect to such Security or the indebtedness evidenced
thereby or with respect to any sinking fund payment required pursuant to the
terms of such Security and all demands whatsoever, and covenants that the
Guarantees will not be discharged in respect of such Security except by complete
performance of the obligations contained in such Guarantee. The Guarantor hereby
agrees that, in the event of a default in payment of principal (or premium, if
any) or interest or Additional Amounts, if any, on such Security, or a default
in any sinking fund or analogous payment referred to therein, legal proceedings
may be instituted by the Trustee on behalf of, or by, the Holder of such
Security, on the terms and conditions set forth in this Indenture, directly
against the Guarantor to enforce the Guarantees without first proceeding against
the Company.

                                       96
<PAGE>
 
     The Guarantor shall be subrogated to all rights of the Holders of the
Securities of a particular series against the Company in respect of any amounts
paid by the Guarantor on account of such Security pursuant to the provisions of
the Guarantees or this Indenture; provided, however, that the Guarantor shall
                                  --------  -------                          
not be entitled to enforce or to receive any payments arising out of, or based
upon, such right of subrogation until the principal of (and premium, if any) and
interest and Additional Amounts, if any, on all Securities of such series issued
hereunder shall have been paid in full.

Section 1402.  Execution and Delivery of Guarantees.
               ------------------------------------ 

     The Guarantees to be endorsed on the Securities of each series shall be in
substantially the form of Exhibit A hereto (except that references to premium
                          ---------                                          
and interest need be included only if any premium or interest, respectively, is
provided for in the terms of such series) and any other terms that may be set
forth in the form established pursuant to Section 202 with respect to such
series. The Guarantor hereby agrees to execute the Guarantees, in a form
established pursuant to Section 202, to be endorsed on each Security
authenticated and delivered by the Trustee.
 
     The Guarantees shall be executed on behalf of the Guarantor by its Chairman
of the Board, a Vice Chairman of the Board, its President or one of its Vice
Presidents, under its corporate seal reproduced thereon attested by its
Secretary or one of its Assistant Secretaries.  The signature of any of these
officers on the Guarantees may be manual or facsimile.

     Guarantees bearing the manual or facsimile signatures of individuals who
were at any time the proper officers of the Guarantor shall bind the Guarantor,
notwithstanding that such individuals or any of them have ceased to hold such
offices prior to the authentication and delivery of such Guarantees or did not
hold such offices at the date of such Guarantees.

     The delivery of any Security by the Trustee, after the authentication
thereof hereunder, shall constitute due delivery of the Guarantee endorsed
thereon on behalf of the Guarantor.  The Guarantor hereby agrees that its
Guarantee set forth in Section 1401 shall remain in full force and effect
notwithstanding any failure to endorse a Guarantee on any Security.

Section 1403.  Guarantees Optional.
               ------------------- 

     Notwithstanding anything to the contrary in this Indenture, if so provided
in the terms of any series of Securities, such series of Securities may be
issued without the Guarantees contemplated by this Article Fourteen.  In such
case, any and all references to the "Guarantees" or the "Guarantor" (including
the provisions relating thereto) throughout this Indenture shall be inapplicable
to such series.

                                       97
<PAGE>
 
                                ARTICLE FIFTEEN

                      REPAYMENT AT THE OPTION OF HOLDERS

     Section 1501.  Applicability Of Article.  Repayment of Securities of any
                    ------------------------                                 
series that are convertible into Common Stock pursuant to Article Twelve before
their Stated Maturity at the option of Holders thereof shall be made in
accordance with the terms of such Securities, if any, and (except as otherwise
specified by the terms of such series established pursuant to Section 301) in
accordance with this Article Fifteen.

     Section 1502.  Repayment Of Securities. Securities of any series subject to
                    -----------------------                                     
repayment in whole or in part (which shall be in a principal amount hereof which
is U.S. $1,000 or an integral multiple thereof) at the option of the Holders
thereof on any Repayment Date (as defined below) will, unless otherwise provided
in the Company's Board Resolutions or Officers' Certificate establishing such
series, be repaid at a price equal to the principal amount thereof, together
with interest and Additional Amounts, if any (the "Repayment Price"), if a
                                                   ---------------        
Repayment Event shall occur or have occurred.  For purposes hereof a "Repayment
                                                                      ---------
Event" shall have occurred if the Common Stock (or other equity securities into
- -----                                                                          
which such series of Securities is then convertible) is neither listed for
trading on a United States national securities exchange, the Nasdaq National
Market nor approved for trading on an established automated over-the-counter
trading market in the United States.  The "Repayment Date" with respect to any
                                           --------------                     
Repayment Event shall be the ninetieth (90th) day after the later of the
Exchange Date or the date a Repayment Event has occurred.  The Company covenants
that at or prior to 10:00 a.m., Eastern Time, on the Repayment Date it will
deposit with the Trustee or with a Paying Agent (or, if the Company is acting as
its own Paying Agent, segregate and hold in trust as provided in Section 1003)
an amount of money in Dollars sufficient to pay the principal (or, if so
provided by the terms of the Securities of any series, a percentage of the
principal) of, and (except if the Repayment Date shall be an Interest Payment
Date) accrued interest and Additional Amounts, if any, on, all the Securities or
portions thereof, as the case may be, to be repaid on such date.

     Section 1503.  Notice of Repayment.  Unless the Company shall have
                    -------------------                                
theretofore called for redemption all of the Outstanding Securities of such
series, on or before the 30th day after the later of the Exchange Date and the
occurrence of a Repayment Event, the Company or, at the request and expense of
the Company, the Trustee shall give notice to all Holders of Securities entitled
to repayment pursuant to terms of such Securities established in accordance with
Section 301, in the manner provided in Section 106 (the "Repayment Notice"),
                                                         ----------------   
that a Repayment Event has occurred and of the repayment right set forth herein
arising as a result thereof.  If applicable, the Company shall also deliver a
copy of the Repayment Notice to the Trustee.

     All notices of repayment shall identify the Securities eligible for
repayment and shall state:

     (1)  the Repayment Date,

                                       98
<PAGE>
 
     (2)  the date by which the repayment right must be exercised,

     (3)  the Repayment Price,

     (4)  the Conversion Price then in effect, the date on which the right to
convert the Securities to be repaid will terminate and the place or places where
such Securities, together (in the case of Bearer Securities) with all Coupons
appertaining thereto, if any, maturing after the Repayment Date, may be
surrendered for conversion,

     (5)  a description of the procedure which a Holder must follow to exercise
a repayment right and the place or places where such Securities, together (in
the case of Bearer Securities) with all Coupons appertaining thereto, if any,
maturing after the Repayment Date, are to be surrendered for payment and accrued
interest and Additional Amounts, if any, pertaining thereto, and

     (6)  that, unless otherwise specified in such notice, Bearer Securities of
any series, if any, surrendered for repayment must be accompanied by all Coupons
maturing subsequent to the Repayment Date or the amount of any such missing
Coupon or Coupons will be deducted from any amount due to such Holder, unless
security or indemnity satisfactory to the Company, the Trustee and any Paying
Agent is furnished.

     Section 1504.  Exercise Of Option.  Securities of any series subject to
                    ------------------                                      
repayment at the option of the Holders thereof will contain an "Option to Elect
Repayment" form substantially in the form of Exhibit F, on the reverse of such
                                             ---------                        
Securities.  In order for any Security to be repaid at the option of the Holder,
the Trustee must receive at the Place of Payment therefor specified in the terms
of such Security (or at such other place or places of which the Company shall
from time to time notify the Holders of such Securities) not earlier than 60
days nor later than 30 days prior to the Repayment Date (1) the Security so
providing for such repayment together with the "Option to Elect Repayment" form
on the reverse thereof duly completed by the Holder (or by the Holder's attorney
duly authorized in writing) or (2) a telegram, facsimile transmission or a
letter from a member of a national securities exchange or the National
Association of Securities Dealers, Inc. ("NASD"), or a commercial bank or trust
company in the United States setting forth the name of the Holder of the
Security, the principal amount of the Security, the principal amount of the
Security to be repaid, the CUSIP number, if any, or a description of the tenor
and terms of the Security, a statement that the option to elect repayment is
being exercised thereby and a guarantee that the Security to be repaid, together
with the duly completed form entitled "Option to Elect Repayment" on the reverse
of the Security, will be received by the Trustee not later than the fifth
Business Day after the date of such telegram, facsimile transmission or letter;
provided, however, that such telegram, facsimile transmission or letter shall
- --------  -------                                                            
only be effective if such Security and form duly completed are received by the
Trustee by such fifth Business Day.  If less than the entire principal amount of
such Security is to be repaid in accordance with the terms of such Security, the
principal amount of such Security to be repaid, in increments of the minimum
denomination for Securities of such series, and the denomination or
denominations of the Security or Securities to be issued to the Holder for the
portion of the principal amount of such Security surrendered that is not to be
repaid, must be specified. The principal amount of any Security providing for
repayment at the option of the Holder thereof may not be repaid in part if,

                                       99
<PAGE>
 
following such repayment, the unpaid principal amount of such Security would be
less than the minimum authorized denomination of Securities of the series of
which such Security to be repaid is a part.  Except as otherwise provided in or
pursuant to this Indenture, exercise of the repayment option by the Holder shall
be irrevocable unless waived by the Company and except that the right of the
Holder to convert the Securities with respect to which the repayment option is
being exercised shall continue until the close of business on the second
Business Day preceding the Repayment Date.

     Section 1505.  When Securities Presented For Repayment Become Due And
                    ------------------------------------------------------
Payable.  If Securities of any series providing for repayment at the option of
- -------                                                                       
the Holders thereof shall have been surrendered as provided in this Article
Fifteen and as provided by or pursuant to the terms of such Securities, such
Securities or the portions thereof, as the case may be, to be repaid shall
become due and payable and shall be paid by the Company on the Repayment Date
therein specified, and on and after such Repayment Date (unless the Company
shall default in the payment of such Securities on such Repayment Date) such
Securities shall, if the same were interest-bearing, cease to bear interest and
the Coupons for such interest appertaining to any Bearer Securities so to be
repaid, except to the extent provided below, shall be void. Upon surrender of
any such Security for repayment in accordance with such provisions, together
with all Coupons, if any, appertaining thereto maturing after the Repayment
Date, the principal amount of such Security so to be repaid shall be paid by the
Company, together with accrued interest and Additional Amounts, if any, to the
Repayment Date; provided, however, that Coupons whose Stated Maturity is on or
                --------  -------                                             
prior to the Repayment Date shall be payable only at an office or agency located
outside the United States (except as otherwise provided in Section 1002) and,
unless otherwise specified pursuant to Section 301, only upon presentation and
surrender of such Coupons; and provided, further, that, in the case of
Registered Securities, installments of interest and Additional Amounts, if any,
whose Stated Maturity is on or prior to the Repayment Date shall be payable (but
without interest thereon, unless the Company shall default in the payment
thereof) to the Holders of such Securities, or one or more Predecessor
Securities, registered as such at the close of business on the relevant Record
Dates according to their terms and the provisions of Section 307.

     If any Bearer Security surrendered for repayment shall not be accompanied
by all appurtenant Coupons maturing after the Repayment Date, such Security may
be paid after deducting from the amount payable therefor as provided in Section
1502 an amount equal to the face amount of all such missing Coupons, or the
surrender of such missing Coupon or Coupons may be waived by the Company and the
Trustee if there be furnished to them such security or indemnity as they may
require to save each of them and any Paying Agent harmless.  If thereafter the
Holder of such Security shall surrender to the Trustee or any Paying Agent any
such missing Coupon in respect of which a deduction shall have been made as
provided in the preceding sentence, such Holder shall be entitled to receive the
amount so deducted; provided, however, that interest represented by Coupons
                    --------  -------                                      
shall be payable only at an office or agency located outside the United States
(except as otherwise provided in Section 1002) and, unless otherwise specified
as contemplated by Section 301, only upon presentation and surrender of those
Coupons.

     If the principal amount of any Security surrendered for repayment shall not
be so repaid upon surrender thereof, such principal amount (together with
interest, if any, thereon accrued to

                                      100
<PAGE>
 
such Repayment Date) shall, until paid, bear interest from the Repayment Date at
the rate of interest or yield to maturity (in the case of Original Issue
Discount Securities ) set forth in such Security.

     Section 1506.  Securities Repaid In Part.  Upon surrender of any Security
                    -------------------------                                 
which is to be repaid in part only, the Company shall execute, the Guarantees of
the Guarantor shall be endorsed thereon  and the Trustee shall authenticate and
deliver to the Holder of such Security, without service charge and at the
expense of the Company, a new Security or Securities of the same series, of any
authorized denomination specified by the Holder, in an aggregate principal
amount equal to and in exchange for the portion of the principal of such
Security so surrendered which is not to be repaid.


                                ARTICLE SIXTEEN

                       MEETINGS OF HOLDERS OF SECURITIES

Section 1601.  Purposes for Which Meetings May Be Called.
               ----------------------------------------- 

     A meeting of Holders of Securities of any series may be called at any time
and from time to time pursuant to this Article Sixteen to make, give or take any
request, demand, authorization, direction, notice, consent, waiver or other Act
provided by this Indenture to be made, given or taken by Holders of Securities
of such series.

Section 1602.  Call, Notice and Place of Meetings.
               ---------------------------------- 

               (1)  The Trustee may at any time call a meeting of Holders of
     Securities of any series for any purpose specified in Section 1601, to be
     held at such time and at such place in the Borough of Manhattan, The City
     of New York, or, if Securities of such series have been issued in whole or
     in part as Bearer Securities, in London or in such place outside the United
     States as the Trustee shall determine.  Notice of every meeting of Holders
     of Securities of any series, setting forth the time and the place of such
     meeting and in general terms the action proposed to be taken at such
     meeting, shall be given, in the manner provided in Section 106, not less
     than 21 nor more than 180 days prior to the date fixed for the meeting.

 
               (2)  In case at any time the Company (by or pursuant to a Board
     Resolution) or the Holders of at least 10% in principal amount of the
     Outstanding Securities of any series shall have requested the Trustee to
     call a meeting of the Holders of Securities of such series for any purpose
     specified in Section 1601, by written request setting forth in reasonable
     detail the action proposed to be taken at the meeting, and the Trustee
     shall not have mailed notice of or made the first publication of the notice
     of such meeting within 21 days after receipt of such request (whichever
     shall be required pursuant to Section 106) or shall not thereafter proceed
     to cause the meeting to be held as provided herein, then the Company or the
     Holders of Securities of such series in the amount above specified, as the
     case may be, may determine the time and the place in the Borough of
     Manhattan, The City of New York, or, if Securities of such series are to be
     issued as

                                      101
<PAGE>
 
     Bearer Securities, in London for such meeting and may call such meeting for
     such purposes by giving notice thereof as provided in clause (1) of this
     Section.

Section 1603.  Persons Entitled to Vote at Meetings.
               ------------------------------------ 

     To be entitled to vote at any meeting of Holders of Securities of any
series, a Person shall be (1) a Holder of one or more Outstanding Securities of
such series, or (2) a Person appointed by an instrument in writing as proxy for
a Holder or Holders of one or more Outstanding Securities of such series by such
Holder or Holders.  The only Persons who shall be entitled to be present or to
speak at any meeting of Holders of Securities of any series shall be the Persons
entitled to vote at such meeting and their counsel, any representatives of the
Trustee and its counsel and any representatives of the Company and its counsel.


Section 1604.  Quorum; Action.
               -------------- 

     The Persons entitled to vote a majority in principal amount of the
Outstanding Securities of a series shall constitute a quorum for a meeting of
Holders of Securities of such series; provided, however, that if any action is
                                      --------  -------                       
to be taken at such meeting with respect to a consent or waiver which this
Indenture expressly provides may be given by the Holders of at least 66-2/3% in
principal amount of the Outstanding Securities of a series, the Persons entitled
to vote 66-2/3% in principal amount of the Outstanding Securities of such series
constitute a quorum.  In the absence of a quorum within 30 minutes after the
time appointed for any such meeting, the meeting shall, if convened at the
request of Holders of Securities of such series, be dissolved.  In any other
case the meeting may be adjourned for a period of not less than 10 days as
determined by the chairman of the meeting prior to the adjournment of such
meeting.  In the absence of a quorum at any such adjourned meeting, such
adjourned meeting may be further adjourned for a period of not less than 10 days
as determined by the chairman of the meeting prior to the adjournment of such
adjourned meeting.  Notice of the reconvening of any adjourned meeting shall be
given as provided in Section 1602(1), except that such notice need be given only
once not less than five days prior to the date on which the meeting is scheduled
to be reconvened.  Notice of the reconvening of an adjourned meeting shall state
expressly the percentage, as provided above, of the principal amount of the
Outstanding Securities of such series which shall constitute a quorum.

     Except as limited by the proviso to Section 902, any resolution presented
to a meeting or adjourned meeting duly reconvened at which a quorum is present
as aforesaid may be adopted only by the affirmative vote of the Holders of a
majority in principal amount of the Outstanding Securities of that series;
provided, however, that, except as limited by the proviso to Section 902, any
- --------  -------                                                            
resolution with respect to any consent or waiver which this Indenture expressly
provides may be given by the Holders of at least 66-2/3% in principal amount of
the Outstanding Securities of a series may be adopted at a meeting or an
adjourned meeting duly convened and at which a quorum is present as aforesaid
only by the affirmative vote of the Holders of 66-2/3% in principal amount of
the Outstanding Securities of that series; and provided, further, that, except
as limited by the proviso to Section 902, any resolution with respect to any
request, demand, authorization, direction, notice, consent, waiver or other Act
which this Indenture expressly provides may be made, given or taken by the
Holders of a specified percentage, which is less

                                      102
<PAGE>
 
than a majority, in principal amount of the Outstanding Securities of a series
may be adopted at a meeting or an adjourned meeting duly reconvened and at which
a quorum is present as aforesaid by the affirmative vote of the Holders of such
specified percentage in principal amount of the Outstanding Securities of such
series.

     Any resolution passed or decision taken at any meeting of Holders of
Securities of any series duly held in accordance with this Section shall be
binding on all the Holders of Securities of such series and the Coupons
appertaining thereto, whether or not such Holders were present or represented at
the meeting.

Section 1605.  Determination of Voting Rights; Conduct and Adjournment of
               ----------------------------------------------------------
Meetings.
- -------- 

               (1)  Notwithstanding any other provisions of this Indenture, the
     Trustee may make such reasonable regulations as it may deem advisable for
     any meeting of Holders of Securities of such series in regard to proof of
     the holding of Securities of such series and of the appointment of proxies
     and in regard to the appointment and duties of inspectors of votes, the
     submission and examination of proxies, certificates and other evidence of
     the right to vote, and such other matters concerning the conduct of the
     meeting as it shall deem appropriate.  Except as otherwise permitted or
     required by any such regulations, the holding of Securities shall be proved
     in the manner specified in Section 104 and the appointment of any proxy
     shall be proved in the manner specified in Section 104 or by having the
     signature of the person executing the proxy witnessed or guaranteed by any
     trust company, bank or banker authorized by Section 104 to certify to the
     holding of Bearer Securities.  Such regulations may provide that written
     instruments appointing proxies, regular on their face, may be presumed
     valid and genuine without the proof specified in Section 104 or other
     proof.

               (2)  The Trustee shall, by an instrument in writing, appoint a
     temporary chairman of the meeting, unless the meeting shall have been
     called by the Company, the Guarantor or by Holders of Securities as
     provided in Section 1602(2), in which case the Company, the Guarantor or
     the Holders of Securities of the series calling the meeting, as the case
     may be, shall in like manner appoint a temporary chairman.  A permanent
     chairman and a permanent secretary of the meeting shall be elected by vote
     of the Persons entitled to vote a majority in principal amount of the
     Outstanding Securities of such series represented at the meeting.

               (3)  At any meeting, each Holder of a Security of such series or
     proxy shall be entitled to one vote for each $1,000 principal amount of
     Securities of such series held or represented by him; provided, however,
                                                           --------  ------- 
     that no vote shall be cast or counted at any meeting in respect of any
     Security challenged as not Outstanding and ruled by the chairman of the
     meeting to be not Outstanding.  The chairman of the meeting shall have no
     right to vote, except as a Holder of a Security of such series or proxy.

               (4)  Any meeting of Holders of Securities of any series duly
     called pursuant to Section 1602 at which a quorum is present may be
     adjourned from time to time by Persons entitled to vote a majority in
     principal amount of the Outstanding Securities of

                                      103
<PAGE>
 
     such series represented at the meeting; and the meeting may be held as so
     adjourned without further notice.

Section 1606.  Counting Votes and Recording Action of Meetings.
               ----------------------------------------------- 

     The vote upon any resolution submitted to any meeting of Holders of
Securities of any series shall be by written ballots on which shall be
subscribed the signatures of the Holders of Securities of such series or of
their representatives by proxy and the principal amounts and serial numbers of
the Outstanding Securities of such series held or represented by them.  The
permanent chairman of the meeting shall appoint two inspectors of votes who
shall count all votes cast at the meeting for or against any resolution and who
shall make and file with the secretary of the meeting their verified written
reports in triplicate of all votes cast at the meeting.  A record, at least in
triplicate, of the proceedings of each meeting of Holders of Securities of any
series shall be prepared by the secretary of the meeting and there shall be
attached to said record the original reports of the inspectors of votes on any
vote by ballot taken thereat and affidavits by one or more persons having
knowledge of the facts setting forth a copy of the notice of the meeting and
showing that said notice was given as provided in Section 1602 and, if
applicable, Section 1604.  Each copy shall be signed and verified by the
affidavits of the permanent chairman and secretary of the meeting and one such
copy shall be delivered to the Company, another to the Guarantor, and another to
the Trustee to be preserved by the Trustee, the latter to have attached thereto
the ballots voted at the meeting.  Any record so signed and verified shall be
conclusive evidence of the matters therein stated.


                               ARTICLE SEVENTEEN

                          SUBORDINATION OF SECURITIES

Section 1701.  Securities Subordinate to Senior Indebtedness.
               --------------------------------------------- 

     The Company covenants and agrees, and each Holder of a Security, by his
acceptance thereof, likewise covenants and agrees, that, to the extent and in
the manner hereinafter set forth in this Article Seventeen, the indebtedness
represented by the Securities and the payment of the principal of, premium, if
any, and interest on each and all of the Securities are hereby expressly made
subordinate and subject in right of payment to the prior payment in full of all
Senior Indebtedness.

Section 1702.  Payment Over of Proceeds Upon Dissolution, Etc.
               ---------------------------------------------- 

     In the event of (a) any insolvency or bankruptcy case or proceeding, or any
receivership, liquidation, reorganization or other similar case or proceeding in
connection therewith, relative to the Company or its creditors, as such, or to
its assets, or (b) any liquidation, dissolution or other winding up of the
Company, whether voluntary or involuntary and whether or not involving
insolvency or bankruptcy, or (c) any assignment for the benefit of creditors or
any other marshaling of assets and liabilities of the Company, then and in any
such event the holders of Senior Indebtedness shall be entitled to receive
payment in full of all amounts due or to become due on or in respect of all
Senior Indebtedness, or provision shall be made for such payment in

                                      104
<PAGE>
 
money or money's worth, before the Holders of the Securities are entitled to
receive any payment on account of principal of, premium, if any, or interest on
the Securities and to that end the holders of Senior Indebtedness shall be
entitled to receive, for application to the payment thereof, any payment or
distribution of any kind or character, whether in cash, property or securities,
which may be payable or deliverable in respect of the Securities in any such
case, proceeding, dissolution, liquidation or other winding up or event.

     In the event that, notwithstanding the foregoing provisions of this Section
1702, the Trustee or the Holder of any Security shall have received any payment
or distribution of assets of the Company of any kind or character, whether in
cash, property or securities, before all Senior Indebtedness is paid in full or
payment thereof provided for, and if such fact shall, at or prior to the time of
such payment or distribution, have been made known to the Trustee or, as the
case may be, such Holder, then and in such event such payment or distribution
shall be paid over or delivered forthwith to the trustee in bankruptcy,
receiver, liquidating trustee, custodian, assignee, agent or other Person making
payment or distribution of assets of the Company for application to the payment
of all Senior Indebtedness remaining unpaid, to the extent necessary to pay all
Senior Indebtedness in full, after giving effect to any concurrent payment or
distribution to or for the holder of Senior Indebtedness.

     For purposes of this Article only, the words "cash, property or securities"
shall not be deemed to include shares of stock of the Company as reorganized or
readjusted, or securities of the Company or any other corporation provided for
by a plan of reorganization or readjustment which are subordinated in right of
payment to all Senior Indebtedness which may at the time be outstanding to
substantially the same extent as, or to a greater extent than, the Securities
are so subordinated as provided in this Article Seventeen.

     The issuance and delivery of junior securities upon conversion of
Securities in accordance with Article Twelve shall not be deemed to constitute a
payment or distribution on account of the principal of or premium or interest on
Securities or on account of the purchase or other acquisition of securities.
For the purposes of this Section, the term "junior securities" means Common
                                            -----------------              
Stock and any other cash, property or securities into which the Securities are
convertible pursuant to Article Twelve.  Nothing contained in this Article or
elsewhere in this Indenture or in the Securities is intended to or shall impair,
as among the Company, its creditors other than holders of Senior Indebtedness
and the Holders of the Securities, the right, which is absolute and
unconditional, of the Holder of any Security to convert such Security in
accordance with Article Twelve.

     The consolidation of the Company with, or the merger of the Company into,
another Person or the liquidation or dissolution of the Company following the
conveyance or transfer of all or substantially all of its properties and assets
to another Person upon the terms and conditions set forth in Article Eight shall
not be deemed a dissolution, winding up, liquidation, reorganization, assignment
for the benefit of creditors or marshaling of assets and liabilities of the
Company for the purposes of this Section if the Person formed by such
consolidation or into which the Company is merged or which acquires by
conveyance or transfer all or substantially all of such properties and assets,
as the case may be, shall, as a part of such consolidation, merger, conveyance
or transfer, comply with the conditions set forth in Article Eight.

                                      105
<PAGE>
 
Section 1703.  No Payment When Senior Indebtedness in Default
               ----------------------------------------------

     Upon the maturity of any Senior Indebtedness of the Company by lapse of
time, acceleration or otherwise, all principal thereof (and premium, if any) and
interest due thereon, including interest thereon accruing after the commencement
of any proceeding of the type referred to in Section 1702 above, and all other
amounts due on or with respect thereto, shall first be paid in full, or such
payment duly provided for in cash, before any payment, directly or indirectly,
is made by the Company on account of the principal of, premium, if any, or
interest and Additional Amounts on the Securities or Coupons.  Upon the
happening of an event of default with respect to any Senior Indebtedness of the
Company, as defined therein or in the instrument under which it is outstanding
permitting the holders to accelerate the maturity thereof, then, unless and
until such event of default shall have been cured or waived or shall have ceased
to exist, no payment shall be made by the Company, directly or indirectly, on
account of the principal of, premium, if any, or interest and Additional Amounts
on the Securities or Coupons; provided, however, that nothing in this Section
                              --------  -------                              
shall prevent the satisfaction of any sinking fund payment in accordance with
Article Thirteen by delivering and crediting pursuant to Section 1302 Securities
which have been acquired (upon redemption or otherwise) prior to such default in
payment or other default.

     In the event that, notwithstanding the foregoing, the Company shall make
any payment to the Trustee or the Holder of any Security prohibited by the
foregoing provisions of this Section, and if such fact shall, at or prior to the
time of such payment, have been made known to the Trustee or, as the case may
be, such Holder, then and in such event such payment shall be paid over and
delivered forthwith to the Company.

     The provisions of this Section 1703 shall not apply to any payment with
respect to which Section 1702 would be applicable.

Section 1704.  Payment Permitted If No Default.
               ------------------------------- 

     Nothing contained in this Article Seventeen or elsewhere in this Indenture
or in any of the Securities shall prevent (a) the Company, at any time except
during the pendency of any case, proceeding, dissolution, liquidation or other
winding up, assignment for the benefit of creditors or other marshaling of
assets and liabilities of the Company referred to in Section 1702 or under the
conditions described in Section 1703, from making payments at any time of
principal of, premium, if any, or interest on the Securities, or (b) the
application by the Trustee of any money deposited with it hereunder to the
payment of or on account of the principal of, premium, if any, or interest on
the Securities or the retention of such payment by the Holders if, at the time
of such application by the Trustee, it did not have knowledge that such payment
would have been prohibited by the provisions of this Article Seventeen.

Section 1705.  Subrogation to Rights of Holders of Senior Indebtedness.
               ------------------------------------------------------- 

     Subject to the payment in full of all Senior Indebtedness, the Holders of
the Securities shall be subrogated to the extent of the payments or
distributions made to the holders of such

                                      106
<PAGE>
 
Senior Indebtedness pursuant to the provisions of this Article Seventeen to the
rights of the holders of such Senior Indebtedness to receive payments and
distributions of cash, property and securities applicable to the Senior
Indebtedness until the principal of, premium, if any, and interest on the
Securities shall be paid in full. For purposes of such subrogation, no payments
or distributions to the holders of the Senior Indebtedness of any cash, property
or securities to which the Holders of the Securities or the Trustee would be
entitled except for the provisions of this Article Seventeen, and no payments
over pursuant to the provisions of this Article Seventeen to the holders of
Senior Indebtedness by Holders of the Securities or the Trustee, shall, as among
the Company, its creditors other than holders of Senior Indebtedness and the
Holders of the Securities, be deemed to be a payment or distribution by the
Company to or on account of the Senior Indebtedness.

Section 1706.  Provisions Solely to Define Relative Rights.
               ------------------------------------------- 

     The provisions of this Article Seventeen are and are intended solely for
the purpose of defining the relative rights of the Holders of the Securities on
the one hand and the holders of Senior Indebtedness on the other hand.  Nothing
contained in this Article Seventeen or elsewhere in this Indenture or in the
Securities is intended to or shall (a) impair, as among the Company, its
creditors other than holders of Senior Indebtedness and the Holders of the
Securities, the obligation of the Company, which is absolute and unconditional
(and which, subject to the rights under this Article Seventeen of the holders of
Senior Indebtedness, is intended to rank equally with all other general
unsecured obligations of the Company), to pay to the Holders of the Securities
the principal of, premium, if any, and interest on the Securities as and when
the same shall become due and payable in accordance with their terms; or (b)
affect the relative rights against the Company of the Holders of the Securities
and creditors of the Company other than the holders of Senior Indebtedness; or
(c) prevent the Trustee or the Holder of any Security from exercising all
remedies otherwise permitted by applicable law upon default under this
Indenture, subject to the rights, if any, under this Article Seventeen of the
holders of Senior Indebtedness to receive cash, property and securities
otherwise payable or deliverable to the Trustee or such Holder.

Section 1707.  Trustee to Effectuate Subordination.
               ----------------------------------- 

     Each holder of a Security by his acceptance thereof authorizes and directs
the Trustee on his behalf to take such action as may be necessary or appropriate
to effectuate the subordination provided in this Article Seventeen and appoints
the Trustee his attorney-in-fact for any and all such purposes.

Section 1708.  No Waiver of Subordination Provisions.
               ------------------------------------- 

     No right of any present or future holder of any Senior Indebtedness to
enforce subordination as herein provided shall at any time in any way be
prejudiced or impaired by any act or failure to act on the part of the Company
or by any act or failure to act, in good faith, by any such holder, or by any
non-compliance by the Company with the terms, provisions and covenants of this
Indenture, regardless of any knowledge thereof any such holder may have or be
otherwise charged with.

                                      107
<PAGE>
 
     Without in any way limiting the generality of the foregoing paragraph, the
holders of Senior Indebtedness may, at any time and from time to time, without
the consent of or notice to the Trustee or the Holders of the Securities,
without incurring responsibility to the Holders of the Securities and without
impairing or releasing the subordination provided in this Article Seventeen or
the obligations hereunder of the Holders of the Securities to the holders of
Senior Indebtedness, do any one or more of the following: (i) change the manner,
place or terms of payment or extend the time of payment of, or renew or alter,
Senior Indebtedness, or otherwise amend or supplement in any manner Senior
Indebtedness or any instrument evidencing the same or any agreement under which
Senior Indebtedness is outstanding; (ii) sell, exchange, release or otherwise
deal with any property pledged, mortgaged or otherwise securing Senior
Indebtedness; (iii) release any Person liable in any manner for the collection
of Senior Indebtedness; and (iv) exercise or refrain from exercising any rights
against the Company and any other Person.

Section 1709.  Notice to Trustee.
               ----------------- 

     The Company shall give prompt written notice to the Trustee of any fact
known to the Company which would prohibit the making of any payment to or by the
Trustee in respect of the Securities.  Notwithstanding the provisions of this
Article Seventeen or any other provision of this Indenture, the Trustee shall
not be charged with knowledge of the existence of any facts which would prohibit
the making of any payment to or by the Trustee in respect of the Securities,
unless and until the Trustee shall have received written notice thereof from the
Company, the Guarantor or a Senior Lender or from any trustee therefor; and,
prior to the receipt of any such written notice, the Trustee, subject to the
provisions of Section 601, shall be entitled in all respects to assume that no
such facts exist; provided, however, that if the Trustee shall not have received
                  --------  -------                                             
the notice provided for in this Section at least three Business Days prior to
the date upon which by the terms hereof any money may become payable for any
purpose (including, without limitation, the payment of the principal of,
premium, if any, or interest on any Security), then, anything herein contained
to the contrary notwithstanding, the Trustee shall have full power and authority
to receive such money and to apply the same to the purpose for which such money
was received and shall not be affected by any notice to the contrary which may
be received by it within three Business Days prior to such date.

     Subject to the provisions of Section 601, the Trustee shall be entitled to
conclusively rely on the delivery to it of a written notice by a Person
representing himself to be a Senior Lender (or a trustee therefor) to establish
that such notice has been given by a Senior Lender (or a trustee therefor).  In
the event that the Trustee determines in good faith that further evidence is
required with respect to the right of any Person as holders of Senior
Indebtedness to participate in any payment or distribution pursuant to this
Article Seventeen, the Trustee may request such Person to furnish evidence to
the reasonable satisfaction of the Trustee as to the amount of Senior
Indebtedness held by such Person, the extent to which such Person is entitled to
participate in such payment or distribution and any other facts pertinent to the
rights of such Person under this Article Seventeen, and if such evidence is not
furnished, the Trustee may defer any payment to such Person pending judicial
determination as to the right of such Person to receive such payment.

                                      108
<PAGE>
 
Section 1710.  Reliance on Judicial Order or Certificate of Liquidating Agent.
               -------------------------------------------------------------- 

     Upon any payment or distribution of assets of the Company referred to in
this Article Seventeen, the Trustee, subject to the provisions of Section 601,
and the Holders of the Securities shall be entitled to conclusively rely upon
any order or decree entered by any court of competent jurisdiction in which such
insolvency, bankruptcy, receivership, liquidation, reorganization, dissolution,
winding up or similar case or proceeding is pending, or a certificate of the
trustee in bankruptcy, receiver, liquidating trustee, custodian, assignee for
the benefit of creditors, agent or other Person making such payment or
distribution, delivered to the Trustee or to the Holders of Securities, for the
purpose of ascertaining the Persons entitled to participate in such payment or
distribution, the holders of the Senior Indebtedness and other indebtedness of
the Company, the amount thereof or payable thereon, the amount or amounts paid
or distributed thereon and all other facts pertinent thereto or to this Article
Seventeen.

Section 1711.  Trustee Not Fiduciary for Holders of Senior Indebtedness.
               -------------------------------------------------------- 

     The Trustee shall not be deemed to owe any fiduciary duty to the holders of
Senior Indebtedness and shall not be liable to any such holders if it shall in
good faith mistakenly pay over or distribute to Holders of Securities or to the
Company or to any other Person cash, property or securities to which any holders
of Senior Indebtedness shall be entitled by virtue of this Article Seventeen or
otherwise.

Section 1712.  Rights of Trustee as Holder of Senior Indebtedness; Preservation
               ----------------------------------------------------------------
of Trustee's Rights.
- ------------------- 

     The Trustee in its individual capacity shall be entitled to all the rights
set forth in this Article Seventeen with respect to any Senior Indebtedness
which may at any time be held by it, to the same extent as any other holder of
Senior Indebtedness, and nothing in this Indenture shall deprive the Trustee of
any of its rights as such holder.

     Nothing in this Article Seventeen shall apply to claims of, or payments to,
the Trustee under or pursuant to Section 606.

Section 1713.  Article Applicable to Paying Agents.
               ----------------------------------- 

     In case at any time any Paying Agent other than the Trustee shall have been
appointed by the Company and be then acting hereunder, the term "Trustee" as
                                                                 -------    
used in this Article shall in such case (unless the context otherwise requires)
be construed as extending to and including such Paying Agent within its meaning
as fully for all intents and purposes as if such Paying Agent were named in this
Article Seventeen in addition to or in place of the Trustee; provided, however,
                                                             --------  ------- 
that Section 1712 shall not apply to the Company or any Affiliate of the Company
if it or such Affiliate acts as Paying Agent.

                                      109
<PAGE>
 
                               ARTICLE EIGHTEEN


                          SUBORDINATION OF GUARANTEES

Section 1801.  Guarantees Subordinate to Senior Guarantor Indebtedness.
               ------------------------------------------------------- 

     The Guarantor covenants and agrees, and each Holder of a Security and the
related Guarantee, by his acceptance thereof, likewise covenants and agrees,
that, to the extent and in the manner hereinafter set forth in this Article
Eighteen, the Guarantees in respect of the Securities are hereby expressly made
subordinate and subject in right of payment to the prior payment in full of all
Senior Guarantor Indebtedness.

Section 1802.  Payment Over of Proceeds Upon Dissolution, Etc.
               ---------------------------------------------- 

     In the event of (a) any insolvency or bankruptcy case or proceeding, or any
receivership, liquidation, reorganization or other similar case or proceeding in
connection therewith, relative to the Guarantor or its creditors, as such, or to
its assets, or (b) any liquidation, dissolution or other winding up of the
Guarantor, whether voluntary or involuntary and whether or not involving
insolvency or bankruptcy, or (c) any assignment for the benefit or creditors or
any other marshaling of assets and liabilities of the Guarantor, then and in any
such event the holders of Senior Guarantor Indebtedness shall be entitled to
receive payment in full of all amounts due or to become due on or in respect of
all Senior Guarantor Indebtedness, or provision shall be made for such payment
in money or money's worth, before the Holders of the Guarantees are entitled to
receive any payment under the Guarantees on account of principal on, premium, if
any, or interest on the Securities and to that end the holders of Senior
Guarantor Indebtedness shall be entitled to receive, for application to the
payment thereof, any payment or distribution of any kind or character, whether
in cash, property or securities, which may be payable or deliverable in respect
of the Guarantees in any such case, proceeding, dissolution, liquidation or
other winding up or event.

     In the event that, notwithstanding the foregoing provisions of this
Section, the Trustee or the Holder of any Security in respect of the related
Guarantee shall have received any payment or distribution of assets of the
Guarantor of any kind or character, whether in cash, property or securities,
before all Senior Guarantor Indebtedness is paid in full or payment thereof
provided for, and if such fact shall, at or prior to the time of such payment or
distribution, have been made known to the Trustee or, as the case may be, such
Holder, then and in such event such payment or distribution shall be paid over
or delivered forthwith to the trustee in bankruptcy, receiver, liquidating
trustee, custodian, assignee, agent or other Person making payment or
distribution of assets of the Guarantor for application to the payment of all
Senior Guarantor Indebtedness remaining unpaid, to the extent necessary to pay
all Senior Guarantor Indebtedness in full, after giving effect to any concurrent
payment or distribution to or for the holder of Senior Guarantor Indebtedness.

     For purposes of this Article Eighteen only, the words "cash, property or
securities" shall not be deemed to include shares of stock of the Guarantor as
reorganized or readjusted, or securities of the Guarantor or any other
corporation provided for by a plan of reorganization or 

                                      110
<PAGE>
 
readjustment, which are subordinated in right of payment to all Senior Guarantor
Indebtedness which may at the time be outstanding to substantially the same
extent as, or to a greater extent than, the Guarantees are so subordinated as
provided in this Article Eighteen. The consolidation of the Guarantor with, or
the merger of the Guarantor into, another Person or the liquidation or
dissolution of the Guarantor following the conveyance or transfer of all or
substantially all of its properties and assets to another Person upon the terms
and conditions set forth in Article Eight shall not be deemed a dissolution,
winding up, liquidation, reorganization, assignment for the benefit of creditors
or marshaling of assets and liabilities of the Guarantor for the purposes of
this Section if the Person formed by such consolidation or into which the
Guarantor is merged or which acquires by conveyance or transfer all or
substantially all of such properties and assets , as the case may be, shall, as
a part of such consolidation, merger, conveyance or transfer, comply with the
conditions set forth in Article Eight.

     Section 1803.  No Payment When Senior Guarantor Indebtedness in Default.
                    -------------------------------------------------------- 

     Upon the maturity of any Senior Guarantor Indebtedness by lapse of time,
acceleration or otherwise, all principal thereof (and premium, if any) and
interest due thereon, including interest thereon accruing after the commencement
of any proceeding of the type referred to in Section 1802 above, and all other
amounts due on or with respect thereto, shall first be paid in full, or such
payment duly provided for in cash, before any payment, directly or indirectly,
is made by the Guarantor, directly or indirectly, in respect of the Guarantees
on account of the principal of, premium, if any, or interest and Additional
Amounts on the Securities or Coupons.  Upon the happening of an event of default
with respect to any Senior Guarantor Indebtedness, as defined therein or in the
instrument under which it is outstanding permitting the holders to accelerate
the maturity thereof, then, unless and until such event of default shall have
been cured or waived or shall have ceased to exist, no payment shall be made by
the Guarantor, directly or indirectly, in respect of the Guarantees on account
of the principal of, premium, if any, or interest and Additional Amounts on the
Securities or Coupons.

     In the event that, notwithstanding the foregoing, the Guarantor shall make
any payment to the Trustee or a Holder with respect to the Guarantee of any
Security prohibited by the foregoing provisions of this Section, and if such
fact shall, at or prior to the time of such payment, have been made known to the
Trustee or, as the case may be, the Holder of the Security to which such
Guarantee relates, then and in such event such payment shall be paid over and
delivered forthwith to the Guarantor.

     The provisions of this Section 1803 shall not apply to any payment with
respect to which Section 1802 would be applicable.

Section 1804.  Payment Permitted If No Default.
               ------------------------------- 

     Nothing contained in this Article Eighteen or elsewhere in this Indenture
or in any of the Securities or the Guarantees shall prevent (a) the Guarantor,
at any time except during the pendency of any case, proceeding, dissolution,
liquidation or other winding up, assignment for the benefit of creditors or
other marshaling of assets and liabilities of the Guarantor referred to in
Section 1802 or under the conditions described in Section 1803, from making
payments at any 

                                      111
<PAGE>
 
time on the Guarantees on account of principal of, premium, if any, or interest
on the Securities, or (b) the application by the Trustee of any money deposited
with it hereunder to the payment of or on the Guarantees on account of the
principal of, premium, if any, or interest on the Securities or the retention of
such payment by the Holders if, at the time of such application by the Trustee,
it did not have knowledge that such payment would have been prohibited by the
provisions of this Article Eighteen.

Section 1805.  Subrogation to Rights of Holders of Senior Guarantor 
               ---------------------------------------------------- 
Indebtedness. 
- ------------

     Subject to the payment in full of all Senior Guarantor Indebtedness, the
Holders of the Securities which are entitled to the benefits of the Guarantee
shall be subrogated to the extent of the payments or distributions made to the
holders of such Senior Guarantor Indebtedness pursuant to the provisions of this
Article Eighteen to the rights of the holders of such Senior Guarantor
Indebtedness to receive payments and distributions of cash, property and
securities applicable to the Senior Guarantor Indebtedness until the principal
of, premium, if any, and interest on the Securities shall be paid in full.  For
purposes of such subrogation, no payments or distributions to the holders of the
Senior Guarantor Indebtedness of any cash, property or securities to which the
Holders of any Security entitled to the benefits of a Guarantee or the Trustee
would be entitled except for the provisions of this Article Eighteen, and no
payments over pursuant to the provisions of this Article Eighteen to the holders
of Senior Guarantor Indebtedness by Holders of any Security entitled to the
benefits of a Guarantee or the Trustee, shall, as among the Guarantor, its
creditors other than holders of Senior Guarantor Indebtedness and the Holders of
any Security entitled to the benefits of a Guarantee, be deemed to be a payment
or distribution by the Guarantor to or on account of the Senior Guarantor
Indebtedness.

Section 1806.  Provisions Solely to Define Relative Rights.
               ------------------------------------------- 

     The provisions of this Article Eighteen are and are intended solely for the
purpose of defining the relative rights of the Holders of any Security entitled
to the benefits of a Guarantee on the one hand and the holders of Senior
Guarantor Indebtedness on the other hand.  Nothing contained in this Article
Eighteen or elsewhere in this Indenture or in the Guarantees or the Securities
is intended to or shall (a) impair, as among the Guarantor, its creditors other
than holders of Senior Guarantor Indebtedness and the Holders of any Security
entitled to the benefits of a Guarantee, the obligation of the Guarantor, which
is absolute and unconditional (and which, subject to the rights under this
Article Eighteen of the holders of Senior Guarantor Indebtedness, is intended to
rank equally with all other general obligations of the Guarantor), to pay to the
Holders of any Security entitled to the benefits of a Guarantee on account of
the principal of, premium, if any, and interest on the Securities as and when
the same shall become due and payable in accordance with their terms; or (b)
affect the relative rights against the Guarantor of the Holders of any Security
entitled to the benefits of a Guarantee and creditors of the Guarantor other
than the holders of Senior Guarantor Indebtedness; or (c) prevent the Trustee or
the Holder of any Security entitled to the benefits of a Guarantee from
exercising all remedies otherwise permitted by applicable law upon default under
this Indenture, subject to the rights, if any, under this Article Eighteen of
the holders of Senior Guarantor Indebtedness to receive cash, property and
securities otherwise payable or deliverable to the Trustee or such Holder.

                                      112
<PAGE>
 
Section 1807.  Trustee to Effectuate Subordination.
               ----------------------------------- 

     Each holder of a Guarantee by his acceptance thereof authorizes and directs
the Trustee on his behalf to take such action as may be necessary or appropriate
to effectuate the subordination provided in this Article Eighteen and appoints
the Trustee his attorney-in-fact for any and all such purposes.

Section 1808.  No Waiver of Subordination Provisions.
               ------------------------------------- 

     No right of any present or future holder of any Senior Guarantor
Indebtedness to enforce subordination as herein provided shall at any time in
any way be prejudiced or impaired by any act or failure to act on the part of
the Guarantor or by any act or failure to act, in good faith, by any such
holder, or by any non-compliance by the Guarantor with the terms, provisions and
covenants of this Indenture, regardless of any knowledge thereof any such holder
may have or be otherwise charged with.

     Without in any way limiting the generality of the foregoing paragraph, the
holders of Senior Guarantor Indebtedness may, at any time and from time to time,
without the consent of or notice to the Trustee or the Holders of any Security
entitled to the benefits of a Guarantee, without incurring responsibility to the
Holders of any Security entitled to the benefits of a Guarantee and without
impairing or releasing the subordination provided in this Article Eighteen or
the obligations hereunder of the Holders of any Security entitled to the
benefits of a Guarantee to the holders of Senior Guarantor Indebtedness, do any
one or more of the following: (i) change the manner, place or terms of payment
or extend the time of payment of, or renew or alter, Senior Guarantor
Indebtedness, or otherwise amend or supplement in any manner Senior Guarantor
Indebtedness or any instrument evidencing the same or any agreement under which
Senior Guarantor Indebtedness is outstanding; (ii) sell, exchange, release or
otherwise deal with any property pledged, mortgaged or otherwise securing Senior
Guarantor Indebtedness; (iii) release any Person liable in any manner for the
collection of Senior Guarantor Indebtedness; and (iv) exercise or refrain from
exercising any rights against the Guarantor and any other Person.

Section 1809.  Notice to Trustee.
               ----------------- 

     The Guarantor shall give prompt written notice to the Trustee of any fact
known to the Guarantor which would prohibit the making of any payment to or by
the Trustee in respect of the Guarantees.  Notwithstanding the provisions of
this Article Eighteen or any other provision of this Indenture, the Trustee
shall not be charged with knowledge of the existence of any facts which would
prohibit the making of any payment to or by the Trustee in respect of the
Guarantees, unless and until the Trustee shall have received written notice
thereof from the Guarantor, the Company or a holder of Senior Guarantor
Indebtedness or from any trustee therefor; and, prior to the receipt of any such
written notice, the Trustee, subject to the provisions of Section 601, shall be
entitled in all respects to assume that no such facts exist; provided, however,
                                                             --------  ------- 
that if the Trustee shall not have received the notice provided for in this
Section at least three Business Days prior to the date upon which by the terms
hereof any money may become payable for any purpose (including, without
limitation, the payment under the Guarantees on account of the principal of,
premium, if any, or interest on any Security), then, anything herein 

                                      113
<PAGE>
 
contained to the contrary notwithstanding, the Trustee shall have full power and
authority to receive such money and to apply the same to the purpose for which
such money was received and shall not be affected by any notice to the contrary
which may be received by it within three Business Days prior to such date.

     Subject to the provisions of Section 601, the Trustee shall be entitled to
conclusively rely on the delivery to it of a written notice by a Person
representing himself to be a holder of Senior Guarantor Indebtedness (or a
trustee therefor) to establish that such notice has been given by a holder of
Senior Guarantor Indebtedness (or a trustee therefor).  In the event that the
Trustee determines in good faith that further evidence is required with respect
to the right of any Person as a holder of Senior Guarantor Indebtedness to
participate in any payment or distribution pursuant to this Article Eighteen,
the Trustee may request such Person to furnish evidence to the reasonable
satisfaction of the Trustee as to the amount of Senior Guarantor Indebtedness
held by such Person, the extent to which such Person is entitled to participate
in such payment or distribution and any other facts pertinent to the rights of
such Person under this Article Eighteen, and if such evidence is not furnished,
the Trustee may defer any payment to such Person pending judicial determination
as to the right of such Person to receive such payment.

Section 1810.  Reliance on Judicial Order or Certificate of Liquidating Agent.
               -------------------------------------------------------------- 

     Upon any payment or distribution of assets of the Guarantor referred to in
this Article Eighteen, the Trustee, subject to the provisions of Section 601,
and the Holders of any Security entitled to the benefits of a Guarantee shall be
entitled to rely upon any order or decree entered by any court of competent
jurisdiction in which such insolvency, bankruptcy, receivership, liquidation,
reorganization, dissolution, winding up or similar case or proceeding is
pending, or a certificate of the trustee in bankruptcy, receiver, liquidating
trustee, custodian, assignee for the benefit of creditors, agent or other Person
making such payment or distribution, delivered to the Trustee or to the Holders
of any Security entitled to the benefits of a Guarantee, for the purpose of
ascertaining the Persons entitled to participate in such payment or
distribution, the holders of the Senior Guarantor Indebtedness and other
indebtedness of the Guarantor, the amount thereof or payable thereon, the amount
or amounts paid or distributed thereon and all other facts pertinent thereto or
to this Article Eighteen.

Section 1811.  Trustee Not Fiduciary for Holders of Senior Guarantor
               -----------------------------------------------------
Indebtedness.
- ------------

     The Trustee shall not be deemed to owe any fiduciary duty to the holders of
Senior Guarantor Indebtedness and shall not be liable to any such holders if it
shall in good faith mistakenly pay over or distribute to Holders of Guarantees
or to the Guarantor or to any other Person cash, property or securities to which
any holders of Senior Guarantor Indebtedness shall be entitled by virtue of this
Article Eighteen or otherwise.

Section 1812.  Rights of Trustee as Holder of Senior Guarantor Indebtedness;
               -------------------------------------------------------------
Preservation of Trustee's Rights.
- --------------- ---------------- 

     The Trustee in its individual capacity shall be entitled to all the rights
set forth in this Article Eighteen with respect to any Senior Guarantor
Indebtedness which may at any time be 

                                      114
<PAGE>
 
held by it, to the same extent as any other holder of Senior Guarantor
Indebtedness, and nothing in this Indenture shall deprive the Trustee of any of
its rights as such holder.

     Nothing in this Article Eighteen shall apply to claims of, or payments to,
the Trustee under or pursuant to Section 606.

Section 1813.  Article Applicable to Paying Agents.
               ----------------------------------- 

     In case at any time any Paying Agent other than the Trustee shall have been
appointed by the Company and be then acting hereunder, the term "Trustee" as
                                                                 -------    
used in this Article Eighteen shall in such case (unless the context otherwise
requires) be construed as extending to and including such Paying Agent within
its meaning as fully for all intents and purposes as if such Paying Agent were
named in this Article Eighteen in addition to or in place of the Trustee;
provided, however, that Section 1812 shall not apply to the Company or any
- --------  -------                                                         
Affiliate of the Company if it or such Affiliate acts as Paying Agent.

                                     * * *

     This instrument may be executed in any number of counterparts, each of
which so executed shall be deemed to be an original, but all such counterparts
shall together constitute but one and the same instrument.

                 [Remainder of page intentionally left blank]

                                      115
<PAGE>
 
     IN WITNESS WHEREOF, the parties hereto have caused this Indenture to be
duly executed, and their respective corporate seals to be hereunto affixed, all
as of the day and year first above written.


                                    THERMO INSTRUMENT SYSTEMS INC.


                                    By:/s/ Melissa F. Riordan 
                                       _____________________________
                                    Name:  Melissa F. Riordan
                                    Title: Treasurer

(SEAL)



Attest:


/s/ Sandra L. Lambert
______________________
  Secretary


                                    THERMO ELECTRON CORPORATION





(SEAL)                              By:/s/ Melissa F. Riordan
                                       _______________________________
                                    Name:  Melissa F. Riordan
                                    Title: Treasurer

Attest:


/s/ Sandra L. Lambert
______________________
  Secretary


                                    BANKERS TRUST COMPANY, as TRUSTEE



                                    By: /s/ Sandra Shaffer
                                       _____________________________
(SEAL)                              Name:  Sandra Shaffer
                                    Title: Assistant Vice President


Attest:


/s/ Jason Krasilovsky
_________________________

                                      116
<PAGE>
 
STATE OF MASSACHUSETTS    )
                          )  : SS.:
COUNTY OF MIDDLESEX       )

     On the 15th day of January, 1998, before me personally came Melissa F.
Riordan, to me known, who, being by me duly sworn, did depose and say that he is
the Treasurer of Thermo Instrument Systems Inc., a Delaware corporation, one of
the corporations described in and which executed the foregoing instrument; that
he knows the seal of said Corporation; that the seal affixed to said instrument
is such Corporation's seal; that it was so affixed by authority of the Board of
Directors of said Corporation; and that he signed his name thereto by like
authority.

 
                                    Tammy J. Viera  
                                    ____________________________________
                                    Notary Public
                                    Comm. Exp. Oct. 16, 2003  

[NOTARIAL SEAL]

                                      117
<PAGE>
 
STATE OF MASSACHUSETTS    )
                          )  : SS.:
COUNTY OF MIDDLESEX       )



     On the 15th day of January, 1998, before me personally came Melissa F.
Riordan, to me known, who, being by me duly sworn, did depose and say that he is
a Treasurer of Thermo Electron Corporation, a Delaware corporation, one of
the corporations described in and which executed the foregoing instrument; that
he knows the seal of said Corporation; that the seal affixed to said instrument
is such Corporation's seal; that it was so affixed by authority of the Board of
Directors of said Corporation; and that he signed his name thereto by like
authority.

 

 
                                    Tammy J. Viera
                                    ____________________________________
                                    Notary Public
                                    Comm. Exp. Oct. 16, 2003

[NOTARIAL SEAL]



STATE OF    )
            )  : SS.:
COUNTY OF   )



     On the 15th day of January, 1998, before me personally came
Sandra Shaffer, to me known, who, being by me duly sworn, did depose and say
that he is a Assist. VP of Bankers Trust Company, a New York banking
corporation, one of the persons described in and who executed the foregoing
instrument; that he knows the seal of said Corporation; that the seal affixed to
said instrument is such Corporation's seal; that it was so affixed by authority
of the Board of Directors of said Corporation; and that he signed his name
thereto by like authority.

                                    Margaret Bereza 
                                    ____________________________________
                                    Notary Public


[NOTARIAL SEAL]

                                      118
<PAGE>
 
                                                                       EXHIBIT A
                                                                       ---------
                                                                                
                                   GUARANTEE

     For value received, Thermo Electron Corporation, a corporation organized
under the laws of the State of Delaware (herein called the "Guarantor," which
                                                            ---------        
term includes any successor corporation under the indenture referred to in the
Security upon which this Guarantee is endorsed), hereby unconditionally
guarantees to the Holder of the Security upon which this Guarantee is endorsed
and to the Trustee on behalf of the Trustee and such Holder the due and punctual
payment of the principal of, premium, if any, and interest and Additional
Amounts, if any, on such Security, any other amount due and payable pursuant to
the terms of the Indenture and the due and punctual payment of the sinking fund
or analogous payments referred to therein if any, when and as the same shall
become due and payable, whether at the stated Maturity, by declaration of
acceleration, call for redemption, repayment at the option of the Holder or
otherwise, according to the terms hereof and of the Indenture.  In case of the
failure of Thermo Instrument Systems Inc., a corporation organized under the
laws of Delaware (herein called the "Company," which term includes any successor
                                     -------                                    
corporation under such Indenture), punctually to make any such payment of
principal, premium, if any, or interest or Additional Amounts, if any, the
Guarantor hereby agrees to cause any such payment to be made punctually when and
as the same shall become due and payable, whether at the Stated Maturity or by
declaration of acceleration, call for redemption, repayment at the option of the
Holder or otherwise, and as if such payment were made by the Company.

     The Guarantor hereby agrees that its obligations hereunder shall be as if
it were principal debtor and not merely surety, and shall be absolute and
unconditional (except as to the specific subordination provisions contained in
Article Eighteen of the Indenture), irrespective of, and shall be unaffected by,
any invalidity, subordination, irregularity or unenforceability of such Security
or such Indenture, any failure to enforce the provisions of such Security or
such Indenture, or any waiver, modification or indulgence granted to the Company
with respect thereto, by the Holder of such Security or the Trustee or any other
circumstance which may otherwise constitute a legal or equitable discharge of a
surety or guarantor.  The Guarantor hereby waives the benefits of diligence,
presentment, demand of payment, filing of claims with a court in the event of
merger, insolvency or bankruptcy of the Company, any right to require a
proceeding first against the Company, protest or notice with respect to such
Security or the indebtedness evidenced thereby and all demands whatsoever, and
covenants that this Guarantee will not be discharged except by strict and
complete performance of the obligations contained in such Security and this
Guarantee.  The Guarantor hereby agrees that, in the event of a default in
payment of principal of, premium, if any, and interest, and Additional Amounts,
if any, on such Security, or default in any sinking fund or analogous payment
referred to therein, legal proceedings may be instituted by the Trustee on
behalf of, or by, the Holder of such Security, on the terms and conditions set
forth in the indenture, directly against the Guarantor to enforce this Guarantee
without first proceeding against the Company.

     The Guarantor shall be subrogated to all rights of the Holder of such
Security and the Trustee against the Company in respect of any amounts paid to
such Holder by the Guarantor on account of such Security pursuant to the
provisions of this Guarantee or the Indenture; provided, 
                                               --------

                                      A-1
<PAGE>
 
however, that the Guarantor shall not be entitled to enforce, or to receive any
- ------- 
payments arising out of or based upon, such right of subrogation until the
principal of, premium, if any, and interest and Additional Amounts, if any, on
all Securities issued under such Indenture shall have been paid in full.

     Claims under this Guarantee are, to the extent provided in the Indenture,
subject in right of payment to the prior payment in full of all Senior Guarantor
Indebtedness, and this Guarantee is issued subject to the provisions of the
Indenture with respect thereto.  Each Holder of a Security upon which this
Guarantee is endorsed, by accepting the same, (a) agrees to and shall be bound
by such provisions, (b) authorizes and directs the Trustee on his behalf to take
such action as may be necessary or appropriate to effectuate the subordination
so provided and (c) appoints the Trustee his, her or its attorney-in-fact for
any and all such purposes.

     No reference herein to such Indenture and no provision of this Guarantee or
of such Indenture shall alter or impair the guarantee of the Guarantor, which is
absolute and unconditional (except as to the specific subordination provisions
contained in Article Eighteen of the Indenture), of the due and punctual payment
of principal, premium (if any), and interest and Additional Amounts, if any, on
the Security upon which this Guarantee is endorsed.

     This Guarantee shall not be valid or obligatory for any purpose until the
certificate of authentication of the Security upon which this Guarantee is
endorsed shall have been manually executed by or on behalf of the Trustee under
such Indenture.

     All terms used in this Guarantee which are defined in such Indenture shall
have the meanings assigned to them in such Indenture.

     This Guarantee shall be deemed to be a contract made under the laws of the
Commonwealth of Massachusetts, and for all purposes shall be governed by and
construed in accordance with the laws of the Commonwealth of Massachusetts.

     IN WITNESS WHEREOF, the Guarantor has caused this Guarantee to be duly
executed under its corporate seal and dated the date on the face hereof.

                                    THERMO ELECTRON CORPORATION


Attest:______________________________    By: ________________________________

                                         Title: _____________________________

                                      A-2
<PAGE>
 
                                                                       EXHIBIT B
                                                                       ---------
                                                                                
     This is one of the Securities of the series designated therein referred to
in the within-mentioned Indenture.

                                    NAME OF TRUSTEE,
                                    as Trustee
*Dated:
                                    By:_________________________________
                                       Authorized Officer



____________________________________
*  For Registered Securities Only

                                      B-1
<PAGE>
 
                                                                       EXHIBIT C
                                                                       ---------
                                                                                
                               CONVERSION NOTICE

     (a) For Bearer Securities:

     The undersigned Holder of this Security hereby irrevocably exercises the
option to convert this Security, or any portion of the principal amount hereof
(which is an integral multiple of U.S. $1,000 below designated) into shares of
Common Stock in accordance with the terms of the Indenture referred to in this
Security and directs that such shares, together with a check in payment for any
fractional share and any securities representing any unconverted principal
amount hereof, be delivered to the undersigned unless a different name has been
indicated below.  The address for payment of any such check must be outside the
United States.  If shares are to be registered in the name of a Person other
than the undersigned, the undersigned will pay all transfer taxes payable with
respect thereto.

<TABLE>
<CAPTION>
Dated: __________________                       ________________________________
                                                Signature
<S>                                             <C>
If shares are to be registered in the name of   Holder
and delivered to a Person other than the
Holder, please print such Person's name and     Please print name and address of holder
address:
 
 _____________________________________           ____________________________________
             Name                                           Name
 
_____________________________________           ____________________________________
             Address                                        Address
 
_____________________________________           ____________________________________
 
 
_____________________________________           ____________________________________
 
 
_____________________________________           ____________________________________
Social Security or other Taxpayer               Social Security or other Taxpayer
Identification Number, if any                   Identification Number, if any
</TABLE>

                                      C-1
<PAGE>
 
<TABLE>
<CAPTION>
<S>                                             <C> 
Name and Address (outside the United States)    If only a portion of the Securities is to be
to where any check referred to in the first     converted, please indicate:
paragraph of this Conversion Notice should
be mailed:                                      1.  Principal Amount to be converted:
 
                                                U.S. $___________________
 
 
_______________________________                 2.  Principal amount and denomination of
         Name                                   Bearer Securities representing unconverted
                                                principal amount to be issued:
 
_______________________________
         Address
                                                Amount:  U.S.$_________________

                                                Denominations:
                                                U.S.$__________
                                                (any integral multiple of U.S. $1,000)
</TABLE>

                                      C-2
<PAGE>
 
     (b) For Registered Securities:

     The undersigned Holder of this Security hereby irrevocably exercises the
option to convert this Security, or any portion of the principal amount hereof
(which is an integral multiple of U.S. $1,000 below designated) into shares of
Common Stock in accordance with the terms of the Indenture referred to in this
Security, and directs that such shares, together with a check in payment for any
fractional share and any Securities representing any unconverted principal
amount hereof, be delivered to and be registered in the name of the undersigned
unless a different name has been indicated below.  If shares or Securities are
to be registered in the name of a Person other than the undersigned, the
undersigned will pay all transfer taxes payable with respect thereto.

Dated:______________________        ___________________________
                                         Signature
                                    [MUST BE GUARANTEED IF STOCK OR SECURITIES
                                    ARE TO BE ISSUED IN A NAME OTHER THAN THE
                                    REGISTERED HOLDER OF THE SECURITY]

____________________________________
              Name
 
____________________________________
             Address

____________________________________
Social Security or other Taxpayer
Identification Number, if any

                                      C-3
<PAGE>

<TABLE> 
<S>                                                             <C> 
If shares or Registered Securities are to be                    If only a portion of the Securities is to be converted, please 
registered in the name of a person other than                   indicate:   
the Holder, please print such Person's name and address:        1.  Principal amount to be converted:                          
                                                                                                                               
                                                                U.S. $___________________                                      
_______________________________________                                                                                        
             Name                                                                                                              
                                                                2.  Principal amount and denomination of Registered Securities 
                                                                representing unconverted principal amount to be issued.    
_______________________________________                                                                                        
            Address                                             Amount:  U.S.$_________________                                
                                                                                                                               
_______________________________________                         Denominations:                                                 
Social security or other Taxpayer Identification                U.S.$__________                                                
Number, if any                                                  (any integral multiple of U.S. $1,000)                         
</TABLE> 
                                       
                                      C-4
<PAGE>
 
                                                                       EXHIBIT D
                                                                       ---------

                Form of Certificate of Beneficial Ownership for
                    Bearer Securities to be Provided to the
              Euroclear Operator or to Cedel Bank, societe anonyme

                                 CERTIFICATION
                                 -------------
                                        
                               U.S. $____________

                         THERMO INSTRUMENT SYSTEMS INC.

                             [Title of Securities]

                               (the "Securities")

     This is to certify that as of the date hereof and except as set forth
below, $___________ aggregate principal amount of the above-mentioned Securities
held by you for our account are owned or, if this certificate is being delivered
in connection with a payment of interest, were owned, by or on behalf of, (a) a
person (other than a financial institution for purposes of resale during the
restricted period) who is not a United States person; or (b) a United States
person (other than a financial institution for purposes of resale during the
restricted period) who is (i) a foreign branch of a United States financial
institution or (ii) a United States person acquiring such Securities through the
foreign branch of a United States financial institution and who for purposes of
this certification holds such Securities through such financial institution on
the date hereof, and, in the case of either (i) or (ii), such United States
financial institution has agreed, for the benefit of the Company, to comply with
the requirements of Section 165(j)(3)(A), (B) or (C) of the United States
Internal Revenue Code of 1986, as from time to time amended, and the regulations
thereunder; or (c) a financial institution for purposes of resale during the
restricted period and such financial institution has not acquired such
Securities for purposes of resale directly or indirectly to a United States
person or to a person within the United States or its possessions; and the
undersigned has obtained a similar certificate from its member organizations on
which this certificate is based; provided, however, that if the undersigned has
actual knowledge that the information contained in such a certificate is false
(and, absent documentary evidence that the beneficial owner of such Security is
not a United States person, it will be deemed to have actual knowledge that such
certificate is false if it has a United States address for such beneficial
owner, other than a financial institution described above), the undersigned will
not deliver a Security in temporary or definitive bearer form to the person who
signed such certificate notwithstanding the delivery of such certificate to the
undersigned.

                                      D-1
<PAGE>
 
<TABLE>
<CAPTION>
                                No. of Certificates                           Amount
<S>                             <C>                          <C>       <C>
$1,000 Denomination             ________________             =         $________________
$10,000 Denomination            ________________             =         $________________
[Other Authorized               ________________             =         $________________
 Denomination]
Total Requested                 ________________             =         $________________/*/
</TABLE>

     As used herein, (i) "United States person" means a citizen or resident of
the United States, a corporation, partnership or other entity created or
organized in or under the laws of the United States, an estate the income of
which is subject to United States Federal income taxation regardless of its
source, any trust if a court within the United States is able to exercise
primary supervision of the administration thereof and one or more United States
fiduciaries have the authority to control all substantial decisions thereof, and
any other person deemed a "United States person" or a "U.S. person" under the
Internal Revenue Code of 1986, as amended, (ii) "United States" means the United
States of America (including the States and the District of Columbia) and its
territories and possessions, including Puerto Rico, the U.S. Virgin Islands,
Guam, American Samoa, Wake Island and the Northern Mariana Islands, (iii)
"restricted period" means the period described in Section 1.163-5(c)(2)(i)(D)(7)
of the United States Treasury Regulations, and (iv) "financial institution"
means the persons described in Section 1. 165-12(c)(1)(v) of the United States
Treasury Regulations.

     We undertake to advise you promptly by tested telex on or prior to the date
on which you intend to submit your certification relating to the Securities held
by you for our account in accordance with your operating procedures if any
applicable statement herein is not correct on such date, and in the absence of
any such notification it may be assumed that this certification applies as of
such date.

     This certification excepts and does not relate to U.S.$_______________ of
such interest in the above Securities in respect of which we are not able to
certify and as to which we understand exchange and delivery of Definitive
Securities cannot be made until we do so certify.


__________________________
/*/ Must equal the amount stated in the first paragraph of this certificate.

                                      D-2
<PAGE>
 
     We understand that this certification is required in connection with
certain tax laws and, if applicable, certain securities laws of the United
States.  In connection therewith, if administrative or legal proceedings are
commenced or threatened in connection with which this certification is or would
be relevant, we irrevocably authorize you to produce this certification or a
copy hereof to any interested party in such proceedings.

Dated:    ___________________, ____/*//*/


                                           [Name]


                                           By:_________________________
                                                Signature
                                                As, or as agent for, the
                                                beneficial owner[s] of the
                                                Securities to which this
                                                certificate relates.


______________________________
/*//*/ Not earlier than 15 days prior to the earlier of the date that definitive
Bearer Security is delivered and the Exchange Date.

                                      D-3
<PAGE>
 
                                                                       EXHIBIT E
                                                                       ---------

                       Form of Certificate to be Given by
             the Euroclear Operator and Cedel Bank, societe anonyme


                                 CERTIFICATION
                                 -------------

                                     U.S. $

                         THERMO INSTRUMENT SYSTEMS INC.

                             [Title of Securities]

                              (the "Securities")

     This is to certify that, based solely on certifications we have received in
writing, by tested telex or electronic transmission from member organizations
appearing in our records as persons being entitled to a portion of the principal
amount set forth below or to interest payable on an interest payment date (our
"Member Organizations"), substantially to the effect set forth in the Indenture
relating to the above-captioned Securities, as of the date hereof, U.S.
$_______________ aggregate principal amount of the above-captioned Securities is
owned by persons that are not citizens or residents of the United States, United
States domestic partnerships, United States domestic corporations, any estate
the income of which is subject to United States Federal income taxation
regardless of its source, any trust if a court within the United States is able
to exercise primary supervision of the administration thereof and one or more
United States fiduciaries have the authority to control all substantial
decisions thereof, or any other person deemed a "United States person" or a
"U.S. person" under the Internal Revenue Code of 1986, as amended and the
regulations thereunder ("United States persons").

     The following denominations of Bearer Securities are requested:

<TABLE>
<CAPTION>
                                No. of Certificates                           Amount
<S>                             <C>                          <C>       <C>
$1,000 Denomination             ________________             =         $________________
$10,000 Denomination            ________________             =         $________________
[Other    Authorized            ________________             =         $________________
Denomination]
Total Requested                 ________________             =         $________________/*/
</TABLE>



     We further certify (i) that we are not making available herewith for
exchange any portion of the temporary global Security excepted in such
certifications and (ii) that as of the date hereof we have not received any
notification from any of our Member Organizations to the effect that the
statements made by such Member Organization with respect to any portion of the
part submitted herewith for exchange are no longer true and cannot be relied
upon as of the date


__________________________
/*/ Must equal the amount stated in the first paragraph of this certificate.

                                      E-1
<PAGE>
 
hereof. We further certify that interest payable on the interest payment dates
on _________ and _________ will be paid with respect to U.S. $_____________
principal amount of the Securities with respect to which we have received from
Member Organizations certificates substantially in the form set out in Exhibit D
to the Indenture relating to the Securities that the Securities (a) are owned by
a person (other than a financial institution for purposes of resale during the
restricted period) who is not a United States person; (b) are owned by a United
States person (other than a financial institution for purposes of resale during
the restricted period) who is (i) a foreign branch of a United States financial
institution or (ii) a United States person who acquired such Securities through
the foreign branch of a United States financial institution and who for purposes
of this certification holds such Securities through such financial institution
on the date hereof and, in either case, such United States financial institution
has agreed, for the benefit of the Company, to comply with the requirements of
Section 165(j)(3)(A), (B) or (C) of the United States Internal Revenue Code of
1986, as from time to time amended, and the regulations thereunder; or (c) are
owned by a financial institution for purposes of resale during the restricted
period and such financial institution has certified that it has not acquired
such Securities for purposes of resale directly or indirectly to a United States
person or to a person within the United States or its possessions.

     To the extent that we have knowledge that any of such certificates from a
Member Organization is false and to the extent that we have not received with
respect to any Securities such certificates from Member Organization, we are not
requesting that payment be made for interest with respect thereto.

     We further certify that as of the date hereof we have not received any
notification from any of our Member Organizations to the effect that the
statements made by such Member Organization with respect to any interest payment
on any portion of the principal amount of the Securities are no longer true and
cannot be relied upon as of the date hereof.  We further certify that under the
rules of the undersigned organization, each Member Organization has agreed that
any electronic certification shall have the effect of a signed certification and
that all certifications shall be retained for at least four calendar years
following the year in which the certifications are received in compliance with
the rules set forth under Treas.  Reg. 1.163-5(c)(2)(i)(D)(3)(i).

     We undertake that any interest received by us and not paid as provided
above shall be returned to the Trustee for the above-captioned Securities
immediately prior to the expiration of two years after such interest payment
date in order to be repaid by such Trustee to the above issuer at the end of two
years after such interest payment date.

     We understand that this certification is required in connection with
certain tax laws and, if applicable, certain securities laws of the United
States.  In connection therewith, if administrative or legal proceedings are
commenced or threatened in connection with which this certification is or would
be relevant, we irrevocably authorize you to produce this certification to any
interested party in such proceedings.

                                      E-2
<PAGE>
 
     As used herein, "United States" means the United States of America
(including the states thereof and the District of Columbia), its territories and
possessions and other areas subject to its jurisdiction,.  As used herein,
"restricted period" means the period described in Section 1.163-5(c)(2)(i)(D)(7)
of the United States Treasury Regulations and "financial institution" means the
persons described in Section 1.165-12(c)(1)(v) of the United States Treasury
Regulations.


Dated:    ____________________, ____/*//*/



                                          Yours faithfully,

                                          [MORGAN GUARANTY TRUST COMPANY OF NEW
                                          YORK, BRUSSELS OFFICE, AS OPERATOR OF
                                          THE EUROCLEAR SYSTEM]

                                          CEDEL BANK, SOCIETE ANONYME/*//*//*/

                                          By:_____________________________



______________________________
/*//*/      To be dated no earlier than the earlier of the date the definitive
Bearer Security is delivered and the Exchange Date.
/*//*//*/   Delete as appropriate.

                                      E-3
<PAGE>
 
                                                                       EXHIBIT F
                                                                       ---------

                           OPTION TO ELECT REPAYMENT
                             UPON A REPAYMENT EVENT

To:     Thermo Instrument Systems Inc.

     The undersigned owner of this Security hereby acknowledges receipt of a
notice from Thermo Instrument Systems Inc. (the "Company") as to the occurrence
of a Repayment Event with respect to the Common Stock of the Company and
requests and instructs the Company to repay the entire principal amount of this
Security, or the portion thereof (which is $1,000 or an integral multiple
thereof) below designated, in accordance with the terms of the Indenture
referred to in this Security at the Repayment Price (or the relevant percentage
thereof), together with accrued interest to such date (except if the Repayment
Date shall be an Interest Payment Date), to the holder hereof.


Dated: ________________________

                                  ________________________________
                                  Signature*(s)

                                  Name: __________________________
                                  Address:_________________________
                                          _________________________
                                  [* Signature Guarantee Required]

                                  Principal amount to be repaid
                                  (if less than all):
                                  $__________
                                  NOTICE:  If this Security is issued
                                  in registered form, the above
                                  signatures of the holder(s) hereof
                                  must correspond with the name as it appears
                                  in the Security in every particular without
                                  alteration or enlargement or any
                                  change whatever.

__________________

                                  Social Security or Other
                                  Taxpayer Identification Number

                                      F-1

<PAGE>
 
                                                                     EXHIBIT 4.2

       Joint Officers' Certificate of Thermo Instrument Systems Inc. and
              Thermo Electron Corporation Pursuant to Section 301
                       of the Indenture Identified Below



     The undersigned, Melissa F. Riordan and Sandra Lambert, as the Treasurer
and Corporate Secretary, respectively, of Thermo Instrument Systems Inc. (the
"Company"), acting pursuant to authorizations contained in resolutions, copies
of which are delivered herewith, duly adopted on July 17, 1997 and January 13,
1998 by the Board of Directors of the Company and on January 15, 1998 by the
Pricing Committee thereof, and the undersigned, Melissa F. Riordan and Sandra
Lambert, as the Treasurer and the Corporate Secretary, respectively, of Thermo
Electron Corporation ("Thermo Electron" or the "Guarantor"), acting pursuant to
authorizations contained in resolutions, copies of which are delivered herewith,
duly adopted on July 17, 1997 and January 13, 1998 by the Board of Directors of
the Guarantor, do hereby authorize, adopt and approve the following terms for a
series (the "Series") of the Company's debt securities (the "Securities") to be
issued under a Subordinated Indenture dated as of January 15, 1998 (the
"Indenture"), from the Company, as issuer, and Thermo Electron, as guarantor, to
Bankers Trust Company, as Trustee, pursuant to the Registration Statement on
Form S-3 (Nos. 333-32031 and 333-32031-01) under the Securities Act of 1933, as
amended.  Terms used herein without definition shall have the meanings ascribed
to such terms in the Indenture.  Article and Section references are to the
Indenture.

<TABLE>


- --------------------------------------------------------------------------------------------------------
<S>        <C>                                         <C>
Section    The title or designation of the                 4% Convertible Subordinated Debentures due
301 (1)    Securities and the series in which the        2005 (the "Debentures").
           Securities shall be included:
- --------------------------------------------------------------------------------------------------------
</TABLE> 
<PAGE>
 
                                      -2-

<TABLE>


- --------------------------------------------------------------------------------------------------------
<S>        <C>                                         <C>
Section    Any limit upon the aggregate principal      $250,000,000 aggregate principal amount
301 (2)    amount of the Securities of such title or   
           designation or the Securities of such       
           series which may be authenticated and
           delivered under the Indenture (except for
           Securities authenticated and delivered
           upon registration or transfer of, or in
           exchange for, or in lieu of, other
           Securities of such series pursuant to
           Section 304, 305, 306, 905 or 1107 of the
           Indenture, upon repayment in part of any
           Security of such series pursuant to
           Article Fifteen, or upon surrender in
           part of any Security for conversion or
           exchange into other securities pursuant
           to its terms, or pursuant to the terms of
           such Securities):
- --------------------------------------------------------------------------------------------------------
Section    If the Securities are to be issuable as     The Debentures are to be issued as both
301 (3)    Registered Securities, as Bearer            Registered Debentures and as Bearer Debentures.
           Securities or alternatively as Bearer                                                              
           Securities and Registered Securities, and   Bearer Debentures are to be issued with Coupons        
           whether the Bearer Securities are to be     attached (except for the temporary global Bearer       
           issuable with Coupons, without Coupons or   Debenture).  (Section 201)                             
           both, and any restrictions applicable to                                                            
           the offer, sale or delivery of the Bearer   Restrictions on the offer, sale and delivery of         
           Securities and the terms, if any, upon      Bearer Debentures are as set forth in the               
           which Bearer Securities may be exchanged    Indenture.  (Section 304)                               
           for Registered Securities and vice versa:                                                            
                                                       Bearer Debentures may be exchanged for                   
                                                       Registered Debentures as set forth in the                
                                                       Indenture. (Section 305)                                 
                                                                                                                 
                                                       Registered Debentures may not be exchanged for            
                                                       Bearer Debentures. (Section 305)                          
- --------------------------------------------------------------------------------------------------------
</TABLE> 
<PAGE>
 
                                      -3-

<TABLE>


- --------------------------------------------------------------------------------------------------------
<S>        <C>                                         <C>
Section    If any of the Securities are to be          Registered Debentures are to be issued solely in
301 (4)    issuable in global form, when any of such   permanent global form (except as otherwise
           Securities are to be issuable in global     specified in Section 305).  The Depository for
           form and (i) whether such Securities are    the Registered Debentures is the Depository
           to be issued in temporary or permanent      Trust Company. Registered Debentures shall be
           global form or both, (ii) the extent to     registered in the name of the Depository or its
           which, or the manner in which, any          nominee (except as otherwise specified in
           interest payment or Additional Amounts on   Section 305). Beneficial owners of interests in
           a global Security on an Interest Payment    the permanent global Registered Debenture may
           Date will be paid and the manner in which   not exchange such interest for Debentures,
           any principal of or premium, if any, on     except as specified in Section 305. The original
           any global Security will be paid, (iii)     issuance date for the Debentures is January 21,
           whether beneficial owners of interests in   1998.
           any such global Security may exchange       
           such interests for Securities of the same   Bearer Debentures shall be initially issued  in    
           series and of like tenor and of any         temporary global form, to be delivered to and      
           authorized form and denomination, and the   held by Bankers Trust Company, London office, as   
           circumstances under which any such          the Common Depository.  On and after the           
           exchanges may occur, if other than in the   Exchange Date, which is the date 40 days after     
           manner specified in Section 305 of the      the first closing date relating to the sale    
           Indenture, (iv) the name of the             of the Debentures, the temporary global Bearer 
           Depository or the U.S. Depository, as the   Debenture shall be exchangeable for Definitive     
           case may be, with respect to any global     Debentures as provided in the Indenture. Other          
           Security, (v) the name of the Common        exchanges shall be as set forth in the Indenture.    
           Depository, if applicable, and (vi) the           
           Exchange Date, if applicable:                     
                                                            
                                                       Payments of interest and Additional Amounts, if     
                                                       any, on an Interest Payment Date and payments of    
                                                       principal and premium, if any, shall be made to     
                                                       the registered holder of a global Debenture as      
                                                       provided in the Indenture.  In the case of a        
                                                       temporary global Bearer Debenture, no interest      
                                                       payments or other payments thereon will be made     
                                                       until such temporary global Bearer Debenture is     
                                                       exchanged for definitive Debentures as provided     
                                                       in the Indenture.                                    
                                                       
- --------------------------------------------------------------------------------------------------------
Section    If any of the Securities are to be          Bearer Debentures and Registered Debentures in
301 (5)    issuable as Bearer Securities or in         global form shall be dated the date of original
           global form, the date as of which any       issuance of the Debentures.  All other
           such Bearer Security or global Security     Debentures shall be dated the date of their
           shall be dated (if other than the date of   authentication.
           original issuance of the first of such
           Securities to be issued):
- --------------------------------------------------------------------------------------------------------
</TABLE> 
<PAGE>
 
                                      -4-

<TABLE>


- --------------------------------------------------------------------------------------------------------
<S>        <C>                                         <C>
Section    If any of the Securities are to be          Not applicable.
301 (6)    issuable as Bearer Securities, whether
           interest in respect of any portion of a
           temporary Bearer Security in global form
           payable in respect of an Interest Payment
           Date therefor prior to the Exchange Date,
           shall be paid to any clearing
           organization with respect to the portion
           of such temporary Bearer Security held
           for its account and, in such event, the
           terms and conditions (including any
           certification requirements) upon which
           any such interest payment received by a
           clearing organization will be credited to
           the Persons entitled to interest payable
           on such Interest Payment Date, if other
           than as provided in Section 304 of the
           Indenture:
- --------------------------------------------------------------------------------------------------------
Section    The date or dates, or the method or         The Stated Maturity of the principal of the
301 (7)    methods, if any, by which the date or       Debentures is January 15, 2005.
           dates shall be determined on which the
           principal of the Securities is payable:
- --------------------------------------------------------------------------------------------------------
Section    The rate or rates at which the Securities   The Debentures shall bear interest at the per
301 (8)    shall bear interest, if any, or the         annum rate of 4%. Interest shall accrue from
           method or methods, if any, by which such    the date of original issuance of the Debentures.
           rate or rates are to be determined; the     The Interest Payment Dates for the Debentures
           date or dates, if any, from which such      shall be January 15 and July 15 in each year,
           interest shall accrue or the method or      commencing July 15, 1998. The Regular Record Dates
           methods, if any, by which such date or      for the interest payable on such Interest
           dates are to be determined; the Interest    Payment Dates are January 1 and July 1,
           Payment Dates, if any, on which such        respectively.  Additional Amounts shall be
           interest shall be payable and the Regular   payable on the Debentures as set forth in the
           Record Date, if any, for the interest       Indenture.
           payable on Registered Securities on any
           Interest Payment Date; whether and under    
           what circumstances Additional Amounts on    
           such Securities or any of them shall be     
           payable; the notice, if any, to Holders   
           regarding the determination of interest
           on a floating rate Security and the
           manner of giving such notice, and the
           basis upon which interest shall be
           calculated if other than that of a
           360-day year of twelve 30-day months:
- --------------------------------------------------------------------------------------------------------

</TABLE> 
<PAGE>
 
                                      -5-

<TABLE>

- --------------------------------------------------------------------------------------------------------
<S>        <C>                                         <C>
Section    If in addition to or other than the         The Borough of Manhattan, The City of New York,
301 (9)    Borough of Manhattan, The City of New       in the case of Registered Debentures, and
           York (or, in the case of Bearer             London, England and Luxembourg, in the case of
           Securities, except as otherwise provided    Bearer Debentures, shall be the places where
           in the Indenture, London, England), the     principal of, any premium and interest on or any
           place or places where the principal of,     Additional Amounts with respect to such
           any premium and interest on or any          Debentures shall be payable, any of such
           Additional Amounts with respect to such     Debentures may be surrendered for registration
           Securities shall be payable, any of such    of transfer and exchange, any of such Debentures
           Securities may be surrendered for           may be surrendered for transfer, exchange or
           registration of transfer and exchange,      conversion in the circumstances described herein
           any of such Securities may be surrendered   and in the Indenture, and notices or demands to
           for transfer, exchange or conversion in     or upon the Company or the Guarantor in respect
           the circumstances described  herein and     of such Debentures and the Indenture may be
           in the Indenture, and notices or demands    served.
           to or upon the Company or the Guarantor
           in respect of such Securities and the
           Indenture may be served:                    Principal, premium (if any), interest payments
                                                       and Additional Amounts with respect to a global
                                                       Debenture will be paid in the manner set forth
                                                       in the Indenture.
- --------------------------------------------------------------------------------------------------------
Section    Whether any of the Securities are to be     The Debentures may be redeemed, at the option of
301 (10)   redeemable at the option of the Company     the Company, in whole or in part at any time on
           and, if so, the date or dates on which,     or after January 15, 2001, on the Redemption Date,
           the period or periods within which, the     upon notice as described in the Indenture, at
           price or prices at which and the other      the Redemption Price; provided, however, that
           terms and conditions upon which the         the Debentures may also be so redeemed on or
           Securities may be redeemed, in whole or     before January 15, 2001, on the Redemption Date, 
           in part, at the option of the Company       in the event of certain changes in United States
           and, if other than by a Company Board       taxation as set forth in the Indenture.
           Resolution, the manner in which any         
           election by the Company to redeem the       The Redemption Price shall be equal to 100% of     
           Securities shall be evidenced:              the principal amount of the Debentures, together   
                                                       with accrued interest to the date fixed for        
                                                       redemption, and any Additional Amounts then        
                                                       payable. (Section 1102)                             

- --------------------------------------------------------------------------------------------------------
</TABLE> 
<PAGE>
 
                                      -6-

<TABLE>

- --------------------------------------------------------------------------------------------------------
<S>        <C>                                         <C>
Section    If the Company is obligated to redeem or    The Debentures are subject to repayment at the
301 (11)   purchase any of the Securities pursuant     option of the Holder on the Repayment Date at
           to any sinking fund or analogous            the Repayment Price upon the occurrence of a
           provision or at the option of any Holder    Repayment Event. (Section 1502)
           thereof and, if so, the date or dates on                                                              
           which, the period or periods within         The Repayment Notice shall be given as set forth          
           which, the price or prices at which and     in the Indenture.  (Section 1503)                         
           the other terms and conditions upon which                                                              
           the Securities shall be redeemed or         Once a Holder of a Debenture shall deliver a               
           purchased, in whole or in part, pursuant    Debenture with the Option to Elect Repayment               
           to such obligation, and any provisions      duly completed and executed, such election to be           
           for the remarketing of the Securities so    repaid shall be irrevocable.  (Section 1504)               
           redeemed or purchased:                                                                                  
                                                       The terms Repayment Date, Repayment Price and               
                                                       Repayment Event shall have the meanings set                 
                                                       forth in the Indenture. (Section 1502)                      
- --------------------------------------------------------------------------------------------------------
Section    The denominations in which any of the       None, except that the global Registered
301 (12)   Securities that are Registered Securities   Debenture held by the Depository and the
           shall be issuable if other than             temporary global Bearer Debenture held by the
           denominations of $1,000 and any integral    Common Depository (or by a custodian or
           multiple thereof, and the denominations     depository therefor) shall be in such principal
           in which any of the Securities that are     amount as the officer(s) manually executing the
           Bearer Securities shall be issuable if      same shall approve, their manual execution
           other than the denominations of $1,000      thereof to be conclusive evidence of such
           and $10,000:                                approval.
- --------------------------------------------------------------------------------------------------------
Section    If other than the principal amount          Not applicable.
301 (13)   thereof, the portion of the principal
           amount of any of the Securities that
           shall be payable upon declaration of
           acceleration of the Maturity thereof
           pursuant to Section 502 of the Indenture
           or the method by which such portion is to
           be determined:
- --------------------------------------------------------------------------------------------------------

</TABLE> 
<PAGE>
 
                                      -7-

<TABLE>

- --------------------------------------------------------------------------------------------------------
<S>        <C>                                         <C>
Section    If the amount of payments of principal      Not applicable.
301 (14)   of, any premium or interest on or any
           Additional Amounts with respect to the
           Securities may be determined with
           reference to an index, indices, formula
           or other method or methods (which index,
           indices, formula or method or methods may
           be based, without limitation, on one or
           more currencies, commodities, equity
           indices or other indices), and, if so,
           the terms and conditions upon which and
           the manner in which such amounts shall be
           determined and paid or payable:
- --------------------------------------------------------------------------------------------------------
Section    Any deletions from, modifications of or     Not applicable.
301 (15)   additions to the Events of Default or
           covenants of the Company with respect to
           any of the Securities, whether or not
           such Events of Default or covenants are
           consistent with the Events of Default or
           covenants set forth in the Indenture:
- --------------------------------------------------------------------------------------------------------
Section    If either or both of Section 402(2)         Not applicable.
301 (16)   relating to defeasance or Section 402(3)
           relating to covenant defeasance, as set
           forth in the Indenture, shall be
           applicable to the Securities, or any
           covenants in addition to those specified
           in Section 402(3) of the Indenture
           relating to the Securities which shall be
           subject to covenant defeasance, and any
           deletions from, or modifications or
           additions to, the provisions of Article
           Four of the Indenture in respect of the
           Securities shall apply:
- --------------------------------------------------------------------------------------------------------


</TABLE> 
<PAGE>
 
                                      -8-

<TABLE>

- --------------------------------------------------------------------------------------------------------
<S>        <C>                                         <C>
Section    The terms, if any, on which the             The Debentures shall be convertible into shares
301 (17)   Securities may be converted into or         of Common Stock of the Company from the date of
           exchanged for other securities of the       the issuance thereof (except that the temporary
           Company:                                    global Bearer Debenture shall not be so
                                                       convertible) as provided in the Indenture, at an
                                                       initial Conversion Price (subject to adjustment
                                                       as provided in the Indenture) of $35.65 per
                                                       share.

                                                       The Company may not substitute cash or other
                                                       securities in lieu of the Common Stock to be
                                                       delivered upon conversion of the Debentures.
- --------------------------------------------------------------------------------------------------------
Section    If any of the Securities are to be          As set forth or provided in the Indenture.
301 (18)   issuable in global form and are to be
           issuable in definitive form (whether upon
           original issue or upon exchange of a
           temporary Security) only upon receipt of
           certain certificates or other documents
           or satisfaction of other conditions, then
           the form and terms of such certificates,
           documents or conditions:
- --------------------------------------------------------------------------------------------------------
Section    If there is more than one Trustee, the      The Trustee is:
301 (19)   identity of the Trustee and, if not the     
           Trustee, the identity of each Security      Bankers Trust Company                            
           Registrar, Paying Agent, Conversion Agent   Four Albany Street                               
           or Authenticating Agent with respect to     4th Floor                                        
           such Securities:                            New York, NY  10006                              
                                                       
                                                       The Trustee shall initially be the Security       
                                                       Registrar, one of the Authenticating Agents, the  
                                                       Conversion Agent and the Paying Agent with        
                                                       respect to the Debentures.                         
- --------------------------------------------------------------------------------------------------------
</TABLE> 
<PAGE>
 
                                      -9-

<TABLE>

- --------------------------------------------------------------------------------------------------------
<S>        <C>                                         <C>
Section    The subordination provisions with respect   The Debentures shall rank pari passu with the
301 (20)   to the Securities and Guarantees if other   following outstanding obligations of the
           than as set forth in Article Seventeen or   Company:  none.
           Eighteen, respectively, of the Indenture:   
                                                       The obligations represented by the Guarantees            
                                                       shall rank pari passu with the following                
                                                       outstanding obligations of the Guarantor: (i)           
                                                       obligations with respect to its 4 1/4%                  
                                                       Convertible Subordinated Debentures due 2003,           
                                                       (ii) subordinated guarantee of the 4 5/8%               
                                                       Convertible Subordinated Debentures due 2003            
                                                       issued by Thermo TerraTech Inc., the 3 3/4%             
                                                       Convertible Subordinated Debentures due 2000            
                                                       issued by Thermo Voltek Corp., the 4 7/8%               
                                                       Convertible Subordinated Debentures due 2000            
                                                       issued by Thermo Remediation Inc., the 5%               
                                                       Convertible Subordinated Debentures due 2000            
                                                       issued by ThermoQuest Corporation, the 5%               
                                                       Convertible Subordinated Debentures due 2000            
                                                       issued by Thermo Optek Corporation, the                 
                                                       Non-Interest Bearing Convertible Subordinated           
                                                       Debentures due 2001 and the 4 7/8% Convertible          
                                                       Subordinated Debentures due 2004 issued by              
                                                       Thermo Ecotek Corporation, the Non-Interest             
                                                       Bearing Convertible Subordinated Debentures due         
                                                       2003 issued by Thermedics Inc., the 4 3/4%              
                                                       Convertible Subordinated Debentures due 2004            
                                                       issued by Thermo Cardiosystems Inc., the 4 1/2%         
                                                       Convertible Subordinated Debentures due 2004            
                                                       issued by Thermo Fibertek Inc., the 4 3/8%              
                                                       Convertible Subordinated Debentures due 2004            
                                                       issued by ThermoLase Corporation and the 3 1/4%         
                                                       Convertible Subordinated Debentures due 2007            
                                                       issued by ThermoTrex Corporation, and (iii)             
                                                       obligations with respect to its subordinated            
                                                       guarantee of the obligations to redeem the              
                                                       common stock of ThermoLyte Corporation, Thermo          
                                                       Fibergen Inc. and ThermoLase Corporation.               
                                                                                                               
                                                       In addition to the Senior Indebtedness set forth        
                                                       or described in the Indenture, Senior                   
                                                       Indebtedness shall include, without limitation,         
                                                       the indebtedness represented by the following           
                                                       outstanding obligations of the Company: none.           
                                                                                                               
                                                       In addition to the Senior Guarantor Indebtedness        
                                                       set forth or described in the Indenture, Senior         
                                                       Guarantor Indebtedness shall include, without           
                                                       limitation, the indebtedness represented by the         
                                                       following outstanding obligations of the                
                                                       Guarantor:  none.                                        
- --------------------------------------------------------------------------------------------------------

</TABLE> 
<PAGE>
 
                                      -10-

<TABLE>

- --------------------------------------------------------------------------------------------------------
<S>        <C>                                         <C>
Section    Any other terms of the Securities and any   The form of the definitive Registered Debentures
301 (21)   deletions from or modifications or          is attached to this Certificate as Exhibit A.
           additions to the Indenture in respect of    The form of the Registered Debentures in global
           the Securities (which terms shall not be    form is attached to this Certificate as Exhibit
           inconsistent with the provisions of the     B.  The forms of the definitive Bearer
           Indenture, except as permitted by Section   Debentures and Coupons are attached to this
           901 thereof):                               Certificate as Exhibit C.  The form of the
                                                       temporary Bearer Debenture in global form is
                                                       attached to this Certificate as Exhibit D.
- --------------------------------------------------------------------------------------------------------
Section    Definition of Business Day, if other than   Not applicable.
101        as set forth in the Indenture:
- --------------------------------------------------------------------------------------------------------

- --------------------------------------------------------------------------------------------------------
 
Section    Definition of United States, if other       Not applicable.
101        than as set forth in the Indenture:
- --------------------------------------------------------------------------------------------------------

- --------------------------------------------------------------------------------------------------------
 
Section    The extent to which an Indexed Security     Not applicable.
101        is deemed Outstanding, if other than as
           set forth in the Indenture:
- --------------------------------------------------------------------------------------------------------
Section    Whether an Opinion of Counsel may not be    Not applicable.
101        given by an employee of the Company or
           Guarantor:
 
- --------------------------------------------------------------------------------------------------------
Section    Whether actions by Holders may not be       Not applicable.
104        taken by proxy:
- --------------------------------------------------------------------------------------------------------
Section    Whether notice of any event given to        Not applicable.
106        Holders shall be in a manner different
           than as set forth in the Indenture:
 
- --------------------------------------------------------------------------------------------------------
Section    Payment or conversion on a day other than   Not applicable.
114        a Business Day, if other than as set
           forth in the Indenture:
- --------------------------------------------------------------------------------------------------------

</TABLE> 
<PAGE>
 
                                      -11-

<TABLE>

- --------------------------------------------------------------------------------------------------------
<S>        <C>                                         <C>
Section    Whether the Securities are issued with or   The Debentures are guaranteed on a subordinated
202        without Guarantees:                         basis by Thermo Electron, as provided in the
                                                       Indenture.
- --------------------------------------------------------------------------------------------------------
Section    Whether the Securities initially shall be   Not applicable.
204        issued in other than global form:
 
- --------------------------------------------------------------------------------------------------------
Section    Whether payment of principal of, any        Not applicable.
204        premium and (except for temporary global
           Bearer Securities) interest on, and any
           Additional Amounts in respect of, any
           temporary or permanent global Security
           shall be made to a Person or Persons
           other than the Person or Persons
           specified therein:
 
- --------------------------------------------------------------------------------------------------------
Section    The Persons whom the Trustee or any agent   Notwithstanding the provisions of Section 308
204        of the Company or the Trustee shall treat   and except as provided in the penultimate
           as the Holder of the principal amount of    paragraph of Section 204, the Company, the
           the temporary global Bearer Security:       Trustee or any agent of the Company and the
                                                       Trustee shall treat the Common Depository as the
                                                       Holder of the principal amount of the temporary
                                                       global Bearer Security.
 
- --------------------------------------------------------------------------------------------------------
Section    Whether temporary Securities (other than    The temporary Debentures, until so exchanged for
304(b)     temporary global Bearer Securities),        Definitive Debentures of such series, will be
           until exchanged for Definitive Securities   entitled to the same benefits under the
           of such series, will be entitled to the     Indenture as Definitive Debentures of such
           same benefits under the Indenture as        series.
           Definitive Securities of such series:
- --------------------------------------------------------------------------------------------------------
Section    Whether temporary global Bearer             Temporary global Bearer Debentures shall in all
304(c)     Securities shall have the same rights and   respects be entitled to the same rights and
           benefits as definitive Bearer Securities:   benefits as definitive Bearer Debentures, except
                                                       that Euroclear, Cedel or the beneficial owner,
                                                       as applicable, must exchange the temporary
                                                       global Bearer Debenture for definitive
                                                       Debentures before interest payments or other
                                                       payments thereon are collected or conversion
                                                       rights exercised.
- --------------------------------------------------------------------------------------------------------

</TABLE> 
<PAGE>
 
                                      -12-

<TABLE>

- --------------------------------------------------------------------------------------------------------
<S>        <C>                                         <C>
Section    The terms on which a permanent global       Not applicable.
305        Registered Security shall be exchangeable
           for definitive Securities, if other than
           as set forth in the Indenture:
- --------------------------------------------------------------------------------------------------------
Section    The terms under which holders of            Not applicable.
305        definitive Registered Securities and
           Bearer Securities may exchange such
           interest for securities in global form,
           if other than as set forth in the
           Indenture:
- --------------------------------------------------------------------------------------------------------
Section    The terms on which interest on Bearer       Not applicable.
306        Securities shall be paid without
           presentation and surrender of the
           applicable Coupon, if other than as set
           forth in the Indenture:
- --------------------------------------------------------------------------------------------------------
Section    The person or persons to receive payments   Not applicable.
307(a)     with respect to Registered Securities, if
           other than the registered holder
           (including DTC) thereof on the Regular
           Record Date:
- --------------------------------------------------------------------------------------------------------
Section    Manner in which payments of interest        Not applicable.
307(a)     shall be made if other than as set forth
           in the Indenture:
- --------------------------------------------------------------------------------------------------------
Section    The terms on which a Bearer Security may    Not applicable.
307(a)     be exchanged for a Registered Security
           after a Regular Record Date and before an
           Interest Payment Date, if other than as
           set forth in the Indenture:
- --------------------------------------------------------------------------------------------------------
Section    Circumstances under which payments on a     Not applicable.
307(a),    Bearer Security may be paid in the United
1002       States, if other than as set forth in the
           Indenture:
- --------------------------------------------------------------------------------------------------------
Section    Method of paying interest, by check or      Not applicable.
307(a)     wire transfer or both, if other than as
           set forth in the Indenture:
- --------------------------------------------------------------------------------------------------------

</TABLE> 
<PAGE>
 
                                      -13-

<TABLE>

- --------------------------------------------------------------------------------------------------------
<S>        <C>                                         <C>
Section    The terms on which Defaulted Interest       Not applicable.
307(b)     shall be paid with respect to Registered
           Securities, if other than as set forth in
           the Indenture:
- --------------------------------------------------------------------------------------------------------
Section    Whether Securities or Coupons shall be      Not applicable.
309        authenticated in lieu of or in exchange
           for any Securities or Coupons canceled as
           provided in Section 309 of the Indenture,
           except as expressly permitted by or
           pursuant to the Indenture:
- --------------------------------------------------------------------------------------------------------
Section    Qualifications for an Authenticating        Not applicable.
612        Agent, if other than as set forth in the
           Indenture:
- --------------------------------------------------------------------------------------------------------
Section    Dates upon which the Company and the        Not applicable.
701(1)     Guarantor will furnish names and
           addresses of Holders, if other than as
           set forth in the Indenture:
- --------------------------------------------------------------------------------------------------------
Section    Whether the Company shall be required to    The Company shall not be required to deposit
1105       deposit with the Trustee the accrued        with the Trustee the accrued interest on and any
           interest on and any Additional Amounts      Additional Amounts with respect to Debentures
           with respect to Securities being redeemed   being redeemed if the Redemption Date shall be
           if the Redemption Date shall be an          an Interest Payment Date.
           Interest Payment Date:
- --------------------------------------------------------------------------------------------------------
Section    Whether installments of interest on         Not applicable.
1106       Bearer Securities whose Stated Maturity
           is on or prior to the Redemption Date
           shall be payable other than upon the
           presentation and surrender of the Coupons
           for such interest:
- --------------------------------------------------------------------------------------------------------
Section    Whether installments of interest on         Not applicable.
1106       Registered Securities whose Stated
           Maturity is on or prior to the Redemption
           Date shall be payable to the Holders of
           such Securities registered as such at the
           close of business on the Regular Record
           Date:
- --------------------------------------------------------------------------------------------------------
</TABLE> 
<PAGE>
 
                                      -14-

<TABLE>

- --------------------------------------------------------------------------------------------------------
<S>        <C>                                         <C>
           Issue price to public of Securities of      One hundred percent (100%) of the principal
           the Series:                                 amount of the Debentures.
- --------------------------------------------------------------------------------------------------------
           Underwriters' commission or discount as a   2 1/4 percent (2 1/4%)
           percentage of the principal amount of       
           Securities of the Series to be issued:      
                                                       
- --------------------------------------------------------------------------------------------------------
</TABLE>



                   REMAINDER OF PAGE INTENTIONALLY LEFT BLANK
<PAGE>
 
                                      -15-

IN WITNESS WHEREOF, the undersigned have executed this Certificate on behalf of
the Company and Thermo Electron.

                              THERMO INSTRUMENT SYSTEMS INC.


                              By: /s/ Melissa F. Riordan
                                 _______________________________________
                                  Name:  Melissa F. Riordan
                                  Title  Treasurer


                              By: /s/ Sandra Lambert
                                 _______________________________________
                                  Name:   Sandra Lambert
                                  Title:  Corporate Secretary


                              THERMO ELECTRON CORPORATION


                              By: /s/ Melissa F. Riordan
                                 _______________________________________
                                  Name:   Melissa F. Riordan
                                  Title:  Treasurer


                              By: /s/ Sandra Lambert
                                 _______________________________________
                                  Name:  Sandra Lambert
                                  Title: Corporate Secretary

Dated as of January 15, 1998
<PAGE>
 
                                                                     EXHIBIT A



                    (FORM OF FACE OF REGISTERED SECURITIES)

                        THERMO INSTRUMENT SYSTEMS INC.
                    (Incorporated in the State of Delaware)


                     4% CONVERTIBLE SUBORDINATED DEBENTURE
                             DUE JANUARY 15, 2005
                     GUARANTEED ON A SUBORDINATED BASIS BY
                          THERMO ELECTRON CORPORATION
                    (Incorporated in the State of Delaware)

No. R-
      __________

Cusip: 883559AE6
      __________
 
         Thermo Instrument Systems Inc., a Delaware corporation (herein referred
to as the "Company," which term includes any successor corporation under the
Indenture referred to on the reverse hereof), for value received, hereby
promises to pay to ____________________ or registered assigns the principal sum
of _______ Dollars plus any premium, if any, on January 15, 2005 (the "Stated
Maturity") upon the presentation and surrender hereof or, at the option of the
Company, in whole or in part at any time on or after January 15, 2001, upon
notice as described in the Indenture and to pay interest thereon from January
21, 1998 or from the most recent Interest Payment Date to which interest has
been paid or duly provided for, semi-annually in arrears on January 15 and July
15 in each year (each, an "Interest Payment Date"), commencing July 15, 1998, at
the rate of 4% per annum, and Additional Amounts, if any, until the principal
hereof is paid or duly provided for. The interest and Additional Amounts, if
any, so payable, and punctually paid or duly provided for, on any Interest
Payment Date will, as provided in such Indenture, be paid to the Holder in whose
name this Security (or one or more Predecessor Securities) is registered at the
close of business on the Regular Record Date for such interest, which shall be
the January 1 or July 1 (whether or not a Business Day), as the case may be,
next preceding such Interest Payment Date at the Office or Agency of the Company
maintained for such purpose; provided, however, that such interest may be paid,
at the Company's option, by mailing a check to such Holder at its registered
address or by transfer of funds to an account maintained by such Holder within
the United States. Any such interest not so punctually paid or duly provided for
shall forthwith cease to be payable to the Holder on such Regular Record Date,
and may be paid to the Holder in whose name this Security (or one or more
Predecessor Securities) is registered at the close of business on a Special
Record Date for the payment of such Defaulted Interest to be fixed by the
Trustee, notice whereof shall be given to Holders of Securities of this series
not less than 10 days prior to such Special Record Date, or may be paid at any
time in any other lawful manner not inconsistent with the requirements of any
securities exchange on which the Securities of this series may be listed, and
upon such notice as may be required by such exchange, all as more fully provided
in the Indenture. Interest will be computed on the basis of a 360-day year of
twelve 30-day months. All payments hereunder shall be made in United States
Dollars.
<PAGE>
 
         Reference is hereby made to the further provisions of this Security set
forth on the reverse hereof, which further provisions shall for all purposes
have the same effect as if set forth at this place.

         Unless the Certificate of Authentication hereon has been executed by
the Trustee by manual signature of one of its authorized signatories, this
Security shall not be entitled to any benefit under the Indenture, or be valid
or obligatory for any purpose.

                                      -2-
<PAGE>
 
         IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed under its facsimile corporate seal.

Dated:  January __, 1998                      THERMO INSTRUMENT SYSTEMS
                                              INC.

                                              By:_______________________
Attest:                                          [Name]
                                                 [Title]
_____________________________
Secretary

[SEAL]




                         CERTIFICATE OF AUTHENTICATION

         This is one of the Securities of the series designated therein referred
to in the within-mentioned Indenture.

                                              BANKERS TRUST COMPANY,
                                              as Trustee


                                              By:
                                                 ____________________________
                                                 Authorized Officer

                                      -3-
<PAGE>
 
                  (FORM OF REVERSE OF REGISTERED SECURITIES)

                        THERMO INSTRUMENT SYSTEMS INC.

This Security is one of a duly authorized issue of securities of the Company
(herein called the "Securities"), issued and to be issued in one or more series
under an Indenture, dated as of January 15, 1998 (herein called the "Indenture")
by the Company, as issuer, and Thermo Electron Corporation, as guarantor (herein
called the "Guarantor," which term includes any successor corporation under the
Indenture), to Bankers Trust Company, as Trustee (herein called the "Trustee,"
which term includes any successor trustee under the Indenture with respect to
the series of which this Security is a part), to which Indenture and all
indentures supplemental thereto reference is hereby made for a statement of the
respective rights, limitations of rights, duties and immunities thereunder of
the Company, the Guarantor, the Trustee and the Holders of the Securities and
any Coupons appertaining thereto, and of the terms upon which the Securities
are, and are to be, authenticated and delivered. This Security is one of the
duly authorized series of Securities designated on the face hereof and the
aggregate principal amount of the Securities to be issued under such series is
limited to $250,000,000 (except for Securities authenticated and delivered upon
transfer of, or in exchange for, or in lieu of other Securities). The Guarantor
has unconditionally guaranteed on a subordinated basis the payment of principal,
premium, if any, and interest on the Securities. The Holders of the Securities
will be entitled to the benefits of, be bound by, and be deemed to have notice
of, all of the provisions of the Indenture. A copy of the Indenture is on file
and may be inspected at the office of the Paying Agents appointed by the
Company. All terms used in this Security which are defined in the Indenture
shall have the meanings assigned to them in the Indenture.

         The Securities are issuable as bearer securities (the "Bearer
Securities"), with interest Coupons attached, in the denominations of U.S.
$1,000 and U.S. $10,000, and as registered securities (the "Registered
Securities"), without Coupons, in denominations of U.S. $1,000 and integral
multiples thereof, except as otherwise provided in or pursuant to the Indenture.
The Registered Securities, and transfers thereof, shall be registered as
provided in the Indenture. The holder of any Bearer Security or any Coupon
appertaining thereto and the registered holder of a Registered Security shall
(to the fullest extent permitted by applicable law) be treated at all times, by
all persons and for all purposes as the absolute owner of such Security or
Coupon, as the case may be, regardless of any notice of ownership, theft or loss
or of any writing thereon. Bearer Securities may be exchanged for Registered
Securities as set forth in the Indenture. Registered Securities may not be
exchanged for Bearer Securities.

         The Securities are general, unsecured obligations of the Company,
subordinated in right of payment to the prior payment in full of all existing
and future Senior Indebtedness of the Company to the extent set forth in Article
Seventeen of the Indenture. There are no restrictions herein on other
indebtedness or securities which may be incurred or issued by the Company or the
Guarantor.

         Additional Amounts shall be payable on the Securities as set forth in
the Indenture.

                                      -4-
<PAGE>
 
         If an Event of Default, as defined in the Indenture, shall occur and be
continuing, the principal of the Securities of this series may be declared due
and payable in the manner and with the effect provided in the Indenture.

         Subject to the terms of the Indenture, the Securities are convertible
at any time prior to Maturity at an initial Conversion Price of $35.65 per
share, subject to adjustment as provided in the Indenture. Accrued interest from
the immediately preceding Interest Payment Date until the Conversion Date will
be paid within five Business Days after the Conversion Date. In case this
Security, or a portion thereof, is called for redemption, or is delivered for
repayment, the conversion right in respect of this Security or a portion thereof
so called and delivered shall expire on the close of business on the fifth
Business Day preceding the Redemption Date or the second Business Day preceding
a repayment on the Repayment Date, as the case may be, unless the Company
defaults in making the payment due upon redemption or repayment, as the case may
be. To convert this Security, the Holder must surrender this Security, duly
endorsed or assigned to the Company, at any applicable Place of Conversion,
accompanied by a duly signed conversion notice. Bearer Securities surrendered
for conversion must be surrendered together with all Coupons appertaining
thereto that mature after the Conversion Date, except as otherwise provided in
the Indenture.

         The Securities are subject to redemption at any time on or after
January 15, 2001, as a whole or in part, at the option of the Company, at a
Redemption Price equal to 100% of the principal amount, together in the case of
any such redemption with accrued interest to the Redemption Date as provided in
the Indenture. Notice of redemption will be given to Holders of Securities, not
less than 20 nor more than 60 days prior to the Redemption Date, all as provided
in the Indenture. Subject to the terms of the Indenture, if as a result of a Tax
Law Change the Company has or will become obligated to pay to the Holder of any
Tax Affected Security Additional Amounts, and such obligation cannot be avoided
by the Company taking reasonable measures available to it, then the Company may,
at its option, redeem the Tax Affected Securities as a whole, but not in part,
upon not less than 20 nor more than 60 days' notice to the Holders prior to the
Redemption Date therefor, at a Redemption Price equal to 100% of the principal
amount plus interest accrued to the Redemption Date, and any Additional Amounts
then payable.

         Subject to the terms of the Indenture, the Securities are subject to
repayment at the option of the Holder thereof, in whole or in part, on the
Repayment Date, if the Common Stock (or other equity securities into which this
Security is then convertible) is neither listed for trading on a United States
national securities exchange, the Nasdaq National Market nor approved for
trading on an established automated over-the-counter trading market in the
United States. In such event, the Securities shall be repaid at a price equal to
the principal amount hereof, plus accrued interest and Additional Amounts, if
any. The Holders of Securities of this series desiring to be repaid must deliver
(1) this Security with the "Option to Elect Repayment" duly signed and
completed, or (2) such other documentation as may be provided by the Indenture,
to the Trustee at the Place of Payment not earlier than 60 days nor later than
30 days prior to the Repayment Date. Bearer Securities must be surrendered
together with all Coupons appertaining thereto that mature after the Repayment
Date, except as otherwise provided in the Indenture.

                                      -5-
<PAGE>
 
         In the event of redemption, exchange, repayment or conversion of this
Security in part only, a new Security or Securities for the unredeemed,
unexchanged, unrepaid or unconverted portion hereof shall be issued in the name
of the Holder hereof upon the cancellation hereof as set forth in the Indenture.

         The Place of Payment, place of registration of transfer and exchange
and the Place of Conversion for the Registered Securities and the Guarantees
endorsed thereon, shall be the Borough of Manhattan, The City of New York, and
the Corporate Trust Office of the Trustee shall be the Company's and the
Guarantor's Office or Agency in the Borough of Manhattan, The City of New York
for such purpose. The Places of Payment and Places of Conversion for the Bearer
Securities and the Guarantees endorsed thereon, shall be London, England and
Luxembourg, and the offices of the Trustee in London and Luxembourg shall be the
Offices or Agencies for such purpose and the offices of the Trustee in London
and Luxembourg shall be the Company's and the Guarantor's Paying Agent in London
and Luxembourg, respectively.

         The Trustee initially shall be the Security Registrar, one of the
Authenticating Agents, the Paying Agent and the Conversion Agent. The Trustee
presently has its Corporate Trust Office at Four Albany Street, 4th Floor, New
York, NY 10006, its Office in London at 1 Appold Street, Broadgate, London, EC2A
2HE, England, and its Office in Luxembourg at 14 Boulevard F.D. Roosevelt,
L-2450 Luxembourg. The Company and the Guarantor may subsequently appoint an
Office or Agency in addition to or other than the Borough of Manhattan, The City
of New York with respect to the Registered Securities and London, England and
Luxembourg with respect to the Bearer Securities.

         The Indenture permits, with certain exceptions as therein provided, the
amendment thereof and the modification of the rights and obligations of the
Company and the Guarantor and the rights of the Holders of the Securities under
the Indenture at any time by the Company, the Guarantor and the Trustee with the
consent of the Holders of not less than a majority of the aggregate principal
amount of all Securities issued under the Indenture at the time Outstanding and
affected thereby. The Indenture also contains provisions permitting the Holders
of not less than a majority of the aggregate principal amount of the Outstanding
Securities, on behalf of the Holders of all such Securities, to waive compliance
by the Company and the Guarantor with certain provisions of the Indenture.
Furthermore, provisions in the Indenture permit the Holders of not less than a
majority of the aggregate principal amount, in certain instances, of the
Outstanding Securities of any series to waive, on behalf of all of the Holders
of Securities of such series, certain past defaults under the Indenture and
their consequences. Any such consent or waiver by the Holder of this Security
shall be conclusive and binding upon such Holder and upon all future Holders of
this Security and other Securities issued upon the registration of transfer
hereof or in exchange herefor or in lieu hereof, whether or not notation of such
consent or waiver is made upon this Security.

         No reference herein to the Indenture and no provision of this Security
or of the Indenture shall alter or impair the obligation of the Company, which
is absolute and unconditional (except as to the specific subordination
provisions contained in Article Seventeen of the Indenture), to

                                      -6-
<PAGE>
 
pay the principal of, premium, if any, interest and Additional Amounts, if any,
on this Security at the times, places and rates, and in the coin or currency,
herein prescribed.

         No service charge shall be made for any registration of transfer or
exchange, but the Company may require payment of a sum sufficient to cover any
tax or other governmental charge payable in connection therewith.

         The Indenture and the Securities shall be governed by and construed in
accordance with the laws of the Commonwealth of Massachusetts applicable to
agreements made and to be performed entirely in such Commonwealth except that
the rights, protections, obligations, indemnities and immunities of the Trustee
under the Indenture and the Securities shall be governed by the laws of the
State of New York, without regard to the principles of conflicts of laws of
either state.

                                      -7-
<PAGE>
 
                                   GUARANTEE

         For value received, Thermo Electron Corporation, a corporation
organized under the laws of the State of Delaware (herein called the
"Guarantor," which term includes any successor corporation under the Indenture
referred to in the Security upon which this Guarantee is endorsed), hereby
unconditionally guarantees to the Holder of the Security upon which this
Guarantee is endorsed and to the Trustee on behalf of the Trustee and such
Holder the due and punctual payment of the principal of, premium, if any, and
interest and Additional Amounts, if any, on such Security, any other amount due
and payable pursuant to the terms of the Indenture and the due and punctual
payment of the sinking fund or analogous payments referred to therein if any,
when and as the same shall become due and payable, whether at the Stated
Maturity, by declaration of acceleration, call for redemption, repayment at the
option of the Holder or otherwise, according to the terms thereof and of the
Indenture. In case of the failure of Thermo Instrument Systems Inc., a
corporation organized under the laws of Delaware (herein called the "Company,"
which term includes any successor corporation under such Indenture), punctually
to make any such payment of principal, premium, if any, or interest or
Additional Amounts, if any, the Guarantor hereby agrees to cause any such
payment to be made punctually when and as the same shall become due and payable,
whether at the Stated Maturity or by declaration of acceleration, call for
redemption, repayment at the option of the Holder or otherwise, and as if such
payment were made by the Company.

         The Guarantor hereby agrees that its obligations hereunder shall be as
if it were principal debtor and not merely surety, and shall be absolute and
unconditional (except as to the specific subordination provisions contained in
Article Eighteen of the Indenture), irrespective of, and shall be unaffected by,
any invalidity, subordination, irregularity or unenforceability of such Security
or such Indenture, any failure to enforce the provisions of such Security or
such Indenture, or any waiver, modification or indulgence granted to the Company
with respect thereto, by the Holder of such Security or the Trustee or any other
circumstance which may otherwise constitute a legal or equitable discharge of a
surety or guarantor. The Guarantor hereby waives the benefits of diligence,
presentment, demand of payment, filing of claims with a court in the event of
merger, insolvency or bankruptcy of the Company, any right to require a
proceeding first against the Company, protest or notice with respect to such
Security or the indebtedness evidenced thereby and all demands whatsoever, and
covenants that this Guarantee will not be discharged except by strict and
complete performance of the obligations contained in such Security and this
Guarantee. The Guarantor hereby agrees that, in the event of a default in
payment of principal of, premium, if any, and interest, and Additional Amounts,
if any, on such Security, or default in any sinking fund or analogous payment
referred to therein, legal proceedings may be instituted by the Trustee on
behalf of, or by, the Holder of such Security, on the terms and conditions set
forth in the Indenture, directly against the Guarantor to enforce this Guarantee
without first proceeding against the Company.

         The Guarantor shall be subrogated to all rights of the Holder of such
Security and the Trustee against the Company in respect of any amounts paid to
such Holder by the Guarantor on account of such Security pursuant to the
provisions of this Guarantee or the Indenture; provided, however, that the
                                               --------  -------  
Guarantor shall not be entitled to enforce, or to receive any payments arising

                                      -8-
<PAGE>
 
out of or based upon, such right of subrogation until the principal of, premium,
if any, and interest and Additional Amounts, if any, on all Securities issued
under such Indenture shall have been paid in full.

         Claims under this Guarantee are, to the extent provided in the
Indenture, subject in right of payment to the prior payment in full of all
Senior Guarantor Indebtedness, and this Guarantee is issued subject to the
provisions of the Indenture with respect thereto. Each Holder of a Security upon
which this Guarantee is endorsed, by accepting the same, (a) agrees to and shall
be bound by such provisions, (b) authorizes and directs the Trustee on his
behalf to take such action as may be necessary or appropriate to effectuate the
subordination so provided and (c) appoints the Trustee his, her or its
attorney-in-fact for any and all such purposes.

         No reference herein to such Indenture and no provision of this
Guarantee or of such Indenture shall alter or impair the guarantee of the
Guarantor, which is absolute and unconditional (except as to the specific
subordination provisions contained in Article Eighteen of the Indenture), of the
due and punctual payment of principal, premium (if any), and interest and
Additional Amounts, if any, on the Security upon which this Guarantee is
endorsed.

         This Guarantee shall not be valid or obligatory for any purpose until
the certificate of authentication of the Security upon which this Guarantee is
endorsed shall have been manually executed by or on behalf of the Trustee under
such Indenture.

         All terms used in this Guarantee which are defined in such Indenture
shall have the meanings assigned to them in such Indenture.

         This Guarantee shall be deemed to be a contract made under the laws of
the Commonwealth of Massachusetts, and for all purposes shall be governed by and
construed in accordance with the laws of the Commonwealth of Massachusetts.

         IN WITNESS WHEREOF, the Guarantor has caused this Guarantee to be duly
executed under its corporate seal and dated the date on the face hereof.

                                            THERMO ELECTRON CORPORATION


Attest:______________________________       By: ________________________________

                                            Title: _____________________________

                                      -9-
<PAGE>
 
         This is one of the Securities of the series designated therein referred
to in the within-mentioned Indenture.

Dated:  _______________________                   BANKERS TRUST COMPANY,
                                                  as Trustee



                                                  By: __________________________
                                                      Authorized Officer

                                      -10-
<PAGE>
 
                                TRANSFER NOTICE


FOR VALUE RECEIVED, the undersigned Holder hereby sell(s), assign(s) and
transfer(s) unto______________________________________________________________
______________________________________________________________________________
whose taxpayer identification number is _____________________ and whose address
including postal/zip code is _____________________________________ the within
Security and all rights thereunder, hereby irrevocably constituting and
appointing _____________________________ attorney-in-fact to transfer said
Security on the books of the Security Registrar with full power of substitution
in the premises.


Dated:___________________                            Name:______________________

                                                     By:________________________

                                                     Title:_____________________

                                                     NOTICE: The signature of
                                                     the Holder to this
                                                     assignment must correspond
                                                     with the name as written
                                                     upon the face of the within
                                                     instrument in every
                                                     particular, without
                                                     enlargement or any change
                                                     whatsoever.

                                                     SIGNATURE GUARANTEED

                                                     ___________________________

                                      -11-
<PAGE>
 
                               CONVERSION NOTICE



         The undersigned Holder of this Security hereby irrevocably exercises
the option to convert this Security, or any portion of the principal amount
hereof (which is an integral multiple of U.S. $1,000 below designated), into
shares of Common Stock in accordance with the terms of the Indenture referred to
in this Security, and directs that such shares, together with a check in payment
for any fractional share and any Securities representing any unconverted
principal amount hereof, be delivered to and be registered in the name of the
undersigned unless a different name has been indicated below. If shares or
Securities are to be registered in the name of a Person other than the
undersigned, the undersigned will pay all transfer taxes payable with respect
thereto.


Dated:------------------------------         ---------------------------------
                                                         Signature
                                             [MUST BE GUARANTEED IF STOCK
                                             OR SECURITIES ARE TO BE ISSUED IN
                                             A NAME OTHER THAN THE  REGISTERED
                                             HOLDER OF THE SECURITY]


- ------------------------------------
               Name

- ------------------------------------
               Address

- ------------------------------------
Social Security or other Taxpayer
Identification Number, if any

                                      -12-
<PAGE>
 
If shares or Registered Securities are to    If only a portion of the
be registered in the name of a Person        Securities is to be converted,
other than the Holder, print such            please please indicate:   
Person's name and address:    


                                             1. Principal amount to be
                                                converted:

                                             U.S. $___________________

_______________________________              2.  Principal amount and
           Name                                  denomination of Registered
                                                 Securities representing
                                                 unconverted principal amount
                                                 to be issued.
_______________________________
           Address
                                             Amount:  U.S.$_________________
_______________________________
Social Security or other Taxpayer            Denominations:
Identification Number, if any                U.S.$__________
                                             (any integral multiple of U.S.
                                             $1,000)

_______________________________

                                      -13-
<PAGE>
 
                           OPTION TO ELECT REPAYMENT
                            UPON A REPAYMENT EVENT


To:      Thermo Instrument Systems Inc.

         The undersigned owner of this Security hereby acknowledges receipt of a
notice from Thermo Instrument Systems Inc.(the "Company") as to the occurrence
of a Repayment Event with respect to the Common Stock of the Company and
requests and instructs the Company to repay the entire principal amount of this
Security, or the portion thereof (which is $1,000 or an integral multiple
thereof) below designated, in accordance with the terms of the Indenture
referred to in this Security at the Repayment Price (or the relevant percentage
thereof), together with accrued interest to such date (except if the Repayment
Date shall be an Interest Payment Date), to the holder hereof.


Dated: ________________________


                                                 _______________________________
                                                 Signature*(s)

                                                 Name: _______________________
                                                 Address:_____________________
                                                         _____________________
                                                 [* Signature Guarantee 
                                                 Required]

                                                 Principal amount to be repaid
                                                 (if less than all):

                                                 $__________

                                                 NOTICE: If this Security is
                                                 issued in registered form, the
                                                 above signatures of the
                                                 holder(s) hereof must
                                                 correspond with the name as it
                                                 appears in the Security in
                                                 every particular without
                                                 alteration or enlargement or
                                                 any change whatever.


____________________________
Social Security or Other
Taxpayer Identification Number

                                      -14-
<PAGE>
 
                                                                    EXHIBIT B

                (FORM OF FACE OF REGISTERED GLOBAL SECURITIES)

Unless this Security is presented by an authorized representative of The
Depository Trust Company ("DTC"), 55 Water Street, New York, New York to the
issuer or its agent for registration of transfer, exchange or payment, and such
Security issued is registered in the name of CEDE & CO., or such other name as
requested by an authorized representative of DTC, ANY TRANSFER, PLEDGE OR OTHER
USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL, since the
registered owner hereof, CEDE & CO., has an interest herein.

Unless and until this Security is exchanged in whole or in part for Securities
in certificated form, this Security may not be transferred except as a whole by
DTC to a nominee thereof or by a nominee thereof to DTC or another nominee of
DTC or by DTC or any such nominee to a successor of DTC or a nominee of such
successor.

                        THERMO INSTRUMENT SYSTEMS INC.
                    (Incorporated in the State of Delaware)


                 4% CONVERTIBLE SUBORDINATED GLOBAL DEBENTURE
                             DUE JANUARY 15, 2005
                     GUARANTEED ON A SUBORDINATED BASIS BY
                          THERMO ELECTRON CORPORATION
                    (Incorporated in the State of Delaware)

No. R-________________

Cusip: 883559AE6
      ________________

     Thermo Instrument Systems Inc., a Delaware corporation (herein referred
to as the "Company," which term includes any successor corporation under the
Indenture referred to on the reverse hereof), for value received, hereby
promises to pay to Cede & Co. or registered assigns the principal sum of _______
Dollars (or any other amounts as are endorsed on the Schedule of Adjustments
hereto) plus any premium, if any, on January 15, 2005 (the "Stated Maturity")
upon the presentation and surrender hereof or, at the option of the Company, in
whole or in part at any time on or after January 15, 2001, upon notice as
described in the Indenture and to pay interest thereon from January 21, 1998 or
from the most recent Interest Payment Date to which interest has been paid or
duly provided for, semi-annually in arrears on January 15 and July 15 in each
year (each, an "Interest Payment Date"), commencing July 15, 1998, at the rate
of 4% per annum, and Additional Amounts, if any, until the principal hereof is
paid or duly provided for. The interest and Additional Amounts, if any, so
payable, and punctually paid or duly provided for, on any Interest Payment Date
will, as provided in such Indenture, be paid to the Holder in whose name this
Security (or one or more Predecessor Securities) is registered at the close of
business on the Regular Record Date for such interest, which shall be the
January 1 or July 1 (whether or not a Business Day), as the case may be, next
preceding such Interest
<PAGE>
 
Payment Date at the Office or Agency of the Company maintained for such
purpose; provided, however, that such interest may be paid, at the Company's
         --------  -------
option, by mailing a check to such Holder at its registered address or by
transfer of funds to an account maintained by such Holder within the United
States. Any such interest not so punctually paid or duly provided for shall
forthwith cease to be payable to the Holder on such Regular Record Date, and may
be paid to the Holder in whose name this Security (or one or more Predecessor
Securities) is registered at the close of business on a Special Record Date for
the payment of such Defaulted Interest to be fixed by the Trustee, notice
whereof shall be given to Holders of Securities of this series not less than 10
days prior to such Special Record Date, or may be paid at any time in any other
lawful manner not inconsistent with the requirements of any securities exchange
on which the Securities of this series may be listed, and upon such notice as
may be required by such exchange, all as more fully provided in the Indenture.
Interest will be computed on the basis of a 360-day year of twelve 30-day
months. All payments hereunder shall be made in United States Dollars.

     Subject to the applicable provisions of the Indenture, the aggregate
principal amount represented by this global Security may be decreased to reflect
exchanges or partial conversions, redemptions or repayments, by endorsing the
Schedule of Adjustments hereto, and the principal amount hereof shall be deemed
to be decreased for all purposes by the amount so exchanged, converted, redeemed
or repaid, as applicable.

     Reference is hereby made to the further provisions of this Security set
forth on the reverse hereof, which further provisions shall for all purposes
have the same effect as if set forth at this place.

     Unless the Certificate of Authentication hereon has been executed by
the Trustee by manual signature of one of its authorized signatories, this
Security shall not be entitled to any benefit under the Indenture, or be valid
or obligatory for any purpose.

                                      -2-
<PAGE>
 
     IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed under its facsimile corporate seal.

Dated:  January __, 1998                     THERMO INSTRUMENT SYSTEMS INC.

                                             By:_______________________
Attest:                                          [Name]
                                                 [Title]
_______________________________
Secretary

[SEAL]


                          CERTIFICATE OF AUTHENTICATION

         This is one of the Securities of the series designated therein referred
to in the within-mentioned Indenture.

                                                  BANKERS TRUST COMPANY,
                                                  as Trustee


                                                  By:________________________
                                                      Authorized Officer

                                      -3-
<PAGE>
 
               (FORM OF REVERSE OF REGISTERED GLOBAL SECURITIES)

                        THERMO INSTRUMENT SYSTEMS INC.


     This Security is one of a duly authorized issue of securities of the
Company (herein called the "Securities"), issued and to be issued in one or more
series under an Indenture, dated as of January 15, 1998 (herein called the
"Indenture") by the Company, as issuer, and Thermo Electron Corporation, as
guarantor (herein called the "Guarantor," which term includes any successor
corporation under the Indenture), to Bankers Trust Company, as Trustee (herein
called the "Trustee," which term includes any successor trustee under the
Indenture with respect to the series of which this Security is a part), to which
Indenture and all indentures supplemental thereto reference is hereby made for a
statement of the respective rights, limitations of rights, duties and immunities
thereunder of the Company, the Guarantor, the Trustee and the Holders of the
Securities and any Coupons appertaining thereto, and of the terms upon which the
Securities are, and are to be, authenticated and delivered. This Security is one
of the duly authorized series of Securities designated on the face hereof and
the aggregate principal amount of the Securities to be issued under such series
is limited to $250,000,000 (except for Securities authenticated and delivered
upon transfer of, or in exchange for, or in lieu of other Securities). The
Guarantor has unconditionally guaranteed on a subordinated basis the payment of
principal, premium, if any, and interest on the Securities. The Holders of the
Securities will be entitled to the benefits of, be bound by, and be deemed to
have notice of, all of the provisions of the Indenture. A copy of the Indenture
is on file and may be inspected at the office of the Paying Agents appointed by
the Company. All terms used in this Security which are defined in the Indenture
shall have the meanings assigned to them in the Indenture.

     The Securities are issuable as bearer securities (the "Bearer
Securities"), with interest Coupons attached, in the denominations of U.S.
$1,000 and U.S. $10,000, and as registered securities (the "Registered
Securities"), without Coupons, in denominations of U.S. $1,000 and integral
multiples thereof, except as otherwise provided in or pursuant to the Indenture.
The Registered Securities, and transfers thereof, shall be registered as
provided in the Indenture. The holder of any Bearer Security or any Coupon
appertaining thereto and the registered holder of a Registered Security shall
(to the fullest extent permitted by applicable law) be treated at all times, by
all persons and for all purposes as the absolute owner of such Security or
Coupon, as the case may be, regardless of any notice of ownership, theft or loss
or of any writing thereon. Bearer Securities may be exchanged for Registered
Securities as set forth in the Indenture. Registered Securities may not be
exchanged for Bearer Securities.

     The Securities are general, unsecured obligations of the Company,
subordinated in right of payment to the prior payment in full of all existing
and future Senior Indebtedness of the Company to the extent set forth in Article
Seventeen of the Indenture. There are no restrictions herein on other
indebtedness or securities which may be incurred or issued by the Company or the
Guarantor.

     Additional Amounts shall be payable on the Securities as set forth in
the Indenture.

                                      -4-
<PAGE>
 
     If an Event of Default, as defined in the Indenture, shall occur and be
continuing, the principal of the Securities of this series may be declared due
and payable in the manner and with the effect provided in the Indenture.

     Subject to the terms of the Indenture, the Securities are convertible
at any time prior to Maturity at an initial Conversion Price of $35.65 per
share, subject to adjustment as provided in the Indenture. Accrued interest from
the immediately preceding Interest Payment Date until the Conversion Date will
be paid within five Business Days after the Conversion Date. In case this
Security, or a portion thereof, is called for redemption, or is delivered for
repayment, the conversion right in respect of this Security or a portion thereof
so called and delivered shall expire on the close of business on the fifth
Business Day preceding the Redemption Date or the second Business Day preceding
a repayment on the Repayment Date, as the case may be, unless the Company
defaults in making the payment due upon redemption or repayment, as the case may
be. To convert this Security, the Holder must surrender this Security, duly
endorsed or assigned to the Company, at any applicable Place of Conversion,
accompanied by a duly signed conversion notice. Bearer Securities surrendered
for conversion must be surrendered together with all Coupons appertaining
thereto that mature after the Conversion Date, except as otherwise provided in
the Indenture.

     The Securities are subject to redemption at any time on or after
January 15, 2001, as a whole or in part, at the option of the Company, at a
Redemption Price equal to 100% of the principal amount, together in the case of
any such redemption with accrued interest to the Redemption Date as provided in
the Indenture. Notice of redemption will be given to Holders of Securities, not
less than 20 nor more than 60 days prior to the Redemption Date, all as provided
in the Indenture. Subject to the terms of the Indenture, if as a result of a Tax
Law Change the Company has or will become obligated to pay to the Holder of any
Tax Affected Security Additional Amounts, and such obligation cannot be avoided
by the Company taking reasonable measures available to it, then the Company may,
at its option, redeem the Tax Affected Securities as a whole, but not in part,
upon not less than 20 nor more than 60 days' notice to the Holders prior to the
Redemption Date therefor, at a Redemption Price equal to 100% of the principal
amount plus interest accrued to the Redemption Date, and any Additional Amounts
then payable.

     Subject to the terms of the Indenture, the Securities are subject to
repayment at the option of the Holder thereof, in whole or in part, on the
Repayment Date, if the Common Stock (or other equity securities into which this
Security is then convertible) is neither listed for trading on a United States
national securities exchange, the Nasdaq National Market nor approved for
trading on an established automated over-the-counter trading market in the
United States. In such event, the Securities shall be repaid at a price equal to
the principal amount hereof, plus accrued interest and Additional Amounts, if
any. The Holders of Securities of this series desiring to be repaid must deliver
(1) this Security with the "Option to Elect Repayment" duly signed and
completed, or (2) such other documentation as may be provided by the Indenture,
to the Trustee at the Place of Payment not earlier than 60 days nor later than
30 days prior to the Repayment Date. Bearer 

                                      -5-
<PAGE>
 
Securities must be surrendered together with all Coupons appertaining thereto
that mature after the Repayment Date, except as otherwise provided in the
Indenture.

     The Place of Payment, place of registration of transfer and exchange
and the Place of Conversion for the Registered Securities and the Guarantees
endorsed thereon, shall be the Borough of Manhattan, The City of New York, and
the Corporate Trust Office of the Trustee shall be the Company's and the
Guarantor's Office or Agency in the Borough of Manhattan, The City of New York
for such purpose. The Places of Payment and Places of Conversion for the Bearer
Securities and the Guarantees endorsed thereon, shall be London, England and
Luxembourg, and the offices of the Trustee in London and Luxembourg shall be the
Offices or Agencies for such purpose and the offices of the Trustee in London
and Luxembourg shall be the Company's and the Guarantor's Paying Agent in London
and Luxembourg, respectively.

     The Trustee initially shall be the Security Registrar, one of the
Authenticating Agents, the Paying Agent and the Conversion Agent. The Trustee
presently has its Corporate Trust Office at Four Albany Street, 4th Floor, New
York, NY 10006, its Office in London at 1 Appold Street, Broadgate, London, EC2A
2HE, England, and its Office in Luxembourg at 14 Boulevard F.D. Roosevelt,
L-2450 Luxembourg. The Company and the Guarantor may subsequently appoint an
Office or Agency in addition to or other than the Borough of Manhattan, The City
of New York with respect to the Registered Securities and London, England and
Luxembourg with respect to the Bearer Securities.

     The Indenture permits, with certain exceptions as therein provided, the
amendment thereof and the modification of the rights and obligations of the
Company and the Guarantor and the rights of the Holders of the Securities under
the Indenture at any time by the Company, the Guarantor and the Trustee with the
consent of the Holders of not less than a majority of the aggregate principal
amount of all Securities issued under the Indenture at the time Outstanding and
affected thereby. The Indenture also contains provisions permitting the Holders
of not less than a majority of the aggregate principal amount of the Outstanding
Securities, on behalf of the Holders of all such Securities, to waive compliance
by the Company and the Guarantor with certain provisions of the Indenture.
Furthermore, provisions in the Indenture permit the Holders of not less than a
majority of the aggregate principal amount, in certain instances, of the
Outstanding Securities of any series to waive, on behalf of all of the Holders
of Securities of such series, certain past defaults under the Indenture and
their consequences. Any such consent or waiver by the Holder of this Security
shall be conclusive and binding upon such Holder and upon all future Holders of
this Security and other Securities issued upon the registration of transfer
hereof or in exchange herefor or in lieu hereof, whether or not notation of such
consent or waiver is made upon this Security.

     No reference herein to the Indenture and no provision of this Security
or of the Indenture shall alter or impair the obligation of the Company, which
is absolute and unconditional (except as to the specific subordination
provisions contained in Article Seventeen of the Indenture), to pay the
principal of, premium, if any, interest and Additional Amounts, if any, on this
Security at the times, places and rates, and in the coin or currency, herein
prescribed.

                                      -6-
<PAGE>
 
     No service charge shall be made for any registration of transfer or
exchange, but the Company may require payment of a sum sufficient to cover any
tax or other governmental charge payable in connection therewith.

     The Indenture and the Securities shall be governed by and construed in
accordance with the laws of the Commonwealth of Massachusetts applicable to
agreements made and to be performed entirely in such Commonwealth except that
the rights, protections, obligations, indemnities and immunities of the Trustee
under the Indenture and the Securities shall be governed by the laws of the
State of New York, without regard to the principles of conflicts of laws of
either state.

                                      -7-
<PAGE>
 
                            SCHEDULE OF ADJUSTMENTS

                                          Remaining           Notation
                Principal                 principal amount    made on
                amount                    following such      behalf of the
Date made       adjustment                adjustment          Trustee
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------      ------------------

- -------------------------------------------------------------------------------

                                      -8-
<PAGE>
 
                                    GUARANTEE

     For value received, Thermo Electron Corporation, a corporation
organized under the laws of the State of Delaware (herein called the
"Guarantor," which term includes any successor corporation under the Indenture
referred to in the Security upon which this Guarantee is endorsed), hereby
unconditionally guarantees to the Holder of the Security upon which this
Guarantee is endorsed and to the Trustee on behalf of the Trustee and such
Holder the due and punctual payment of the principal of, premium, if any, and
interest and Additional Amounts, if any, on such Security, any other amount due
and payable pursuant to the terms of the Indenture and the due and punctual
payment of the sinking fund or analogous payments referred to therein if any,
when and as the same shall become due and payable, whether at the Stated
Maturity, by declaration of acceleration, call for redemption, repayment at the
option of the Holder or otherwise, according to the terms thereof and of the
Indenture. In case of the failure of Thermo Instrument Systems Inc., a
corporation organized under the laws of Delaware (herein called the "Company,"
which term includes any successor corporation under such Indenture), punctually
to make any such payment of principal, premium, if any, or interest or
Additional Amounts, if any, the Guarantor hereby agrees to cause any such
payment to be made punctually when and as the same shall become due and payable,
whether at the Stated Maturity or by declaration of acceleration, call for
redemption, repayment at the option of the Holder or otherwise, and as if such
payment were made by the Company.

     The Guarantor hereby agrees that its obligations hereunder shall be as
if it were principal debtor and not merely surety, and shall be absolute and
unconditional (except as to the specific subordination provisions contained in
Article Eighteen of the Indenture), irrespective of, and shall be unaffected by,
any invalidity, subordination, irregularity or unenforceability of such Security
or such Indenture, any failure to enforce the provisions of such Security or
such Indenture, or any waiver, modification or indulgence granted to the Company
with respect thereto, by the Holder of such Security or the Trustee or any other
circumstance which may otherwise constitute a legal or equitable discharge of a
surety or guarantor. The Guarantor hereby waives the benefits of diligence,
presentment, demand of payment, filing of claims with a court in the event of
merger, insolvency or bankruptcy of the Company, any right to require a
proceeding first against the Company, protest or notice with respect to such
Security or the indebtedness evidenced thereby and all demands whatsoever, and
covenants that this Guarantee will not be discharged except by strict and
complete performance of the obligations contained in such Security and this
Guarantee. The Guarantor hereby agrees that, in the event of a default in
payment of principal of, premium, if any, and interest, and Additional Amounts,
if any, on such Security, or default in any sinking fund or analogous payment
referred to therein, legal proceedings may be instituted by the Trustee on
behalf of, or by, the Holder of such Security, on the terms and conditions set
forth in the Indenture, directly against the Guarantor to enforce this Guarantee
without first proceeding against the Company.

     The Guarantor shall be subrogated to all rights of the Holder of such
Security and the Trustee against the Company in respect of any amounts paid to
such Holder by the Guarantor on account of such Security pursuant to the
provisions of this Guarantee or the Indenture; provided, however, that the
                                               --------  -------
Guarantor shall not be entitled to enforce, or to receive any payments arising

                                      -9-
<PAGE>
 
out of or based upon, such right of subrogation until the principal of, premium,
if any, and interest and Additional Amounts, if any, on all Securities issued
under such Indenture shall have been paid in full.

     Claims under this Guarantee are, to the extent provided in the
Indenture, subject in right of payment to the prior payment in full of all
Senior Guarantor Indebtedness, and this Guarantee is issued subject to the
provisions of the Indenture with respect thereto. Each Holder of a Security upon
which this Guarantee is endorsed, by accepting the same, (a) agrees to and shall
be bound by such provisions, (b) authorizes and directs the Trustee on his
behalf to take such action as may be necessary or appropriate to effectuate the
subordination so provided and (c) appoints the Trustee his, her or its
attorney-in-fact for any and all such purposes.

     No reference herein to such Indenture and no provision of this
Guarantee or of such Indenture shall alter or impair the guarantee of the
Guarantor, which is absolute and unconditional (except as to the specific
subordination provisions contained in Article Eighteen of the Indenture), of the
due and punctual payment of principal, premium (if any), and interest and
Additional Amounts, if any, on the Security upon which this Guarantee is
endorsed.

     This Guarantee shall not be valid or obligatory for any purpose until
the certificate of authentication of the Security upon which this Guarantee is
endorsed shall have been manually executed by or on behalf of the Trustee under
such Indenture.

     All terms used in this Guarantee which are defined in such Indenture
shall have the meanings assigned to them in such Indenture.

     This Guarantee shall be deemed to be a contract made under the laws of
the Commonwealth of Massachusetts, and for all purposes shall be governed by and
construed in accordance with the laws of the Commonwealth of Massachusetts.

     IN WITNESS WHEREOF, the Guarantor has caused this Guarantee to be duly
executed under its corporate seal and dated the date on the face hereof.

                                             THERMO ELECTRON CORPORATION


Attest:______________________________        By: _____________________________

                                             Title: __________________________

                                      -10-
<PAGE>
 
         This is one of the Securities of the series designated therein referred
to in the within-mentioned Indenture.

Dated:  _______________________              BANKERS TRUST COMPANY,
                                             as Trustee



                                             By: ______________________________
                                                       Authorized Officer

                                      -11-
<PAGE>
 
                                 TRANSFER NOTICE


FOR VALUE RECEIVED, the undersigned Holder hereby sell(s), assign(s) and 
transfer(s) unto ______________________________________________________________
whose taxpayer identification number is _____________________ and whose address
including postal/zip code is _____________________________________ the within
Security and all rights thereunder, hereby irrevocably constituting and
appointing _____________________________ attorney-in-fact to transfer said
Security on the books of the Security Registrar with full power of substitution
in the premises.


Dated: __________________________      Name: ____________________________

                                       By: ______________________________

                                       Title: ___________________________

                                       NOTICE: The signature of the
                                       Holder to this assignment must
                                       correspond with the name as
                                       written upon the face of the
                                       within instrument in every
                                       particular, without enlargement
                                       or any change whatsoever.

                                       SIGNATURE GUARANTEED


                                       ____________________________________


                                      -12-
<PAGE>
 
                               CONVERSION NOTICE



     The undersigned Holder of this Security hereby irrevocably exercises
the option to convert this Security, or any portion of the principal amount
hereof (which is an integral multiple of U.S. $1,000 below designated), into
shares of Common Stock in accordance with the terms of the Indenture referred to
in this Security, and directs that such shares, together with a check in payment
for any fractional share and any Securities representing any unconverted
principal amount hereof, be delivered to and be registered in the name of the
undersigned unless a different name has been indicated below. If shares or
Securities are to be registered in the name of a Person other than the
undersigned, the undersigned will pay all transfer taxes payable with respect
thereto.


Dated: ___________________________          ___________________________________
                                                          Signature
                                            [MUST BE GUARANTEED IF STOCK
                                            OR SECURITIES ARE TO BE ISSUED
                                            IN A NAME OTHER THAN THE 
                                            REGISTERED HOLDER OF THE
                                            SECURITY]

____________________________________
               Name

____________________________________
             Address

____________________________________
Social Security or other Taxpayer 
Identification Number, if any

                                      -13-
<PAGE>
 
If shares or Registered Securities are     If only a portion of the Securities 
to be registered in the name of a Person   is to be converted, please indicate:
other than the Holder, please print
such Person's name and address:            1. Principal amount to be converted:

                                           U.S. $___________________

_______________________________            2. Principal amount and denomination
            Name                              of Registered Securities
                                              representing unconverted
                                              principal amount to be issued.
_______________________________
           Address
                                           Amount:  U.S.$_________________
_______________________________
Social Security or other Taxpayer          Denominations:
Identification Number, if any              U.S.$__________
                                           (any integral multiple of 
                                            U.S. $1,000)

_______________________________



                           OPTION TO ELECT REPAYMENT
                            UPON A REPAYMENT EVENT


To:  Thermo Instrument Systems Inc.

     The undersigned owner of this Security hereby acknowledges receipt of a
notice from Thermo Instrument Systems Inc.(the "Company") as to the occurrence
of a Repayment Event with respect to the Common Stock of the Company and
requests and instructs the Company to repay the entire principal amount of this
Security, or the portion thereof (which is $1,000 or an integral multiple
thereof) below designated, in accordance with the terms of the Indenture
referred to in this Security at the Repayment Price (or the relevant percentage
thereof), together with accrued interest to such date (except if the Repayment
Date shall be an Interest Payment Date), to the holder hereof.


Dated: ________________________


                                              _______________________________
                                              Signature*(s)

                                      -14-
<PAGE>
 
                                              Name: ___________________________
                                              Address:_________________________

                                                 ______________________________
                                              [* Signature Guarantee Required]

                                              Principal amount to be repaid
                                              (if less than all):

                                              $__________________

                                              NOTICE: If this Security is
                                              issued in registered form, the
                                              above signatures of the
                                              holder(s) hereof must
                                              correspond with the name as it
                                              appears in the Security in
                                              every particular without
                                              alteration or enlargement or
                                              any change whatever.


_______________________________
Social Security or Other
Taxpayer Identification Number

                                      -15-
<PAGE>
 
                                                                     EXHIBIT C
                                                                                
               FORM OF CONVERTIBLE SUBORDINATED BEARER SECURITY
                              [Face of Security]

ANY UNITED STATES PERSON WHO HOLDS THIS SECURITY WILL BE SUBJECT TO LIMITATIONS
UNDER THE UNITED STATES INCOME TAX LAWS, INCLUDING THE LIMITATIONS PROVIDED IN
SECTIONS 165(j) AND 1287(a) OF THE UNITED STATES INTERNAL REVENUE CODE.

                         THERMO INSTRUMENT SYSTEMS INC.
                    (INCORPORATED IN THE STATE OF DELAWARE)


                     4% CONVERTIBLE SUBORDINATED DEBENTURE
                             DUE JANUARY 15, 2005
                     GUARANTEED ON A SUBORDINATED BASIS BY
                          THERMO ELECTRON CORPORATION
                    (INCORPORATED IN THE STATE OF DELAWARE)

NO. ____________                                                   $____________

          Thermo Instrument Systems Inc., a Delaware corporation (herein
referred to as the "Company," which term includes any successor corporation
under the Indenture referred to on the reverse hereof), for value received,
hereby promises to pay to bearer upon presentation and surrender hereof the
principal sum of $_______ United States Dollars plus any premium, if any, on
January 15, 2005 (the "Stated Maturity") or, at the option of the Company, in
whole or in part at any time on or after January 15, 2001, upon notice as
described in the Indenture and to pay interest thereon from January 21, 1998 or
from the most recent Interest Payment Date to which interest has been paid or
duly provided for, semi-annually in arrears on January 15 and July 15 in each
year (each, an "Interest Payment Date"), commencing July 15, 1998, at the rate
of 4% per annum, and Additional Amounts, if any, until the principal hereof is
paid or duly provided for. The interest and Additional Amounts, if any, so
payable, and punctually paid or duly provided for, on any Interest Payment Date
will, as provided in such Indenture, be paid to the Holder surrendering the
appropriate Coupon appertaining hereto. Interest will be computed on the basis
of a 360-day year of twelve 30-day months.

          Such payments (including premium, if any) shall be made in United
States Dollars.  The Company shall maintain, subject to any laws or regulations
applicable thereto, an Office or Agency in a Place of Payment that is located
outside the United States where this Security and any Coupons appertaining
hereto, and Guarantees with respect hereto, may be presented and surrendered for
payment.  Subject to the right of the Company (limited as provided in the
Indenture) to change the location of any Office or Agency, the  Place of Payment
and Place of Conversion with respect to this Security shall be either at the
London office of Bankers Trust Company located at 1 Appold Street, Broadgate, 
London, EC2A 2HE, England, at Bankers Trust 

<PAGE>
 
Luxembourg, S.A. located at 14 Boulevard, F.D. Roosevelt, L-2450 Luxembourg or
at such other Offices or Agencies outside the United States as the Company may
designate. Such payments shall be made by United States Dollar check drawn on a
bank in the City of New York, or (at the option of the Company with the consent
of the Paying Agent) by transfer to a United States Dollar account maintained by
the Holder at a bank located outside the United States. Interest on this
Security shall be paid only at an Office or Agency located outside the United
States and, in the case of interest due on or before Maturity, only upon
presentation and surrender at such an Office or Agency of the applicable
interest Coupons hereto attached as they severally mature. No payment on this
Security or any Coupon will be made at the Corporate Trust Office of the Trustee
or any other Paying Agent maintained by the Company in the United States, nor
will any payment be made by transfer to an account in the United States, except
as may be permitted by United States tax laws and regulations in effect at the
time of such payment without detriment to the Company. Notwithstanding the
foregoing, payment of this Security and Coupons may be made at the Corporate
Trust Office of the Trustee in the City of New York if full payment at all
Paying Agents outside the United States is illegal or effectively precluded by
exchange controls or other similar restrictions.

          Reference is hereby made to the further provisions of this Security
set forth on the reverse hereof, which further provisions shall for all purposes
have the same effect as if set forth at this place.

          Unless the Certificate of Authentication hereon has been executed by
the Trustee by manual signature of one of its authorized signatories, this
Security shall not be entitled to any benefit under the indenture, or be valid
or obligatory for any purpose.

                                      -2-
<PAGE>
 
    IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed under its facsimile corporate seal.

Dated: January __, 1998                     THERMO INSTRUMENT SYSTEMS INC.
                                            
                                            By:_______________________
Attest:                                        Name
                                               Title
_______________________________
Secretary

[SEAL]

                         CERTIFICATE OF AUTHENTICATION

  This is one of the Securities of the series designated therein referred to in
the within-mentioned Indenture.

                              BANKERS TRUST COMPANY,
                              As Trustee

                                 BY:_____________________________
                                    Authorized Officer

                                      -3-
<PAGE>
 
                 (FORM OF FACE OF COUPON ON BEARER SECURITIES)

ANY UNITED STATES PERSON WHO HOLDS THIS SECURITY WILL BE SUBJECT TO LIMITATIONS
UNDER THE UNITED STATES INCOME TAX LAWS, INCLUDING THE LIMITATIONS PROVIDED IN
SECTIONS 165(j) AND 1287(a) OF THE UNITED STATES INTERNAL REVENUE CODE.

                         THERMO INSTRUMENT SYSTEMS INC.
                    (Incorporated in the State of Delaware)

                4% CONVERTIBLE SUBORDINATED DEBENTURE DUE 2005

                                              No:  _____________

                                              U.S.$____________

                                              Due:

          Unless the Security to which this Coupon appertains shall have been
called for redemption or presented for repayment prior to the due date hereof
and payment thereof duly provided for or shall have been converted, Thermo
Instrument Systems Inc. (herein called the "Company") shall, subject to and in
accordance with the terms and conditions of the Bearer Security and the
Indenture dated as of January 15, 1998 by the Company, as issuer, and Thermo
Electron Corporation, as guarantor, to Bankers Trust Company, as Trustee, pay to
the bearer, on the date set forth herein upon surrender hereof, the amount shown
hereon (together with any Additional Amounts in respect thereof which the
Company may be required to pay according to the terms of said Indenture) at the
offices of the Paying Agent set out on the reverse hereof or at such other
places outside the United States as the Company may determine from time to time,
by United States Dollar check drawn on a bank in the City of New York, or (at
the option of the Company with the consent of the Paying Agent) by transfer to a
United States Dollar account maintained by the bearer at a bank outside the
United States, being one-half year's interest then payable on said Security.

                                              THERMO INSTRUMENT SYSTEMS INC.


                                              By:___________________________
                                                 Name:
                                                 Title:
Attest:

__________________________

                                      -4-
<PAGE>
 
                              [Reverse of Coupon]


Bankers Trust Company                         Bankers Trust Luxembourg, S.A.
1 Appold Street                               14 Boulevard, F.D. Roosevelt
Broadgate, London EC2A 2HE                    L-2450 Luxembourg
England

                                      -5-
<PAGE>
 
                     (FORM OF REVERSE OF BEARER SECURITIES)

                         THERMO INSTRUMENT SYSTEMS INC.


          This Security is one of a duly authorized issue of securities of the
Company (herein called the "Securities"), issued and to be issued in one or more
series under an Indenture, dated as of January 15, 1998 (herein called the
"Indenture") by the Company, as issuer, and Thermo Electron Corporation, as
guarantor (herein called the "Guarantor," which term includes any successor
corporation under the Indenture), to Bankers Trust Company, as Trustee (herein
called the "Trustee," which term includes any successor trustee under the
Indenture with respect to the series of which this Security is a part), to which
Indenture and all indentures supplemental thereto reference is hereby made for a
statement of the respective rights, limitations of rights, duties and immunities
thereunder of the Company, the Guarantor, the Trustee and the Holders of the
Securities and any Coupons appertaining thereto, and of the terms upon which the
Securities are, and are to be, authenticated and delivered. This Security is one
of the duly authorized series of Securities designated on the face hereof and
the aggregate principal amount of the Securities to be issued under such series
is limited to $250,000,000 (except for Securities authenticated and delivered
upon transfer of, or in exchange for, or in lieu of other Securities). The
Guarantor has unconditionally guaranteed on a subordinated basis the payment of
principal, premium, if any, and interest on the Securities. The Holders of the
Securities will be entitled to the benefits of, be bound by, and be deemed to
have notice of, all of the provisions of the Indenture. A copy of the Indenture
is on file and may be inspected at the office of the Paying Agent appointed by
the Company. All terms used in this Security which are defined in the Indenture
shall have the meanings assigned to them in the Indenture.

          The Securities are issuable as bearer securities (the "Bearer
Securities"), with interest Coupons attached, in the denominations of U.S.
$1,000 AND U.S. $10,000, and as registered securities (the "Registered
Securities"), without Coupons, in denominations of U.S. $1,000 and integral
multiples thereof, except as otherwise provided in or pursuant to the Indenture.
The Registered Securities, and transfers thereof, shall be registered as
provided in the Indenture.  The holder of any Bearer Security or any Coupon
appertaining thereto and the registered holder of a Registered Security shall
(to the fullest extent permitted by applicable law) be treated at all times, by
all persons and for all purposes as the absolute owner of such Security or
Coupon, as the case may be, regardless of any notice of ownership, theft or loss
or of any writing thereon.  Bearer Securities may be exchanged for Registered
Securities as set forth in the Indenture.  Registered Securities may not be
exchanged for Bearer Securities.

          The Securities are general, unsecured obligations of the Company,
subordinated in right of payment to the prior payment in full of all existing
and future Senior Indebtedness of the Company to the extent set forth in Article
Seventeen of the Indenture.  There are no restrictions herein on other
indebtedness or securities which may be incurred or issued by the Company or the
Guarantor.

          The Securities have been approved for listing on the American Stock 
Exchange (the "AMEX"). Contracts for Securities traded on the AMEX must be 
settled in Registered Securities.

          Additional Amounts shall be payable on the Securities as set forth in
the Indenture.

                                      -6-
<PAGE>
 
          If an Event of Default, as defined in the indenture, shall occur and
be continuing, the principal of the Securities of this series may be declared
due and payable in the manner and with the effect provided in the Indenture.

          Subject to the terms of the Indenture, the Securities are convertible
at any time prior to Maturity at an initial Conversion Price of $35.65 per 
share, subject to adjustment as provided in the Indenture. Accrued interest from
the immediately preceding Interest Payment Date until the Conversion Date will
be paid within five Business Days after the Conversion Date. In case this
Security, or a portion thereof, is called for redemption, or is delivered for
repayment, the conversion right in respect of this Security or a portion thereof
so called and delivered shall expire on the close of business on the fifth
Business Day preceding the Redemption Date or the second Business Day preceding
a repayment on the Repayment Date, as the case may be, unless the Company
defaults in making the payment due upon redemption or repayment, as the case may
be. To convert this Security, the Holder must surrender this Security, duly
endorsed or assigned to the company, at any applicable place of conversion,
accompanied by a duly signed conversion notice. Bearer Securities surrendered
for conversion must be surrendered together with all Coupons appertaining
thereto that mature after the Conversion Date, except as otherwise provided in
the Indenture.

          The Securities are subject to redemption at any time on or after
January 15, 2001, as a whole or in part, at the option of the Company, at a
Redemption Price equal to 100% of the principal amount, together in the case of
any such redemption with accrued interest to the Redemption Date as provided in
the Indenture.  Notice of redemption will be given to Holders of Securities, not
less than 20 nor more than 60 days prior to the Redemption Date, all as provided
in the Indenture.  Subject to the terms of the indenture, if as a result of a
Tax Law Change the Company has or will become obligated to pay to the Holder of
any Tax Affected Security Additional Amounts, and such obligation cannot be
avoided by the Company taking reasonable measures available to it, then the
Company may, at its option, redeem the Tax Affected Securities as a whole, but
not in part, upon not less than 20 nor more than 60 days' notice to the Holders
prior to the Redemption Date therefor, at a Redemption Price equal to 100% of
the principal amount plus interest accrued to the Redemption Date, and any
Additional Amounts then payable.

          Subject to the terms of the Indenture, the Securities are subject to
repayment at the option of the Holder thereof, in whole or in part, on the
Repayment Date, if the Common Stock (or other equity securities into which this
Security is then convertible) is neither listed for trading on a United States
national securities exchange, the Nasdaq National Market nor approved for
trading on an established automated over-the-counter trading market in the
United States. In such event, the Securities shall be repaid at a price equal to
the principal amount hereof, plus accrued interest 

                                      -7-
<PAGE>
 
and Additional Amounts, if any. The Holders of Securities of this series
desiring to be repaid must deliver (1) this Security with the "Option to Elect
Repayment" duly signed and completed, or (2) such other documentation as may be
provided by the Indenture, to the Trustee at the Place of Payment not earlier
than 60 days nor later than 30 days prior to the Repayment Date. Bearer
Securities must be surrendered together with all Coupons appertaining thereto
that mature after the Repayment Date, except as otherwise provided in the
Indenture.

     In the event of redemption, exchange, repayment or conversion of this
Security in part only, a new Security or Securities for the unredeemed,
unexchanged, unrepaid or unconverted portion hereof shall be issued to the
Holder hereof upon the cancellation hereof as set forth in the Indenture.

     The Place of Payment, place of registration of transfer and exchange and
the Place of Conversion for the Registered Securities and the Guarantees
endorsed thereon, shall be the Borough of Manhattan, The City of New York, and
the Corporate Trust Office of the Trustee shall be the Company's and the
Guarantor's Office or Agency in the Borough of Manhattan, The City of New York
for such purpose.  The Places of Payment and Places of Conversion for the Bearer
Securities and the Guarantees endorsed thereon, shall be London, England and
Luxembourg, and the offices of the Trustee in London and Luxembourg shall be the
Offices or Agencies for such purpose and the offices of the Trustee in London
and Luxembourg shall be the Company's and the Guarantor's Paying Agent in London
and Luxembourg, respectively.

     The Trustee initially shall be the Security Registrar, one of the
Authenticating Agents, the Paying Agent and the Conversion Agent.  The Trustee
presently has its Corporate Trust Office at Four Albany Street, 4th floor, New
York, NY 10006, its Office in London at 1 Appold Street, Broadgate, London, EC2A
2HE, England and its Office in Luxembourg at 14 Boulevard, F.D. Roosevelt, L-
2450 Luxembourg. The Company and the Guarantor may subsequently appoint an
Office or Agency in addition to or other than the Borough of Manhattan, The City
of New York with respect to the Registered Securities and London, England and
Luxembourg with respect to the Bearer Securities.

     The Indenture permits, with certain exceptions as therein provided, the
amendment thereof and the modification of the rights and obligations of the
Company and the Guarantor and the rights of the Holders of the Securities under
the Indenture at any time by the Company, the Guarantor and the Trustee with the
consent of the Holders of not less than a majority of the aggregate principal
amount of all Securities issued under the Indenture at the time Outstanding and
affected thereby. The Indenture also contains provisions permitting the Holders
of not less than a majority of the aggregate principal amount of the Outstanding
Securities, on behalf of the Holders of all such Securities, to waive compliance
by the Company or the Guarantor with certain provisions of the Indenture.
Furthermore, provisions in the Indenture permit the Holders of not less than a
majority of the aggregate principal amount, in certain instances, of the
Outstanding Securities of any series to waive, on behalf of all of the Holders
of Securities of such series, certain past defaults under the Indenture and
their consequences. Any such consent or waiver by the Holder of this Security
shall be conclusive and binding upon such Holder and upon all future Holders of
this Security and other Securities issued upon the registration of transfer

                                      -8-
<PAGE>
 
hereof or in exchange herefor or in lieu hereof, whether or not notation of such
consent or waiver is made upon this Security.

     No reference herein to the indenture and no provision of this Security or
of the Indenture shall alter or impair the obligation of the Company, which is
absolute and unconditional (except as to the specific subordination provisions
contained in Article Seventeen of the Indenture), to pay the principal of,
premium, if any, interest and Additional Amounts, if any, on this Security at
the times, places and rates, and in the coin or currency, herein prescribed.

     No service charge shall be made for any registration of transfer or
exchange, but the Company may require payment of a sum sufficient to cover any
tax or other governmental charge payable in connection therewith.

     The Indenture and the Securities shall be governed by and construed in
accordance with the laws of the Commonwealth of Massachusetts applicable to
agreements made and to be performed entirely in such Commonwealth except that
the rights, protections, obligations, indemnities and immunities of the Trustee
under the Indenture and the Securities shall be governed by the laws of the
State of New York, without regard to the principles of conflicts of laws of
either state.

                                      -9-
<PAGE>
 
                                   GUARANTEE

     For value received, Thermo Electron Corporation, a corporation organized
under the laws of the State of Delaware (herein called the "Guarantor," which
                                                            ---------        
term includes any successor corporation under the Indenture referred to in the
Security upon which this Guarantee is endorsed), hereby unconditionally
guarantees to the Holder of the Security upon which this Guarantee is endorsed
and to the Trustee on behalf of the Trustee and such Holder the due and punctual
payment of the principal of, premium, if any, and interest and Additional
Amounts, if any, on such Security, any other amount due and payable pursuant to
the terms of the Indenture and the due and punctual payment of the sinking fund
or analogous payments referred to therein if any, when and as the same shall
become due and payable, whether at the Stated Maturity, by declaration of
acceleration, call for redemption, repayment at the option of the Holder or
otherwise, according to the terms thereof and of the Indenture.  In case of the
failure of Thermo Instrument Systems Inc., a corporation organized under the
laws of Delaware (herein called the "Company," which term includes any successor
                                     -------                                    
corporation under such Indenture), punctually to make any such payment of
principal, premium, if any, or interest or Additional Amounts, if any, the
Guarantor hereby agrees to cause any such payment to be made punctually when and
as the same shall become due and payable, whether at the Stated Maturity or by
declaration of acceleration, call for redemption, repayment at the option of the
Holder or otherwise, and as if such payment were made by the Company.

     The Guarantor hereby agrees that its obligations hereunder shall be as if
it were principal debtor and not merely surety, and shall be absolute and
unconditional (except as to the specific subordination provisions contained in
Article Eighteen of the Indenture), irrespective of, and shall be unaffected by,
any invalidity, subordination, irregularity or unenforceability of such Security
or such Indenture, any failure to enforce the provisions of such Security or
such Indenture, or any waiver, modification or indulgence granted to the Company
with respect thereto, by the Holder of such Security or the Trustee or any other
circumstance which may otherwise constitute a legal or equitable discharge of a
surety or guarantor.  The Guarantor hereby waives the benefits of diligence,
presentment, demand of payment, filing of claims with a court in the event of
merger, insolvency or bankruptcy of the Company, any right to require a
proceeding first against the Company, protest or notice with respect to such
Security or the indebtedness evidenced thereby and all demands whatsoever, and
covenants that this Guarantee will not be discharged except by strict and
complete performance of the obligations contained in such Security and this
Guarantee.  The Guarantor hereby agrees that, in the event of a default in
payment of principal of, premium, if any, and interest, and Additional Amounts,
if any, on such Security, or default in any sinking fund or analogous payment
referred to therein, legal proceedings may be instituted by the Trustee on
behalf of, or by, the Holder of such Security, on the terms and conditions set
forth in the Indenture, directly against the Guarantor to enforce this Guarantee
without first proceeding against the Company.

     The Guarantor shall be subrogated to all rights of the Holder of such
Security and the Trustee against the Company in respect of any amounts paid to
such Holder by the Guarantor on account of such Security pursuant to the
provisions of this Guarantee or the Indenture; provided, however, that the
                                               --------  -------          
Guarantor shall not be entitled to enforce, or to receive any payments arising

                                      -10-
<PAGE>
 
out of or based upon, such right of subrogation until the principal of, premium,
if any, and interest and Additional Amounts, if any, on all Securities issued
under such Indenture shall have been paid in full.

     Claims under this Guarantee are, to the extent provided in the Indenture,
subject in right of payment to the prior payment in full of all Senior Guarantor
Indebtedness, and this Guarantee is issued subject to the provisions of the
Indenture with respect thereto.  Each Holder of a Security upon which this
Guarantee is endorsed, by accepting the same, (a) agrees to and shall be bound
by such provisions, (b) authorizes and directs the Trustee on his behalf to take
such action as may be necessary or appropriate to effectuate the subordination
so provided and (c) appoints the Trustee his, her or its attorney-in-fact for
any and all such purposes.

     No reference herein to such Indenture and no provision of this Guarantee or
of such Indenture shall alter or impair the guarantee of the Guarantor, which is
absolute and unconditional (except as to the specific subordination provisions
contained in Article Eighteen of the Indenture), of the due and punctual payment
of principal, premium (if any), and interest and Additional Amounts, if any, on
the Security upon which this Guarantee is endorsed.

     This Guarantee shall not be valid or obligatory for any purpose until the
certificate of authentication of the Security upon which this Guarantee is
endorsed shall have been manually executed by or on behalf of the Trustee under
such Indenture.

     All terms used in this Guarantee which are defined in such Indenture shall
have the meanings assigned to them in such Indenture.

     This Guarantee shall be deemed to be a contract made under the laws of the
Commonwealth of Massachusetts, and for all purposes shall be governed by and
construed in accordance with the laws of the Commonwealth of Massachusetts.

     IN WITNESS WHEREOF, the Guarantor has caused this Guarantee to be duly
executed under its corporate seal and dated the date on the face hereof.

                                    THERMO ELECTRON CORPORATION


Attest:_______________________      By:________________________________


                                    Title: ____________________________

                                      -11-
<PAGE>
 
     This is one of the Securities of the series designated therein referred to
in the within-mentioned Indenture.

                                    BANKERS TRUST COMPANY,
                                    as Trustee



                                    By: ______________________________
                                        Authorized Officer

                                      -12-
<PAGE>
 
                               CONVERSION NOTICE


     The undersigned Holder of this Security hereby irrevocably exercises the
option to convert this Security, or any portion of the principal amount hereof
(which is an integral multiple of U.S. $1,000 below designated) into shares of
Common Stock in accordance with the terms of the Indenture referred to in this
Security and directs that such shares, together with a check in payment for any
fractional share and any Securities representing any unconverted principal
amount hereof, be delivered to the undersigned unless a different name has been
indicated below.  The address for payment of any such check must be outside the
United States.  If shares are to be registered in the name of a Person other
than the undersigned, the undersigned will pay all transfer taxes payable with
respect thereto.


Dated: __________________                        ______________________________
                                                 Signature

 
If shares are to be registered in the name of    HOLDER
and delivered to a Person other than the
Holder, please print such Person's name and      Please print name and address 
address:                                         of Holder 
 
 
 
_____________________________________          _________________________________
             Name                                         Name
 
_____________________________________          _________________________________
             Address                                      Address
 
_____________________________________          _________________________________
 
 
_____________________________________          _________________________________
 
 
_____________________________________          _________________________________
Social Security or other Taxpayer              Social Security or other Taxpayer
Identification Number, if any                  Identification Number, if any

                                      -13-
<PAGE>
 
 Name and address (outside the United    If only a portion of the Securities 
 States) to where any check referred     is to be converted, please indicate:
 to in the first paragraph of this 
 Conversion Notice should be mailed:     1.  Principal amount to be converted:  
                                             U.S.  $______________
______________________________________   2.  Principal amount and denomination
Name                                         of Bearer Securities representing 
                                             unconverted principal amount to 
                                             be issued:  
______________________________________       Amount:  U.S. $_________________
Address                                  Denominations:  U.S. $________________
                                         (any integral multiple of U.S. $1,000)
 

                                      -14-
<PAGE>
 
                           OPTION TO ELECT REPAYMENT
                             UPON A REPAYMENT EVENT


To:  Thermo Instrument Systems Inc.

     The undersigned owner of this Security hereby acknowledges receipt of a
notice from Thermo Instrument Systems Inc. (the "Company") as to the occurrence
of a Repayment Event with respect to the Common Stock of the Company and
requests and instructs the Company to repay the entire principal amount of this
Security, or the portion thereof (which is $1,000 or an integral multiple
thereof) below designated, in accordance with the terms of the Indenture
referred to in this Security at the Repayment Price (or the relevant percentage
thereof), together with accrued interest to such date (except if the Repayment
Date shall be an Interest Payment Date), to the holder hereof.


Dated: ________________________


                            ________________________________
                            Signature

                            Name: __________________________
                            Address:_________________________
                                    _________________________
                                Principal amount to be repaid
                            (if less than all):

                            $__________

 

_____________________________
Social Security or Other
Taxpayer Identification Number

                                      -15-
<PAGE>
 
                                                                     EXHIBIT D




         ANY UNITED STATES PERSON WHO HOLDS THIS SECURITY WILL BE SUBJECT TO
LIMITATIONS UNDER THE UNITED STATES INCOME TAX LAWS, INCLUDING THE LIMITATIONS
PROVIDED IN SECTION 165(j) AND 1287(a) OF THE UNITED STATES INTERNAL REVENUE
CODE.

         THIS SECURITY IS A TEMPORARY GLOBAL SECURITY, WITHOUT COUPONS OR
CONVERSION RIGHTS, EXCHANGEABLE FOR DEFINITIVE BEARER SECURITIES WITH INTEREST
COUPONS OR REGISTERED SECURITIES WITHOUT INTEREST COUPONS. THE RIGHTS ATTACHING
TO THIS GLOBAL SECURITY, AND THE CONDITIONS AND PROCEDURES GOVERNING ITS
EXCHANGE FOR DEFINITIVE SECURITIES, ARE AS SPECIFIED IN THE INDENTURE (AS
DEFINED HEREIN).

         NEITHER THE HOLDER NOR THE BENEFICIAL OWNERS OF THIS GLOBAL SECURITY
SHALL BE ENTITLED TO RECEIVE PAYMENT OF INTEREST OR ANY PAYMENTS HEREON EXCEPT
PURSUANT TO THE PROVISIONS HEREOF.

                        THERMO INSTRUMENT SYSTEMS INC.
                    (Incorporated in the State of Delaware)


                4% CONVERTIBLE SUBORDINATED DEBENTURE DUE 2005
                     GUARANTEED ON A SUBORDINATED BASIS BY
                          THERMO ELECTRON CORPORATION
                    (Incorporated in the State of Delaware)

                       TEMPORARY GLOBAL BEARER DEBENTURE

         Thermo Instrument Systems Inc., a Delaware corporation (herein referred
to as the "Company", which term includes any successor corporation under the
Indenture referred to below), for value received, hereby promises to pay to
bearer upon presentation and surrender of this global Security the principal sum
of $____________ United States Dollars plus any premium, if any, on January 15,
2005 and to pay interest thereon from January 21, 1998 or from the most recent
Interest Payment Date to which interest has been paid or duly provided for,
semi-annually in arrears on January 15 and July 15 in each year, commencing July
15, 1998, at the rate of 4% per annum, and Additional Amounts, if any, until
the principal hereof is paid or duly provided for; provided, however, that
interest, Additional Amounts, if any, and any other payments on this global
Security shall be payable only after the issuance of the definitive Securities
for which this global Security is exchangeable and, in the case of definitive
Securities in bearer form, only upon presentation and surrender (at an Office or
Agency located outside the United States, except as otherwise provided in the
Indenture referred to below) of the appropriate Coupons appertaining thereto.

         This global Security is one of a duly authorized issue of Securities of
the Company designated as specified in the title hereof, issued and to be issued
in one or more series under the
<PAGE>
 
Indenture, dated as of January 15, 1998 (the "Indenture") by the Company and
Thermo Electron Corporation, as guarantor, to Bankers Trust Company, as Trustee
(the "Trustee", which term includes any successor Trustee under the Indenture).
This global Security is a temporary security and is exchangeable in whole or
from time to time in part without charge upon request of the Holder hereof for
definitive Securities in bearer form, with interest Coupons attached, commencing
on the date 40 days after the later of (i) the first closing date relating to
the sale of the Securities or (ii) the date of the closing relating to the sale
of the Securities acquired pursuant to the exercise of the over-allotment option
granted by the Company to the Underwriters, upon certification, in the forms set
forth as Exhibits D and E of the Indenture for such purpose, that the beneficial
owner or owners of this global Security (or, if such exchange is only for a part
of this global Security, of such part) are not United States persons or other
persons who have purchased such Security for resale to United States persons.
Definitive Securities in bearer form to be delivered in exchange for any part of
this global Security shall be delivered only outside of the United States. This
global Security will be exchangeable for definitive Securities in registered
form at any time without the certification requirements set forth above;
provided that such exchange is permitted by the rules and procedures then in
effect of Cedel and Euroclear, and provided, further, that if and so long as
Securities in registered form are represented solely by a permanent global
Security in registered form, this global Security will only be exchangeable for
an interest in the permanent global Security in registered form as set forth in
the Indenture.

         Until exchanged in full for definitive Securities, this global Security
shall in all respects be entitled to the same benefits under, and subject to the
same terms and conditions of, the Indenture as definitive Securities
authenticated and delivered thereunder, except that neither the Holder hereof
nor the beneficial owners of this global Security shall be entitled to receive
payment of interest or any other payments hereon, except as provided above, or
to convert this global Security into shares of Common Stock of the Company or
any other security, cash or other property.

         THIS GLOBAL SECURITY SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE
WITH THE LAWS OF THE COMMONWEALTH OF MASSACHUSETTS, UNITED STATES OF AMERICA,
EXCEPT THAT THE RIGHTS, PROTECTIONS, OBLIGATIONS, INDEMNITIES, AND IMMUNITIES OF
THE TRUSTEE UNDER THIS GLOBAL SECURITY AND THE INDENTURE SHALL BE GOVERNED BY
THE LAWS OF THE STATE OF NEW YORK, WITHOUT REGARD TO THE PRINCIPLES OF CONFLICTS
OF LAWS OF EITHER STATE.

         All terms used in this global Security which are defined in the
Indenture shall have the meanings assigned to them in the Indenture.

         Unless the certificate of authentication hereon has been manually
executed by an authorized signatory of the Trustee, this global Security shall
not be entitled to any benefit under the Indenture or valid or obligatory for
any purpose.

                                      -2-
<PAGE>
 
         IN WITNESS WHEREOF, the Company has caused this global Security to be
duly executed under its facsimile corporate seal.

Dated: January __, 1998
                                    THERMO INSTRUMENT SYSTEMS INC.
              

                                    By:
                                       -----------------------------------------
                                      Name:
                                      Title:
Attest:

- --------------------------
Secretary
[SEAL]

                                      -3-
<PAGE>
 
                         CERTIFICATE OF AUTHENTICATION

         This is one of the Securities of the series designated therein referred
to in the within-mentioned Indenture.

                                                 BANKERS TRUST COMPANY,
                                                   as Trustee


                                                 By:
                                                    -------------------------
                                                    Authorized Officer

                                      -4-
<PAGE>
 
                                   GUARANTEE

         For value received, Thermo Electron Corporation, a corporation
organized under the laws of the State of Delaware (herein called the
"Guarantor," which term includes any successor corporation under this Indenture
referred to in the Security upon which this Guarantee is endorsed), hereby
unconditionally guarantees to the Holder of the Security upon which this
Guarantee is endorsed and to the Trustee on behalf of the Trustee and such
Holder the due and punctual payment of the principal of, premium, if any, and
interest and Additional Amounts, if any, on such Security, any other amount due
and payable pursuant to the terms of the Indenture and the due and punctual
payment of the sinking fund or analogous payments referred to therein if any,
when and as the same shall become due and payable, whether at the Stated
Maturity, by declaration of acceleration, call for redemption, repayment at the
option of the Holder or otherwise, according to the terms thereof and of the
Indenture. In case of the failure of Thermo Instrument Systems Inc., a
corporation organized under the laws of Delaware (herein called the "Company,"
which term includes any successor corporation under such Indenture), punctually
to make any such payment of principal, premium, if any, or interest or
Additional Amounts, if any, the Guarantor hereby agrees to cause any such
payment to be made punctually when and as the same shall become due and payable,
whether at the Stated Maturity or by declaration of acceleration, call for
redemption, repayment at the option of the Holder or otherwise, and as if such
payment were made by the Company.

         The Guarantor hereby agrees that its obligations hereunder shall be as
if it were principal debtor and not merely surety, and shall be absolute and
unconditional (except as to the specific subordination provisions contained in
Article Eighteen of the Indenture), irrespective of, and shall be unaffected by,
any invalidity, subordination, irregularity or unenforceability of such Security
or such Indenture, any failure to enforce the provisions of such Security or
such Indenture, or any waiver, modification or indulgence granted to the Company
with respect thereto, by the Holder of such Security or the Trustee or any other
circumstance which may otherwise constitute a legal or equitable discharge of a
surety or guarantor. The Guarantor hereby waives the benefits of diligence,
presentment, demand of payment, filing of claims with a court in the event of
merger, insolvency or bankruptcy of the Company, any right to require a
proceeding first against the Company, protest or notice with respect to such
Security or the indebtedness evidenced thereby and all demands whatsoever, and
covenants that this Guarantee will not be discharged except by strict and
complete performance of the obligations contained in such Security and this
Guarantee. The Guarantor hereby agrees that, in the event of a default in
payment of principal of, premium, if any, and interest, and Additional Amounts,
if any, on such Security, or default in any sinking fund or analogous payment
referred to therein, legal proceedings may be instituted by the Trustee on
behalf of, or by, the Holder of such Security, on the terms and conditions set
forth in the Indenture, directly against the Guarantor to enforce this Guarantee
without first proceeding against the Company.

         The Guarantor shall be subrogated to all rights of the Holder of such
Security and the Trustee against the Company in respect of any amounts paid to
such Holder by the Guarantor on account of such Security pursuant to the
provisions of this Guarantee or the Indenture; provided, however, that the
                                               --------  -------
Guarantor shall not be entitled to enforce, or to receive any payments arising

                                      -5-
<PAGE>
 
out of or based upon, such right of subrogation until the principal of, premium,
if any, and interest and Additional Amounts, if any, on all Securities issued
under such Indenture shall have been paid in full.

         Claims under this Guarantee are, to the extent provided in the
Indenture, subject in right of payment to the prior payment in full of all
Senior Guarantor Indebtedness, and this Guarantee is issued subject to the
provisions of the Indenture with respect thereto. Each Holder of a Security upon
which this Guarantee is endorsed, by accepting the same, (a) agrees to and shall
be bound by such provisions, (b) authorizes and directs the Trustee on his
behalf to take such action as may be necessary or appropriate to effectuate the
subordination so provided and (c) appoints the Trustee his, her or its
attorney-in-fact for any and all such purposes.

         No reference herein to such Indenture and no provision of this
Guarantee or of such Indenture shall alter or impair the guarantee of the
Guarantor, which is absolute and unconditional (except as to the specific
subordination provisions contained in Article Eighteen of the Indenture), of the
due and punctual payment of principal, premium (if any), and interest and
Additional Amounts, if any, on the Security upon which this Guarantee is
endorsed.

         This Guarantee shall not be valid or obligatory for any purpose until
the certificate of authentication of the Security upon which this Guarantee is
endorsed shall have been manually executed by or on behalf of the Trustee under
such Indenture.

         All terms used in this Guarantee which are defined in such Indenture
shall have the meanings assigned to them in such Indenture.

         This Guarantee shall be deemed to be a contract made under the laws of
the Commonwealth of Massachusetts, and for all purposes shall be governed by and
construed in accordance with the laws of the Commonwealth of Massachusetts.

         IN WITNESS WHEREOF, the Guarantor has caused this Guarantee to be duly
executed under its corporate seal and dated the date on the face hereof.

                                            THERMO ELECTRON CORPORATION


Attest:______________________________       By: ________________________________

                                            Title: _____________________________

                                      -6-

<PAGE>
 
                                                                     EXHIBIT 4.3



                    (FORM OF FACE OF REGISTERED SECURITIES)

                        THERMO INSTRUMENT SYSTEMS INC.
                    (Incorporated in the State of Delaware)


                     4% CONVERTIBLE SUBORDINATED DEBENTURE
                             DUE JANUARY 15, 2005
                     GUARANTEED ON A SUBORDINATED BASIS BY
                          THERMO ELECTRON CORPORATION
                    (Incorporated in the State of Delaware)

No. R-
      __________

Cusip: 883559AE6
      __________
 
         Thermo Instrument Systems Inc., a Delaware corporation (herein referred
to as the "Company," which term includes any successor corporation under the
Indenture referred to on the reverse hereof), for value received, hereby
promises to pay to ____________________ or registered assigns the principal sum
of _______ Dollars plus any premium, if any, on January 15, 2005 (the "Stated
Maturity") upon the presentation and surrender hereof or, at the option of the
Company, in whole or in part at any time on or after January 15, 2001, upon
notice as described in the Indenture and to pay interest thereon from January
21, 1998 or from the most recent Interest Payment Date to which interest has
been paid or duly provided for, semi-annually in arrears on January 15 and July
15 in each year (each, an "Interest Payment Date"), commencing July 15, 1998, at
the rate of 4% per annum, and Additional Amounts, if any, until the principal
hereof is paid or duly provided for. The interest and Additional Amounts, if
any, so payable, and punctually paid or duly provided for, on any Interest
Payment Date will, as provided in such Indenture, be paid to the Holder in whose
name this Security (or one or more Predecessor Securities) is registered at the
close of business on the Regular Record Date for such interest, which shall be
the January 1 or July 1 (whether or not a Business Day), as the case may be,
next preceding such Interest Payment Date at the Office or Agency of the Company
maintained for such purpose; provided, however, that such interest may be paid,
at the Company's option, by mailing a check to such Holder at its registered
address or by transfer of funds to an account maintained by such Holder within
the United States. Any such interest not so punctually paid or duly provided for
shall forthwith cease to be payable to the Holder on such Regular Record Date,
and may be paid to the Holder in whose name this Security (or one or more
Predecessor Securities) is registered at the close of business on a Special
Record Date for the payment of such Defaulted Interest to be fixed by the
Trustee, notice whereof shall be given to Holders of Securities of this series
not less than 10 days prior to such Special Record Date, or may be paid at any
time in any other lawful manner not inconsistent with the requirements of any
securities exchange on which the Securities of this series may be listed, and
upon such notice as may be required by such exchange, all as more fully provided
in the Indenture. Interest will be computed on the basis of a 360-day year of
twelve 30-day months. All payments hereunder shall be made in United States
Dollars.
<PAGE>
 
         Reference is hereby made to the further provisions of this Security set
forth on the reverse hereof, which further provisions shall for all purposes
have the same effect as if set forth at this place.

         Unless the Certificate of Authentication hereon has been executed by
the Trustee by manual signature of one of its authorized signatories, this
Security shall not be entitled to any benefit under the Indenture, or be valid
or obligatory for any purpose.

                                      -2-
<PAGE>
 
         IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed under its facsimile corporate seal.

Dated:  January __, 1998                      THERMO INSTRUMENT SYSTEMS
                                              INC.

                                              By:_______________________
Attest:                                          [Name]
                                                 [Title]
_____________________________
Secretary

[SEAL]




                         CERTIFICATE OF AUTHENTICATION

         This is one of the Securities of the series designated therein referred
to in the within-mentioned Indenture.

                                              BANKERS TRUST COMPANY,
                                              as Trustee


                                              By:
                                                 ____________________________
                                                 Authorized Officer

                                      -3-
<PAGE>
 
                  (FORM OF REVERSE OF REGISTERED SECURITIES)

                        THERMO INSTRUMENT SYSTEMS INC.

This Security is one of a duly authorized issue of securities of the Company
(herein called the "Securities"), issued and to be issued in one or more series
under an Indenture, dated as of January 15, 1998 (herein called the "Indenture")
by the Company, as issuer, and Thermo Electron Corporation, as guarantor (herein
called the "Guarantor," which term includes any successor corporation under the
Indenture), to Bankers Trust Company, as Trustee (herein called the "Trustee,"
which term includes any successor trustee under the Indenture with respect to
the series of which this Security is a part), to which Indenture and all
indentures supplemental thereto reference is hereby made for a statement of the
respective rights, limitations of rights, duties and immunities thereunder of
the Company, the Guarantor, the Trustee and the Holders of the Securities and
any Coupons appertaining thereto, and of the terms upon which the Securities
are, and are to be, authenticated and delivered. This Security is one of the
duly authorized series of Securities designated on the face hereof and the
aggregate principal amount of the Securities to be issued under such series is
limited to $250,000,000 (except for Securities authenticated and delivered upon
transfer of, or in exchange for, or in lieu of other Securities). The Guarantor
has unconditionally guaranteed on a subordinated basis the payment of principal,
premium, if any, and interest on the Securities. The Holders of the Securities
will be entitled to the benefits of, be bound by, and be deemed to have notice
of, all of the provisions of the Indenture. A copy of the Indenture is on file
and may be inspected at the office of the Paying Agents appointed by the
Company. All terms used in this Security which are defined in the Indenture
shall have the meanings assigned to them in the Indenture.

         The Securities are issuable as bearer securities (the "Bearer
Securities"), with interest Coupons attached, in the denominations of U.S.
$1,000 and U.S. $10,000, and as registered securities (the "Registered
Securities"), without Coupons, in denominations of U.S. $1,000 and integral
multiples thereof, except as otherwise provided in or pursuant to the Indenture.
The Registered Securities, and transfers thereof, shall be registered as
provided in the Indenture. The holder of any Bearer Security or any Coupon
appertaining thereto and the registered holder of a Registered Security shall
(to the fullest extent permitted by applicable law) be treated at all times, by
all persons and for all purposes as the absolute owner of such Security or
Coupon, as the case may be, regardless of any notice of ownership, theft or loss
or of any writing thereon. Bearer Securities may be exchanged for Registered
Securities as set forth in the Indenture. Registered Securities may not be
exchanged for Bearer Securities.

         The Securities are general, unsecured obligations of the Company,
subordinated in right of payment to the prior payment in full of all existing
and future Senior Indebtedness of the Company to the extent set forth in Article
Seventeen of the Indenture. There are no restrictions herein on other
indebtedness or securities which may be incurred or issued by the Company or the
Guarantor.

         Additional Amounts shall be payable on the Securities as set forth in
the Indenture.

                                      -4-
<PAGE>
 
         If an Event of Default, as defined in the Indenture, shall occur and be
continuing, the principal of the Securities of this series may be declared due
and payable in the manner and with the effect provided in the Indenture.

         Subject to the terms of the Indenture, the Securities are convertible
at any time prior to Maturity at an initial Conversion Price of $35.65 per
share, subject to adjustment as provided in the Indenture. Accrued interest from
the immediately preceding Interest Payment Date until the Conversion Date will
be paid within five Business Days after the Conversion Date. In case this
Security, or a portion thereof, is called for redemption, or is delivered for
repayment, the conversion right in respect of this Security or a portion thereof
so called and delivered shall expire on the close of business on the fifth
Business Day preceding the Redemption Date or the second Business Day preceding
a repayment on the Repayment Date, as the case may be, unless the Company
defaults in making the payment due upon redemption or repayment, as the case may
be. To convert this Security, the Holder must surrender this Security, duly
endorsed or assigned to the Company, at any applicable Place of Conversion,
accompanied by a duly signed conversion notice. Bearer Securities surrendered
for conversion must be surrendered together with all Coupons appertaining
thereto that mature after the Conversion Date, except as otherwise provided in
the Indenture.

         The Securities are subject to redemption at any time on or after
January 15, 2001, as a whole or in part, at the option of the Company, at a
Redemption Price equal to 100% of the principal amount, together in the case of
any such redemption with accrued interest to the Redemption Date as provided in
the Indenture. Notice of redemption will be given to Holders of Securities, not
less than 20 nor more than 60 days prior to the Redemption Date, all as provided
in the Indenture. Subject to the terms of the Indenture, if as a result of a Tax
Law Change the Company has or will become obligated to pay to the Holder of any
Tax Affected Security Additional Amounts, and such obligation cannot be avoided
by the Company taking reasonable measures available to it, then the Company may,
at its option, redeem the Tax Affected Securities as a whole, but not in part,
upon not less than 20 nor more than 60 days' notice to the Holders prior to the
Redemption Date therefor, at a Redemption Price equal to 100% of the principal
amount plus interest accrued to the Redemption Date, and any Additional Amounts
then payable.

         Subject to the terms of the Indenture, the Securities are subject to
repayment at the option of the Holder thereof, in whole or in part, on the
Repayment Date, if the Common Stock (or other equity securities into which this
Security is then convertible) is neither listed for trading on a United States
national securities exchange, the Nasdaq National Market nor approved for
trading on an established automated over-the-counter trading market in the
United States. In such event, the Securities shall be repaid at a price equal to
the principal amount hereof, plus accrued interest and Additional Amounts, if
any. The Holders of Securities of this series desiring to be repaid must deliver
(1) this Security with the "Option to Elect Repayment" duly signed and
completed, or (2) such other documentation as may be provided by the Indenture,
to the Trustee at the Place of Payment not earlier than 60 days nor later than
30 days prior to the Repayment Date. Bearer Securities must be surrendered
together with all Coupons appertaining thereto that mature after the Repayment
Date, except as otherwise provided in the Indenture.

                                      -5-
<PAGE>
 
         In the event of redemption, exchange, repayment or conversion of this
Security in part only, a new Security or Securities for the unredeemed,
unexchanged, unrepaid or unconverted portion hereof shall be issued in the name
of the Holder hereof upon the cancellation hereof as set forth in the Indenture.

         The Place of Payment, place of registration of transfer and exchange
and the Place of Conversion for the Registered Securities and the Guarantees
endorsed thereon, shall be the Borough of Manhattan, The City of New York, and
the Corporate Trust Office of the Trustee shall be the Company's and the
Guarantor's Office or Agency in the Borough of Manhattan, The City of New York
for such purpose. The Places of Payment and Places of Conversion for the Bearer
Securities and the Guarantees endorsed thereon, shall be London, England and
Luxembourg, and the offices of the Trustee in London and Luxembourg shall be the
Offices or Agencies for such purpose and the offices of the Trustee in London
and Luxembourg shall be the Company's and the Guarantor's Paying Agent in London
and Luxembourg, respectively.

         The Trustee initially shall be the Security Registrar, one of the
Authenticating Agents, the Paying Agent and the Conversion Agent. The Trustee
presently has its Corporate Trust Office at Four Albany Street, 4th Floor, New
York, NY 10006, its Office in London at 1 Appold Street, Broadgate, London, EC2A
2HE, England, and its Office in Luxembourg at 14 Boulevard F.D. Roosevelt,
L-2450 Luxembourg. The Company and the Guarantor may subsequently appoint an
Office or Agency in addition to or other than the Borough of Manhattan, The City
of New York with respect to the Registered Securities and London, England and
Luxembourg with respect to the Bearer Securities.

         The Indenture permits, with certain exceptions as therein provided, the
amendment thereof and the modification of the rights and obligations of the
Company and the Guarantor and the rights of the Holders of the Securities under
the Indenture at any time by the Company, the Guarantor and the Trustee with the
consent of the Holders of not less than a majority of the aggregate principal
amount of all Securities issued under the Indenture at the time Outstanding and
affected thereby. The Indenture also contains provisions permitting the Holders
of not less than a majority of the aggregate principal amount of the Outstanding
Securities, on behalf of the Holders of all such Securities, to waive compliance
by the Company and the Guarantor with certain provisions of the Indenture.
Furthermore, provisions in the Indenture permit the Holders of not less than a
majority of the aggregate principal amount, in certain instances, of the
Outstanding Securities of any series to waive, on behalf of all of the Holders
of Securities of such series, certain past defaults under the Indenture and
their consequences. Any such consent or waiver by the Holder of this Security
shall be conclusive and binding upon such Holder and upon all future Holders of
this Security and other Securities issued upon the registration of transfer
hereof or in exchange herefor or in lieu hereof, whether or not notation of such
consent or waiver is made upon this Security.

         No reference herein to the Indenture and no provision of this Security
or of the Indenture shall alter or impair the obligation of the Company, which
is absolute and unconditional (except as to the specific subordination
provisions contained in Article Seventeen of the Indenture), to

                                      -6-
<PAGE>
 
pay the principal of, premium, if any, interest and Additional Amounts, if any,
on this Security at the times, places and rates, and in the coin or currency,
herein prescribed.

         No service charge shall be made for any registration of transfer or
exchange, but the Company may require payment of a sum sufficient to cover any
tax or other governmental charge payable in connection therewith.

         The Indenture and the Securities shall be governed by and construed in
accordance with the laws of the Commonwealth of Massachusetts applicable to
agreements made and to be performed entirely in such Commonwealth except that
the rights, protections, obligations, indemnities and immunities of the Trustee
under the Indenture and the Securities shall be governed by the laws of the
State of New York, without regard to the principles of conflicts of laws of
either state.

                                      -7-
<PAGE>
 
                                   GUARANTEE

         For value received, Thermo Electron Corporation, a corporation
organized under the laws of the State of Delaware (herein called the
"Guarantor," which term includes any successor corporation under the Indenture
referred to in the Security upon which this Guarantee is endorsed), hereby
unconditionally guarantees to the Holder of the Security upon which this
Guarantee is endorsed and to the Trustee on behalf of the Trustee and such
Holder the due and punctual payment of the principal of, premium, if any, and
interest and Additional Amounts, if any, on such Security, any other amount due
and payable pursuant to the terms of the Indenture and the due and punctual
payment of the sinking fund or analogous payments referred to therein if any,
when and as the same shall become due and payable, whether at the Stated
Maturity, by declaration of acceleration, call for redemption, repayment at the
option of the Holder or otherwise, according to the terms thereof and of the
Indenture. In case of the failure of Thermo Instrument Systems Inc., a
corporation organized under the laws of Delaware (herein called the "Company,"
which term includes any successor corporation under such Indenture), punctually
to make any such payment of principal, premium, if any, or interest or
Additional Amounts, if any, the Guarantor hereby agrees to cause any such
payment to be made punctually when and as the same shall become due and payable,
whether at the Stated Maturity or by declaration of acceleration, call for
redemption, repayment at the option of the Holder or otherwise, and as if such
payment were made by the Company.

         The Guarantor hereby agrees that its obligations hereunder shall be as
if it were principal debtor and not merely surety, and shall be absolute and
unconditional (except as to the specific subordination provisions contained in
Article Eighteen of the Indenture), irrespective of, and shall be unaffected by,
any invalidity, subordination, irregularity or unenforceability of such Security
or such Indenture, any failure to enforce the provisions of such Security or
such Indenture, or any waiver, modification or indulgence granted to the Company
with respect thereto, by the Holder of such Security or the Trustee or any other
circumstance which may otherwise constitute a legal or equitable discharge of a
surety or guarantor. The Guarantor hereby waives the benefits of diligence,
presentment, demand of payment, filing of claims with a court in the event of
merger, insolvency or bankruptcy of the Company, any right to require a
proceeding first against the Company, protest or notice with respect to such
Security or the indebtedness evidenced thereby and all demands whatsoever, and
covenants that this Guarantee will not be discharged except by strict and
complete performance of the obligations contained in such Security and this
Guarantee. The Guarantor hereby agrees that, in the event of a default in
payment of principal of, premium, if any, and interest, and Additional Amounts,
if any, on such Security, or default in any sinking fund or analogous payment
referred to therein, legal proceedings may be instituted by the Trustee on
behalf of, or by, the Holder of such Security, on the terms and conditions set
forth in the Indenture, directly against the Guarantor to enforce this Guarantee
without first proceeding against the Company.

         The Guarantor shall be subrogated to all rights of the Holder of such
Security and the Trustee against the Company in respect of any amounts paid to
such Holder by the Guarantor on account of such Security pursuant to the
provisions of this Guarantee or the Indenture; provided, however, that the
                                               --------  -------  
Guarantor shall not be entitled to enforce, or to receive any payments arising

                                      -8-
<PAGE>
 
out of or based upon, such right of subrogation until the principal of, premium,
if any, and interest and Additional Amounts, if any, on all Securities issued
under such Indenture shall have been paid in full.

         Claims under this Guarantee are, to the extent provided in the
Indenture, subject in right of payment to the prior payment in full of all
Senior Guarantor Indebtedness, and this Guarantee is issued subject to the
provisions of the Indenture with respect thereto. Each Holder of a Security upon
which this Guarantee is endorsed, by accepting the same, (a) agrees to and shall
be bound by such provisions, (b) authorizes and directs the Trustee on his
behalf to take such action as may be necessary or appropriate to effectuate the
subordination so provided and (c) appoints the Trustee his, her or its
attorney-in-fact for any and all such purposes.

         No reference herein to such Indenture and no provision of this
Guarantee or of such Indenture shall alter or impair the guarantee of the
Guarantor, which is absolute and unconditional (except as to the specific
subordination provisions contained in Article Eighteen of the Indenture), of the
due and punctual payment of principal, premium (if any), and interest and
Additional Amounts, if any, on the Security upon which this Guarantee is
endorsed.

         This Guarantee shall not be valid or obligatory for any purpose until
the certificate of authentication of the Security upon which this Guarantee is
endorsed shall have been manually executed by or on behalf of the Trustee under
such Indenture.

         All terms used in this Guarantee which are defined in such Indenture
shall have the meanings assigned to them in such Indenture.

         This Guarantee shall be deemed to be a contract made under the laws of
the Commonwealth of Massachusetts, and for all purposes shall be governed by and
construed in accordance with the laws of the Commonwealth of Massachusetts.

         IN WITNESS WHEREOF, the Guarantor has caused this Guarantee to be duly
executed under its corporate seal and dated the date on the face hereof.

                                            THERMO ELECTRON CORPORATION


Attest:______________________________       By: ________________________________

                                            Title: _____________________________

                                      -9-
<PAGE>
 
         This is one of the Securities of the series designated therein referred
to in the within-mentioned Indenture.

Dated:  _______________________                   BANKERS TRUST COMPANY,
                                                  as Trustee



                                                  By: __________________________
                                                      Authorized Officer

                                      -10-
<PAGE>
 
                                TRANSFER NOTICE


FOR VALUE RECEIVED, the undersigned Holder hereby sell(s), assign(s) and
transfer(s) unto______________________________________________________________
______________________________________________________________________________
whose taxpayer identification number is _____________________ and whose address
including postal/zip code is _____________________________________ the within
Security and all rights thereunder, hereby irrevocably constituting and
appointing _____________________________ attorney-in-fact to transfer said
Security on the books of the Security Registrar with full power of substitution
in the premises.


Dated:___________________                            Name:______________________

                                                     By:________________________

                                                     Title:_____________________

                                                     NOTICE: The signature of
                                                     the Holder to this
                                                     assignment must correspond
                                                     with the name as written
                                                     upon the face of the within
                                                     instrument in every
                                                     particular, without
                                                     enlargement or any change
                                                     whatsoever.

                                                     SIGNATURE GUARANTEED

                                                     ___________________________

                                      -11-
<PAGE>
 
                               CONVERSION NOTICE



         The undersigned Holder of this Security hereby irrevocably exercises
the option to convert this Security, or any portion of the principal amount
hereof (which is an integral multiple of U.S. $1,000 below designated), into
shares of Common Stock in accordance with the terms of the Indenture referred to
in this Security, and directs that such shares, together with a check in payment
for any fractional share and any Securities representing any unconverted
principal amount hereof, be delivered to and be registered in the name of the
undersigned unless a different name has been indicated below. If shares or
Securities are to be registered in the name of a Person other than the
undersigned, the undersigned will pay all transfer taxes payable with respect
thereto.


Dated:------------------------------         ---------------------------------
                                                         Signature
                                             [MUST BE GUARANTEED IF STOCK
                                             OR SECURITIES ARE TO BE ISSUED IN
                                             A NAME OTHER THAN THE  REGISTERED
                                             HOLDER OF THE SECURITY]


- ------------------------------------
               Name

- ------------------------------------
               Address

- ------------------------------------
Social Security or other Taxpayer
Identification Number, if any

                                      -12-
<PAGE>
 
If shares or Registered Securities are to    If only a portion of the
be registered in the name of a Person        Securities is to be converted,
other than the Holder, print such            please please indicate:   
Person's name and address:    


                                             1. Principal amount to be
                                                converted:

                                             U.S. $___________________

_______________________________              2.  Principal amount and
           Name                                  denomination of Registered
                                                 Securities representing
                                                 unconverted principal amount
                                                 to be issued.
_______________________________
           Address
                                             Amount:  U.S.$_________________
_______________________________
Social Security or other Taxpayer            Denominations:
Identification Number, if any                U.S.$__________
                                             (any integral multiple of U.S.
                                             $1,000)

_______________________________

                                      -13-
<PAGE>
 
                           OPTION TO ELECT REPAYMENT
                            UPON A REPAYMENT EVENT


To:      Thermo Instrument Systems Inc.

         The undersigned owner of this Security hereby acknowledges receipt of a
notice from Thermo Instrument Systems Inc.(the "Company") as to the occurrence
of a Repayment Event with respect to the Common Stock of the Company and
requests and instructs the Company to repay the entire principal amount of this
Security, or the portion thereof (which is $1,000 or an integral multiple
thereof) below designated, in accordance with the terms of the Indenture
referred to in this Security at the Repayment Price (or the relevant percentage
thereof), together with accrued interest to such date (except if the Repayment
Date shall be an Interest Payment Date), to the holder hereof.


Dated: ________________________


                                                 _______________________________
                                                 Signature*(s)

                                                 Name: _______________________
                                                 Address:_____________________
                                                         _____________________
                                                 [* Signature Guarantee 
                                                 Required]

                                                 Principal amount to be repaid
                                                 (if less than all):

                                                 $__________

                                                 NOTICE: If this Security is
                                                 issued in registered form, the
                                                 above signatures of the
                                                 holder(s) hereof must
                                                 correspond with the name as it
                                                 appears in the Security in
                                                 every particular without
                                                 alteration or enlargement or
                                                 any change whatever.


____________________________
Social Security or Other
Taxpayer Identification Number

                                      -14-

<PAGE>
 
                                                                    EXHIBIT 4.4

                (FORM OF FACE OF REGISTERED GLOBAL SECURITIES)

Unless this Security is presented by an authorized representative of The
Depository Trust Company ("DTC"), 55 Water Street, New York, New York to the
issuer or its agent for registration of transfer, exchange or payment, and such
Security issued is registered in the name of CEDE & CO., or such other name as
requested by an authorized representative of DTC, ANY TRANSFER, PLEDGE OR OTHER
USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL, since the
registered owner hereof, CEDE & CO., has an interest herein.

Unless and until this Security is exchanged in whole or in part for Securities
in certificated form, this Security may not be transferred except as a whole by
DTC to a nominee thereof or by a nominee thereof to DTC or another nominee of
DTC or by DTC or any such nominee to a successor of DTC or a nominee of such
successor.

                        THERMO INSTRUMENT SYSTEMS INC.
                    (Incorporated in the State of Delaware)


                 4% CONVERTIBLE SUBORDINATED GLOBAL DEBENTURE
                             DUE JANUARY 15, 2005
                     GUARANTEED ON A SUBORDINATED BASIS BY
                          THERMO ELECTRON CORPORATION
                    (Incorporated in the State of Delaware)

No. R-________________

Cusip: 883559AE6
      ________________

     Thermo Instrument Systems Inc., a Delaware corporation (herein referred
to as the "Company," which term includes any successor corporation under the
Indenture referred to on the reverse hereof), for value received, hereby
promises to pay to Cede & Co. or registered assigns the principal sum of _______
Dollars (or any other amounts as are endorsed on the Schedule of Adjustments
hereto) plus any premium, if any, on January 15, 2005 (the "Stated Maturity")
upon the presentation and surrender hereof or, at the option of the Company, in
whole or in part at any time on or after January 15, 2001, upon notice as
described in the Indenture and to pay interest thereon from January 21, 1998 or
from the most recent Interest Payment Date to which interest has been paid or
duly provided for, semi-annually in arrears on January 15 and July 15 in each
year (each, an "Interest Payment Date"), commencing July 15, 1998, at the rate
of 4% per annum, and Additional Amounts, if any, until the principal hereof is
paid or duly provided for. The interest and Additional Amounts, if any, so
payable, and punctually paid or duly provided for, on any Interest Payment Date
will, as provided in such Indenture, be paid to the Holder in whose name this
Security (or one or more Predecessor Securities) is registered at the close of
business on the Regular Record Date for such interest, which shall be the
January 1 or July 1 (whether or not a Business Day), as the case may be, next
preceding such Interest
<PAGE>
 
Payment Date at the Office or Agency of the Company maintained for such
purpose; provided, however, that such interest may be paid, at the Company's
         --------  -------
option, by mailing a check to such Holder at its registered address or by
transfer of funds to an account maintained by such Holder within the United
States. Any such interest not so punctually paid or duly provided for shall
forthwith cease to be payable to the Holder on such Regular Record Date, and may
be paid to the Holder in whose name this Security (or one or more Predecessor
Securities) is registered at the close of business on a Special Record Date for
the payment of such Defaulted Interest to be fixed by the Trustee, notice
whereof shall be given to Holders of Securities of this series not less than 10
days prior to such Special Record Date, or may be paid at any time in any other
lawful manner not inconsistent with the requirements of any securities exchange
on which the Securities of this series may be listed, and upon such notice as
may be required by such exchange, all as more fully provided in the Indenture.
Interest will be computed on the basis of a 360-day year of twelve 30-day
months. All payments hereunder shall be made in United States Dollars.

     Subject to the applicable provisions of the Indenture, the aggregate
principal amount represented by this global Security may be decreased to reflect
exchanges or partial conversions, redemptions or repayments, by endorsing the
Schedule of Adjustments hereto, and the principal amount hereof shall be deemed
to be decreased for all purposes by the amount so exchanged, converted, redeemed
or repaid, as applicable.

     Reference is hereby made to the further provisions of this Security set
forth on the reverse hereof, which further provisions shall for all purposes
have the same effect as if set forth at this place.

     Unless the Certificate of Authentication hereon has been executed by
the Trustee by manual signature of one of its authorized signatories, this
Security shall not be entitled to any benefit under the Indenture, or be valid
or obligatory for any purpose.

                                      -2-
<PAGE>
 
     IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed under its facsimile corporate seal.

Dated:  January __, 1998                     THERMO INSTRUMENT SYSTEMS INC.

                                             By:_______________________
Attest:                                          [Name]
                                                 [Title]
_______________________________
Secretary

[SEAL]


                          CERTIFICATE OF AUTHENTICATION

         This is one of the Securities of the series designated therein referred
to in the within-mentioned Indenture.

                                                  BANKERS TRUST COMPANY,
                                                  as Trustee


                                                  By:________________________
                                                      Authorized Officer

                                      -3-
<PAGE>
 
               (FORM OF REVERSE OF REGISTERED GLOBAL SECURITIES)

                        THERMO INSTRUMENT SYSTEMS INC.


     This Security is one of a duly authorized issue of securities of the
Company (herein called the "Securities"), issued and to be issued in one or more
series under an Indenture, dated as of January 15, 1998 (herein called the
"Indenture") by the Company, as issuer, and Thermo Electron Corporation, as
guarantor (herein called the "Guarantor," which term includes any successor
corporation under the Indenture), to Bankers Trust Company, as Trustee (herein
called the "Trustee," which term includes any successor trustee under the
Indenture with respect to the series of which this Security is a part), to which
Indenture and all indentures supplemental thereto reference is hereby made for a
statement of the respective rights, limitations of rights, duties and immunities
thereunder of the Company, the Guarantor, the Trustee and the Holders of the
Securities and any Coupons appertaining thereto, and of the terms upon which the
Securities are, and are to be, authenticated and delivered. This Security is one
of the duly authorized series of Securities designated on the face hereof and
the aggregate principal amount of the Securities to be issued under such series
is limited to $250,000,000 (except for Securities authenticated and delivered
upon transfer of, or in exchange for, or in lieu of other Securities). The
Guarantor has unconditionally guaranteed on a subordinated basis the payment of
principal, premium, if any, and interest on the Securities. The Holders of the
Securities will be entitled to the benefits of, be bound by, and be deemed to
have notice of, all of the provisions of the Indenture. A copy of the Indenture
is on file and may be inspected at the office of the Paying Agents appointed by
the Company. All terms used in this Security which are defined in the Indenture
shall have the meanings assigned to them in the Indenture.

     The Securities are issuable as bearer securities (the "Bearer
Securities"), with interest Coupons attached, in the denominations of U.S.
$1,000 and U.S. $10,000, and as registered securities (the "Registered
Securities"), without Coupons, in denominations of U.S. $1,000 and integral
multiples thereof, except as otherwise provided in or pursuant to the Indenture.
The Registered Securities, and transfers thereof, shall be registered as
provided in the Indenture. The holder of any Bearer Security or any Coupon
appertaining thereto and the registered holder of a Registered Security shall
(to the fullest extent permitted by applicable law) be treated at all times, by
all persons and for all purposes as the absolute owner of such Security or
Coupon, as the case may be, regardless of any notice of ownership, theft or loss
or of any writing thereon. Bearer Securities may be exchanged for Registered
Securities as set forth in the Indenture. Registered Securities may not be
exchanged for Bearer Securities.

     The Securities are general, unsecured obligations of the Company,
subordinated in right of payment to the prior payment in full of all existing
and future Senior Indebtedness of the Company to the extent set forth in Article
Seventeen of the Indenture. There are no restrictions herein on other
indebtedness or securities which may be incurred or issued by the Company or the
Guarantor.

     Additional Amounts shall be payable on the Securities as set forth in
the Indenture.

                                      -4-
<PAGE>
 
     If an Event of Default, as defined in the Indenture, shall occur and be
continuing, the principal of the Securities of this series may be declared due
and payable in the manner and with the effect provided in the Indenture.

     Subject to the terms of the Indenture, the Securities are convertible
at any time prior to Maturity at an initial Conversion Price of $35.65 per
share, subject to adjustment as provided in the Indenture. Accrued interest from
the immediately preceding Interest Payment Date until the Conversion Date will
be paid within five Business Days after the Conversion Date. In case this
Security, or a portion thereof, is called for redemption, or is delivered for
repayment, the conversion right in respect of this Security or a portion thereof
so called and delivered shall expire on the close of business on the fifth
Business Day preceding the Redemption Date or the second Business Day preceding
a repayment on the Repayment Date, as the case may be, unless the Company
defaults in making the payment due upon redemption or repayment, as the case may
be. To convert this Security, the Holder must surrender this Security, duly
endorsed or assigned to the Company, at any applicable Place of Conversion,
accompanied by a duly signed conversion notice. Bearer Securities surrendered
for conversion must be surrendered together with all Coupons appertaining
thereto that mature after the Conversion Date, except as otherwise provided in
the Indenture.

     The Securities are subject to redemption at any time on or after
January 15, 2001, as a whole or in part, at the option of the Company, at a
Redemption Price equal to 100% of the principal amount, together in the case of
any such redemption with accrued interest to the Redemption Date as provided in
the Indenture. Notice of redemption will be given to Holders of Securities, not
less than 20 nor more than 60 days prior to the Redemption Date, all as provided
in the Indenture. Subject to the terms of the Indenture, if as a result of a Tax
Law Change the Company has or will become obligated to pay to the Holder of any
Tax Affected Security Additional Amounts, and such obligation cannot be avoided
by the Company taking reasonable measures available to it, then the Company may,
at its option, redeem the Tax Affected Securities as a whole, but not in part,
upon not less than 20 nor more than 60 days' notice to the Holders prior to the
Redemption Date therefor, at a Redemption Price equal to 100% of the principal
amount plus interest accrued to the Redemption Date, and any Additional Amounts
then payable.

     Subject to the terms of the Indenture, the Securities are subject to
repayment at the option of the Holder thereof, in whole or in part, on the
Repayment Date, if the Common Stock (or other equity securities into which this
Security is then convertible) is neither listed for trading on a United States
national securities exchange, the Nasdaq National Market nor approved for
trading on an established automated over-the-counter trading market in the
United States. In such event, the Securities shall be repaid at a price equal to
the principal amount hereof, plus accrued interest and Additional Amounts, if
any. The Holders of Securities of this series desiring to be repaid must deliver
(1) this Security with the "Option to Elect Repayment" duly signed and
completed, or (2) such other documentation as may be provided by the Indenture,
to the Trustee at the Place of Payment not earlier than 60 days nor later than
30 days prior to the Repayment Date. Bearer 

                                      -5-
<PAGE>
 
Securities must be surrendered together with all Coupons appertaining thereto
that mature after the Repayment Date, except as otherwise provided in the
Indenture.

     The Place of Payment, place of registration of transfer and exchange
and the Place of Conversion for the Registered Securities and the Guarantees
endorsed thereon, shall be the Borough of Manhattan, The City of New York, and
the Corporate Trust Office of the Trustee shall be the Company's and the
Guarantor's Office or Agency in the Borough of Manhattan, The City of New York
for such purpose. The Places of Payment and Places of Conversion for the Bearer
Securities and the Guarantees endorsed thereon, shall be London, England and
Luxembourg, and the offices of the Trustee in London and Luxembourg shall be the
Offices or Agencies for such purpose and the offices of the Trustee in London
and Luxembourg shall be the Company's and the Guarantor's Paying Agent in London
and Luxembourg, respectively.

     The Trustee initially shall be the Security Registrar, one of the
Authenticating Agents, the Paying Agent and the Conversion Agent. The Trustee
presently has its Corporate Trust Office at Four Albany Street, 4th Floor, New
York, NY 10006, its Office in London at 1 Appold Street, Broadgate, London, EC2A
2HE, England, and its Office in Luxembourg at 14 Boulevard F.D. Roosevelt,
L-2450 Luxembourg. The Company and the Guarantor may subsequently appoint an
Office or Agency in addition to or other than the Borough of Manhattan, The City
of New York with respect to the Registered Securities and London, England and
Luxembourg with respect to the Bearer Securities.

     The Indenture permits, with certain exceptions as therein provided, the
amendment thereof and the modification of the rights and obligations of the
Company and the Guarantor and the rights of the Holders of the Securities under
the Indenture at any time by the Company, the Guarantor and the Trustee with the
consent of the Holders of not less than a majority of the aggregate principal
amount of all Securities issued under the Indenture at the time Outstanding and
affected thereby. The Indenture also contains provisions permitting the Holders
of not less than a majority of the aggregate principal amount of the Outstanding
Securities, on behalf of the Holders of all such Securities, to waive compliance
by the Company and the Guarantor with certain provisions of the Indenture.
Furthermore, provisions in the Indenture permit the Holders of not less than a
majority of the aggregate principal amount, in certain instances, of the
Outstanding Securities of any series to waive, on behalf of all of the Holders
of Securities of such series, certain past defaults under the Indenture and
their consequences. Any such consent or waiver by the Holder of this Security
shall be conclusive and binding upon such Holder and upon all future Holders of
this Security and other Securities issued upon the registration of transfer
hereof or in exchange herefor or in lieu hereof, whether or not notation of such
consent or waiver is made upon this Security.

     No reference herein to the Indenture and no provision of this Security
or of the Indenture shall alter or impair the obligation of the Company, which
is absolute and unconditional (except as to the specific subordination
provisions contained in Article Seventeen of the Indenture), to pay the
principal of, premium, if any, interest and Additional Amounts, if any, on this
Security at the times, places and rates, and in the coin or currency, herein
prescribed.

                                      -6-
<PAGE>
 
     No service charge shall be made for any registration of transfer or
exchange, but the Company may require payment of a sum sufficient to cover any
tax or other governmental charge payable in connection therewith.

     The Indenture and the Securities shall be governed by and construed in
accordance with the laws of the Commonwealth of Massachusetts applicable to
agreements made and to be performed entirely in such Commonwealth except that
the rights, protections, obligations, indemnities and immunities of the Trustee
under the Indenture and the Securities shall be governed by the laws of the
State of New York, without regard to the principles of conflicts of laws of
either state.

                                      -7-
<PAGE>
 
                            SCHEDULE OF ADJUSTMENTS

                                          Remaining           Notation
                Principal                 principal amount    made on
                amount                    following such      behalf of the
Date made       adjustment                adjustment          Trustee
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------       -----------------
                                                            
- --------------  --------------------      -------------      ------------------

- -------------------------------------------------------------------------------

                                      -8-
<PAGE>
 
                                    GUARANTEE

     For value received, Thermo Electron Corporation, a corporation
organized under the laws of the State of Delaware (herein called the
"Guarantor," which term includes any successor corporation under the Indenture
referred to in the Security upon which this Guarantee is endorsed), hereby
unconditionally guarantees to the Holder of the Security upon which this
Guarantee is endorsed and to the Trustee on behalf of the Trustee and such
Holder the due and punctual payment of the principal of, premium, if any, and
interest and Additional Amounts, if any, on such Security, any other amount due
and payable pursuant to the terms of the Indenture and the due and punctual
payment of the sinking fund or analogous payments referred to therein if any,
when and as the same shall become due and payable, whether at the Stated
Maturity, by declaration of acceleration, call for redemption, repayment at the
option of the Holder or otherwise, according to the terms thereof and of the
Indenture. In case of the failure of Thermo Instrument Systems Inc., a
corporation organized under the laws of Delaware (herein called the "Company,"
which term includes any successor corporation under such Indenture), punctually
to make any such payment of principal, premium, if any, or interest or
Additional Amounts, if any, the Guarantor hereby agrees to cause any such
payment to be made punctually when and as the same shall become due and payable,
whether at the Stated Maturity or by declaration of acceleration, call for
redemption, repayment at the option of the Holder or otherwise, and as if such
payment were made by the Company.

     The Guarantor hereby agrees that its obligations hereunder shall be as
if it were principal debtor and not merely surety, and shall be absolute and
unconditional (except as to the specific subordination provisions contained in
Article Eighteen of the Indenture), irrespective of, and shall be unaffected by,
any invalidity, subordination, irregularity or unenforceability of such Security
or such Indenture, any failure to enforce the provisions of such Security or
such Indenture, or any waiver, modification or indulgence granted to the Company
with respect thereto, by the Holder of such Security or the Trustee or any other
circumstance which may otherwise constitute a legal or equitable discharge of a
surety or guarantor. The Guarantor hereby waives the benefits of diligence,
presentment, demand of payment, filing of claims with a court in the event of
merger, insolvency or bankruptcy of the Company, any right to require a
proceeding first against the Company, protest or notice with respect to such
Security or the indebtedness evidenced thereby and all demands whatsoever, and
covenants that this Guarantee will not be discharged except by strict and
complete performance of the obligations contained in such Security and this
Guarantee. The Guarantor hereby agrees that, in the event of a default in
payment of principal of, premium, if any, and interest, and Additional Amounts,
if any, on such Security, or default in any sinking fund or analogous payment
referred to therein, legal proceedings may be instituted by the Trustee on
behalf of, or by, the Holder of such Security, on the terms and conditions set
forth in the Indenture, directly against the Guarantor to enforce this Guarantee
without first proceeding against the Company.

     The Guarantor shall be subrogated to all rights of the Holder of such
Security and the Trustee against the Company in respect of any amounts paid to
such Holder by the Guarantor on account of such Security pursuant to the
provisions of this Guarantee or the Indenture; provided, however, that the
                                               --------  -------
Guarantor shall not be entitled to enforce, or to receive any payments arising

                                      -9-
<PAGE>
 
out of or based upon, such right of subrogation until the principal of, premium,
if any, and interest and Additional Amounts, if any, on all Securities issued
under such Indenture shall have been paid in full.

     Claims under this Guarantee are, to the extent provided in the
Indenture, subject in right of payment to the prior payment in full of all
Senior Guarantor Indebtedness, and this Guarantee is issued subject to the
provisions of the Indenture with respect thereto. Each Holder of a Security upon
which this Guarantee is endorsed, by accepting the same, (a) agrees to and shall
be bound by such provisions, (b) authorizes and directs the Trustee on his
behalf to take such action as may be necessary or appropriate to effectuate the
subordination so provided and (c) appoints the Trustee his, her or its
attorney-in-fact for any and all such purposes.

     No reference herein to such Indenture and no provision of this
Guarantee or of such Indenture shall alter or impair the guarantee of the
Guarantor, which is absolute and unconditional (except as to the specific
subordination provisions contained in Article Eighteen of the Indenture), of the
due and punctual payment of principal, premium (if any), and interest and
Additional Amounts, if any, on the Security upon which this Guarantee is
endorsed.

     This Guarantee shall not be valid or obligatory for any purpose until
the certificate of authentication of the Security upon which this Guarantee is
endorsed shall have been manually executed by or on behalf of the Trustee under
such Indenture.

     All terms used in this Guarantee which are defined in such Indenture
shall have the meanings assigned to them in such Indenture.

     This Guarantee shall be deemed to be a contract made under the laws of
the Commonwealth of Massachusetts, and for all purposes shall be governed by and
construed in accordance with the laws of the Commonwealth of Massachusetts.

     IN WITNESS WHEREOF, the Guarantor has caused this Guarantee to be duly
executed under its corporate seal and dated the date on the face hereof.

                                             THERMO ELECTRON CORPORATION


Attest:______________________________        By: _____________________________

                                             Title: __________________________

                                      -10-
<PAGE>
 
         This is one of the Securities of the series designated therein referred
to in the within-mentioned Indenture.

Dated:  _______________________              BANKERS TRUST COMPANY,
                                             as Trustee



                                             By: ______________________________
                                                       Authorized Officer

                                      -11-
<PAGE>
 
                                 TRANSFER NOTICE


FOR VALUE RECEIVED, the undersigned Holder hereby sell(s), assign(s) and 
transfer(s) unto ______________________________________________________________
whose taxpayer identification number is _____________________ and whose address
including postal/zip code is _____________________________________ the within
Security and all rights thereunder, hereby irrevocably constituting and
appointing _____________________________ attorney-in-fact to transfer said
Security on the books of the Security Registrar with full power of substitution
in the premises.


Dated: __________________________      Name: ____________________________

                                       By: ______________________________

                                       Title: ___________________________

                                       NOTICE: The signature of the
                                       Holder to this assignment must
                                       correspond with the name as
                                       written upon the face of the
                                       within instrument in every
                                       particular, without enlargement
                                       or any change whatsoever.

                                       SIGNATURE GUARANTEED


                                       ____________________________________


                                      -12-
<PAGE>
 
                               CONVERSION NOTICE



     The undersigned Holder of this Security hereby irrevocably exercises
the option to convert this Security, or any portion of the principal amount
hereof (which is an integral multiple of U.S. $1,000 below designated), into
shares of Common Stock in accordance with the terms of the Indenture referred to
in this Security, and directs that such shares, together with a check in payment
for any fractional share and any Securities representing any unconverted
principal amount hereof, be delivered to and be registered in the name of the
undersigned unless a different name has been indicated below. If shares or
Securities are to be registered in the name of a Person other than the
undersigned, the undersigned will pay all transfer taxes payable with respect
thereto.


Dated: ___________________________          ___________________________________
                                                          Signature
                                            [MUST BE GUARANTEED IF STOCK
                                            OR SECURITIES ARE TO BE ISSUED
                                            IN A NAME OTHER THAN THE 
                                            REGISTERED HOLDER OF THE
                                            SECURITY]

____________________________________
               Name

____________________________________
             Address

____________________________________
Social Security or other Taxpayer 
Identification Number, if any

                                      -13-
<PAGE>
 
If shares or Registered Securities are     If only a portion of the Securities 
to be registered in the name of a Person   is to be converted, please indicate:
other than the Holder, please print
such Person's name and address:            1. Principal amount to be converted:

                                           U.S. $___________________

_______________________________            2. Principal amount and denomination
            Name                              of Registered Securities
                                              representing unconverted
                                              principal amount to be issued.
_______________________________
           Address
                                           Amount:  U.S.$_________________
_______________________________
Social Security or other Taxpayer          Denominations:
Identification Number, if any              U.S.$__________
                                           (any integral multiple of 
                                            U.S. $1,000)

_______________________________



                           OPTION TO ELECT REPAYMENT
                            UPON A REPAYMENT EVENT


To:  Thermo Instrument Systems Inc.

     The undersigned owner of this Security hereby acknowledges receipt of a
notice from Thermo Instrument Systems Inc.(the "Company") as to the occurrence
of a Repayment Event with respect to the Common Stock of the Company and
requests and instructs the Company to repay the entire principal amount of this
Security, or the portion thereof (which is $1,000 or an integral multiple
thereof) below designated, in accordance with the terms of the Indenture
referred to in this Security at the Repayment Price (or the relevant percentage
thereof), together with accrued interest to such date (except if the Repayment
Date shall be an Interest Payment Date), to the holder hereof.


Dated: ________________________


                                              _______________________________
                                              Signature*(s)

                                      -14-
<PAGE>
 
                                              Name: ___________________________
                                              Address:_________________________

                                                 ______________________________
                                              [* Signature Guarantee Required]

                                              Principal amount to be repaid
                                              (if less than all):

                                              $__________________

                                              NOTICE: If this Security is
                                              issued in registered form, the
                                              above signatures of the
                                              holder(s) hereof must
                                              correspond with the name as it
                                              appears in the Security in
                                              every particular without
                                              alteration or enlargement or
                                              any change whatever.


_______________________________
Social Security or Other
Taxpayer Identification Number

                                      -15-

<PAGE>
 
                                                                     EXHIBIT 4.5
                                                                                
               FORM OF CONVERTIBLE SUBORDINATED BEARER SECURITY
                              [Face of Security]

ANY UNITED STATES PERSON WHO HOLDS THIS SECURITY WILL BE SUBJECT TO LIMITATIONS
UNDER THE UNITED STATES INCOME TAX LAWS, INCLUDING THE LIMITATIONS PROVIDED IN
SECTIONS 165(j) AND 1287(a) OF THE UNITED STATES INTERNAL REVENUE CODE.

                         THERMO INSTRUMENT SYSTEMS INC.
                    (INCORPORATED IN THE STATE OF DELAWARE)


                     4% CONVERTIBLE SUBORDINATED DEBENTURE
                             DUE JANUARY 15, 2005
                     GUARANTEED ON A SUBORDINATED BASIS BY
                          THERMO ELECTRON CORPORATION
                    (INCORPORATED IN THE STATE OF DELAWARE)

NO. ____________                                                   $____________

          Thermo Instrument Systems Inc., a Delaware corporation (herein
referred to as the "Company," which term includes any successor corporation
under the Indenture referred to on the reverse hereof), for value received,
hereby promises to pay to bearer upon presentation and surrender hereof the
principal sum of $_______ United States Dollars plus any premium, if any, on
January 15, 2005 (the "Stated Maturity") or, at the option of the Company, in
whole or in part at any time on or after January 15, 2001, upon notice as
described in the Indenture and to pay interest thereon from January 21, 1998 or
from the most recent Interest Payment Date to which interest has been paid or
duly provided for, semi-annually in arrears on January 15 and July 15 in each
year (each, an "Interest Payment Date"), commencing July 15, 1998, at the rate
of 4% per annum, and Additional Amounts, if any, until the principal hereof is
paid or duly provided for. The interest and Additional Amounts, if any, so
payable, and punctually paid or duly provided for, on any Interest Payment Date
will, as provided in such Indenture, be paid to the Holder surrendering the
appropriate Coupon appertaining hereto. Interest will be computed on the basis
of a 360-day year of twelve 30-day months.

          Such payments (including premium, if any) shall be made in United
States Dollars.  The Company shall maintain, subject to any laws or regulations
applicable thereto, an Office or Agency in a Place of Payment that is located
outside the United States where this Security and any Coupons appertaining
hereto, and Guarantees with respect hereto, may be presented and surrendered for
payment.  Subject to the right of the Company (limited as provided in the
Indenture) to change the location of any Office or Agency, the  Place of Payment
and Place of Conversion with respect to this Security shall be either at the
London office of Bankers Trust Company located at 1 Appold Street, Broadgate, 
London, EC2A 2HE, England, at Bankers Trust 

<PAGE>
 
Luxembourg, S.A. located at 14 Boulevard, F.D. Roosevelt, L-2450 Luxembourg or
at such other Offices or Agencies outside the United States as the Company may
designate. Such payments shall be made by United States Dollar check drawn on a
bank in the City of New York, or (at the option of the Company with the consent
of the Paying Agent) by transfer to a United States Dollar account maintained by
the Holder at a bank located outside the United States. Interest on this
Security shall be paid only at an Office or Agency located outside the United
States and, in the case of interest due on or before Maturity, only upon
presentation and surrender at such an Office or Agency of the applicable
interest Coupons hereto attached as they severally mature. No payment on this
Security or any Coupon will be made at the Corporate Trust Office of the Trustee
or any other Paying Agent maintained by the Company in the United States, nor
will any payment be made by transfer to an account in the United States, except
as may be permitted by United States tax laws and regulations in effect at the
time of such payment without detriment to the Company. Notwithstanding the
foregoing, payment of this Security and Coupons may be made at the Corporate
Trust Office of the Trustee in the City of New York if full payment at all
Paying Agents outside the United States is illegal or effectively precluded by
exchange controls or other similar restrictions.

          Reference is hereby made to the further provisions of this Security
set forth on the reverse hereof, which further provisions shall for all purposes
have the same effect as if set forth at this place.

          Unless the Certificate of Authentication hereon has been executed by
the Trustee by manual signature of one of its authorized signatories, this
Security shall not be entitled to any benefit under the indenture, or be valid
or obligatory for any purpose.

                                      -2-
<PAGE>
 
    IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed under its facsimile corporate seal.

Dated: January __, 1998                     THERMO INSTRUMENT SYSTEMS INC.
                                            
                                            By:_______________________
Attest:                                        Name
                                               Title
_______________________________
Secretary

[SEAL]

                         CERTIFICATE OF AUTHENTICATION

  This is one of the Securities of the series designated therein referred to in
the within-mentioned Indenture.

                              BANKERS TRUST COMPANY,
                              As Trustee

                                 BY:_____________________________
                                    Authorized Officer

                                      -3-
<PAGE>
 
                 (FORM OF FACE OF COUPON ON BEARER SECURITIES)

ANY UNITED STATES PERSON WHO HOLDS THIS SECURITY WILL BE SUBJECT TO LIMITATIONS
UNDER THE UNITED STATES INCOME TAX LAWS, INCLUDING THE LIMITATIONS PROVIDED IN
SECTIONS 165(j) AND 1287(a) OF THE UNITED STATES INTERNAL REVENUE CODE.

                         THERMO INSTRUMENT SYSTEMS INC.
                    (Incorporated in the State of Delaware)

                4% CONVERTIBLE SUBORDINATED DEBENTURE DUE 2005

                                              No:  _____________

                                              U.S.$____________

                                              Due:

          Unless the Security to which this Coupon appertains shall have been
called for redemption or presented for repayment prior to the due date hereof
and payment thereof duly provided for or shall have been converted, Thermo
Instrument Systems Inc. (herein called the "Company") shall, subject to and in
accordance with the terms and conditions of the Bearer Security and the
Indenture dated as of January 15, 1998 by the Company, as issuer, and Thermo
Electron Corporation, as guarantor, to Bankers Trust Company, as Trustee, pay to
the bearer, on the date set forth herein upon surrender hereof, the amount shown
hereon (together with any Additional Amounts in respect thereof which the
Company may be required to pay according to the terms of said Indenture) at the
offices of the Paying Agent set out on the reverse hereof or at such other
places outside the United States as the Company may determine from time to time,
by United States Dollar check drawn on a bank in the City of New York, or (at
the option of the Company with the consent of the Paying Agent) by transfer to a
United States Dollar account maintained by the bearer at a bank outside the
United States, being one-half year's interest then payable on said Security.

                                              THERMO INSTRUMENT SYSTEMS INC.


                                              By:___________________________
                                                 Name:
                                                 Title:
Attest:

__________________________

                                      -4-
<PAGE>
 
                              [Reverse of Coupon]


Bankers Trust Company                         Bankers Trust Luxembourg, S.A.
1 Appold Street                               14 Boulevard, F.D. Roosevelt
Broadgate, London EC2A 2HE                    L-2450 Luxembourg
England

                                      -5-
<PAGE>
 
                     (FORM OF REVERSE OF BEARER SECURITIES)

                         THERMO INSTRUMENT SYSTEMS INC.


          This Security is one of a duly authorized issue of securities of the
Company (herein called the "Securities"), issued and to be issued in one or more
series under an Indenture, dated as of January 15, 1998 (herein called the
"Indenture") by the Company, as issuer, and Thermo Electron Corporation, as
guarantor (herein called the "Guarantor," which term includes any successor
corporation under the Indenture), to Bankers Trust Company, as Trustee (herein
called the "Trustee," which term includes any successor trustee under the
Indenture with respect to the series of which this Security is a part), to which
Indenture and all indentures supplemental thereto reference is hereby made for a
statement of the respective rights, limitations of rights, duties and immunities
thereunder of the Company, the Guarantor, the Trustee and the Holders of the
Securities and any Coupons appertaining thereto, and of the terms upon which the
Securities are, and are to be, authenticated and delivered. This Security is one
of the duly authorized series of Securities designated on the face hereof and
the aggregate principal amount of the Securities to be issued under such series
is limited to $250,000,000 (except for Securities authenticated and delivered
upon transfer of, or in exchange for, or in lieu of other Securities). The
Guarantor has unconditionally guaranteed on a subordinated basis the payment of
principal, premium, if any, and interest on the Securities. The Holders of the
Securities will be entitled to the benefits of, be bound by, and be deemed to
have notice of, all of the provisions of the Indenture. A copy of the Indenture
is on file and may be inspected at the office of the Paying Agent appointed by
the Company. All terms used in this Security which are defined in the Indenture
shall have the meanings assigned to them in the Indenture.

          The Securities are issuable as bearer securities (the "Bearer
Securities"), with interest Coupons attached, in the denominations of U.S.
$1,000 AND U.S. $10,000, and as registered securities (the "Registered
Securities"), without Coupons, in denominations of U.S. $1,000 and integral
multiples thereof, except as otherwise provided in or pursuant to the Indenture.
The Registered Securities, and transfers thereof, shall be registered as
provided in the Indenture.  The holder of any Bearer Security or any Coupon
appertaining thereto and the registered holder of a Registered Security shall
(to the fullest extent permitted by applicable law) be treated at all times, by
all persons and for all purposes as the absolute owner of such Security or
Coupon, as the case may be, regardless of any notice of ownership, theft or loss
or of any writing thereon.  Bearer Securities may be exchanged for Registered
Securities as set forth in the Indenture.  Registered Securities may not be
exchanged for Bearer Securities.

          The Securities are general, unsecured obligations of the Company,
subordinated in right of payment to the prior payment in full of all existing
and future Senior Indebtedness of the Company to the extent set forth in Article
Seventeen of the Indenture.  There are no restrictions herein on other
indebtedness or securities which may be incurred or issued by the Company or the
Guarantor.

          The Securities have been approved for listing on the American Stock 
Exchange (the "AMEX"). Contracts for Securities traded on the AMEX must be 
settled in Registered Securities.

          Additional Amounts shall be payable on the Securities as set forth in
the Indenture.

                                      -6-
<PAGE>
 
          If an Event of Default, as defined in the indenture, shall occur and
be continuing, the principal of the Securities of this series may be declared
due and payable in the manner and with the effect provided in the Indenture.

          Subject to the terms of the Indenture, the Securities are convertible
at any time prior to Maturity at an initial Conversion Price of $35.65 per 
share, subject to adjustment as provided in the Indenture. Accrued interest from
the immediately preceding Interest Payment Date until the Conversion Date will
be paid within five Business Days after the Conversion Date. In case this
Security, or a portion thereof, is called for redemption, or is delivered for
repayment, the conversion right in respect of this Security or a portion thereof
so called and delivered shall expire on the close of business on the fifth
Business Day preceding the Redemption Date or the second Business Day preceding
a repayment on the Repayment Date, as the case may be, unless the Company
defaults in making the payment due upon redemption or repayment, as the case may
be. To convert this Security, the Holder must surrender this Security, duly
endorsed or assigned to the company, at any applicable place of conversion,
accompanied by a duly signed conversion notice. Bearer Securities surrendered
for conversion must be surrendered together with all Coupons appertaining
thereto that mature after the Conversion Date, except as otherwise provided in
the Indenture.

          The Securities are subject to redemption at any time on or after
January 15, 2001, as a whole or in part, at the option of the Company, at a
Redemption Price equal to 100% of the principal amount, together in the case of
any such redemption with accrued interest to the Redemption Date as provided in
the Indenture.  Notice of redemption will be given to Holders of Securities, not
less than 20 nor more than 60 days prior to the Redemption Date, all as provided
in the Indenture.  Subject to the terms of the indenture, if as a result of a
Tax Law Change the Company has or will become obligated to pay to the Holder of
any Tax Affected Security Additional Amounts, and such obligation cannot be
avoided by the Company taking reasonable measures available to it, then the
Company may, at its option, redeem the Tax Affected Securities as a whole, but
not in part, upon not less than 20 nor more than 60 days' notice to the Holders
prior to the Redemption Date therefor, at a Redemption Price equal to 100% of
the principal amount plus interest accrued to the Redemption Date, and any
Additional Amounts then payable.

          Subject to the terms of the Indenture, the Securities are subject to
repayment at the option of the Holder thereof, in whole or in part, on the
Repayment Date, if the Common Stock (or other equity securities into which this
Security is then convertible) is neither listed for trading on a United States
national securities exchange, the Nasdaq National Market nor approved for
trading on an established automated over-the-counter trading market in the
United States. In such event, the Securities shall be repaid at a price equal to
the principal amount hereof, plus accrued interest 

                                      -7-
<PAGE>
 
and Additional Amounts, if any. The Holders of Securities of this series
desiring to be repaid must deliver (1) this Security with the "Option to Elect
Repayment" duly signed and completed, or (2) such other documentation as may be
provided by the Indenture, to the Trustee at the Place of Payment not earlier
than 60 days nor later than 30 days prior to the Repayment Date. Bearer
Securities must be surrendered together with all Coupons appertaining thereto
that mature after the Repayment Date, except as otherwise provided in the
Indenture.

     In the event of redemption, exchange, repayment or conversion of this
Security in part only, a new Security or Securities for the unredeemed,
unexchanged, unrepaid or unconverted portion hereof shall be issued to the
Holder hereof upon the cancellation hereof as set forth in the Indenture.

     The Place of Payment, place of registration of transfer and exchange and
the Place of Conversion for the Registered Securities and the Guarantees
endorsed thereon, shall be the Borough of Manhattan, The City of New York, and
the Corporate Trust Office of the Trustee shall be the Company's and the
Guarantor's Office or Agency in the Borough of Manhattan, The City of New York
for such purpose.  The Places of Payment and Places of Conversion for the Bearer
Securities and the Guarantees endorsed thereon, shall be London, England and
Luxembourg, and the offices of the Trustee in London and Luxembourg shall be the
Offices or Agencies for such purpose and the offices of the Trustee in London
and Luxembourg shall be the Company's and the Guarantor's Paying Agent in London
and Luxembourg, respectively.

     The Trustee initially shall be the Security Registrar, one of the
Authenticating Agents, the Paying Agent and the Conversion Agent.  The Trustee
presently has its Corporate Trust Office at Four Albany Street, 4th floor, New
York, NY 10006, its Office in London at 1 Appold Street, Broadgate, London, EC2A
2HE, England and its Office in Luxembourg at 14 Boulevard, F.D. Roosevelt, L-
2450 Luxembourg. The Company and the Guarantor may subsequently appoint an
Office or Agency in addition to or other than the Borough of Manhattan, The City
of New York with respect to the Registered Securities and London, England and
Luxembourg with respect to the Bearer Securities.

     The Indenture permits, with certain exceptions as therein provided, the
amendment thereof and the modification of the rights and obligations of the
Company and the Guarantor and the rights of the Holders of the Securities under
the Indenture at any time by the Company, the Guarantor and the Trustee with the
consent of the Holders of not less than a majority of the aggregate principal
amount of all Securities issued under the Indenture at the time Outstanding and
affected thereby. The Indenture also contains provisions permitting the Holders
of not less than a majority of the aggregate principal amount of the Outstanding
Securities, on behalf of the Holders of all such Securities, to waive compliance
by the Company or the Guarantor with certain provisions of the Indenture.
Furthermore, provisions in the Indenture permit the Holders of not less than a
majority of the aggregate principal amount, in certain instances, of the
Outstanding Securities of any series to waive, on behalf of all of the Holders
of Securities of such series, certain past defaults under the Indenture and
their consequences. Any such consent or waiver by the Holder of this Security
shall be conclusive and binding upon such Holder and upon all future Holders of
this Security and other Securities issued upon the registration of transfer

                                      -8-
<PAGE>
 
hereof or in exchange herefor or in lieu hereof, whether or not notation of such
consent or waiver is made upon this Security.

     No reference herein to the indenture and no provision of this Security or
of the Indenture shall alter or impair the obligation of the Company, which is
absolute and unconditional (except as to the specific subordination provisions
contained in Article Seventeen of the Indenture), to pay the principal of,
premium, if any, interest and Additional Amounts, if any, on this Security at
the times, places and rates, and in the coin or currency, herein prescribed.

     No service charge shall be made for any registration of transfer or
exchange, but the Company may require payment of a sum sufficient to cover any
tax or other governmental charge payable in connection therewith.

     The Indenture and the Securities shall be governed by and construed in
accordance with the laws of the Commonwealth of Massachusetts applicable to
agreements made and to be performed entirely in such Commonwealth except that
the rights, protections, obligations, indemnities and immunities of the Trustee
under the Indenture and the Securities shall be governed by the laws of the
State of New York, without regard to the principles of conflicts of laws of
either state.

                                      -9-
<PAGE>
 
                                   GUARANTEE

     For value received, Thermo Electron Corporation, a corporation organized
under the laws of the State of Delaware (herein called the "Guarantor," which
                                                            ---------        
term includes any successor corporation under the Indenture referred to in the
Security upon which this Guarantee is endorsed), hereby unconditionally
guarantees to the Holder of the Security upon which this Guarantee is endorsed
and to the Trustee on behalf of the Trustee and such Holder the due and punctual
payment of the principal of, premium, if any, and interest and Additional
Amounts, if any, on such Security, any other amount due and payable pursuant to
the terms of the Indenture and the due and punctual payment of the sinking fund
or analogous payments referred to therein if any, when and as the same shall
become due and payable, whether at the Stated Maturity, by declaration of
acceleration, call for redemption, repayment at the option of the Holder or
otherwise, according to the terms thereof and of the Indenture.  In case of the
failure of Thermo Instrument Systems Inc., a corporation organized under the
laws of Delaware (herein called the "Company," which term includes any successor
                                     -------                                    
corporation under such Indenture), punctually to make any such payment of
principal, premium, if any, or interest or Additional Amounts, if any, the
Guarantor hereby agrees to cause any such payment to be made punctually when and
as the same shall become due and payable, whether at the Stated Maturity or by
declaration of acceleration, call for redemption, repayment at the option of the
Holder or otherwise, and as if such payment were made by the Company.

     The Guarantor hereby agrees that its obligations hereunder shall be as if
it were principal debtor and not merely surety, and shall be absolute and
unconditional (except as to the specific subordination provisions contained in
Article Eighteen of the Indenture), irrespective of, and shall be unaffected by,
any invalidity, subordination, irregularity or unenforceability of such Security
or such Indenture, any failure to enforce the provisions of such Security or
such Indenture, or any waiver, modification or indulgence granted to the Company
with respect thereto, by the Holder of such Security or the Trustee or any other
circumstance which may otherwise constitute a legal or equitable discharge of a
surety or guarantor.  The Guarantor hereby waives the benefits of diligence,
presentment, demand of payment, filing of claims with a court in the event of
merger, insolvency or bankruptcy of the Company, any right to require a
proceeding first against the Company, protest or notice with respect to such
Security or the indebtedness evidenced thereby and all demands whatsoever, and
covenants that this Guarantee will not be discharged except by strict and
complete performance of the obligations contained in such Security and this
Guarantee.  The Guarantor hereby agrees that, in the event of a default in
payment of principal of, premium, if any, and interest, and Additional Amounts,
if any, on such Security, or default in any sinking fund or analogous payment
referred to therein, legal proceedings may be instituted by the Trustee on
behalf of, or by, the Holder of such Security, on the terms and conditions set
forth in the Indenture, directly against the Guarantor to enforce this Guarantee
without first proceeding against the Company.

     The Guarantor shall be subrogated to all rights of the Holder of such
Security and the Trustee against the Company in respect of any amounts paid to
such Holder by the Guarantor on account of such Security pursuant to the
provisions of this Guarantee or the Indenture; provided, however, that the
                                               --------  -------          
Guarantor shall not be entitled to enforce, or to receive any payments arising

                                      -10-
<PAGE>
 
out of or based upon, such right of subrogation until the principal of, premium,
if any, and interest and Additional Amounts, if any, on all Securities issued
under such Indenture shall have been paid in full.

     Claims under this Guarantee are, to the extent provided in the Indenture,
subject in right of payment to the prior payment in full of all Senior Guarantor
Indebtedness, and this Guarantee is issued subject to the provisions of the
Indenture with respect thereto.  Each Holder of a Security upon which this
Guarantee is endorsed, by accepting the same, (a) agrees to and shall be bound
by such provisions, (b) authorizes and directs the Trustee on his behalf to take
such action as may be necessary or appropriate to effectuate the subordination
so provided and (c) appoints the Trustee his, her or its attorney-in-fact for
any and all such purposes.

     No reference herein to such Indenture and no provision of this Guarantee or
of such Indenture shall alter or impair the guarantee of the Guarantor, which is
absolute and unconditional (except as to the specific subordination provisions
contained in Article Eighteen of the Indenture), of the due and punctual payment
of principal, premium (if any), and interest and Additional Amounts, if any, on
the Security upon which this Guarantee is endorsed.

     This Guarantee shall not be valid or obligatory for any purpose until the
certificate of authentication of the Security upon which this Guarantee is
endorsed shall have been manually executed by or on behalf of the Trustee under
such Indenture.

     All terms used in this Guarantee which are defined in such Indenture shall
have the meanings assigned to them in such Indenture.

     This Guarantee shall be deemed to be a contract made under the laws of the
Commonwealth of Massachusetts, and for all purposes shall be governed by and
construed in accordance with the laws of the Commonwealth of Massachusetts.

     IN WITNESS WHEREOF, the Guarantor has caused this Guarantee to be duly
executed under its corporate seal and dated the date on the face hereof.

                                    THERMO ELECTRON CORPORATION


Attest:_______________________      By:________________________________


                                    Title: ____________________________

                                      -11-
<PAGE>
 
     This is one of the Securities of the series designated therein referred to
in the within-mentioned Indenture.

                                    BANKERS TRUST COMPANY,
                                    as Trustee



                                    By: ______________________________
                                        Authorized Officer

                                      -12-
<PAGE>
 
                               CONVERSION NOTICE


     The undersigned Holder of this Security hereby irrevocably exercises the
option to convert this Security, or any portion of the principal amount hereof
(which is an integral multiple of U.S. $1,000 below designated) into shares of
Common Stock in accordance with the terms of the Indenture referred to in this
Security and directs that such shares, together with a check in payment for any
fractional share and any Securities representing any unconverted principal
amount hereof, be delivered to the undersigned unless a different name has been
indicated below.  The address for payment of any such check must be outside the
United States.  If shares are to be registered in the name of a Person other
than the undersigned, the undersigned will pay all transfer taxes payable with
respect thereto.


Dated: __________________                        ______________________________
                                                 Signature

 
If shares are to be registered in the name of    HOLDER
and delivered to a Person other than the
Holder, please print such Person's name and      Please print name and address 
address:                                         of Holder 
 
 
 
_____________________________________          _________________________________
             Name                                         Name
 
_____________________________________          _________________________________
             Address                                      Address
 
_____________________________________          _________________________________
 
 
_____________________________________          _________________________________
 
 
_____________________________________          _________________________________
Social Security or other Taxpayer              Social Security or other Taxpayer
Identification Number, if any                  Identification Number, if any

                                      -13-
<PAGE>
 
 Name and address (outside the United    If only a portion of the Securities 
 States) to where any check referred     is to be converted, please indicate:
 to in the first paragraph of this 
 Conversion Notice should be mailed:     1.  Principal amount to be converted:  
                                             U.S.  $______________
______________________________________   2.  Principal amount and denomination
Name                                         of Bearer Securities representing 
                                             unconverted principal amount to 
                                             be issued:  
______________________________________       Amount:  U.S. $_________________
Address                                  Denominations:  U.S. $________________
                                         (any integral multiple of U.S. $1,000)
 

                                      -14-
<PAGE>
 
                           OPTION TO ELECT REPAYMENT
                             UPON A REPAYMENT EVENT


To:  Thermo Instrument Systems Inc.

     The undersigned owner of this Security hereby acknowledges receipt of a
notice from Thermo Instrument Systems Inc. (the "Company") as to the occurrence
of a Repayment Event with respect to the Common Stock of the Company and
requests and instructs the Company to repay the entire principal amount of this
Security, or the portion thereof (which is $1,000 or an integral multiple
thereof) below designated, in accordance with the terms of the Indenture
referred to in this Security at the Repayment Price (or the relevant percentage
thereof), together with accrued interest to such date (except if the Repayment
Date shall be an Interest Payment Date), to the holder hereof.


Dated: ________________________


                            ________________________________
                            Signature

                            Name: __________________________
                            Address:_________________________
                                    _________________________
                                Principal amount to be repaid
                            (if less than all):

                            $__________

 

_____________________________
Social Security or Other
Taxpayer Identification Number

                                      -15-

<PAGE>
 
                                                                     EXHIBIT 4.6




         ANY UNITED STATES PERSON WHO HOLDS THIS SECURITY WILL BE SUBJECT TO
LIMITATIONS UNDER THE UNITED STATES INCOME TAX LAWS, INCLUDING THE LIMITATIONS
PROVIDED IN SECTION 165(j) AND 1287(a) OF THE UNITED STATES INTERNAL REVENUE
CODE.

         THIS SECURITY IS A TEMPORARY GLOBAL SECURITY, WITHOUT COUPONS OR
CONVERSION RIGHTS, EXCHANGEABLE FOR DEFINITIVE BEARER SECURITIES WITH INTEREST
COUPONS OR REGISTERED SECURITIES WITHOUT INTEREST COUPONS. THE RIGHTS ATTACHING
TO THIS GLOBAL SECURITY, AND THE CONDITIONS AND PROCEDURES GOVERNING ITS
EXCHANGE FOR DEFINITIVE SECURITIES, ARE AS SPECIFIED IN THE INDENTURE (AS
DEFINED HEREIN).

         NEITHER THE HOLDER NOR THE BENEFICIAL OWNERS OF THIS GLOBAL SECURITY
SHALL BE ENTITLED TO RECEIVE PAYMENT OF INTEREST OR ANY PAYMENTS HEREON EXCEPT
PURSUANT TO THE PROVISIONS HEREOF.

                        THERMO INSTRUMENT SYSTEMS INC.
                    (Incorporated in the State of Delaware)


                4% CONVERTIBLE SUBORDINATED DEBENTURE DUE 2005
                     GUARANTEED ON A SUBORDINATED BASIS BY
                          THERMO ELECTRON CORPORATION
                    (Incorporated in the State of Delaware)

                       TEMPORARY GLOBAL BEARER DEBENTURE

         Thermo Instrument Systems Inc., a Delaware corporation (herein referred
to as the "Company", which term includes any successor corporation under the
Indenture referred to below), for value received, hereby promises to pay to
bearer upon presentation and surrender of this global Security the principal sum
of $____________ United States Dollars plus any premium, if any, on January 15,
2005 and to pay interest thereon from January 21, 1998 or from the most recent
Interest Payment Date to which interest has been paid or duly provided for,
semi-annually in arrears on January 15 and July 15 in each year, commencing July
15, 1998, at the rate of 4% per annum, and Additional Amounts, if any, until
the principal hereof is paid or duly provided for; provided, however, that
interest, Additional Amounts, if any, and any other payments on this global
Security shall be payable only after the issuance of the definitive Securities
for which this global Security is exchangeable and, in the case of definitive
Securities in bearer form, only upon presentation and surrender (at an Office or
Agency located outside the United States, except as otherwise provided in the
Indenture referred to below) of the appropriate Coupons appertaining thereto.

         This global Security is one of a duly authorized issue of Securities of
the Company designated as specified in the title hereof, issued and to be issued
in one or more series under the
<PAGE>
 
Indenture, dated as of January 15, 1998 (the "Indenture") by the Company and
Thermo Electron Corporation, as guarantor, to Bankers Trust Company, as Trustee
(the "Trustee", which term includes any successor Trustee under the Indenture).
This global Security is a temporary security and is exchangeable in whole or
from time to time in part without charge upon request of the Holder hereof for
definitive Securities in bearer form, with interest Coupons attached, commencing
on the date 40 days after the later of (i) the first closing date relating to
the sale of the Securities or (ii) the date of the closing relating to the sale
of the Securities acquired pursuant to the exercise of the over-allotment option
granted by the Company to the Underwriters, upon certification, in the forms set
forth as Exhibits D and E of the Indenture for such purpose, that the beneficial
owner or owners of this global Security (or, if such exchange is only for a part
of this global Security, of such part) are not United States persons or other
persons who have purchased such Security for resale to United States persons.
Definitive Securities in bearer form to be delivered in exchange for any part of
this global Security shall be delivered only outside of the United States. This
global Security will be exchangeable for definitive Securities in registered
form at any time without the certification requirements set forth above;
provided that such exchange is permitted by the rules and procedures then in
effect of Cedel and Euroclear, and provided, further, that if and so long as
Securities in registered form are represented solely by a permanent global
Security in registered form, this global Security will only be exchangeable for
an interest in the permanent global Security in registered form as set forth in
the Indenture.

         Until exchanged in full for definitive Securities, this global Security
shall in all respects be entitled to the same benefits under, and subject to the
same terms and conditions of, the Indenture as definitive Securities
authenticated and delivered thereunder, except that neither the Holder hereof
nor the beneficial owners of this global Security shall be entitled to receive
payment of interest or any other payments hereon, except as provided above, or
to convert this global Security into shares of Common Stock of the Company or
any other security, cash or other property.

         THIS GLOBAL SECURITY SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE
WITH THE LAWS OF THE COMMONWEALTH OF MASSACHUSETTS, UNITED STATES OF AMERICA,
EXCEPT THAT THE RIGHTS, PROTECTIONS, OBLIGATIONS, INDEMNITIES, AND IMMUNITIES OF
THE TRUSTEE UNDER THIS GLOBAL SECURITY AND THE INDENTURE SHALL BE GOVERNED BY
THE LAWS OF THE STATE OF NEW YORK, WITHOUT REGARD TO THE PRINCIPLES OF CONFLICTS
OF LAWS OF EITHER STATE.

         All terms used in this global Security which are defined in the
Indenture shall have the meanings assigned to them in the Indenture.

         Unless the certificate of authentication hereon has been manually
executed by an authorized signatory of the Trustee, this global Security shall
not be entitled to any benefit under the Indenture or valid or obligatory for
any purpose.

                                      -2-
<PAGE>
 
         IN WITNESS WHEREOF, the Company has caused this global Security to be
duly executed under its facsimile corporate seal.

Dated: January __, 1998
                                    THERMO INSTRUMENT SYSTEMS INC.
              

                                    By:
                                       -----------------------------------------
                                      Name:
                                      Title:
Attest:

- --------------------------
Secretary
[SEAL]

                                      -3-
<PAGE>
 
                         CERTIFICATE OF AUTHENTICATION

         This is one of the Securities of the series designated therein referred
to in the within-mentioned Indenture.

                                                 BANKERS TRUST COMPANY,
                                                   as Trustee


                                                 By:
                                                    -------------------------
                                                    Authorized Officer

                                      -4-
<PAGE>
 
                                   GUARANTEE

         For value received, Thermo Electron Corporation, a corporation
organized under the laws of the State of Delaware (herein called the
"Guarantor," which term includes any successor corporation under this Indenture
referred to in the Security upon which this Guarantee is endorsed), hereby
unconditionally guarantees to the Holder of the Security upon which this
Guarantee is endorsed and to the Trustee on behalf of the Trustee and such
Holder the due and punctual payment of the principal of, premium, if any, and
interest and Additional Amounts, if any, on such Security, any other amount due
and payable pursuant to the terms of the Indenture and the due and punctual
payment of the sinking fund or analogous payments referred to therein if any,
when and as the same shall become due and payable, whether at the Stated
Maturity, by declaration of acceleration, call for redemption, repayment at the
option of the Holder or otherwise, according to the terms thereof and of the
Indenture. In case of the failure of Thermo Instrument Systems Inc., a
corporation organized under the laws of Delaware (herein called the "Company,"
which term includes any successor corporation under such Indenture), punctually
to make any such payment of principal, premium, if any, or interest or
Additional Amounts, if any, the Guarantor hereby agrees to cause any such
payment to be made punctually when and as the same shall become due and payable,
whether at the Stated Maturity or by declaration of acceleration, call for
redemption, repayment at the option of the Holder or otherwise, and as if such
payment were made by the Company.

         The Guarantor hereby agrees that its obligations hereunder shall be as
if it were principal debtor and not merely surety, and shall be absolute and
unconditional (except as to the specific subordination provisions contained in
Article Eighteen of the Indenture), irrespective of, and shall be unaffected by,
any invalidity, subordination, irregularity or unenforceability of such Security
or such Indenture, any failure to enforce the provisions of such Security or
such Indenture, or any waiver, modification or indulgence granted to the Company
with respect thereto, by the Holder of such Security or the Trustee or any other
circumstance which may otherwise constitute a legal or equitable discharge of a
surety or guarantor. The Guarantor hereby waives the benefits of diligence,
presentment, demand of payment, filing of claims with a court in the event of
merger, insolvency or bankruptcy of the Company, any right to require a
proceeding first against the Company, protest or notice with respect to such
Security or the indebtedness evidenced thereby and all demands whatsoever, and
covenants that this Guarantee will not be discharged except by strict and
complete performance of the obligations contained in such Security and this
Guarantee. The Guarantor hereby agrees that, in the event of a default in
payment of principal of, premium, if any, and interest, and Additional Amounts,
if any, on such Security, or default in any sinking fund or analogous payment
referred to therein, legal proceedings may be instituted by the Trustee on
behalf of, or by, the Holder of such Security, on the terms and conditions set
forth in the Indenture, directly against the Guarantor to enforce this Guarantee
without first proceeding against the Company.

         The Guarantor shall be subrogated to all rights of the Holder of such
Security and the Trustee against the Company in respect of any amounts paid to
such Holder by the Guarantor on account of such Security pursuant to the
provisions of this Guarantee or the Indenture; provided, however, that the
                                               --------  -------
Guarantor shall not be entitled to enforce, or to receive any payments arising

                                      -5-
<PAGE>
 
out of or based upon, such right of subrogation until the principal of, premium,
if any, and interest and Additional Amounts, if any, on all Securities issued
under such Indenture shall have been paid in full.

         Claims under this Guarantee are, to the extent provided in the
Indenture, subject in right of payment to the prior payment in full of all
Senior Guarantor Indebtedness, and this Guarantee is issued subject to the
provisions of the Indenture with respect thereto. Each Holder of a Security upon
which this Guarantee is endorsed, by accepting the same, (a) agrees to and shall
be bound by such provisions, (b) authorizes and directs the Trustee on his
behalf to take such action as may be necessary or appropriate to effectuate the
subordination so provided and (c) appoints the Trustee his, her or its
attorney-in-fact for any and all such purposes.

         No reference herein to such Indenture and no provision of this
Guarantee or of such Indenture shall alter or impair the guarantee of the
Guarantor, which is absolute and unconditional (except as to the specific
subordination provisions contained in Article Eighteen of the Indenture), of the
due and punctual payment of principal, premium (if any), and interest and
Additional Amounts, if any, on the Security upon which this Guarantee is
endorsed.

         This Guarantee shall not be valid or obligatory for any purpose until
the certificate of authentication of the Security upon which this Guarantee is
endorsed shall have been manually executed by or on behalf of the Trustee under
such Indenture.

         All terms used in this Guarantee which are defined in such Indenture
shall have the meanings assigned to them in such Indenture.

         This Guarantee shall be deemed to be a contract made under the laws of
the Commonwealth of Massachusetts, and for all purposes shall be governed by and
construed in accordance with the laws of the Commonwealth of Massachusetts.

         IN WITNESS WHEREOF, the Guarantor has caused this Guarantee to be duly
executed under its corporate seal and dated the date on the face hereof.

                                            THERMO ELECTRON CORPORATION


Attest:______________________________       By: ________________________________

                                            Title: _____________________________

                                      -6-

<PAGE>
 
                                                                    EXHIBIT 12.1

                        THERMO INSTRUMENT SYSTEMS INC.

                      RATIO OF EARNINGS TO FIXED CHARGES
                            (DOLLARS IN THOUSANDS)

<TABLE> 
<CAPTION> 
                                                                                                            NINE
                                                                       FISCAL YEAR                         MONTHS
                                                     -------------------------------------------------      ENDED
                                                                                                          SEPT. 27,
                                                      1992       1993      1994       1995       1996       1997
                                                     -------   -------   --------   --------    -------   --------
<S>                                                  <C>       <C>       <C>        <C>         <C>       <C>   
Income from continuing operations before
  provision for income taxes........................  $54,429   $75,240   $ 95,768   $122,017   $184,478    $168,759
Add:
    Minority interest in consolidated subsidi-
     aries with fixed charges.......................      --        --         112      1,324      5,376       7,743
    Interest on indebtedness and amortization
     of debt expense................................   11,389    14,384     15,761     18,129     28,923      33,843
    Portion of rents representative of the
     interest factor/(1)/...........................    1,964     2,724      3,009      3,704      7,024       6,662
                                                      -------   -------   --------   --------   --------    --------
       Income, As Adjusted..........................  $67,782   $92,348   $114,650   $145,174   $225,801    $217,007  
                                                      =======   =======   ========   ========   ========    ========
Fixed Charges:
    Interest on indebtedness and amortization
     of debt expense................................  $11,389   $14,384   $ 15,761   $ 18,129   $ 28,923    $ 33,843
    Portion of rents representative of the
     interest factor/(1)/...........................    1,964     2,724      3,009      3,704      7,024       6,662
                                                      -------   -------   --------   --------   --------    --------
       Fixed Charges................................  $13,353   $17,108   $ 18,770   $ 21,833   $ 35,947    $ 40,505
                                                      =======   =======   ========   ========   ========    ========
Ratio of Earnings to Fixed Charges..................     5.08      5.40       6.11       6.65       6.28        5.36
                                                      =======   =======   ========   ========   ========    ========
</TABLE> 

______________
(1) Portion of rents representative of the interest factor is 1/3 of total 
    rents.

<PAGE>
 
                                                                    EXHIBIT 12.2

                          THERMO ELECTRON CORPORATION

                      RATIO OF EARNINGS TO FIXED CHARGES
                            (DOLLARS IN THOUSANDS)

<TABLE>
<CAPTION>
                                                                                                                       
                                                                                                                        NINE
                                                                                 FISCAL YEAR                           MONTHS
                                                       ------------------------------------------------------------    ENDED  
                                                                                                                      SEPT. 27,
                                                          1992       1993         1994         1995        1996         1997
                                                       --------    --------     --------     --------    --------     --------
<S>                                                    <C>         <C>          <C>          <C>         <C>         <C>
Income before provision for income taxes
  and cumulative effect of change in
  accounting principle...............................  $ 88,673    $110,381     $175,414     $238,293    $301,661     $288,448
Less:
     Minority interest in losses of
       consolidated subsidiaries.....................      (281)       (215)           -         (789)     (1,797)      (5,637)
Add:
     Minority interest in consolidated
       Subsidiaries with fixed charges...............    14,183      21,301       30,962       61,044      74,306       58,060
     Interest on indebteness and
       amortization of debt expense..................    24,322      31,736       59,844       77,861      96,695       67,794
     Portion of rents representative of the
       interest factor/(1)/..........................    15,208      15,621       15,806       16,251      20,856       17,559
                                                       ---------   --------     --------     --------    --------     --------
          Income, As Adjusted........................  $142,105    $178,824     $282,026     $392,660    $491,721     $426,224
                                                       =========   ========     ========     ========    ========     ========
Fixed Charges:
     Interest on indebtedness and
       amortization of debt expense..................  $ 24,322    $ 31,736     $ 59,844     $ 77,861    $ 96,695     $ 67,794
     Portion of rents representative of the
       interest factor/(1)/..........................    15,208      15,621       15,806       16,251      20,856       17,559
     Capitalized interest............................     7,100       8,400        2,114            -           -            -
                                                       --------    --------     --------     --------    --------     --------
          Fixed Charges..............................  $ 46,630    $ 55,757     $ 77,764     $ 94,112    $117,551     $ 85,353
                                                       ========    ========     ========     ========    ========     ========
Ratio of Earnings to Fixed Charges...................      3.05        3.21         3.63         4.17        4.18         4.99
                                                       ========    ========     ========     ========    ========     ========
</TABLE>

_____________
(1)  Portion of rents representative of the interest factor is 1/3 of total 
     rents.


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