SKYTEL COMMUNICATIONS INC
8-A12G, 1999-08-05
RADIOTELEPHONE COMMUNICATIONS
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                      SECURITIES AND EXCHANGE COMMISSION
                           WASHINGTON, D.C.  20549

                                   FORM 8-A

               FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES
                   PURSUANT TO SECTION 12(b) OR 12(g) OF THE
                        SECURITIES EXCHANGE ACT OF 1934

                          SkyTel Communications, Inc.
            (Exact Name of Registrant as Specified in Its Charter)

               Delaware                               64-0518209
(State of Incorporation or Organization)    (IRS Employer Identification No.)

        200 South Lamar Street
            Skytel Centre
         Jackson, Mississippi                            39201
(Address of Principal Executive Offices)               (Zip Code)


     If this form relates to the registration of a class of securities pursuant
to Section 12(b) of the Exchange Act and is effective pursuant to General
Instruction A.(c), check the following box. [ ]

     If this form relates to the registration of a class of securities pursuant
to Section 12(g) of the Exchange Act and is effective pursuant to General
Instruction A.(d) check the following box.  [X]

     Securities Act registration statement file number to which this form
relates:

     Securities to be registered pursuant to Section 12(b) of the Act:

          Title of Each Class        Name of Each Exchange on which
          to be so Registered        Each Class is to be Registered
          -------------------        ------------------------------

                               None


Securities to be registered pursuant to Section 12(g) of the Act:

           $2.25 Cumulative Convertible Exchangeable Preferred Stock
                                (Title of Class)

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Item 1.  Description of Registrant's Securities to be Registered.

     The following is a summary of the terms of the $2.25 Cumulative Convertible
Exchangeable Preferred Stock (the "Preferred Stock") of SkyTel Communications,
Inc. (formerly Mobile Telecommunications Technologies Corp.), a Delaware
corporation (the "Company"). This summary is not intended to be complete and is
subject to and qualified in its entirety by reference to the Certificate of
Designations of the Preferred Stock (the "Designations") filed with the
Secretary of State of the State of Delaware and setting forth the rights,
preferences and limitations of the Preferred Stock, a copy of which has been
filed as an exhibit to this registration statement.

     General.  The holders of shares of Preferred Stock have no preemptive
rights.  The Preferred Stock is not be subject to any sinking fund or other
obligation of the Company to redeem or retire the Preferred Stock.  Unless
converted or redeemed, the Preferred Stock has a perpetual maturity.  Any share
of Preferred Stock converted, redeemed or otherwise acquired by the Company will
be retired and canceled and will, upon cancellation be restored to the status of
authorized but unissued preferred stock, subject to reissuance by the Board of
Directors as Preferred Stock or as shares of preferred stock of any one or more
other series.

     Dividends.  Holders of the Preferred Stock are entitled to receive, when,
as and if declared by the Board of Directors, out of the funds of the Company
legally available therefor, a cash dividend at the annual rate of $2.25 per
share of Preferred Stock, payable in quarterly installments on January 15, April
15, July 15, and October 15, commencing January 15, 1994 (and, in the case of
any accrued but unpaid dividends, at such additional times and for such interim
periods, if any, as determined by the Board of Directors).  Dividends on the
Preferred Stock are cumulative and accrue without interest from the date of
original issuance, and are payable to holders of record as they appear on the
stock books of the Company on such record dates, which shall be not more than 60
days nor less than 10 days preceding the payment dates, as shall be fixed by the
Board of Directors, provided that holders of shares of Preferred Stock called
for redemption on a redemption date falling between a dividend payment record
date and the dividend payment date shall, in lieu of receiving such dividend on
the dividend payment date fixed therefor, receive such dividend payment together
with all other accrued and unpaid dividends on the date fixed for redemption
(unless such holders convert such shares in accordance with the Designations).
Dividends payable on the Preferred Stock for any period greater or less than a
full dividend period will be computed on the basis of a 360-day year consisting
of twelve 30-day months.

     If dividends are not paid in full upon the Preferred Stock and any other
preferred stock ranking on a parity as to dividends with the Preferred Stock,
all dividends declared upon shares of Preferred Stock and such other preferred
stock will be declared pro rata so that in all cases the amount of dividends
declared per share on the Preferred Stock and such other preferred stock bear to
each other the same ratio that accrued and unpaid dividends per share on the
shares of the Preferred Stock and such other preferred stock bear to each other.
Except as set forth above, unless full cumulative dividends on the Preferred
Stock have been paid and funds set aside, dividends (other than dividends paid
solely in shares of the Company's common stock, par value $.01 per share
("Common Stock"), other stock ranking junior as to dividends to the Preferred
Stock and rights to acquire the foregoing) may not be paid or declared and set
aside for payment and other distributions may not be made upon the Common Stock
or on any other stock of the Company ranking junior to or on a parity with the
Preferred Stock as to dividends nor may any Common Stock or any other stock of
the


                                 Page 2 of 14
<PAGE>

Company ranking junior to or on a parity with the Preferred Stock as to
dividends be redeemed, purchased or otherwise acquired for any consideration by
the Company (except for repurchases from employees and consultants and by
conversion into or exchange for stock of the Company ranking junior to the
Preferred Stock as to dividends).

     Conversion Rights.  Each share of Preferred Stock may be converted at any
time at the option of the holder into fully paid, non-assessable shares of
Common Stock.  The conversion price will be $45.00 per share of Common Stock;
provided, however, that such conversion price will be adjusted and readjusted
from time to time as provided in the Designations.  Except as may be provided by
the Board of Directors, upon conversion, the Company is not obligated to make
any payment or adjustment with respect to dividends accrued on the Preferred
Stock unless the holder of the shares of Preferred Stock being converted was the
record holder of such shares on the last record date for the payment of such
dividends.  Upon conversion of the Preferred Stock, the Company will make no
payment or adjustment whatsoever relating to dividends accrued on the Common
Stock issuable upon conversion.

     Upon surrender of certificates for shares of Preferred Stock to be
converted as required in the Designations, the Company will issue the number of
full shares of Common Stock issuable upon conversion thereof and cash for any
remaining fraction of a share of Common Stock in an amount equal to the Current
Market Price (as defined in the Designations) on the conversion date.

     The conversion price is subject to adjustment upon certain events,
including the subdivision or combination of the outstanding Common Stock, the
payment of a stock dividend to holders of Common Stock, or the issuance or sale
to all holders of Common Stock of any shares of Common Stock for a consideration
per share that is less than the Current Market Price immediately prior to such
issuance or sale (or deemed issuance or sale).  Issuances of options and
securities convertible into Common Stock are deemed to be issuances of the
underlying Common Stock for purposes of adjustments to the conversion price.
Whenever the conversion price is adjusted, the Company will promptly mail to
holders of Preferred Stock a notice of adjustment briefly stating the facts
requiring the adjustment and the manner of computing it.  No adjustment in the
conversion price need be made unless the adjustment would require an increase or
decrease of at least 1% in the conversion price; provided, however, that any
adjustments that are not made will be carried forward and taken into account in
any subsequent adjustment.  All calculations under the Designations will be made
either to the nearest cent or the nearest 1/100th of a share.

     In case of any consolidation or merger of the Company with any other
corporation (other than a wholly owned subsidiary of the Company), or in the
case of any sale or transfer of all or substantially all of the assets of the
Company, or in the case of any share exchange pursuant to which all of the
outstanding shares of Common Stock are converted into other securities or
property, the Company will make appropriate provision or cause appropriate
provision to be made so that holders of each share of Preferred Stock then
outstanding will have the right thereafter to convert such share of Preferred
Stock into the kind and amount of shares of stock and other securities and
property receivable upon such consolidation, merger, sale, transfer or share
exchange by a holder of the number of shares of Common Stock into which such
share of Preferred Stock might have been converted immediately prior to the
effective date of such

                                 Page 3 of 14
<PAGE>

consolidation, merger, sale, transfer or share exchange. If in connection with
any such consolidation, merger, sale, transfer or share exchange, each holder of
shares of Common Stock is entitled to elect to receive either securities, cash
or other assets upon completion of such transaction, the Company will provide or
cause to be provided to each holder of Preferred Stock the right to elect to
receive the securities, cash or other assets into which the Preferred Stock held
by such holder will be convertible after completion of any such transaction on
the same terms and subject to the same conditions applicable to holders of the
Common Stock (including, without limitation, notice of the right to elect,
limitations on the period in which such election will be made and the effect of
failing to exercise the election). The above will similarly apply to successive
consolidations, mergers, sales, transfers or share exchanges.

     The Company will reserve and at all times keep available, free from
preemptive rights, out of its authorized but unissued stock, for the purpose of
effecting the conversion of the Preferred Stock, such number of shares of its
duly authorized Common Stock as will from time to time be sufficient to effect
the conversion of all outstanding Preferred Stock.

     Liquidation Rights.  In the event of any liquidation, dissolution or
winding up of the Company, whether voluntary or involuntary, the holders of
shares of Preferred Stock are entitled to receive out of assets of the Company,
whether such assets are stated capital or surplus of any nature, before any
payment is made or any assets are distributed to holders of Common Stock and of
any other class of stock of the Company ranking junior to the Preferred Stock as
to a liquidation, dissolution or winding up, liquidating distributions in the
amount of $50.00 per share of Preferred Stock plus accrued and unpaid dividends,
whether or not declared, without interest. If upon any liquidation, dissolution
or winding up of the Company, the amounts payable with respect to the Preferred
Stock and any other preferred stock ranking as to any such distribution on a
parity with the Preferred Stock are not paid in full, the holders of the
Preferred Stock and of such other preferred stock will share ratably in any such
distribution of assets in proportion to the full respective preferential amounts
to which they are entitled.  After payment of the full amount of the liquidating
distribution to which they are entitled, the holders of shares of Preferred
Stock will not be entitled to any further participation in any distribution of
assets by the Company. Neither a consolidation or merger of the Company with
another corporation nor a sale or transfer of all or part of the Company's
assets for cash, securities or other property will be considered a liquidation,
dissolution or winding up of the Company for these purposes.

     Optional Redemption.  Shares of Preferred Stock were not redeemable prior
to October 25, 1996.  Shares of Preferred Stock are redeemable at the option of
the Company, in whole or in part, at any time out of funds legally available
therefor, on or after October 25, 1996, as specified in the Designations, on not
less than 30 nor more than 60 days notice to each holder of record of the shares
to be redeemed, by first-class mail at the per share redemption prices set forth
below during the period beginning on October 15 of the years shown below
(October 25 in the case of 1996), plus in each case an amount equal to accrued
and unpaid dividends, if any, to (and including) the redemption date, whether or
not earned or declared.

                                 Page 4 of 14
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<TABLE>
<CAPTION>

                            Redemption                           Redemption
  Year                      Per Share     Year                    Per Share
  ----                      ----------    -----                  -----------
  <S>                       <C>           <C>                    <C>
  1996...................     $51.50      2000.................     $50.50
  1997...................     $51.25      2001.................     $50.25
  1998...................     $51.00      2002 and thereafter..     $50.00
  1999...................     $50.75
</TABLE>

     If fewer than all of the shares of Preferred Stock are to be redeemed, the
shares to be redeemed shall be selected by lot or pro rata or by any other
equitable manner determined by the Board of Directors of the Company in its sole
discretion.  On and after the date fixed for redemption, provided that the
redemption price (including any accrued and unpaid dividends to and including
the date fixed for redemption) has been duly paid or provided for, dividends
shall cease to accrue on the Preferred Stock called for redemption, such shares
shall no longer be deemed to be outstanding and all rights of the holders of
such shares as stockholders of the Company shall cease, except the right to
receive the monies payable upon such redemption, without interest thereon, upon
surrender of the certificates evidencing such shares.

     Exchangeability.  The Preferred Stock is exchangeable in whole, but not in
part, at the option of the Company, for 4.5% Convertible Subordinated Debentures
due 2003 (the "Exchange Debentures") on any dividend payment date beginning
October 15, 1995 at the rate of $50.00 principal amount of Exchange Debentures
for each share of Preferred Stock outstanding at the time of exchange; provided
that the Exchange Debentures will be issuable initially in denominations of
$1,000 and integral multiples thereof.  If the exchange results in an amount of
Exchange Debentures that is not an integral multiple of $1,000, the amount in
excess of the closest integral multiple of $1,000 will be paid in cash by the
Company.  The Company will mail written notice of its intention to exchange to
each holder of record of the Preferred Stock not less than 30 nor more than 60
days prior to the date fixed for exchange.

     Upon the date fixed for exchange of Preferred Stock for Exchange Debentures
(the "Exchange Date"), if the Company has taken all action required to authorize
the issuance of the Exchange Debentures in exchange for the Preferred Stock, all
of the shares of Preferred Stock will no longer be deemed outstanding and all
rights relating to such shares will terminate, except only the right to receive
dividends accrued and unpaid to the date fixed for such redemption and the right
to receive the Exchange Debentures upon surrender of certificates representing
the Preferred Stock, the rights of holders of Preferred Stock as stockholders of
the Company shall cease (except the right to receive, accrued and unpaid
dividends to and including the Exchange Date) and their shares of Preferred
Stock no longer will be deemed outstanding and will represent only the right to
receive the Exchange Debentures and any accrued and unpaid dividends.  If all
dividends accrued and payable on the Preferred Stock have not been paid or
declared prior to the Exchange Date and funds have not been set aside to provide
for payment in full of the dividends, the Company may not exercise its option to
exchange the Preferred Stock for the Exchange Debentures.  In addition, the
exchange of the Preferred Stock for the Exchange Debentures is subject to
compliance at the time with any relevant covenants in the Company's then
existing bank loan agreements.  The exchange of Preferred Stock for Exchange
Debentures may be a

                                 Page 5 of 14
<PAGE>

taxable event and, therefore, may result in tax liability for the holder
exchanging such stock without any correlative cash payment to such holder.

     Voting Rights.  Except as indicated below or otherwise required by law,
holders of Preferred Stock will have no voting rights.  If at any time the
equivalent of six quarterly dividends payable on the Preferred Stock are accrued
and unpaid, the number of directors of the Company will be increased by two and
the holders of all outstanding shares of Preferred Stock and any stock ranking
on a parity as to dividends with the shares of Preferred Stock and having
similar voting rights then exercisable, voting separately as a class without
regard to series, will be entitled to elect the additional two directors to
serve until all dividends accumulated and unpaid have been paid or declared and
funds set aside to provide for payment in full.

     In addition, without the vote or consent of the holders of at least a
majority of shares of the Preferred Stock then outstanding, the Company may not
(a) create or issue or increase the authorized number of shares of any class or
series of stock ranking prior to the Preferred Stock either as to dividends or
upon liquidation, dissolution or winding up, or any security convertible into or
exercisable or exchangeable for such stock or (b) amend, alter or repeal any of
the provisions of the Certificate so as to affect adversely any right,
preference, privilege or voting power of the Preferred Stock or the holders
thereof; provided, however, that any increase in the amount of authorized
preferred stock or the creation and issuance of other series of Preferred stock,
or any increase in the amount of authorized shares of such series or of any
other series of preferred stock, in each case ranking on a parity with or junior
to the Preferred Stock with respect to the payment of dividends and the
distribution of assets upon liquidation, dissolution or winding up, will not be
deemed to affect adversely such rights, preferences or voting powers.

     Redemption at Option of Holder Upon a Fundamental Change.  If a Fundamental
Change (as defined below) occurs, each holder of Preferred Stock shall have the
right, at the holder's option, to require the Company to repurchase all of such
holder's Preferred Stock, or any portion thereof that has an aggregate
liquidation value that is a multiple of $50.00, on the date (the "Repurchase
Date") selected by the Company that is not less than ten nor more than 20 days
after the Final Surrender Date (as defined below), at a price per share equal to
$50.00, plus accrued and unpaid dividends to the Repurchase Date.  The Company
may, at its option, pay all or any portion of the repurchase price upon a
Fundamental Change in shares of Common Stock of the Company or any successor
corporation. For purposes of calculating the number of shares of Common Stock
issuable upon such redemption, the value of any such Common Stock will equal the
average of the closing prices of such Common Stock for the five trading days
ending on the third trading day immediately preceding the Repurchase Date.
Payment may not be made in shares of Common Stock unless such shares have been,
or will be no later than the Final Surrender Date (as defined below), registered
under the Securities Act or are freely tradeable pursuant to an exemption
thereunder and are listed on a United States national securities exchange or
quoted on the NASDAQ-NMS at the time of payment.

     Within 30 days after the occurrence of a Fundamental Change, the Company is
obligated to mail to all holders of record of the Preferred Stock a notice (the
"Company Notice") describing, among other things, the occurrence of such
Fundamental Change and of the repurchase right arising as a result thereof.  The
Company must cause a copy of such notice to be published in a daily newspaper of
national circulation (which shall be The Wall Street Journal if then in
circulation).  At least two business days prior to the Repurchase Date, the
Company must publish a similar notice stating whether and to what extent the
repurchase price will be paid in cash or shares of Common

                                 Page 6 of 14
<PAGE>

Stock. To exercise the repurchase right, a holder of Preferred Stock must
surrender, on or before the date which is, subject to any contrary requirements
of applicable law, 60 days after the date of mailing of the Company Notice (the
"Final Surrender Date"), the certificates representing the Preferred Stock with
respect to which the right is being exercised, duly endorsed for transfer to the
Company, together with a written notice of election.

     The term "Fundamental Change" shall mean either of the following:

          (a) a "person" or "group" (within the meaning of Sections 13(d) and
     14(d)(2) of the Exchange Act) becoming, in one transaction or a series of
     related transactions, the "beneficial owner" (as defined in Rule 13d-3
     under the Exchange Act) of Voting Shares (as defined below) of the Company
     entitled to exercise more than 50% of the total voting power of all
     outstanding Voting Shares of the Company (including any Voting Shares that
     are not then outstanding of which such person or group is deemed the
     beneficial owner); or

          (b) any consolidation of the Company with, or merger of the Company
     into, any other person, any merger of another person into the Company, or
     any sale, lease or transfer of all or substantially all of the assets of
     the Company to another person (other than a merger (i) which results in the
     holders of Common Stock of the Company immediately prior to giving effect
     to such transaction owning shares of capital stock of the surviving
     corporation in such transaction representing in excess of 40% of the total
     voting power of all shares of capital stock of such surviving corporation
     entitled to vote generally in the election of directors and (ii) in which
     the shares of the surviving corporation held by such holders are, or
     immediately upon issuance will be, listed on a national securities exchange
     or quoted on the NASDAQ-NMS and are not subject to any right of repurchase
     by the issuer thereof or any third party and are not otherwise subject to
     any encumbrance as a result of such transaction, provided, that the
     surviving corporation (x) amends its charter or certificate of
     incorporation to include the Preferred Stock and its terms as set forth in
     the Designations or (y) if the Preferred Stock has been exchanged for the
     Exchange Debentures, assumes or guarantees the Company's obligations under
     the Exchange Debentures);

provided, however, that a Fundamental Change shall not occur if either (i) for
any five trading days during the 10 trading days immediately preceding either
the public announcement by the Company of such transaction or the consummation
of such transaction, the last sale price of the Common Stock is equal to at
least 105% of the conversion price in effect on such trading days, or (ii) at
least 90% of the consideration (excluding cash payments for fractional shares)
in such transaction or transactions to the holders of Common Stock consists of
shares of common stock that are, or immediately upon issuance will be, listed on
a national securities exchange or quoted on the NASDAQ-NMS, and as a result of
such transaction or transactions, the Preferred Stock or Exchange Debentures, as
the case may be, become convertible into such common stock.  The Company will
not complete any Fundamental Change unless it makes proper provision to satisfy
its obligations under the Designations.

     For purposes of the foregoing, "Voting Shares" is defined to mean all
outstanding shares of any class or classes (however designated) of capital stock
entitled to vote generally in the election of members of the Board of Directors.

                                 Page 7 of 14
<PAGE>

The Exchange Debentures

     General.  If the Company elects to exchange the Preferred Stock for the
Exchange Debentures, the Company will issue the Exchange Debentures under an
Indenture (the "Indenture") to be entered into between the Company and a trustee
to be designated by the Company prior to such exchange and who would qualify at
the time of such designation as a trustee under the Trust Indenture Act of 1939,
as amended by the Trust Indenture Reform Act of 1990, as amended (together with
any successor trustee, the "Trustee"), at a rate of $50.00 principal amount of
Exchange Debentures for each share of Preferred Stock as exchanged.  The
following descriptions of certain provisions of the Indenture and the Exchange
Debentures are intended as summaries only and are qualified in their entirety by
reference to the Indenture and the Exchange Debentures, including the
definitions in those documents of certain terms.  Copies of the forms of
Indenture and Exchange Debentures have been filed as exhibits to this
registration statement.

     The Exchange Debentures will be general, unsecured, subordinated
obligations of the Company, limited to an aggregate principal amount equal to
the aggregate liquidation value of the Preferred Stock (excluding accrued and
unpaid dividends payable upon liquidation) and will mature on October 15, 2003.
The Exchange Debentures will be issued only in fully registered form, without
coupons, initially in denominations of $1,000 and any integral multiple of
$1,000.  No service charge will be made for any registration of transfer or
exchange of the Exchange Debentures, but the Company may require payment of a
sum sufficient to cover any tax or other governmental charge payable in
connection with any such transaction.

     Interest.  The Exchange Debentures will bear interest at the rate of 4.5%
per annum from the date of issuance, or from the most recent interest payment
date to which interest has been paid or provided for, payable semiannually on
April 15 and October 15 each year to the person in whose name the Exchange
Debenture (or any predecessor Debenture) is registered at the close of business
on the preceding April 1 and October 1, as the case may be.  Interest will be
computed on the basis of a 360-day year consisting of twelve 30-day months.
Principal of, premium, if any, and interest on the Exchange Debentures will be
payable, and the transfer of Exchange Debentures will be registrable, at the
principal office of the paying agent (who, initially, may be the Trustee).  In
addition, payment of interest may, at the option of the Company, be made by
check mailed to the address of the person entitled thereto as it appears in the
register of holders of Exchange Debentures.

     Conversion Rights.  The Exchange Debentures will be convertible into Common
Stock of the Company at the option of the holder at any time at the conversion
price then in effect (which shall be the conversion price of the Preferred Stock
set forth on the cover page of this Offering Memorandum, as subsequently
adjusted).  The right to convert Exchange Debentures called for redemption will
terminate at the close of business on the third business day preceding the date
fixed for redemption and will be lost if not exercised prior to that time.

     In case the Company shall be a party to any transaction (including, without
limitation, a merger; consolidation, sale, lease or transfer of all or
substantially all of its assets or reclassification of the Common Stock) as a
result of which shares of Common Stock shall be converted into the right to
receive stock, securities or other property (including cash or any combination
thereof), each Exchange Debenture shall thereafter be convertible into the kind
and amount of shares of stock and other securities and property receivable
(including cash) upon the consummation of such transaction by a holder of that
number of shares of Common Stock, or

                                 Page 8 of 14
<PAGE>

fraction thereof, into which an Exchange Debenture was convertible immediately
prior to such transaction.

     The conversion price is subject to adjustment upon certain events,
including the subdivision or combination of the outstanding Common Stock, the
payment of a stock dividend to holders of Common Stock or the issuance or sale
to all holders of Common Stock of any shares of Common Stock for a consideration
per share that is less than the current market price immediately prior to such
issuance or sale (or deemed issuance or sale).  Issuances of options and
securities convertible into Common Stock are deemed to be issuances of the
underlying Common Stock for purposes of adjustments to the conversion price.
Whenever the conversion price is adjusted, the Company will promptly mail to
holders of Exchange Debentures a notice of adjustment briefly stating the facts
requiring the adjustment and the manner of computing it.

     No adjustment of the conversion price will be required to be made in any
case until cumulative adjustments amount to a change in the conversion price of
1% or more, but any such adjustment that would otherwise be required to be made
shall be carried forward and taken into account in any subsequent adjustment.

     No fractional shares or securities representing fractional shares of Common
Stock will be issued upon conversion.  Any fractional shares resulting from
conversion will be paid in cash based on the current market price of the Common
Stock at the close of business on the first trading day preceding the date of
conversion.

     Holders of Exchange Debentures at the close of business on an interest
payment record date will be entitled to receive the interest payable on such
Exchange Debentures on the corresponding interest payment date notwithstanding
the conversion thereof or the Company's default on payment of the interest due
on such interest payment date.  However, Exchange Debentures surrendered for
conversion during the period from the close of business on any interest payment
record date to the opening of business on the corresponding interest payment
date (except Exchange Debentures called for redemption on a redemption date
during such period) must be accompanied by payment of an amount equal to the
interest payable on such Exchange Debentures on such interest payment date.  A
holder of Exchange Debentures on an interest payment record date who (or whose
transferee) converts Exchange Debentures on an interest payment date will
receive the interest payment on such Exchange Debentures by the Company on such
date, and the converting holder need not include payment in the amount of such
interest upon surrender of Exchange Debentures for conversion.  Except as
provided above, no payment or adjustment will be made on account of accrued
interest upon conversion of Exchange Debentures.

     Subordination. The payment of the principal of, premium, if any, and
interest on Exchange Debentures will, to the extent set forth in the Indenture,
be subordinated in right of payment to the prior payment in full of all Senior
Indebtedness (as defined below).  In the event and during the continuation of
any default in the payment of principal, interest or premium, if any, on any
Senior Indebtedness or an event of default with respect to any Senior
Indebtedness permitting the holders to accelerate the maturity thereof,
continuing beyond the period of grace, if any, specified in the instrument
evidencing such Senior Indebtedness, no payment with respect to the principal,
interest or premium, if any, on the Exchange Debentures may be made by the
Company unless and until such default has been cured or waived or shall have
ceased to exist.

                                 Page 9 of 14
<PAGE>

Upon any payment or distribution of assets to creditors upon any dissolution,
winding up, liquidation or reorganization of the Company, the holders of all
Senior Indebtedness will first be entitled to receive payment in full of all
amounts due or to become due thereon before the holders of the Exchange
Debentures will be entitled to receive any payment in respect of the principal
of or premium, if any, or interest on the Exchange Debentures.

     "Senior Indebtedness" with respect to the Exchange Debentures means (a) the
principal of and premium, if any, and interest (including, without limitation,
any interest accruing subsequent to the filing of a petition or other action
concerning bankruptcy or other similar proceedings, whether or not constituting
an allowed claim in any such proceedings) on the following, whether presently
outstanding or hereafter incurred or created: all indebtedness or obligations of
the Company (i) for money borrowed (other than that evidenced by the Exchange
Debentures), including intercompany loans and (ii) which is evidenced by a note,
bond, debenture or similar instrument (including a purchase money mortgage), (b)
all obligations constituting Bank Debt as defined in the Indenture; (c) all
obligations of the Company: (i) for the reimbursement of any obligor on any
letter of credit, banker's acceptance or similar credit transaction, (ii) under
interest rate swaps, caps, collars, options and similar arrangements, and (iii)
under any foreign exchange contract, currency swap agreement, futures contract,
currency option contract, or other foreign currency hedge; (d) all obligations
for the payment of money relating to a capitalized lease obligation; (e) any
liabilities of others described in the preceding clauses (a), (b), (c) and (d)
which the Company has guaranteed or which are otherwise its legal liability; and
(f) renewals, extensions, refundings, restructurings, amendments and
modifications of any such indebtedness or guarantee.  Notwithstanding anything
to the contrary in the Indenture or the Exchange Debentures,"Senior
Indebtedness" shall not include (a) any indebtedness represented by the
Company's 3.0% Convertible Subordinated Note due December 1, 1996, (b) any
indebtedness represented by the Company's 3.5% Convertible Subordinated
Debenture due October 15, 1999, (c) any indebtedness represented by the 6.75%
Debentures, (d) any indebtedness of the Company to a Subsidiary except to the
extent any such indebtedness is pledged by such Subsidiary as security for any
Bank Debt, (e) any indebtedness or guarantee of the Company which by its terms
or the terms of the instrument creating or evidencing it is not superior in
right of payment to the Exchange Debentures and (f) accounts payable or any
other indebtedness to trade creditors created or assumed by the Company in the
ordinary course of business, which shall rank pari passu with the Exchange
Debentures.  The Exchange Debentures will be structurally subordinated to
indebtedness of the Company's subsidiaries.

     Company's Right of Redemption.  If issued, the Exchange Debentures will be
redeemable, at the option of the Company at any time, in whole or in part, upon
not less than 30 or more than 60 days prior notice by first-class mail at the
following redemption prices (expressed as percentages of principal amount), plus
accrued interest, to the date fixed for redemption, if redeemed during the 12-
month period beginning October 15 of the year indicated:


                                 Page 10 of 14
<PAGE>

<TABLE>
<CAPTION>
                        Redemption                               Redemption
  Year                  Per Share         Year                   Per Share
  ----                  ----------        ----                   -----------
  <S>                  <C>               <C>                     <C>
  1996...............     103.0%          2000.................     101.0%
  1997...............     102.5%          2001.................     100.5%
  1998...............     102.0%          2002 and thereafter..     100.0%
  1999...............     101.5%
</TABLE>

     Redemption at Option of Holders Upon a Fundamental Change.  If a
Fundamental Change occurs, each holder of Exchange Debentures shall have the
right, at the holder's option, to require the Company to repurchase all of such
holder's Exchange Debentures, or any portion thereof that is an integral
multiple of $1,000, on the Repurchase Date, at a price equal to the principal
amount of the Exchange Debentures, plus accrued interest to the Repurchase Date.

     Within 30 days after the occurrence of a Fundamental Change, the Company is
obligated to mail to all holders of record of the Exchange Debentures the
Company Notice describing, among other things, the occurrence of such
Fundamental Change and of the repurchase right arising as a result thereof.  The
Company must deliver a copy of the Company Notice to the Trustee and cause a
copy of such notice to be published in a daily newspaper of national circulation
(which shall be The Wall Street Journal if then in circulation).  At least two
business days prior to the Repurchase Date, the Company must publish a similar
notice stating whether and to what extent the repurchase price will be paid in
cash or equivalent shares of Common Stock.   For purposes of calculating the
number of shares of Common Stock issuable upon such redemption, the value of any
such common stock will be equal to the average of the closing prices of such
Common Stock for the five trading days ending on the third trading day
immediately preceding the Repurchase Date.  Payment may not be made in shares of
Common Stock unless such shares have been, or will be no later than the Final
Surrender Date, registered under the Securities Act or are freely tradeable
pursuant to an exemption thereunder and are listed on a United States national
securities exchange or quoted on the NASDAQ-NMS at the time of payment.  To
exercise the repurchase right, a holder of Exchange Debentures must surrender,
on or before the Final Surrender Date, the Exchange Debentures with respect to
which the right is being exercised, duly endorsed for transfer to the Company,
together with a written notice of election.

     Events of Default.  The following will be Events of Default under the
Indenture: (a) failure to pay principal of or premium, if any, on the Exchange
Debentures when due at maturity, upon redemption or otherwise, including failure
by the Company to redeem the Exchange Debentures when required (whether or not
such payment shall be prohibited by the subordination provisions of the
Indenture); (b) failure to pay any interest on any Exchange Debentures when due,
continued for 30 days (whether or not such payment shall be prohibited by the
subordination provisions of the Indenture); (c) failure to perform any other
covenant or agreement of the Company in the Exchange Debentures or the
Indenture, continued for 30 days after written notice as provided in the
Indenture; (d) failure to pay when due any amounts payable with respect to any
indebtedness for money borrowed by the Company in excess of $10 million, and
such default has resulted in the acceleration of such indebtedness, which
acceleration is not


                                 Page 11 of 14
<PAGE>

withdrawn, canceled or annulled within 10 days after notice of it; and
(e) certain events in bankruptcy; insolvency or reorganization of the Company or
any subsidiary. Subject to the provisions of the Indenture relating to the
duties of the Trustee in case an Event of Default shall occur and be continuing,
the Trustee will be under no obligation to exercise any of its rights or powers
under the Indenture at the request or direction of any of the holders, unless
such holders shall have offered to the Trustee reasonable security or indemnity.
The holders of a majority in aggregate principal amount of the outstanding
Exchange Debentures will 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 to the Trustee (subject to certain exceptions).

     If an Event of Default (other than an Event of Default arising out of
certain events of bankruptcy, insolvency or reorganization) occurs and is
continuing, either the Trustee or the holders of at least 25% in aggregate
principal amount of the outstanding Exchange Debentures may accelerate the
maturity of all Exchange Debentures.  The maturity of the Exchange Debentures
automatically accelerates upon the occurrence of an Event of Default arising out
of certain events of bankruptcy, insolvency or reorganization.  After such
acceleration, but before a judgment or decree based on acceleration, the holders
of a majority in aggregate principal amount of outstanding Exchange Debentures
may, subject to certain conditions, rescind and annul the acceleration if all
Events of Default, other than the nonpayment of amounts which became due by
acceleration, have been cured or waived as provided in the Indenture.

     No holder of any Exchange Debenture will have any right to institute any
proceeding with respect to the Indenture or for any remedy under the Indenture
unless such holder previously has given to the Trustee written notice of a
continuing Event of Default and unless also the holders of at least 25% in
aggregate principal amount of the outstanding Exchange Debentures have made
written request, and offered reasonable indemnity to the Trustee to institute
proceedings as trustee, and the Trustee has not received from the holders of a
majority in aggregate principal amount of the outstanding Exchange Debentures a
direction inconsistent with the request and has failed to institute such
proceedings within 60 days.  However, these limitations do not apply to a suit
instituted by a holder of an Exchange Debenture for the enforcement of payment
of the principal of or premium, if any, or interest on such Exchange Debenture
on or after the respective due dates expressed in such Exchange Debenture or of
the right to convert the Exchange Debenture in accordance with the Indenture.

     The Company will be required to furnish to the Trustee annually a statement
of the performance by the Company of certain of its obligations under the
Indenture and as to any default in the performance of the obligations.

     The Indenture provides that the Trustee will, within 90 days after the
occurrence of default, mail to all holders notice of all defaults known to it,
but, except in the case of a default in the payment of the principal of or
premium, if any, or interest on any of the Exchange Debentures, the Trustee
shall be protected in withholding such notice if it in good faith determines
that the withholding of such notice is in the interests of such holders.

     The holders of a majority in aggregate principal amount of outstanding
Exchange Debentures may on behalf of the holders of all the Exchange Debentures
waive any past defaults, other than a default in payment of the principal of or
premium, if any, or interest on any

                                 Page 12 of 14
<PAGE>

Exchange Debenture or a failure by the Company to convert any Exchange
Debentures into Common Stock.

     Merger and Consolidation.  So long as the Exchange Debentures are
outstanding, the Company may not consolidate or merge with or into, or sell,
lease, convey or otherwise dispose of all or substantially all of its assets to,
another corporation, person or entity unless (a) the Company is the surviving
person or the successor or transferee is a corporation organized under the laws
of the United States, any state thereof or the District of Columbia; provided,
however, that the foregoing shall not be applicable in the event of a
transaction constituting a Fundamental Change, (b) the successor assumes all the
obligations of the Company under the Exchange Debentures and the Indenture (in
which case all obligations of the Company shall terminate), and (c) immediately
before, after giving effect to such transaction, no Event of Default exists.

     Modification.  Supplemental indentures modifying or amending the Indenture
may be made by the Company and the Trustee with the consent of the holders of a
majority in aggregate principal amount of the outstanding Exchange Debentures;
provided, however, that no such modification or amendment may, without the
consent of the holders of all the Exchange Debentures then outstanding, (a)
extend the stated maturity of any Exchange Debenture, reduce the rate or extend
the time of payment of interest on any Exchange Debenture, reduce the principal
amount on any Exchange Debenture or premium, if any, on any Exchange Debenture,
or impair the right of a holder to institute suit for payment thereof, change
the currency in which the Exchange Debentures are payable, impair the right to
convert the Exchange Debentures into stock, securities or other property or
assets (including cash) subject to the terms set forth in the Indenture, modify
the subordination provisions of the Indenture in a manner adverse to the holders
of Exchange Debentures or modify the provisions regarding repurchase of Exchange
Debentures upon a Fundamental Change, in each case without the consent of the
holders of each Exchange Debenture so affected, or (b) reduce the percentage of
Exchange Debentures, the consent of holders of which is required for any such
modification.

Item 2.  Exhibits.

     The following exhibits are filed as part of this registration statement on
Form 8-A. Where such filing is made by incorporation by reference to a
previously filed statement or report, such statement or report is identified in
parenthesis.  The securities to be registered are to be registered on the NASDAQ
National Market.  All exhibits required to be filed with the NASDAQ National
Market in accordance with the Instructions as to Exhibits on Form 8-A have been
duly filed with each copy of the Registration Statement filed with the NASDAQ
National Market.

Exhibit No.                         Description
- -----------                         -----------

4.1            Certificate of Designations of the $2.25 Cumulative Convertible
               Exchangeable Preferred Stock of the Company (Exhibit 4.1 to the
               Company's Quarterly Report on Form 10-Q for the quarter ended
               September 30, 1993)

4.2            Form of Indenture and Exchange Debenture  relating to the 4.5%
               Convertible Subordinated Debentures due 2003. (filed herewith)

                                 Page 13 of 14
<PAGE>

                                   SIGNATURES

     Pursuant to the requirements of Section 12 of the Securities Exchange Act
of 1934, the registrant has duly caused this registration statement to be signed
on its behalf by the undersigned, thereto duly authorized.

August 5, 1999
                                   SKYTEL COMMUNICATIONS, INC.


                                   By: /s/ Leonard G. Kriss
                                       -------------------------------
                                       Name:   Leonard G. Kriss
                                       Title:  Senior Vice President,
                                               General Counsel and Secretary

                                 Page 14 of 14

<PAGE>

            _______________________________________________________

                  MOBILE TELECOMMUNICATION TECHNOLOGIES CORP.


                                      AND


                           ________________________
                                    Trustee



                                _______________


                                   Indenture

                            Dated as of __________

                                 ____________



                   4.5% Convertible Subordinated Debentures
                                   due 2003


            _______________________________________________________
<PAGE>

                               TABLE OF CONTENTS

                                                                  Page


                                   ARTICLE 1

                   DEFINITIONS AND INCORPORATION BY REFERENCE

SECTION 1.1.    Definitions........................................  1
SECTION 1.2.    Other Definitions..................................  5
SECTION 1.3.    Incorporation by Reference of Trust Indenture Act..  5
SECTION 1.4.    Rules of Construction..............................  6

                                   ARTICLE 2

                                 THE DEBENTURES

SECTION 2.1.    Form and Dating....................................  7
SECTION 2.2.    Execution and Authentication.......................  8
SECTION 2.3.    Registrar, Paying Agent anal Conversion Agent......  8
SECTION 2.4.    Paying Agent to Hold Money in Trust................  9
SECTION 2.5.    Debentureholder Lists..............................  9
SECTION 2.6.    Transfer and Exchange..............................  9
SECTION 2.7.    Replacement Debentures............................. 10
SECTION 2.8.    Outstanding Debentures............................. 10
SECTION 2.9.    Treasury Debentures................................ 10
SECTION 2.10.   Temporary Debentures............................... 11
SECTION 2.11.   Cancellation....................................... 11
SECTION 2.12.   Defaulted Interest................................. 11

                                   ARTICLE 3

                                   REDEMPTION


SECTION 3.1.    Notice to Trustee.................................. 12
SECTION 3.2.    Selection of Debentures to be Redeemed............. 12
SECTION 3.3.    Notice of Redemption............................... 12
SECTION 3.4.    Effect of Notice of Redemption..................... 13
SECTION 3.5.    Deposit of Redemption Price........................ 13
SECTION 3.6.    Debentures Redeemed in Part........................ 13

                                   ARTICLE 4

                                   CONVERSION

SECTION 4.1.    Conversion Privilege............................... 14
SECTION 4.2.    Conversion Procedure............................... 14

                                      -i-
<PAGE>

SECTION 4.3.    Fractional Shares.................................. 15
SECTION 4.4.    Taxes on Conversion................................ 15
SECTION 4.5.    Company to Provide Stock........................... 15
SECTION 4.6.    Adjustment of Conversion Price..................... 15
SECTION 4.7.    No Adjustment...................................... 18
SECTION 4.8.    Equivalent Adjustments............................. 18
SECTION 4.9.    Adjustments for Tax Purposes....................... 19
SECTION 4.10.   Notice of Adjustment............................... 19
SECTION 4.11.   Notice of Certain Transactions..................... 19
SECTION 4.12.   Effect of Reclassifications, Consolidations,
                Mergers or Sales on Conversion Privilege........... 19
SECTION 4.13.   Trustee's Disclaimer............................... 20
SECTION 4.14.   Voluntary Reduction................................ 21

                                   ARTICLE 5

                                 SUBORDINATION


SECTION 5.1.    Debentures Subordinated to Senior Indebtedness..... 21
SECTION 5.2.    Debentures Subordinated to Prior Payment of All
                Senior Indebtedness on Dissolution, Liquidation,
                Reorganization, etc. of the Company................ 21
SECTION 5.3.    Debentureholders to be Subrogated to Right of
                Holders of Senior Indebtedness..................... 23
SECTION 5.4.    Obligations of the Company Unconditional........... 23
SECTION 5.5.    Company Not to Make Payment with Respect to the
                Debentures in Certain Circumstances................ 24
SECTION 5.6.    Trustee Entitled to Assume Payments Not Prohibited
                in Absence of Notice............................... 25
SECTION 5.7.    Application by Trustee of Monies Deposited with It. 25
SECTION 5.8.    Subordination Rights Not Impaired by Acts or
                Omissions of Company or Holders of Senior
                Indebtedness....................................... 26
SECTION 5.9.    Debentureholders Authorize Trustee to Effectuate
                Subordination of Debentures........................ 26
SECTION 5.10.   Right of Trustee to Hold Senior Indebtedness....... 27
SECTION 5.11.   Article 5 Not to Prevent Events of Default......... 27
SECTION 5.12.   No Fiduciary Duty Created to Holders of Senior
                Indebtedness....................................... 27

                                   ARTICLE 6

                                   COVENANTS

SECTION 6.1.    Payment of Debentures.............................. 28
SECTION 6.2.    SEC Reports........................................ 28
SECTION 6.3.    Waiver of Usury Defense............................ 28
SECTION 6.4.    Liquidation........................................ 29
SECTION 6.5.    Compliance Certificates............................ 29
SECTION 6.6.    Notice of Defaults................................. 30

                                      -ii-
<PAGE>

SECTION 6.7.    Payment of Taxes and Other Claims..................  30
SECTION 6.8.    Corporate Existence................................  30
SECTION 6.9.    Maintenance of Properties..........................  30
SECTION 6.10.   Purchase of the Debentures at Option of the
                Holder Upon Fundamental Change.....................  31
SECTION 6.11.   Effect of Fundamental Change Purchase Notice.......  34
SECTION 6.12.   Deposit of Fundamental Change Purchase Price.......  35
SECTION 6.13.   Debentures Purchased in Part.......................  35
SECTION 6.14.   Compliance with Securities Laws upon Purchase
                of any Debentures..................................  35
SECTION 6.15.   Repayment to the Company...........................  36
SECTION 6.16.   No Amendments to Section 6.05(d) of the Bank Credit
                Agreement..........................................  36
SECTION 6.17.   144A Resale........................................  36

                                   ARTICLE 7

                             SUCCESSOR CORPORATION

SECTION 7.1.    When Company May Merge, etc........................  36
SECTION 7.2.    Successor Corporation Substituted..................  37

                                   ARTICLE 8

                              DEFAULT AND REMEDIES


SECTION 8.1.    Events of Default..................................  37
SECTION 8.2.    Acceleration.......................................  39
SECTION 8.3.    Other Remedies.....................................  40
SECTION 8.4.    Waiver of Defaults and Events of Default...........  40
SECTION 8.5.    Control by Majority................................  40
SECTION 8.6.    Limitation on Suits................................  40
SECTION 8.7.    Rights of Holders to Receive Payment...............  41
SECTION 8.8.    Collection Suit by Trustee.........................  41
SECTION 8.9.    Trustee May File Proofs of Claim...................  41
SECTION 8.10.   Priorities.........................................  42
SECTION 8.11.   Undertaking for Costs..............................  42

                                   ARTICLE 9

                                    TRUSTEE


SECTION 9.1.    Duties of Trustee..................................  43
SECTION 9.2.    Rights of Trustee..................................  44
SECTION 9.3.    Individual Rights of Trustee.......................  44
SECTION 9.4.    Trustee's Disclaimer...............................  44
SECTION 9.5.    Notice of Default or Events of Default.............  44
SECTION 9.6.    Reports by Trustee to Holders......................  45

                                     -iii-
<PAGE>

SECTION 9.7.    Compensation and Indemnity.........................  45
SECTION 9.8.    Replacement of Trustee.............................  46
SECTION 9.9.    Successor Trustee by Merger, etc...................  47
SECTION 9.11.   Preferential Collection of Claims Against Company..  47

                                   ARTICLE 10

                    SATISFACTION AND DISCHARGE OF INDENTURE

SECTION 10.1.   Termination of Company's Obligations...............  48
SECTION 10.2.   Application of Trust Money.........................  48
SECTION 10.3.   Repayment to Company...............................  49
SECTION 10.4.   Reinstatement......................................  49

                                   ARTICLE 11

                      AMENDMENTS, SUPPLEMENTS AND WAIVERS

SECTION 11.1.   Without Consent of Holders.........................  50
SECTION 11.2.   With Consent of Holders............................  50
SECTION 11.3.   Compliance with Trust Indenture Act................  51
SECTION 11.4.   Revocation and Effect of Consents..................  51
SECTION 11.5.   Notation On or Exchange of Debentures..............  51
SECTION 11.6.   Trustee to Sign Amendments, etc....................  52

                                   ARTICLE 12

                                 MISCELLANEOUS

SECTION 12.1.   Trust Indenture Act Controls.......................  53
SECTION 12.2.   Notices............................................  53
SECTION 12.3.   Communications by Holders with Other Holders.......  53
SECTION 12.4.   Certificate and Opinion as to Conditions Precedent.  54
SECTION 12.5.   Record Date for Vote or Consent of
                Debentureholders...................................  54
SECTION 12.6.   Rules by Trustee, Paying Agent, Registrar..........  55
SECTION 12.7.   Legal Holidays.....................................  55
SECTION 12.8.   Governing Law......................................  55
SECTION 12.9.   No Adverse Interpretation of Other Agreements......  55
SECTION 12.10.  No Recourse Against Others.........................  55
SECTION 12.11.  Successors.........................................  55
SECTION 12.12.  Multiple Counterparts..............................  55
SECTION 12.13.  Separability.......................................  56
SECTION 12.14.  Table of Contents, Headings, etc...................  56

                                      -iv-
<PAGE>

                             CROSS-REFERENCE TABLE


                                                                  Indenture
TIA Section                                                        Section
- -----------                                                       ---------

(S) 310    (a)(1)......................................................9.10
           (a)(2)......................................................9.10
           (a)(3)......................................................N.A.
           (a)(4)......................................................N.A.
           (a)(5)......................................................9.10
           (b)....................................................9.8; 9.10
           (c).........................................................N.A.
(S) 311    (a).........................................................9.11
           (b).........................................................9.11
           (c).........................................................N.A.
(S) 312    (a)..........................................................2.5
           (b).........................................................12.3
           (c).........................................................12.3
(S) 313    (a)..........................................................9.6
           (b)(1)......................................................N.A.
           (b)(2).......................................................9.6
           (c)....................................................9.6; 12.2
           (d)..........................................................9.6
(S) 314    (a)...............................................6.2; 6.5; 12.3
           (b).........................................................N.A.
           (c)(1)...................................................12.4(a)
           (c)(2)...................................................12.4(a)
           (c)(3)......................................................N.A.
           (d).........................................................N.A.
           (e)......................................................12.4(b)
           (f).........................................................N.A.
(S) 315    (a).......................................................9.1(b)
           (b)................................................... 9.5; 12.2
           (c).......................................................9.1(a)
           (d).......................................................9.1(c)
           (e).........................................................8.11
(S) 316    (a)(last sentence)...........................................2.9
           (a)(1)(A)....................................................8.5
           (a)(1)(B)....................................................8.4
           (a)(2)......................................................N.A.
           (b)..........................................................8.7
           (c).........................................................12.5

                                       i
<PAGE>

(S) 317    (a)(1).......................................................8.8
           (a)(2).......................................................8.9
           (b)..........................................................2.4
(S) 318    (a).........................................................12.1


_______________
N.A. means Not Applicable
Note: This Cross-Reference Table shall not, for any purpose, be deemed to be a
part of this Indenture.



                                      ii
<PAGE>

          INDENTURE dated as of ______________________ between MOBILE
TELECOMMUNICATION TECHNOLOGIES CORP., a Delaware corporation (the "Company"),
and ____________________, as Trustee (the "Trustee").

          Both parties agree as follows for the benefit of the other and for the
equal and ratable benefit of the registered holders of the Company's 4.5%
Convertible Subordinated Debentures due 2003.


                                   ARTICLE 1

                   DEFINITIONS AND INCORPORATION BY REFERENCE

 SECTION 1.1   Definitions.
               -----------

          "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 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.

          "Agent" means any Registrar, Paying Agent or Conversion Agent.

          "Associate" shall have the meaning ascribed to such term in Rule 12b-2
of the General Rules and Regulations under the Exchange Act, as such Rule is in
effect on the date of this Indenture.

          "Bank Credit Agreement" means the Credit, Guaranty and Debenture
Agreement dated as of December 11, 1990, as amended, among SkyTel Corp., the
Company, the Subsidiaries of the Company referred to therein, the Lenders
referred to therein and Chemical Bank and Credit Lyonnais New York Branch as co-
agents for the lenders, as in effect on the date hereof and as the same may be
further amended, supplemented or replaced from time to time.

          "Bank Debt" means any and all amounts payable under or in respect of
the Bank Credit Agreement or any related agreement, including principal, premium
(if any), interest (including, without limitation, any interest accruing
subsequent to the filing of a petition or other action concerning bankruptcy or
other similar proceeding, whether or not constituting an allowed claim in any
such proceedings), fees, charges, expenses, reimbursement obligations,
guarantees and all other amounts payable thereunder or in respect thereof.

          "Board of Directors" means the Board of Directors of the Company or
any authorized committee of the Board of Directors.

          "Business Day" means a day that is not a Legal Holiday.
<PAGE>

          "Capitalized Lease Obligation" means indebtedness represented by
obligations under a lease that is required to be capitalized for financial
reporting purposes in accordance with generally accepted accounting principles
and the amount of such indebtedness shall be the capitalized amount of such
obligations determined in accordance with such principles.

          "Common Stock" means the common stock of the Company as it exists on
the date of this Indenture or as it may be constituted from time to time.

          "Company" means the party named as such in this Indenture until a
successor replaces it pursuant to this Indenture and thereafter means the
successor.

          "Debentures" means the 4.5 % Convertible Subordinated Debentures due
2003 of the Company.

          "default" means any event which is, or after notice or passage of
time, or both, would be, an Event of Default.

          "Designated Senior Indebtedness" means (i) the Bank Debt and (ii) any
other Senior Indebtedness issued or incurred in a single transaction in which
such Senior Indebtedness has an aggregate principal amount then outstanding of
$10,000,000 or more.

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

          "Holder" or "Debentureholder" means the person in whose name a
Debenture is registered on the Registrar's books.

          "Indenture" means this Indenture as amended or supplemented from time
to time.

          "Initial Purchasers" means Alex. Brown & Sons Incorporated, Bear,
Stearns & Co. Inc. and Morgan Keegan & Company, Inc.

          "NASDAQ National Market System" means the National Market System of
the National Association of Securities Dealers, Inc. Automated Quotation System.

          "Offering Memorandum" means the Offering Memorandum of the Company
dated October 12, 1993, relating to the offering of the Preferred Stock by the
Initial Purchasers.

          "Officer" means the Chairman of the Board, the President, any Vice
President, the Chief Financial Officer, the Treasurer, the Secretary or the
Controller of the Company.

          "Officers' Certificate" means a certificate signed by two Officers or
by an Officer and an Assistant Treasurer or Assistant Secretary of the Company;
provided, however, that for purposes of Section 6.5 "Officers' Certificate"
means a certificate signed by the principal executive officer, principal
financial officer or principal accounting officer of the Company.

          "Opinion of Counsel" means a written opinion from outside legal
counsel who is acceptable to the Trustee.

                                       2
<PAGE>

          "Over-Allotment Option" means the option to purchase up to 562,500
additional shares of Preferred Stock granted by the Company to the Initial
Purchasers pursuant to the Placement Agreement.

          "person" means any individual, corporation, partnership, joint
venture, association, joint-stock company, trust, unincorporated organization or
government or other agency or political subdivision thereof.

          "Placement Agreement" means the Placement Agreement dated October 12,
1993 between the Company and Alex. Brown & Sons Incorporated, Bear, Stearns &
Co. Inc. and Morgan Keegan & Company, Inc., as Initial Purchasers of the
Preferred Stock.

          "Preferred Stock" means the 3,750,000 shares of $2.25 Cumulative
Convertible Exchangeable Preferred Stock of the Company (plus up to 562,500
additional shares to cover over-allotment(s)) sold to the Initial Purchasers
pursuant to the Placement Agreement as more fully described in the Offering
Memorandum.

          "principal" of a debt security, including the Debentures, means the
principal of the security plus, when appropriate, the premium, if any, on the
security.

          "redemption date," when used with respect to any Debenture to be
redeemed, means the date fixed for such redemption pursuant to this Indenture,
as set forth in the form of Debenture annexed as Exhibit A hereto.

          "redemption price," when used with respect to any Debenture to be
redeemed, means the price fixed for such redemption pursuant to this Indenture,
as set forth in the form of Debenture annexed as Exhibit A hereto.

          "SEC" or "Commission" means the Securities and Exchange Commission.

          "Senior Indebtedness" means (a) the principal of and premium, if any,
and interest (including, without limitation, any interest accruing subsequent to
the filing of a petition or other action concerning bankruptcy or other similar
proceedings, whether or not constituting an allowed claim in any such
proceedings) on the following, whether presently outstanding or hereafter
incurred or created: all indebtedness or obligations of the Company (i) for
money borrowed (other than that evidenced by the Debentures), including
intercompany loans made by SkyTel Corp. to the Company, and (ii) which is
evidenced by a note, bond, debenture or similar instrument (including a purchase
money mortgage); (b) all obligations constituting Bank Debt; (c) all obligations
of the Company (i) for the reimbursement of any obligor on any letter of credit,
banker's acceptance or similar credit transaction, (ii) under interest rate
swaps, caps, collars, options and similar arrangements and (iii) under any
foreign exchange contract, currency swap agreement, futures contract, currency
option contract, or other foreign currency hedge; (d) all obligations for the
payment of money relating to a Capitalized Lease Obligation; (e) any liabilities
of others described in the preceding clauses (a), (b), (c) and (d) which the
Company has guaranteed or which are otherwise its legal liability; and (f)
renewals, extensions, refundings, restructurings, amendments and modifications
of any such indebtedness or guarantee.

                                       3
<PAGE>

Notwithstanding anything to the contrary in this Indenture or the Debentures,
"Senior Indebtedness" shall not include (a) any indebtedness represented by the
Company's 3.0% Convertible Subordinated Note due December 1, 1996, (b) any
indebtedness represented by the Company's 3.5 % Convertible Subordinated
Debenture due October 15, 1999, (c) any indebtedness represented by the
Company's 6.75% Convertible Subordinated Debentures due 2002, (d) any
indebtedness of the Company to a Subsidiary except to the extent any such
indebtedness is pledged by such Subsidiary as security for any Bank Debt, (e)
any indebtedness or guarantee of the Company which by its terms or the terms of
the instrument creating or evidencing it is not superior in right of payment to
the Debentures and (f) accounts payable or any other indebtedness to trade
creditors created or assumed by the Company in the ordinary course of business,
each of which shall rank pari passu with the Debentures.
                         ---- -----

          "Subsidiary" means any corporation of which at least a majority of the
outstanding capital stock having voting power under ordinary circumstances to
elect directors of such corporation shall at the time be held, directly or
indirectly, by the Company, by the Company and one or more Subsidiaries or by
one or more Subsidiaries.

          "TIA" means the Trust Indenture Act of 1939, as amended by the Trust
Indenture Reform Act of 1990 and as in effect on the date of this Indenture,
except as provided in Section 11.3 hereof, and except to the extent any
amendment to the Trust Indenture Act expressly provides for application of the
Trust Indenture Act as in effect on another date.

          "trading day" means any day on which the New York Stock Exchange is
open for trading.

          "Trustee" means the party named as such in this Indenture until a
successor replaces it in accordance with the provisions of this Indenture and
thereafter means the successor.

          "Trust Officer" means any officer within the Corporate Trust
Department (or any successor group) of the Trustee, including without limitation
any Vice President, Assistant Vice President, any trust officer, any Assistant
Secretary or any other officer customarily performing functions similar to those
performed by any of the above-designated officers who shall, in any case, be
responsible for the administration of this Indenture or have familiarity with
it, and also means, with respect to a particular corporate matter, any other
officer of the Trustee to whom corporate trust matters are referred because of
his knowledge of and familiarity with the particular subject.










                                       4
<PAGE>

 SECTION 1.2   Other Definitions.
               -----------------

<TABLE>
<CAPTION>
                                                                    Defined in
Term                                                                 Section
- -----                                                               ----------
<S>                                                                 <C>
"Bankruptcy Law"................................................       8.1

"Conversion Agent"..............................................       2.3

"Custodian".....................................................       8.1

"Event of Default"..............................................       8.1

"Final Surrender Date"..........................................       6.10

"Fundamental Change"............................................       6.10

"Fundamental Change Purchase Date"..............................       6.10

"Fundamental Change Purchase Notice"............................       6.10

"Fundamental Change Purchase Price".............................       6.10

"Legal Holiday".................................................      12.7

"Paying Agent"..................................................       2.3

"Registrar".....................................................       2.3

"U.S. Government Obligations"...................................      10.1

"Voting Shares".................................................       6.10
</TABLE>

SECTION 1.3    Incorporation by Reference of Trust Indenture Act.
               --------------------------------------------------

          Whenever this Indenture refers to a provision of the TIA, the
provision is incorporated by reference in and made a part of this Indenture.
The following TIA terms used in this Indenture have the following meanings:

          "Commission" means the SEC.

          "indenture securities" means the Debentures.

          "indenture security holder" means a Debentureholder.

          "indenture to be qualified" means this Indenture.

          "indenture trustee" or "institutional trustee" means the Trustee.

                                       5
<PAGE>

          "obligor" on the indenture securities means the Company or any other
obligor on the Debentures.

          All other terms used in this Indenture that are defined in the TIA,
defined by TIA reference to another statute or defined by SEC rule and not
otherwise defined herein have the meanings assigned to them therein.

SECTION 1.4    Rules of Construction.
               ---------------------

          Unless the context otherwise requires:

          (1)  a term has the meaning assigned to it;

          (2)  an accounting term not otherwise defined has the meaning assigned
     to it in accordance with generally accepted accounting principles in effect
     on the date hereof, and any other reference in this Indenture to "generally
     accepted accounting principles" refers to generally accepted accounting
     principles in effect on the date hereof;

          (3)  "or" is not exclusive;

          (4)  words in the singular include the plural, and words in the plural
     include the singular;

          (5)  provisions apply to successive events and transactions; and

          (6)  "herein", "hereof" and other words of similar import refer to
this Indenture as a whole and not to any particular Article, Section or other
subdivision.









                                       6
<PAGE>

                                   ARTICLE 2

                                 THE DEBENTURES

SECTION 2.1   Form and Dating.
              ---------------

          (a)  The Debentures and the Trustee's certificate of authentication
shall be substantially in the form of Exhibit A, which is incorporated in and
made part of this Indenture. The Debentures may have notations, legends or
endorsements required by law, stock exchange rule, agreements to which the
Company is subject or usage.  The Company shall approve the form of the
Debentures and any notation, legend or endorsement on them.  Each Debenture
shall be dated the date of its authentication.

          (b)  Each certificate evidencing the Debentures and all securities
issued in exchange therefor or substitution thereof (including shares of Common
Stock issued upon conversion of any Debenture unless such Common Stock is issued
pursuant to an effective registration statement covering the issuance of such
shares) shall bear a legend in substantially the following form:

     "THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933,
     AS AMENDED (THE "SECURITIES ACT").  THE HOLDER HEREOF, BY PURCHASING THIS
     SECURITY, AGREES FOR THE BENEFIT OF MOBILE TELECOMMUNICATION TECHNOLOGIES
     CORP.  (THE "COMPANY") THAT THIS SECURITY MAY BE RESOLD, PLEDGED OR
     OTHERWISE TRANSFERRED ONLY (1) TO THE COMPANY (UPON CONVERSION, EXCHANGE OR
     REDEMPTION THEREOF OR OTHERWISE), (2) SO LONG AS THIS SECURITY IS ELIGIBLE
     FOR RESALE PURSUANT TO RULE 144A UNDER THE SECURITIES ACT ("RULE 144A"), TO
     A PERSON WHOM THE SELLER REASONABLY BELIEVES IS A QUALIFIED INSTITUTIONAL
     BUYER WITHIN THE MEANING OF RULE 144A, PURCHASING FOR ITS OWN ACCOUNT OR
     FOR THE ACCOUNT OF A QUALIFIED INSTITUTIONAL BUYER TO WHOM NOTICE IS GIVEN
     THAT THE RESALE, PLEDGE OR OTHER TRANSFER IS BEING MADE IN RELIANCE ON RULE
     144A, (3) IN AN OFFSHORE TRANSACTION IN ACCORDANCE WITH REGULATION S UNDER
     THE SECURITIES ACT, BUT ONLY IN THE CASE OF A TRANSFER THAT IS EFFECTED BY
     THE DELIVERY TO THE TRANSFEREE OF DEFINITIVE SECURITIES REGISTERED IN ITS
     NAME (OR ITS NOMINEE'S NAME) ON THE BOOKS MAINTAINED BY THE REGISTRAR, (4)
     PURSUANT TO AN EXEMPTION FROM REGISTRATION IN ACCORDANCE WITH RULE 144 (IF
     AVAILABLE) UNDER SECURITIES ACT, OR (5) PURSUANT TO AN EFFECTIVE
     REGISTRATION STATEMENT UNDER THE SECURITIES ACT, IN EACH CASE IN ACCORDANCE
     WITH ANY APPLICABLE SECURITIES LAWS OF ANY STATE OF THE UNITED STATES."

          (c)  The Trustee shall be entitled (but not obligated) to require such
additional certificates and Opinions of Counsel as it may reasonably deem
necessary to demonstrate that any sale or other transfer of a Debenture or other
restricted security is made in compliance with the applicable restrictions set
forth above.

                                       7
<PAGE>

SECTION 2.2   Execution and Authentication.
              ----------------------------

          Two Officers shall sign the Debentures for the Company by manual or
facsimile signature.  The Company's seal shall be reproduced on the Debentures.

          If an Officer whose signature is on a Debenture no longer holds that
office at the time the Trustee authenticates the Debenture, the Debenture shall
be valid nevertheless.

          A Debenture shall not be valid until an authorized signatory of the
Trustee manually signs the certificate of authentication on the Debenture.  The
signature shall be conclusive evidence that the Debenture has been authenticated
under this Indenture.

          The Trustee shall authenticate the Debentures for original issue in
the aggregate principal amount equal to (i) the number of shares of Preferred
Stock so exchanged, (ii) multiplied by $50 per share, upon a written order or
orders of the Company signed by two Officers or by an Officer and an Assistant
Treasurer or Assistant Secretary of the Company (a "Company Order").  The
Company Order shall specify the amount of the Debentures to be authenticated and
the date on which the original issue of the Debentures is to be authenticated.
The aggregate principal amount of the Debentures outstanding at any time may not
exceed $187,500,000 except as provided in Section 2.7.

          The Trustee shall act as the initial authenticating agent.
Thereafter, the Trustee may appoint an authenticating agent acceptable to the
Company to authenticate the Debentures. An authenticating agent may authenticate
the Debentures whenever the Trustee may do so.  Each reference in this Indenture
to authentication by the Trustee includes authentication by such agent. An
authenticating agent has the same rights as an Agent to deal with the Company or
an Affiliate of the Company.

          The Debentures shall be initially issuable only in registered form
without coupons and only in denominations of $1,000 and any integral multiple
thereof.

SECTION 2.3   Registrar, Paying Agent anal Conversion Agent.
              ---------------------------------------------

          The Company shall maintain an office or agency where the Debentures
may be presented for registration of transfer or for exchange ("Registrar"), an
office or agency where the Debentures may be presented for payment ("Paying
Agent"), an office or agency where the Debentures may be presented for
conversion ("Conversion Agent") and an office or agency where notices and
demands to or upon the Company in respect of the Debentures and this Indenture
may be served.  The Registrar shall keep a register of the Debentures and of
their transfer and exchange.  The Company may have one or more co-Registrars,
one or more additional Paying Agents and one or more additional Conversion
Agents.  The term "Registrar" includes any co-Registrar, the term "Paying Agent"
includes any additional Paying Agent and the term "Conversion Agent" includes
any additional Conversion Agent.  Except for purposes of Section 6.4 and
Article 10, the Company or any Affiliate of the Company may act as Paying Agent.

          The Company shall enter into an appropriate agency agreement with any
Agent not a party to this Indenture.  The agreement shall implement the
provisions of this Indenture that

                                       8
<PAGE>

relate to such Agent.  The Company shall notify the Trustee of the name and
address of any Agent not a party to this Indenture.  If the Company fails to
maintain a Registrar, Paying Agent, Conversion Agent or agent for service of
notices and demands, or fails to give the foregoing notice, the Trustee shall
act as such.

          The Company initially appoints the Trustee as Registrar, Paying Agent,
Conversion Agent and agent for service of notices and demands.

SECTION 2.4   Paying Agent to Hold Money in Trust.
              -----------------------------------

          On or prior to each due date of the principal of or interest on any of
the Debentures, the Company shall deposit with the Paying Agent a sum sufficient
to pay such principal or interest so becoming due.  Subject to Section 5.7, the
Paying Agent shall hold in trust for the benefit of the Debentureholders or the
Trustee all money held by the Paying Agent for the payment of principal of or
interest on the Debentures, and shall notify the Trustee of any default by the
Company (or any other obligor on the Debentures) in making any such payment. If
the Company or an Affiliate of the Company acts as Paying Agent, it shall on or
before each due date of the principal of or interest on any of the Debentures
segregate the money and hold it as a separate trust fund.  The Company at any
time may require a Paying Agent to pay all money held by it to the Trustee and
the Trustee may at any time during the continuance of any default, upon written
request to a Paying Agent, require such Paying Agent to forthwith pay to the
Trustee all sums so held in trust by such Paying Agent.  Upon doing so, the
Paying Agent (other than the Company) shall have no further liability for the
money.

SECTION 2.5   Debentureholder Lists.
              ---------------------

          The Trustee shall preserve in as current a form as is reasonably
practicable the most recent list available to it of the names and addresses of
the Debentureholders.  If the Trustee is not the Registrar, the Company shall
furnish to the Trustee on or before each semi-annual interest payment date and
at such other times as the Trustee may request in writing a list in such form
and as of such date as the Trustee may reasonably require of the names and
addresses of the Debentureholders.

SECTION 2.6   Transfer and Exchange.
              ---------------------

          When a Debenture is presented to the Registrar with a request to
register a transfer thereof, the Registrar shall register the transfer as
requested and when the Debentures are presented to the Registrar with a request
to exchange them for an equal principal amount of the Debentures of other
authorized denominations, the Registrar shall make the exchange as requested;
provided that every Debenture presented or surrendered for registration of
transfer or exchange shall be duly endorsed or be accompanied by a written
instrument of transfer in form satisfactory to the Company and the Registrar
duly executed by the Holder thereof or his attorney duly authorized in writing.
To permit registration of transfers and exchanges, the Company shall execute and
the Trustee shall authenticate the Debentures at the Registrar's request.  Any
exchange or transfer shall be without charge, except that the Company may
require payment of a sum sufficient to cover any tax or other governmental
charge that may be imposed in relation thereto, but this provision shall not
apply to any exchange pursuant to Section 2.10, 3.6, 6.13 or 11.5.

                                       9
<PAGE>

SECTION 2.7   Replacement Debentures.
              ----------------------

          If a mutilated Debenture is surrendered to the Trustee, or if the
Holder of a Debenture claims that the Debenture has been lost, destroyed or
wrongfully taken, and neither the Company nor the Trustee has received notice
that such Debenture has been acquired by a bona fide purchaser, the Company
shall issue and the Trustee shall authenticate a replacement Debenture if the
requirements of Section 8-405 of the New York Uniform Commercial Code, as then
in effect, are met, and there shall have been delivered to the Company and the
Trustee evidence to their satisfaction of the loss, destruction or theft of any
Debenture if such is the case. An indemnity bond may be required that is
sufficient in the judgment of the Company and the Trustee to protect the
Company, the Trustee or any Agent from any loss which any of them may suffer if
a Debenture is replaced.  The Company may charge for its expenses in replacing a
Debenture.  Every replacement Debenture is an additional obligation of the
Company.

SECTION 2.8   Outstanding Debentures.
              ----------------------

          The Debentures outstanding at any time are all of the Debentures
authenticated by the Trustee, except for those canceled by it, those delivered
to it for cancellation and those described in this Section 2.8 as not
outstanding.

          If a Debenture is replaced pursuant to Section 2.7, it ceases to be
outstanding unless the Trustee receives proof satisfactory to it that the
replaced Debenture is held by a bona fide purchaser.

          If the Paying Agent (other than the Company or an Affiliate of the
Company) holds on a redemption date or maturity date money sufficient to pay the
principal of and accrued interest on the Debentures payable on that date, then
on and after that date such Debentures cease to be outstanding and interest on
them ceases to accrue.

          Subject to the restrictions contained in Section 2.9, a Debenture does
not cease to be outstanding because the Company or an Affiliate of the Company
holds the Debenture.

SECTION 2.9   Treasury Debentures.
              -------------------

          In determining whether the Holders of the required principal amount of
the Debentures have concurred in any notice, direction, waiver or consent, the
Debentures owned by the Company or any other obligor on the Debentures or by any
Affiliate of the Company or of such other obligor shall be disregarded, except
that for purposes of determining whether the Trustee shall be protected in
relying on any such notice, direction, waiver or consent, only the Debentures
which the Trustee knows are so owned shall be so disregarded.  The Debentures so
owned which have been pledged in good faith shall not be disregarded if the
pledgee establishes to the satisfaction of the Trustee the pledgee's right so to
act with respect to the Debentures and that the pledgee is not the Company or
any other obligor upon the Debentures or any Affiliate of the Company or of such
other obligor.

                                       10
<PAGE>

SECTION 2.10  Temporary Debentures.
              --------------------

          Until definitive Debentures are ready for delivery, the Company may
prepare and, upon the order of the Company, the Trustee shall authenticate and
deliver temporary Debentures. Temporary Debentures shall be substantially in the
form of definitive Debentures but may have variations that the Company with the
consent of the Trustee considers appropriate for temporary Debentures.  Without
unreasonable delay, the Company shall prepare and the Trustee shall authenticate
and deliver definitive Debentures in exchange for temporary Debentures.


SECTION 2.11  Cancellation.
              ------------

          The Company at any time may deliver Debentures to the Trustee for
cancellation. The Registrar, the Paying Agent and the Conversion Agent shall
forward to the Trustee any Debentures surrendered to them for transfer,
exchange, payment or conversion.  The Trustee and no one else shall cancel all
Debentures surrendered for transfer, exchange, payment (including redemption),
conversion or cancellation and shall dispose of cancelled Debentures as the
Company shall direct.  The Company may not issue new Debentures to replace
Debentures it has paid or delivered to the Trustee for cancellation or which
have been converted.

SECTION 2.12  Defaulted Interest.
              ------------------

          If the Company defaults in a payment of interest on the Debentures, it
shall pay the defaulted interest to the persons who are Debentureholders on a
subsequent special record date, and such term as used in this Section 2.12 with
respect to the payment of any defaulted interest, shall mean the 15th day next
preceding the special payment date fixed by the Company, whether or not such day
is a Business Day.  At least 15 days before the special record date, the Company
shall mail to each Debentureholder and the Trustee a notice that states the
special record date, the special payment date and the amount of defaulted
interest to be paid.


















                                       11
<PAGE>

                                   ARTICLE 3

                                   REDEMPTION

SECTION 3.1   Notice to Trustee.
              -----------------

          If the Company wants to redeem the Debentures pursuant to paragraph 5
of the Debentures, it shall notify the Trustee at least 60 days prior to the
redemption date as fixed by the Company (unless a shorter notice shall be
satisfactory to the Trustee) of the redemption date and the principal amount of
the Debentures to be redeemed.

SECTION 3.2   Selection of Debentures to be Redeemed.
              --------------------------------------

          If less than all of the Debentures are to be redeemed, the Trustee
shall, not more than 60 days prior to the redemption date, select the Debentures
to be redeemed pro rata or by lot, as the Trustee in its discretion shall
determine.  The Trustee shall make the selection from the Debentures outstanding
and not previously called for redemption.  The Debentures in denominations of
$1,000 may only be redeemed in whole.  The Trustee may select for redemption
portions (equal to $1,000 or any multiple thereof) of the principal of the
Debentures that have denominations larger than $1,000.  Provisions of this
Indenture that apply to Debentures called for redemption also apply to portions
of the Debentures called for redemption.

SECTION 3.3   Notice of Redemption.
              --------------------

          At least 30 days but not more than 60 days before a redemption date,
the Company shall mall a notice of redemption by first class mail to each Holder
of the Debentures to be redeemed.

          The notice shall identify the Debentures to be redeemed and shall
state:

          (1)  the redemption date;

          (2)  the redemption price;

          (3)  the then current conversion price;

          (4)  the name and address of the Paying Agent and the Conversion
     Agent;

          (5)  that the Debentures called for redemption must be surrendered to
     the Paying Agent to collect the redemption price;

          (6)  that the right to convert Debentures called for redemption shall
     terminate at the close of business on the third Business Day immediately
     preceding the redemption date;

          (7)  that Holders who wish to convert the Debentures must satisfy the
     requirements in paragraph 9 of the Debentures;

                                       12
<PAGE>

          (8)  that, unless the Company defaults in making the redemption
     payment, interest on the Debentures called for redemption ceases to accrue
     on and after the redemption date and the only remaining right of the Holder
     is to receive payment of the redemption price upon surrender to the Paying
     Agent of the Debentures; and

          (9)  if any Debenture is being redeemed in part, the portion of the
     principal amount of such Debenture to be redeemed and that, after the
     redemption date, upon surrender of such Debenture, a new Debenture or
     Debentures in principal amount equal to the unredeemed portion thereof will
     be issued.

          At the Company's request, the Trustee shall give the notice of
redemption in the Company's name and at the Company's expense.

SECTION 3.4   Effect of Notice of Redemption.
              ------------------------------

          Once notice of redemption is mailed, the Debentures called for
redemption become due and payable on the redemption date, subject to the
provisions of Section 4.1, and at the redemption price.  Upon surrender to the
Paying Agent, such Debentures shall be paid at the redemption price, plus
accrued interest to the redemption date.

SECTION 3.5   Deposit of Redemption Price.
              ---------------------------

          On or prior to the redemption date, the Company shall deposit with the
Paying Agent (or if the Company is its own Paying Agent, shall segregate and
hold in trust) money sufficient to pay the redemption price of and accrued
interest on all Debentures to be redeemed on that date, other than the
Debentures or portions thereof called for redemption on that date which have
been delivered by the Company to the Trustee for cancellation.  The Paying Agent
shall return to the Company any money not required for that purpose because of
the conversion of the Debentures or otherwise.

SECTION 3.6   Debentures Redeemed in Part.
              ---------------------------

          Upon surrender of a Debenture that is redeemed in part, the Company
shall issue and the Trustee shall authenticate for and deliver to the Holder a
new Debenture equal in principal amount to the unredeemed portion of the
Debenture surrendered.








                                       13
<PAGE>

                                   ARTICLE 4

                                   CONVERSION

SECTION 4.1   Conversion Privilege.
              --------------------

          A Holder of a Debenture may convert it into Common Stock of the
Company at any time prior to maturity at the conversion price then in effect,
except that, with respect to any Debenture called for redemption, such
conversion right shall terminate at the close of business on the third Business
Day immediately preceding the redemption date (unless the Company shall default
in making the redemption payment then due, in which case the conversion right
shall terminate on the date such default is cured).  The number of shares of
Common Stock issuable upon conversion of a Debenture is determined by dividing
the principal amount converted by the conversion price in effect on the
conversion date.

          The initial conversion price is stated in paragraph 8 of the
Debentures and is subject to adjustment as provided in this Article 4.

          A Holder may convert a portion of a Debenture equal to $1,000 or any
integral multiple thereof.  Provisions of this Indenture that apply to
conversion of all of a Debenture also apply to conversion of a portion of it.

SECTION 4.2   Conversion Procedure.
              --------------------

          To convert a Debenture, a Holder must satisfy the requirements in
paragraph 8 of the Debentures.  The date on which the Holder satisfies all of
those requirements is the conversion date.  As soon as practicable after the
conversion date, the Company shall deliver to the Holder through the Conversion
Agent a certificate for the number of whole shares of Common Stock issuable upon
the conversion and a check for any fractional share.  The person in whose name
the certificate is registered shall become the stockholder of record on the
conversion date and, as of such date, such person's rights as a Debentureholder
shall cease.

          Holders of the Debentures at the close of business on an interest
payment record date will be entitled to receive the interest payable on such
Debentures on the corresponding interest payment date notwithstanding the
conversion thereof or the Company's default on payment of the interest due on
such interest payment date.  However, the Debentures surrendered for conversion
during the period from the close of business on any interest payment record date
to the opening of business on the corresponding interest payment date (except
Debentures called for redemption on a redemption date during such period) must
be accompanied by payment of an amount equal to the interest payable on such
Debentures on such interest payment date.  Any Holder of the Debentures on an
interest payment record date who (or whose transferee) converts the Debentures
on an interest payment date will receive the interest payment on such Debentures
by the Company on such date, and the converting holder need not include payment
in the amount of such interest upon surrender of the Debentures for conversion.
Except as provided above, no payment or adjustment will be made on account of
accrued interest upon conversion of the Debentures.

                                       14
<PAGE>

          If a Holder converts more than one Debenture at the same time, the
number of whole shares issuable upon the conversion shall be based on the total
principal amount of the Debentures converted.

          Upon surrender of a Debenture that is converted in part, the Trustee
shall authenticate for the Holder a new Debenture equal in principal amount to
the unconverted portion of the Debenture surrendered.

SECTION 4.3   Fractional Shares.
              -----------------

          The Company will not issue fractional shares of Common Stock upon
conversion of the Debentures.  In lieu thereof, the Company will pay an amount
in cash based upon the current market price of the Common Stock on the trading
day prior to the date of conversion, determined as provided in Section 4.6(d).

SECTION 4.4   Taxes on Conversion.
              -------------------

          The issuance of certificates for shares of Common Stock upon the
conversion of any Debenture shall be made without a service charge to the
converting Debentureholder for such certificates, but the holder will be
required to pay any tax or governmental charge in respect of such transaction,
and such certificates shall be issued in the respective names of, or in such
names as may be directed by, the Holder or Holders of the Debenture converted;
provided, however, that in the event that certificates for shares of Common
Stock are to be issued in a name other than the name of the Holder of the
Debenture converted, such Debenture, when surrendered for conversion, shall be
accompanied by an instrument of transfer, in form satisfactory to the Company,
duly executed by the registered Holder thereof or his duly authorized attorney;
and provided further, however, that the Company shall not be required to pay any
tax which may be payable in respect of any transfer involved in the issuance and
delivery of any such certificates in a name other than that of the Holder of the
Debenture converted, and the Company shall not be required to issue or deliver
such certificates unless or until the person or persons requesting the issuance
thereof shall have paid to the Company the amount of such tax or shall have
established to the satisfaction of the Company that such tax has been paid or is
not applicable.

SECTION 4.5   Company to Provide Stock.
              ------------------------

          The Company shall at all times reserve and keep available, free from
preemptive rights, out of its authorized but unissued Common Stock, solely for
the purpose of issuance upon conversion of the Debentures as herein provided, a
sufficient number of shares of Common Stock to permit the conversion of all
outstanding Debentures.

          All shares of Common Stock which may be issued upon conversion of the
Debentures shall be duly authorized, validly issued, fully paid and non-
assessable when so issued.

                                       15
<PAGE>

SECTION 4.6   Adjustment of Conversion Price.
              ------------------------------

          The conversion price (herein called the "Conversion Price") shall be
subject to adjustment from time to time as follows:

          (a)  In case the Company shall (1) pay a dividend in shares of Common
     Stock to holders of Common Stock, (2) make a distribution in shares of
     Common Stock to holders of Common Stock, (3) split or otherwise subdivide
     its outstanding shares of Common Stock into a greater number of shares of
     Common Stock or (4) combine its outstanding shares of Common Stock into a
     smaller number of shares of Common Stock, the Conversion Price in effect
     immediately prior to such action shall be adjusted so that the Holder of
     any Debenture thereafter surrendered for conversion shall be entitled to
     receive the number of shares of Common Stock which he would have owned
     immediately following such action had such Debentures been converted
     immediately prior thereto.  An adjustment made pursuant to this subsection
     (a) shall become effective immediately after the record date in the case of
     a dividend or distribution and shall become effective immediately after the
     effective date in the case of a subdivision or combination.

          (b)  In case the Company shall issue rights, options or warrants to
     all or substantially all holders of Common Stock entitling them (for a
     period commencing no earlier than the record date for the determination of
     holders of Common Stock entitled to receive such rights, options or
     warrants and expiring not more than 45 days after such record date) to
     subscribe for or purchase shares of Common Stock (or securities convertible
     into or exchangeable for Common Stock) at a price per share less than the
     current market price (as determined pursuant to subsection (d) below) of
     the Common Stock on such record date, 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 such record date by a
     fraction of which the numerator shall be the number of shares of Common
     Stock outstanding on such record date, plus the number of shares of Common
     Stock which the aggregate offering price of the offered shares of Common
     Stock (or the aggregate conversion price of the convertible securities so
     offered) would purchase at such current market price, and of which the
     denominator shall be the number of shares of Common Stock outstanding on
     such record date plus the number of additional shares of Common Stock
     offered (or into which the convertible securities so offered are
     convertible). Such adjustments shall become effective immediately after
     such record date. If at the end of the period during which such warrants or
     rights are exercisable not all warrants or rights shall have been
     exercised, the adjusted conversion price shall be immediately readjusted to
     what it would have been based on the number of additional shares of Common
     Stock actually issued (or the number of shares of Common Stock issuable
     upon conversion of convertible securities actually issued).

          (c)  In case the Company shall distribute to all holders of Common
     Stock shares of any class of stock other than Common Stock, evidences of
     indebtedness or other assets (other than dividends or cash distributions
     payable out of consolidated net income or retained earnings), or shall
     distribute to all or substantially all holders of Common Stock rights or
     warrants to subscribe for securities (other than those referred to in
     subsection (b) above), then in each such case 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 date of such
     distribution by a fraction of which the numerator shall be the current
     market price (determined as provided in subsection (d)

                                       16
<PAGE>

     below) of the Common Stock on the record date mentioned below less the then
     fair market value (as determined by the Board of Directors, whose
     determination shall be conclusive evidence of such fair market value) of
     the portion of the assets so distributed or of such subscription rights or
     warrants applicable to one share of Common Stock, and of which the
     denominator shall be such current market price of the Common Stock. Such
     adjustment shall become effective immediately after the record date for the
     determination of the holders of Common Stock entitled to receive such
     distribution. Notwithstanding the foregoing, in the event that the Company
     shall distribute rights or warrants (other than those referred to in
     subsection (b) above) ("Rights") pro rata to holders of Common Stock, the
     Company may, in lieu of making any adjustment pursuant to this Section 4.6,
     make proper provision so that each holder of a Debenture who converts such
     Debenture (or any portion thereof) after the record date for such
     distribution and prior to the expiration or redemption of the Rights shall
     be entitled to receive upon such conversion, in addition to the shares of
     Common Stock issuable upon such conversion (the "Conversion Shares"), a
     number of Rights to be determined as follows: (i) if such conversion occurs
     on or prior to the date for the distribution to the holders of Rights of
     separate certificates evidencing such Rights (the "Distribution Date"), the
     same number of Rights to which a holder of a number of shares of Common
     Stock equal to the number of Conversion Shares is entitled at the time of
     such conversion in accordance with the terms and provisions of and
     applicable to the Rights; and (ii) if such conversion occurs after the
     Distribution Date, the same number of Rights to which a holder of the
     number of shares of Common Stock into which the principal amount of the
     Debenture so converted was convertible immediately prior to the
     Distribution Date would have been entitled on the Distribution Date in
     accordance with the terms and provisions of and applicable to the Rights.

          (d)  The current market price per share of Common Stock on any date
     shall be deemed to be the average of the daily closing prices for thirty
     consecutive trading days commencing 45 trading days before the day in
     question.  The closing price for each day shall be the last reported sales
     price regular way or, in case no such reported sale takes place on such
     date, the average of the reported closing bid and asked prices regular way,
     in either case on the New York Stock Exchange Composite Tape, or if the
     Common Stock is not listed or admitted to trading on such Exchange, on the
     principal national securities exchange on which the Common Stock is listed
     or admitted to trading or, if not listed or admitted to trading on any
     national securities exchange, the closing sales price of the Common Stock
     as quoted by the NASDAQ National Market System, or in case no reported sale
     takes place, the average of the closing bid and asked prices as quoted by
     the NASDAQ National Market System or any comparable system, or if the
     Common Stock is not quoted on the NASDAQ National Market System or any
     comparable system, the closing sales price or, in case no reported sale
     takes place, the average of the closing bid and asked prices, as furnished
     by any two members of the National Association of Securities Dealers, Inc.
     selected from time to time by the Company for that purpose.

          (e)  In any case in which this Section 4.6 shall require that an
     adjustment be made immediately following a record date established for
     purposes of Section 4.6, the Company may elect to defer (but only until
     five Business Days following the filing by the Company with the Trustee of
     the certificate described in Section 4.10 below) issuing to the holder of
     any Debenture converted after such record date the shares of Common

                                       17
<PAGE>

     Stock and other capital stock of the Company issuable upon such conversion
     over and above the shares of Common Stock and other capital stock of the
     Company issuable upon such conversion only on the basis of the Conversion
     Price prior to adjustment; and, in lieu of the shares the issuance of which
     is so deferred, the Company shall issue or cause its transfer agents to
     issue due bills or other appropriate evidence of the right to receive such
     shares.

SECTION 4.7   No Adjustment.
              -------------

          No adjustment in the Conversion Price shall be required until
cumulative adjustments amount to a change in the Conversion Price of 1% or more
as last adjusted; provided, however, that any adjustments which by reason of
this Section 4.7 are not required to be made shall be carried forward and taken
into account in any subsequent adjustment.  All calculations under this
Article 4 shall be made to the nearest cent or to the nearest one-hundredth of a
share, as the case may be. No adjustment to the Conversion Price shall be made
for cash or dividend distributions paid out of consolidated net income or
retained earnings.

          No adjustment need be made for a transaction referred to in Section
4.6 if all Debentureholders are entitled to participate in the transaction on a
basis and with notice that the Board of Directors determines to be fair and
appropriate in light of the basis and notice on which holders of Common Stock
participate in the transaction.

          No adjustment need be made for rights to purchase Common Stock or
issuances of Common Stock pursuant to a Company plan for reinvestment of
dividends or interest.

          No adjustment need be made for a change in the par value or a change
to no par value of the Common Stock.

          To the extent that the Debentures become convertible into cash, no
adjustment need be made thereafter as to the cash.  Interest will not accrue on
the cash.

SECTION 4.8   Equivalent Adjustments.
              ----------------------

          In the event that, as a result of an adjustment made pursuant to
Section 4.6 above, the holder of any Debenture thereafter surrendered for
conversion shall become entitled to receive any shares of capital stock of the
Company other than shares of its Common Stock, thereafter the Conversion Price
of such other shares so receivable upon conversion of any Debentures shall be
subject to adjustment from time to time in a manner and on terms as nearly
equivalent as practicable to the provisions with respect to Common Stock
contained in this Article 4.

SECTION 4.9   Adjustments for Tax Purposes.
              ----------------------------

          The Company may make such reductions in the Conversion Price, in
addition to acquired by paragraphs (a), (b) and (c) of Section 4.6 above, as it
considers to be advisable that any event treated for Federal income tax purposes
as a dividend of stock or stock shall not be taxable to the recipients thereof.

                                       18
<PAGE>

SECTION 4.10  Notice of Adjustment.
              --------------------

          Whenever the Conversion Price is adjusted, the Company shall promptly
mail to Debentureholders a notice of the adjustment and file with the Trustee an
Officers' Certificate briefly stating the facts requiring the adjustment and the
manner of computing it.  The certificate will be conclusive evidence of the
correctness of such adjustment.

SECTION 4.11  Notice of Certain Transactions.
              ------------------------------

          In the event that:

          (1)  the Company takes any action which would require an adjustment in
     the Conversion Price,

          (2)  the Company consolidates or merges with, or transfers all or
     substantially all of its assets to, another corporation and stockholders of
     the Company must approve the transaction, or

          (3)  there is a dissolution or liquidation of the Company,

Holder of a Debenture may wish to convert such Debenture into shares of Common
Stock prior to the record date for or the effective date of the transaction so
that he may receive the rights, warrants, securities or assets which a holder of
shares of Common Stock on that date may receive.  Therefore, the Company shall
mail to Debentureholders and the Trustee a notice stating the proposed record or
effective date, as the case may be.  The Company shall mail the notice at least
10 days before such date; however, failure to mail such notice or any defect
therein shall affect the validity of any transaction referred to in clause (1),
(2) or (3) of this Section 4.11.

SECTION 4.12  Effect of Reclassifications, Consolidations, Mergers or Sales on
              ----------------------------------------------------------------
              Conversion Privilege.
              --------------------

          If any of the following shall occur, namely:  (i) any reclassification
or change of outstanding shares of Common Stock issuable upon conversion of
Debentures (other than a change in par value, or from par value to no par value,
or from no par value to par value, or as a result of a subdivision or
combination), (ii) any reorganization, consolidation or merger to which the
Company is a party other than a merger in which the Company is the continuing
corporation and which does not result in any reclassification of, or change
(other than a change in name, or par value, or from par value to no par value,
or from no par value to par value, or as a result of a subdivision or
combination) in, outstanding shares of Common Stock or (iii) any sale, lease or
transfer of all or substantially all of the property or business of the Company
as an entirety, then the Company, or such successor or purchasing corporation,
as the case may be, shall, as a condition precedent to such reclassification,
change, consolidation, merger, sale, lease or transfer, execute and deliver to
the Trustee a supplemental indenture providing that the Holder of each Debenture
then outstanding shall have the right to convert such Debenture into the kind
and amount of shares of stock and other securities and property (including cash)
receivable upon such reclassification, change, reorganization, consolidation,
merger, sale or conveyance by a holder of the number of shares of Common Stock,
or fraction thereof, deliverable upon conversion of such Debenture immediately
prior to such reclassification, change, reorganization, consolidation,

                                       19
<PAGE>

merger, sale, lease or transfer. Such supplemental indenture shall provide for
adjustments of the Conversion Price which shall be as nearly equivalent as may
be practicable to the adjustments of the Conversion Price provided for in this
Article 4. The foregoing, however, shall not in any way affect the right a
holder of a Debenture may otherwise have, pursuant to clause (ii) of the last
sentence of subsection (c) of Section 4.6, to receive Rights upon conversion of
a Debenture. If, in the case of any such reorganization, consolidation, merger,
sale, lease or transfer the stock or other securities and property (including
cash) receivable thereupon by a holder of Common Stock includes shares of stock
or other securities and property of a corporation other than the successor or
purchasing corporation, as the case may be, in such reorganization,
consolidation, merger, sale, lease or transfer, 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 Debentures
as the Board of Directors of the Company shall reasonably consider necessary by
reason of the foregoing. The provision of this Section 4.12 shall similarly
apply to successive reorganizations, consolidations, mergers, sales, leases or
transfers.

          In the event the Company shall execute a supplemental indenture
pursuant to this Section 4.12, the Company shall promptly file with the Trustee
an Officers' Certificate briefly stating the reasons therefor, the kind or
amount of shares of stock or securities or property (including cash) receivable
by Holders of the Debentures upon the conversion of their Debentures after any
such reclassification, change, reorganization, consolidation, merger, sale,
lease or transfer, any adjustment to be made with respect thereto and that all
conditions precedent have been complied with.

SECTION 4.13  Trustee's Disclaimer.
              --------------------

          The Trustee has no duty to determine when an adjustment under this
Article 4 should be made, how it should be made or what such adjustment should
be, but may accept as conclusive evidence of the correctness of any such
adjustment, and shall be protected in relying upon, the Officers' Certificate
with respect thereto which the Company is obligated to file with the Trustee
pursuant to Section 4.10.  The Trustee makes no representation as to the
validity or value of any securities or assets issued upon conversion of
Debentures, and the Trustee shall not be responsible for the Company's failure
to comply with any provisions of this Article 4.

          The Trustee shall not be under any responsibility to determine the
correctness of any provisions contained in any supplemental indenture executed
pursuant to Section 4.12, but may accept as conclusive evidence of the
correctness thereof, and shall be protected in relying upon, the Officers'
Certificate with respect thereto which the Company is obligated to file with the
Trustee pursuant to Section 4.12.

SECTION 4.14  Voluntary Reduction.
              -------------------

          The Company from time to time may reduce the Conversion Price by any
amount for any period of time if the period is at least 20 days or such longer
period as may be required by law and if the reduction is irrevocable during the
period; provided, that in no event may the Conversion Price be less than the par
value of a share of Common Stock.

                                       20
<PAGE>

                                   ARTICLE 5

                                 SUBORDINATION

SECTION 5.1   Debentures Subordinated to Senior Indebtedness.
              ----------------------------------------------

          The Company, for itself, its successors and assigns, covenants and
agrees, and each Holder of a Debenture, by his acceptance thereof, likewise
covenants and agrees, that the indebtedness evidenced by the Debentures,
including the payment of the principal thereof and interest thereon, shall be
subordinate and junior in right of payment, to the extent and in the manner set
forth in this Article 5, to the prior payment in full of all Senior
Indebtedness, and that each holder of Senior Indebtedness whether now
outstanding or hereafter created, incurred, assumed or guaranteed shall be
deemed to have acquired Senior Indebtedness in reliance upon the covenants and
provisions contained in this Indenture and the Debentures.  The Debentures shall
not be superior in right of payment to the payment of the indebtedness evidenced
by the Company's 3.5% Convertible Subordinated Debenture due 1999, the Company's
3.0% Convertible Subordinated Note due 1996 and the Company's 6.75% Convertible
Subordinated Debentures due 2002, but shall rank pari passu in all respects with
                                                 ---- -----
such obligation(s).  In addition, all Debentures of this issue rank as to
payment of principal and interest equally and ratably, without priority one over
the other.  The provisions of this Article 5 are made for the benefit of all
holders of Senior Indebtedness and any such holder may proceed to enforce such
provisions.

          Notwithstanding anything contained in this Indenture or the Debentures
to the contrary, all the provisions of this Indenture and the Debentures shall
be subject to the provisions of this Article 5, so far as they may be applicable
thereto.

SECTION 5.2   Debentures Subordinated to Prior Payment of All Senior
              ------------------------------------------------------
              Indebtedness on Dissolution, Liquidation,  Reorganization, etc.
              ---------------------------------------------------------------
              of the Company.
              --------------

          Upon any payment or distribution of the assets of the Company of any
kind or character, whether in cash, property or securities (including any
collateral at any time securing the Debentures), to creditors upon any
dissolution, winding-up, total or partial liquidation, or reorganization of the
Company (whether voluntary or involuntary, or in bankruptcy, insolvency,
reorganization, liquidation, receivership proceedings, or upon an assignment for
the benefit of creditors, or any other marshaling of the assets and liabilities
of the Company, or otherwise), then in such event:

          (a)  all Senior Indebtedness shall first be paid in full (including
     principal thereof and interest thereon) in cash, or have provision made for
     such payment, before any payment is made on account of the principal of or
     interest on the indebtedness evidenced by the Debentures, or any deposit is
     made pursuant to Section 6.4;

          (b)  any payment or distribution of assets of the Company of any kind
     or character, whether in cash, property or securities (other than
     securities of the Company as reorganized or readjusted, or securities of
     the Company or any other company, trust or corporation provided for by a
     plan or reorganization or readjustment, junior, or the payment of which is
     otherwise subordinate, at least to the extent provided in this Article 5
     with respect to the Debentures, to the payment of all Senior Indebtedness
     at the time outstanding and to the payment of all securities issued in
     exchange therefor to the holders

                                       21
<PAGE>

     of the Senior Indebtedness at the time outstanding), to which the Holders
     or the Trustee on behalf of the Holders would be entitled except for the
     provisions of this Article 5, shall be paid or delivered by any debtor,
     Custodian or other person making such payment or distribution, directly to
     the holders of the Senior Indebtedness or their representative or
     representatives, or to the trustee or trustees under any indenture pursuant
     to which any instruments evidencing any of such Senior Indebtedness may
     have been issued, ratably according to the aggregate amounts remaining
     unpaid on account of the principal of and interest on the Senior
     Indebtedness held or represented by each, for application to 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, or provision therefor, to the holders of such Senior
     Indebtedness; and

          (c)  in the event that, notwithstanding the foregoing provisions of
     this Section 5.2, any payment or distribution of assets of the Company of
     any kind or character, whether in cash, property or securities (other than
     securities of the Company as reorganized or readjusted, or securities of
     the Company or any other company, trust or corporation provided for by a
     plan of reorganization or readjustment, junior, or the payment of which is
     otherwise subordinate, at least to the extent provided for in this Article
     5 with respect to the Debentures, to the payment of all Senior Indebtedness
     at the time outstanding and to the payment of all securities issued in
     exchange therefor to the holders of Senior Indebtedness at the time
     outstanding), shall be received by the Trustee or the Holders before all
     Senior Indebtedness is paid in full, or provision made for its payment,
     such payment or distribution (subject to the provisions of Sections 5.6 and
     5.7) shall be held in trust for the benefit of, and shall be immediately
     paid or delivered by the Trustee or such Holders, as the case may be, to
     the holders of Senior Indebtedness remaining unpaid or unprovided for, or
     their representative or representatives, or to the trustee or trustees
     under any indenture pursuant to which any instruments evidencing any of
     such Senior Indebtedness may have been issued, ratably according to the
     aggregate amounts remaining unpaid on account of the principal of and
     interest on the Senior Indebtedness held or represented by each, 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, or provision therefor, to
     the holders of such Senior Indebtedness.

          The Company shall give prompt notice to the Trustee of any
dissolution, winding-up liquidation or reorganization of the Company.

          Upon any distribution of assets of the Company referred to in this
Article 5, the Trustee, subject to the provisions of Sections 9.1 and 9.2, and
the Holders shall be entitled to rely upon any order or decree by any court of
competent jurisdiction in which such dissolution, winding-up, liquidation or
reorganization proceeding is pending, or a certificate of the liquidating
trustee or agent or other person making any distribution to the Trustee or to
the Holders, for the purpose of ascertaining the persons entitled to participate
in such 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 5.

                                       22
<PAGE>

SECTION 5.3   Debentureholders to be Subrogated to Right of Holders of Senior
              ---------------------------------------------------------------
              Indebtedness.
              ------------

          Subject to the prior payment in full of all Senior Indebtedness then
due, the Holders shall be subrogated (equally and ratably with the holders of
all subordinated indebtedness of the Company which by its terms is not superior
in right or payment to the Debentures and ranks on a parity with the Debentures)
to the rights of the holders of Senior Indebtedness to receive payments or
distributions of assets of the Company applicable to the Senior Indebtedness
until the principal of and interest on the Debentures shall be paid in full, and
for purposes of such subrogation, no payments or distributions to the holders of
Senior Indebtedness of assets, whether in cash, property or securities,
distributable to the holders of Senior Indebtedness under the provisions hereof
to which the Holders would be entitled except for the provisions of this Article
5, and no payment pursuant to the provisions of this Article 5 to the holders of
Senior Indebtedness by the Holders shall, as among the Company, its creditors
other than the holders of Senior Indebtedness, and the Holders, be deemed to be
a payment by the Company to or on account of Senior Indebtedness, it being
understood that the provisions of this Article 5 are, and are intended, solely
for the purpose of defining the relative rights of the Holders, on the one hand,
and the holders of Senior Indebtedness, on the other hand.

SECTION 5.4   Obligations of the Company Unconditional.
              ----------------------------------------

          Nothing contained in this Article 5 or elsewhere in this Indenture or
in any Debenture is intended to or shall impair, as among the Company, its
creditors other than the holders of Senior Indebtedness and the Holders, the
obligation of the Company, which is absolute and unconditional, to pay to the
Holders the principal of and interest on the Debentures, as and when the same
shall become due and payable in accordance with the terms of the Debentures, or
to affect the relative rights of the Holders and other creditors of the Company
other than the holders of Senior Indebtedness, nor shall anything herein or
therein prevent the Trustee or any Holder from exercising all remedies otherwise
permitted by applicable law upon the happening of an Event of Default under this
Indenture, subject to the provisions of Article 8, and the rights, if any, under
this Article 5 of the holders of Senior Indebtedness in respect of assets,
whether in cash, property or securities, of the Company received upon the
exercise of any such remedy.

SECTION 5.5   Company Not to Make Payment with Respect to the Debentures in
              -------------------------------------------------------------
              Certain Circumstances.
              ---------------------

          (a)  Upon the happening of a default in payment (whether at maturity
or at a date fixed for prepayment or by acceleration or otherwise) of the
principal of or interest on any Senior Indebtedness, as such default is defined
under any such Senior Indebtedness or in any agreement pursuant to which any
Senior Indebtedness has been issued, then, unless and until the amount of such
Senior Indebtedness then due shall have been paid in full or provision made
therefor in a manner satisfactory to the holders of such Senior Indebtedness, or
such default shall have been cured or waived or shall have ceased to exist, the
Company shall not pay principal of, premium, if any, or interest on the
Debentures or make any deposit pursuant to Section 6.4 or 10.01 and shall not
repurchase, redeem or otherwise retire any Debentures (collectively, "pay the
Debentures"); provided, however, that the Company may pay the Debentures without
regard to the foregoing if the Company and the Trustee receive written notice
approving such payment

                                       23
<PAGE>

from the representative of each outstanding class of Designated Senior
Indebtedness and the Company certifies to the Trustee that such representatives
relate to all outstanding classes of Designated Senior Indebtedness.

          (b)  Upon the happening and during the continuance of any default
under the Bank Credit Agreement (other than a default in payment of principal or
interest thereunder as provided in Section 5.5(a)), which, after the giving of
notice or the passage of time, or both, would constitute an event of default
which would permit the holder or holders of the Bank Debt to accelerate the
maturity thereof (other than a default of the type specified in Section 5.5(a)
above), and after written notice of such default has been given to the Company
and the Trustee by the holder or holders of such Bank Debt or their
representative or representatives, or upon written notice thereof given to the
Company by the holder or holders of such Bank Debt or their representative or
representatives and given to the Trustee by the Company, then, unless and until
such default shall have been cured or waived or shall have ceased to exist, or
provision shall have been made for the payment, in a manner satisfactory to the
holder or holders of such Bank Debt, of all such Bank Debt which would be due in
the event of the acceleration of the maturity thereof, the Company shall not pay
the Debentures.

          (c)  In the event that, notwithstanding the foregoing provision of
this Section 5.5, any payment on account of principal of or interest on the
Debentures shall be made by or on behalf of the Company and received by the
Trustee, any Holder or any Paying Agent (or, if the Company is acting as its own
Paying Agent, money for any such payment shall be segregated and held in trust),
after the happening of a default of the type specified in Section 5.5(a) or (b)
above, then, unless and until the amount of such Senior Indebtedness (in the
case of a default under Section 5.5(a)) or Bank Debt (in the case of a default
under Section 5.5(b)) then due shall have been paid in full, or provision made
therefor or such default shall have been cured or waived, such payment (subject,
in each case, to the provision of Sections 5.6 and 5.7) shall be held in trust
for the benefit of, and shall be immediately paid over to, the holders of Senior
Indebtedness (in the case of a default under Section 5.5(a)) or Bank Debt (in
the case of a default under Section 5.5(b)) or their representative or
representatives or the trustee or trustees under any indenture under which any
instruments evidencing any of such indebtedness may have been issued, ratably
according to the aggregate amounts remaining unpaid on account of the principal
of and interest on the Senior Indebtedness (in the case of a default under
Section 5.5(a)) or Bank Debt (in the case of a default under Section 5.5(b))
held or represented by each, for application to the payment of all such
indebtedness remaining unpaid to the extent necessary to pay all such
indebtedness in accordance with its terms, after giving effect to any concurrent
payment or distribution to or for the benefit of the holders of such
indebtedness.  The Company shall give prompt written notice to the Trustee of
any default under any Senior Indebtedness (in the case of a default under
Section 5.5(a)) or Bank Debt (in the case of a default under Section 5.5(b)) or
under any agreement pursuant to which such indebtedness may have been issued.

SECTION 5.6   Trustee Entitled to Assume Payments Not Prohibited in Absence
              -------------------------------------------------------------
              of Notice.
              ---------

          The Trustee shall not at any time be charged with knowledge of the
existence of any facts which would prohibit the making of any payment to or by
the Trustee, unless and until the Trustee shall have received notice thereof
from the Company or from the holder or holders of senior Indebtedness or from
their representative or representatives; and, prior to the receipt of

                                       24
<PAGE>

any such notice, the Trustee, subject to the provisions of Sections 9.1 and 9.2,
shall be entitled to assume conclusively that no such facts exist.

          The Trustee shall be entitled to rely on the delivery to it of a
written notice by a person representing himself to be a holder of Senior
Indebtedness (or a representative of such holder) to establish that such notice
has been given by a holder of Senior Indebtedness or a representative of any
such holder.  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 Indebtedness to participate in any payment or distribution pursuant to
this Article 5, 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
each person under this Article 5, 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 5.7   Application by Trustee of Monies Deposited with It.
              --------------------------------------------------

          Money or U.S. Government Obligations deposited in trust with the
Trustee pursuant to and in accordance with this Article 5 and Sections 6.4 and
10.1 shall be for the sole benefit of Debentureholders and shall thereafter not
be subject to the subordination provisions of this Article 5.  Otherwise, any
deposit of monies by the Company with the Trustee or any Paying Agent (whether
or not in trust) for the payment of the principal of or interest on any
Debentures shall be subject to the provisions of Sections 5.1, 5.2, 5.3 and 5.5;
except that, if two Business Days prior to the date on which by the terms of
this Indenture any such monies may become payable for any purpose (including,
without limitation, the payment of either the principal of or interest on any
Debenture), the Trustee shall not have received with respect to such monies the
notice provided for in Section 5.6, then the Trustee or any Paying Agent shall
have full power and authority to receive such monies and to apply such monies to
the purpose for which they were received, and shall not be affected by any
notice to the contrary which may be received by it on or after such date.  This
Section 5.7 shall be construed solely for the benefit of the Trustee and the
Paying Agent and shall not otherwise affect the rights that holders of Senior
Indebtedness may have to recover any such payments from the Holders in
accordance with the provisions of this Article 5.

SECTION 5.8   Subordination Rights Not Impaired by Acts or Omissions of Company
              -----------------------------------------------------------------
              or Holders of Senior Indebtedness.
              ---------------------------------

          No right of any present or future holders 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 which any such holder may have or
be otherwise charged with.  The holders of any Senior Indebtedness may extend,
renew, modify or amend the terms of such Senior Indebtedness or any security
therefor and release, sell or exchange such security and otherwise deal freely
with the Company, all without affecting the liabilities and obligations of the
parties to this Indenture or the Holders.  No provision in any supplemental
indenture which affects the superior position of the holders of the Senior

                                       25
<PAGE>

Indebtedness shall be effective against the holders of the Senior Indebtedness
unless the holders of such Senior Indebtedness (required pursuant to the terms
of such Senior Indebtedness to give such consent) have consented thereto.

SECTION 5.9   Debentureholders Authorize Trustee to Effectuate Subordination
              --------------------------------------------------------------
              of Debentures.
              -------------

          Without purporting to limit the authority of the Trustee as may be
appropriate in other circumstances, each Holder of any Debenture by his
acceptance thereof, irrevocably authorizes and expressly directs the Trustee on
his behalf to take such action as may be necessary or appropriate to effectuate
the subordination provided in this Article 5 and appoints the Trustee his
attorney-in-fact for such purpose, including, in the event of any dissolution,
winding-up or liquidation or reorganization under Bankruptcy Law of the Company
(whether in bankruptcy, insolvency or receivership proceedings or otherwise),
the timely filing of a claim for the unpaid balance of its or his Debentures in
the form required in such proceedings, and the causing of such claim to be
approved.  If the Trustee does not file a proper claim or proof of debt in the
form required in such proceedings prior to 30 days before the expiration of the
time to file such claims or proofs, then any of the holders of Senior
Indebtedness have the right to demand, sue for, collect, receive and receipt
for, the payments and distributions in respect of the Debentures which are
required to be paid or delivered to the holders of Senior Indebtedness as
provided in this Article 5, and to file and prove all claims therefor and to
take all such other action in the name of the Holders or otherwise, as any such
holder of Senior Indebtedness or such holder's representative may determine to
be necessary or appropriate for the enforcement of the provisions of this
Article 5.

SECTION 5.10  Right of Trustee to Hold Senior Indebtedness.
              --------------------------------------------

          The Trustee, in its individual capacity, shall be entitled to all of
the rights set forth in this Article 5 in respect of any Senior Indebtedness at
any time held by it to the same extent as any other holder of Senior
Indebtedness, and nothing in this Indenture shall be construed to deprive the
Trustee of any of its rights as such holder.

SECTION 5.11  Article 5 Not to Prevent Events of Default.
              ------------------------------------------

          The failure to make a payment on account of the principal of or
interest on the Debentures by reason of any provision in this Article 5 shall
not be construed as preventing the occurrence of an Event of Default under
Section 8.1.

SECTION 5.12  No Fiduciary Duty Created to Holders of Senior Indebtedness.
              -----------------------------------------------------------

          Notwithstanding any other provision in this Article 5, the Trustee
shall not be deemed to owe any fiduciary duty to the holders of Senior
Indebtedness by virtue of the provisions of this Article 5.

                                       26
<PAGE>

                                   ARTICLE 6

                                   COVENANTS

SECTION 6.1   Payment of Debentures.
              ---------------------

          The Company shall pay the principal of and interest on the Debentures
on the dates and in the manner provided in the Debentures and this Indenture.
An installment of principal or interest shall be considered paid on the date it
is due if the Paying Agent (other than the Company or an Affiliate of the
Company) holds on that date money designated for and sufficient to pay the
installment.  The Company shall pay interest on overdue principal at the rate
borne by the Debentures per annum; it shall pay interest on overdue installments
of interest at the same rate to the extent lawful.

SECTION 6.2   SEC Reports.
              -----------

          The Company shall file all reports and other information and documents
which it is required to file with the SEC pursuant to Section 13 or 15(d) of the
Securities Exchange Act of 1934, as amended (the "Exchange Act"), and within 15
days after it files them with the SEC, the Company shall file copies of all such
reports, information and other documents with the Trustee. The Company will
cause any quarterly and annual reports which it mails to its stockholders to be
mailed to the Holders of the Debentures.

          If the Company is not subject to the reporting requirements of Section
13 or 15(d) of the Exchange Act, the Company will prepare, for the first three
quarters of each fiscal year, quarterly financial statements substantially
equivalent to the financial statements required to be included in a report on
Form 10-Q under the Exchange Act.  The Company will also prepare, on an annual
basis, complete audited consolidated financial statements including, but not
limited to, a balance sheet, a statement of income and retained earnings, a
statement of changes in financial position and all appropriate notes.  All such
financial statements will be prepared in accordance with generally accepted
accounting principles consistently applied, except for changes with which the
Company's independent accountants concur, and except that quarterly statements
may be subject to year-end adjustments.  The Company will cause a copy of such
financial statements to be filed with the Trustee and mailed to the Holders of
the Debentures within 50 days after the close of each of the first three
quarters of each fiscal year and within 95 days after the close of each fiscal
year.  The Company will also comply with the other provisions of TIA (S) 314(a).

SECTION 6.3   Waiver of Usury Defense.
              -----------------------

          The Company agrees that it will not assert, plead (as a defense or
otherwise) or in any manner whatsoever claim (and will actively resist any
attempt to compel it to assert, plead or claim) in any action, suit or
proceeding that the interest rate on the Debentures violates present or future
usury or other laws relating to the interest payable on any indebtedness and
will not otherwise avail itself (and will actively resist any attempt to compel
it to avail itself) of the benefits or advantages of any such laws.

                                       27
<PAGE>

SECTION 6.4   Liquidation.
              -----------

          Subject to the provisions of Article 5, so far as they may be
applicable hereto, the Board of Directors or the stockholders of the Company may
not adopt a plan of liquidation which plan provides for, contemplates or the
effectuation of which is preceded by (a) the sale, lease, conveyance or other
disposition of all or substantially all of the assets of the Company otherwise
than substantially as an entirety (Article 7 of this Indenture being the Article
which governs any such sale, lease, conveyance or other disposition
substantially as an entirety), and (b) the distribution of all or substantially
all of the proceeds of such sale, lease, conveyance or other disposition and of
the remaining assets of the Company to the holders of the capital stock of the
Company, unless the Company shall in connection with the adoption of such plan
make provision for, or agree that prior to making any liquidating distributions
it will make provision for, the satisfaction of the Company's obligations
hereunder and under the Debentures as to the payment of the principal and
interest.  The Company shall be deemed to make provision for such payments only
if (1) the Company irrevocably deposits in trust with the Trustee money or U.S.
Government Obligations maturing as to principal and interest in such amounts and
at such times as are sufficient, without consideration of any reinvestment of
such interest, to pay the principal of and interest on the Debentures then
outstanding to maturity and to pay all other sums payable by it hereunder, or
(2) there is an express assumption of the due and punctual payment of the
Company's obligations hereunder and under the Debentures and the performance and
observance of all covenants and conditions to be performed by the Company
hereunder, by the execution and delivery of a supplemental indenture in form
satisfactory to the Trustee by a person who acquires, or will acquire (otherwise
than pursuant to a lease) a portion of the assets of the Company, and which
person will have assets (immediately after the acquisition) and aggregate
earnings (for such person's four full fiscal quarters immediately preceding such
acquisition) equal to not less than the assets of the Company (immediately
preceding such acquisition) and the aggregate earnings of the Company (for its
four full fiscal quarters immediately preceding the acquisition), respectively,
and which is a corporation organized under the laws of the United States, any
State thereof or the District of Columbia; provided, however, that Company shall
not make any liquidating distribution until after the Company shall have
certified to the Trustee with an Officers' Certificate at least five days prior
to the making of any liquidating distribution that it has complied with the
provisions of this Section 6.4.

SECTION 6.5   Compliance Certificates.
              -----------------------

          The Company shall deliver to the Trustee within 120 days after the end
of each fiscal year of the Company, an Officers' Certificate as to the signer's
knowledge of the Company's compliance with all conditions and covenants on its
part contained in this Indenture and stating whether or not the signer knows of
any default or Event of Default.  If such signer knows of such a default or
Event of Default, the Certificate shall describe the default or Event of Default
and the efforts to remedy the same.  For the purposes of this Section 6.5,
compliance shall be determined without regard to any grace period or requirement
of notice provided pursuant to the terms of this Indenture.  The Certificate
need not comply with Section 12.4 hereof.

SECTION 6.6   Notice of Defaults.
              ------------------

          In the event that indebtedness of the Company in an aggregate amount
in excess of $10,000,000 is declared due and payable before its maturity because
of the occurrence of any default under such indebtedness, the Company will
promptly give written notice to the Trustee of

                                       28
<PAGE>

such declaration or of the occurrence of any event which, with the giving of
notice or the passage of time, or both, would entitle the holder or holders of
such indebtedness to declare such indebtedness due and payable before its
maturity.

SECTION 6.7   Payment of Taxes and Other Claims.
              ---------------------------------

          The Company will pay or discharge or cause to be paid or discharged,
before the same shall become delinquent, (1) all material taxes, assessments and
governmental charges levied or imposed upon the Company, directly or by reason
of its ownership of any Subsidiary or upon the income, profits or property of
the Company; and (2) all materials lawful claims for labor, materials and
supplies, which, if unpaid, might by law become a lien upon the property of the
Company; provided, however, that the Company shall not be required to pay or
discharge or cause to be paid or discharged any such tax, assessment, charge or
claim whose amount, applicability or validity is being contested in good faith
by appropriate proceedings and for which adequate provision has been made.

SECTION 6.8   Corporate Existence.
              -------------------

          Subject to Section 6.4 and Article 7, the Company will do or cause to
be done all things necessary to preserve and keep in full force and effect its
corporate existence and rights (charter and statutory); provided, however, that
the Company shall not be required to preserve any right if the Board of
Directors shall determine that the preservation is no longer desirable in the
conduct of the Company's business and that the loss thereof is not, and will not
be, adverse in any material respect to the Holders.

SECTION 6.9   Maintenance of Properties.
              -------------------------

          Subject to Section 6.4, the Company will cause all material properties
owned, leased or licensed in the conduct of its business to be maintained and
kept in good condition, repair and working order and supplied with all necessary
equipment and will cause to be made all necessary repairs, renewals,
replacements, betterments and improvements thereof and thereto, all as in the
judgment of the Company may be necessary so that the business carried on in
connection therewith may be properly and advantageously conducted at all times
while any Debentures are outstanding; provided, however, that nothing in this
Section 6.9 shall prevent the Company from discontinuing the maintenance of any
such properties if, in the judgment of the Board of Directors, such
discontinuance is desirable in the conduct of the Company's business and is not,
and will not be, adverse in any material respect to the Holders.

SECTION 6.10  Purchase of the Debentures at Option of the Holder Upon
              -------------------------------------------------------
              Fundamental Change.
              ------------------

          (a)  If at any time that the Debentures remain outstanding there shall
have occurred a Fundamental Change (as hereinafter defined), each holder of the
Debentures shall have the right to require the Company to purchase all of such
holders' Debentures or any portion thereof that is an integral multiple of
$1,000, at a purchase price (the "Fundamental Change purchase Price") equal to
the principal amount thereof plus accrued interest to the Final Surrender Date
(as hereinafter defined), as of the date that is not less than ten nor more than
20 days after the Final Surrender Date (the "Fundamental Change Purchase Date"),
subject to the

                                       29
<PAGE>

Company's ability to pay the Fundamental Change Purchase Price under the terms
of its then-existing Bank Credit Agreement or other agreements relating to
borrowings which constitute Senior Indebtedness, and subject to satisfaction by
or on behalf of the Holder of the requirements set forth in subsection (c) of
this Section 6.10. The term "Final Surrender Date" shall mean the date that is
60 days after the date of mailing the notice of Fundamental Change as described
in subsection (b) of this Section 6.10.

          The Fundamental Change Purchase Price shall be payable, at the option
of the Company, in cash or marketable shares of common stock of the Company or
any successor corporation based on its then fair market value, or a combination
thereof, subject to the requirements set forth in subsection (d) of this Section
6.10.

          The term "Fundamental Change" shall mean either of the following:

          (a)  a "person" or "Group" (within the meaning of Sections 13(d) and
     14(d)(2) of the Exchange Act) becoming, in one transaction or a series of
     related transactions, the "beneficial owner" (as defined in Rule 13d-3
     under the Exchange Act) of Voting Shares of the Company entitled to
     exercise more than 50% of the total voting power of all outstanding Voting
     Shares of the Company (including any Voting Shares that are not then
     outstanding of which such person or group is deemed the beneficial owner);
     or

          (b)  any consolidation of the Company with, or merger of the Company
     into, any other person, any merger of another person into the Company, or
     any sale, lease or transfer of all or substantially all of the assets of
     the Company to another person (other than a merger (i) which results in the
     holders of Common Stock of the Company immediately prior to giving effect
     to such transaction owning shares of capital stock of the surviving
     corporation in such transaction representing in excess of 40% of the total
     voting power of all shares of capital stock of such surviving corporation
     entitled to vote generally in the election of directors and (ii) in which
     the shares of the surviving corporation held by such holders are, or
     immediately upon issuance will be, listed on a national securities exchange
     or quoted on the NASDAQ National Market System and are not subject to any
     right of repurchase by the issuer thereof or any third party and are not
     otherwise subject to any encumbrance as a result of such transaction,
     provided, that the surviving corporation assumes or guarantees the
     Company's obligations under the Debentures); provided, however, that a
     Fundamental Change shall not occur if either (i) for any five trading days
     immediately preceding either the public announcement by the Company of such
     transaction or the consummation of such transaction, the last sale price of
     the Common Stock is equal to at least 105% of the conversion price in
     effect on such trading days, or (ii) at least 90% of the consideration
     (excluding cash payments for fractional shares) in such transaction or
     transactions to the holders of Common Stock consists of shares of common
     stock at are, or immediately upon issuance will be, listed on a national
     securities exchange or quoted on the NASDAQ National Market System, and as
     a result of such transaction or transactions, the Debentures become
     convertible into such common stock.

          For purposes of the foregoing, the term "Voting Shares" shall mean all
outstanding shares of any class or classes (however designated) of capital stock
entitled to vote generally in the election of members of the Board of Directors.

                                       30
<PAGE>

          (b)  Within 30 days after the occurrence of a Fundamental Change, the
Company shall mall a written notice of Fundamental Change by first-class mail to
the Trustee and to each Holder (and to beneficial owners as required by
applicable law) and shall cause a copy of such notice to be published in a dally
newspaper of national circulation (which shall be The Wall Street Journal unless
                                                  -----------------------
it is not then so circulated).  The notice shall include the form of a
Fundamental Change Purchase Notice (as defined below) to be completed by the
Holder and shall state:

          (1)  the date of such Fundamental Change and, briefly, the events
          causing such Fundamental Change;

          (2)  the date by which the Fundamental Change Purchase Notice pursuant
          to this Section 6.10 must be given;

          (3)  the Fundamental Change Purchase Date;

          (4)  the Fundamental Change Purchase Price;

          (5)  that the Fundamental Change Purchase Price is payable in cash or
          shares of marketable common stock of the Company or any successor
          corporation based on its fair market value, or a combination thereof,
          as may be determined by the Company and set forth in a supplemental
          notice to be provided at least two Business Days prior to the Final
          Surrender Date pursuant to Section 6.10(d);

          (6)  briefly, the conversion rights of the Debentures including,
          without limitation, whether the lenders under the Company's Bank
          Credit will permit the payment of the Fundamental Change Purchase
          Price;

          (7)  the name and address of the Paying Agent and the Conversion
          Agent;

          (8)  the Conversion Price then in effect and any adjustments thereto
          arising out of such Fundamental Change;

          (9)  that Debentures as to which a Fundamental Change Purchase Notice
          has been given may be converted into Common Stock only to the extent
          that the Fundamental Change Purchase Notice has been withdrawn in
          accordance with the terms of this Indenture;

          (10) the procedures that the Holder must follow to exercise rights
          under this Section 6.10;

          (11) the procedures for withdrawing a Fundamental Change Purchase
          Notice, including a form of notice of withdrawal; and

          (12) that the Holder must satisfy the requirements set forth in the
          Debentures in order to convert the Debentures.

                                       31
<PAGE>

          (c)  A Holder may exercise its rights specified in subsection (a) of
this Section 6.10 upon delivery of a written notice of the exercise of such
rights (a "Fundamental Change Purchase Notice") to the Paying Agent at any time
prior to the close of business on the Final Surrender Date, stating:

          (1)  the certificate number of each Debenture that the Holder will
          deliver to be purchased;

          (2)  the portion of the principal amount of each Debenture that the
          Holder will deliver to be purchased, which portion must be $1,000 or
          an integral multiple thereof; and

          (3)  that such Debenture shall be purchased pursuant to the terms and
          conditions specified in this Indenture.

          The delivery of such Debenture to the Paying Agent prior to or on the
Final Surrender Date (together with all necessary endorsements) at the office of
the Paying Agent shall be a condition to the receipt by the Holder of the
Fundamental Change Purchase Price therefor; provided, however, that such
                                            --------  -------
Fundamental Change Purchase Price shall be so paid pursuant to this Section 6.10
only if the Debenture so delivered to the Paying Agent shall conform in all
respects to the description thereof set forth in the related Fundamental Change
Purchase Notice.

          The Company shall purchase from the Holder thereof, pursuant to this
Section 6.10, a portion of a Debenture if the principal amount of such portion
is $1,000 or an integral multiple of $1,000.  Provisions of this Indenture that
apply to the purchase of all of a Debenture pursuant to Sections 6.10 through
6.15 also apply to the purchase of such portion of such Debenture.

          Notwithstanding anything herein to the contrary, any Holder delivering
to the Paying Agent the Fundamental Change Purchase Notice contemplated by this
Section 6.10(c) shall have the right to withdraw such Fundamental Change
Purchase Notice in whole or in a portion thereof that is $1,000 or in an
integral multiple thereof at any time prior to the close of  business on the
Final Surrender Date by delivery of a written notice of withdrawal to the Paying
Agent in accordance with Section 6.11.

          The Paying Agent shall promptly notify the Company of the receipt by
it of any Fundamental Change Purchase Notice or written withdrawal thereof.

          (d)  At least two Business Days prior to the Final Surrender Date, the
Company shall mail and cause to be published a supplemental notice of
Fundamental Change in similar form and manner as set forth in Section 6.10(b)
hereof, which supplemental notice shall also state whether and to what extent
the Fundamental Change Purchase Price will be paid in cash or equivalent shares
of common stock of the Company or any successor corporation.  For purposes of
calculating the number of shares of common stock issuable upon such redemption,
the value of any such common stock will be equal to the average of the closing
prices of such common stock for the five trading days ending on the third
trading day immediately preceding the Final Surrender Date.  Payment may not be
made in shares of common stock unless such shares have been, or will be no later
than the Fundamental Change Purchase Date, registered

                                       32
<PAGE>

under the Securities Act, or are freely tradeable pursuant to an exemption
thereunder and are listed on a United States national securities exchange or
quoted on the NASDAQ National Market System at the time of payment.

SECTION 6.11  Effect of Fundamental Change Purchase Notice.
              --------------------------------------------

          Upon receipt by the Paying Agent of the Fundamental Change Purchase
Notice specified in Section 6.10(c) and delivery to the Paying Agent of the
Debenture in respect of which such Fundamental Change Purchase Notice was given,
the Holder of such Debenture shall (unless such Fundamental Change Purchase
Notice is withdrawn as specified below) thereafter be entitled to receive solely
the Fundamental Change Purchase Price with respect to such Debenture.  Such
Fundamental Change Purchase Price shall be paid to such Holder promptly
following the Fundamental Change Purchase Date with respect to such Debenture
(provided the conditions in Section 6.10(c) have been satisfied).  Debentures in
respect of which a Fundamental Change Purchase Notice has been given by the
Holder thereof may not be converted into shares of Common Stock on or after the
date of the delivery of such Fundamental Change Purchase Notice unless such
Fundamental Change Purchase Notice has first been validly withdrawn.

          A Fundamental Change Purchase Notice may be withdrawn by means of a
written notice of withdrawal delivered to the office of the Paying Agent at any
time prior to the close of business on the Final Surrender Date to which it
relates, specifying:

          (1)  the certificate number of each Debenture in respect of which such
          notice of withdrawal is being submitted,

          (2)  the principal amount of the Debenture or portion thereof with
          respect to which such notice of withdrawal is being submitted, and

          (3)  the principal amount, if any, of such Debenture that remains
          subject to the original Fundamental Change Purchase Notice and that
          has been or will be delivered for purchase by the Company.

          There shall be no purchase of any Debentures pursuant to Section 6.10
if there has occurred (prior to, on or after, as the case may be, the giving, by
the Holders of such Debentures, of the required Fundamental Change Purchase
Notice) and is continuing an Event of Default (other than a default in the
payment of the Fundamental Change Purchase Price with respect to such
Debentures).

SECTION 6.12  Deposit of Fundamental Change Purchase Price.
              --------------------------------------------

          On or before the Business Day prior to a Fundamental Change Purchase
Date, the Company shall deposit with the Trustee or with the Paying Agent (or,
if the Company is acting as the Paying Agent, shall segregate and hold in trust
as provided in Section 2.4) an amount of cash or shares of marketable common
stock of the Company or any successor corporation, in the manner provided in
Section 6.10(d), sufficient to pay the aggregate Fundamental Change Purchase
Price of all the Debentures or portions thereof that are to be purchased as of
such Fundamental Change Purchase Date.  The manner in which the deposit required
by this

                                       33
<PAGE>

Section 6.12 is made by the Company shall be at the option of the Company,
provided that any deposit of cash shall be made in a manner such that the
Trustee or the Paying Agent shall have immediately available funds on the
Business Day prior to the Fundamental Change Purchase Date.

          If the Paying Agent holds, in accordance with the terms hereof, cash
or shares of marketable common stock of the Company or any successor
corporation, in the manner provided in Section 6.10(d), sufficient to pay the
Fundamental Change Purchase Price of any Debenture properly tendered for
redemption and not subsequently withdrawn, then, on and after the Fundamental
Change Purchase Date, such Debenture will cease to be outstanding and interest
on such Debenture will cease to accrue and will be deemed paid, and all other
rights of the Holder in respect thereof shall terminate (other than the right to
receive the Fundamental Change Purchase Price).

SECTION 6.13  Debentures Purchased in Part.
              ----------------------------

          Any Debenture that is to be purchased only in part shall be
surrendered at the office of the Paying Agent (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 such Holder's attorney duly authorized in writing), and the Company
shall execute and the Trustee shall authenticate and deliver to the Holder of
such Debenture, without service charge, a new Debenture or Debentures, of such
authorized denomination or denominations as may be requested by such Holder, in
aggregate principal amount equal to, and in exchange for, the portion of the
principal amount of the Debenture so surrendered that is not purchased.

SECTION 6.14  Compliance with Securities Laws upon Purchase of any Debentures.
              ---------------------------------------------------------------

          In connection with any offer to purchase or purchase of any Debentures
under Section 6.10 hereof (provided that such offer or purchase constitutes an
"issuer tender offer" for purposes of Rule 13e-4 (which term, as used herein,
includes any successor provision thereto) at the time of such offer or
purchase), the Company shall (i) comply with Rule 13e-4 and Rule 14e-1 under the
Exchange Act, (ii) file the related Schedule 13E-4 (or any successor Schedule,
form or report) under the Exchange Act, and (iii) otherwise comply with all
Federal and state securities laws so as to permit the rights of the Holders and
obligations of the Company under Sections 6.10 through 6.13 to be exercised in
the tune and in the manner specified therein.

SECTION 6.15  Repayment to the Company.
              ------------------------

          Subject to the provisions of Section 5.7 to the extent that the
aggregate amount of cash or marketable stock deposited by the Company pursuant
to Section 6.12 exceeds the aggregate Fundamental Change Purchase Price of the
Debentures or portions thereof to be purchased, then promptly after the Business
Day following the Fundamental Change Purchase Date the Trustee or the Paying
Agent, as the case may be, shall return any such excess to the Company.

                                       34
<PAGE>

SECTION 6.16   No Amendments to Section 6.05(d) of the Bank Credit Agreement.
               -------------------------------------------------------------

          The Company shall not, and shall cause SkyTel not to, amend, alter or
modify Section 6.05(d) of the Bank Credit Agreement as in effect on the date
hereof (or any similar provision in any amended, supplemented or replacement
agreement) so as to restrict SkyTel from making loans to Mtel in order to fund
interest and principal payments on the Debentures.

SECTION 6.17   144A Resale.
               -----------

          Neither the Company nor its Subsidiaries shall conduct their business
or take any action at would cause either the Debentures or the Common Stock
issuable upon conversion thereof pursuant to Article 4 to become ineligible for
resale under Rule 144A under the Securities Act.


                                   ARTICLE 7

                             SUCCESSOR CORPORATION

SECTION 7.1   When Company May Merge, etc.
              ---------------------------

          The Company shall not consolidate with or merge with or into, or sell,
lease, convey, transfer or otherwise dispose of all or substantially all of its
assets to, any person unless:

          (a) either the Company shall be the resulting or surviving entity or
     such person is a corporation organized and existing under the laws of the
     United States, a State thereof or the District of Columbia; provided,
     however, that this subsection (a) shall not apply in the event of a
     transaction constituting a Fundamental Change;

          (b) such person expressly assumes by supplemental indenture executed
     and delivered to the Trustee, in form satisfactory to the Trustee, all the
     obligations of the Company under the Debentures and this Indenture (in
     which case all such obligations of the Company shall terminate); and

          (c) immediately before and immediately after giving effect to such
     transaction and treating any indebtedness which becomes an obligation of
     the Company as a result of such transaction as having been incurred by the
     Company at the time of such transaction, no default or Event of Default
     shall have occurred and be continuing.

          The Company shall deliver to the Trustee prior to the proposed
transaction an Officers' Certificate and an Opinion of Counsel, each of which
shall comply with Section 12.4 shall state that such consolidation, merger or
transfer and such supplemental indenture comply with this Article 7 and that all
conditions precedent herein provided for relating to such transaction have been
complied with.

SECTION 7.2   Successor Corporation Substituted.
              ---------------------------------

          Upon any consolidation or merger, or any transfer of all or
substantially all of the assets of the Company in accordance with Section 7.1,
the successor corporation formed by such consolidation or into which the Company
is merged or to which such transfer is made shall

                                       35
<PAGE>

succeed to, and be substituted for, and may exercise every right and power of,
the Company under this Indenture with the same effect as if such successor
corporation had been named as the Company herein.


                                   ARTICLE 8

                              DEFAULT AND REMEDIES

SECTION 8.1   Events of Default.
              -----------------

          An "Event of Default" occurs if:

          (1) the Company defaults in the payment of interest on any Debenture
     when the same becomes due and payable (whether or not such payment shall be
     prohibited by the provisions of Article 5) and the default continues for a
     period of 30 days;

          (2) the Company defaults in the payment of the principal of or
     premium, if any, of any Debenture when the same becomes due and payable at
     maturity, upon redemption or otherwise, including, without limitation, the
     failure by the Company to redeem the Debentures upon a Fundamental Change
     (whether or not such payment shall be prohibited by the provisions of
     Article 5);

          (3) the Company fails to comply with any of its other covenants or
     agreements contained in the Debentures or this Indenture, including,
     without limitation, failure by the Company to redeem or repurchase the
     Debentures at such times and in such manner as may be required by this
     Indenture (whether or not such payment shall be prohibited by the
     provisions of Article 5) and the default continues for the period and after
     the notice specified below;

          (4) the Company shall fail to pay at maturity or at a date fixed for
     prepayment or by acceleration (provided, however, such acceleration is not
     withdrawn, cancelled or otherwise annulled within 10 days following the
     occurrence of such acceleration) principal of, premium, if any, or interest
     under any bond, debenture, note or other evidence of indebtedness for money
     borrowed or under any mortgage, indenture or other instrument under which
     there may be issued or by which there may be secured or evidenced any
     indebtedness for money borrowed by the Company or under any guaranteed of
     payment by the Company of indebtedness for money borrowed, whether such
     indebtedness or guarantee now exists or shall hereafter be created;
     provided, however, no such Event of Default shall exist under this Section
     8.1(4) unless the aggregate amount (which is due and unpaid whether by
     reason of maturity or at a date fixed for prepayment or by acceleration,
     provided, however, such acceleration is not withdrawn, cancelled or
     otherwise annulled within 10 days following the occurrence of such
     acceleration) of such principal, premium, if any, and interest is in excess
     of $10,000,000;

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

                                       36
<PAGE>

               (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;

               (C) consents to the appointment of a Custodian of it or for all
     or substantially all of its property; or

               (D) makes a general assignment for the benefit of its creditors;
     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 any Subsidiary in an
     involuntary case or proceeding;

               (B) appoints a Custodian of the Company or any Subsidiary or for
     all or substantially all of the property of any of them; or

               (C) orders the liquidation of the Company or any Subsidiary;

     and in each case the order or decree remains unstayed and in effect for 60
days.

          The term "Bankruptcy Law" means Title 11, U.S. Code or any similar
Federal or state law for the relief of debtors.  The term "Custodian" means any
receiver, trustee, assignee, liquidator, sequestrator or similar official under
any Bankruptcy Law.

          A default under clause (3) is not an Event of Default until the
Trustee notifies the Company or the Holders of at least 25 % in principal amount
of the Debentures then outstanding notify the Company and the Trustee, of the
default, and the Company does not cure the default within 30 days after receipt
of such notice.  The notice given pursuant to this Section 8.1 must specify the
default, demand that it be remedied and state that the notice is a "Notice of
Default". When a default is cured, it ceases.

          Subject to the provisions of Sections 9.1 and 9.2, the Trustee shall
not be charged with knowledge of any Event of Default unless written notice
thereof shall have been given to a Trust Officer at the corporate trust office
of the Trustee by the Company, the Paying Agent, any Holder or an agent of any
Holder.

SECTION 8.2   Acceleration.
              ------------

          If an Event of Default (other than an Event of Default specified in
Section 8.1(5) or (6)) occurs and is continuing, the Trustee may, by notice to
the Company, or the Holders of at least 25% in principal amount of the
Debentures then outstanding may, by notice to the Company and the Trustee, and
the Trustee shall, upon the request of such Holders, declare all unpaid
principal of and accrued interest to the date of acceleration on the Debentures
then outstanding (if not then due and payable) to be due and payable upon any
such declaration, the same shall become and be immediately due and payable.  If
an Event of Default specified in

                                       37
<PAGE>

Section 8.1(5) or (6) occurs, all unpaid principal of and accrued interest on
the Debentures then outstanding shall ipso facto become and be immediately due
                                      ---- -----
and payable without any declaration or other act on the pan of the Trustee or
any Debentureholder. The Holders of a majority in principal amount of the
Debentures then outstanding by notice to the Trustee may rescind and annul an
acceleration and its consequences if (i) all existing Events of Default, other
than the nonpayment of the principal of and accrued interest on the Debentures
which has become due solely by such declaration of acceleration, have been cured
or waived; (ii) to the extent the payment of such interest is lawful, interest
on overdue installments of interest and overdue principal, which has become due
otherwise than by such declaration of acceleration, has been paid; (iii) the
rescission would not conflict with any judgment or decree of a court of
competent jurisdiction; and (iv) all payments due to the Trustee and any
predecessor Trustee under Section 9.7 have been made. Anything herein contained
to the contrary notwithstanding, in the event of any acceleration pursuant to
this Section 8.2, the Company shall not be obligated to pay any premium which it
would have had to pay if it had then elected to redeem the Debentures pursuant
to paragraph 15 of the Debentures, except in the case of any Event of Default
occurring by reason of any willful action (or inaction) taken (or not taken) by
or on behalf of the Company with the intention of avoiding payment of the
premium which it would have had to pay if it had then elected to redeem the
Debentures pursuant to paragraph 15 of the Debentures, in which case an
equivalent premium shall also become and be immediately due and payable to the
extent permitted by law.

SECTION 8.3   Other Remedies.
              --------------

          If an Event of Default occurs and is continuing, the Trustee may
pursue any available remedy by proceeding at law or in equity to collect the
payment of the principal of or interest on the Debentures or to enforce the
performance of any provision of the Debentures or this Indenture.

          The Trustee may maintain a proceeding even if it does not possess any
of the Debentures or does not produce any of them in the proceeding.  A delay or
omission by the Trustee or any Debentureholder in exercising any right or remedy
accruing upon an Event of Default shall not impair the right or remedy or
constitute a waiver of or acquiescence in the Event of Default.  No remedy is
exclusive of any other remedy.  All available Remedies are cumulative to the
extent permitted by law.

SECTION 8.4   Waiver of Defaults and Events of Default.
              ----------------------------------------

          Subject to Sections 8.7 and 11.2, the Holders of a majority in
principal amount of the Debentures then outstanding by notice to the Trustee may
waive an existing default or Event of Default and its consequences, except a
default in the payment of the principal of or interest on any Debenture as
specified in clauses (1) and (2) of Section 8.1 or a failure by the Company to
convert any Debenture into Common Stock in accordance with Article 4.  When a
default or Event of Default is waived, it is cured and ceases.

SECTION 8.5   Control by Majority.
              -------------------

          The Holders of a majority in principal amount of the Debentures then
outstanding may direct the time, method and place of conducting any proceeding
for any remedy available to

                                       38
<PAGE>

the Trustee or exercising any trust or power conferred on it. However, the
Trustee may refuse to follow any direction that conflicts with law or this
Indenture, that the Trustee determines may be unduly prejudicial to the rights
of another Debentureholder, or that may involve the Trustee in personal
liability; provided that the Trustee may take any other action deemed proper by
the Trustee which is not inconsistent with such direction.

SECTION 8.6   Limitation on Suits.
              -------------------

          A Debentureholder may not pursue any remedy with respect to this
Indenture or the Debentures (except actions for payment of overdue principal or
premium, if any, or interest or for the conversion of the Debentures pursuant to
Article 4) unless:

          (1) the Holder gives to the Trustee written notice of a continuing
     Event of Default;

          (2) the Holders of at least 2.5 % in principal amount of the
     Debentures then outstanding Debentures make a written request to the
     Trustee to pursue the remedy;

          (3) such Holder or Holders offer to the Trustee indemnity satisfactory
     to the Trustee against any loss, liability or expense;

          (4) the Trustee does not comply with the request within 60 days after
     receipt of the request and the offer of indemnity; 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 Debentures then outstanding.

          A Debentureholder may not use this Indenture to prejudice the rights
of another Debentureholder or to obtain a preference or priority over such other
Debentureholder.

SECTION 8.7   Rights of Holders to Receive Payment.
              ------------------------------------

          Notwithstanding any other provision of this Indenture, the right of
any Holder of a Debenture to receive payment of the principal of and interest on
the Debenture, on or after the respective due dates expressed in the Debenture,
or to bring suit for the enforcement of any such payment on or after such
respective dates, or to convert the Debenture in accordance with the terms
hereof, is absolute and unconditional and shall not be impaired or affected
without the consent of the Holder.

SECTION 8.8   Collection Suit by Trustee.
              --------------------------

          If an Event of Default in the payment of principal or interest
specified in Section 8.1(1) or (2) occurs and is continuing, the Trustee may
recover judgment in its own name and as trustee of an express trust against the
Company or another obligor on the Debentures for the whole amount of principal
and accrued interest remaining unpaid, together with interest on overdue
principal and, to the extent that payment of such interest is lawful, interest
on overdue installments of interest, in each case at the rate per annum borne by
the Debentures and such

                                       39
<PAGE>

further amount 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.

SECTION 8.9   Trustee May File Proofs of Claim.
              --------------------------------

          The Trustee may file such proofs of claim and 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 and counsel) and the
Debentureholders allowed in any judicial proceedings relative to the Company (or
any other obligor on the Debentures), its creditors or its property and shall be
entitled and empowered to collect and receive any monies or other property
payable or deliverable on any such claims and to distribute the same, and any
Custodian in any such judicial proceeding is hereby authorized by each
Debentureholder 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
Debentureholders, to pay to the Trustee any amount due to it for the reasonable
compensation, expenses, disbursements and advances of the Trustee, its agents
and counsel, and any other amounts due the Trustee under Section 9.7, and to the
extent that such payment for the reasonable compensation, expenses,
disbursements and advances in any such proceedings shall be denied for any
reason, payment of the same shall be secured by a lien on, and shall be paid out
of, any and all distributions, dividends, monies, securities and other property
which the Debentureholders may be entitled to receive in such proceedings,
whether in liquidation or under any plan of reorganization or arrangement or
otherwise.  Nothing herein contained shall be deemed to authorize the Trustee to
authorize or consent to or the Trustee to authorize or accept or adopt on behalf
of any Debentureholder any plan of reorganization, arrangement, adjustment or
composition affecting the Debentures or the rights of any Holder thereof, or to
authorize the Trustee to vote in respect of the claim of any Debentureholder in
any such proceeding.

SECTION 8.10   Priorities.
               ----------

          If the Trustee collects any money pursuant to this Article 8, it shall
pay out the money in the following order:

          First, to the Trustee for amounts due under Section 9.7;

          Second, to the holders of Senior Indebtedness to the extent required
by Article 5;

          Third, to Debentureholders for amounts due and unpaid on the
     Debentures for principal and interest, ratably, without preference or
     priority of any kind, according to the amounts due and payable on the
     Debentures for principal and interest, respectively; and

          Fourth, to the Company.

          The Trustee may fix a record date and payment date for any payment to
the Debentureholders pursuant to this Section 8.10.

                                       40
<PAGE>

SECTION 8.11   Undertaking for Costs.
               ---------------------

          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, a court in its discretion may require the filing by any party
litigant in the suit of an undertaking to pay the costs of the suit, and the
court in its discretion may assess reasonable costs, including reasonable
attorneys' fees, against any party litigant in the suit, having due regard to
the merits and good faith of the claims or defense made by the party litigant.
This Section 8.11 does not apply to a suit made by the Trustee, a suit by a
Holder pursuant to Section 8.7, or a suit by Holders of more than 10% in
principal amount of the Debentures then outstanding.

                                       41
<PAGE>

                                   ARTICLE 9

                                    TRUSTEE

 SECTION 9.1  Duties of Trustee.
              -----------------

          (a) If an Event of Default has occurred and is continuing, the
Trustee shall exercise such of the rights and powers vested in it by this
Indenture and use the same degree of care and skill, in their exercise as a
prudent person would exercise or use under the circumstances in the conduct of
his own affairs.

          (b) Except during the continuance of an Event of Default:

          (1) the Trustee need perform only those duties as are specifically set
     forth in this Indenture and no others; and

          (2) in the absence of bad faith on its part, the Trustee may
     conclusively rely, as to the truth of the statements and the correctness of
     the opinions expressed therein, upon certificates or opinions furnished to
     the Trustee and conforming to the requirements of this Indenture.  The
     Trustee, however, shall examine the certificates and opinions to determine
     whether or not they conform to the requirements of this Indenture.

          (c) The Trustee may not be relieved from liability for its own
negligent action, its own negligent failure to act, or its own willful
misconduct, except that:

          (1) this paragraph does not limit the effect of paragraph (b) of this
     Section 9.1;

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

          (3) the Trustee shall not be liable with respect to any action it
     takes or omits to take in good faith in accordance with a direction
     received by it pursuant to Section 8.5.

          (d) The Trustee may refuse to perform any duty or exercise any right
or power unless it receives indemnity satisfactory to it against any loss,
liability, expense or fee.

          (e) Every provision of this Indenture that in any way relates to the
Trustee is subject to paragraphs (a), (b), (c) and (d) of this Section 9.1.

          (f) The Trustee shall not be liable for interest on any money received
by it except as the Trustee may agree in writing with the Company.  Money held
in trust by the Trustee need not be segregated from other funds except to the
extent required by law.



SECTION 9.2   Rights of Trustee.
               -----------------


                                      42
<PAGE>

          Subject to Section 9.1:

          (a) The Trustee may rely on any document believed by it to be genuine
and to have been signed or presented by the proper person.  The Trustee need not
investigate any fact or matter stated in the document.

          (b) Before the Trustee acts or refrains from acting, it may require an
Officers' Certificate or an Opinion of Counsel, which shall conform to Section
12.4(b).  The Trustee shall not be liable for any action it takes or omits to
take in good faith in reliance on such Certificate or Opinion.

          (c) The Trustee may act through its agents and shall not be
responsible for the misconduct or negligence of any agent appointed with due
care.

          (d) The Trustee shall not be liable for any action it takes or omits
to take in good faith which it believes to be authorized or within its rights or
powers.

          (e) The Trustee may consult with counsel and the advice or opinion of
such counsel as to matters of law that shall be full and complete authorization
and protection in respect of any action taken, omitted or suffered by it
hereunder in good faith and in accordance with the advice or opinion of such
counsel.

 SECTION 9.3   Individual Rights of Trustee.
               ----------------------------

          The Trustee in its individual or any other capacity may become the
owner or pledgee of Debentures and may otherwise deal with the Company or an
affiliate of the Company with the same rights it would have if it were not
Trustee.  Any Agent may do the same with like rights.  However, the Trustee is
subject to Sections 9.10 and 9.11.

 SECTION 9.4   Trustee's Disclaimer.
               --------------------

          The Trustee makes no representation as to the validity or adequacy of
this indenture or the Debentures, it shall not be accountable for the Company's
use of the proceeds from the Debentures, and it shall not be responsible for any
statement in the Debentures other than its certificate of authentication.

 SECTION 9.5   Notice of Default or Events of Default.
               --------------------------------------

          If a default or an Event of Default occurs and is continuing and if it
is known to the Trustee, the Trustee shall mail to each Debentureholder notice
of the default or Event of Default within 90 days after it occurs.  Except in
the case of a default or an Event of Default in payment of the principal of or
premium, if any, or interest on any Debenture, the Trustee may withhold the
notice if the Trustee in good faith determines that withholding the notice is in
the interest of Debentureholders.

 SECTION 9.6   Reports by Trustee to Holders.
               -----------------------------


                                      43
<PAGE>

          If such report is required by TIA (S) 313, within 60 days after each
May 15 beginning with the May 15 following the date of this Indenture, the
Trustee shall mail to each Debentureholder a brief report dated as of such May
15 that complies with TIA (S) 313(a).  The Trustee also shall comply with TIA
(S) 313(b)(2) and (c).

          A copy of each report at the time of its mailing to the
Debentureholders shall be mailed to the Company and filed with the SEC and each
stock exchange, if any, on which the securities are listed.  The Company shall
notify the Trustee whenever the Debentures become listed on any stock exchange
and any changes in the stock exchanges on which the Debentures are listed.

 SECTION 9.7   Compensation and Indemnity.
               --------------------------

          The Company shall pay to the Trustee from time to time reasonable
compensation for its services (which compensation shall not be limited by any
provision of law in regard to the compensation of a trustee of an express
trust).  The Company shall reimburse the Trustee upon request for all reasonable
disbursements, expenses and advances incurred or made by it.  Such expenses may
include the reasonable compensation, disbursements and expenses of Trustee's
agents and counsel.

          The Company shall indemnify the Trustee for, and hold it harmless
against, any loss, liability or expense incurred by it in connection with its
duties under this Indenture or any action or failure to act as authorized or
within the discretion or rights or powers conferred upon the Trustee hereunder.
The Trustee shall notify the Company promptly of any claim asserted against the
Trustee for which it may seek indemnity.  The Company shall defend the claim and
the Trustee shall cooperate in the defense.  The Trustee may have separate
counsel and the company shall pay the reasonable fees and expenses of such
counsel.  The Company need not pay for any settlement made without its written
consent.

          The Company need not reimburse the Trustee for any expense or
indemnify it against any loss or liability incurred by it through its negligence
or bad faith.

          To secure the Company's payment obligations in this Section, the
Trustee shall have a senior claim to which the Debentures are hereby made
subordinate on all money or property held or collected by the Trustee, except
such money or property held in trust to pay the principal of and interest on
particular Debentures.  The obligations of the Company under this Section 9.7 to
compensate or indemnify the Trustee and to pay or reimburse the Trustee for
expenses, disbursements and advances shall be secured by a lien prior to that of
the Debentures upon all property and funds held or collected by the Trustee as
such except funds held in trust for the benefit of the Holders of particular
Debentures.  The obligation of the Company under this Section 9.7 shall survive
the satisfaction and discharge of this Indenture.

          When the Trustee incurs expenses or renders services after an Event of
Default specified in Section 8.1(5) or (6) occurs, the expenses and the
compensation for the services are intended to constitute expenses of
administration under any Bankruptcy Law.

 SECTION 9.8   Replacement of Trustee.
               ----------------------


                                      44
<PAGE>

          The Trustee may resign by so notifying the Company.  The Holders of a
majority in principal amount of the Debentures then outstanding may remove the
Trustee by so notifying the Trustee and may appoint a successor Trustee with the
Company's written consent.  The Company may remove the Trustee if:

               (1) the Trustee fails to comply with Section 9.10;

               (2) the Trustee is adjudged a bankrupt or an insolvent;

               (3) a receiver or other public officer takes charge of the
     Trustee or its property; or

               (4) the Trustee becomes incapable of acting.

          If the Trustee resigns or is removed or if a vacancy exists in the
office of Trustee for any reason, the Company shall promptly appoint a successor
Trustee.

          If a successor Trustee does not take office within 45 days after the
retiring Trustee resigns or is removed, the retiring Trustee, the Company or the
Holders of 10% in principal amount of the Debentures then outstanding may
petition any court of competent jurisdiction for the appointment of a successor
Trustee.

          If the Trustee falls to comply with Section 9.10, any Debentureholder
may petition any court of competent jurisdiction for the removal of the Trustee
and the appointment of a successor Trustee.

          A successor Trustee shall deliver a written acceptance of its
appointment to the retiring Trustee and to the Company.  Immediately after that,
the retiring Trustee shall transfer all property held by it as Trustee to the
successor Trustee and be released from its obligations (exclusive of any
liabilities Trustee may have incurred while acting as Trustee) hereunder, the
resignation or removal of the retiring Trustee shall become effective, and the
successor Trustee shall have all the rights, powers and duties of the Trustee
under this Indenture.  A successor Trustee shall mall notice of its succession
to each Debentureholder.

          Notwithstanding replacement of the Trustee pursuant to this Section
9.8, the Company's obligations under Section 9.7 hereof shall continue for the
benefit of the retiring Trustee.

 SECTION 9.9   Successor Trustee by Merger, etc.
               ---------------------------------

          If the Trustee consolidates with, merges or converts into, or
transfers all or substantially all of its corporate trust assets to, another
corporation, the resulting, surviving or transferee corporation without any
further act shall be the successor Trustee, provided such transferee corporation
shall qualify and be eligible under Section 9.10.

SECTION 9.10   Eligibility; Disqualification.
               -----------------------------

                                      45
<PAGE>

          This Indenture shall always have a Trustee who satisfies the
requirements of paragraphs (1), (2) and (5) of TIA (S) 310.  If at any tune the
Trustee shall cease to satisfy any such requirements, it shall resign
immediately in the manner and with the effect specified in this Article Nine.
The Trustee shall be subject to the provisions of TIA (S) 310(b).  Nothing
herein shall prevent the Trustee from filing with the SEC the application
referred to in the penultimate paragraph of TIA (S) 310(b).

 SECTION 9.11  Preferential Collection of Claims Against Company.
               -------------------------------------------------

          The Trustee shall comply with TIA (S) 311(a), excluding any creditor
relationship listed in TIA (S) 311(b).  A trustee who has resigned or been
removed shall be subject to TIA (S) 311(a) to the extent indicated therein.


                                      46
<PAGE>

                                   ARTICLE 10

                    SATISFACTION AND DISCHARGE OF INDENTURE

 SECTION 10.1  Termination of Company's Obligations.
               ------------------------------------

          The Company may terminate all of its obligations under the Debentures
and this Indenture (except those obligations referred to in the immediately
succeeding paragraph) if all of the Debentures previously authenticated and
delivered (other than destroyed, lost or stolen Debentures which have been
replaced or paid or Debentures for whose payment money has theretofore been held
in trust and thereafter repaid to the Company, as provided in Section 10.3) have
been delivered to the Trustee for cancellation and the Company has paid all sums
payable by it hereunder, or if the Company irrevocably deposits in trust with
the Trustee money or U.S. Government Obligations maturing as to principal and
interest in such amounts and at such times as are sufficient without
consideration of any reinvestment of such interest, to pay the principal of and
interest on the Debentures then outstanding to maturity or to the date fixed for
redemption and to pay all other sums payable by it hereunder.  The Company may
make an irrevocable deposit pursuant to this Section 10.1 only if at such time
it is not prohibited from doing so under the provisions of Article 5 and the
Company shall have delivered to the Trustee and any such Paying Agent an
Officers' Certificate to that effect and that all other conditions to such
deposit have been complied with.

          The Company's obligations in paragraph 13 of the Debentures, in
Sections 2.3, 2.4, 2.5, 2.6, 2.7, 2.11, 6.1, 6.3, 9.7, 9.8 and 10.4, and in
Article 4 shall survive until the Debentures are no longer outstanding.
Thereafter, the Company's obligations in such paragraph 13 and in Section 9.7
shall survive.

          After such irrevocable deposit, the Trustee upon request shall
acknowledge in writing the discharge of the Company's obligations under the
Debentures and this Indenture, except for those surviving obligations specified
above.

          "U.S. Government Obligations" means direct non-callable obligations
of, or non-callable obligations guaranteed by, the United States of America for
the payment of which guarantee or obligation the full faith and credit of the
United States is pledged.

 SECTION 10.2  Application of Trust Money.
               --------------------------

          The Trustee or the Paying Agent shall hold in trust, for the benefit
of the Holders, money or U.S. Government Obligations deposited with it pursuant
to Section 10.1, and shall apply the deposited money and the money from U.S.
Government Obligations in accordance with this Indenture to the payment of the
principal of and interest on the Debentures.  Money and U.S. Government
Obligations so held in trust shall not be subject to the subordination
provisions of Article 5.


                                      47
<PAGE>

 SECTION 10.3  Repayment to Company.
               --------------------

          Subject to Section 10.1, the Trustee and the Paying Agent shall
promptly pay to the Company upon request any excess money or U.S. Government
Obligations held by them at any time.

          The Trustee and the Paying Agent shall pay to the Company upon request
any money held by them for the payment of principal or interest that remains
unclaimed for two years after a right to such money has matured; provided,
however, that the Trustee or such Paying Agent, before being required to make
any such payment, may at the expense of the Company cause to be published once
in a newspaper of general circulation in the City of New York or mail to each
Holder entitled to such money notice that such money remains unclaimed and that
after a date specified therein, which shall be at least 30 days from the date of
such publication or mailing, any unclaimed balance of such money then remaining
will be repaid to the Company. After payment to the Company, Debentureholders
entitled to money must look to the Company for payment as general creditors
unless otherwise prohibited by law.

 SECTION 10.4  Reinstatement.
               -------------

          If the Trustee or the Paying Agent is unable to apply any money or
U.S. Government Obligations in accordance with Section 10.1 by reason of any
legal proceeding or by reason of any order or judgment of any court or
governmental authority enjoining, restraining or otherwise prohibiting such
application, the Company's obligations under this Indenture and the Debentures
shall be revived and reinstated as though no deposit had occurred pursuant to
Section 10.1 until such time as the Trustee or Paying Agent is permitted to
apply all such money or U.S. Government Obligations in accordance with Section
10.1; provided, however, that if the Company has made any payment of the
principal of or interest on any Debentures because of the reinstatement of its
obligations, the Company shall be subrogated to the rights of the Holders of
such Debentures to receive any such payment from the money or U.S. Government
Obligations held by the Trustee or the Paying Agent.


                                      48
<PAGE>

                                   ARTICLE 11

                      AMENDMENTS, SUPPLEMENTS AND WAIVERS

 SECTION 11.1  Without Consent of Holders.
               --------------------------

          The Company and the Trustee may amend or supplement this Indenture or
the Debentures without notice to or consent of any Debentureholder:

          (1) to comply with Sections 6.4 and 7.1;

          (2) to provide for uncertificated Debentures in addition to or in
     place of certificated Debentures;

          (3) to cure any ambiguity, defect or inconsistency, or to make any
     other change that does not adversely affect the rights of any
     Debentureholder; or

          (4) to comply with the provisions of the TIA.

 SECTION 11.2  With Consent of Holders.
               -----------------------

          The Company and the Trustee may amend or supplement this Indenture or
the Debentures without notice to any Debentureholder but with the written
consent of the Holders of a majority of the Debentures then outstanding.  The
Holders of a majority in principal amount of the Debentures then outstanding may
waive compliance in a particular instance by the Company with any provision of
this Indenture or the Debentures without notice to any Debentureholder. Subject
to Section 11.4, without the written consent of each Debentureholder affected,
however, an amendment, supplement or waiver, including a waiver pursuant to
Section 8.4, may not:

          (1) extend the stated maturity of the Debentures;

          (2) reduce the rate of or extend the time for payment of interest on
              the Debentures;

          (3) reduce the principal amount or premium, if any, on the Debentures;

          (4) impair the rights of any holder of the Debentures to institute
              suit for payment thereof;

          (5) change the currency in which the Debentures are payable;

          (6) impair the right of any holder to convert the Debentures into
              cash, securities or other assets;

          (7) modify the subordination provisions set forth herein in a manner
              adverse to the holders of the Debentures;

                                      49
<PAGE>

          (8) impair the rights of holders to cause the Company to repurchase
              the Debentures upon a Fundamental Change;

          (9) reduce the percentage of Debentures, the holders of which must
              consent to any such modification.

          It shall not be necessary for the consent of the Holders under this
Section to approve the particular form of any proposed amendment, supplement or
waiver, but it shall be sufficient if such consent approves the substance
thereof.

          After an amendment, supplement or waiver under this Section becomes
effective, the Company shall mail to the Holders affected thereby a notice
briefly describing the amendment, supplement or waiver.  Any failure of the
Company to mail such notice, or any defect therein, shall not, however, in any
way impair or affect the validity of any such amendment, supplement or waiver.

          An amendment under this Section 11.2 may not make any change that
adversely affects the rights under Article 5 of any holder of an issue of Senior
Indebtedness unless the holders of that issue, pursuant to its terms, consent to
the change.

 SECTION 11.3  Compliance with Trust Indenture Act.
               -----------------------------------

          Every amendment to or supplement of this Indenture or the Debentures
shall comply with the TIA as in effect at the date of such amendment or
supplement.

 SECTION 11.4  Revocation and Effect of Consents.
               ---------------------------------

          Until an amendment, supplement or waiver becomes effective, a consent
to it by a Holder is a continuing consent by the Holder and every subsequent
Holder of a Debenture or portion of a Debenture that evidences the same debt as
the consenting Holder's Debenture, even if notation of the consent is not made
on any Debenture.  However, any such Holder or subsequent Holder may revoke the
consent as to his Debenture or portion of a Debenture if the Trustee receives
the notice of revocation before the date the amendment, supplement or waiver
becomes effective.

          After an amendment, supplement or waiver becomes effective, it shall
bind every Debentureholder, unless it makes a change described in any of clauses
(1) through (8) of Section 11.2.  In that case the amendment, supplement or
waiver shall bind each Holder of a Debenture who has consented to it and every
subsequent Holder of a Debenture or portion of a Debenture that evidences the
same debt as the consenting Holder's Debenture.

 SECTION 11.5  Notation On or Exchange of Debentures.
               -------------------------------------

          If an amendment, supplement or waiver changes the terms of a
Debenture, the Trustee may require the Holder of the Debenture to deliver it to
the Trustee.  The Trustee may place an appropriate notation on the Debenture
about the changed terms and return it to the Holder.  Alternatively, if the
Company or the Trustee so determines, the Company in exchange


                                      50
<PAGE>

for the Debenture shall issue and the Trustee shall authenticate a new Debenture
that reflects the changed terms.

 SECTION 11.6  Trustee to Sign Amendments, etc.
               --------------------------------

          The Trustee shall sign any amendment or supplement authorized pursuant
to this Article 11 if the amendment or supplement does not adversely affect the
rights, duties, liabilities or immunities of the Trustee.  If it does, the
Trustee may but need not sign it.  In signing or refusing to sign such amendment
or supplement, the Trustee shall be entitled to receive and, subject to Section
9.1 shall be fully protected in relying upon, an Opinion of Counsel stating that
such amendment or supplement is authorized or permitted by this Indenture.  The
Company may not sign an amendment or supplement until the Board of Directors
approves it.

                                      51

<PAGE>

                                   ARTICLE 12

                                 MISCELLANEOUS

 SECTION 12.1  Trust Indenture Act Controls.
               ----------------------------

          If any provision of this Indenture limits, qualifies or conflicts with
the duties imposed by any of Sections 310 to 317, inclusive, of the TIA through
operation of Section 318(c) thereof, such imposed duties shall control.

 SECTION 12.2  Notices.
               -------

          Any notice or communication shall be given in writing and delivered in
person or mailed by certified or registered mail, return receipt requested,
addressed as follows:

               if to the Company:

               Mobile Telecommunication Technologies Corp.
               200 South Lamar Street
               Security Centre, South Building
               Jackson, Mississippi 39201

               Attention:     Vice President-Finance
               if to the Trustee:



Such notices or communications shall be effective when received.

          The Company or the Trustee by notice to the other may designate
additional or different addresses for subsequent notices or communications.

          Any notice or communication mailed to a Debentureholder shall be
mailed by first-class mail to him at his address shown on the register kept by
the Registrar.

          Failure to mail a notice or communication to a Debentureholder or any
defect in it shall not affect its sufficiency with respect to other
Debentureholders.  If a notice or communication to a Debentureholder is mailed
in the manner provided above, it is duly given, whether or not the addressee
receives it.

 SECTION 12.3  Communications by Holders with Other Holders.
               --------------------------------------------

     The Debentureholders may communicate pursuant to TIA (S) 312(b) with other
Debentureholders with respect to their rights under this Indenture or the
Debentures.  The Company, the Trustee, the Registrar and any other person shall
have the protection of TIA (S) 312(c).

                                      52
<PAGE>

 SECTION 12.4  Certificate and Opinion as to Conditions Precedent.
               --------------------------------------------------

          (a) Upon any request or application by the Company to the Trustee to
take any action under this Indenture, the Company shall furnish to the Trustee
at the request of the Trustee:

               (1) an Officers' Certificate stating that, in the opinion of the
          signers, all conditions precedent (including any covenants compliance
          with which constitutes a condition precedent), if any, provided for in
          this Indenture relating to the proposed action have been complied
          with; and

               (2) an Opinion of Counsel stating that, in the opinion of such
          counsel, all such conditions precedent (including any covenants
          compliance with which constitutes a condition precedent) have been
          complied with.

          (b) Each Officers' Certificate and Opinion of Counsel with respect to
compliance with a condition or covenant provided for in this Indenture (other
than annual certificates provided pursuant to Section 6.5 hereof) shall include:

               (1) a statement that the person making such certificate or
          opinion has read such covenant or condition;

               (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 such person, he has made
          such examination or investigation as is necessary to enable him to
          express an informed opinion as to whether or not such covenant or
          condition has been complied with; and

               (4) a statement as to whether or not, in the opinion of such
          person, such condition or covenant has been complied with; provided,
          however, that with respect to matters of fact an Opinion of Counsel
          may rely on an Officers' Certificate or certificates of public
          officials.

 SECTION 12.5  Record Date for Vote or Consent of Debentureholders.
               ---------------------------------------------------

          The Company (or, in the event deposits have been made pursuant to
Sections 6.4 or 10.1, the Trustee) may set a record date for purposes of
determining the identity of the Debentureholders entitled to vote or consent to
any action by vote or consent authorized or permitted under this Indenture,
which record date shall be the later of 10 days prior to the first solicitation
of such vote or consent or the date of the most recent list of Debentureholders
famished to the Trustee pursuant to Section 2.5 hereof prior to such
solicitation.  If a record date is fixed, those persons who were Holders of the
Debentures at such record date (or their duly designated proxies), and only
those persons, shall be entitled to take such action by vote or consent or to
revoke any vote or consent previously given, whether or not such persons
continue to be Holders after such record date.

                                      53

<PAGE>

SECTION 12.6   Rules by Trustee, Paying Agent, Registrar.
               -----------------------------------------

          The Trustee may make reasonable rules for action by or at a meeting of
Holders. The Registrar or the Paying Agent may make reasonable rules for its
functions.

 SECTION 12.7  Legal Holidays.
               --------------

          A "Legal Holiday" is a Saturday, a Sunday or a day on which state or
Federally chartered banking institutions in New York, New York or the city and
state where the Trustee's corporate trust operations are located, which
initially are Dallas, Texas, are not required to be open.  If a payment date is
a Legal Holiday at a place of payment, payment may be made at that place on the
next succeeding day that is not a Legal Holiday, and no interest shall accrue
for the intervening period.

 SECTION 12.8  Governing Law.
               -------------

          The laws of the State of New York shall govern this Indenture and the
Debentures without regard to principles of conflicts of law.

 SECTION 12.9  No Adverse Interpretation of Other Agreements.
               ---------------------------------------------

          This Indenture may not be used to interpret another indenture, loan or
debt agreement of the Company or a Subsidiary.  Any such indenture, loan or debt
agreement may not be used to interpret this Indenture.

 SECTION 12.10 No Recourse Against Others.
               --------------------------

          All liability described in paragraph l8 of the Debentures of any
director, officer, employee or stockholder, as such, of the Company is waived
and released.

 SECTION 12.11 Successors.
               ----------

          All agreements of the Company in this Indenture and the Debentures
shall bind its successor.  All agreements of the Trustee in this Indenture shall
bind its successor.

 SECTION 12.12 Multiple Counterparts.
               ---------------------

          The parties may sign multiple counterparts of this Indenture.  Each
signed counterpart shall be deemed an original, but all of them together
represent the same agreement.

 SECTION 12.13 Separability.
               ------------

          In case any provision in this Indenture or in the Debentures 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 12.14 Table of Contents, Headings, etc.
               ---------------------------------

                                      54
<PAGE>

          The table of contents, cross-reference sheet and headings of the
Articles and Sections of this Indenture have been inserted for convenience of
reference only, are not to be considered a part hereof, and shall in no way
modify or restrict any of the terms or provisions hereof.

                                      55
<PAGE>

                                   SIGNATURES

          IN WITNESS WHEREOF, the parties hereto have hereunto set their hands
as of the _____ day of _______________.


                  MOBILE TELECOMMUNICATION TECHNOLOGIES CORP.

                              By:
                                 ------------------------------
                                 Name:
                                 Title:



[SEAL]

Attest:


- -------------------------
Secretary



                              [                    ]
                               --------------------
                              as Trustee

                              By:
                                 ------------------------------
                              Title:
                                    ---------------------------



[SEAL]

Attest:



- ------------------
Name:
Title:


                                      56
<PAGE>

                                                                       EXHIBIT A

                                                             [FACE OF DEBENTURE]
Number

                  MOBILE TELECOMMUNICATION TECHNOLOGIES CORP.

4.5 % Convertible Subordinated Debentures due 2003

          MOBILE TELECOMMUNICATION TECHNOLOGIES CORP., a Delaware corporation,
promises to pay to          or registered assigns the principal sum of
                  ----------                                          ---------
Dollars on October 15, 2003.

Interest Payment Dates:                    and
                             -------------     ---------------
Record Dates:                              and
                             -------------     ---------------

          Additional provisions of this Debenture are set forth on the other
side of this Debenture.

          Dated:
                              MOBILE TELECOMMUNICATION TECHNOLOGIES CORP.

                              By:
                                 -----------------------------------
                                 Name:
                                 Title:


[SEAL]

Attest:

By:
   -----------------------
       Secretary

Certificate of Authentication:

This is one of the Debentures referred
to in the within mentioned Indenture.



as Trustee,

By:
   -----------------------
   Authorized Signatory



                                      A-1
<PAGE>

                                                                  [REVERSE SIDE]

                  MOBILE TELECOMMUNICATION TECHNOLOGIES CORP.

               4.5 % Convertible Subordinated Debentures due 2003

          THIS DEBENTURE HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
          1933, AS AMENDED (THE "SECURITIES ACT").  THE HOLDER HEREOF, BY
          PURCHASING THIS DEBENTURE, AGREES FOR THE BENEFIT OF MOBILE
          TELECOMMUNICATION TECHNOLOGIES CORP.  (THE "COMPANY") THAT THIS
          DEBENTURE MAY BE RESOLD, PLEDGED OR OTHERWISE TRANSFERRED ONLY (1) TO
          THE COMPANY (UPON CONVERSION, EXCHANGE OR REDEMPTION THEREOF OR
          OTHERWISE), (2) SO LONG AS THIS DEBENTURE IS ELIGIBLE FOR RESALE
          PURSUANT TO RULE 144A UNDER THE SECURITIES ACT ("RULE 144A"), TO A
          PERSON WHOM THE SELLER REASONABLY BELIEVES IS A QUALIFIED
          INSTITUTIONAL BUYER WITHIN THE MEANING OF RULE 144A, PURCHASING FOR
          ITS OWN ACCOUNT OR FOR THE ACCOUNT OF A QUALIFIED INSTITUTIONAL BUYER
          TO WHOM NOTICE IS GIVEN THAT THE RESALE, PLEDGE OR OTHER TRANSFER IS
          BEING MADE IN RELIANCE ON RULE 144A, (3) IN AN OFFSHORE TRANSACTION IN
          ACCORDANCE WITH REGULATION S UNDER THE SECURITIES ACT, BUT ONLY IN THE
          CASE OF A TRANSFER THAT IS EFFECTED BY THE DELIVERY TO THE TRANSFEREE
          OF DEFINITIVE DEBENTURES REGISTERED IN ITS NAME (OR ITS NOMINEE'S
          NAME) ON THE BOOKS MAINTAINED BY THE REGISTRAR, (4) PURSUANT TO AN
          EXEMPTION FROM REGISTRATION IN ACCORDANCE WITH RULE 144 (IF AVAILABLE)
          UNDER THE SECURITIES ACT, OR (5) PURSUANT TO AN EFFECTIVE REGISTRATION
          STATEMENT UNDER THE SECURITIES ACT, IN EACH CASE IN ACCORDANCE WITH
          ANY APPLICABLE SECURITIES LAWS OF ANY STATE OF THE UNITED STATES.

1.        Interest.
          --------

          Mobile Telecommunication Technologies Corp., a Delaware corporation
(the "Company"), promises to pay interest on the principal amount of this
Debenture at the rate per annum shown above.  The Company shall pay interest
semi-annually on April 15 and October 15 of each year, commencing April 15,
1994.  Interest on this Debenture will accrue from the most recent date to which
interest has been paid or, if no interest has been paid, from the date of first
issuance of the Debentures under the Indenture (as defined below); provided
that,


                                      A-2
<PAGE>

if there is not existing default in the payment of interest, and if this
Debenture is authenticated between a record date referred to on the face hereof
and the next succeeding interest payment date, interest shall accrue from such
interest payment date.  Interest will be computed on the basis of a 360-day year
of twelve 30-day months.

2.        Method of Payment.
          -----------------

          The Company will pay interest on this Debenture (except defaulted
interest) to the person who is the registered holder of this Debenture at the
close of business on the April 1 and October 1 next preceding the interest
payment date.  The holder must surrender this Debenture to the Paying Agent to
collect payment of principal.  The Company will pay principal and interest in
money of the United States that at the time of payment is legal tender for
payment of public and private debts.  The Company, however, may pay principal
and interest by its check payable in such money.  It may mail an interest check
to the holder's registered address.

3.        Paying Agent, Registrar and Conversion Agent.
          --------------------------------------------

          Initially,            (the "Trustee") will act as Paying Agent,
Registrar and Conversion Agent.  The Company may change any Paying Agent,
Registrar or Conversion Agent without notice to the holder.  The Company or any
of its Subsidiaries may act as Paying Agent, Registrar or Conversion Agent.

4.        Indenture, Limitations.
          ----------------------

          This Debenture is one of a duly authorized issue of Debentures of the
Company designated as its 4.5% Convertible Subordinated Debentures due 2003 (the
"Debentures"), issued under an Indenture dated as of        (the "Indenture"),
between the Company and the Trustee.  The terms of this Debenture include those
stated in the Indenture and those made part of the Indenture by reference to the
Trust Indenture Act of 1939 (15 U.S.C. (S)(S) 77aaa-77bbb), as amended by the
Trust Indenture Reform Act of 1990 and as in effect on the date of the
Indenture.  This Debenture is subject to all such terms, and the holder of this
Debenture is referred to the Indenture and said Act for a statement of them. The
Debentures are subordinated unsecured obligations of the Company limited to up
to $____________.

5.        Optional Redemption.
          -------------------

          The Debentures may be redeemed, at the Company's option, on and after
October 25, 1996, in whole or in part at the following redemption prices
(expressed as percentages of principal amount), plus accrued interest to the
date fixed for redemption, if redeemed during the 12-month period beginning
October 15 (October 25 for 1996) of the year indicated:

<TABLE>
<CAPTION>
               Year                   Redemption Price
               ----                   ----------------
               <S>                    <C>
               1996                        103.0%
               1997                        102.5%
               1998                        102.0%
               1999                        101.5%
               2000                        101.0%
               2001                        100.5%
               2002 and thereafter         100.0%
</TABLE>

                        A-3
<PAGE>

6.    Notice of Redemption.
      ---------------------

          Notice of redemption will be mailed by first class mail at least 30
days but not more than 60 days before the redemption date to each Holder of
record to be redeemed at his registered address.  Debentures in denominations
larger than $1,000 may be redeemed in part, but only in whole multiples of
$1,000.  On and after the redemption date, subject to the deposit with the
Paying Agent of funds sufficient to pay the redemption price, interest ceases to
accrue on or portions of them called for redemption.

7.    Purchase of at Option of Holder Upon a Fundamental Change.
      ---------------------------------------------------------

          At the option of the Holder and subject to the terms and conditions of
the Indenture, the Company shall become obligated to purchase all or any part
specified by the Holder (so long as the principal amount of such part is $1,000
or an integral multiple thereof) of the Debentures held by such Holder on the
date that is not less than 70 nor more than 110 days after a Fundamental Change
as defined in the Indenture.  The repurchase price shall be payable, at the
option of the Company, in cash or marketable stock based on its then fair market
value, or a combination thereof.  The Holder shall have the right to withdraw
any Fundamental Change Purchase Notice by delivering a written notice of
withdrawal to the Paying Agent in accordance with the term of the Indenture.
The obligation of the Company to pay the Fundamental Change Purchase Price will
be subject to the terms of its then-existing Bank Credit Agreement or other
agreements relating to borrowings which constitute Senior Indebtedness.

8.    Conversion.
      ----------

          A Holder of a Debenture may convert it into shares of Common Stock of
the Company at any time prior to maturity, except that if the Debenture is
called for redemption, the conversion right will terminate at the close of
business on the third Business Day immediately preceding the redemption date.
The initial conversion price is $45.00 per share, subject to adjustment under
certain circumstances.  The number of shares issuable upon conversion of a
Debenture is determined by dividing the principal amount converted by the
conversion price in effect on the conversion date.  Upon conversion, no
adjustment for interest or dividends will be made.  No fractional shares will be
issued upon conversion; in lieu thereof, an amount will be paid in cash based
upon the market price (as defined) of the Common Stock on the last trading day
prior to the date of conversion.

          To convert a Debenture, a Holder must (a) complete and sign the
conversion notice set forth below, (b) surrender the Debenture to a Conversion
Agent, (c) furnish appropriate endorsements or transfer documents if required by
the Registrar or the Conversion Agent and (d) pay any transfer or similar tax,
if required.  If a Holder surrenders a Debenture for conversion between the
record date for the payment of an installment of interest and the next interest
payment date, the Debenture must be accompanied by payment of an amount equal to
the interest payable on such interest payment date on the principal amount of
the Debenture or


                                      A-4
<PAGE>

portion thereof then converted.  A Holder may convert a portion
of a Debenture equal to $1,000 or any integral multiple thereof.

          A Debenture in respect of which a Holder had delivered a Fundamental
Change Purchase Notice exercising the option of such Holder to require the
Company to purchase such Debenture may be converted only if the notice of
exercise is withdrawn as provided above and in accordance with the terms of the
Indenture.

9.    Subordination.
      -------------

          The indebtedness evidenced by the Debentures is, to the extent and in
the manner provided in the Indenture, subordinate and junior in right of payment
to the prior payment in full of all Senior Indebtedness of the Company, as
defined in the Indenture.  Senior Indebtedness must be paid before any payment
may be made to any Holder of the Debentures. Any Holder by accepting this
Debenture agrees to and shall be bound by such subordination revisions and
authorizes the Trustee to give them effect.

          In addition to all other rights of Senior Indebtedness described in
the Indenture, the Senior Indebtedness shall continue to be Senior Indebtedness
and entitled to the benefits of the subordination provisions irrespective of any
amendment, modification or waiver of any terms of any instrument relating to the
Senior Indebtedness or any extension or renewal of the Senior Indebtedness.

10.   Denominations, Transfer, Exchange.
      ---------------------------------

          The Debentures are in registered form without coupons in denominations
of $1,000 and integral multiples of $1,000.  A Holder may register the transfer
of or exchange Debentures in accordance with the Indenture.  The Registrar may
require a Holder, among other things, to furnish appropriate endorsements and
transfer documents and to pay any taxes or other governmental charges that may
be imposed by law or permitted by the Indenture.

11.   Persons Deemed Owners.
      ---------------------

          The registered holder of a Debenture may be treated as the owner
of it for all purposes.

12.   Unclaimed Money.
      ---------------

          If money for the payment of principal or interest remains unclaimed
for two years, the Trustee or Paying Agent will pay the money back to the
Company at its request. After that, Holders entitled to money must look to the
Company for payment.

13.   Amendment, Supplement, Waiver.
      -----------------------------

          Subject to certain exceptions, the Indenture or the Debentures may be
amended or supplemented with the consent of the Holders of 66-2/3% in principal
amount


                                      A-5
<PAGE>

of the Debentures then outstanding and any past default or compliance
with any provision may be waived in a particular instance with the consent of
the Holders of a majority in principal amount of the Debentures then
outstanding.  Without the consent of or notice to any Holder, the Company and
the Trustee may amend or supplement the Indenture or the Debentures to, among
other things, provide for uncertificated Debentures in addition to or in place
of certificated Debentures, or to cure any ambiguity, defect or inconsistency or
make any other change that does not adversely affect the rights of any Holder.

14.   Successor Corporation.
      ---------------------

          When a successor corporation assumes all the obligations of its
predecessor under the Debentures and the Indenture, the predecessor corporation
will be released from those obligations.

15.   Defaults and Remedies.
      ---------------------

          An Event of Default is: default for 30 days in payment of interest on
the Debentures; default in payment of principal on them; failure by the Company
for 30 days after notice to it to comply with any of its other agreements in the
Indenture or the Debentures; certain events of bankruptcy or insolvency of the
Company or' any of its subsidiaries; and certain defaults on other indebtedness.
If an Event of Default (other than as a result of certain events of bankruptcy
or insolvency), occurs and is continuing, the Trustee or the Holders of at least
2.5% in principal amount of the Debentures then outstanding may declare all
unpaid principal of and accrued interest to the date of acceleration on the
Debentures then outstanding to be due and payable immediately, all as and to the
extent provided in the Indenture.  If an Event of Default occurs as a result of
certain events of bankruptcy or insolvency, all unpaid principal of and accrued
interest on the Debentures then outstanding shall become due and payable
immediately without any declaration or other act on the part of the Trustee or
any Holder, all as and to the extent provided in the Indenture.  Holders may not
enforce the Indenture or the Debentures except as provided in the Indenture.
The Trustee may require indemnity satisfactory to it before it enforces the
Indenture or the Debentures.  Subject to certain limitations, Holders of a
majority in principal amount of the Debentures then outstanding may direct the
Trustee in its exercise of any trust or power.  The Trustee may withhold from
Holders notice of any continuing default (except a default in payment of
principal or interest) if it determines that withholding notice is in their
interests.  The Company is required to file periodic reports with the Trustee as
to the absence of default.

16.   Trustee Dealings with the Company.
      ---------------------------------

                                    , the Trustee under the Indenture, in its
          --------------------------
individual or any other capacity, may make loans to, accept deposits from, and
perform services for the Company or an Affiliate of the Company, and may
otherwise deal with the Company or an Affiliate of the Company, as if it were
not the Trustee.

17.   No Recourse Against Others.
      --------------------------

          A director, officer, employee or stockholder, as such, of the Company
shall not have any liability for any obligations of the Company under the
Debentures or the Indenture or for any claim based on, in respect or by reason
of, such obligations or their creation.


                                      A-6
<PAGE>

The Holder of this Debenture by accepting this Debenture waives and releases all
such liability. The waiver and release are part of the consideration for the
issue of this Debenture .

18.   Discharge Prior to Maturity.
      ---------------------------

          If the Company deposits with the Trustee or the Paying Agent money or
U.S. Government Obligations sufficient to pay the principal of and interest on
the Debentures to maturity, the Company will be discharged from the Indenture
except for certain Sections thereof.

19.   Authentication.
      --------------

          This Debenture shall not be valid until the Trustee or an
authenticating agent signs the certificate of authentication on the other side
of this Debenture.

20.   Abbreviations and Definitions.
      -----------------------------

          Customary abbreviations may be used in the name of a Holder or an
assignee, such as: TEN COM (= tenants in common), TEN ENT (= tenants by the
entireties), JT TEN (= joint tenants with right of survivorship and not as
tenants in common), CUST (= Custodian) and U/G/M/A (= Uniform Gifts to Minors
Act).

          All capitalized terms used in this Debenture and not specifically
defined herein are defined in the Indenture and are used herein as so defined.

21.   Indenture to Control.
      --------------------

          In the case of any conflict between the provisions of this Debenture
and the Indenture, the provisions of the Indenture shall control.

          The Company will furnish to any Holder, upon written request and
without charge, a copy of the Indenture.  Requests may be made to: Mobile
Telecommunication Technologies Corp., 200 South Lamar Street, Security Centre,
South Building, Jackson, Mississippi 39201, Attention: Secretary.

                                      A-7
<PAGE>

<TABLE>
<CAPTION>
ASSIGNMENT FORM                                                         CONVERSION NOTICE
<S>                                              <C>
To Assign this Debenture, fill in the form       To convert this Debenture into Common Stock of the Company,
 below:                                          check the box:
                                                                    [ ]
I or we assign and transfer this Debenture
 to                                              To convert only part of this Debenture, state the amount:

   --------------------------------------        ------------------------------------------------------
   --------------------------------------        ------------------------------------------------------
                                                 If you want the stock certificate made out in another person's
(Insert assignee's soc. sec. or tax I.D. no.)    name, fill in the form below:

- -----------------------------------------        ------------------------------------------------------
- -----------------------------------------        ------------------------------------------------------
- -----------------------------------------
- -----------------------------------------        (Insert the other person's soc. sec. or tax I.D. no.)

Print or type assignee's name, address           ------------------------------------------------------
 and zip code)                                   ------------------------------------------------------
                                                 ------------------------------------------------------
and irrevocably appoint                          ------------------------------------------------------
                                                 ------------------------------------------------------
- -----------------------------------------        (Print or type other person's name, address and zip code)
agent to transfer this Debenture on the
books of the Company.  The Agent may             Your Signature:                                      *
substitute another to act for him.               ------------------------------------------------------
                                                 (Sign exactly as your name appears on the other side of
Your Signature:                         *        this Debenture)
               --------------------------
                (Sign exactly as your                                                                 *
                name appears on the              ------------------------------------------------------
                other side of this               (Sign exactly as your name appears on the other side of
                Debenture)                       this Debenture)

                                       *         Date:
- ----------------------------------------              --------------------------------------------------
(Sign exactly as your name appears on
 the other side of this Debenture)               *Signature guaranteed by:

Date:                                            ------------------------------------------------------------
     -----------------------------------
                                                 By:
*Signature guaranteed by:                            --------------------------------------------------------

- ----------------------------------------         ------------------------------------------------------------
                                                 *The signature must be guaranteed by a bank, a trust company or
By:                                               a member firm of the New York Stock Exchange.
   -------------------------------------

*The signature must be guaranteed by a
 bank, a trust company or a member firm
 of the New York Stock Exchange.








</TABLE>

<PAGE>

                       OPTION OF HOLDER TO ELECT PURCHASE


          If you want to elect to have this Debenture purchased by the Company
pursuant to Section 6.10 of the Indenture, check the box:

                                                        [ ]

          If you want to elect to have only part of this Debenture purchased by
the Company pursuant to Section 6.10 of the Indenture, state the amount: $
                                                                          -----
Date:                             Your Signature:
                                                 ------------------------------
                                                  (Sign exactly as your name
                                                   appears on the other side
                                                   of this Debenture)

                                  Print Name:
                                             -----------------------------------


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