<PAGE>
Exhibit 4.3
UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE
DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("DTC"), TO NATURAL
MICROSYSTEMS CORPORATION OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE, OR
PAYMENT, AND ANY CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR
IN SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND
ANY PAYMENT IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN
AUTHORIZED REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE, OR OTHER USE HEREOF FOR
VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED
OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.
TRANSFERS OF THIS GLOBAL NOTE SHALL BE LIMITED TO TRANSFER IN WHOLE, BUT NOT IN
PART, TO NOMINEES OF DTC OR TO A SUCCESSOR THEREOF OR SUCH SUCCESSOR'S NOMINEE
AND TRANSFERS MADE IN ACCORDANCE WITH THE RESTRICTIONS SET FORTH IN THE
INDENTURE REFERRED TO ON THE REVERSE HEREOF.
NATURAL MICROSYSTEMS CORPORATION
Number R-1 $175,000,000
CUSIP No. 638882AA8
5% Convertible Subordinated Note Due 2005
Natural MicroSystems Corporation, a Delaware corporation, promises to
pay to Cede & Co. or registered assigns, the principal sum of One Hundred
Seventy-Five Million Dollars ($175,000,000) on October 15, 2005 and to pay
interest on the principal amount of this Note beginning the most recent date to
which interest has been paid or, if no interest has been paid, beginning October
11, 2000 at the rate of 5% per annum.
Interest Payment Dates: April 15 and October 15
Record Dates: April 1 and October 1
This Note is convertible at such times and as specified on the other
side of this Note. Additional provisions of this Note are set forth on the other
side of this Note.
<PAGE>
IN WITNESS WHEREOF, the Company has caused this 5% Convertible
Subordinated Note due 2005 to be signed by its duly authorized officers.
Dated: October 11, 2000 NATURAL MICROSYSTEMS CORPORATION
By: /s/ Robert P. Schechter
-----------------------------
Robert P. Schechter
Chairman of the Board, President,
and Chief Executive Officer
By: /s/ Robert E. Hult
---------------------------------
Robert E. Hult
Senior Vice President of Finance and
Operations, Chief Financial Officer,
and Treasurer
Dated: October 11, 2000
TRUSTEE'S CERTIFICATE OF AUTHENTICATION
This is one of the Securities of the series designated herein and
referred to in the within-mentioned Indenture as supplemented by a First
Supplemental Indenture.
STATE STREET BANK AND TRUST COMPANY,
as Trustee
By: /s/ David Ganss
-----------------------------------
Authorized Signatory
<PAGE>
[REVERSE OF NOTE]
NATURAL MICROSYSTEMS CORPORATION
5% Convertible Subordinated Note Due 2005
1. INTEREST.
Natural MicroSystems Corporation, a Delaware corporation (the
"Company"), promises to pay interest on the principal amount of this Note 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, 2001. Interest on the
Notes will accrue from the most recent date to which interest has been paid or,
if no interest has been paid, from October 11, 2000. 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 Note (except defaulted interest)
to the person who is the registered Holder of this Note at the close of business
on the April 1 and October 1 next preceding the interest payment date. The
Holder must surrender this Note 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, except that with respect to any Holder of Notes with an
aggregate principal amount equal to or in excess of $5 million, at the request
of such Holder in writing the Company shall pay interest on such Holder's Notes
by wire transfer in immediately available funds. It may mail an interest check
to the Holder's registered address.
3. PAYING AGENT, REGISTRAR AND CONVERSION AGENT.
Initially, State Street Bank and Trust Company (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 Note is one of a duly authorized issue of Notes of the Company
designated as its 5% Convertible Subordinated Notes Due 2005 (the "Notes"),
issued under an Indenture dated as of October 11, 2000 (the "Indenture") and a
First Supplemental Indenture dated as of October 11, 2000 (the "First
Supplemental Indenture"), between the Company and the Trustee. The terms of this
Note include those stated in the First Supplemental Indenture and in the
Indenture and those made part of the First Supplemental Indenture and the
Indenture by reference to the Trust Indenture Act of 1939 (15 U.S.C. ss.ss.
77aaa-77bbbb), as amended by the Trust Indenture Reform Act of 1990, as in
effect on the date hereof or, from and after the date that the First
Supplemental Indenture and the Indenture shall be qualified thereunder, as in
effect on such date. This Note is
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<PAGE>
subject to all such terms, and the Holder of this Note is referred to the First
Supplemental Indenture and the Indenture and said Act for a statement of them.
The Notes are subordinated unsecured obligations of the Company
initially limited to up to $175,000,000 aggregate principal amount plus an
additional principal amount not exceeding $26,250,000 in the aggregate as may be
issued upon the exercise by the Underwriters, in whole or in part, of the
Purchase Option.
5. OPTIONAL REDEMPTION.
At any time on and after October 16, 2003, and prior to maturity, if
the closing price of the Common Stock shall have exceeded 130% of the conversion
price then in effect for at least 20 trading days in the consecutive 30-trading
day period ending on the trading day prior to the date of mailing of a notice of
optional redemption, the Company may, at its option, redeem all or any part of
the Notes, upon mailing a notice of such redemption not less than thirty (30)
days before the date fixed for redemption to the Holders of Notes, at the
following optional redemption prices (expressed as percentages of the principal
amount):
If redeemed during the period beginning October 16, 2003 and ending on
October 14, 2004, at a redemption price of 102%, and if redeemed during the
period beginning October 15, 2004 and ending on October 15, 2005, at a
redemption price of 101%, together in the case of any such redemption with
accrued interest to the date of redemption, but any interest payment that is due
and payable on or prior to such date of redemption will be payable to the
Holders of such Notes, or one or more predecessor Notes, of record at the close
of business on the relevant record dates referred to on the face hereof, all as
provided in the First Supplemental Indenture and the Indenture.
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
Notes to be redeemed at his registered address. Notes 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 Notes
or portions of them called for redemption.
7. REPURCHASE OF NOTES AT OPTION OF HOLDER UPON A CHANGE IN CONTROL.
If at any time that Notes remain outstanding there shall have occurred
a Change in Control (as defined in the First Supplemental Indenture and in the
Indenture), at the option of the Holder and subject to the terms and conditions
of the First Supplemental Indenture and the Indenture, the Company shall become
obligated to repurchase 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
Notes held by such Holder on the Repurchase Date. The Holder shall have the
right to withdraw any Repurchase Notice by delivering a written notice of
withdrawal to the Paying Agent in accordance with the terms of the First
Supplemental Indenture and the Indenture. At
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<PAGE>
the option of the Company, the Repurchase Price may be paid in cash or, subject
to the fulfillment by the Company of the conditions set forth in Section 3.08(b)
of the First Supplemental Indenture, by delivery of shares of Common Stock, the
Adjusted Market Value of which shall be equal to the Repurchase Price.
8. CONVERSION.
At any time after 90 days following the latest date of original
issuance of the Notes and prior to the close of business on October 14, 2005, a
Holder of a Note may convert such Note into shares of Common Stock of the
Company; PROVIDED, HOWEVER, that if the Note is called for redemption, the
conversion right will terminate at the close of business on the third Business
Day before the redemption date of such Note (unless the Note is called for
redemption pursuant to Article 3 during the period commencing on October 16,
2003 and ending on (including) October 24, 2003 in which case the conversion
right shall terminate on the close of business on the first Business Day before
the redemption date or unless the Company shall default in making the redemption
payment when due, in which case the conversion right shall terminate at the
close of business on the date such default is cured and such Note is redeemed).
The initial conversion price is $63.125 per share, subject to adjustment under
certain circumstances as described in the First Supplemental Indenture and the
Indenture. The number of shares issuable upon conversion of a Note 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 current market price (as
defined in the First Supplemental Indenture and the Indenture) of the Common
Stock on the last trading day prior to the date of conversion.
To convert a Note, a Holder must (a) complete and sign the conversion
notice set forth below and deliver such notice to the Conversion Agent, (b)
surrender the Note to the Conversion Agent, if certificated, (c) furnish
appropriate endorsements and transfer documents if required by the Registrar or
the Conversion Agent, (d) pay any transfer or similar tax, if required and (e)
if the Note is held in book-entry form, complete and deliver to the Depositary
appropriate instructions pursuant to the Depositary's book-entry conversion
programs. If a Holder surrenders a Note for conversion between the record date
for the payment of an installment of interest and the next interest payment
date, the Note must be accompanied by payment of an amount equal to the interest
payable on such interest payment date on the principal amount of the Note or
portion thereof then converted; PROVIDED, HOWEVER, that no such payment shall be
required if such Note has been called for redemption on a redemption date within
the period between and including such record date and such interest payment
date, or if such Note is surrendered for conversion on the interest payment
date. A Holder may convert a portion of a Note equal to $1,000 or any integral
multiple thereof.
A Note in respect of which a Holder had delivered a Repurchase Notice
exercising the option of such Holder to require the Company to repurchase such
Note may be converted only if the Repurchase Notice is withdrawn as provided
above and in accordance with the terms of the Indenture.
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<PAGE>
9. SUBORDINATION.
The indebtedness evidenced by the Notes is, to the extent and in the
manner provided in the First Supplemental Indenture and 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 First Supplemental
Indenture. Any Holder by accepting this Note agrees to and shall be bound by
such subordination provisions and authorizes the Trustee to give them effect.
In addition to all other rights of Senior Indebtedness described in the
First Supplemental Indenture and 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 Notes are in registered form without coupons in denominations of
$1,000 and integral multiples thereof. A Holder may register the transfer of or
exchange Notes in accordance with the First Supplemental Indenture and 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 First
Supplemental Indenture and the Indenture.
The aggregate principal amount of the Note in global form represented
hereby may from time to time be reduced to reflect conversions or redemptions of
a part of this Note in global form or cancellations of a part of this Note in
global form, in each case, and in any such case, by means of notations on the
Global Note Transfer Schedule on the last page hereof. Notwithstanding any
provision of this Note to the contrary, conversions or redemptions of a part of
this Note in global form and cancellations of a part of this Note in global
form, may be effected without the surrendering of this Note in global form,
PROVIDED that appropriate notations on the Global Note Transfer Schedule are
made by the Trustee, or the Custodian at the direction of the Trustee, to
reflect the appropriate reduction or increase, as the case may be, in the
aggregate principal amount of this Note in a global form resulting therefrom or
as a consequence thereof.
11. PERSONS DEEMED OWNERS.
The registered Holder of a Note 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 unless an abandoned property law designates another person.
4
<PAGE>
13. AMENDMENT, SUPPLEMENT, WAIVER.
Subject to certain exceptions, the First Supplemental Indenture, the
Indenture or the Notes may be amended or supplemented with the consent of the
Holders of a majority in aggregate principal amount of the Notes 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
aggregate principal amount of the Notes then outstanding. Without the consent of
or notice to any Holder, the Company and the Trustee may amend or supplement the
First Supplemental Indenture, the Indenture or the Notes to, among other things,
cure any ambiguity, omission, 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 Notes, the First Supplemental Indenture 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 Notes; default in payment of principal or premium on the Notes when due;
failure by the Company for 60 days after notice to it to comply with any of its
other agreements contained in the First Supplemental Indenture, the Indenture or
the Notes; default by the Company or any Subsidiary with respect to its
obligation to pay principal of or interest on indebtedness for borrowed money
aggregating more than $20.0 million or the acceleration of such indebtedness if
not withdrawn within 15 days from the date of such acceleration; and certain
events of bankruptcy, insolvency or reorganization of the Company or any of its
subsidiaries, all as and to the extent provided in the First Supplemental
Indenture and the Indenture. If an Event of Default (other than as a result of
certain events of bankruptcy, insolvency or reorganization) occurs and is
continuing, the Trustee or the Holders of at least 25% in principal amount of
the Notes then outstanding may declare all unpaid principal of and accrued
interest to the date of acceleration on the Notes then outstanding to be due and
payable immediately, all as and to the extent provided in the First Supplemental
Indenture and the Indenture. If an Event of Default occurs as a result of
certain events of bankruptcy, insolvency or reorganization, all unpaid principal
of and accrued interest on the Notes 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 First
Supplemental Indenture and the Indenture. Holders may not enforce the First
Supplemental Indenture, the Indenture or the Notes except as provided in the
First Supplemental Indenture and the Indenture. The Trustee may require
indemnity satisfactory to it before it enforces the First Supplemental
Indenture, the Indenture or the Notes. Subject to certain limitations, Holders
of a majority in principal amount of the Notes 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.
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<PAGE>
16. TRUSTEE DEALINGS WITH THE COMPANY.
State Street Bank and Trust Company, the Trustee under the First
Supplemental Indenture and 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 Notes,
the First Supplemental Indenture and the Indenture or for any claim based on, in
respect or by reason of, such obligations or their creation. The Holder of this
Note by accepting this Note waives and releases all such liability. The waiver
and release are part of the consideration for the issue of this Note.
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 Notes to maturity as provided in the First Supplemental Indenture and the
Indenture, the Company will be discharged from the First Supplemental Indenture
and the Indenture except for certain Sections thereof.
19. AUTHENTICATION.
This Note shall not be valid until the Trustee or an authenticating
agent signs the certificate of authentication on the other side of this Note.
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 Note and not specifically defined
herein are defined in the First Supplemental Indenture or in the Indenture and
are used herein as so defined.
21. FIRST SUPPLEMENTAL INDENTURE AND INDENTURE TO CONTROL.
In the case of any conflict between the provisions of this Note and the
First Supplemental Indenture and the Indenture, the provisions of the First
Supplemental Indenture and the Indenture shall control.
The Company will furnish to any Holder, upon written request and
without charge, a copy of the First Supplemental Indenture and the Indenture.
Requests may be made to: Natural
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<PAGE>
MicroSystems Corporation, 100 Crossing Boulevard, Framingham, Massachusetts
01702, Attention: Chief Financial Officer.
[The remainder of this page is left blank intentionally]
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<PAGE>
TRANSFER NOTICE
This Transfer Notice relates to $__________ principal amount of the 5%
Convertible Subordinated Notes Due 2005 of Natural MicroSystems Corporation, a
Delaware corporation, held by ______________________________ (the "Transferor").
(I) or (we) assign and transfer this Note to
_______________________________________________________________________________
(Print or type assignee's name, address and zip code)
_______________________________________________________________________________
_______________________________________________________________________________
(Insert assignee's social security or tax I.D. no.)
and irrevocably appoint _______________________________ agent to transfer this
Note on the books of the Company. The agent may substitute another to act for
him.
Your Signature: _______________________________________________________________
(Sign exactly as your name appears on the other side
of this Convertible Note)
Date: _______________________________________________________________
Signature Guarantee:(1) ______________________________________________
--------
(1) Signature must be guaranteed by a commercial bank, trust company or
member firm of the New York Stock Exchange.
<PAGE>
CONVERSION NOTICE
To Natural MicroSystems Corporation:
The undersigned owner of this Note hereby irrevocably exercises the
option to convert this Note, or the portion below designated, into Common Stock
of Natural MicroSystems Corporation in accordance with the terms of the First
Supplemental Indenture and the Indenture referred to in this Note, and directs
that the shares issuable and deliverable upon conversion, together with any
check in payment for fractional shares, be issued in the name of and delivered
to the undersigned, unless a different name has been indicated in the assignment
below. If shares are to be issued in the name of a person other than the
undersigned, the undersigned will pay all transfer taxes payable with respect
thereto.
/ / Convert whole / / Convert in part
Amount of Note to be converted
($1,000 or integral multiples
thereof):
$____________________________
_______________________________________
Signature (sign exactly as name
appears on the other side of this Note)
_______________________________________
Signature Guarantee:(2)
--------
(2) Signature must be guaranteed by a commercial bank, trust company or
member firm of the New York Stock Exchange.
<PAGE>
If you want the stock certificate made out in another person's name, complete
the following for such person:
_________________________________________________
Name
_________________________________________________
Social Security or Taxpayer Identification Number
_________________________________________________
Street Address
_________________________________________________
City, State and Zip Code
<PAGE>
OPTION OF HOLDER TO ELECT REPURCHASE
If you want to elect to have this Note repurchased by the Company
pursuant to Section 3.08 of the First Supplemental Indenture, check the box:
/ /
If you want to elect to have only part of this Note repurchased by the
Company pursuant to Section 3.08 of the First Supplemental Indenture, state the
principal amount (which shall be $1,000 or a multiple thereof) to be
repurchased: $____________________
Dated: ___________________________ _______________________________________
Signature (sign exactly as name appears
on the other side of this Note)
__________________________________
Signature Guarantee:(3)
--------
(3) Signature must be guaranteed by a commercial bank, trust company or
member firm of the New York Stock Exchange.
<PAGE>
Schedule A to Exhibit A
GLOBAL NOTE TRANSFER SCHEDULE
Changes to Principal Amount of Global Note
<TABLE>
<CAPTION>
===================================================================================================================
Date Principal Amount of Notes by Remaining Principal Amount of this Authorized Signature
which this Global Note Is to Be Global Note of officer of Trustee
Reduced and Reason for Reduction (following decrease) or Note Custodian
-------------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C>
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===================================================================================================================
</TABLE>
Schedule to be maintained by Depositary in cooperation with Trustee.
