<PAGE>   1





                                                                     Exhibit 4.1

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



                                    INDENTURE

                            Dated as of May 23, 2001


                                     Between

                             BROOKS AUTOMATION, INC.

                                       and

                       STATE STREET BANK AND TRUST COMPANY

                                   as Trustee

                               ------------------

              4.75% Convertible Subordinated Notes Due June 1, 2008


================================================================================
<PAGE>   2
<TABLE>
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                                TABLE OF CONTENTS
                                                                                                      Page

                                    ARTICLE 1

                   DEFINITIONS AND INCORPORATION BY REFERENCE

<S>                                                                                                   <C>
SECTION 1.1.   Definitions...............................................................................1
SECTION 1.2.   Other Definitions.........................................................................6
SECTION 1.3.   Trust Indenture Act Provisions............................................................7
SECTION 1.4.   Rules of Construction.....................................................................7

                                    ARTICLE 2

                                 THE SECURITIES

SECTION 2.1.   Form and Dating...........................................................................8
SECTION 2.2.   Execution and Authentication..............................................................9
SECTION 2.3.   Registrar, Paying Agent and Conversion Agent..............................................9
SECTION 2.4.   Paying Agent to Hold Money in Trust......................................................10
SECTION 2.5.   Security Holder Lists....................................................................10
SECTION 2.6.   Transfer and Exchange....................................................................10
SECTION 2.7.   Replacement Securities...................................................................11
SECTION 2.8.   Outstanding Securities...................................................................12
SECTION 2.9.   Treasury Securities......................................................................12
SECTION 2.10.  Temporary Securities.....................................................................12
SECTION 2.11.  Cancellation.............................................................................13
SECTION 2.12.  Additional Transfer and Exchange Requirements............................................13
SECTION 2.13.  CUSIP Numbers............................................................................18
SECTION 2.14.  Defaulted Interest.......................................................................18

                                    ARTICLE 3

                            REDEMPTION AND PURCHASES

SECTION 3.1.   Provisional and Optional Redemption; Notice to Trustee...................................19
SECTION 3.2.   Selection of Securities to Be Redeemed...................................................20
SECTION 3.3.   Notice of Redemption.....................................................................20
SECTION 3.4.   Effect of Notice of Redemption...........................................................21
SECTION 3.5.   Deposit of Redemption Price..............................................................21
SECTION 3.6.   Securities Redeemed in Part..............................................................21
SECTION 3.7.   Conversion Arrangement on Call for Redemption............................................21
SECTION 3.8.   Purchase of Securities at Option of the Holder upon Change in Control....................22
SECTION 3.9.   Effect of Change in Control Purchase Notice..............................................25
SECTION 3.10.  Deposit of Change in Control Purchase Price..............................................25
SECTION 3.11.  Securities Purchased in Part.............................................................26
SECTION 3.12.  Compliance with Securities Laws upon Purchase of Securities..............................26
SECTION 3.13.  Repayment to the Company.................................................................26
</TABLE>


                                      -i-
<PAGE>   3
<TABLE>
<CAPTION>
                                                                                                      Page
                                    ARTICLE 4

                                   CONVERSION
<S>                                                                                                   <C>
SECTION 4.1.   Conversion Privilege.....................................................................26
SECTION 4.2.   Conversion Procedure.....................................................................27
SECTION 4.3.   Fractional Shares........................................................................28
SECTION 4.4.   Taxes on Conversion......................................................................28
SECTION 4.5.   Company to Provide Stock.................................................................28
SECTION 4.6.   Adjustment of Conversion Price...........................................................29
SECTION 4.7.   No Adjustment............................................................................32
SECTION 4.8.   Adjustment for Tax Purposes..............................................................33
SECTION 4.9.   Notice of Adjustment.....................................................................33
SECTION 4.10.  Notice of Certain Transactions...........................................................33
SECTION 4.11.  Effect of Reclassification, Consolidation, Merger or Sale on Conversion Privilege........33
SECTION 4.12.  Trustee's Disclaimer.....................................................................34
SECTION 4.13.  Voluntary Reduction......................................................................34

                                    ARTICLE 5

                                  SUBORDINATION

SECTION 5.1.   Agreement of Subordination...............................................................35
SECTION 5.2.   Payments to Holders......................................................................35
SECTION 5.3.   Subrogation of Securities................................................................37
SECTION 5.4.   Authorization to Effect Subordination....................................................38
SECTION 5.5.   Notice to Trustee........................................................................38
SECTION 5.6.   Trustee's Relation to Senior Indebtedness................................................39
SECTION 5.7.   No Impairment of Subordination...........................................................39
SECTION 5.8.   Certain Conversions Deemed Payment.......................................................40
SECTION 5.9.   Article Applicable to Paying Agents......................................................40
SECTION 5.10.  Senior Indebtedness Entitled to Rely.....................................................40

                               ARTICLE 6

                               COVENANTS

SECTION 6.1.   Payment of Securities...................................................................40
SECTION 6.2.   SEC Reports.............................................................................41
SECTION 6.3.   Compliance Certificates.................................................................41
SECTION 6.4.   Further Instruments and Acts............................................................41
SECTION 6.5.   Maintenance of Corporate Existence......................................................41
SECTION 6.6.   Rule 144A Information Requirement.......................................................42
SECTION 6.7.   Stay, Extension and Usury Laws..........................................................42
SECTION 6.8.   Payment of Additional Interest..........................................................42
</TABLE>


                                      -ii-
<PAGE>   4
<TABLE>
<CAPTION>
                                                                                                      Page
                                    ARTICLE 7

              CONSOLIDATION, MERGER, CONVEYANCE, TRANSFER OR LEASE

<S>                                                                                                   <C>
SECTION 7.1.   Company May Consolidate, Etc., Only on Certain Terms...................................42
SECTION 7.2.   Successor Substituted..................................................................43

                                    ARTICLE 8

                              DEFAULT AND REMEDIES

SECTION 8.1.   Events of Default......................................................................43
SECTION 8.2.   Acceleration...........................................................................45
SECTION 8.3.   Other Remedies.........................................................................45
SECTION 8.4.   Waiver of Defaults and Events of Default...............................................45
SECTION 8.5.   Control by Majority....................................................................46
SECTION 8.6.   Limitations on Suits...................................................................46
SECTION 8.7.   Rights of Holders to Receive Payment and to Convert....................................46
SECTION 8.8.   Collection Suit by Trustee.............................................................46
SECTION 8.9.   Trustee May File Proofs of Claim.......................................................47
SECTION 8.10.  Priorities.............................................................................47
SECTION 8.11.  Undertaking for Costs..................................................................48

                               ARTICLE 9

                                TRUSTEE

SECTION 9.1.   Duties of Trustee......................................................................48
SECTION 9.2.   Rights of Trustee......................................................................49
SECTION 9.3.   Individual Rights of Trustee...........................................................50
SECTION 9.4.   Trustee's Disclaimer...................................................................50
SECTION 9.5.   Notice of Default or Events of Default.................................................50
SECTION 9.6.   Reports by Trustee to Holders..........................................................50
SECTION 9.7.   Compensation and Indemnity.............................................................50
SECTION 9.8.   Replacement of Trustee.................................................................51
SECTION 9.9.   Successor Trustee by Merger, Etc.......................................................52
SECTION 9.10.  Eligibility; Disqualification..........................................................52
SECTION 9.11.  Preferential Collection of Claims Against Company......................................52
 .
                                   ARTICLE 10

                     SATISFACTION AND DISCHARGE OF INDENTURE

SECTION 10.1.  Satisfaction and Discharge of Indenture................................................53
SECTION 10.2.  Application of Trust Money.............................................................54
SECTION 10.3.  Repayment to Company...................................................................54
SECTION 10.4.  Reinstatement..........................................................................54
</TABLE>


                                     -iii-
<PAGE>   5
<TABLE>
<CAPTION>
                                                                                                      Page
                                   ARTICLE 11

                       AMENDMENTS, SUPPLEMENTS AND WAIVERS

<S>                                                                                                   <C>
SECTION 11.1.  Without Consent of Holders.............................................................54
SECTION 11.2.  With Consent of Holders................................................................55
SECTION 11.3.  Compliance with Trust Indenture Act....................................................56
SECTION 11.4.  Revocation and Effect of Consents......................................................56
SECTION 11.5.  Notation on or Exchange of Securities..................................................56
SECTION 11.6.  Trustee to Sign Amendments, Etc........................................................56

                                   ARTICLE 12

                                  MISCELLANEOUS

SECTION 12.1.  Trust Indenture Act Controls...........................................................57
SECTION 12.2.  Notices................................................................................57
SECTION 12.3.  Communications by Holders with Other Holders...........................................58
SECTION 12.4.  Certificate and Opinion as to Conditions Precedent.....................................58
SECTION 12.5.  Record Date for Vote or Consent of Securityholders.....................................58
SECTION 12.6.  Rules by Trustee, Paying Agent, Registrar and Conversion Agent.........................59
SECTION 12.7.  Legal Holidays.........................................................................59
SECTION 12.8.  Governing Law..........................................................................59
SECTION 12.9.  No Adverse Interpretation of Other Agreements..........................................59
SECTION 12.10. No Recourse Against Others.............................................................59
SECTION 12.11. Successors.............................................................................59
SECTION 12.12. Multiple Counterparts..................................................................59
SECTION 12.13. Separability...........................................................................60
SECTION 12.14. Table of Contents, Headings, Etc.......................................................60
SECTION 12.15. Improper Payments......................................................................60
</TABLE>


                                      -iv-
<PAGE>   6
                             CROSS-REFERENCE TABLE*

<TABLE>
<CAPTION>
                                                                     INDENTURE
TIA SECTION                                                            SECTION


<S>                 <C>                                              <C>
Section 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.
Section 311(a).......................................................9.11
                    (b)..............................................9.11
                    (c)..............................................N.A.
Section 312(a).......................................................2.5
                    (b)..............................................12.3
                    (c)..............................................12.3
Section 313(a).......................................................9.6
                    (b)(1)...........................................N.A.
                    (b)(2)...........................................9.6
                    (c)..............................................9.6; 12.2
                    (d)..............................................9.6
Section 314(a).......................................................6.2; 6.3,
                                                                     6.4; 12.2

                    (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.
Section 315(a).......................................................9.1(b)
                    (b)..............................................9.5; 12.2
                    (c)..............................................9.1(a)
                    (d)..............................................9.1(c)
                    (e)..............................................8.11
Section 316(a)(last sentence)........................................2.9
                    (a)(1)(A)........................................8.5
                    (a)(1)(B)........................................8.4
                    (a)(2)...........................................N.A.
                    (b)..............................................8.7
                    (c)..............................................2.5
Section 317(a)(1)....................................................8.8
                    (a)(2)...........................................8.9
                    (b)..............................................2.4
</TABLE>

---------------------
* This Cross-Reference Table shall not, for any purpose, be deemed a part of
  this Indenture.

** N.A. means Not Applicable.


                                      -v-
<PAGE>   7
                  THIS INDENTURE dated as of May 23, 2001 is between Brooks
Automation, Inc., a Delaware corporation (the "COMPANY"), and State Street Bank
and Trust Company, a Massachusetts trust company, as Trustee (the "TRUSTEE").

                  In consideration of the premises and the purchase of the
Securities by the Holders thereof, 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 4.75% Convertible Subordinated Notes Due June 1, 2008.

                                    ARTICLE 1

                   DEFINITIONS AND INCORPORATION BY REFERENCE


SECTION 1.1.               Definitions.

                  "ADDITIONAL INTEREST" has the meaning specified in Section
5(a) of the Registration Rights Agreement. All references herein to interest
accrued or payable as of any date shall include any Additional Interest accrued
or payable as of such date as provided in the Registration Rights Agreement.

                  "AFFILIATE" means, with respect to any specified person, 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.

                  "APPLICABLE PROCEDURES" means, with respect to any transfer or
exchange of beneficial ownership interests in a Global Security, the rules and
procedures of the Depositary that are applicable to such transfer or exchange.

                  "BOARD OF DIRECTORS" means the board of directors of the
Company or any authorized committee of the Board of Directors.

                  "BUSINESS DAY" means each day that is not a Legal Holiday.

                  "CAPITAL STOCK" of any Person means any and all shares,
interests, rights to purchase, warrants, options, participations or other
equivalents of or interests in (however designated) equity of such Person, but
excluding any debt securities convertible into such equity.

                  "CASH" means such coin or currency of the United States as at
any time of payment is legal tender for the payment of public and private debts.

                  "CERTIFICATED SECURITY" means a Security that is in
substantially the form attached hereto as Exhibit A and that does not include
the information or the schedule called for by footnotes 1, 3 and 4 thereof.

                   "CODE" means the Internal Revenue Code of 1986, as amended.
<PAGE>   8
                                      -2-


                  "COMMON STOCK" means the common stock of the Company, par
value $.01 per share, as it exists on the date of this Indenture and any shares
of any class or classes of capital stock of the Company resulting from any
reclassification or reclassifications thereof and which have no preference in
respect of dividends or of amounts payable in the event of any voluntary or
involuntary liquidation, dissolution or winding-up of the Company and which are
not subject to redemption by the Company; provided, however, that if at any time
there shall be more than one such resulting class, the shares of each such class
then so issuable on conversion of Securities shall be substantially in the
proportion which the total number of shares of such class resulting from all
such reclassifications bears to the total number of shares of all such classes
resulting from all such reclassifications.

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

                  "CORPORATE TRUST OFFICE" shall be the principal address of the
Trustee specified in Section 12.2 or such other address as to which the Trustee
may give notice to the Company.

                  "CREDIT FACILITY" means that certain Demand Promissory Note
Agreement, dated as of May 2, 2000 with ABN AMRO Bank, N.V. including any
related notes, guarantees, collateral documents, instruments and agreements
executed in connection therewith, and in each case as amended (including any
amendment and restatement thereof), modified, renewed, refunded, replaced,
refinanced or restructured (including, without limitation, any amendment
increasing the amount of available borrowing thereunder) from time to time and
whether with the same or any other agent, lender or group of lenders.

                  "DEFAULT" means, when used with respect to the Securities, any
event which is or, after notice or passage of time or both, would be an Event of
Default.

                  "DESIGNATED SENIOR INDEBTEDNESS" means (a) the Company's
obligations under the Credit Facility, and (b) any particular Senior
Indebtedness in which the instrument creating or evidencing the same or the
assumption or guarantee thereof (or related agreements or documents to which the
Company is a party) expressly provides that such Indebtedness shall be
"Designated Senior Indebtedness" for purposes of this Indenture (provided that
such instrument, agreement or other document may place limitations and
conditions on the right of such Senior Indebtedness to exercise the rights of
Designated Senior Indebtedness). If any payment made to any holder of any
Designated Senior Indebtedness or its Representative with respect to such
Designated Senior Indebtedness is rescinded or must otherwise be returned by
such holder or Representative upon the insolvency, bankruptcy or reorganization
of the Company or otherwise, the reinstated Indebtedness of the Company arising
as a result of such rescission or return shall constitute Designated Senior
Indebtedness effective as of the date of such rescission or return.

                  "EXCHANGE ACT" means the Securities Exchange Act of 1934, as
amended, and the rules and regulations promulgated thereunder, as in effect from
time to time.

                  "FINAL MATURITY DATE" means June 1, 2008.

                  "GAAP" means generally accepted accounting principles in the
United States of America as in effect as of the date of this Indenture,
including those set forth in (1) the opinions and pronouncements of the
Accounting Principles Board of the American Institute of Certified Public
Accountants, (2) the statements and pronouncements of the Financial Accounting
Standards Board, (3) such other statements by such other entity as approved by a
significant segment of the accounting profession and (4) the rules and
regulations of the SEC
<PAGE>   9
                                      -3-


governing the inclusion of financial statements (including pro forma financial
statements) in registration statements filed under the Securities Act and
periodic reports required to be filed pursuant to Section 13 of the Exchange
Act, including opinions and pronouncements in staff accounting bulletins and
similar written statements from the accounting staff of the SEC.

                  "GLOBAL SECURITY" means a permanent Global Security that is in
substantially the form attached hereto as Exhibit A and that includes the
information and schedule called for by footnotes 1, 3 and 4 thereof and which is
deposited with the Depositary or its custodian and registered in the name of the
Depositary or its nominee.

                  "HOLDER" or "SECURITYHOLDER" means the person in whose name a
Security is registered on the Primary Registrar's books.

                  "INDEBTEDNESS" means, with respect to any Person, without
duplication, (a) all indebtedness, obligations and other liabilities (contingent
or otherwise) of such Person for borrowed money (including obligations of such
Person in respect of overdrafts, foreign exchange contracts, currency exchange
agreements, interest rate protection agreements, and any loans or advances from
banks, whether or not evidenced by notes or similar instruments) or evidenced by
credit or loan agreements, bonds, debentures, notes or written obligations
(whether or not the recourse of the lender is to the whole of the assets of such
Person or to only a portion thereof) (other than any accounts payable or other
accrued current liability or obligation incurred in the ordinary course of
business in connection with the obtaining of materials or services), (b) all
reimbursement obligations and other liabilities (contingent or otherwise) of
such Person with respect to letters of credit, bank guarantees or bankers'
acceptances, (c) all obligations and liabilities (contingent or otherwise) of
such Person (i) in respect of leases of such Person required, in conformity with
GAAP, to be accounted for as capitalized lease obligations on the balance sheet
of such Person, or (ii) under any lease or related document (including a
purchase agreement) in connection with the lease of real property or
improvements (or any personal property included as part of any such lease) which
provides that such Person is contractually obligated to purchase or cause a
third party to purchase the leased property and thereby guarantee a residual
value of the leased property to the lessor and all of the obligations of such
Person under such lease or related document to purchase or to cause a third
party to purchase such leased property (whether or not such lease transaction is
characterized as an operating lease or a capitalized lease in accordance with
GAAP), (d) all obligations (contingent or otherwise) of such Person with respect
to any interest rate, currency or other swap, cap, floor or collar agreement,
hedge agreement, forward contract, or other similar instrument or agreement or
foreign currency hedge, exchange, purchase or similar instrument or agreement,
(e) all of the Company's obligations evidenced by a note or similar instrument
given in connection with the acquisition of any business, properties or assets
of any kind, (f) all direct or indirect guaranties or similar agreements by such
Person to purchase or otherwise acquire or otherwise assure a creditor against
loss in respect of indebtedness, obligations or liabilities of another Person of
the kind described in clauses (a) through (e), and (g) any and all deferrals,
renewals, extensions and refundings of, or amendments, modifications or
supplements to, any indebtedness, obligation or liability of the kind described
in clauses (a) through (f).

                  "INDENTURE" means this Indenture as amended or supplemented
from time to time pursuant to the terms of this Indenture.

                  "OFFICER" means the Chairman or any Co-Chairman of the Board,
any Vice Chairman of the Board, the Chief Executive Officer, the President, any
Vice President, the Chief Financial Officer, the Controller, the Treasurer, the
Secretary or any Assistant Secretary of the Company.
<PAGE>   10
                                      -4-


                  "OFFICERS' CERTIFICATE" means a certificate signed by two
Officers; provided, however, that for purposes of Sections 4.11 and 6.3,
"Officers' Certificate" means a certificate signed by the principal executive
officer, principal financial officer or principal accounting officer of the
Company and by one other Officer.

                  "OPINION OF COUNSEL" means a written opinion from legal
counsel. The counsel may be an employee of or counsel to the Company or the
Trustee.

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

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

                  "REDEMPTION DATE," when used with respect to any Security to
be redeemed, means the Provisional Redemption Date, in the event of a
Provisional Redemption pursuant to Section 3.1(a) or the Optional Redemption
Date, in the event of an Optional Redemption pursuant to Section 3.1(b), as the
case may be.

                  "REDEMPTION PRICE," when used with respect to any Security to
be redeemed, means the Provisional Redemption Price, in the event of a
Provisional Redemption pursuant to Section 3.1(a) or the Optional Redemption
Price, in the event of an Optional Redemption pursuant to Section 3.1(b), as the
case may be.

                  "REGISTRATION RIGHTS AGREEMENT" means the Registration Rights
Agreement, dated as of May 23, 2001, among the Company and Credit Suisse First
Boston Corporation and SG Cowen Securities Corporation, as initial purchasers.

                  "REPRESENTATIVE" means (a) the indenture trustee or other
trustee, agent or representative for any Senior Indebtedness or (b) with respect
to any Senior Indebtedness that does not have any such trustee, agent or other
representative, (i) in the case of such Senior Indebtedness issued pursuant to
an agreement providing for voting arrangements as among the holders or owners of
such Senior Indebtedness, any holder or owner of such Senior Indebtedness acting
with the consent of the required persons necessary to bind such holders or
owners of such Senior Indebtedness and (ii) in the case of all other such Senior
Indebtedness, the holder or owner of such Senior Indebtedness.

                  "RESTRICTED CERTIFICATED SECURITY" means a Certificated
Security which is a Transfer Restricted Security.

                  "RESTRICTED GLOBAL SECURITY" means a Global Security that is a
Transfer Restricted Security.

                   "RULE 144" means Rule 144 under the Securities Act or any
successor to such Rule.

                  "RULE 144A" means Rule 144A under the Securities Act or any
successor to such Rule.

                  "SEC" means the Securities and Exchange Commission.

                  "SECURITIES" means the 4.75% Convertible Subordinated Notes
Due June 1, 2008 or any of them (each, a "SECURITY"), as amended or supplemented
from time to time, that are issued under this Indenture.
<PAGE>   11
                                      -5-



                  "SECURITIES ACT" means the Securities Act of 1933, as amended,
and the rules and regulations promulgated thereunder, as in effect from time to
time.

                  "SECURITIES CUSTODIAN" means the Trustee, as custodian with
respect to the Securities in global form, or any successor thereto.

                  "SENIOR INDEBTEDNESS" means the principal of, premium, if any,
interest (including all interest accruing subsequent to the commencement of any
bankruptcy or similar proceeding, whether or not a claim for post-petition
interest is allowable as a claim in any such proceeding) and rent payable on or
in connection with, and all fees, costs, expenses and other amounts accrued or
due on or in connection with, Indebtedness of the Company, whether secured or
unsecured, absolute or contingent, due or to become due, outstanding on the date
of this Indenture or thereafter created, incurred, assumed, guaranteed or in
effect guaranteed by the Company (including all deferrals, renewals, extensions
or refundings of, or amendments, modifications or supplements to, the
foregoing), unless in the case of any particular Indebtedness the instrument
creating or evidencing the same or the assumption or guarantee thereof expressly
provides that such Indebtedness shall not be senior in right of payment to the
Securities or expressly provides that such Indebtedness is "pari passu" or
"junior" to the Securities. Notwithstanding the foregoing, the term Senior
Indebtedness shall not include any Indebtedness of the Company to any Subsidiary
of the Company or any obligation for Federal, state, local or other taxes. If
any payment made to any holder of any Senior Indebtedness or its Representative
with respect to such Senior Indebtedness is rescinded or must otherwise be
returned by such holder or Representative upon the insolvency, bankruptcy or
reorganization of the Company or otherwise, the reinstated Indebtedness of the
Company arising as a result of such rescission or return shall constitute Senior
Indebtedness effective as of the date of such rescission or return.

                  "SUBSIDIARY" means, in respect of any Person, any corporation,
association, partnership or other business entity of which more than 50% of the
total voting power of shares of Capital Stock or other interests (including
partnership interests) entitled (without regard to the occurrence of any
contingency) to vote in the election of directors, managers, general partners or
trustees thereof is at the time owned or controlled, directly or indirectly, by
(i) such Person; (ii) such Person and one or more Subsidiaries of such Person;
or (iii) one or more Subsidiaries of such Person.

                  "TIA" means the Trust Indenture Act of 1939, as amended, as in
effect on the date of this Indenture, except as provided in Section 11.3, 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, with respect to any security, each
Monday, Tuesday, Wednesday, Thursday and Friday, other than any day on which
securities are not generally traded on the principal exchange or market in which
such security is traded.

                  "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, with respect to the Trustee, any
officer in its corporate trust department (or similar group) having direct
responsibility for the administration of the trust hereunder, and also, with
respect to a particular matter, any other officer to whom such matter is
referred because of such officer's knowledge of and familiarity with the
particular subject.
<PAGE>   12
                                      -6-



                  "UNRESTRICTED CERTIFICATED SECURITY" means a Certificated
Security that is not a Transfer Restricted Security.

                  "UNRESTRICTED GLOBAL SECURITY" means a Global Security that is
not a Transfer Restricted Security.

                  "VOTING STOCK" of a Person means any class or classes of
Capital Stock of such Person pursuant to which the holders of Capital Stock
under ordinary circumstances have the power to vote in the election of the board
of directors, managers or trustees of any person or other persons performing
similar functions irrespective of whether or not, at the time Capital Stock of
any other class or classes shall have, or might have, voting power by reason of
the occurrence of any contingency.

SECTION 1.2.               Other Definitions.

<TABLE>
<CAPTION>
                                                                  Defined
Term                                                              in Section

<S>                                                               <C>
"Agent Members".................................................. 2.1
"Bankruptcy Law"................................................. 8.1
"Change in Control".............................................. 3.8(a)
"Change in Control Purchase Date"................................ 3.8(a)
"Change in Control Purchase Notice".............................. 3.8(c)
"Change in Control Purchase Price"............................... 3.8(a)
"Closing Price".................................................. 4.6(f)
"Company Order".................................................. 2.2
"Conversion Agent"............................................... 2.3
"Conversion Date"................................................ 4.2
"Conversion Price"............................................... 4.6
"Current Market Price Per Share"................................. 4.6(f)
"Custodian"...................................................... 8.1
"DTC"............................................................ 2.1(a)
"Defaulted Interest" ............................................ 2.14
"Depositary"..................................................... 2.1(a)
"Determination Date"............................................. 4.6(d)
"Event of Default"............................................... 8.1
"Expiration Date"................................................ 4.6(e)
"Expiration Time"................................................ 4.6(e)
"Legal Holiday".................................................. 12.7
"Make-Whole Payment"............................................. 3.1(a)
"NNM"............................................................ 4.6(f)
"Notice Date".................................................... 3.1(a)
"NYSE"........................................................... 4.6(f)
"Optional Redemption"............................................ 3.1(b)
"Optional Redemption Date"....................................... 3.1(b)
"Optional Redemption Price"...................................... 3.1(b)
"Paying Agent"................................................... 2.3
"Payment Blockage Notice"........................................ 5.2
"Primary Registrar".............................................. 2.3
</TABLE>
<PAGE>   13
                                      -7-


<TABLE>
<CAPTION>

<S>                                                               <C>
"Provisional Redemption"......................................... 3.1(a)
"Provisional Redemption Date".................................... 3.1(a)
"Provisional Redemption Price"................................... 3.1(a)
"Purchase Agreement"............................................. 2.1
"Purchased Shares"............................................... 4.6(e)
"QIB"............................................................ 2.1(a)
"Registrar"...................................................... 2.3
"Transfer Certificate"........................................... 2.12(f)
"Transfer Restricted Security"................................... 2.12(f)
"Triggering Distribution"........................................ 4.6(d)
</TABLE>

SECTION 1.3.               Trust Indenture Act Provisions.

                  Whenever this Indenture refers to a provision of the TIA, that
provision is incorporated by reference in and made a part of this Indenture. The
Indenture shall also include those provisions of the TIA required to be included
herein by the provisions of the Trust Indenture Reform Act of 1990. The
following TIA terms used in this Indenture have the following meanings:

                  "INDENTURE SECURITIES" means the Securities;

                  "INDENTURE SECURITY HOLDER" means a Securityholder;

                  "INDENTURE TO BE QUALIFIED" means this Indenture;

                  "INDENTURE TRUSTEE" or "INSTITUTIONAL TRUSTEE" means the
Trustee; and "obligor" on the indenture securities means the Company or any
other obligor on the Securities.

                  All other terms used in this Indenture that are defined in the
TIA, defined by TIA reference to another statute or defined by any 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:

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

                  (ii) an accounting term not otherwise defined has the meaning
         assigned to it in accordance with GAAP;

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

                  (iv) provisions apply to successive events and transactions;

                  (v) the term "merger" includes a statutory share exchange and
         the term "merged" has a correlating meaning;

                  (vi) the masculine gender includes the feminine and the
         neuter;
<PAGE>   14
                                      -8-


                  (vii) references to agreements and other instruments include
         subsequent amendments thereto; and

                  (viii) "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.


                                    ARTICLE 2

                                 THE SECURITIES


SECTION 2.1.               Form and Dating.

                  The Securities and the Trustee's certificate of authentication
shall be substantially in the respective forms set forth in Exhibit A, which
Exhibit is incorporated in and made part of this Indenture. The Securities may
have notations, legends or endorsements required by law, stock exchange rule or
usage. Each Security shall be dated the date of its authentication. The
Securities are being offered and sold by the Company pursuant to a Purchase
Agreement, dated May 17, 2001 (the "PURCHASE Agreement"), between the Company
and Credit Suisse First Boston Corporation and SG Cowen Securities Corporation
in transactions exempt from, or not subject to, the registration requirements of
the Securities Act.

                  (a) Restricted Global Securities. All of the Securities are
initially being offered and sold to qualified institutional buyers as defined in
Rule 144A (collectively, "QIBS" or individually, each a "QIB") in reliance on
Rule 144A under the Securities Act and shall be issued initially in the form of
one or more Restricted Global Securities, which shall be deposited on behalf of
the purchasers of the Securities represented thereby with the Trustee, at its
Corporate Trust Office, as custodian for the depositary, The Depository Trust
Company ("DTC") (such depositary, or any successor thereto, being hereinafter
referred to as the "DEPOSITARY"), and registered in the name of its nominee,
Cede & Co., duly executed by the Company and authenticated by the Trustee as
hereinafter provided. The aggregate principal amount of the Restricted Global
Security may from time to time be increased or decreased by adjustments made on
the records of the Securities Custodian as hereinafter provided, subject in each
case to compliance with the Applicable Procedures.

                  (b) Global Securities In General. Each Global Security shall
represent such of the outstanding Securities as shall be specified therein and
each shall provide that it shall represent the aggregate amount of outstanding
Securities from time to time endorsed thereon and that the aggregate amount of
outstanding Securities represented thereby may from time to time be reduced or
increased, as appropriate, to reflect exchanges, redemptions, purchases or
conversions of such Securities. Any endorsement of a Global Security to reflect
the amount of any increase or decrease in the amount of outstanding Securities
represented thereby shall be made by the Securities Custodian in accordance with
the standing instructions and procedures existing between the Depositary and the
Securities Custodian.

                  Members of, or participants in, the Depositary ("AGENT
MEMBERS") shall have no rights under this Indenture with respect to any Global
Security held on their behalf by the Depositary or under any Global Security,
and the Depositary (including, for this purpose, its nominee) may be treated by
the Company, the Trustee and any agent of the Company or the Trustee as the
absolute owner and Holder of such Global Security for all purposes whatsoever.
Notwithstanding the foregoing, nothing herein shall (A) prevent the Company, the
Trustee or any agent of the Company or the Trustee from giving effect to any
written certification, proxy or
<PAGE>   15
                                      -9-


other authorization furnished by the Depositary or (B) impair, as between the
Depositary and its Agent Members, the operation of customary practices governing
the exercise of the rights of a Holder of any Security.

                  (c) Certificated Securities. Certificated Securities shall be
issued only under the limited circumstances provided in Section 2.12(a)(1)
hereof.

SECTION 2.2.               Execution and Authentication.

                  An Officer shall sign the Securities for the Company by manual
or facsimile signature attested by the manual or facsimile signature of the
Secretary or an Assistant Secretary of the Company. Typographic and other minor
errors or defects in any such facsimile signature shall not affect the validity
or enforceability of any Security which has been authenticated and delivered by
the Trustee.

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

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

                  The Trustee shall authenticate and make available for delivery
Securities for original issue in the aggregate principal amount of up to $150
million (plus up to an additional $25 million in aggregate principal amount
issuable upon the exercise of the option described in the Purchase Agreement)
upon receipt of a written order or orders of the Company signed by two Officers
of the Company (a "COMPANY ORDER"). The Company Order shall specify the amount
of Securities to be authenticated, shall provide that all such Securities will
be represented by a Restricted Global Security and the date on which each
original issue of Securities is to be authenticated. The aggregate principal
amount of Securities outstanding at any time may not exceed $150,000,000 plus
the amount (up to an additional $25 million) issuable upon exercise of the
option in the Purchase Agreement, 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 Securities. An authenticating agent may authenticate
Securities whenever the Trustee may do so. Each reference in this Indenture to
authentication by the Trustee includes authentication by such agent. An
authenticating agent shall have the same rights as an Agent to deal with the
Company or an Affiliate of the Company.

                  The Securities shall be 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 and Conversion Agent.

                  The Company shall maintain one or more offices or agencies
where Securities may be presented for registration of transfer or for exchange
(each, a "REGISTRAR"), one or more offices or agencies where Securities may be
presented for payment (each, a "PAYING AGENT"), one or more offices or agencies
where Securities may be presented for conversion (each, a "CONVERSION AGENT")
and one or more offices or agencies where notices and demands to or upon the
Company in respect of the Securities and this Indenture may be served. The
Company will at all times maintain a Paying Agent, Conversion Agent, Registrar
and an office or agency where notices and demands to or upon the Company in
respect of the Securities and this Indenture may be served in the
<PAGE>   16
                                      -10-


Borough of Manhattan, the City of New York. One of the Registrars (the "PRIMARY
REGISTRAR") shall keep a register of the Securities and of their transfer and
exchange.

                  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 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 in any place required by this
Indenture, or fails to give the foregoing notice, the Trustee shall act as such.
The Company or any Affiliate of the Company may act as Paying Agent (except for
the purposes of Section 6.1 and Article 10).

                  The Company hereby initially designates the Trustee as Paying
Agent, Registrar, Primary Registrar, Custodian and Conversion Agent.

SECTION 2.4.               Paying Agent to Hold Money in Trust.

                  Prior to 11:00 a.m., New York City time, on each due date of
the principal of or interest, if any, on any Securities, the Company shall
deposit with a Paying Agent a sum sufficient to pay such principal or interest,
if any, so becoming due. Subject to Section 5.7, a Paying Agent shall hold in
trust for the benefit of Security holders or the Trustee all money held by the
Paying Agent for the payment of principal of or interest, if any, on the
Securities, and if the Paying Agent is different than the Trustee, shall notify
the Trustee of any Default by the Company (or any other obligor on the
Securities) in making any such payment. If the Company or an Affiliate of the
Company acts as Paying Agent, it shall, before 11:00 a.m., New York City time,
on each due date of the principal of or interest on any Securities, 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.               Security Holder 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 Security holders. If the Trustee is not the Primary Registrar, the
Company shall furnish to the Trustee on or before each semiannual 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 Securityholders.

SECTION 2.6.               Transfer and Exchange.

                  (a) Subject to compliance with any applicable additional
requirements contained in Section 2.12, when a Security is presented to a
Registrar with a request to register a transfer thereof or to exchange such
Security for an equal principal amount of Securities of other authorized
denominations, the Registrar shall register the transfer or make the exchange as
requested; provided, however, that every Security presented or surrendered for
registration of transfer or exchange shall be duly endorsed or accompanied by an
assignment form and, if applicable, a transfer certificate each in the form
included in Exhibit A, and in form satisfactory to the Registrar duly executed
by the Holder thereof or its attorney duly authorized in writing. To permit
registration of transfers and exchanges, upon surrender of any Security for
registration of transfer or exchange at an office or agency maintained pursuant
to Section 2.3, the Company shall execute and the Trustee shall authenti-
<PAGE>   17
                                      -11-


cate Securities of a like aggregate principal amount at the Registrar's request.
Any exchange or transfer shall be without charge, except that the Company or the
Registrar may require payment of a sum sufficient to cover any tax or other
governmental charge that may be imposed in relation thereto, and provided, that
this sentence shall not apply to any exchange pursuant to Section 2.7, 2.10,
2.12(a)(1), 3.6, 3.11, 4.2 (last paragraph) or 11.5.

                  Neither the Company, any Registrar nor the Trustee shall be
required to exchange or register a transfer of (a) any Securities for a period
of 15 days next preceding any mailing of a notice of Securities to be redeemed,
(b) any Securities or portions thereof selected or called for redemption
(except, in the case of redemption of a Security in part, the portion not to be
redeemed) or (c) any Securities or portions thereof in respect of which a Change
in Control Purchase Notice has been delivered and not withdrawn by the Holder
thereof (except, in the case of the purchase of a Security in part, the portion
not to be purchased).

                  All Securities issued upon any transfer or exchange of
Securities shall be valid obligations of the Company, evidencing the same debt
and entitled to the same benefits under this Indenture, as the Securities
surrendered upon such transfer or exchange.

                  (b) Any Registrar appointed pursuant to Section 2.3 hereof
shall provide to the Trustee such information as the Trustee may reasonably
require in connection with the delivery by such Registrar of Securities upon
transfer or exchange of Securities.

                  (c) Each Holder of a Security agrees to indemnify the Company
and the Trustee against any liability that may result from the transfer,
exchange or assignment of such Holder's Security in violation of any provision
of this Indenture and/or applicable United States federal or state securities
law.

                  The Trustee shall have no obligation or duty to monitor,
determine or inquire as to compliance with any restrictions on transfer imposed
under this Indenture or under applicable law with respect to any transfer of any
interest in any Security (including any transfers between or among Agent Members
or other beneficial owners of interests in any Global Security) other than to
require delivery of such certificates and other documentation or evidence as are
expressly required by, and to do so if and when expressly required by the terms
of, this Indenture, and to examine the same to determine substantial compliance
as to form with the express requirements hereof. The Trustee shall have no
responsibility for the actions or omissions of the Depositary, or for the
accuracy of the books or records of the Depositary.

SECTION 2.7.               Replacement Securities.

                  If any mutilated Security is surrendered to the Company, a
Registrar or the Trustee, or the Company, a Registrar and the Trustee receive
evidence to their satisfaction of the destruction, loss or theft of any
Security, and there is delivered to the Company, the applicable Registrar and
the Trustee such Security or indemnity as will be required by them to save each
of them harmless, then, in the absence of notice to the Company, such Registrar
or the Trustee that such Security has been acquired by a bona fide purchaser,
the Company shall execute, and upon its written request the Trustee shall
authenticate and deliver, in exchange for any such mutilated Security or in lieu
of any such destroyed, lost or stolen Security, a new Security of like tenor and
principal amount, bearing a number not contemporaneously outstanding.

                  In case any such mutilated, destroyed, lost or stolen Security
has become or is about to become due and payable, or is about to be redeemed or
purchased by the Company pursuant to Article 3, the Company in its discretion
may, instead of issuing a new Security, pay, redeem or purchase such Security,
as the case may be.
<PAGE>   18
                                      -12-



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

                  Every new Security issued pursuant to this Section 2.7 in lieu
of any destroyed, lost or stolen Security shall constitute an original
additional contractual obligation of the Company, whether or not the destroyed,
lost or stolen Security shall be at any time enforceable by anyone, and shall be
entitled to all benefits of this Indenture equally and proportionately with any
and all other Securities duly issued hereunder.

                  The provisions of this Section 2.7 are (to the extent lawful)
exclusive and shall preclude (to the extent lawful) all other rights and
remedies with respect to the replacement or payment of mutilated, destroyed,
lost or stolen Securities.

SECTION 2.8.               Outstanding Securities.

                  Securities outstanding at any time are all Securities
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 Security is replaced pursuant to Section 2.7, it ceases
to be outstanding unless the Company receives proof satisfactory to it that the
replaced Security is held by a bona fide purchaser.

                  If a Paying Agent (other than the Company or an Affiliate of
the Company) holds on a Redemption Date, a Change in Control Purchase Date or
the Final Maturity Date money sufficient to pay the principal of (including
premium, if any) and accrued interest on Securities (or portions thereof)
payable on that date, then on and after that date such Securities (or portions
thereof, as the case may be) cease to be outstanding and interest on them ceases
to accrue.

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

SECTION 2.9.               Treasury Securities.

                  In determining whether the Holders of the required principal
amount of Securities have concurred in any notice, direction, waiver or consent,
Securities owned by the Company or any other obligor on the Securities 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 Securities which
a Trust Officer of the Trustee actually knows are so owned shall be so
disregarded. Securities 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 Securities and that the pledgee is
not the Company or any other obligor on the Securities or any Affiliate of the
Company or of such other obligor.

SECTION 2.10.              Temporary Securities.

                  Until definitive Securities are ready for delivery, the
Company may prepare and execute, and, upon receipt of a Company Order, the
Trustee shall authenticate and deliver, temporary Securities. Temporary
<PAGE>   19
                                      -13-



Securities shall be substantially in the form of definitive Securities but may
have variations that the Company with the consent of the Trustee considers
appropriate for temporary Securities. Without unreasonable delay, the Company
shall prepare and the Trustee shall authenticate and deliver definitive
Securities in exchange for temporary Securities.

SECTION 2.11.              Cancellation.

                  The Company at any time may deliver Securities to the Trustee
for cancellation. The Registrar, the Paying Agent and the Conversion Agent shall
forward to the Trustee or its agent any Securities surrendered to them for
transfer, exchange, payment or conversion. The Trustee and no one else shall
cancel, in accordance with its standard procedures, all Securities surrendered
for transfer, exchange, redemption, payment, conversion or cancellation and
shall deliver the canceled Securities to the Company. All Securities which are
redeemed, purchased or otherwise acquired by the Company or any of its
Subsidiaries prior to the Final Maturity Date shall be delivered to the Trustee
for cancellation and the Company may not hold or resell such Securities or issue
any new Securities to replace any such Securities or any Securities that any
Holder has converted pursuant to Article 4. Without limitation to the foregoing,
any Securities acquired by any investment bankers or other purchasers pursuant
to Section 3.7 shall be surrendered for conversion and thereafter cancelled, and
may not be reoffered, sold or otherwise transferred.

SECTION 2.12.              Additional Transfer and Exchange Requirements.

                  (a) Transfer and Exchange of Global Securities.

                  (1) Certificated Securities shall be issued in exchange for
         interests in the Global Securities only if (x) the Depositary notifies
         the Company that it is unwilling or unable to continue as depositary
         for the Global Securities or if it at any time ceases to be a "clearing
         agency" registered under the Exchange Act, if so required by applicable
         law or regulation and a successor depositary is not appointed by the
         Company within 90 days, or (y) an Event of Default has occurred and is
         continuing. In either case, the Company shall execute, and the Trustee
         shall, upon receipt of a Company Order (which the Company agrees to
         delivery promptly), authenticate and deliver Certificated Securities in
         an aggregate principal amount equal to the principal amount of such
         Global Securities in exchange therefor. Only Restricted Certificated
         Securities shall be issued in exchange for beneficial interests in
         Restricted Global Securities, and only Unrestricted Certificated
         Securities shall be issued in exchange for beneficial interests in
         Unrestricted Global Securities. Certificated Securities issued in
         exchange for beneficial interests in Global Securities shall be
         registered in such names and shall be in such authorized denominations
         as the Depositary, pursuant to instructions from its direct or indirect
         participants or otherwise, shall instruct the Trustee. The Trustee
         shall deliver or cause to be delivered such Certificated Securities to
         the persons in whose names such Securities are so registered. Such
         exchange shall be effected in accordance with the Applicable
         Procedures.

                  (2) Notwithstanding any other provisions of this Indenture
         other than the provisions set forth in Section 2.12(a)(1), a Global
         Security may not be transferred as a whole except by the Depositary to
         a nominee of the Depositary or by a nominee of the Depositary to the
         Depositary or another nominee of the Depositary or by the Depositary or
         any such nominee to a successor Depositary or a nominee of such
         successor Depositary.

                  (b) Transfer and Exchange of Certificated Securities. In the
event that Certificated Securities are issued in exchange for beneficial
interests in Global Securities in accordance with Section 2.12(a)(1) of
<PAGE>   20
                                      -14-


this Indenture, on or after such event when Certificated Securities are
presented by a Holder to a Registrar with a request:

                  (x) to register the transfer of the Certificated Securities to
         a person who will take delivery thereof in the form of Certificated
         Securities only; or

                  (y) to exchange such Certificated Securities for an equal
         principal amount of Certificated Securities of other authorized
         denominations, such Registrar shall register the transfer or make the
         exchange as requested;

provided, however, that the Certificated Securities presented or surrendered for
register of transfer or exchange:

                  (1) shall be duly endorsed or accompanied by a written
         instrument of transfer in accordance with the proviso to the first
         paragraph of Section 2.6(a); and

                  (2) in the case of a Restricted Certificated Security, such
         request shall be accompanied by the following additional information
         and documents, as applicable:

                           (i) if such Restricted Certificated Security is being
                           delivered to the Registrar by a Holder for
                           registration in the name of such Holder, without
                           transfer, or such Restricted Certificated Security is
                           being transferred to the Company or a Subsidiary of
                           the Company, a certification to that effect from such
                           Holder (in substantially the form set forth in the
                           Transfer Certificate);

                           (ii) if such Restricted Certificated Security is
                           being transferred to a person the Holder reasonably
                           believes is a QIB in accordance with Rule 144A or
                           pursuant to an effective registration statement under
                           the Securities Act, a certification to that effect
                           from such Holder (in substantially the form set forth
                           in the Transfer Certificate); or

                           (iii) if such Restricted Certificated Security is
                           being transferred (i) pursuant to an exemption from
                           the registration requirements of the Securities Act
                           in accordance with Rule 144 or (ii) pursuant to an
                           exemption from the registration requirements of the
                           Securities Act (other than pursuant to Rule 144A or
                           Rule 144) and as a result of which, in the case of a
                           Security transferred pursuant to this clause (ii),
                           such Security shall cease to be a "restricted
                           security" within the meaning of Rule 144, a
                           certification to that effect from the Holder (in
                           substantially the form set forth in the Transfer
                           Certificate) and, if the Company or such Registrar so
                           requests, a customary opinion of counsel,
                           certificates and other information reasonably
                           acceptable to the Company and such Registrar to the
                           effect that such transfer is in compliance with the
                           registration requirements of the Securities Act.

                  (c) Transfer of a Beneficial Interest in a Restricted Global
Security for a Beneficial Interest in an Unrestricted Global Security. Any
person having a beneficial interest in a Restricted Global Security may upon
request, subject to the Applicable Procedures, transfer such beneficial interest
to a person who is required or permitted to take delivery thereof in the form of
an Unrestricted Global Security. Upon receipt by the Trustee of written
instructions, or such other form of instructions as is customary for the
Depositary, from the Depositary or its nominee on behalf of any person having a
beneficial interest in a Restricted Global Security and the following additional
information and documents in such form as is customary for the Depositary from

<PAGE>   21
                                      -15-


the Depositary or its nominee on behalf of the person having such beneficial
interest in the Restricted Global Security (all of which may be submitted by
facsimile or electronically):

                  (1) if such beneficial interest is being transferred pursuant
         to an effective registration statement under the Securities Act, a
         certification to that effect from the transferor (in substantially the
         form set forth in the Transfer Certificate); or

                  (2) if such beneficial interest is being transferred (i)
         pursuant to an exemption from the registration requirements of the
         Securities Act in accordance with Rule 144 or (ii) pursuant to an
         exemption from the registration requirements of the Securities Act
         (other than pursuant to Rule 144A or Rule 144) and as a result of
         which, in the case of a Security transferred pursuant to this clause
         (ii), such Security shall cease to be a "restricted security" within
         the meaning of Rule 144, a certification to that effect from the
         transferor (in substantially the form set forth in the Transfer
         Certificate) and, if the Company or the Trustee so requests, a
         customary opinion of counsel, certificates and other information
         reasonably acceptable to the Company and the Trustee to the effect that
         such transfer is in compliance with the registration requirements of
         the Securities Act, the Trustee, as a Registrar and Securities
         Custodian, shall reduce or cause to be reduced the aggregate principal
         amount of the Restricted Global Security by the appropriate principal
         amount and shall increase or cause to be increased the aggregate
         principal amount of the Unrestricted Global Security by a like
         principal amount. Such transfer shall otherwise be effected in
         accordance with the Applicable Procedures. If no Unrestricted Global
         Security is then outstanding, the Company shall execute and the Trustee
         shall, upon receipt of a Company Order (which the Company agrees to
         deliver promptly), authenticate and deliver an Unrestricted Global
         Security.

                  (d) Transfer of a Beneficial Interest in an Unrestricted
Global Security for a Beneficial Interest in a Restricted Global Security. Any
person having a beneficial interest in an Unrestricted Global Security may upon
request, subject to the Applicable Procedures, transfer such beneficial interest
to a person who is required or permitted to take delivery thereof in the form of
a Restricted Global Security (it being understood that only QIBs may own
beneficial interests in Restricted Global Securities). Upon receipt by the
Trustee of written instructions or such other form of instructions as is
customary for the Depositary, from the Depositary or its nominee, on behalf of
any person having a beneficial interest in an Unrestricted Global Security and,
in such form as is customary for the Depositary, from the Depositary or its
nominee on behalf of the person having such beneficial interest in the
Unrestricted Global Security (all of which may be submitted by facsimile or
electronically) a certification from the transferor (in substantially the form
set forth in the Transfer Certificate) to the effect that such beneficial
interest is being transferred to a person that the transferor reasonably
believes is a QIB in accordance with Rule 144A. The Trustee, as a Registrar and
Securities Custodian, shall reduce or cause to be reduced the aggregate
principal amount of the Unrestricted Global Security by the appropriate
principal amount and shall increase or cause to be increased the aggregate
principal amount of the Restricted Global Security by a like principal amount.
Such transfer shall otherwise be effected in accordance with the Applicable
Procedures. If no Restricted Global Security is then outstanding, the Company
shall execute and the Trustee shall, upon receipt of a Company Order (which the
Company agrees to deliver promptly), authenticate and deliver a Restricted
Global Security.

                  (e) Transfers of Certificated Securities for Beneficial
Interest in Global Securities. In the event that Certificated Securities are
issued in exchange for beneficial interests in Global Securities and,
thereafter, the events or conditions specified in Section 2.12(a)(1) which
required such exchange shall cease to exist, the Company shall mail notice to
the Trustee and to the Holders stating that Holders may exchange Certificated
Securities for interests in Global Securities by complying with the procedures
set forth in this Indenture and
<PAGE>   22
                                      -16-


briefly describing such procedures and the events or circumstances requiring
that such notice be given. Thereafter, if Certificated Securities are presented
by a Holder to a Registrar with a request:

                  (x) to register the transfer of such Certificated Securities
         to a person who will take delivery thereof in the form of a beneficial
         interest in a Global Security, which request shall specify whether such
         Global Security will be a Restricted Global Security or an Unrestricted
         Global Security; or

                  (y) to exchange such Certificated Securities for an equal
         principal amount of beneficial interests in a Global Security, which
         beneficial interests will be owned by the Holder transferring such
         Certificated Securities (provided that in the case of such an exchange,
         Restricted Certificated Securities may be exchanged only for Restricted
         Global Securities and Unrestricted Certificated Securities may be
         exchanged only for Unrestricted Global Securities), the Registrar shall
         register the transfer or make the exchange as requested by canceling
         such Certificated Security and causing, or directing the Securities
         Custodian to cause, the aggregate principal amount of the applicable
         Global Security to be increased accordingly and, if no such Global
         Security is then outstanding, the Company shall issue and the Trustee
         shall authenticate and deliver a new Global Security;

provided, however, that the Certificated Securities presented or surrendered for
registration of transfer or exchange:

                  (1) shall be duly endorsed or accompanied by a written
         instrument of transfer in accordance with the proviso to the first
         paragraph of Section 2.6(a);

                  (2) in the case of a Restricted Certificated Security to be
         transferred for a beneficial interest in an Unrestricted Global
         Security, such request shall be accompanied by the following additional
         information and documents, as applicable:

                            (i) if such Restricted Certificated Security is
                  being transferred pursuant to an effective registration
                  statement under the Securities Act, a certification to that
                  effect from such Holder (in substantially the form set forth
                  in the Transfer Certificate); or

                           (ii) if such Restricted Certificated Security is
                  being transferred pursuant to (i) an exemption from the
                  registration requirements of the Securities Act in accordance
                  with Rule 144 or (ii) pursuant to an exemption from the
                  registration requirements of the Securities Act (other than
                  pursuant to Rule 144A or Rule 144) and as a result of which,
                  in the case of a Security transferred pursuant to this clause
                  (ii), such Security shall cease to be a "restricted security"
                  within the meaning of Rule 144, a certification to that effect
                  from such Holder (in substantially the form set forth in the
                  Transfer Certificate), and, if the Company or the Registrar so
                  requests, a customary opinion of counsel, certificates and
                  other information reasonably acceptable to the Company and the
                  Trustee to the effect that such transfer is in compliance with
                  the registration requirements of the Securities Act;

                  (3) in the case of a Restricted Certificated Security to be
         transferred or exchanged for a beneficial interest in a Restricted
         Global Security, such request shall be accompanied by a certification
         from such Holder (in substantially the form set forth in the Transfer
         Certificate) to the effect that such Restricted Certificated Security
         is being transferred to a person the Holder reasonably believes is a
         QIB (which, in the case of an exchange, shall be such Holder) in
         accordance with Rule 144A;
<PAGE>   23
                                      -17-



                  (4) in the case of an Unrestricted Certificated Security to be
transferred or exchanged for a beneficial interest in an Unrestricted Global
Security, such request need not be accompanied by any additional information or
documents; and

                  (5) in the case of an Unrestricted Certificated Security to be
         transferred or exchanged for a beneficial interest in a Restricted
         Global Security, such request shall be accompanied by a certification
         from such Holder (in substantially the form set forth in the Transfer
         Certificate) to the effect that such Unrestricted Certificated Security
         is being transferred to a person the Holder reasonably believes is a
         QIB (which, in the case of an exchange, shall be such Holder) in
         accordance with Rule 144A.

                  (f) Legends.

         (1) Except as permitted by the following paragraphs (2) and (3), each
Global Security and Certificated Security (and all Securities issued in exchange
therefor or upon registration of transfer or replacement thereof) shall bear a
legend in substantially the form called for by footnote 2 to Exhibit A hereto
(each a "TRANSFER RESTRICTED SECURITY" for so long as it is required by this
Indenture to bear such legend). Each Transfer Restricted Security shall have
attached thereto a certificate (a "TRANSFER CERTIFICATE") in substantially the
form called for by footnote 5 to Exhibit A hereto.

         (2) Upon any sale or transfer of a Transfer Restricted Security (w)
after the expiration of the holding period applicable to sales of the Securities
under Rule 144(k) of the Securities Act, (x) pursuant to Rule 144, (y) pursuant
to an effective registration statement under the Securities Act or (z) pursuant
to any other available exemption (other than Rule 144A) from the registration
requirements of the Securities Act and as a result of which, in the case of a
Security transferred pursuant to this clause (z), such Security shall cease to
be a "restricted security" within the meaning of Rule 144:

                  (i) in the case of any Restricted Certificated Security, any
         Registrar shall permit the Holder thereof to exchange such Restricted
         Certificated Security for an Unrestricted Certificated Security, or
         (under the circumstances described in Section 2.12(e)) to transfer such
         Restricted Certificated Security to a transferee who shall take such
         Security in the form of a beneficial interest in an Unrestricted Global
         Security, and in each case shall rescind any restriction on the
         transfer of such Security; provided, however, that the Holder of such
         Restricted Certificated Security shall, in connection with such
         exchange or transfer, comply with the other applicable provisions of
         this Section 2.12; and

                  (ii) in the case of any beneficial interest in a Restricted
         Global Security, the Trustee shall permit the beneficial owner thereof
         to transfer such beneficial interest to a transferee who shall take
         such interest in the form of a beneficial interest in an Unrestricted
         Global Security and shall rescind any restriction on transfer of such
         beneficial interest; provided, that such Unrestricted Global Security
         shall continue to be subject to the provisions of Section 2.12(a)(2);
         and provided, further, that the owner of such beneficial interest
         shall, in connection with such transfer, comply with the other
         applicable provisions of this Section 2.12.

         (3) Upon the exchange, registration of transfer or replacement of
Securities not bearing the legend described in paragraph (1) above, the Company
shall execute, and the Trustee shall authenticate and deliver Securities that do
not bear such legend and that do not have a Transfer Certificate attached
thereto.
<PAGE>   24
                                      -18-



         (4) After the expiration of the holding period pursuant to Rule 144(k)
of the Securities Act, the Company may with the consent of the Holder of a
Restricted Global Security or Restricted Certificated Security, remove any
restriction of transfer on such Security, and the Company shall execute, and the
Trustee shall authenticate and deliver Securities that do not bear such legend
and that do not have a Transfer Certificate attached thereto.

                  (g) Transfers to the Company. Nothing in this Indenture or in
the Securities shall prohibit the sale or other transfer of any Securities
(including beneficial interests in Global Securities) to the Company or any of
its Subsidiaries, which Securities shall thereupon be cancelled in accordance
with the last sentence of Section 2.11.

SECTION 2.13.              CUSIP Numbers.

                  The Company in issuing the Securities may use "CUSIP" numbers
(if then generally in use), and, if so, the Trustee shall use "CUSIP" numbers in
notices of redemption or purchase as a convenience to Holders; provided that any
such notice may state that no representation is made as to the correctness of
such numbers either as printed on the Securities or as contained in any notice
of a redemption or purchase and that reliance may be placed only on the other
identification numbers printed on the Securities, and any such redemption or
purchase shall not be affected by any defect in or omission of such numbers. The
Company will promptly notify the Trustee of any change in the "CUSIP" numbers.

SECTION 2.14.              Defaulted Interest.

                  Any interest on any Security which is payable, but is not
punctually paid or duly provided for, on any interest payment date ("DEFAULTED
INTEREST"), shall forthwith cease to be payable to the Holder on the relevant
regular record date, and such Defaulted Interest may be paid by the Company as
follows. The Company may elect to make payment of any Defaulted Interest to the
Persons in whose names the Securities are registered at the close of business on
a special record date for the payment of such Defaulted Interest, which shall be
fixed in the following manner. The Company shall notify the Trustee in writing
of the amount of Defaulted Interest proposed to be paid on each Security and the
date of the proposed payment, and at the same time the Company shall deposit
with the Trustee an amount of money equal to the aggregate amount proposed to be
paid in respect of such Defaulted Interest or shall make arrangements
satisfactory to the Trustee for such deposit prior to the date of the proposed
payment, such money when deposited to be held in trust for the benefit of the
Persons entitled to such Defaulted Interest as in this section provided.
Thereupon the Company shall fix a special record date for the payment of such
Defaulted Interest which shall be not more than 15 days and not less than 10
days after the receipt by the Trustee of the notice of the proposed payment, and
notify the Trustee thereof. The Trustee shall, in the name and at the expense of
the Company, cause notice of the proposed payment of such Defaulted Interest and
the special record date therefor to be given to each Holder of Securities
pursuant to Section 12.2, not less than 10 days prior to such special record
date. Notice of the proposed payment of such defaulted interest and the special
record date therefor having been so mailed, such Defaulted Interest shall be
paid to the Persons in whose names the Securities are registered at the close of
business on such special record date.

                  Alternatively, the Company may elect to make payment of any
Defaulted Interest on the Securities in any other lawful manner not inconsistent
with the requirements of any securities exchange on which such Securities may be
listed, and upon any such notice as may be required by such exchange, if, after
notice given by the Company to the Trustee of the proposed payment pursuant to
this section, such manner of payment shall be deemed practicable by the Trustee.
<PAGE>   25
                                      -19-



                                    ARTICLE 3

                            REDEMPTION AND PURCHASES


SECTION 3.1.             Provisional and Optional Redemption; Notice to Trustee.

                  (a) The Company may redeem any portion of the Securities at
any time prior to June 6, 2004 (a "PROVISIONAL REDEMPTION"), upon giving notice
as set forth in Section 3.3, at a redemption price equal to $1,000 per $1,000
principal amount of the Securities redeemed plus accrued and unpaid interest, if
any (such amount, together with the "Make-Whole Payment" described below, the
"PROVISIONAL REDEMPTION PRICE"), to but excluding the date of redemption (the
"PROVISIONAL REDEMPTION DATE") if (1) the Closing Price of the Common Stock has
exceeded 150% of the Conversion Price for at least 20 Trading Days within a
period of any 30 consecutive Trading Days ending on the Trading Day prior to the
date of mailing of the notice of Provisional Redemption (the "NOTICE DATE"), and
(2) a shelf registration statement covering resales of the Securities and the
Common Stock issuable upon conversion thereof is effective and available for use
and is expected to remain effective and available for use for the 30 days
following the Provisional Redemption Date unless registration is no longer
required.

                  Upon any such Provisional Redemption, the Company shall make
an additional payment, at its option, in cash or Common Stock or a combination
of cash and Common Stock (the "MAKE-WHOLE PAYMENT") with respect to all
Securities called for redemption to Holders on the Notice Date in an amount
equal to $142.50 per $1,000 principal amount of the Securities, less the amount
of any interest actually paid (including, if the Provisional Redemption Date
occurs after a record date but before an interest payment date, any interest
paid or to be paid in connection with such interest payment date) on such
Securities prior to the Provisional Redemption Date. Payments made in Common
Stock will be valued at 97% of the average Closing Price of the Common Stock for
the five (5) Trading Days ending on the day prior to the Provisional Redemption
Date. The Company shall make the Make-Whole Payment on all Securities called for
Provisional Redemption, including those Securities converted into Common Stock
between the Notice Date and the Provisional Redemption Date.

                  (b) Except as set forth in clause (a) of this Section 3.1, the
Company shall not have the option to redeem the Securities pursuant to this
Section 3.1 prior to June 6, 2004. Thereafter, the Company shall have the option
to redeem any portion of the Securities (an "OPTIONAL REDEMPTION") upon giving
notice as set forth in Section 3.3 at the Redemption Prices (the "OPTIONAL
REDEMPTION PRICE") specified in paragraph 5 of the form of Security attached
hereto as Exhibit A, together with accrued interest up to but not including the
date of redemption (the "OPTIONAL REDEMPTION DATE"); provided that if the
Optional Redemption Date falls after an interest payment record date and on or
before an interest payment date, then the interest payment will be payable to
the Holders in whose name the Securities are registered at the close of business
on the relevant record date for payment of such interest.

                  If the Company elects to redeem Securities pursuant to clause
(a) or clause (b) of this Section 3.1 and paragraph 5 of the Securities, it
shall notify the Trustee, at the earlier of the time the Company notifies the
Holders of such redemption or 45 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 Securities to be redeemed. If
fewer than all of the Securities are to be redeemed, the record date relating to
such redemption shall be selected by the Company and given to the Trustee, which
record date shall not be less than ten days after the date of notice to the
Trustee.
<PAGE>   26
                                      -20-



                  The Trustee shall have no duty or obligation to determine
whether the Securities are eligible for Provisional Redemption, and may
conclusively rely on any such determination by the Company.

                  Any redemption pursuant to clause (a) or clause (b) of this
Section 3.1 shall be made pursuant to the applicable provisions of Sections 3.2
through 3.7 and Section 3.12 hereof.

SECTION 3.2.               Selection of Securities to Be Redeemed.

                  If fewer than all of the Securities are to be redeemed, the
Trustee shall, not more than 60 days prior to the Redemption Date, select the
Securities to be redeemed. The Trustee shall make the selection from the
Securities outstanding and not previously called for redemption, by lot, or in
its discretion, on a pro rata basis. Securities 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 Securities that have
denominations larger than $1,000. Provisions of this Indenture that apply to
Securities called for redemption also apply to portions of Securities called for
redemption.

                  If any Security selected for partial redemption is converted
in part before termination of the conversion right with respect to the portion
of the Security so selected, the converted portion of such Security shall be
deemed to be the portion selected for redemption. Securities which have been
converted during a selection of Securities to be redeemed shall be treated by
the Trustee as outstanding for the purpose of such selection.

SECTION 3.3.               Notice of Redemption.

                  At least 20 days but not more than 60 days before a Redemption
Date, the Company shall mail or cause to be mailed a notice of redemption to
each Holder of Securities to be redeemed at such Holder's address as it appears
on the Primary Registrar's books.

                  The notice shall identify the Securities (including CUSIP
numbers) 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 each Paying Agent and Conversion
         Agent;

                  (5) that Securities called for redemption must be presented
         and surrendered to a Paying Agent to collect the Redemption Price;

                  (6) that Holders who wish to convert Securities must surrender
         such Securities for conversion no later than the close of business on
         the Business Day immediately preceding the Redemption Date and must
         satisfy the other requirements in paragraph 8 of the Securities;

                  (7) that, unless the Company defaults in making the redemption
         payment, interest on Securities called for redemption shall cease
         accruing on and after the Redemption Date and the only re-
<PAGE>   27
                                      -21-



         maining right of the Holder shall be to receive payment of the
         Redemption Price, plus accrued interest, if any upon presentation and
         surrender to a Paying Agent of the Securities; and

                  (8) if any Security is being redeemed in part, the portion of
         the principal amount of such Security to be redeemed and that, after
         the Redemption Date, upon presentation and surrender of such Security,
         a new Security or Securities in aggregate principal amount equal to the
         unredeemed portion thereof will be issued.

                  If any of the Securities to be redeemed is in the form of a
Global Security, then the Company shall modify such notice to the extent
necessary to accord with the procedures of the Depositary applicable to
redemptions. At the Company's written request, which request shall (i) be
irrevocable once given and (ii) set forth all relevant information required by
clauses (1) through (8) of the preceding paragraph, 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, Securities called for
redemption become due and payable on the Redemption Date and at the Redemption
Price stated in the notice, together with accrued interest, if any, except for
Securities that are converted in accordance with the provisions of Article 4.
Upon presentation and surrender to a Paying Agent, Securities called for
redemption shall be paid at the Redemption Price, plus accrued interest up to
but not including the Redemption Date; provided if the Redemption Date is an
interest payment date, interest will be payable to the Holders in whose names
the Securities are registered at the close of business on the relevant record
dates for payment of such interest.

SECTION 3.5.               Deposit of Redemption Price.

                  The Company, prior to 11:00 a.m. New York City time, on the
Redemption Date, shall deposit with a Paying Agent (or, if the Company acts as
Paying Agent, shall segregate and hold in trust) money sufficient to pay the
Redemption Price of and accrued interest on all Securities to be redeemed on
that date, other than Securities or portions thereof called for redemption on
that date which have been delivered by the Company to the Trustee for
cancellation or have been converted. The Paying Agent shall return to the
Company any money not required for that purpose because of the conversion of
Securities pursuant to Article 4 or, if such money is then held by the Company
in trust and is not required for such purpose, it shall be discharged from the
trust.

SECTION 3.6.               Securities Redeemed in Part.

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

SECTION 3.7.               Conversion Arrangement on Call for Redemption.

                  In connection with any redemption of Securities, the Company
may arrange for the purchase and conversion of any Securities called for
redemption by an agreement with one or more investment bankers or other
purchasers to purchase such Securities by paying to a Paying Agent (other than
the Company or any of its Affiliates) in trust for the Holders, on or before
11:00 a.m. New York City time on the Redemption Date, an amount that, together
with any amounts deposited with such Paying Agent by the Company for the
redemption
<PAGE>   28
                                      -22-



of such Securities, is not less than the Redemption Price, together with
interest accrued to, but not including, the Redemption Date, of such Securities.
Notwithstanding anything to the contrary contained in this Article 3, the
obligation of the Company to pay the Redemption Price of such Securities,
including all accrued interest, shall be deemed to be satisfied and discharged
to the extent such amount is so paid by such purchasers; provided, however, that
nothing in this Section 3.7 shall relieve the Company of its obligation to pay
the Redemption Price, plus accrued interest to but excluding the relevant
Redemption Date, on Securities called for redemption. If such an agreement with
one or more investment banks or other purchasers is entered into, any Securities
called for redemption and not surrendered for conversion by the Holders thereof
prior to the relevant Redemption Date may, at the option of the Company upon
written notice to the Trustee, be deemed, to the fullest extent permitted by
law, acquired by such purchasers from such Holders and (notwithstanding anything
to the contrary contained in Article 4) surrendered by such purchasers for
conversion, all as of 11:00 a.m. New York City time on the Redemption Date,
subject to payment of the above amount as aforesaid. The Paying Agent shall hold
and pay to the Holders whose Securities are selected for redemption any such
amount paid to it for purchase in the same manner as it would money deposited
with it by the Company for the redemption of Securities. Without the Paying
Agent's prior written consent, no arrangement between the Company and such
purchasers for the purchase and conversion of any Securities shall increase or
otherwise affect any of the powers, duties, responsibilities or obligations of
the Paying Agent as set forth in this Indenture, and the Company agrees to
indemnify the Paying Agent from, and hold it harmless against, any loss,
liability or expense arising out of or in connection with any such arrangement
for the purchase and conversion of any Securities between the Company and such
purchasers, including the costs and expenses incurred by the Paying Agent in the
defense of any claim or liability arising out of or in connection with the
exercise or performance of any of its powers, duties, responsibilities or
obligations under this Indenture.

SECTION 3.8.    Purchase of Securities at Option of the Holder upon Change in
                Control.


                  (a) If at any time that Securities remain outstanding there
shall occur a Change in Control, Securities shall be purchased by the Company at
the option of the Holders thereof as of the date that is 30 Business Days after
the occurrence of the Change in Control (the "CHANGE IN CONTROL PURCHASE DATE")
at a purchase price equal to the principal amount of the Securities, plus
accrued and unpaid interest to, but excluding, the Change in Control Purchase
Date (the "CHANGE IN CONTROL PURCHASE PRICE"), subject to satisfaction by or on
behalf of any Holder of the requirements set forth in subsection (c) of this
Section 3.8.

                  A "Change in Control" shall be deemed to have occurred if any
of the following occurs after the date hereof:

                  (1) any "person" or "group" (as such terms are defined below)
         is or becomes the "beneficial owner" (as defined below), directly or
         indirectly, of shares of Voting Stock of the Company representing 50%
         or more of the total voting power of all outstanding classes of Voting
         Stock of the Company or such person or group has the power, directly or
         indirectly, to elect a majority of the members of the Board of
         Directors of the Company; or

                  (2) the Company consolidates with, or merges with or into,
         another Person or the Company sells, assigns, conveys, transfers,
         leases or otherwise disposes of all or substantially all of the assets
         of the Company, or any Person consolidates with, or merges with or
         into, the Company, in any such event other than pursuant to a
         transaction in which the Persons that "beneficially owned" (as defined
         below), directly or indirectly, shares of Voting Stock of the Company
         immediately prior to such transaction "beneficially own" (as defined
         below), directly or indirectly, shares of Voting Stock of the
<PAGE>   29
                                      -23-



         Company representing at least a majority of the total voting power of
         all outstanding classes of Voting Stock of the surviving or transferee
         Person; or

                  (3) there shall occur the liquidation or dissolution of the
         Company.

For the purpose of the definition of "Change in Control", (i) "person" and
"group" have the meanings given such terms under Section 13(d) and 14(d) of the
Exchange Act or any successor provision to either of the foregoing, and the term
"group" includes any group acting for the purpose of acquiring, holding or
disposing of securities within the meaning of Rule 13d-5(b)(1) under the
Exchange Act (or any successor provision thereto), (ii) a "beneficial owner"
shall be determined in accordance with Rule 13d-3 under the Exchange Act, as in
effect on the date of this Indenture, except that the number of shares of Voting
Stock of the Company shall be deemed to include, in addition to all outstanding
shares of Voting Stock of the Company and Unissued Shares deemed to be held by
the "person" or "group" (as such terms are defined above) or other Person with
respect to which the Change in Control determination is being made, all Unissued
Shares deemed to be held by all other Persons, and (iii) the terms "beneficially
owned" and "beneficially own" shall have meanings correlative to that of
"beneficial owner." The term "Unissued Shares" means shares of Voting Stock not
outstanding that are subject to options, warrants, rights to purchase or
conversion privileges exercisable within 60 days of the date of determination of
a Change in Control.

                  Notwithstanding anything to the contrary set forth in this
Section 3.8, a Change in Control will not be deemed to have occurred if either:

                  (1) the Closing Price of the Common Stock for any five Trading
         Days during the ten Trading Days immediately preceding the Change in
         Control is at least equal to 105% of the Conversion Price in effect on
         such Trading Day; or

                  (2) in the case of a merger or consolidation, all of the
         consideration (excluding cash payments for fractional shares in the
         merger or consolidation constituting the Change in Control) consists of
         common stock traded on a United States national securities exchange or
         quoted on the Nasdaq National Market (or which will be so traded or
         quoted when issued or exchanged in connection with such Change In
         Control) and as a result of such transaction or transactions the
         Securities become convertible solely into such common stock.

                  (b) Within 10 Business Days after the occurrence of a Change
in Control, the Company shall mail a written notice of the Change in Control to
the Trustee (and the Paying Agent if the Trustee is not then acting as Paying
Agent) and to each Holder (and to beneficial owners as required by applicable
law). The notice shall include the form of a Change in Control Purchase Notice
to be completed by the Holder and shall state:

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

                  (2) the date by which the Change in Control Purchase Notice
         pursuant to this Section 3.8 must be given;

                  (3) the Change in Control Purchase Date;

                  (4) the Change in Control Purchase Price;
<PAGE>   30
                                      -24-



                  (5) briefly, the conversion rights of the Securities;

                  (6) the name and address of each Paying Agent and Conversion
         Agent;

                  (7) the Conversion Price and any adjustments thereto;

                  (8) that Securities as to which a Change in Control Purchase
         Notice has been given may be converted into Common Stock pursuant to
         Article 4 of this Indenture only to the extent that the Change in
         Control Purchase Notice has been withdrawn in accordance with the terms
         of this Indenture;

                  (9) the procedures that the Holder must follow to exercise
         rights under this Section 3.8;

                  (10) the procedures for withdrawing a Change in Control
         Purchase Notice, including a form of notice of withdrawal; and

                  (11) that the Holder must satisfy the requirements set forth
         in the Securities in order to convert the Securities.

                  If any of the Securities is in the form of a Global Security,
then the Company shall modify such notice to the extent necessary to accord with
the procedures of the Depositary applicable to the repurchase of Global
Securities.

                  (c) A Holder may exercise its rights specified in subsection
(a) of this Section 3.8 upon delivery of a written notice (which shall be in
substantially the form included in Exhibit A hereto and which may be delivered
by letter, overnight courier, hand delivery, facsimile transmission or in any
other written form and, in the case of Global Securities, may be delivered
electronically or by other means in accordance with the Depositary's customary
procedures) of the exercise of such rights (a "CHANGE IN CONTROL PURCHASE
NOTICE") to any Paying Agent at any time prior to the close of business on the
Business Day next preceding the Change in Control Purchase Date.

                  The delivery of such Security to any Paying Agent (together
with all necessary endorsements) at the office of such Paying Agent shall be a
condition to the receipt by the Holder of the Change in Control Purchase Price
therefor.

                  The Company shall purchase from the Holder thereof, pursuant
to this Section 3.8, a portion of a Security if the principal amount of such
portion is $1,000 or an integral multiple of $1,000. Provisions of the Indenture
that apply to the purchase of all of a Security pursuant to Sections 3.8 through
3.13 also apply to the purchase of such portion of such Security.

                  Notwithstanding anything herein to the contrary, any Holder
delivering to a Paying Agent the Change in Control Purchase Notice contemplated
by this subsection (c) shall have the right to withdraw such Change in Control
Purchase Notice in whole or in a portion thereof that is a principal amount of
$1,000 or in an integral multiple thereof at any time prior to the close of
business on the Business Day next preceding the Change in Control Purchase Date
by delivery of a written notice of withdrawal to the Paying Agent in accordance
with Section 3.9.

                  A Paying Agent shall promptly notify the Company of the
receipt by it of any Change in Control Purchase Notice or written withdrawal
thereof.
<PAGE>   31
                                      -25-



                  Anything herein to the contrary notwithstanding, in the case
of Global Securities, any Change in Control Purchase Notice may be delivered or
withdrawn and such Securities may be surrendered or delivered for purchase in
accordance with the Applicable Procedures as in effect from time to time.

SECTION 3.9.               Effect of Change in Control Purchase Notice.

                  Upon receipt by any Paying Agent of the Change in Control
Purchase Notice specified in Section 3.8(c), the Holder of the Security in
respect of which such Change in Control Purchase Notice was given shall (unless
such Change in Control Purchase Notice is withdrawn as specified below)
thereafter be entitled to receive the Change in Control Purchase Price with
respect to such Security. Such Change in Control Purchase Price shall be paid to
such Holder promptly following the later of (a) the Change in Control Purchase
Date with respect to such Security (provided the conditions in Section 3.8(c)
have been satisfied) and (b) the time of delivery of such Security to a Paying
Agent by the Holder thereof in the manner required by Section 3.8(c). Securities
in respect of which a Change in Control 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 Change in Control Purchase Notice unless such
Change in Control Purchase Notice has first been validly withdrawn.

                  A Change in Control Purchase Notice may be withdrawn by means
of a written notice (which may be delivered by letter, overnight courier, hand
delivery, facsimile transmission or in any other written form and, in the case
of Global Securities, may be delivered electronically or by other means in
accordance with the Depositary's customary procedures) of withdrawal delivered
by the Holder to a Paying Agent at any time prior to the close of business on
the Business Day immediately preceding the Change in Control Purchase Date,
specifying the principal amount of the Security or portion thereof (which must
be a principal amount of $1,000 or an integral multiple of $1,000 in excess
thereof) with respect to which such notice of withdrawal is being submitted.

SECTION 3.10.              Deposit of Change in Control Purchase Price.

                  On or before 11:00 a.m. New York City time on the Change in
Control Purchase Date, the Company shall deposit with the Trustee or with a
Paying Agent (other than the Company or an Affiliate of the Company) an amount
of money (in immediately available funds if deposited on such Business Day)
sufficient to pay the aggregate Change in Control Purchase Price of all the
Securities or portions thereof that are to be purchased as of such Change in
Control Purchase Date. The manner in which the deposit required by this Section
3.10 is made by the Company shall be at the option of the Company, provided that
such deposit shall be made in a manner such that the Trustee or a Paying Agent
shall have immediately available funds on the Change in Control Purchase Date.

                  If a Paying Agent holds, in accordance with the terms hereof,
money sufficient to pay the Change in Control Purchase Price of any Security for
which a Change in Control Purchase Notice has been tendered and not withdrawn in
accordance with this Indenture then, on the Change in Control Purchase Date,
such Security will cease to be outstanding and the rights of the Holder in
respect thereof shall terminate (other than the right to receive the Change in
Control Purchase Price as aforesaid). The Company shall publicly announce the
principal amount of Securities purchased as a result of such Change in Control
on or as soon as practicable after the Change in Control Purchase Date.
<PAGE>   32
                                      -26-



SECTION 3.11.              Securities Purchased in Part.

                  Any Security that is to be purchased only in part shall be
surrendered at the office of a Paying Agent and promptly after the Change in
Control Purchase Date the Company shall execute and the Trustee shall
authenticate and deliver to the Holder of such Security, without service charge,
a new Security or Securities, 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 Security so
surrendered that is not purchased.

SECTION 3.12.              Compliance with Securities Laws upon Purchase of
                           Securities.

                  In connection with any offer to purchase or purchase of
Securities under Section 3.8, the Company shall (a) comply with Rule 13e-4 and
Rule 14e-1 (or any successor to either such Rule), if applicable, under the
Exchange Act, (b) file the related Schedule TO (or any successor or similar
schedule, form or report) if required under the Exchange Act, and (c) otherwise
comply with all federal and state securities laws in connection with such offer
to purchase or purchase of Securities, all so as to permit the rights of the
Holders and obligations of the Company under Sections 3.8 through 3.11 to be
exercised in the time and in the manner specified therein.

SECTION 3.13.              Repayment to the Company.

                  To the extent that the aggregate amount of cash deposited by
the Company pursuant to Section 3.10 exceeds the aggregate Change in Control
Purchase Price together with interest, if any, thereon of the Securities or
portions thereof that the Company is obligated to purchase, then promptly after
the Change in Control Purchase Date the Trustee or a Paying Agent, as the case
may be, shall return any such excess cash (including any interest thereon) to
the Company.

                                    ARTICLE 4

                                   CONVERSION

SECTION 4.1.               Conversion Privilege.

                  Subject to the further provisions of this Section 4.1, a
Holder of a Security may, at the Holder's option, convert the principal amount
of such Security (or any portion thereof equal to $1,000 or any integral
multiple of $1,000 in excess thereof) into Common Stock at any time prior to the
close of business on the Final Maturity Date, at the Conversion Price then in
effect; provided, however, that, if such Security is called for redemption or
submitted or presented for purchase pursuant to Article 3, such conversion right
shall terminate at the close of business on the Business Day immediately
preceding the Redemption Date or Change in Control Purchase Date, as the case
may be, for such Security or such earlier date as the Holder presents such
Security for redemption or for purchase (unless the Company shall Default in
making the redemption payment or Change in Control Purchase Price 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 Security is redeemed or purchased, as
the case may be). The number of shares of Common Stock issuable upon conversion
of a Security shall be determined by dividing the principal amount of the
Security or portion thereof surrendered for conversion by the Conversion
<PAGE>   33
                                      -27-



Price in effect on the Conversion Date. The initial Conversion Price is set
forth in paragraph 8 of the Securities and is subject to adjustment as provided
in this Article 4.

                  Provisions of this Indenture that apply to conversion of all
of a Security also apply to conversion of a portion of a Security.

                  A Security in respect of which a Holder has delivered a Change
in Control Purchase Notice pursuant to Section 3.8(c) exercising the option of
such Holder to require the Company to purchase such Security may be converted
only if such Change in Control Purchase Notice is withdrawn by a written notice
of withdrawal delivered to a Paying Agent prior to the close of business on the
Business Day immediately preceding the Change in Control Purchase Date in
accordance with Section 3.9.

                  A Holder of Securities is not entitled to any rights of a
holder of Common Stock until such Holder has converted its Securities to Common
Stock, and only to the extent such Securities are deemed to have been converted
into Common Stock pursuant to this Article 4.

SECTION 4.2.               Conversion Procedure.

                  To convert a Security, a Holder must (a) complete and manually
sign the conversion notice on the back of the Security and deliver such notice
to a Conversion Agent, (b) surrender the Security to a Conversion Agent, (c)
furnish appropriate endorsements and transfer documents if required by a
Registrar or a Conversion Agent, and (d) pay any transfer or similar tax, if
required. 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 a Conversion Agent a certificate for
the number of whole shares of Common Stock issuable upon the conversion and cash
in lieu of any fractional shares pursuant to Section 4.3. Anything herein to the
contrary notwithstanding, in the case of Global Securities, conversion notices
may be delivered and such Securities may be surrendered for conversion in
accordance with the Applicable Procedures as in effect from time to time.

                  The person in whose name the Common Stock certificate is
registered shall be deemed to be a stockholder of record on the Conversion Date;
provided, however, that no surrender of a Security on any date when the stock
transfer books of the Company shall be closed shall be effective to constitute
the person or persons entitled to receive the shares of Common Stock upon such
conversion as the record holder or holders of such shares of Common Stock on
such date, but such surrender shall be effective to constitute the person or
persons entitled to receive such shares of Common Stock as the record holder or
holders thereof for all purposes at the close of business on the next succeeding
day on which such stock transfer books are open; provided, further, that such
conversion shall be at the Conversion Price in effect on the Conversion Date as
if the stock transfer books of the Company had not been closed. Upon conversion
of a Security, such person shall no longer be a Holder of such Security. No
payment or adjustment will be made for dividends or distributions on shares of
Common Stock issued upon conversion of a Security.

                  Securities so surrendered for conversion (in whole or in part)
during the period from the close of business on any regular record date to the
opening of business on the next succeeding interest payment date (excluding
Securities or portions thereof which are either (i) called for redemption or
(ii) subject to purchase following a Change in Control, in either case, on the
date during the period beginning at the close of business on a regular record
date and ending at the opening of business on the first Business Day after the
next succeeding interest payment date, or if such interest payment date is not a
Business Day, the second such Business Day) shall also be accompanied by payment
in funds acceptable to the Company of an amount equal to the interest
<PAGE>   34
                                      -28-



payable on such interest payment date on the principal amount of such Security
then being converted, and such interest shall be payable to such registered
Holder notwithstanding the conversion of such Security, subject to the
provisions of this Indenture relating to the payment of defaulted interest by
the Company. Except as otherwise provided in this Section 4.2, no payment or
adjustment will be made for accrued interest on a converted Security. If the
Company defaults in the payment of interest payable on such interest payment
date, the Company shall promptly repay such funds to such Holder.

                  Nothing in this Section shall affect the right of a Holder in
whose name any Security is registered at the close of business on a record date
to receive the interest payable on such Security on the related interest payment
date in accordance with the terms of this Indenture and the Securities. If a
Holder converts more than one Security at the same time, the number of shares of
Common Stock issuable upon the conversion shall be based on the aggregate
principal amount of Securities converted.

                  Upon surrender of a Security that is converted in part, the
Company shall execute, and the Trustee shall authenticate and deliver to the
Holder, a new Security equal in principal amount to the unconverted portion of
the Security surrendered.

SECTION 4.3.               Fractional Shares.

                  The Company will not issue fractional shares of Common Stock
upon conversion of Securities. In lieu thereof, the Company will pay an amount
in cash based upon the Closing Price of the Common Stock on the Trading Day
immediately prior to the Conversion Date.

SECTION 4.4.               Taxes on Conversion.

                  If a Holder converts a Security, the Company shall pay any
documentary, stamp or similar issue or transfer tax due on the issue of shares
of Common Stock upon such conversion. However, the Holder shall pay any such tax
which is due because the Holder requests the shares to be issued in a name other
than the Holder's name. The Conversion Agent may refuse to deliver the
certificate representing the Common Stock being issued in a name other than the
Holder's name until the Conversion Agent receives a sum sufficient to pay any
tax which will be due because the shares are to be issued in a name other than
the Holder's name. Nothing herein shall preclude any tax withholding required by
law or regulation.

SECTION 4.5.               Company to Provide Stock.

                  The Company shall, prior to issuance of any Securities
hereunder, and from time to time as may be necessary, reserve, out of its
authorized but unissued Common Stock, a sufficient number of shares of Common
Stock to permit the conversion of all outstanding Securities into shares of
Common Stock.

                  All shares of Common Stock delivered upon conversion of the
Securities shall be newly issued shares, shall be duly authorized, validly
issued, fully paid and nonassessable and shall be free from preemptive rights
and free of any lien or adverse claim.

                  The Company will endeavor promptly to comply with all federal
and state securities laws regulating the offer and delivery of shares of Common
Stock upon conversion of Securities, if any, and will list or cause to have
quoted such shares of Common Stock on each national securities exchange or on
the Nasdaq National Market or other over-the-counter market or such other market
on which the Common Stock is then listed or quoted; provided, however, that if
rules of such automated quotation system or exchange permit the
<PAGE>   35
                                      -29-



Company to defer the listing of such Common Stock until the first conversion of
the Notes into Common Stock in accordance with the provisions of this Indenture,
the Company covenants to list such Common Stock issuable upon conversion of the
Notes in accordance with the requirements of such automated quotation system or
exchange at such time.

SECTION 4.6.               Adjustment of Conversion Price.

                  The conversion price as stated in paragraph 8 of the
Securities (the "CONVERSION PRICE") shall be adjusted from time to time by the
Company as follows:

                  (a) In case the Company shall (i) pay a dividend on its Common
         Stock in shares of Common Stock, (ii) make a distribution on its Common
         Stock in shares of Common Stock, (iii) subdivide its outstanding Common
         Stock into a greater number of shares, or (iv) combine its outstanding
         Common Stock into a smaller number of shares, the Conversion Price in
         effect immediately prior thereto shall be adjusted so that the Holder
         of any Security thereafter surrendered for conversion shall be entitled
         to receive that number of shares of Common Stock which it would have
         owned had such Security been converted immediately prior to the
         happening of such event. 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 subdivision or
         combination.

                  (b) In case the Company shall issue rights or warrants to all
         or substantially all holders of its Common Stock entitling them (for a
         period commencing no earlier than the record date described below and
         expiring not more than 60 days after such record date) to subscribe for
         or purchase shares of Common Stock (or securities convertible into
         Common Stock) at a price per share (or having a conversion price per
         share) less than the Current Market Price Per Share of Common Stock on
         the record date for the determination of stockholders entitled to
         receive such rights or warrants, the Conversion Price in effect
         immediately prior thereto 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 (x)
         the numerator shall be the number of shares of Common Stock outstanding
         on such record date plus the number of shares which the aggregate
         offering price of the total number of shares of Common Stock so offered
         (or the aggregate conversion price of the convertible securities so
         offered, which shall be determined by multiplying the number of shares
         of Common Stock issuable upon conversion of such convertible securities
         by the conversion price per share of Common Stock pursuant to the terms
         of such convertible securities) would purchase at the Current Market
         Price Per Share of Common Stock on such record date, and of which (y)
         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 adjustment shall be made successively
         whenever any such rights or warrants are issued, and shall become
         effective immediately after such record date. If at the end of the
         period during which such rights or warrants are exercisable not all
         rights or warrants shall have been exercised, the adjusted Conversion
         Price shall be immediately readjusted to what it would have been based
         upon 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 or
         substantially all holders of its Common Stock any shares of capital
         stock of the Company (other than Common Stock), evidences of
         indebtedness or other non-cash assets (including securities of any
         person other than the Company but excluding
<PAGE>   36
                                      -30-



         (1) dividends or distributions paid exclusively in cash or (2)
         dividends or distributions referred to in subsection (a) of this
         Section 4.6), or shall distribute to all or substantially all holders
         of its Common Stock rights or warrants to subscribe for or purchase any
         of its securities (excluding those rights and warrants referred to in
         subsection (b) of this Section 4.6 and also excluding the distribution
         of rights to all holders of Common Stock pursuant to the adoption of a
         stockholders rights plan or the detachment of such rights under the
         terms of such stockholder rights plan), then in each such case the
         Conversion Price shall be adjusted so that the same shall equal the
         price determined by multiplying the current Conversion Price by a
         fraction of which the numerator shall be the Current Market Price Per
         Share of the Common Stock on the record date mentioned below less the
         fair market value on such record date (as reasonably determined in good
         faith by the Board of Directors, whose determination shall be
         conclusive evidence of such fair market value and which shall be
         evidenced by an Officers' Certificate delivered to the Trustee) of the
         portion of the capital stock, evidences of indebtedness or other
         non-cash assets so distributed or of such rights or warrants applicable
         to one share of Common Stock (determined on the basis of the number of
         shares of Common Stock outstanding on the record date), and of which
         the denominator shall be the Current Market Price Per Share of the
         Common Stock on such record date. Such adjustment shall be made
         successively whenever any such distribution is made and shall become
         effective immediately after the record date for the determination of
         shareholders entitled to receive such distribution.

                  (d) In case the Company shall, by dividend or otherwise, at
         any time distribute (a "TRIGGERING DISTRIBUTION") to all or
         substantially all holders of its Common Stock cash in an aggregate
         amount that, together with the aggregate amount of (A) any cash and the
         fair market value (as reasonably determined in good faith by the Board
         of Directors, whose determination shall be conclusive evidence thereof
         and which shall be evidenced by an Officers' Certificate delivered to
         the Trustee) of any other consideration payable in respect of any
         tender offer by the Company or a Subsidiary of the Company for Common
         Stock consummated within the 12 months preceding the date of payment of
         the Triggering Distribution and in respect of which no Conversion Price
         adjustment pursuant to this Section 4.6 has been made and (B) all other
         cash distributions to all or substantially all holders of its Common
         Stock made within the 12 months preceding the date of payment of the
         Triggering Distribution and in respect of which no Conversion Price
         adjustment pursuant to this Section 4.6 has been made, exceeds an
         amount equal to 10.0% of the product of the Current Market Price Per
         Share of Common Stock on the Business Day (the "DETERMINATION DATE")
         immediately preceding the day on which such Triggering Distribution is
         declared by the Company multiplied by the number of shares of Common
         Stock outstanding on the Determination Date (excluding shares held in
         the treasury of the Company), the Conversion Price shall be reduced so
         that the same shall equal the price determined by multiplying such
         Conversion Price in effect immediately prior to the Determination Date
         by a fraction of which the numerator shall be the Current Market Price
         Per Share of the Common Stock on the Determination Date less the sum of
         the aggregate amount of cash and the aggregate fair market value (as
         reasonably determined in good faith by the Board of Directors, whose
         determination shall be conclusive evidence of such fair market value
         and which shall be evidenced by an Officers' Certificate delivered to
         the Trustee) of any such other consideration so distributed, paid or
         payable within such 12 months (including, without limitation, the
         Triggering Distribution) applicable to one share of Common Stock
         (determined on the basis of the number of shares of Common Stock
         outstanding on the Determination Date) and the denominator shall be
         such Current Market Price Per Share of the Common Stock on the
         Determination Date, such reduction to become effective immediately
         prior to the opening of business on the day following the date on which
         the Triggering Distribution is paid.
<PAGE>   37
                                      -31-



                  (e) (1) In case any tender offer made by the Company or any of
         its Subsidiaries for Common Stock shall expire and such tender offer
         (as amended upon the expiration thereof) shall involve the payment of
         aggregate consideration in an amount (determined as the sum of the
         aggregate amount of cash consideration and the aggregate fair market
         value (as reasonably determined in good faith by the Board of
         Directors, whose determination shall be conclusive evidence thereof and
         which shall be evidenced by an Officers' Certificate delivered to the
         Trustee thereof) of any other consideration) that, together with the
         aggregate amount of (A) any cash and the fair market value (as
         reasonably determined in good faith by the Board of Directors, whose
         determination shall be conclusive evidence thereof and which shall be
         evidenced by an Officers' Certificate delivered to the Trustee) of any
         other consideration payable in respect of any other tender offers by
         the Company or any Subsidiary of the Company for Common Stock
         consummated within the 12 months preceding the date of the Expiration
         Date (as defined below) and in respect of which no Conversion Price
         adjustment pursuant to this Section 4.6 has been made and (B) all cash
         distributions to all or substantially all holders of its Common Stock
         made within the 12 months preceding the Expiration Date and in respect
         of which no Conversion Price adjustment pursuant to this Section 4.6
         has been made, exceeds an amount equal to 10.0% of the product of the
         Current Market Price Per Share of Common Stock as of the last date (the
         "EXPIRATION DATE") tenders could have been made pursuant to such tender
         offer (as it may be amended) (the last time at which such tenders could
         have been made on the Expiration Date is hereinafter sometimes called
         the "EXPIRATION TIME") multiplied by the number of shares of Common
         Stock outstanding (including tendered shares but excluding any shares
         held in the treasury of the Company) at the Expiration Time, then,
         immediately prior to the opening of business on the day after the
         Expiration Date, the Conversion Price shall be reduced so that the same
         shall equal the price determined by multiplying the Conversion Price in
         effect immediately prior to close of business on the Expiration Date by
         a fraction of which the numerator shall be the product of the number of
         shares of Common Stock outstanding (including tendered shares but
         excluding any shares held in the treasury of the Company) at the
         Expiration Time multiplied by the Current Market Price Per Share of the
         Common Stock on the Trading Day next succeeding the Expiration Date and
         the denominator shall be the sum of (x) the aggregate consideration
         (determined as aforesaid) payable to stockholders based on the
         acceptance (up to any maximum specified in the terms of the tender
         offer) of all shares validly tendered and not withdrawn as of the
         Expiration Time (the shares deemed so accepted, up to any such maximum,
         being referred to as the "PURCHASED Shares") and (y) the product of the
         number of shares of Common Stock outstanding (less any Purchased Shares
         and excluding any shares held in the treasury of the Company) at the
         Expiration Time and the Current Market Price Per Share of Common Stock
         on the Trading Day next succeeding the Expiration Date, such reduction
         to become effective immediately prior to the opening of business on the
         day following the Expiration Date. In the event that the Company is
         obligated to purchase shares pursuant to any such tender offer, but the
         Company is permanently prevented by applicable law from effecting any
         or all such purchases or any or all such purchases are rescinded, the
         Conversion Price shall again be adjusted to be the Conversion Price
         which would have been in effect based upon the number of shares
         actually purchased. If the application of this Section 4.6(e) to any
         tender offer would result in an increase in the Conversion Price, no
         adjustment shall be made for such tender offer under this Section
         4.6(e).

                  (2) For purposes of Section 4.6(d) and 4.6(e), the term
         "tender offer" shall mean and include both tender offers and exchange
         offers (within the meaning of U.S. Federal securities laws), all
         references to "purchases" of shares in tender offers (and all similar
         references) shall mean and include both the purchase of shares in
         tender offers and the acquisition of shares pursuant to exchange
         offers, and all references to "tendered shares" (and all similar
         references) shall mean and include shares tendered in both tender
         offers and exchange offers.
<PAGE>   38
                                      -32-



                  (f) For the purpose of any computation under subsections (b),
         (c), (d) and (e) of this Section 4.6, the current market price per
         share of Common Stock (the "CURRENT MARKET PRICE PER SHARE") on any
         date shall be deemed to be the average of the daily Closing Prices for
         the 30 consecutive Trading Days commencing 45 Trading Days before (i)
         the Determination Date or the Expiration Date, as the case may be, with
         respect to distributions or tender offers under subsection (e) of this
         Section 4.6 or (ii) the record date with respect to distributions,
         issuances or other events requiring such computation under subsection
         (b), (c) or (d) of this Section 4.6. The Closing Price for each day
         (the "CLOSING PRICE") shall be the last reported sales price or, in
         case no such reported sale takes place on such date, the average of the
         reported closing bid and asked prices in either case on the New York
         Stock Exchange (the "NYSE") or the Nasdaq National Market (the "NNM"),
         as applicable, or, if the Common Stock is not listed or admitted to
         trading on the NYSE or the NNM, the principal national securities
         exchange or quotation system on which the Common Stock is quoted or
         listed or admitted to trading or, if not quoted or listed or admitted
         to trading on any national securities exchange or quotation 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. If no such
         prices are available, the Current Market Price Per Share shall be the
         fair value of a share of Common Stock as reasonably determined in good
         faith by the Board of Directors (which shall be evidenced by an
         Officers' Certificate delivered to the Trustee).

                  (g) In any case in which this Section 4.6 shall require that
         an adjustment be made following a record date or a Determination Date
         or Expiration Date, as the case may be, established for purposes of
         this 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 4.9) issuing to the Holder of any
         Security converted after such record date or Determination Date or
         Expiration Date the shares of Common 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 agent to issue
         due bills or other appropriate evidence prepared by the Company of the
         right to receive such shares. If any distribution in respect of which
         an adjustment to the Conversion Price is required to be made as of the
         record date or Determination Date or Expiration Date therefor is not
         thereafter made or paid by the Company for any reason, the Conversion
         Price shall be readjusted to the Conversion Price which would then be
         in effect if such record date had not been fixed or such effective date
         or Determination Date or Expiration Date had not occurred.

SECTION 4.7.               No Adjustment.

                  No adjustment in the Conversion Price shall be required unless
the adjustment would require an increase or decrease of at least 1% in the
Conversion Price 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 need be made for issuances of Common Stock
pursuant to a Company plan for reinvestment of dividends or interest or for a
change in the par value or a change to no par value of the Common Stock.
<PAGE>   39
                                      -33-



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

SECTION 4.8.               Adjustment for Tax Purposes.

                  The Company shall be entitled to make such reductions in the
Conversion Price, in addition to those required by Section 4.6, as it in its
discretion shall determine to be advisable in order that any stock dividends,
subdivisions of shares, distributions of rights to purchase stock or securities
or distributions of securities convertible into or exchangeable for stock
hereafter made by the Company to its stockholders shall not be taxable.

SECTION 4.9.               Notice of Adjustment.

                  Whenever the Conversion Price or conversion privilege is
adjusted, the Company shall promptly mail to Securityholders 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. Unless and
until the Trustee shall receive an Officers' Certificate setting forth an
adjustment of the Conversion Price, the Trustee may assume without inquiry that
the Conversion Price has not been adjusted and that the last Conversion Price of
which it has knowledge remains in effect.

SECTION 4.10.              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 property and assets to, another corporation
         and shareholders of the Company must approve the transaction; or

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

the Company shall mail to Holders and file with the Trustee a notice stating the
proposed record or effective date, as the case may be. The Company shall mail
the notice at least ten days before such date. Failure to mail such notice or
any defect therein shall not affect the validity of any transaction referred to
in clause (1), (2) or (3) of this Section 4.10.

SECTION 4.11.              Effect of Reclassification, Consolidation, Merger or
                           Sale on Conversion Privilege.

                  If any of the following shall occur, namely: (a) any
reclassification or change of shares of Common Stock issuable upon conversion of
the Securities (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, or any other change for which an adjustment is provided in Section
4.6); (b) any consolidation or merger or combination 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 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) in, outstanding shares of
<PAGE>   40
                                      -34-


Common Stock; or (c) any sale or conveyance as an entirety or substantially as
an entirety of the property and assets of the Company, directly or indirectly,
to any person, then the Company, or such successor, purchasing or transferee
corporation, as the case may be, shall, as a condition precedent to such
reclassification, change, combination, consolidation, merger, sale or
conveyance, execute and deliver to the Trustee a supplemental indenture
providing that the Holder of each Security then outstanding shall have the right
to convert such Security into the kind and amount of shares of stock and other
securities and property (including cash) receivable upon such reclassification,
change, combination, consolidation, merger, sale or conveyance by a holder of
the number of shares of Common Stock deliverable upon conversion of such
Security immediately prior to such reclassification, change, combination,
consolidation, merger, sale or conveyance. 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. If, in the case of any such consolidation,
merger, combination, sale or conveyance, the stock or other securities and
property (including cash) receivable thereupon by a holder of Common Stock
include shares of stock or other securities and property of a person other than
the successor, purchasing or transferee corporation, as the case may be, in such
consolidation, merger, combination, sale or conveyance, then such supplemental
indenture shall also be executed by such other person and shall contain such
additional provisions to protect the interests of the Holders of the Securities
as the Board of Directors shall reasonably consider necessary by reason of the
foregoing. The provisions of this Section 4.11 shall similarly apply to
successive reclassifications, changes, combinations, consolidations, mergers,
sales or conveyances.

                  In the event the Company shall execute a supplemental
indenture pursuant to this Section 4.11, the Company shall promptly file with
the Trustee (x) an Officers' Certificate briefly stating the reasons therefor,
the kind or amount of shares of stock or other securities or property (including
cash) receivable by Holders of the Securities upon the conversion of their
Securities after any such reclassification, change, combination, consolidation,
merger, sale or conveyance, any adjustment to be made with respect thereto and
that all conditions precedent have been complied with and (y) an Opinion of
Counsel that all conditions precedent have been complied with, and shall
promptly mail notice thereof to all Holders.

SECTION 4.12.              Trustee's Disclaimer.

                  The Trustee shall have 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 that fact or the
correctness of any such adjustment, and shall be protected in relying upon, an
Officers' Certificate including the Officers' Certificate with respect thereto
which the Company is obligated to file with the Trustee pursuant to Section 4.9.
The Trustee makes no representation as to the validity or value of any
securities or assets issued upon conversion of Securities, 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 4.11, but may accept as conclusive evidence of the
correctness thereof, and shall be fully protected in relying upon, the Officers'
Certificate with respect thereto which the Company is obligated to file with the
Trustee pursuant to Section 4.11.

SECTION 4.13.              Voluntary Reduction.

                  The Company from time to time may voluntarily reduce the
Conversion Price by any amount for any period of time if the period is at least
20 days and if the reduction is irrevocable during the period if the Board of
Directors determines that such reduction would be in the best interest of the
Company and the Com-
<PAGE>   41
                                      -35-


pany provides 15 days prior notice of any voluntary reduction in the Conversion
Price; provided, however, that in no event may the Company reduce the Conversion
Price to be less than the par value of a share of Common Stock.

                                    ARTICLE 5

                                  SUBORDINATION

SECTION 5.1.               Agreement of Subordination.

                  The Company covenants and agrees, and each Holder of
Securities issued hereunder by its acceptance thereof likewise covenants and
agrees, that all Securities shall be issued subject to the provisions of this
Article 5; and each Person holding any Security, whether upon original issue or
upon transfer, assignment or exchange thereof, accepts and agrees to be bound by
such provisions.

                  The payment of the principal of, premium, if any, and interest
(including Additional Interest, if any) on all Securities (including, but not
limited to, the Redemption Price with respect to the Securities called for
redemption or the Change in Control Purchase Price with respect to the
Securities subject to purchase in accordance with Article 3 as provided in this
Indenture) issued hereunder shall, to the extent and in the manner hereinafter
set forth, be subordinated and subject in right of payment to the prior payment
in full in cash or other payment satisfactory to the holders of Senior
Indebtedness of all Senior Indebtedness, whether outstanding at the date of this
Indenture or thereafter incurred.

                  No provision of this Article 5 shall prevent the occurrence of
any Default or Event of Default hereunder.

SECTION 5.2.               Payments to Holders.

                  No payment shall be made with respect to the principal of, or
premium, if any, or interest (including Additional Interest, if any) on the
Securities (including, but not limited to, the Redemption Price with respect to
the Securities to be called for redemption or the Change in Control Purchase
Price with respect to the Securities subject to purchase in accordance with
Article 3 as provided in this Indenture), except payments and distributions made
by the Trustee as permitted by the first or second paragraph of Section 5.5, if:

                  (i) a default in the payment of principal, premium, interest,
         rent or other obligations due on any Designated Senior Indebtedness
         occurs and is continuing (or, in the case of Designated Senior
         Indebtedness for which there is a period of grace, in the event of such
         a default that continues beyond the period of grace, if any, specified
         in the instrument or lease evidencing such Designated Senior
         Indebtedness), unless and until such default shall have been cured or
         waived or shall have ceased to exist; or

                  (ii) a default, other than a payment default, on a Designated
         Senior Indebtedness occurs and is continuing that then permits holders
         of such Designated Senior Indebtedness to accelerate its maturity and
         the Trustee receives a notice of the default (a "PAYMENT BLOCKAGE
         NOTICE") from a Representative or holder of Designated Senior
         Indebtedness.
<PAGE>   42
                                      -36-


                  Subject to the provisions of Section 5.5, if the Trustee
receives any Payment Blockage Notice pursuant to clause (ii) above, no
subsequent Payment Blockage Notice shall be effective for purposes of this
Section unless and until at least 365 days shall have elapsed since the initial
effectiveness of the immediately prior Payment Blockage Notice. No nonpayment
default that existed or was continuing on the date of delivery of any Payment
Blockage Notice to the Trustee (unless such default was waived, cured or
otherwise ceased to exist and thereafter subsequently reoccurred) shall be, or
be made, the basis for a subsequent Payment Blockage Notice.

                  The Company may and shall resume payments on and distributions
in respect of the Securities upon the earlier of:

                  (a) the date upon which the default is cured or waived or
         ceases to exist, or

                  (b) in the case of a default referred to in clause (ii) above,
         179 days pass after a Payment Blockage Notice is received, unless this
         Article 5 otherwise prohibits the payment or distribution at the time
         of such payment or distribution.

                  Upon any payment by the Company, or distribution of assets of
the Company of any kind or character, whether in cash, property or securities,
to creditors upon any dissolution or winding-up or liquidation or reorganization
of the Company (whether voluntary or involuntary) or in bankruptcy, insolvency,
receivership or similar proceedings, all amounts due or to become due upon all
Senior Indebtedness shall first be paid in full in cash, or other payments
satisfactory to the holders of Senior Indebtedness, before any payment is made
on account of the principal of, premium, if any, or interest (including
Additional Interest, if any) on the Securities (except payments made pursuant to
Article 10 from monies deposited with the Trustee pursuant thereto prior to
commencement of proceedings for such dissolution, winding-up, liquidation or
reorganization); and upon any such dissolution or winding-up or liquidation or
reorganization of the Company or bankruptcy, insolvency, receivership or other
proceeding, any payment by the Company, or distribution of assets of the Company
of any kind or character, whether in cash, property or securities, to which the
Holders of the Securities or the Trustee would be entitled, except for the
provision of this Article 5, shall (except as aforesaid) be paid by the Company
or by any receiver, trustee in bankruptcy, liquidating trustee, agent or other
Person making such payment or distribution, or by the Holders of the Securities
or by the Trustee under this Indenture if received by them or it, directly to
the holders of Senior Indebtedness (pro rata to such holders on the basis of the
respective amounts of Senior Indebtedness held by such holders, or as otherwise
required by law or a court order) or their representative or representatives, or
to the trustee or trustees under any indenture pursuant to which any instruments
evidencing any Senior Indebtedness may have been issued, as their respective
interests may appear, to the extent necessary to pay all Senior Indebtedness in
full in cash, or other payment satisfactory to the holders of Senior
Indebtedness, after giving effect to any concurrent payment or distribution to
or for the holders of Senior Indebtedness, before any payment or distribution is
made to the Holders of the Securities or to the Trustee.

                  For purposes of this Article 5, the words, "cash, property or
securities" shall not be deemed to include shares of stock of the Company as
reorganized or readjusted, or securities of the Company or any other corporation
provided for by a plan of reorganization or readjustment, the payment of which
is subordinated at least to the extent provided in this Article 5 with respect
to the Securities to the payment of all Senior Indebtedness which may at the
time be outstanding; provided that (i) the Senior Indebtedness is assumed by the
new corporation, if any, resulting from any reorganization or readjustment, and
(ii) the rights of the holders of Senior Indebtedness (other than leases which
are not assumed by the Company or the new corporation, as the case may be) are
not, without the consent of such Holders, altered by such reorganization or
readjustment. The consolidation of the Company with, or the merger of the
Company into, another corporation or the liquidation or dissolu-
<PAGE>   43
                                      -37-


tion of the Company following the conveyance or transfer of its property as an
entirety, or substantially as an entirety, to another corporation upon the terms
and conditions provided for in Article 7 shall not be deemed a dissolution,
winding-up, liquidation or reorganization for the purposes of this Section 5.2
if such other corporation shall, as a part of such consolidation, merger,
conveyance or transfer, comply with the conditions stated in Article 7.

                  In the event of the acceleration of the Securities because of
an Event of Default, no payment or distribution shall be made to the Trustee or
any Holder of Securities in respect of the principal of, premium, if any, or
interest (including Additional Interest, if any) on the Securities (including,
but not limited to, the Redemption Price with respect to the Securities called
for redemption or the Change in Control Purchase Price with respect to the
Securities subject to purchase in accordance with Article 3 as provided in this
Indenture), except payments and distributions made by the Trustee as permitted
by the first or second paragraph of Section 5.5, until all Senior Indebtedness
has been paid in full in cash or other payment satisfactory to the holders of
Senior Indebtedness or such acceleration is rescinded in accordance with the
terms of this Indenture.

                  In the event that, notwithstanding the foregoing provisions,
any payment or distribution of assets of the Company of any kind or character,
whether in cash, property or securities (including, without limitation, by way
of setoff or otherwise), prohibited by the foregoing, shall be received by the
Trustee or the Holders of the Securities before all Senior Indebtedness is paid
in full, in cash or other payment satisfactory to the holders of Senior
Indebtedness, or provision is made for such payment thereof in accordance with
its terms in cash or other payment satisfactory to the holders of Senior
Indebtedness, such payment or distribution shall be held in trust for the
benefit of and shall be paid over or delivered to the holders of Senior
Indebtedness or their representative or representatives, or to the trustee or
trustees under any indenture pursuant to which any instruments evidencing any
Senior Indebtedness may have been issued, as their respective interests may
appear, as calculated by the Company, for application to the payment of all
Senior Indebtedness remaining unpaid to the extent necessary to pay all Senior
Indebtedness in full, in cash or other payment satisfactory to the holders of
Senior Indebtedness, after giving effect to any concurrent payment or
distribution to or for the holders of such Senior Indebtedness.

                  Nothing in this Section 5.2 shall apply to claims of, or
payments to, the Trustee under or pursuant to Section 9.7. This Section 5.2
shall be subject to the further provisions of Section 5.5.

SECTION 5.3.               Subrogation of Securities.

                  Subject to the payment in full, in cash or other payment
satisfactory to the holders of Senior Indebtedness, of all Senior Indebtedness,
the rights of the Holders of the Securities shall be subrogated to the extent of
the payments or distributions made to the holders of such Senior Indebtedness
pursuant to the provisions of this Article 5 (equally and ratably with the
holders of all indebtedness of the Company which by its express terms is
subordinated to other indebtedness of the Company to substantially the same
extent as the Securities are subordinated and is entitled to like rights of
subrogation) to the rights of the holders of Senior Indebtedness to receive
payments or distributions of cash, property or securities of the Company
applicable to the Senior Indebtedness until the principal, premium, if any, and
interest (including Additional Interest, if any) on the Securities shall be paid
in full in cash or other payment satisfactory to the holders of Senior
Indebtedness; and, for the purposes of such subrogation, no payments or
distributions to the holders of the Senior Indebtedness of any cash, property or
securities to which the Holders of the Securities or the Trustee would be
entitled except for the provisions of this Article 5, and no payment over
pursuant to the provisions of this Article 5, to or for the benefit of the
holders of Senior Indebtedness by Holders of the Securities or the Trustee,
shall, as between the Company, its creditors other than holders of Senior
Indebtedness, and the Holders of the Securities, be deemed to be
<PAGE>   44
                                      -38-



a payment by the Company to or on account of the Senior Indebtedness; and no
payments or distributions of cash, property or securities to or for the benefit
of the Holders of the Securities pursuant to the subrogation provisions of this
Article 5, which would otherwise have been paid to the holders of Senior
Indebtedness shall be deemed to be a payment by the Company to or for the
account of the Securities. It is understood that the provisions of this Article
5 are and are intended solely for the purposes of defining the relative rights
of the Holders of the Securities, on the one hand, and the holders of the Senior
Indebtedness, on the other hand.

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

                  Upon any payment or distribution of assets of the Company
referred to in this Article 5, the Trustee, subject to the provisions of Section
9.1, and the Holders of the Securities shall be entitled to rely upon any order
or decree made by any court of competent jurisdiction in which such bankruptcy,
dissolution, winding-up, liquidation or reorganization proceedings are pending,
or a certificate of the receiver, trustee in bankruptcy, liquidating trustee,
agent or other person making such payment or distribution, delivered to the
Trustee or to the Holders of the Securities, 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 and all other facts pertinent thereto or to this Article 5.

SECTION 5.4.               Authorization to Effect Subordination.

                  Each Holder of a Security by the Holder's acceptance thereof
authorizes and directs the Trustee on the Holder's behalf to take such action as
may be necessary or appropriate to effectuate the subordination as provided in
this Article 5 and appoints the Trustee to act as the Holder's attorney-in-fact
for any and all such purposes. If the Trustee does not file a proper proof of
claim or proof of debt in the form required in any proceeding referred to in
Section 5.3 hereof at least 30 days before the expiration of the time to file
such claim, the holders of any Senior Indebtedness or their representatives are
hereby authorized to file an appropriate claim for and on behalf of the Holders
of the Securities.

SECTION 5.5.               Notice to Trustee.

                  The Company shall give prompt written notice in the form of an
Officers' Certificate to a Trust Officer of the Trustee and to any Paying Agent
of any fact known to the Company which would prohibit the making of any payment
of monies to or by the Trustee or any Paying Agent in respect of the Securities
pursuant to the provisions of this Article 5. Notwithstanding the provisions of
this Article 5 or any other provision of this Indenture, the Trustee shall not
be charged with knowledge of the existence of any facts which would prohibit the
making of any payment of monies to or by the Trustee in respect of the
Securities pursuant to the provisions of this Article 5, unless and until a
Trust Officer of the Trustee shall have received written notice thereof at the
Corporate Trust Office from the Company (in the form of an Officers'
Certificate) or a Representative or a holder or holders of Senior Indebtedness;
and before the receipt of any such written notice, the Trus-
<PAGE>   45
                                      -39-


tee, subject to the provisions of Section 9.1, shall be entitled in all respects
to assume that no such facts exist; provided that if on a date not fewer than
one Business Day prior to the date upon which by the terms hereof any such
monies may become payable for any purpose (including, without limitation, the
payment of the principal of, or premium, if any, or interest on any Security)
the Trustee shall not have received, with respect to such monies, the notice
provided for in this Section 5.5, then, anything herein contained to the
contrary notwithstanding, the Trustee shall have full power and authority to
receive such monies and to apply the same 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 prior date. Notwithstanding anything in this
Article 5 to the contrary, nothing shall prevent any payment by the Trustee to
the Holders of monies deposited with it pursuant to Article 10, and any such
payment shall not be subject to the provisions of Article 5.

                  The Trustee, subject to the provisions of Section 9.1, shall
be entitled to rely on the delivery to it of a written notice by a
Representative or a person representing himself to be a holder of Senior
Indebtedness to establish that such notice has been given by a Representative or
a holder of Senior Indebtedness. 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 such 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 5.6.               Trustee's Relation to Senior Indebtedness.

                  The Trustee in its individual capacity shall be entitled to
all 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 Section 9.11 or elsewhere in this Indenture shall
deprive the Trustee of any of its rights as such holder.

                  With respect to the holders of Senior Indebtedness, the
Trustee undertakes to perform or to observe only such of its covenants and
obligations as are specifically set forth in this Article 5, and no implied
covenants or obligations with respect to the holders of Senior Indebtedness
shall be read into this Indenture against the Trustee. The Trustee shall not be
deemed to owe any fiduciary duty to the holders of Senior Indebtedness and,
subject to the provisions of Section 9.1, the Trustee shall not be liable to any
holder of Senior Indebtedness if it shall pay over or deliver to Holders of
Securities, the Company or any other person money or assets to which any holder
of Senior Indebtedness shall be entitled by virtue of this Article 5 or
otherwise.

SECTION 5.7.               No Impairment of Subordination.

                  No right of any present or future holder of any Senior
Indebtedness to enforce subordination as herein provided shall at any time in
any way be prejudiced or impaired by any act or failure to act on the part of
the Company or by any act or failure to act, in good faith, by any such holder,
or by any noncompliance by the Company with the terms, provisions and covenants
of this Indenture, regardless of any knowledge thereof which any such holder may
have or otherwise be charged with.
<PAGE>   46
                                      -40-

SECTION 5.8.               Certain Conversions Deemed Payment.

                  For the purposes of this Article 5 only, (1) the issuance and
delivery of junior securities upon conversion of Securities in accordance with
Article 4 shall not be deemed to constitute a payment or distribution on account
of the principal of (or premium, if any) or interest on Securities or on account
of the purchase or other acquisition of Securities, and (2) the payment,
issuance or delivery of cash (except in satisfaction of fractional shares
pursuant to Section 4.3), property or securities (other than junior securities)
upon conversion of a Security shall be deemed to constitute payment on account
of the principal of such Security. For the purposes of this Section 5.8, the
term "junior securities" means (a) shares of any stock of any class of the
Company, or (b) securities of the Company which are subordinated in right of
payment to all Senior Indebtedness which may be outstanding at the time of
issuance or delivery of such securities to substantially the same extent as, or
to a greater extent than, the Securities are so subordinated as provided in this
Article. Nothing contained in this Article 5 or elsewhere in this Indenture or
in the Securities is intended to or shall impair, as among the Company, its
creditors other than holders of Senior Indebtedness and the Holders, the right,
which is absolute and unconditional, of the Holder of any Security to convert
such Security in accordance with Article 4.

SECTION 5.9.               Article Applicable to Paying Agents.

                  If at any time any Paying Agent other than the Trustee shall
have been appointed by the Company and be then acting hereunder, the term
"Trustee" as used in this Article shall (unless the context otherwise requires)
be construed as extending to and including such Paying Agent within its meaning
as fully for all intents and purposes as if such Paying Agent were named in this
Article in addition to or in place of the Trustee; provided, however, that the
first paragraph of Section 5.5 shall not apply to the Company or any Affiliate
of the Company if it or such Affiliate acts as Paying Agent.

SECTION 5.10.              Senior Indebtedness Entitled to Rely.

                  The holders of Senior Indebtedness (including, without
limitation, Designated Senior Indebtedness) shall have the right to rely upon
this Article 5, and no amendment or modification of the provisions contained
herein shall diminish the rights of any such holder except in accordance with
the last paragraph of Section 11.2.


                                    ARTICLE 6

                                    COVENANTS


SECTION 6.1.               Payment of Securities.

                  The Company shall promptly make all payments in respect of the
Securities on the dates and in the manner provided in the Securities and this
Indenture. An installment of principal or interest or Additional Interest, if
any, shall be considered paid on the date it is due if the Paying Agent (other
than the Company) holds by 11:00 a.m., New York City time, on that date money,
deposited by the Company or an Affiliate thereof, sufficient to pay the
installment. The Company shall, to the fullest extent permitted by law, pay
interest on overdue principal (including premium, if any) and overdue
installments of interest at the rate borne by the Securities per annum. The
conversion of any Securities pursuant to Article 4 hereof and payment of the
Make-Whole Payment by delivery of shares of Common Stock in accordance with
Article 3, together with the making of any cash
<PAGE>   47
                                      -41-

payments required to be made in accordance with the terms of the Securities and
this Indenture, shall satisfy the Company's obligations under this Section 6.1
with respect to such Securities.

                  Payment of the principal of (and premium, if any) and any
interest on the Securities shall be made at the office or agency of the Company
maintained for that purpose in the Borough of Manhattan, The City of New York
(which shall initially be State Street Bank and Trust Company, N.A. having an
office at 61 Broadway, New York, New York 10006) or at the Corporate Trust
Office of the Trustee in such coin or currency of the United States of America
as at the time of payment is legal tender for payment of public and private
debts; provided, however, that at the option of the Company payment of interest
may be made by check mailed to the address of the Person entitled thereto as
such address appears in the Register; provided further that a Holder with an
aggregate principal amount in excess of $2,000,000 will be paid by wire transfer
in immediately available funds at the election of such Holder.

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 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.

                  Delivery of such reports, information and documents to the
Trustee is for informational purposes only and the Trustee's receipt of such
shall not constitute constructive notice of any information contained therein or
determinable from information contained therein, including the Company's
compliance with any of its covenants hereunder (as to which the Trustee is
entitled to rely exclusively on Officers' Certificates).

SECTION 6.3.               Compliance Certificates.

                  The Company shall deliver to the Trustee, within 90 days after
the end of each fiscal year of the Company (beginning with the fiscal year
ending September 30, 2001), an Officers' Certificate as to the signers'
knowledge of the Company's compliance with all conditions and covenants on its
part contained in this Indenture and stating whether or not the signers know of
any Default or Event of Default. If such signers know of such a Default or Event
of Default, the Officers' Certificate shall describe the Default or Event of
Default and the efforts to remedy the same. For the purposes of this Section
6.3, compliance shall be determined without regard to any grace period or
requirement of notice provided pursuant to the terms of this Indenture.

SECTION 6.4.               Further Instruments and Acts.

                  Upon request of the Trustee, the Company will execute and
deliver such further instruments and do such further acts as may be reasonably
necessary or proper to carry out more effectively the purposes of this
Indenture.

SECTION 6.5.               Maintenance of Corporate Existence.

                  Subject to 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.
<PAGE>   48
                                      -42-

SECTION 6.6.               Rule 144A Information Requirement.

                  Within the period prior to the expiration of the holding
period applicable to sales thereof under Rule 144(k) under the Securities Act
(or any successor provision), the Company covenants and agrees that it shall,
during any period in which it is not subject to Section 13 or 15(d) under the
Exchange Act, make available to any Holder or beneficial holder of Securities or
any Common Stock issued upon conversion thereof which continue to be Restricted
Securities in connection with any sale thereof and any prospective purchaser of
Securities or such Common Stock designated by such Holder or beneficial holder,
the information required pursuant to Rule 144A(d)(4) under the Securities Act
upon the request of any Holder or beneficial holder of the Securities or such
Common Stock and it will take such further action as any Holder or beneficial
holder of such Securities or such Common Stock may reasonably request, all to
the extent required from time to time to enable such Holder or beneficial holder
to sell its Securities or Common Stock without registration under the Securities
Act within the limitation of the exemption provided by Rule 144A, as such Rule
may be amended from time to time. Upon the written request of any Holder or any
beneficial holder of the Securities or such Common Stock, the Company will
deliver to such Holder a written statement as to whether it has complied with
such requirements.

SECTION 6.7.               Stay, Extension and Usury Laws.

                  The Company covenants (to the extent that it may lawfully do
so) that it shall not at any time insist upon, plead, or in any manner
whatsoever claim or take the benefit or advantage of, any stay, extension or
usury law or other law which would prohibit or forgive the Company from paying
all or any portion of the principal of, premium, if any, or interest (including
Additional Interest, if any) on the Securities as contemplated herein, wherever
enacted, now or at any time hereafter in force, or which may affect the
covenants or the performance of this Indenture, and the Company (to the extent
it may lawfully do so) hereby expressly waives all benefit or advantage of any
such law, and covenants that it will not, by resort to any such law, hinder,
delay or impede the execution of any power herein granted to the Trustee, but
will suffer and permit the execution of every such power as though no such law
had been enacted.

SECTION 6.8.               Payment of Additional Interest.

                  If Additional Interest is payable by the Company pursuant to
the Registration Rights Agreement, the Company shall deliver to the Trustee a
certificate to that effect stating (i) the amount of such Additional Interest
that is payable and (ii) the date on which such Additional Interest is payable.
Unless and until a Trust Officer of the Trustee receives such a certificate, the
Trustee may assume without inquiry that no such Additional Interest is payable.
If the Company has paid Additional Interest directly to the Persons entitled to
it, the Company shall deliver to the Trustee a certificate setting forth the
particulars of such payment.


                                    ARTICLE 7

              CONSOLIDATION, MERGER, CONVEYANCE, TRANSFER OR LEASE


SECTION 7.1.               Company May Consolidate, Etc., Only on Certain Terms.

                  The Company shall not consolidate with or merge into any other
Person (in a transaction in which the Company is not the surviving corporation)
or convey, transfer or lease its properties and assets substantially as an
entirety to any Person, unless:
<PAGE>   49
                                      -43-

                  (1) in case the Company shall consolidate with or merge into
         another Person (in a transaction in which the Company is not the
         surviving corporation) or convey, transfer or lease its properties and
         assets substantially as an entirety to any Person, the Person formed by
         such consolidation or into which the Company is merged or the Person
         which acquires by conveyance or transfer, or which leases, the
         properties and assets of the Company substantially as an entirety shall
         be a corporation or limited liability company organized and validly
         existing under the laws of the United States of America, any State
         thereof or the District of Columbia and shall expressly assume, by an
         indenture supplemental hereto, executed and delivered to the Trustee,
         in form satisfactory to the Trustee, the due and punctual payment of
         the principal of and any premium and interest on all the Securities and
         the performance or observance of every covenant of this Indenture on
         the part of the Company to be performed or observed and the conversion
         rights shall be provided for in accordance with Article 4, by
         supplemental indenture satisfactory in form to the Trustee, executed
         and delivered to the Trustee, by the Person (if other than the Company)
         formed by such consolidation or into which the Company shall have been
         merged or by the Person which shall have acquired the Company's assets;

                  (2) immediately after giving effect to such transaction, no
         Default or Event of Default shall have happened and be continuing; and

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

SECTION 7.2.               Successor Substituted.

                  Upon any consolidation of the Company with, or merger of the
Company into, any other Person or any conveyance, transfer or lease of the
properties and assets of the Company substantially as an entirety in accordance
with Section 7.1, the successor Person formed by such consolidation or into
which the Company is merged or to which such conveyance, transfer or lease is
made shall succeed to, and be substituted for, and may exercise every right and
power of, the Company under this Indenture with the same effect as if such
successor Person had been named as the Company herein, and thereafter, except in
the case of a lease, the predecessor Person shall be relieved of all obligations
and covenants under this Indenture and the Securities.


                                    ARTICLE 8

                              DEFAULT AND REMEDIES


SECTION 8.1.               Events of Default.

                  An "Event of Default" shall occur if:

                  (1) the Company defaults in the payment of any interest or
         Additional Interest, if any, payable to all holders of Securities (as
         defined in the Registration Rights Agreement) on any Security when the
         same becomes due and payable and the default continues for a period of
         30 days, whether or not such payment shall be prohibited by the
         provisions of Article 5 hereof;
<PAGE>   50
                                      -44-

                  (2) the Company defaults in the payment of any principal of
         (including, without limitation, any premium or Make-Whole Payment, if
         any, on) any Security when the same becomes due and payable (whether at
         maturity, upon redemption, on a Change in Control Purchase Date or
         otherwise), whether or not such payment shall be prohibited by the
         provisions of Article 5 hereof;

                  (3) the Company fails to comply with any of its other
         agreements contained in the Securities or this Indenture and the
         default continues for the period and after the notice specified below;

                  (4) the Company fails to give notice to the Trustee and each
         Holder of a Change in Control in accordance with Section 3.8(b);

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

                           (i) commences a voluntary case or proceeding;

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

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

                           (iv) 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:

                           (i) is for relief against the Company in an
                  involuntary case or proceeding;

                           (ii) appoints a Custodian of the Company or for all
                  or substantially all of the property of the Company; or

                           (iii) orders the liquidation of the Company;

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

                  The term "Bankruptcy Law" means Title 11 of the United States
Code (or any successor thereto) 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) above is not an Event of Default
until the Trustee notifies the Company, or the Holders of at least 25% in
aggregate principal amount of the Securities then outstanding notify the Company
and the Trustee, of the Default, and the Company does not cure the Default
within 60 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 any Default under this Section 8.1 is
cured, it ceases.
<PAGE>   51
                                      -45-

                  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, a Paying
Agent, any Holder or any agent of any Holder.

SECTION 8.2.               Acceleration.

                  If an Event of Default (other than an Event of Default
specified in clause (5) or (6) of Section 8.1) occurs and is continuing, the
Trustee may, by notice to the Company, or the Holders of at least 25% in
aggregate principal amount of the Securities then outstanding may, by notice to
the Company and the Trustee, declare all unpaid principal on the Securities then
outstanding (if not then due and payable) to be due and payable upon any such
declaration, and the same shall become and be immediately due and payable. If an
Event of Default specified in clause (5) or (6) of Section 8.1 occurs, all
unpaid principal of the Securities then outstanding shall ipso facto become and
be immediately due and payable without any declaration or other act on the part
of the Trustee or any Holder. The Holders of a majority in aggregate principal
amount of the Securities then outstanding by notice to the Trustee may rescind
an acceleration and its consequences if (a) all existing Events of Default,
other than the nonpayment of the principal of the Securities which has become
due solely by such declaration of acceleration, have been cured or waived; (b)
to the extent the payment of such interest is lawful, interest (calculated at
the rate per annum borne by the Securities) on overdue installments of interest
and overdue principal, which has become due otherwise than by such declaration
of acceleration, has been paid; (c) the rescission would not conflict with any
judgment or decree of a court of competent jurisdiction; and (d) all payments
due to the Trustee and any predecessor Trustee under Section 9.7 have been made.
No such rescission shall affect any subsequent Default or impair any right
consequent thereto.

SECTION 8.3.               Other Remedies.

                  If an Event of Default occurs and is continuing, the Trustee
may, but shall not be obligated to, pursue any available remedy by proceeding at
law or in equity to collect the payment of the principal of or interest on the
Securities or to enforce the performance of any provision of the Securities or
this Indenture.

                  The Trustee may maintain a proceeding even if it does not
possess any of the Securities or does not produce any of them in the proceeding.
A delay or omission by the Trustee or any Securityholder 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 Securities then outstanding by notice to the Trustee may
waive an existing Default or Event of Default and its consequence, except a
Default or Event of Default (i) in the payment of the principal of or interest,
if any, including the Redemption Price and any Make-Whole Payment upon
redemption pursuant to Section 3.1, on any Security, (ii) in respect of a
failure by the Company to convert any Securities into Common Stock, (iii) in
respect of any covenant or provision hereof for the personal protection or
benefit of the Trustee without its consent or (iv) any Default or Event of
Default in respect of any provision of this Indenture or the Securities which,
under Section 11.2, cannot be modified or amended without the consent of the
Holder of each Security affected. When a Default or Event of Default is waived,
it is cured and ceases.
<PAGE>   52
                                      -46-

SECTION 8.5.               Control by Majority.

                  The Holders of a majority in principal amount of the
Securities then outstanding may direct the time, method and place of conducting
any proceeding for any remedy available to the Trustee or exercising any trust
or power conferred on 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 Holder or the Trustee, or
that may involve the Trustee in personal liability unless the Trustee is offered
indemnity satisfactory to it; provided, however, that the Trustee may take any
other action deemed proper by the Trustee which is not inconsistent with such
direction.

SECTION 8.6.               Limitations on Suits.

                  No Holder has any right to institute any proceeding under this
Indenture, or for the appointment of a receiver or a trustee, or for any other
remedy with respect to this Indenture or the Securities (except actions for
payment of overdue principal or interest or for the conversion of the Securities
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 25% in principal amount of the
         then outstanding Securities make a written request to the Trustee to
         institute such proceeding as trustee;

                  (3) such Holder or Holders offer reasonable indemnity 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 Securities then outstanding.

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

SECTION 8.7.               Rights of Holders to Receive Payment and to Convert.

                  Notwithstanding any other provision of this Indenture, the
right of any Holder of a Security to receive payment of the principal of and
interest, if any, including the Redemption Price and any Make-Whole Payment upon
redemption pursuant to Section 3.1, on the Security, on or after the respective
due dates therefor, to convert such Security in accordance with Article 4 and to
bring suit for the enforcement of any such payment on or after such respective
dates or the right to convert, 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 clause (1) or (2) of Section 8.1 occurs and is continuing, the
Trustee may recover judgment in its own name and as trustee of an
<PAGE>   53
                                      -47-

express trust against the Company or another obligor on the Securities for the
whole amount of principal and accrued interest remaining unpaid, together with,
to the extent that payment of such interest is lawful, interest on overdue
principal and on overdue installments of interest, in each case at the rate per
annum borne by the Securities and such 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
Holders allowed in any judicial proceedings relative to the Company (or any
other obligor on the Securities), its creditors or its property and shall be
entitled and empowered to collect and receive any money or other property
payable or deliverable on any such claims and to distribute the same and to take
any other action with respect to such claims, including participation as a
member of any official committee of creditors appointed in the matters as it
deems necessary or advisable, and any Custodian in any such judicial proceeding
is hereby authorized by each Holder to make such payments to the Trustee and, in
the event that the Trustee shall consent to the making of such payments directly
to the Holders, 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 of 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, money, securities and other property which the Holders
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, on
behalf of any Holder, to authorize, accept or adopt any plan of reorganization,
arrangement, adjustment or composition affecting the Securities or the rights of
any Holder thereof, or to authorize the Trustee to vote in respect of the claim
of any Holder 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 Holders for amounts due and unpaid on the Securities
for principal and interest, ratably, without preference or priority of any kind,
according to the amounts due and payable on the Securities for principal and
interest, respectively; and

                  Fourth, to the Company.

                  The Trustee may fix a record date and payment date for any
payment to Holders pursuant to this Section 8.10.
<PAGE>   54
                                      -48-

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 and expenses, against any party litigant in the suit,
having due regard to the merits and good faith of the claims or defenses 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 Securities then outstanding.


                                    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 its exercise as a prudent
person would exercise or use under the circumstances in the conduct of his or
her 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 any certificates
         and opinions which by any provision hereof are specifically required to
         be delivered to the Trustee 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 subsection (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) No provision of this Indenture shall require the Trustee
to expend or risk its own funds or otherwise incur any financial liability in
the performance of any of its duties hereunder or in the exer-
<PAGE>   55
                                      -49-

cise of any of its rights or powers unless the Trustee shall have received
adequate indemnity in its opinion against potential costs and liabilities
incurred by it relating thereto.

                  (e) Every provision of this Indenture that in any way relates
to the Trustee is subject to subsections (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.

                  Subject to Section 9.1:

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

                  (f) The Trustee shall be under no obligation to exercise any
         of the rights or powers vested in it by this Indenture at the request
         or direction of any of the Holders pursuant to this Indenture, unless
         such Holders shall have offered to the Trustee security or indemnity
         satisfactory to the Trustee against the costs, expenses and liabilities
         which might be incurred by it in compliance with such request or
         direction.

                  (g) The Trustee shall not be bound to make any investigation
         into the facts or matters stated in any resolution, certificate,
         statement, instrument, opinion, report, notice, request, direction,
         consent, order, bond, debenture, note, other evidence of indebtedness
         or other paper or document, but the Trustee, in its discretion, may
         make such further inquiry or investigation into such further inquiry or
         investigation into such facts or matters as it may see fit, and, if the
         Trustee shall determine to make such further inquiry or investigation,
         it shall be entitled to examine the books, records and premises of the
         Company, personally or by agent or attorney at the sole cost of the
         Company and shall incur no liability or additional liability of any
         kind by reason of such inquiry or investigation.
<PAGE>   56
                                      -50-

                  (h) The Trustee shall not be deemed to have notice of any
         Default or Event of Default unless a Trust Officer of the Trustee has
         actual knowledge thereof or unless written notice of any event which is
         in fact such a Default is received by the Trustee at the Corporate
         Trust Office, and such notice references the Securities and this
         Indenture.

                  (i) The rights, privileges, protections, immunities and
         benefits given to the Trustee, including, without limitation, its right
         to be indemnified, are extended to, and shall be enforceable by, the
         Trustee in each of its capacities hereunder, and to each agent,
         custodian and other Person employed to act hereunder.

SECTION 9.3.               Individual Rights of Trustee.

                  The Trustee in its individual or any other capacity may become
the owner or pledgee of Securities 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 Securities, it shall not be accountable for
the Company's use of the proceeds from the Securities, and it shall not be
responsible for any statement in the Securities 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 a Trust Officer of the Trustee, the Trustee shall mail to
each Securityholder notice of the Default or Event of Default within 90 days
after it occurs. However, the Trustee may withhold the notice if and so long as
a committee of its Trust Officers in good faith determines that withholding
notice is in the interests of Securityholders, except in the case of a Default
or an Event of Default in payment of the principal of or interest on any
Security.

SECTION 9.6.               Reports by Trustee to Holders.

                  If such report is required by TIA Section 313, within 60 days
after each June 1, beginning with June 1, 2002, the Trustee shall mail to each
Securityholder a brief report dated as of such June 1that complies with TIA
Section 313(a). The Trustee also shall comply with TIA Section 313(b)(2) and
(c).

                  A copy of each report at the time of its mailing to
Securityholders shall be mailed to the Company and filed with the SEC and each
stock exchange, if any, on which the Securities are listed or quoted. The
Company shall notify the Trustee whenever the Securities become listed on any
stock exchange or listed or admitted to trading on any quotation system and any
changes in the stock exchanges or quotation systems on which the Securities are
listed or admitted to trading and of any delisting thereof.

SECTION 9.7.               Compensation and Indemnity.

                  The Company shall pay to the Trustee from time to time such
compensation (as agreed to from time to time by the Company and the Trustee in
writing) 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
<PAGE>   57
                                      -51-

reimburse the Trustee upon request for all reasonable, actual disbursements,
expenses and advances incurred or made by it. Such expenses may include the
reasonable, actual compensation, disbursements and expenses of the Trustee's
agents and counsel. All rights, protections and benefits of the Trustee shall
extend to the Trustee acting as Conversion Agent, Paying Agent, Registrar,
Primary Registrar or other Agent with respect hereto.

                  The Company shall indemnify the Trustee or any predecessor
Trustee (which for purposes of this Section 9.7 shall include its officers,
directors, employees and agents) for, and hold it harmless against, any and all
loss, liability or expense including taxes (other than taxes based upon,
measured by or determined by the income of the Trustee), (including reasonable
legal fees and expenses) incurred by it in connection with the acceptance or
administration of 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 including the reasonable costs and expenses of the Trustee
and its counsel in defending itself against any claim or liability in connection
with the exercise or performance of any of its powers or duties hereunder. The
Trustee shall notify the Company promptly of any claim asserted against the
Trustee for which it may seek indemnity. The Company need not pay for any
settlement without its written consent, which shall not be unreasonably
withheld.

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

                  To secure the Company's payment obligations in this Section
9.7, the Trustee shall have a senior claim to which the Securities 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 the Securities. The obligations of the Company under this Section 9.7 shall
survive the satisfaction and discharge of this Indenture or the resignation or
removal of the Trustee.

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

SECTION 9.8.               Replacement of Trustee.

                  The Trustee may resign by so notifying the Company. The
Holders of a majority in principal amount of the Securities then outstanding may
remove the Trustee by so notifying the Trustee and may, with the Company's
written consent, appoint a successor Trustee. 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. The resignation or removal of a Trustee shall not be
effective until a successor Trustee shall have delivered the written acceptance
of its appointment as described below.
<PAGE>   58
                                      -52-

                  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 Securities then
outstanding may petition any court of competent jurisdiction for the appointment
of a successor Trustee at the expense of the Company.

                  If the Trustee fails to comply with Section 9.10, any Holder
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 that the retiring 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 mail
notice of its succession to each Holder.

                  A retiring Trustee shall not be liable for the acts or
omissions of any successor Trustee after its succession.

                  Notwithstanding replacement of the Trustee pursuant to this
Section 9.8, the Company's obligations under Section 9.7 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 (including the
administration of this Indenture) 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. Such successor Trustee shall promptly mail notice
of its succession to the Company and each Holder.

SECTION 9.10.              Eligibility; Disqualification.

                  The Trustee shall always satisfy the requirements of
paragraphs (1), (2) and (5) of TIA Section 310(a). The Trustee (or its parent
holding company) shall have a combined capital and surplus of at least
$50,000,000. If at any time the Trustee shall cease to satisfy any such
requirements, it shall resign immediately in the manner and with the effect
specified in this Article 9. The Trustee shall be subject to the provisions of
TIA Section 310(b). Nothing herein shall prevent the Trustee from filing with
the SEC the application referred to in the penultimate paragraph of TIA Section
310(b).

SECTION 9.11.              Preferential Collection of Claims Against Company.

                  The Trustee shall comply with TIA Section 311(a), excluding
any creditor relationship listed in TIA Section 311(b). A Trustee who has
resigned or been removed shall be subject to TIA Section 311(a) to the extent
indicated therein.
<PAGE>   59
                                      -53-

                                   ARTICLE 10

                     SATISFACTION AND DISCHARGE OF INDENTURE


SECTION 10.1.              Satisfaction and Discharge of Indenture.

                  This Indenture shall cease to be of further effect (except as
to any surviving rights of conversion, registration of transfer or exchange of
Securities herein expressly provided for and except as further provided below),
and the Trustee, on demand of and at the expense of the Company, shall execute
proper instruments acknowledging satisfaction and discharge of this Indenture,
when

                  (1)      either

                            (i) all Securities theretofore authenticated and
                  delivered (other than (x) Securities which have been
                  destroyed, lost or stolen and which have been replaced or paid
                  as provided in Section 2.7 and (y) Securities for whose
                  payment money has theretofore been deposited in trust and
                  thereafter repaid to the Company as provided in Section 10.3)
                  have been delivered to the Trustee for cancellation; or

                           (ii) all such Securities not theretofore delivered to
                  the Trustee for cancellation (x) have become due and payable,
                  (y) will become due and payable at the Final Maturity Date
                  within ninety days, or (z) have been called for redemption
                  within ninety days under arrangements satisfactory to the
                  Trustee for the giving of notice of redemption by the Trustee
                  in the name, and at the expense, of the Company,

and the Company, in the case of clause (i) or (ii) above, has irrevocably
deposited or caused to be irrevocably deposited with the Trustee or a Paying
Agent (other than the Company or any of its Affiliates) as trust funds in trust
for the purpose cash in an amount sufficient to pay and discharge the entire
indebtedness on such Securities not theretofore delivered to the Trustee for
cancellation, for principal and interest to the date of such deposit (in the
case of Securities which have become due and payable) or to the Final Maturity
Date or Redemption Date, as the case may be;

                  (2) the Company has paid or caused to be paid all other sums
         payable hereunder by the Company; and

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

                  Notwithstanding the satisfaction and discharge of this
Indenture, the obligations of the Company to the Trustee under Section 9.7 shall
survive and, if money shall have been deposited with the Trustee pursuant to
subclause (y) of clause (1)(i) of this Section, the provisions of Sections 2.3,
2.4, 2.5, 2.6, 2.7, 2.12, 3.8, 3.9, 3.10, 3.11, 3.12, 3.13 and 12.5, Article 4,
the last paragraph of Section 6.2 and this Article 10, shall survive until the
Securities have been paid in full.
<PAGE>   60
                                      -54-

SECTION 10.2.              Application of Trust Money.

                  Subject to the provisions of Section 10.3, the Trustee or a
Paying Agent shall hold in trust, for the benefit of the Holders, all money
deposited with it pursuant to Section 10.1 and shall apply the deposited money
in accordance with this Indenture and the Securities to the payment of the
principal of and interest on the Securities. Money so held in trust shall not be
subject to the subordination provisions of Article 5.

SECTION 10.3.              Repayment to Company.

                  The Trustee and each Paying Agent shall promptly pay to the
Company upon request any excess money (i) deposited with them pursuant to
Section 10.1 and (ii) held by them at any time.

                  The Trustee and each 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 mailed
to each Holder entitled to such money notice that (x) such money remains
unclaimed and (y) after a date specified therein, which shall be at least 30
days from the date of such mailing, any unclaimed balance of such money then
remaining will be repaid to the Company. After payment to the Company, Holders
entitled to money must look to the Company for payment as general creditors.

SECTION 10.4.              Reinstatement.

                  If the Trustee or any Paying Agent is unable to apply any
money in accordance with Section 10.2 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, then the
Company's obligations under this Indenture and the Securities shall be revived
and reinstated as though no deposit had occurred pursuant to Section 10.1 until
such time as the Trustee or such Paying Agent is permitted to apply all such
money in accordance with Section 10.2; provided, however, that if the Company
has made any payment of the principal of or interest on any Securities because
of the reinstatement of its obligations, the Company shall be subrogated to the
rights of the Holders of such Securities to receive any such payment from the
money held by the Trustee or such Paying Agent.


                                   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 Securities without notice to or consent of any Securityholder:

                  (a)      to comply with Sections 4.11 and 7.1;

                  (b) to provide for uncertificated Securities in addition to or
         in place of certificated Securities (provided that the uncertificated
         Securities are issued in registered form for purposes of Section
<PAGE>   61
                                      -55-

         163(f) of the Code, or in a manner such that the uncertificated
         Securities are described in Section 163(f)(2)(B) of the Code);

                  (c) to comply with the provisions of the TIA;

                  (d) to appoint a successor Trustee;

                  (e) to cure any ambiguity, defect or inconsistency; or

                  (f) to make any other change that does not adversely affect
         the rights of any Securityholder.

SECTION 11.2.              With Consent of Holders.

                  The Company and the Trustee may amend or supplement this
Indenture or the Securities with the written consent of the Holders of at least
a majority in aggregate principal amount of the Securities then outstanding. The
Holders of at least a majority in aggregate principal amount of the Securities
then outstanding may waive compliance in a particular instance by the Company
with any provision of this Indenture or the Securities without notice to any
Securityholder. However, notwithstanding the foregoing but subject to Section
11.4, without the written consent of each Securityholder affected, an amendment,
supplement or waiver, including a waiver pursuant to Section 8.4, may not:

                  (a) change the stated maturity of the principal of, or
         interest on, any Security;

                  (b) reduce the principal amount of, or any premium or interest
         on, any Security;

                  (c) reduce the amount of principal payable upon acceleration
         of the maturity of any Security;

                  (d) change the place or currency of payment of principal of,
         or any premium or interest on, any Security;

                  (e) impair the right to institute suit for the enforcement of
         any payment on, or with respect to, any Security;

                  (f) modify the subordination provisions of Article 5 in a
         manner materially adverse to the Holders of Securities;

                  (g) adversely affect the right of Holders to convert
         Securities other than as provided in or under Article 4 of this
         Indenture;

                  (h) reduce the percentage of the aggregate principal amount of
         the outstanding Securities whose Holders must consent to a modification
         or amendment of this Indenture; and

                  (i) modify any of the provisions of this Section or Section
         8.4, except to increase any such percentage or to provide that
         specified additional provisions of this Indenture cannot be modified or
         waived without the consent of the Holder of each outstanding Security
         affected thereby.
<PAGE>   62
                                      -56-

                  It shall not be necessary for the consent of the Holders under
this Section 11.2 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
11.2 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 or supplement under this Section 11.2 or under Section 11.1
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
Securities 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 Security or portion of a Security that evidences the same
debt as the consenting Holder's Security, even if notation of the consent is not
made on any Security. However, any such Holder or subsequent Holder may revoke
the consent as to its Security or portion of a Security 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 Securityholder, unless it makes a change described in any of
clauses (a) through (i) of Section 11.2. In that case the amendment, supplement
or waiver shall bind each Holder of a Security who has consented to it and every
subsequent Holder of a Security or portion of a Security that evidences the same
debt as the consenting Holder's Security.

SECTION 11.5.              Notation on or Exchange of Securities.

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

SECTION 11.6.              Trustee to Sign Amendments, Etc.

                  The Trustee shall sign any amendment or supplemental indenture
authorized pursuant to this Article 11 if the amendment or supplemental
indenture does not adversely affect the rights, duties, liabilities or
immunities of the Trustee. If it does, the Trustee may, in its sole discretion,
but need not sign it. In signing or refusing to sign such amendment or
supplemental indenture, 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 supplemental indenture is authorized or permitted
by this Indenture. The Company may not sign an amendment
<PAGE>   63
                                      -57-

or supplemental indenture until the Board of Directors approves it, which
approval shall be confirmed by an Officers' Certificate of the Company to such
effect.


                                   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, request or communication shall be given in writing
and delivered in person or mailed by first-class mail, postage prepaid,
addressed as follows:

                  If to the Company:

                  Brooks Automation, Inc.
                  15 Elizabeth Drive
                  Chelmsford, Massachusetts 01824
                  Attention: Treasurer
                  Facsimile:  (978) 262-2502

                  with a copy to:

                  Brown, Rudnick, Freed & Gesmer
                  One Financial Center
                  Boston, Massachusetts 02111
                  Attention:  Samuel P. Williams, Esq.
                  Facsimile:  (617) 856-8201

                  If to the Trustee:

                  State Street Bank and Trust Company
                  2 Avenue de Lafayette, 6th Floor
                  Boston, Massachusetts 02111
                  Attention: Global Investor Services Group Corporate Trust
                  Facsimile:  (617) 662-1463

                  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.
<PAGE>   64
                                      -58-

                  Any notice or communication mailed to a Securityholder shall
be mailed by first-class mail to it at its address shown on the register kept by
the Primary Registrar.

                  Failure to mail a notice or communication to a Securityholder
or any defect in it shall not affect its sufficiency with respect to other
Securityholders. If a notice or communication to a Securityholder 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.

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

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 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 or she
         has made such examination or investigation as is necessary to enable
         him or her 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 Securityholders.

                  The Company (or, in the event deposits have been made pursuant
to Section 10.1, the Trustee) may set a record date for purposes of determining
the identity of Holders entitled to vote or consent to any action by vote or
consent authorized or permitted under this Indenture, which record date shall
not be more than thirty
<PAGE>   65
                                      -59-

(30) days prior to the date of the commencement of solicitation of such action.
Notwithstanding the provisions of Section 11.4, if a record date is fixed, those
persons who were Holders of Securities at the close of business on 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.

SECTION 12.6.              Rules by Trustee, Paying Agent, Registrar and
                           Conversion Agent.

                  The Trustee may make reasonable rules (not inconsistent with
the terms of this Indenture) for action by or at a meeting of Holders. Any
Registrar, Paying Agent or Conversion Agent may make reasonable rules for its
functions.

SECTION 12.7.              Legal Holidays.

                  A "Legal Holiday" is a Saturday, Sunday or a day on which
state or federally chartered banking institutions in New York, New York and the
state in which the Corporate Trust Office is located are not required to be
open. If a payment date is a Legal Holiday, payment shall be made on the next
succeeding day that is not a Legal Holiday, and no interest shall accrue for the
intervening period. If a regular record date is a Legal Holiday, the record
shall not be affected.

SECTION 12.8.              Governing Law.

                  This Indenture and the Securities shall be governed by, and
construed in accordance with, the laws of the State of New York, without regard
to principles of conflicts of laws.

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 of the Company. 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 18 of the Securities of
any director, officer, employee or shareholder, as such, of the Company is
waived and released.

SECTION 12.11.             Successors.

                  All agreements of the Company in this Indenture and the
Securities 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.
<PAGE>   66
                                      -60-

SECTION 12.13.             Separability.

                  In case any provisions in this Indenture or in the Securities
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.

                  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.

SECTION 12.15.             Improper Payments.

                  Each Holder, by acceptance of its Security, agrees with the
Company and with each other Holder that in the event that notwithstanding the
provisions of this Indenture, it receives any payment or distribution in respect
of its Security contrary to the provisions of this Indenture, such payment or
distribution shall be received and held in trust for the benefit of, and shall
upon demand of the Company or the Trustee be forthwith paid over and delivered
to, the Trustee, which shall pay and deliver such amount to the Persons then
entitled thereto in accordance with this Indenture.


                             SIGNATURE PAGE FOLLOWS
<PAGE>   67
                                       S-1

                  IN WITNESS WHEREOF, the parties hereto have hereunto set their
hands as of the date and year first above written.

                                            BROOKS AUTOMATION, INC.


                                            By: /s/ Ellen B. Richstone
                                                -------------------------
                                            Name:   Ellen B. Richstone
                                            Title:  Senior Vice President,
                                                    Finance and
                                                    Administration and
                                                    Chief Financial Officer


                                            STATE STREET BANK AND TRUST COMPANY,
                                            as Trustee


                                            By:  /s/ Chi C. Ma
                                                 --------------------
                                            Name:    Chi C. Ma
                                            Title:  Vice President
<PAGE>   68
                                    EXHIBIT A
                           [FORM OF FACE OF SECURITY]


                  [UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED
REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY TO THE COMPANY 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 THE DEPOSITORY TRUST COMPANY (AND ANY PAYMENT
HEREON IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN
AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY), ANY TRANSFER, PLEDGE
OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL SINCE
THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN. THIS SECURITY
IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE HEREINAFTER REFERRED TO
AND IS REGISTERED IN THE NAME OF A DEPOSITARY OR A NOMINEE THEREOF. THIS
SECURITY IS EXCHANGEABLE FOR SECURITIES REGISTERED IN THE NAME OF A PERSON OTHER
THAN THE DEPOSITARY OR ITS NOMINEE ONLY IN THE LIMITED CIRCUMSTANCES DESCRIBED
IN THE INDENTURE AND, UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR
SECURITIES IN DEFINITIVE FORM, THIS SECURITY MAY NOT BE TRANSFERRED EXCEPT AS A
WHOLE BY THE DEPOSITARY TO A NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE
DEPOSITARY TO THE DEPOSITARY OR ANOTHER NOMINEE OF THE DEPOSITARY OR BY THE
DEPOSITARY OR ANY SUCH NOMINEE TO A SUCCESSOR DEPOSITARY OR A NOMINEE OF SUCH
SUCCESSOR DEPOSITARY.](1)

                  [THIS SECURITY (OR ITS PREDECESSOR) WAS ORIGINALLY ISSUED IN A
TRANSACTION EXEMPT FROM REGISTRATION UNDER THE UNITED STATES SECURITIES ACT OF
1933, AS AMENDED (THE "SECURITIES ACT"), AND THIS SECURITY AND THE SHARES OF
COMMON STOCK ISSUABLE UPON CONVERSION THEREOF MAY NOT BE OFFERED, SOLD OR
OTHERWISE TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR AN APPLICABLE
EXEMPTION THEREFROM. EACH PURCHASER OF THIS SECURITY IS HEREBY NOTIFIED THAT THE
SELLER OF THIS SECURITY MAY BE RELYING ON THE EXEMPTION FROM THE PROVISIONS OF
SECTION 5 OF THE SECURITIES ACT PROVIDED BY RULE 144A THEREUNDER.](2)

                  [THE HOLDER OF THIS SECURITY AGREES FOR THE BENEFIT OF THE
COMPANY THAT (a) THIS SECURITY AND THE SHARES OF COMMON STOCK ISSUABLE UPON
CONVERSION THEREOF MAY BE OFFERED, RESOLD, PLEDGED OR OTHERWISE TRANSFERRED,
ONLY (i) IN THE UNITED STATES TO A PERSON WHOM THE SELLER REASONABLY BELIEVES IS
A QUALIFIED INSTITUTIONAL BUYER (AS DEFINED IN RULE 144A UNDER THE SECURITIES
ACT) IN A TRANSACTION MEETING THE REQUIREMENTS OF RULE 144A, (ii) OUTSIDE THE
UNITED STATES IN AN OFFSHORE TRANSACTION IN ACCORDANCE WITH RULE 904 UNDER THE
SECURITIES ACT, (iii) PURSUANT TO AN EXEMPTION FROM REGISTRATION UNDER THE
SECURITIES ACT PROVIDED BY RULE 144 THEREUNDER (IF AVAILABLE) OR (iv) PURSUANT
TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT, IN EACH OF
CASES (i) THROUGH (iv) IN ACCORDANCE WITH ANY APPLICABLE SECURITIES LAWS OF ANY
STATE OF THE UNITED STATES, AND (b) THE HOLDER WILL, AND EACH SUBSEQUENT HOLDER
IS REQUIRED TO, NOTIFY ANY PURCHASER OF THIS SECURITY FROM IT OF THE RESALE
RESTRICTIONS REFERRED TO IN (a) ABOVE. IN ANY CASE, THE HOLDER HEREOF WILL NOT,
DIRECTLY OR INDIRECTLY, ENGAGE IN ANY HEDGING TRANSACTIONS WITH REGARD TO THIS
SECURITY EXCEPT AS PERMITTED UNDER THE SECURITIES ACT.](2)

--------

(1)        These paragraphs should be included only if the Security is a Global
           Security.

(2)        These paragraphs to be included only if the Security is a Transfer
           Restricted Security.

                                      A-1
<PAGE>   69
                  [THE HOLDER OF THIS SECURITY IS ENTITLED TO THE BENEFITS OF A
REGISTRATION RIGHTS AGREEMENT (AS SUCH TERM IS DEFINED IN THE INDENTURE REFERRED
TO ON THE REVERSE HEREOF) AND, BY ITS ACCEPTANCE HEREOF, AGREES TO BE BOUND BY
AND TO COMPLY WITH THE PROVISIONS OF SUCH REGISTRATION RIGHTS AGREEMENT.](2)

                  THIS SECURITY MAY NOT BE SOLD OR TRANSFERRED TO, AND EACH
PURCHASER BY ITS PURCHASE OF THIS SECURITY SHALL BE DEEMED TO HAVE REPRESENTED
AND COVENANTED THAT IT IS NOT ACQUIRING THIS SECURITY FOR OR ON BEHALF OF, AND
WILL NOT TRANSFER THIS SECURITY TO, ANY PENSION OR WELFARE PLAN AS DEFINED IN
SECTION 3(1) OF THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974, AS AMENDED
("ERISA") EXCEPT THAT SUCH PURCHASE FOR OR ON BEHALF OF A PENSION OR WELFARE
PLAN SHALL BE PERMITTED:

                  (i) TO THE EXTENT SUCH PURCHASE IS MADE BY OR ON BEHALF OF A
         BANK COLLECTIVE INVESTMENT FUND MAINTAINED BY THE PURCHASER IN WHICH NO
         PLAN (TOGETHER WITH ANY OTHER PLANS MAINTAINED BY THE SAME EMPLOYER OR
         EMPLOYEE ORGANIZATION) HAS AN INTEREST IN EXCESS OF 10% OF THE TOTAL
         ASSETS IN SUCH COLLECTIVE INVESTMENT FUND, AND THE OTHER APPLICABLE
         CONDITIONS OF PROHIBITED TRANSACTION CLASS EXEMPTION 91-38 ISSUED BY
         THE DEPARTMENT OF LABOR ARE SATISFIED;

                  (ii) TO THE EXTENT SUCH PURCHASE IS MADE BY OR ON BEHALF OF AN
         INSURANCE COMPANY POOLED SEPARATE ACCOUNT MAINTAINED BY THE PURCHASER
         IN WHICH, AT ANY TIME WHILE THESE SECURITIES ARE OUTSTANDING, NO PLAN
         (TOGETHER WITH ANY OTHER PLANS MAINTAINED BY THE SAME EMPLOYER OR
         EMPLOYEE ORGANIZATION) HAS AN INTEREST IN EXCESS OF 10% OF THE TOTAL OF
         ALL ASSETS IN SUCH POOLED SEPARATE ACCOUNT, AND THE OTHER APPLICABLE
         CONDITIONS OF PROHIBITED TRANSACTION CLASS EXEMPTION 90-1 ISSUED BY THE
         DEPARTMENT OF LABOR ARE SATISFIED;

                  (iii) TO THE EXTENT SUCH PURCHASE IS MADE ON BEHALF OF A PLAN
         BY (a) AN INVESTMENT ADVISER REGISTERED UNDER THE INVESTMENT ADVISERS
         ACT OF 1940, AS AMENDED (THE "1940 ACT"), THAT HAD AS OF THE LAST DAY
         OF ITS MOST RECENT FISCAL YEAR TOTAL ASSETS UNDER ITS MANAGEMENT AND
         CONTROL IN EXCESS OF $50.0 MILLION AND HAD STOCKHOLDERS' OR PARTNERS'
         EQUITY IN EXCESS OF $750,000, AS SHOWN IN ITS MOST RECENT BALANCE SHEET
         PREPARED IN ACCORDANCE WITH GENERALLY ACCEPTED ACCOUNTING PRINCIPLES,
         OR (b) A BANK AS DEFINED IN SECTION 202(a)(2) OF THE 1940 ACT WITH
         EQUITY CAPITAL IN EXCESS OF $1.0 MILLION AS OF THE LAST DAY OF ITS MOST
         RECENT FISCAL YEAR, OR (c) AN INSURANCE COMPANY WHICH IS QUALIFIED
         UNDER THE LAWS OF MORE THAN ONE STATE TO MANAGE, ACQUIRE OR DISPOSE OF
         ANY ASSETS OF A PENSION OR WELFARE PLAN, WHICH INSURANCE COMPANY HAS AS
         OF THE LAST DAY OF ITS MOST RECENT FISCAL YEAR, NET WORTH IN EXCESS OF
         $1.0 MILLION AND WHICH IS SUBJECT TO SUPERVISION AND EXAMINATION BY A
         STATE AUTHORITY HAVING SUPERVISION OVER INSURANCE COMPANIES AND, IN ANY
         CASE, SUCH INVESTMENT ADVISER, BANK OR INSURANCE COMPANY IS OTHERWISE A
         QUALIFIED PROFESSIONAL ASSET MANAGER, AS SUCH TERM IS USED IN
         PROHIBITED TRANSACTION CLASS EXEMPTION 84-14 ISSUED BY THE DEPARTMENT
         OF LABOR, AND THE ASSETS OF SUCH PLAN WHEN COMBINED WITH THE ASSETS OF
         OTHER PLANS ESTABLISHED OR MAINTAINED BY THE SAME EMPLOYER (OR
         AFFILIATE THEREOF) OR EMPLOYEE ORGANIZATION AND MANAGED BY SUCH
         INVESTMENT ADVISER, BANK OR INSURANCE COMPANY, DO NOT REPRESENT MORE
         THAN 20% OF THE TOTAL CLIENT ASSETS MANAGED BY SUCH INVESTMENT ADVISER,
         BANK OR INSURANCE COMPANY AT THE TIME OF THE TRANSACTION, AND THE OTHER
         APPLICABLE CONDITIONS OF SUCH EXEMPTION ARE OTHERWISE SATISFIED;

                  (iv) TO THE EXTENT SUCH PLAN IS A GOVERNMENTAL PLAN (AS
         DEFINED AS SECTION 3(33) OF ERISA) WHICH IS NOT SUBJECT TO THE
         PROVISIONS OF TITLE 1 OF ERISA OR SECTION 401 OF THE INTERNAL REVENUE
         CODE OF 1986, AS AMENDED (THE "CODE");

                  (v) TO THE EXTENT SUCH PURCHASE IS MADE BY OR ON BEHALF OF AN
         INSURANCE COMPANY USING THE ASSETS OF ITS GENERAL ACCOUNT, THE RESERVES
         AND LIABILITIES FOR THE GENERAL ACCOUNT CON-

                                      A-2
<PAGE>   70
         TRACTS HELD BY OR ON BEHALF OF ANY PLAN, TOGETHER WITH ANY OTHER PLANS
         MAINTAINED BY THE SAME EMPLOYER (OR ITS AFFILIATES) OR EMPLOYEE
         ORGANIZATION, DO NOT EXCEED 10% OF THE TOTAL RESERVES AND LIABILITIES
         OF THE INSURANCE COMPANY GENERAL ACCOUNT (EXCLUSIVE OF SEPARATE ACCOUNT
         LIABILITIES), PLUS SURPLUS AS SET FORTH IN THE NATIONAL ASSOCIATION OF
         INSURANCE COMMISSIONERS ANNUAL STATEMENT FILED WITH THE STATE OF
         DOMICILE OF THE INSURER, IN ACCORDANCE WITH PROHIBITED TRANSACTION
         CLASS EXEMPTION 95-60, AND THE OTHER APPLICABLE CONDITIONS OF SUCH
         EXEMPTION ARE OTHERWISE SATISFIED;

                  (vi) TO THE EXTENT PURCHASE IS MADE BY AN IN-HOUSE ASSET
         MANAGER WITHIN THE MEANING OF PART IV(a) OF PROHIBITED TRANSACTION
         CLASS EXEMPTION 96-23, SUCH MANAGER HAS MADE OR PROPERLY AUTHORIZED THE
         DECISION FOR SUCH PLAN TO PURCHASE THIS SECURITY, UNDER CIRCUMSTANCES
         SUCH THAT PROHIBITED TRANSACTION CLASS EXEMPTION 96-23 IS APPLICABLE TO
         THE PURCHASE AND HOLDING OF THIS SECURITY; OR

                  (vii) TO THE EXTENT SUCH PURCHASE WILL NOT OTHERWISE GIVE RISE
         TO A TRANSACTION DESCRIBED IN SECTION 406 OR SECTION 4975(c)(1) OF THE
         CODE FOR WHICH A STATUTORY OR ADMINISTRATIVE EXEMPTION IS UNAVAILABLE.

                                      A-3
<PAGE>   71
                             BROOKS AUTOMATION, INC.


CUSIP:  11434AAA8                                                        No. ___

              4.75% CONVERTIBLE SUBORDINATED NOTES DUE JUNE 1, 2008



                  Brooks Automation, Inc., a Delaware corporation (the
"COMPANY", which term shall include any successor corporation under the
Indenture referred to on the reverse hereof), promises to pay to , or registered
assigns, the principal sum of         Dollars ($) on June 1 2008 [or such
greater or lesser amount as is indicated on the Schedule of Exchanges of
Securities on the other side of this Security](3)

Interest Payment Dates:  June 1 and December 1, beginning December 1, 2001

Record Dates: May 15 and November 15

                  This Security is convertible as specified on the other side of
this Security. Additional provisions of this Security are set forth on the other
side of this Security.

                             SIGNATURE PAGE FOLLOWS


-----

(3)        This phrase should be included only if the Security is a Global
           Security.

                                      A-4
<PAGE>   72
                  IN WITNESS WHEREOF, the Company has caused this instrument to
be duly executed.

                                          BROOKS AUTOMATION, INC.


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


Attest:

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

Dated:

Trustee's Certificate of Authentication: This is one of
the Securities referred to in the within-mentioned
Indenture.

STATE STREET BANK AND TRUST COMPANY, as Trustee

-----------------------------------------------------
Authorized Signatory

By:

                                      A-5
<PAGE>   73
                       [FORM OF REVERSE SIDE OF SECURITY]


                             BROOKS AUTOMATION, INC.
              4.75% CONVERTIBLE SUBORDINATED NOTES DUE JUNE 1, 2008


1.       Interest

                  Brooks Automation, Inc. a Delaware corporation (the "COMPANY",
which term shall include any successor corporation under the Indenture
hereinafter referred to), promises to pay interest on the principal amount of
this Security at the rate of 4.75% per annum. The Company shall pay interest
semiannually on June 1 and December 1 of each year, commencing December 1, 2001.
Interest on the Securities shall accrue from the most recent date to which
interest has been paid or, if no interest has been paid, from May 23, 2001;
provided, however, that if there is not an existing Default in the payment of
interest and if this Security 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. Any reference herein to interest
accrued or payable as of any date shall include any Additional Interest accrued
or payable on such date as provided in the Registration Rights Agreement.

2.       Method of Payment

                  The Company shall pay interest on this Security (except
defaulted interest) to the person who is the Holder of this Security at the
close of business on May 15 or November 15, as the case may be, next preceding
the related interest payment date. The Holder must surrender this Security to a
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 may, however, pay
principal and interest in respect of any Certificated Security by check or wire
payable in such money; provided, however, that a Holder with an aggregate
principal amount in excess of $2,000,000 will be paid by wire transfer in
immediately available funds at the election of such Holder. The Company may mail
an interest check to the Holder's registered address. Notwithstanding the
foregoing, so long as this Security is registered in the name of a Depositary or
its nominee, all payments hereon shall be made by wire transfer of immediately
available funds to the account of the Depositary or its nominee.

3.       Paying Agent, Registrar and Conversion Agent

                  Initially, State Street Bank and Trust Company (the "TRUSTEE",
which term shall include any successor trustee under the Indenture hereinafter
referred to) will act as Paying Agent, Registrar, Primary 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, subject to certain limitations set forth in the Indenture, act
as Paying Agent or Registrar.

4.       Indenture, Limitations

                  This Security is one of a duly authorized issue of Securities
of the Company designated as its 4.75% Convertible Subordinated Notes Due June
1, 2008 (the "SECURITIES"), issued under an Indenture dated as of May 23, 2001
(together with any supplemental indentures thereto, the "INDENTURE"), between
the Company and the Trustee. Capitalized terms herein are used as defined in the
Indenture unless otherwise defined herein. The terms of this Security include
those stated in the Indenture and those required by or made part of the
Indenture by reference to the Trust Indenture Act of 1939, as amended, as in
effect on the date of the Indenture. This Security is subject to all such terms,
and the Holder of this Security is referred to the Indenture and said Act for a

                                      A-6
<PAGE>   74
statement of them. The Securities are subordinated unsecured obligations of the
Company limited to $150,000,000 aggregate principal amount plus the amount (up
to an additional $25 million) issuable upon exercise of the option in the
Purchase Agreement, subject to Section 2.7 of the Indenture. The Indenture does
not limit other debt of the Company, secured or unsecured, including Senior
Indebtedness.

5.       Provisional and Optional Redemption

                  (a) The Company may redeem any portion of the Securities at
any time prior to June 6, 2004 (a "PROVISIONAL REDEMPTION"), upon giving notice
as set forth in Section 6, at a redemption price equal to $1,000 per $1,000
principal amount of the Securities redeemed plus accrued and unpaid interest, if
any (such amount, together with the "Make-Whole Payment" described below, the
"PROVISIONAL REDEMPTION PRICE"), to but excluding the date of redemption (the
"PROVISIONAL REDEMPTION DATE") if (1) the Closing Price of the Common Stock has
exceeded 150% of the Conversion Price for at least 20 Trading Days within a
period of any 30 consecutive Trading Days ending on the Trading Day prior to the
date of mailing of the notice of Provisional Redemption (the "NOTICE DATE"), and
(2) a shelf registration statement covering resales of the Securities and the
Common Stock issuable upon conversion thereof is effective and available for use
and is expected to remain effective and available for use for the 30 days
following the Provisional Redemption Date unless registration is no longer
required.

                  Upon any such Provisional Redemption, the Company shall make
an additional payment, at its option, in cash or Common Stock or a combination
of cash and Common Stock (the "MAKE-WHOLE PAYMENT") with respect to the
Securities called for redemption to Holders on the Notice Date in an amount
equal to $142.50 per $1,000 principal amount of the Securities, less the amount
of any interest actually paid (including, if the Provisional Redemption Date
occurs after a record date but before an interest payment date, any interest
paid or to be paid in connection with such interest payment date) on such
Securities prior to the Provisional Redemption Date. Payments made in Common
Stock will be valued at 97% of the average Closing Prices of Common Stock for
the five (5) Trading Days ending on the day prior to the Provisional Redemption
Date. The Company shall make the Make-Whole Payment on all Securities called for
Provisional Redemption, including those Securities converted into Common Stock
between the Notice Date and the Provisional Redemption Date.

                  (b) Except as set forth in clause (a) of this Section 5, the
Company shall not have the option to redeem the Securities pursuant to this
Section 5 prior to June 6, 2004. Thereafter, the Company shall have the option
to redeem any portion of the Securities (an "OPTIONAL REDEMPTION") upon giving
notice as set forth in Section 6. The Optional Redemption Prices (expressed as
percentages of the principal amount) are as follows for Securities redeemed
during the periods set forth below:

<TABLE>
<CAPTION>
Period                                                                             Redemption Price
------                                                                             ----------------
<S>                                                                                <C>
Beginning on June 6, 2004 and ending on May 31, 2005........................       102.38%
Beginning on June 1, 2005 and ending on May 31, 2006........................       101.58%
Beginning on June 1, 2006 and ending on May 31, 2007........................       100.79%
Beginning on June 1, 2007 and thereafter....................................       100.00%
</TABLE>

in each case together with accrued interest up to but not including the date of
redemption (the "OPTIONAL REDEMPTION DATE"); provided that if the Optional
Redemption Date falls after an interest payment record date and on or before an
interest payment date, then the interest payment will be payable to the Holders
in whose names the Securities are registered at the close of business on the
relevant record date for payment of such interest.

                                      A-7
<PAGE>   75
6.       Notice of Redemption

                  Notice of redemption will be mailed by first-class mail at
least 20 days but not more than 60 days before the Redemption Date to each
Holder of Securities to be redeemed at its registered address. Securities 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 plus
accrued interest, if any, accrued to, but excluding, the Redemption Date,
interest shall cease to accrue on Securities or portions of them called for
redemption.

7.       Purchase of Securities at Option of Holder Upon a Change in Control

                  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 of $1,000 in excess thereof) of the
Securities held by such Holder on the date that is 30 Business Days after the
occurrence of a Change in Control, at a purchase price equal to 100% of the
principal amount thereof together with accrued interest up to, but excluding,
the Change in Control Purchase Date. The Holder shall have the right to withdraw
any Change in Control Purchase Notice (in whole or in a portion thereof that is
$1,000 or an integral multiple of $1,000 in excess thereof) at any time prior to
the close of business on the Business Day next preceding the Change in Control
Purchase Date by delivering a written notice of withdrawal to the Paying Agent
in accordance with the terms of the Indenture.

8.       Conversion

                  A Holder of a Security may convert the principal amount of
such Security (or any portion thereof equal to $1,000 or any integral multiple
of $1,000 in excess thereof) into shares of Common Stock at any time prior to
the close of business on June 1, 2008; provided, however, that if the Security
is called for redemption or subject to purchase upon a Change in Control, the
conversion right will terminate at the close of business on the Business Day
immediately preceding the Redemption Date or the Change in Control Purchase
Date, as the case may be, for such Security or such earlier date as the Holder
presents such Security for redemption or purchase (unless the Company shall
default in making the redemption payment or Change in Control Purchase Price, as
the case may be, when due, in which case the conversion right shall terminate at
the close of business on the date such default is cured and such Security is
redeemed or purchased). The initial Conversion Price is $70.23 per share,
subject to adjustment under certain circumstances. The number of shares of
Common Stock issuable upon conversion of a Security is determined by dividing
the principal amount of the Security or portion thereof converted by the
Conversion Price in effect on the Conversion Date. No fractional shares will be
issued upon conversion; in lieu thereof, an amount will be paid in cash based
upon the Closing Price (as defined in the Indenture) of the Common Stock on the
Trading Day immediately prior to the Conversion Date. To convert a Security, a
Holder must (a) complete and manually sign the conversion notice set forth below
and deliver such notice to a Conversion Agent, (b) surrender the Security to a
Conversion Agent, (c) furnish appropriate endorsements and transfer documents if
required by a Registrar or a Conversion Agent, and (d) pay any transfer or
similar tax, if required. Securities so surrendered for conversion (in whole or
in part) during the period from the close of business on any regular record date
to the opening of business on the next succeeding interest payment date
(excluding Securities or portions thereof which are either (i) called for
redemption or (ii) subject to purchase following a Change in Control, in either
case, on a date during the period beginning at the close of business on a
regular record date and ending at the opening of business on the first Business
Day after the next succeeding interest payment date, or if such interest payment
date is not a Business Day, the second such Business Day) shall also be
accompanied by payment in funds acceptable to the Company of an amount equal to
the interest payable on such interest payment date on the principal amount of
such Security then being converted, and such interest shall be payable to such
registered Holder notwithstanding the conversion of such Security, subject to
the provisions of this Indenture relating to the payment of defaulted interest
by the Company. If the Company defaults in the payment of interest payable on
such interest payment date, the Company shall promptly repay

                                      A-8
<PAGE>   76
such funds to such Holder. A Holder may convert a portion of a Security equal to
$1,000 or any integral multiple thereof. A Security in respect of which a Holder
had delivered a Change in Control Purchase Notice exercising the option of such
Holder to require the Company to purchase such Security may be converted only if
the Change in Control Purchase Notice is withdrawn in accordance with the terms
of the Indenture.

9.       Conversion Arrangement on Call for Redemption

                  Any Securities called for redemption, unless surrendered for
conversion before the close of business on the Business Day immediately
preceding the Redemption Date, may be deemed to be purchased from the Holders of
such Securities at an amount not less than the Redemption Price, together with
accrued interest, if any, to, but not including, the Redemption Date, by one or
more investment bankers or other purchasers who may agree with the Company to
purchase such Securities from the Holders, to convert them into Common Stock of
the Company and to make payment for such Securities to the Paying Agent in trust
for such Holders.

10.      Subordination

                  The indebtedness evidenced by the Securities 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.
Any Holder by accepting this Security 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 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.

11.      Denominations, Transfer, Exchange

                  The Securities 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 Securities 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 in relation thereto by law or permitted by the
Indenture.

12.      Persons Deemed Owners

                  The Holder of a Security may be treated as the owner of it for
all purposes.

13.      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 written request. After that, Holders entitled to money must
look to the Company for payment.

14.      Amendment, Supplement and Waiver

                  Subject to certain exceptions, the Indenture or the Securities
may be amended or supplemented with the consent of the Holders of at least a
majority in principal amount of the Securities then outstanding, and an existing
Default or Event of Default and its consequence or compliance with any provision
of the Indenture or the Securities may be waived in a particular instance with
the consent of the Holders of a majority in principal amount of the Securities
then outstanding. Without the consent of or notice to any Holder, the Company
and the Trustee may amend or supplement the Indenture or the Securities to,
among other things, cure any ambiguity, defect or inconsistency or make any
other change that does not adversely affect the rights of any Holder.

                                      A-9
<PAGE>   77
15.      Successor Corporation

                  When a successor corporation assumes all the obligations of
its predecessor under the Securities and the Indenture in accordance with the
terms and conditions of the Indenture, the predecessor corporation will (except
in certain circumstances specified in the Indenture) be released from those
obligations.

16.      Defaults and Remedies

                  Under the Indenture, an Event of Default includes: (i) default
for 30 days in payment of any interest on any Securities; (ii) default in
payment of any principal (including, without limitation, any premium, if any) on
the Securities when due; (iii) failure by the Company for 60 days after notice
to it to comply with any of its other agreements contained in the Indenture or
the Securities; (iv) failure by the Company to give notice to the Trustee and
Holders of a Change in Control in accordance with the Indenture; and (v) certain
events of bankruptcy, insolvency or reorganization of the Company. If an Event
of Default (other than as a result of certain events of bankruptcy, insolvency
or reorganization of the Company) occurs and is continuing, the Trustee or the
Holders of at least 25% in principal amount of the Securities then outstanding
may declare all unpaid principal to the date of acceleration on the Securities
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, insolvency or reorganization of the Company, unpaid
principal of the Securities 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 Securities except as provided in the Indenture. The
Trustee may require indemnity satisfactory to it before it enforces the
Indenture or the Securities. Subject to certain limitations, Holders of a
majority in principal amount of the Securities 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.

17.      Trustee Dealings with the Company

                  State Street Bank and Trust 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.

18.      No Recourse Against Others

                  A director, officer, employee or shareholder, as such, of the
Company shall not have any liability for any obligations of the Company under
the Securities or the Indenture nor for any claim based on, in respect of or by
reason of such obligations or their creation. The Holder of this Security by
accepting this Security waives and releases all such liability. The waiver and
release are part of the consideration for the issuance of this Security.

19.      Authentication

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

                                      A-10
<PAGE>   78
20.      Abbreviations and Definitions

                  Customary abbreviations may be used in the name of the 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 UGMA (= Uniform Gifts to Minors Act).
All terms defined in the Indenture and used in this Security but not
specifically defined herein are defined in the Indenture and are used herein as
so defined.

21.      Indenture to Control; Governing Law

                  In the case of any conflict between the provisions of this
Security and the Indenture, the provisions of the Indenture shall control. This
Security shall be governed by, and construed in accordance with, the laws of the
State of New York, without regard to principles of conflicts of law.

                  The Company will furnish to any Holder, upon written request
and without charge, a copy of the Indenture. Requests may be made to: Brooks
Automation, Inc., 15 Elizabeth Drive, Chelmsford, Massachusetts 01824,
Attention: Treasurer.

                                      A-11
<PAGE>   79
                                ASSIGNMENT FORM


                  To assign this Security, fill in the form below:

                  I or we assign and transfer this Security to

     -----------------------------------------------------------------------
                  (Insert assignee's soc. sec. or tax I.D. no.)


     -----------------------------------------------------------------------


     -----------------------------------------------------------------------


     -----------------------------------------------------------------------


              (Print or type assignee's name, address and zip code)
and irrevocably appoint


     -----------------------------------------------------------------------

agent to transfer this Security on the books of the Company. The agent may
substitute another to act for him or her.

                                                     Your Signature:


Date:
     ---------------------------------------         --------------------------
                                                     (Sign exactly as your name
                                                     appears on the other side
                                                     of this Security)

*Signature guaranteed by:

By:
   ----------------------------------------

         *         Signature(s) must be guaranteed by a qualified guarantor
                   institution with membership in an approved signature
                   guarantee program pursuant to Rule 17Ad-15 under the
                   Securities Exchange Act of 1934.
<PAGE>   80
                               CONVERSION NOTICE


                  To convert this Security into Common Stock of the Company,
check the box: [ ]

                  To convert only part of this Security, state the principal
amount to be converted (must be $1,000 or a multiple of $1,000): $------------.

                  If you want the stock certificate made out in another person's
name, fill in the form below:

     -----------------------------------------------------------------------
                  (Insert assignee's soc. sec. or tax I.D. no.)

     -----------------------------------------------------------------------

     -----------------------------------------------------------------------

     -----------------------------------------------------------------------
              (Print or type assignee's name, address and zip code)

                                                     Your Signature:


Date:
     ---------------------------------------         --------------------------
                                                     (Sign exactly as your name
                                                     appears on the other side
                                                     of this Security)

*Signature guaranteed by:

By:
   --------------------------------------------------

         *         Signature(s) must be guaranteed by a qualified guarantor
                   institution with membership in an approved signature
                   guarantee program pursuant to Rule 17Ad-15 under the
                   Securities Exchange Act of 1934.
<PAGE>   81
                           OPTION TO ELECT REPURCHASE
                            UPON A CHANGE OF CONTROL


To:  Brooks Automation, Inc.

                  The undersigned registered owner of this Security hereby
irrevocably acknowledges receipt of a notice from Brooks Automation, Inc. (the
"COMPANY") as to the occurrence of a Change in Control with respect to the
Company and requests and instructs the Company to redeem the entire principal
amount of this Security, or the portion thereof (which is $1,000 or an integral
multiple thereof) below designated, in accordance with the terms of the
Indenture referred to in this Security at the Change in Control Purchase Price,
together with accrued interest to, but excluding, such date, to the registered
Holder hereof.

Date:
     ----------------         -------------------------------------------------
                               Signature(s)

                               Signature(s) must be guaranteed by a
                               qualified guarantor institution with
                               membership in an approved signature
                               guarantee program pursuant to Rule 17Ad-15
                               under the Securities Exchange Act of 1934.

                               -------------------------------------------------
                               Signature Guaranty

Principal amount to be redeemed(in an integral mul-
tiple of $1,000, if less than all):

---------------------------------------------------



NOTICE:           The signature to the foregoing Election must correspond to the
                  Name as written upon the face of this Security in every
                  particular, without alteration or any change whatsoever.
<PAGE>   82
                      SCHEDULE OF EXCHANGES OF SECURITIES(4)


                  The following exchanges, redemptions, repurchases or
conversions of a part of this global Security have been made:


<TABLE>
<CAPTION>
  Principal Amount of this
  Global Security Following                                  Amount of Decrease in        Amount of Increase in
    Such Decrease Date of       Authorized Signatory of     Principal Amount of this    Principal Amount of this
   Exchange (or Increase)         Securities Custodian          Global Security              Global Security
   ----------------------         --------------------          ---------------              ---------------
<S>                             <C>                         <C>                         <C>
</TABLE>






_____________________

(4)      This schedule should be included only if the Security is a Global
         Security.
<PAGE>   83
            CERTIFICATE TO BE DELIVERED UPON EXCHANGE OR REGISTRATION
                OF TRANSFER OF TRANSFER RESTRICTED SECURITIES(5)


Re:      4.75% Convertible Subordinated Securities Due June 1, 2008
         (the "SECURITIES") of Brooks Automation, Inc.

                  This certificate relates to $_______ principal amount of
                  Securities owned in (check applicable box)

                  [ ] book-entry or [ ] definitive form by
                  ________________ (the "TRANSFEROR").

                  The Transferor has requested a Registrar or the Trustee to
exchange or register the transfer of such Securities.

                  In connection with such request and in respect of each such
Security, the Transferor does hereby certify that the Transferor is familiar
with transfer restrictions relating to the Securities as provided in Section
2.12 of the Indenture dated as of May 23, 2001 between Brooks Automation, Inc.
and State Street Bank and Trust Company (the "INDENTURE"), and the transfer of
such Security is being made pursuant to an effective registration statement
under the Securities Act of 1933, as amended (the "SECURITIES ACT") (check
applicable box) or the transfer or exchange, as the case may be, of such
Security does not require registration under the Securities Act because (check
applicable box):

         [ ]      Such Security is being transferred pursuant to an effective
                  registration statement under the Securities Act.

         [ ]      Such Security is being acquired for the Transferor's own
                  account, without transfer.

         [ ]      Such Security is being transferred to the Company or a
                  Subsidiary (as defined in the Indenture) of the Company.

         [ ]      Such Security is being transferred to a person the Transferor
                  reasonably believes is a "qualified institutional buyer" (as
                  defined in Rule 144A or any successor provision thereto ("RULE
                  144A") under the Securities Act) that is purchasing for its
                  own account or for the account of a "qualified institutional
                  buyer", in each case to whom notice has been given that the
                  transfer is being made in reliance on such Rule 144A, and in
                  each case in reliance on Rule 144A.

         [ ]      Such Security is being transferred pursuant to and in
                  compliance with an exemption from the registration
                  requirements under the Securities Act in accordance with Rule
                  144 (or any successor thereto) ("RULE 144") under the
                  Securities Act.

         [ ]      Such Security is being transferred pursuant to and in
                  compliance with an exemption from the registration
                  requirements of the Securities Act (other than an exemption
                  referred to above) and

______________________
(5)      This certificate should only be included if this Security is a Transfer
         Restricted Security.
<PAGE>   84
                                      -2-

         as a result of which such Security will, upon such transfer, cease to
         be a "restricted security" within the meaning of Rule 144 under the
         Securities Act.





                  The Transferor acknowledges and agrees that, if the transferee
will hold any such Securities in the form of beneficial interests in a global
Security which is a "restricted security" within the meaning of Rule 144 under
the Securities Act, then such transfer can only be made pursuant to Rule 144A
under the Securities Act and such transferee must be a "qualified institutional
buyer" (as defined in Rule 144A).

Date:
     ---------------                -------------------------------------------
                                               (Insert Name of Transferor)