<PAGE>

                                                                     EXHIBIT 4.1

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

                             COR THERAPEUTICS, INC.

                                    ISSUER

                                      TO

                              FIRSTAR BANK, N.A.

                                    TRUSTEE

                               ________________


                                   INDENTURE

                            Dated as of June 11, 2001

                               ________________


                             Up to U.S. $300,000,000


               4.50% CONVERTIBLE SENIOR NOTES DUE JUNE 15, 2006


--------------------------------------------------------------------------------
<PAGE>

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                                            Page
<S>                                                                                                         <C>
RECITALS OF THE COMPANY..................................................................................      1

          ARTICLE ONE DEFINITIONS AND OTHER PROVISIONS OF GENERAL APPLICATION                                  1

SECTION 1.1       Definitions............................................................................      1
                  -----------
   Act...................................................................................................      2
   Affiliate.............................................................................................      2
   Agent Member..........................................................................................      2
   Applicable Procedures.................................................................................      2
   Authenticating Agent..................................................................................      2
   Authorized Newspaper..................................................................................      3
   Board of Directors....................................................................................      3
   Board Resolution......................................................................................      3
   Business Day..........................................................................................      3
   Change in Control.....................................................................................      3
   Closing Price Per Share...............................................................................      3
   Code..................................................................................................      4
   Commission............................................................................................      4
   Common Stock..........................................................................................      4
   Company...............................................................................................      4
   Company Notice........................................................................................      4
   Company Request.......................................................................................      4
   Constituent Person....................................................................................      5
   Conversion Agent......................................................................................      5
   Conversion Price......................................................................................      5
   Conversion Rate.......................................................................................      5
   Corporate Trust Office................................................................................      5
   corporation...........................................................................................      5
   Defaulted Interest....................................................................................      5
   Depositary............................................................................................      5
   Dollar................................................................................................      5
   DTC...................................................................................................      5
   Event of Default......................................................................................      6
   Exchange Act..........................................................................................      6
   Global Security.......................................................................................      6
   Holder................................................................................................      6
   Indenture.............................................................................................      6
   Initial Purchasers....................................................................................      6
   Interest Payment Date.................................................................................      6
   Liquidated Damages....................................................................................      6
   Maturity..............................................................................................      6
</TABLE>

                                      -i-
<PAGE>

<TABLE>
<S>                                                                                                           <C>
   Non-electing Share....................................................................................      6
   Notice of Default.....................................................................................      7
   Officers' Certificate.................................................................................      7
   Opinion of Counsel....................................................................................      7
   Outstanding...........................................................................................      7
   Paying Agent..........................................................................................      8
   Person................................................................................................      8
   Place of Conversion...................................................................................      8
   Place of Payment......................................................................................      8
   Predecessor Security..................................................................................      8
   Purchase Agreement....................................................................................      8
   Record Date...........................................................................................      9
   Record Date Period....................................................................................      9
   Redemption Date.......................................................................................      9
   Redemption Price......................................................................................      9
   Registered Securities.................................................................................      9
   Registrable Securities................................................................................      9
   Registration Default..................................................................................      9
   Registration Rights Agreement.........................................................................      9
   Regular Record Date...................................................................................      9
   Repurchase Date.......................................................................................      9
   Repurchase Price......................................................................................      9
   Responsible Officer...................................................................................      9
   Restricted Global Security............................................................................     10
   Restricted Securities Legend..........................................................................     10
   Rule 144A.............................................................................................     10
   Rule 144A Information.................................................................................     10
   Securities............................................................................................     10
   Securities Act........................................................................................     10
   Securities Act Legend.................................................................................     10
   Security Register.....................................................................................     10
   Shelf Registration Statement..........................................................................     10
   Special Record Date...................................................................................     10
   Stated Maturity.......................................................................................     10
   Subsidiary............................................................................................     11
   Successor Security....................................................................................     11
   Trading Days..........................................................................................     11
   Trust Indenture Act...................................................................................     11
   Trustee...............................................................................................     12
   United States.........................................................................................     12
   Vice President........................................................................................     12
SECTION 1.2    Compliance Certificates and Opinions......................................................     12
               ------------------------------------
SECTION 1.3    Form of Documents Delivered to the Trustee................................................     13
               ------------------------------------------
SECTION 1.4    Acts of Holders of Securities.............................................................     14
               -----------------------------
SECTION 1.5    Notices, Etc., to Trustee and Company.....................................................     16
               -------------------------------------
SECTION 1.6    Notice to Holders of Securities; Waiver...................................................     17
               ---------------------------------------
SECTION 1.7    Effect of Headings and Table of Contents..................................................     18
               ----------------------------------------
</TABLE>

                                     -ii-
<PAGE>

<TABLE>
<S>                                                                                                        <C>
SECTION 1.8    Successors and Assigns................................................................      18
               ----------------------
SECTION 1.9    Separability Clause...................................................................      18
               -------------------
SECTION 1.10   Benefits of Indenture.................................................................      18
               ---------------------
SECTION 1.11   Governing Law.........................................................................      18
               -------------
SECTION 1.12   Legal Holidays........................................................................      18
               --------------
SECTION 1.13   Conflict with Trust Indenture Act.....................................................      19
               ---------------------------------

                 ARTICLE TWO SECURITY FORMS..........................................................      19

SECTION 2.1    Form Generally........................................................................      19
               --------------
SECTION 2.2    Form of Security......................................................................      20
               ---------------
SECTION 2.3    Form of Certificate of Authentication.................................................      37
               -------------------------------------
SECTION 2.4    Form of Conversion Notice.............................................................      37
               -------------------------

                                ARTICLE THREE........................................................      39

          ARTICLE THREE ARTICLE THREE THE SECURITIES.................................................      39

SECTION 3.1    Title and Terms.......................................................................      39
               ---------------
SECTION 3.2    Denominations.........................................................................      40
               -------------
SECTION 3.3    Execution, Authentication, Delivery and Dating........................................      40
               ----------------------------------------------
SECTION 3.4    Global Securities; Non-Global Securities..............................................      41
               ----------------------------------------
SECTION 3.5    Registration, Registration of Transfer and Exchange; Restrictions on Transfer.........      43
               -----------------------------------------------------------------------------
SECTION 3.6    Mutilated, Destroyed, Lost or Stolen Securities.......................................      46
               -----------------------------------------------
SECTION 3.7    Payment of Interest; Interest Rights Preserved........................................      48
               ----------------------------------------------
SECTION 3.8    Persons Deemed Owners.................................................................      49
               ---------------------
SECTION 3.9    Cancellation..........................................................................      49
               ------------
SECTION 3.10   Computation of Interest...............................................................      50
               -----------------------
SECTION 3.11   CUSIP Numbers.........................................................................      50
               -------------

          ARTICLE FOUR SATISFACTION AND DISCHARGE....................................................      50

SECTION 4.1    Satisfaction and Discharge of Indenture...............................................      52
               ---------------------------------------
SECTION 4.2    Application of Trust Money............................................................      53
               --------------------------

                            ARTICLE FIVE REMEDIES....................................................      52

SECTION 5.1    Events of Default.....................................................................      52
               -----------------
SECTION 5.2    Acceleration of Maturity; Rescission and Annulment....................................      54
               --------------------------------------------------
SECTION 5.3    Collection of Indebtedness and Suits for Enforcement by Trustee.......................      55
               ---------------------------------------------------------------
SECTION 5.4    Trustee May File Proofs of Claim......................................................      56
               --------------------------------
SECTION 5.5    Trustee May Enforce Claims Without Possession of Securities...........................      57
               -----------------------------------------------------------
SECTION 5.6    Application of Money Collected........................................................      58
               ------------------------------
</TABLE>

                                     -iii-
<PAGE>

<TABLE>
<S>                                                                                                                     <C>
SECTION 5.7    Limitation on Suits................................................................................      58
               -------------------
SECTION 5.8    Unconditional Right of Holders to Receive Principal, Premium and Interest and to Convert...........      59
               ----------------------------------------------------------------------------------------
SECTION 5.9    Restoration of Rights and Remedies.................................................................      59
               ----------------------------------
SECTION 5.10   Rights and Remedies Cumulative.....................................................................      59
               ------------------------------
SECTION 5.11   Delay or Omission Not Waiver.......................................................................      60
               ----------------------------
SECTION 5.12   Control by Holders of Securities...................................................................      60
               --------------------------------
SECTION 5.13   Waiver of Past Defaults............................................................................      60
               -----------------------
SECTION 5.14   Undertaking for Costs..............................................................................      61
               ---------------------
SECTION 5.15   Waiver of Stay, Usury or Extension Laws............................................................      61
               ---------------------------------------

           ARTICLE SIX THE TRUSTEE                                                                                      62

SECTION 6.1    Certain Duties and Responsibilities................................................................      62
               -----------------------------------
SECTION 6.2    Notice of Defaults.................................................................................      63
               ------------------
SECTION 6.3    Certain Rights of Trustee..........................................................................      64
               -------------------------
SECTION 6.4    Not Responsible for Recitals or Issuance of Securities.............................................      65
               ------------------------------------------------------
SECTION 6.5    May Hold Securities, Act as Trustee Under Other Indentures.........................................      65
               ----------------------------------------------------------
SECTION 6.6    Money Held in Trust................................................................................      66
               -------------------
SECTION 6.7    Compensation and Reimbursement.....................................................................      66
               ------------------------------
SECTION 6.8    Corporate Trustee Required; Eligibility............................................................      67
               ---------------------------------------
SECTION 6.9    Resignation and Removal; Appointment of Successor..................................................      67
               -------------------------------------------------
SECTION 6.10   Acceptance of Appointment by Successor.............................................................      69
               --------------------------------------
SECTION 6.11   Merger, Conversion, Consolidation or Succession to Business........................................      69
               -----------------------------------------------------------
SECTION 6.12   Authenticating Agents..............................................................................      70
               ---------------------
SECTION 6.13   Disqualification; Conflicting Interests............................................................      71
               ---------------------------------------
SECTION 6.14   Preferential Collection of Claims Against Company..................................................      72
               -------------------------------------------------

          ARTICLE SEVEN CONSOLIDATION, MERGER, CONVEYANCE, TRANSFER OR LEASE                                            72

SECTION 7.1    Company May Consolidate, Etc., Only on Certain Terms...............................................      72
               ----------------------------------------------------
SECTION 7.2    Successor Substituted..............................................................................      73
               ---------------------

          ARTICLE EIGHT SUPPLEMENTAL INDENTURES       73

SECTION 8.1    Supplemental Indentures Without Consent of Holders of Securities...................................      73
               ----------------------------------------------------------------
SECTION 8.2    Supplemental Indentures with Consent of Holders of Securities......................................      75
               -------------------------------------------------------------
SECTION 8.3    Execution of Supplemental Indentures...............................................................      76
               ------------------------------------
SECTION 8.4    Effect of Supplemental Indentures..................................................................      76
               ---------------------------------
</TABLE>

                                     -iv-
<PAGE>

<TABLE>
<S>                                                                                   <C>
SECTION 8.5    Reference in Securities to Supplemental Indentures..............       77
               --------------------------------------------------
SECTION 8.6    Notice of Supplemental Indentures...............................       77
               ---------------------------------

                           ARTICLE NINE COVENANTS                                     77

SECTION 9.1    of Principal, Premium and Interest..............................       77
               ----------------------------------
SECTION 9.2    Maintenance of Offices or Agencies..............................       77
               ----------------------------------
SECTION 9.3    Money for Security Payments To Be Held in Trust.................       78
               -----------------------------------------------
SECTION 9.4    Existence.......................................................       80
               ---------
SECTION 9.5    Maintenance of Properties.......................................       80
               -------------------------
SECTION 9.6    Payment of Taxes and Other Claims...............................       80
               ---------------------------------
SECTION 9.7    Registration and Listing........................................       81
               ------------------------
SECTION 9.8    Statement by Officers as to Default.............................       81
               -----------------------------------
SECTION 9.9    Delivery of Certain Information.................................       82
               -------------------------------
SECTION 9.10   Resale of Certain Securities; Reporting Issuer..................       82
               ----------------------------------------------
SECTION 9.11   Registration Rights.............................................       83
               -------------------
SECTION 9.12   Waiver of Certain Covenants.....................................       85
               ---------------------------

                    ARTICLE TEN REDEMPTION OF SECURITIES                              86

SECTION 10.1   Right of Redemption.............................................       86
               -------------------
SECTION 10.2   Applicability of Article........................................       86
               ------------------------
SECTION 10.3   Election to Redeem; Notice to Trustee...........................       86
               -------------------------------------
SECTION 10.4   Selection by Trustee of Securities To Be Redeemed...............       86
               -------------------------------------------------
SECTION 10.5   Notice of Redemption............................................       87
               --------------------
SECTION 10.6   Deposit of Redemption Price.....................................       88
               ---------------------------
SECTION 10.7   Securities Payable on Redemption Date...........................       88
               -------------------------------------
SECTION 10.8   Securities Redeemed in Part.....................................       89
               ---------------------------
SECTION 10.9   Conversion Arrangement on Call for Redemption...................       90
               ---------------------------------------------

                   ARTICLE ELEVEN CONVERSION OF SECURITIES                            90

SECTION 11.1   Conversion Privilege and Conversion Rate........................       90
               ----------------------------------------
SECTION 11.2   Exercise of Conversion Privilege................................       91
               --------------------------------
SECTION 11.3   Fractions of Shares.............................................       93
               -------------------
SECTION 11.4   Adjustment of Conversion Rate...................................       94
               -----------------------------
SECTION 11.5   Notice of Adjustments of Conversion Rate........................      100
               ----------------------------------------
SECTION 11.6   Notice of Certain Corporate Action..............................      100
               ----------------------------------
SECTION 11.7   Company to Reserve Common Stock.................................      102
               -------------------------------
SECTION 11.8   Taxes on Conversions............................................      102
               --------------------
SECTION 11.9   Covenant as to Common Stock.....................................      102
               ---------------------------
SECTION 11.10  Cancellation of Converted Securities............................      102
               ------------------------------------
SECTION 11.11  Provision in Case of Consolidation, Merger or Sale of Assets....      103
               ------------------------------------------------------------
SECTION 11.12  Responsibility of Trustee for Conversion Provisions.............      104
               ---------------------------------------------------
</TABLE>

                                      -v-
<PAGE>

<TABLE>
<S>                                                                                                               <C>
               ARTICLE TWELVE REPURCHASE OF SECURITIES AT THE OPTION OF THE HOLDER UPON A CHANGE IN CONTROL       105

SECTION 12.1   Right to Require Repurchase.....................................................................   105
               ---------------------------
SECTION 12.2   Conditions to the Company's Election to Pay the Repurchase Price in Common Stock................   106
               --------------------------------------------------------------------------------

SECTION 12.3   Notices; Method of Exercising Repurchase Right, Etc.............................................   107
               ----------------------------------------------------
SECTION 12.4   Certain Definitions.............................................................................   110
               -------------------

               ARTICLE THIRTEEN HOLDERS LISTS AND REPORTS BY TRUSTEE AND COMPANY; NON-RECOURSE                    112

SECTION 13.1   Company to Furnish Trustee Names and Addresses of Holders.......................................   112
               ---------------------------------------------------------
SECTION 13.2   Preservation of Information.....................................................................   112
               ---------------------------
SECTION 13.3   No Recourse Against Others......................................................................   113
               --------------------------
SECTION 13.4   Reports by Trustee..............................................................................   113
               ------------------
SECTION 13.5   Reports by Company..............................................................................   114
               ------------------
SIGNATURES
</TABLE>

                                     -vi-
<PAGE>

          INDENTURE, dated as of June 11, 2001, between COR Therapeutics, Inc.,
a corporation duly organized and existing under the laws of the State of
Delaware, having its principal office at 256 East Grand Avenue, South San
Francisco, California 94080 (herein called the "Company"), and Firstar Bank,
N.A., a national banking association, as Trustee hereunder (herein called the
"Trustee").

                            RECITALS OF THE COMPANY

          The Company has duly authorized the creation of an issue of its 4.50%
Convertible Senior Notes due June 15, 2006 (herein called the "Securities") of
substantially the tenor and amount hereinafter set forth, and to provide
therefor the Company has duly authorized the execution and delivery of this
Indenture.

          All things necessary to make the Securities, when the Securities are
executed by the Company and authenticated and delivered hereunder, the valid
obligations of the Company, and to make this Indenture a valid agreement of the
Company, in accordance with their and its terms, have been done. Further, all
things necessary to duly authorize the issuance of the Common Stock of the
Company issuable upon the conversion of the Securities, and to duly reserve for
issuance the number of shares of Common Stock issuable upon such conversion,
have been done.

          NOW, THEREFORE, THIS INDENTURE WITNESSETH:

          For and in consideration of the premises and the purchase of the
Securities by the Holders thereof, it is mutually covenanted and agreed, for the
equal and proportionate benefit of all Holders of the Securities, as follows:

                                  ARTICLE ONE

                       DEFINITIONS AND OTHER PROVISIONS
                            OF GENERAL APPLICATION

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

          For all purposes of this Indenture, except as otherwise expressly
provided or unless the context otherwise requires:

                                      -1-
<PAGE>

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

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

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

          "Act", when used with respect to any Holder of a Security, has the
          meaning specified in Section 1.4.
                               -----------

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

          "Agent Member" means any member of, or participant in, the Depositary.

          "Applicable Procedures" means, with respect to any transfer or
          transaction involving a Global Security or beneficial interest
          therein, the rules and procedures of the Depositary for such Security,
          to the extent applicable to such transaction and as in effect from
          time to time.

          "Authenticating Agent" means any Person authorized pursuant to Section
                                                                         -------
          6.12 to act on behalf of the Trustee to authenticate Securities.
          ----

                                      -2-
<PAGE>

          "Authorized Newspaper" means a newspaper in the English language,
          customarily published on each Monday, Tuesday, Wednesday, Thursday and
          Friday, whether or not published on Saturdays, Sundays or holidays,
          and of general circulation in a Place of Payment.

          "Board of Directors" means either the board of directors of the
          Company or any duly authorized committee of that board.

          "Board Resolution" means a resolution duly adopted by the Board of
          Directors, a copy of which, certified by the Secretary or an Assistant
          Secretary of the Company to have been duly adopted by the Board of
          Directors and to be in full force and effect on the date of such
          certification, shall have been delivered to the Trustee.

          "Business Day", when used with respect to any Place of Payment, Place
          of Conversion or any other place, as the case may be, means each
          Monday, Tuesday, Wednesday, Thursday and Friday which is not a day on
          which banking institutions in such Place of Payment, Place of
          Conversion or other place, as the case may be, are authorized or
          obligated by law or executive order to close; provided, however, that
                                                        --------  -------
          a day on which banking institutions in New York, New York are
          authorized or obligated by law or executive order to close shall not
          be a Business Day for purposes of Section 10.6 or Section 11.5.
                                            ------------    ------------

          "Change in Control" has the meaning specified in Section 12.4(b).
                                                           ---------------

          "Closing Price Per Share" means, with respect to the Common Stock of
          the Company, for any day, (i) the closing price regular way on the New
          York Stock Exchange or, (ii) if the Common Stock is not listed on the
          New York Stock Exchange, the closing bid price regular way on the
          Nasdaq National Market, or the reported last sales price regular way
          per share or, in case no such reported sale takes place on such day,
          the average of the reported closing bid and asked prices regular way,
          in either case, on the principal national securities exchange on which
          the Common Stock is listed or admitted to trading, or (iii) if the
          Common Stock is not quoted on the Nasdaq National

                                      -3-
<PAGE>

          Market or listed or admitted to trading on any national securities
          exchange, the average of the closing bid prices in the over-the-
          counter market as furnished by any New York Stock Exchange member firm
          selected from time to time by the Company for that purpose.

          "Code" has the meaning specified in Section 2.1.
                                              -----------

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

          "Common Stock" means the common stock, par value $0.0001 per share, of
          the Company authorized at the date of this instrument as originally
          executed. Subject to the provisions of Section 11.11, shares issuable
                                                 -------------
          on conversion or repurchase of Securities shall include only shares
          of Common Stock or shares of any class or classes of common stock
          resulting from any reclassification or reclassifications thereof;
          provided, however, that if at any time there shall be more than one
          --------  -------
          such resulting class, the shares so issuable on conversion of
          Securities shall include shares of all such classes, and the shares of
          each such class then so issuable shall be substantially in the
          proportion 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 Person named as the "Company" in the first
          paragraph of this instrument until a successor Person shall have
          become such pursuant to the applicable provisions of this Indenture,
          and thereafter "Company" shall mean such successor Person.

          "Company Notice" has the meaning specified in Section 12.3.
                                                        ------------

          "Company Request" or "Company Order" means a written request or order
          signed in the name of the Company by its Chairman of the Board, its
          Vice Chairman of the

                                      -4-
<PAGE>

          Board, its Chief Executive Officer, its President or a Vice President,
          and by its principal financial officer, Treasurer, an Assistant
          Treasurer, its Secretary or an Assistant Secretary, and delivered to
          the Trustee.

          "Constituent Person" has the meaning specified in Section 11.11.
                                                            -------------

          "Conversion Agent" means any Person authorized by the Company to
          convert Securities in accordance with Article Eleven. The Company has
                                                --------------
          initially appointed the Trustee as its Conversion Agent in the State
          of Minnesota, County of Ramsey, The City of St. Paul.

          "Conversion Price" has the meaning specified in Section 12.4(c).
                                                          ---------------

          "Conversion Rate" has the meaning specified in Section 11.1.
                                                         ------------

          "Corporate Trust Office" means the office of the Trustee at which at
          any particular time its corporate trust business shall be principally
          administered (which at the date of this Indenture is located at 101 E.
          5th Street, 12th Floor, Corporate Trust, St. Paul, Minnesota 55101).

          "corporation" means a corporation, company, association, joint-stock
          company or business trust.

          "Defaulted Interest" has the meaning specified in Section 3.7.
                                                            -----------

          "Depositary" means, with respect to any Registered Securities, a
           clearing agency that is registered as such under the Exchange Act and
           is designated by the Company to act as Depositary for such Registered
           Securities (or any successor securities clearing agency so
           registered).

          "Dollar" or "U.S.$" means a dollar or other equivalent unit in such
          coin or currency of the United States as at the time shall be legal
          tender for the payment of public and private debts.

          "DTC" means The Depository Trust Company, a New York corporation.

                                      -5-
<PAGE>

          "Event of Default" has the meaning specified in Section 5.1.
                                                          -----------

          "Exchange Act" means the United States Securities Exchange Act of 1934
          (or any successor statute), as amended from time to time.

          "Global Security" means a Registered Security that is registered in
          the Security Register in the name of a Depositary or a nominee
          thereof.

          "Holder" means the Person in whose name the Security is registered in
          the Security Register.

          "Indenture" means this instrument as originally executed or as it may
          from time to time be supplemented or amended by one or more indentures
          supplemental hereto entered into pursuant to the applicable provisions
          hereof, including, for all purposes of this instrument and any such
          supplemental indenture, the provisions of the Trust Indenture Act that
          are deemed to be a part of and govern this instrument and any such
          supplemental indenture, respectively.

          "Initial Purchasers" means Goldman, Sachs & Co., Robertson Stephens,
          Inc., Credit Suisse First Boston Corporation, CIBC World Markets Corp.
          and Needham & Company, Inc., collectively.

          "Interest Payment Date" means the Stated Maturity of an installment of
          interest on the Securities.

          "Liquidated Damages" has the meaning specified in Section 9.11.
                                                            ------------

          "Maturity", when used with respect to any Security, means the date on
          which the principal of such Security becomes due and payable as
          therein or herein provided, whether at the Stated Maturity or by
                            --------
          declaration of acceleration, call for redemption, exercise of the
          repurchase right set forth in Article Twelve or otherwise.
                                        ------- ------

          "Non-electing Share" has the meaning specified in Section 11.11.
                                                            -------------

                                      -6-
<PAGE>

          "Notice of Default" has the meaning specified in Section 5.1.
                                                           -----------

          "Officers' Certificate'" means a certificate signed by the Chairman of
          the Board, a Vice Chairman of the Board, the Chief Executive Officer,
          the President or a Vice President and by the principal financial
          officer, the Treasurer, an Assistant Treasurer, the Secretary or an
          Assistant Secretary of the Company, and delivered to the Trustee.

          "Opinion of Counsel" means a written opinion of counsel, who may be
          counsel for the Company and who shall be acceptable to the Trustee.

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

               (i)     Securities theretofore cancelled by the Trustee or
     delivered to the Trustee for cancellation;

               (ii)    Securities for the payment or redemption of which money
     in the necessary amount has been theretofore deposited with the Trustee or
     any Paying Agent (other than the Company) in trust or set aside and
     segregated in trust by the Company (if the Company shall act as its own
     Paying Agent) for the Holders of such Securities, provided that if such
     Securities are to be redeemed, notice of such redemption has been duly
     given pursuant to this Indenture or provision therefor satisfactory to the
     Trustee has been made; and

(iii) Securities which have been paid pursuant to Section 3.6 or in exchange
                                                  -----------
for or in lieu of which other Securities have been authenticated and delivered
pursuant to this Indenture, other than any such Securities in respect of which
there shall have been presented to the Trustee proof satisfactory to it that
such Securities are held by a bona fide purchaser in whose hands such Securities
are valid obligations of the Company;

provided, however, that in determining whether the Holders of the requisite
--------  -------
principal amount of Outstanding Securities are present at a meeting of Holders
of Securities for quorum purposes or have given any request, demand,
authorization, direction, notice, consent or waiver hereunder, Securities owned
by the Company or any other obligor upon the Securities or any

                                      -7-
<PAGE>

Affiliate of the Company or such other obligor shall be disregarded and deemed
not to be Outstanding, except that, in determining whether the Trustee shall be
protected in relying upon any such determination as to the presence of a quorum
or upon any such request, demand, authorization, direction, notice, consent or
waiver, only Securities which a Responsible Officer of the Trustee actually
knows to be so owned shall be so disregarded. Securities so owned which have
been pledged in good faith may be regarded as Outstanding if the pledgee
establishes to the satisfaction of the Trustee the pledgee's right so to act
with respect to such Securities and that the pledgee is not the Company or any
other obligor upon the Securities or any Affiliate of the Company or such other
obligor.

          "Paying Agent" means any Person authorized by the Company to pay the
          principal of or interest on any Securities on behalf of the Company
          and, except as otherwise specifically set forth herein, such term
          shall include the Company if it shall act as its own Paying Agent. The
          Company has initially appointed the Trustee as its Paying Agent in the
          State of Minnesota, County of Ramsey, The City of St. Paul.

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

          "Place of Conversion" has the meaning specified in Section 3.1.
                                                             -----------

          "Place of Payment" has the meaning specified in Section 3.1.

          "Predecessor Security" of any particular Security means every previous
          Security evidencing all or a portion of the same debt as that
          evidenced by such particular Security; and, for the purposes of this
          definition, any Security authenticated and delivered under Section 3.6
                                                                     -----------
          in exchange for or in lieu of a mutilated, destroyed, lost or stolen
          Security shall be deemed to evidence the same debt as the mutilated,
          destroyed, lost or stolen Security.

          "Purchase Agreement" means the Purchase Agreement, dated as of June 6,
          2001, between the Company and the

                                      -8-
<PAGE>

          Initial Purchasers, as such agreement may be amended from time to
          time.

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

          "Record Date Period" means the period from the close of business of
          any Regular Record Date next preceding any Interest Payment Date to
          the opening of business on such Interest Payment Date.

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

          "Redemption Price", when used with respect to any Security to be
          redeemed, means the price at which it is to be redeemed pursuant to
          this Indenture.

          "Registered Securities" has the meaning set forth in Section 2.1.
                                                               -----------

          "Registrable Securities" has the meaning specified in Section 9.11.
                                                                ------------

          "Registration Default" has the meaning specified in Section 9.11.
                                                              ------------

          "Registration Rights Agreement" has the meaning specified in Section
                                                                       -------
          2.2.
          ---

          "Regular Record Date" for interest payable in respect of any
          Registered Security on any Interest Payment Date means the 1st day of
          June or the 1st day of December (whether or not a Business Day), as
          the case may be, next preceding such Interest Payment Date.

          "Repurchase Date" has the meaning specified in Section 12.1.
                                                         ------------

          "Repurchase Price" has the meaning specified in Section 12.1.
                                                          ------------

          "Responsible Officer", when used with respect to the Trustee, means
          any officer within the Corporate Trust Office of the Trustee,
          including, without limitation, any vice president, assistant vice
          president, assistant treasurer, corporate trust officer or other
          employee of the Trustee customarily performing

                                      -9-
<PAGE>

          functions similar to those performed by any of the above designated
          officers, and also means, with respect to a particular corporate trust
          matter, any other officer to whom such matter is referred because of
          his knowledge and familiarity with the particular subject.

          "Restricted Global Security" has the meaning specified in Section 2.1.
                                                                    -----------

          "Restricted Securities Legend" means, collectively, the legends
          substantially in the forms of the legends required in the form of
          Security set forth in Section 2.2 to be placed upon each Security.
                                -----------

          "Rule 144A" means Rule 144A under the Securities Act (or any successor
          provision), as it may be amended from time to time.

          "Rule 144A Information" has the meaning specified in Section 9.9.
                                                               -----------

          "Securities" has the meaning ascribed to it in the first paragraph
          under the caption "Recitals of the Company".

          "Securities Act" means the United States Securities Act of 1933 (or
          any successor statute), as amended from time to time.

          "Securities Act Legend" means a Restricted Securities Legend.

          "Security Register" and "Security Registrar" have the respective
          meanings specified in Section 3.5.
                                -----------

          "Shelf Registration Statement" has the meaning specified in Section
                                                                      -------
          9.11.

          "Special Record Date" for the payment of any Defaulted Interest means
          a date fixed by the Company pursuant to Section 3.7.
                                                  -----------

          "Stated Maturity", when used with respect to any Security or any
          installment of interest thereon, means the date specified in such
          Security as the fixed date on which the principal of such Security or
          such installment of interest is due and payable.

                                     -10-
<PAGE>

          "Subsidiary" means a corporation more than 50% of the outstanding
          voting stock of which is owned, directly or indirectly, by the Company
          or by one or more other Subsidiaries, or by the Company and one or
          more other Subsidiaries. For the purposes of this definition, "voting
          stock" means stock or other similar interests in the corporation which
          ordinarily has or have voting power for the election of directors, or
          persons performing similar functions, whether at all times or only so
          long as no senior class of stock or other interests has or have such
          voting power by reason of any contingency.

          "Successor Security" of any particular Security means every Security
          issued after, and evidencing all or a portion of the same debt as that
          evidenced by, such particular Security; and, for the purposes of this
          definition, any Security authenticated and delivered under Section 3.6
                                                                     -----------
          in exchange for or in lieu of a mutilated, destroyed, lost or stolen
          Security shall be deemed to evidence the same debt as the mutilated,
          destroyed, lost or stolen Security.

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

          "Trust Indenture Act" means the Trust Indenture Act of 1939 as in
          force at the date as of which this instrument was executed; provided,
                                                                      --------
          however, that in the event the Trust Indenture Act of 1939 is amended
          -------
          after such date, "Trust Indenture Act" means, to the extent required
          by any such amendment, the Trust Indenture Act of 1939 as so amended.

                                     -11-
<PAGE>

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

          "United States" means the United States of America (including the
          States and the District of Columbia), its territories, its possessions
          and other areas subject to its jurisdiction (its "possessions"
          including Puerto Rico, the U.S. Virgin Islands, Guam, American Samoa,
          Wake Island and the Northern Mariana Islands).

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

SECTION 1.2    Compliance Certificates and Opinions.
               ------------------------------------

          Upon any application or request by the Company to the Trustee to take
any action under any provision of this Indenture, the Company shall furnish to
the Trustee an Officers' Certificate stating that all conditions precedent, if
any, provided for in this Indenture relating to the proposed action have been
complied with and, if required by the Trust Indenture Act, an Opinion of Counsel
stating that in the opinion of such counsel all such conditions precedent, if
any, have been complied with, except that in the case of any such application or
request as to which the furnishing of such documents is specifically required by
any provision of this Indenture relating to such particular application or
request, no additional certificate or opinion need be furnished.

          Every certificate or opinion with respect to compliance with a
condition or covenant provided for in this Indenture (including certificates
provided for in Section 9.8) shall include:
                -----------

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

          (2)  a brief statement as to the nature and scope of the examination
     or investigation upon which the statements

                                     -12-
<PAGE>

     or opinions contained in such certificate or opinion are based;

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

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

SECTION 1.3    Form of Documents Delivered to the Trustee.
               ------------------------------------------

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

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

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

                                     -13-
<PAGE>

SECTION 1.4      Acts of Holders of Securities.
                 -----------------------------

          (a)  request, demand, authorization, direction, notice, consent,
waiver or other action provided or permitted by this Indenture to be given or
taken by Holders of Securities may be embodied in and evidenced by one or more
instruments of substantially similar tenor signed by such Holders in person or
by an agent or proxy duly appointed in writing by such Holders. Such action
shall become effective when such instrument or instruments record is delivered
to the Trustee and, where it is hereby expressly required, to the Company. The
Trustee shall promptly deliver to the Company copies of all such instruments
delivered to the Trustee. Such instrument or instruments (and the action
embodied therein and evidenced thereby) are herein sometimes referred to as the
"Act" of the Holders of Securities signing such instrument or instruments. Proof
of execution of any such instrument or of a writing appointing any such agent or
proxy, or of the holding by any Person of a Security, shall be sufficient for
any purpose of this Indenture and (subject to Section 6.1) conclusive in favor
                                              -----------
of the Trustee and the Company if made in the manner provided in this Section.

          (b)  The fact and date of the execution by any Person of any such
instrument or writing may be proved by the affidavit of a witness of such
execution or by a certificate of a notary public or other officer authorized by
law to take acknowledgments of deeds, certifying that the individual signing
such instrument or writing acknowledged to him the execution thereof. Where such
execution is by a signer acting in a capacity other than his individual
capacity, such certificate or affidavit shall also constitute sufficient proof
of his authority.

          (c)  The principal amount and serial number of any Registered Security
held by any Person, and the date of his holding the same, shall be proved by the
Security Register.

          (d)  The fact and date of execution of any such instrument or writing
and the authority of the Person executing the same may also be proved in any
other manner which the Trustee deems sufficient; and the Trustee may in any
instance require further proof with respect to any of the matters referred to in
this Section 1.4.
     -----------

          (e)  The Company may set any day as the record date for the purpose of
determining the Holders entitled to give or take any request, demand,
authorization, direction, notice, consent, waiver or other action, or to vote on
any action,

                                     -14-
<PAGE>

authorized or permitted by this Indenture to be given or taken by Holders.
Promptly and in any case not later than ten days after setting a record date,
the Company shall notify the Trustee and the Holders of such record date. If not
set by the Company prior to the first solicitation of a Holder made by any
Person in respect of any such action, or, in the case of any such vote, prior to
such vote, the record date for any such action or vote shall be the 30th day
(or, if later, the date of the most recent list of Holders required to be
provided pursuant to Section 13.1) prior to such first solicitation or vote,
                     ------------
as the case may be. With regard to any record date, the Holders on such date (or
their duly appointed agents or proxies), and only such Persons, shall be
entitled to give or take, or vote on, the relevant action, whether or not such
Holders remain Holders after such record date. Notwithstanding the foregoing,
the Company shall not set a record date for, and the provisions of this
paragraph shall not apply with respect to, any notice, declaration or direction
referred to in the next paragraph.

          Upon receipt by the Trustee from any Holder of (i) any notice of
default or breach referred to in Section 5.1(4), if such default or breach has
                                 --------------
occurred and is continuing and the Trustee shall not have given such a notice to
the Company, (ii) any declaration of acceleration referred to in Section 5.2, if
                                                                 -----------
an Event of Default has occurred and is continuing and the Trustee shall not
have given such a declaration to the Company, or (iii) any direction referred to
in Section 5.12, if the Trustee shall not have taken the action specified in
   ------------
such direction, then, with respect to clauses (ii) and (iii), a record date
shall automatically and without any action by the Company or the Trustee be set
for determining the Holders entitled to join in such declaration or direction,
which record date shall be the close of business on the tenth day (or, if such
day is not a Business Day, the first Business Day thereafter) following the day
on which the Trustee receives such declaration or direction, and, with respect
to clause (i), the Trustee may set any day as a record date for the purpose of
determining the Holders entitled to join in such notice of default. Promptly
after such receipt by the Trustee of any such declaration or direction referred
to in clause (ii) or (iii), and promptly after setting any record date with
respect to clause (i), and as soon as practicable thereafter, the Trustee shall
notify the Company and the Holders of any such record date so fixed. The Holders
on such record date (or their duly appointed agents or proxies), and only such
Persons, shall be entitled to join in such notice, declaration or direction,
whether or not such Holders remain Holders after such record

                                     -15-
<PAGE>

date; provided that, unless such notice, declaration or direction shall have
become effective by virtue of Holders of the requisite principal amount of
Securities on such record date (or their duly appointed agents or proxies)
having joined therein on or prior to the 90th day after such record date, such
notice, declaration or direction shall automatically and without any action by
any Person be cancelled and of no further effect. Nothing in this paragraph
shall be construed to prevent a Holder (or a duly appointed agent or proxy
thereof) from giving, before or after the expiration of such 90-day period, a
notice, declaration or direction contrary to or different from, or, after the
expiration of such period, identical to, the notice, declaration or direction to
which such record date relates, in which event a new record date in respect
thereof shall be set pursuant to this paragraph. In addition, nothing in this
paragraph shall be construed to render ineffective any notice, declaration or
direction of the type referred to in this paragraph given at any time to the
Trustee and the Company by Holders (or their duly appointed agents or proxies)
of the requisite principal amount of Securities on the date such notice,
declaration or direction is so given.

          (f)  Except as provided in Sections 5.12 and 5.13, any request,
demand, authorization, direction, notice, consent, election, waiver or other Act
of the Holder of any Security shall bind every future Holder of the same
Security and the Holder of every Security issued upon the registration of
transfer thereof or in exchange therefor or in lieu thereof in respect of
anything done, omitted or suffered to be done by the Trustee or the Company in
reliance thereon, whether or not notation of such action is made upon such
Security.

SECTION 1.5      Notices, Etc., to Trustee and Company.
                 -------------------------------------

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

          (1)  the Trustee by any Holder of Securities or by the Company shall
     be sufficient for every purpose hereunder if made, given, furnished or
     filed in writing to or with the Trustee and received at its Corporate Trust
     Office, Attention: Corporate Trust Department, and shall be deemed given
     when received.

          (2)  the Company by the Trustee or by any Holder of Securities shall
     be sufficient for every purpose hereunder

                                     -16-
<PAGE>

     (unless otherwise herein expressly provided) if in writing, mailed, first-
     class postage prepaid, or telecopied and confirmed by mail, first-class
     postage prepaid, or delivered by hand or overnight courier, addressed to
     the Company at 256 E. Grand Avenue, South, San Francisco, CA 94080,
     Attention: Vice President, Finance, or at any other address previously
     furnished in writing to the Trustee by the Company, and shall be deemed
     given when received.

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


SECTION 1.6      Notice to Holders of Securities; Waiver.
                 ---------------------------------------

          Except as otherwise expressly provided herein, where this Indenture
provides for notice to Holders of Securities of any event, such notice shall be
sufficiently given to Holders if in writing and mailed, first-class postage
prepaid, to each Holder of a Security affected by such event, at the address of
such Holder as it appears in the Security Register, not earlier than the
earliest date and not later than the latest date prescribed for the giving of
such notice.

          Neither the failure to mail such notice, nor any defect in any notice
so mailed, to any particular Holder of a Registered Security shall affect the
sufficiency of such notice with respect to other Holders of Registered
Securities. In case by reason of the suspension of regular mail service or by
reason of any other cause it shall be impracticable to give such notice by mail,
then such notification to Holders of Registered Securities as shall be made with
the approval of the Trustee, which approval shall not be unreasonably withheld
or delayed, shall constitute a sufficient notification to such Holders for every
purpose hereunder.

          Such notice shall be deemed to have been given when such notice is
mailed.

          In addition to notices by mail, the Company undertakes that any notice
of redemption of the Securities, or notice of any Change in Control and of the
related repurchase right arising as a result thereof, shall further include a
public announcement thereof by release made to Reuters Economic Services and
Bloomberg Business News.

                                     -17-
<PAGE>

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

SECTION 1.7      Effect of Headings and Table of Contents.
                 ----------------------------------------

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

SECTION 1.8      Successors and Assigns.
                 ----------------------

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

SECTION 1.9      Separability Clause.
                 -------------------

          In case any provision in this Indenture or 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 1.10     Benefits of Indenture.
                 ---------------------

          Except as provided in the next sentence, nothing in this Indenture or
in the Securities, express or implied, shall give to any Person, other than the
parties hereto and their successors and assigns hereunder and the Holders of
Securities, any benefit or legal or equitable right, remedy or claim under this
Indenture.

SECTION 1.11     Governing Law.
                 -------------

          THIS INDENTURE AND THE SECURITIES SHALL BE GOVERNED BY AND CONSTRUED
IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK, THE UNITED STATES OF
AMERICA, WITHOUT REGARD TO THE CONFLICTS OF LAWS PRINCIPLES THEREOF.

SECTION 1.12     Legal Holidays.
                 --------------

          In any case where any Interest Payment Date, Redemption Date,
Repurchase Date or Stated Maturity of any Security or the last day on which a
Holder of a Security has a

                                     -18-
<PAGE>

right to convert his Security shall not be a Business Day at a Place of Payment
or Place of Conversion, as the case may be, then (notwithstanding any other
provision of this Indenture or of the Securities) payment of principal of,
premium, if any, or interest on, or the payment of the Repurchase Price (whether
the same is payable in cash or in shares of Common Stock) with respect to, or
delivery for conversion of, such Security need not be made at such Place of
Payment or Place of Conversion, as the case may be, on or by such day, but may
be made on or by the next succeeding Business Day at such Place of Payment or
Place of Conversion, as the case may be, with the same force and effect as if
made on the Interest Payment Date, Redemption Date or Repurchase Date, or at the
Stated Maturity or by such last day for conversion; provided, however, that in
                                                    --------  -------
the case that payment is made on such succeeding Business Day, no interest shall
accrue on the amount so payable for the period from and after such Interest
Payment Date, Redemption Date, Repurchase Date, Stated Maturity or last day for
conversion, as the case may be.

SECTION 1.13     Conflict with Trust Indenture Act.
                 ---------------------------------

          If any provision hereof limits, qualifies or conflicts with a
provision of the Trust Indenture Act that is required under such Act to be a
part of and govern this Indenture, the latter provision shall control. If any
provision of this Indenture modifies or excludes any provision of the Trust
Indenture Act that may be so modified or excluded, the latter provision shall be
deemed to apply to this Indenture as so modified or to be excluded, as the case
may be. Until such time as this Indenture shall be qualified under the Trust
Indenture Act, this Indenture, the Company and the Trustee shall be deemed for
all purposes hereof to be subject to and governed by the Trust Indenture Act to
the same extent as would be the case if this Indenture were so qualified on the
date hereof.

                                  ARTICLE TWO

                                SECURITY FORMS

SECTION 2.1      Form Generally.
                 --------------

          The Securities shall be in substantially the form set forth in this
Article, with such appropriate insertions, omissions, substitutions and other
variations as are required or

                                     -19-
<PAGE>

permitted by this Indenture, and may have such letters, numbers or other marks
of identification and such legends or endorsements placed thereon as may be
required to comply with the rules of any securities exchange or the Internal
Revenue Code of 1986, as amended, and regulations thereunder (the "Code"), or as
may, consistently herewith, be determined by the officers executing such
Securities, as evidenced by their execution thereof. All Securities shall be
issued in registered form, as opposed to bearer form, and shall sometimes be
referred to as "Registered Securities".

          The Trustee's certificates of authentication shall be in substantially
the form set forth in Section 2.3.
                      -----------

          Conversion notices shall be in substantially the form set forth in
Section 2.4.

          Repurchase notices shall be substantially in the form set forth in
Section 2.2.
-----------

          The Securities shall be printed, lithographed, typewritten or engraved
or produced by any combination of these methods on steel engraved borders if so
required by any securities exchange upon which the Securities may be listed, or
may be produced in any other manner permitted by the rules of any such
securities exchange, or, if the Securities are not listed on a securities
exchange, in any other manner approved by the Company, all as determined by the
officers executing such Securities, as evidenced by their execution thereof.

          Upon their original issuance, Securities shall be issued in the form
of one or more Global Securities without interest coupons and shall be
registered in the name of DTC, as Depositary, or its nominee and deposited with
the Trustee, as custodian for DTC, for credit by DTC to the respective accounts
of beneficial owners of the Securities represented thereby (or such other
accounts as they may direct). Such Global Security, together with its Successor
Securities which are Global Securities, are collectively herein called the
"Restricted Global Security".

SECTION 2.2      Form of Security
                 ---------------

                                [FORM OF FACE]

          [THE FOLLOWING LEGEND SHALL APPEAR ON THE FACE OF EACH RESTRICTED
SECURITY OTHER THAN ANY RESTRICTED GLOBAL SECURITY:

                                     -20-
<PAGE>

          THIS NOTE AND ANY COMMON STOCK ISSUABLE UPON THE CONVERSION OF THIS
NOTE HAVE NOT BEEN REGISTERED UNDER THE U.S. SECURITIES ACT OF 1933, AS AMENDED
(THE "SECURITIES ACT"), AND MAY NOT BE SOLD OR OTHERWISE TRANSFERRED IN THE
ABSENCE OF SUCH REGISTRATION OR AN APPLICABLE EXEMPTION THEREFROM. EACH
PURCHASER OF THIS NOTE IS HEREBY NOTIFIED THAT THE SELLER OF THIS NOTE MAY BE
RELYING ON THE EXEMPTION FROM THE PROVISIONS OF SECTION 5 OF THE SECURITIES ACT
PROVIDED BY RULE 144A THEREUNDER.

          THIS NOTE AND ANY COMMON STOCK ISSUABLE UPON CONVERSION OF THIS NOTE
MAY NOT BE OFFERED, SOLD, PLEDGED OR OTHERWISE TRANSFERRED EXCEPT (A) (1) TO A
PERSON WHO THE TRANSFEROR REASONABLY BELIEVES IS A QUALIFIED INSTITUTIONAL BUYER
WITHIN THE MEANING OF RULE 144A UNDER THE SECURITIES ACT ACQUIRING FOR ITS OWN
ACCOUNT OR THE ACCOUNT OF A QUALIFIED INSTITUTIONAL BUYER IN A TRANSACTION
MEETING THE REQUIREMENTS OF RULE 144A, (2) PURSUANT TO AN EXEMPTION FROM
REGISTRATION UNDER THE SECURITIES ACT PROVIDED BY RULE 144 THEREUNDER (IF
AVAILABLE), (3) TO AN INSTITUTIONAL INVESTOR THAT IS AN ACCREDITED INVESTOR
WITHIN THE MEANING OF RULE 501(A)(1), (2), (3) OR (7) OF REGULATION D UNDER THE
SECURITIES ACT PURSUANT TO AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES
ACT (IF AVAILABLE) OR (4) PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER
THE SECURITIES ACT, AND (B) IN ACCORDANCE WITH ALL APPLICABLE SECURITIES LAWS OF
THE STATES OF THE UNITED STATES AND OTHER JURISDICTIONS.

          THIS NOTE, ANY SHARES OF COMMON STOCK ISSUABLE UPON ITS CONVERSION AND
ANY RELATED DOCUMENTATION MAY BE AMENDED OR SUPPLEMENTED FROM TIME TO TIME TO
MODIFY THE RESTRICTIONS ON RESALES AND OTHER TRANSFERS OF THIS NOTE AND ANY SUCH
SHARES TO REFLECT ANY CHANGE IN APPLICABLE LAW OR REGULATION (OR THE
INTERPRETATION THEREOF) OR IN PRACTICES RELATING TO THE RESALE OR TRANSFER OF
RESTRICTED SECURITIES GENERALLY. THE HOLDER OF THIS NOTE AND SUCH SHARES SHALL
BE DEEMED BY THE ACCEPTANCE OF THIS NOTE AND ANY SUCH SHARES TO HAVE AGREED TO
ANY SUCH AMENDMENT OR SUPPLEMENT.]

          [THE FOLLOWING LEGEND SHALL APPEAR ON THE FACE OF EACH RESTRICTED
GLOBAL SECURITY:

          THE SECURITIES EVIDENCED BY THIS GLOBAL SECURITY AND ANY COMMON STOCK
ISSUABLE UPON THE CONVERSION OF THE SECURITIES HAVE NOT BEEN REGISTERED UNDER
THE U.S. SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"), AND MAY NOT
BE SOLD OR OTHERWISE TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR AN
APPLICABLE EXEMPTION THEREFROM. EACH PURCHASER OF ANY

                                     -21-
<PAGE>

BENEFICIAL INTEREST IN THE SECURITIES IS HEREBY NOTIFIED THAT THE SELLER OF SUCH
BENEFICIAL INTEREST IN THE SECURITIES MAY BE RELYING ON THE EXEMPTION FROM THE
PROVISIONS OF SECTION 5 OF THE SECURITIES ACT PROVIDED BY RULE 144A THEREUNDER.

          EACH BENEFICIAL OWNER OF AN INTEREST IN ANY OF THE SECURITIES
EVIDENCED BY THIS GLOBAL SECURITY (INCLUDING ANY PARTICIPANT IN THE DEPOSITARY
HOLDING THE GLOBAL SECURITY THAT IS SHOWN AS HOLDING SUCH AN INTEREST ON THE
RECORDS OF SUCH DEPOSITARY AND EACH BENEFICIAL OWNER THAT HOLDS THROUGH ANY SUCH
PARTICIPANT) AGREES FOR THE BENEFIT OF COR THERAPEUTICS, INC. (THE "COMPANY")
THAT (A) ANY BENEFICIAL INTEREST IN THE SECURITIES AND ANY SHARES OF COMMON
STOCK ISSUABLE UPON THEIR CONVERSION MAY BE RESOLD, PLEDGED OR OTHERWISE
TRANSFERRED ONLY (I) TO A PERSON WHO THE SELLER REASONABLY BELIEVES IS A
QUALIFIED INSTITUTIONAL BUYER WITHIN THE MEANING OF RULE 144A UNDER THE
SECURITIES ACT ACQUIRING FOR ITS OWN ACCOUNT OR THE ACCOUNT OF A QUALIFIED
INSTITUTIONAL BUYER IN A TRANSACTION MEETING THE REQUIREMENTS OF RULE 144A, (II)
PURSUANT TO THE EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT PROVIDED BY
RULE 144 THEREUNDER (IF AVAILABLE), (III) TO AN INSTITUTIONAL INVESTOR THAT IS
AN ACCREDITED INVESTOR WITHIN THE MEANING OF RULE 501(a)(1), (2), (3) OR (7) OF
REGULATION D UNDER THE SECURITIES ACT PURSUANT TO AN EXEMPTION FROM REGISTRATION
UNDER THE SECURITIES ACT (IF AVAILABLE) OR (IV) PURSUANT TO AN EFFECTIVE
REGISTRATION STATEMENT UNDER THE SECURITIES ACT AND IN EACH OF CASES (I) THROUGH
(V) IN ACCORDANCE WITH ANY APPLICABLE SECURITIES LAWS OF THE STATES AND OTHER
JURISDICTIONS OF THE UNITED STATES AND THAT (B) THE BENEFICIAL OWNER WILL, AND
EACH SUBSEQUENT BENEFICIAL OWNER OF AN INTEREST IN ANY OF THE SECURITIES
EVIDENCED BY THIS GLOBAL SECURITY OR ANY COMMON STOCK ISSUABLE UPON CONVERSION
THEREOF IS REQUIRED TO, NOTIFY ANY PURCHASER OF ANY BENEFICIAL INTEREST IN THE
SECURITIES OR SUCH COMMON STOCK ISSUABLE UPON ITS CONVERSION FROM IT OF THE
RESALE RESTRICTIONS REFERRED TO IN (A) ABOVE.

          THIS SECURITY, ANY SHARES OF COMMON STOCK ISSUABLE UPON ITS CONVERSION
AND ANY RELATED DOCUMENTATION MAY BE AMENDED OR SUPPLEMENTED FROM TIME TO TIME
TO MODIFY THE RESTRICTIONS ON RESALES AND OTHER TRANSFERS OF THIS SECURITY AND
ANY SUCH SHARES TO REFLECT ANY CHANGE IN APPLICABLE LAW OR REGULATION (OR THE
INTERPRETATION THEREOF) OR IN PRACTICES RELATING TO THE RESALE OR TRANSFER OF
RESTRICTED SECURITIES GENERALLY. THE HOLDER AND BENEFICIAL OWNERS OF AN INTEREST
IN THIS SECURITY AND ANY SHARES OF COMMON STOCK ISSUABLE ON CONVERSION SHALL BE
DEEMED BY THE ACCEPTANCE OF THIS SECURITY AND THE BENEFICIAL INTERESTS THEREIN

                                     -22-
<PAGE>

AND ANY SUCH SHARES TO HAVE AGREED TO ANY SUCH AMENDMENT OR SUPPLEMENT.]

          [THE FOLLOWING LEGEND SHALL APPEAR ON THE FACE OF EACH GLOBAL
SECURITY:

          THIS SECURITY IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE
HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF THE DEPOSITARY OR A
NOMINEE OF THE DEPOSITARY, WHICH MAY BE TREATED BY THE COMPANY, THE TRUSTEE AND
ANY AGENT THEREOF AS OWNER AND HOLDER OF THIS SECURITY FOR ALL PURPOSES.]

          [THE FOLLOWING LEGEND SHALL APPEAR ON THE FACE OF EACH GLOBAL SECURITY
FOR WHICH THE DEPOSITORY TRUST COMPANY IS TO BE THE DEPOSITARY:

          UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE
OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("DTC"), TO THE ISSUER
OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE, OR PAYMENT, AND ANY
CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH OTHER NAME
AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE
TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED
REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE, OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER
HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.]

                                     -23-
<PAGE>

                            COR THERAPEUTICS, INC.


                         4.50% CONVERTIBLE SENIOR NOTE


                               DUE JUNE 15, 2006

No. __                                                           U.S.$__________

CUSIP No. 217753 AE 2

          COR THERAPEUTICS, INC., a corporation duly organized and existing
under the laws of the State of Delaware (herein called the "Company", which term
includes any successor Person under the Indenture referred to on the reverse
hereof), for value received, hereby promises to pay to CEDE & CO., or registered
assigns, the principal sum of ________________ United States Dollars
(U.S.$___________) [if this Security is a Global Security, then insert -- (which
principal amount may from time to time be increased or decreased to such other
principal amounts (which, taken together with the principal amounts of all other
Outstanding Securities, shall not exceed $300,000,000 in the aggregate at any
time) by adjustments made on the records of the Trustee hereinafter referred to
in accordance with the Indenture)] on June 15, 2006 and to pay interest thereon,
from June 11, 2001, or from the most recent Interest Payment Date (as defined
below) to which interest has been paid or duly provided for, semi-annually in
arrears on June 15 and December 15 in each year (each, an "Interest Payment
Date"), commencing December 15, 2001, at the rate of 4.50% per annum, until the
principal hereof is due, and at the rate of 4.50% per annum on any overdue
principal and premium, if any, and, to the extent permitted by law, on any
overdue interest. The interest so payable, and punctually paid or duly provided
for, on any Interest Payment Date will, as provided in the Indenture, be paid to
the Person in whose name this Security (or one or more Predecessor Securities)
is registered at the close of business on the Regular Record Date for such
interest, which shall be the 1st day of June or the 1st day of December (whether
or not a Business Day), as the case may be, next preceding such Interest Payment
Date. Except as otherwise provided in the Indenture, any such interest not so
punctually paid or duly provided for will forthwith cease to be payable to the
Holder on such Regular Record Date and may either be paid to the Person in whose
name this Security (or one or more Predecessor Securities) is registered at the
close of business on a Special Record Date for the payment of such Defaulted
Interest to be fixed by the Company, notice whereof shall be given to Holders of
Registered Securities not less than 10 days prior to such Special Record

                                     -24-
<PAGE>

Date, or be paid at any time in any other lawful manner not inconsistent with
the requirements of any securities exchange on which the Securities may be
listed, and upon such notice as may be required by such exchange, all as more
fully provided in the Indenture. Payments of principal shall be made upon the
surrender of this Security at the option of the Holder at the Corporate Trust
Office of the Trustee, or at such other office or agency of the Company as may
be designated by it for such purpose in such coin or currency of the United
States of America as at the time of payment shall be legal tender for the
payment of public and private debts, or at such other offices or agencies as the
Company may designate, by United States Dollar check drawn on, or wire transfer
to, a United States Dollar account (such a wire transfer to be made only to a
Holder of an aggregate principal amount of Registered Securities in excess of
U.S.$2,000,000, and only if such Holder shall have furnished wire instructions
in writing to the Trustee no later than 15 days prior to the relevant payment
date) maintained by the payee with a bank. Payment of interest on this Security
may be made by United States Dollar check mailed to the address of the Person
entitled thereto as such address shall appear in the Security Register, or, upon
written application by the Holder to the Security Registrar setting forth wire
instructions not later than the relevant Record Date, by wire transfer to a
United States Dollar account (such a wire transfer to be made only to a Holder
of an aggregate principal amount of Registered Securities in excess of
U.S.$2,000,000 and only if such Holder shall have furnished wire instructions in
writing to the Trustee no later than 15 days prior to the relevant payment date)
maintained by the payee with a bank.

          Except as specifically provided herein and in the Indenture, the
Company shall not be required to make any payment with respect to any tax,
assessment or other governmental charge imposed by any government or any
political subdivision or taxing authority thereof or therein.

          Reference is hereby made to the further provisions of this Security
set forth on the reverse hereof, which further provisions shall for all purposes
have the same effect as if set forth at this place.

          Unless the certificate of authentication hereon has been executed by
the Trustee referred to on the reverse hereof or an Authenticating Agent by the
manual signature of one of their respective authorized signatories, this
Security shall not be entitled to any benefit under the Indenture or be valid or
obligatory for any purpose.

                                     -25-
<PAGE>

          IN WITNESS WHEREOF, the Company has caused this Security to be duly
executed under its corporate seal.

                                        COR THERAPEUTICS, INC.

[Corporate Seal]


                                        By:___________________________
                                            Name:
                                            Title:

Attest:



________________________
Name:
Title:

                                     -26-
<PAGE>

                               [FORM OF REVERSE]

          This Security is one of a duly authorized issue of securities of the
Company designated as its "4.50% Convertible Senior Notes due June 15, 2006"
(herein called the "Securities"), limited in aggregate principal amount to
U.S.$300,000,000, issued and to be issued under an Indenture, dated as of June
11, 2001 (herein called the "Indenture"), between the Company and Firstar Bank,
N.A., as Trustee (herein called the "Trustee", which term includes any successor
trustee under the Indenture), to which Indenture and all indentures supplemental
thereto reference is hereby made for a statement of the respective rights,
limitations of rights, duties and immunities thereunder of the Company, the
Trustee and the Holders of the Securities and of the terms upon which the
Securities are, and are to be, authenticated and delivered. As provided in the
Indenture and subject to certain limitations therein set forth, Registered
Securities are exchangeable for a like aggregate principal amount of Registered
Securities of any authorized denominations as requested by the Holder
surrendering the same upon surrender of the Registered Security or Registered
Securities to be exchanged, at the Corporate Trust Office of the Trustee. The
Trustee upon such surrender by the Holder will issue the new Registered
Securities in the requested denominations.

          No sinking fund is provided for the Securities.

          The Securities are subject to redemption at the option of the Company
at any time on or after June 15, 2004, in whole or in part, upon not less than
30 nor more than 60 days' notice to the Holders prior to the Redemption Date at
the following Redemption Prices (expressed as percentages of the principal
amount) for the twelve-month period beginning on June 15 of the following years:

            Year                   Redemption Price
            ----                   ----------------
            2004.................        101.8%
            2005.................        100.9%

and at a Redemption Price equal to 100% of the principal amount on June 15,
2006, together, in each case, with accrued interest to the Redemption Date;
provided, however, that interest installments on Securities whose Stated
--------  -------
Maturity is on or prior to such Redemption Date will be payable to the Holders
of such Securities, or one or more Predecessor Securities, of record at

                                     -27-
<PAGE>

the close of business on the relevant Record Dates referred to on the face
hereof, all as provided in the Indenture.

          In the event of a redemption of the Securities, the Company will not
be required (a) to register the transfer or exchange of Registered Securities
for a period of 15 days immediately preceding the date notice is given
identifying the serial numbers of the Securities called for such redemption or
(b) to register the transfer or exchange of any Registered Security, or portion
thereof, called for redemption.

          Notice to the Holders will be given not less than 30 nor more than 60
days prior to the Redemption Date as provided in the Indenture.

          In any case where the due date for the payment of the principal of,
premium, if any, interest, or Liquidated Damages on any Security or the last day
on which a Holder of a Security has a right to convert his Security shall be, at
any Place of Payment or Place of Conversion, as the case may be, a day on which
banking institutions at such Place of Payment or Place of Conversion are
authorized or obligated by law or executive order to close, then payment of
principal, premium, if any, interest, or Liquidated Damages, or delivery for
conversion of such Security need not be made on or by such date at such place
but may be made on or by the next succeeding day at such place which is not a
day on which banking institutions are authorized or obligated by law or
executive order to close, with the same force and effect as if made on the date
for such payment or the date fixed for redemption or repurchase, or by such last
day for conversion, and no interest shall accrue on the amount so payable for
the period from and after such due date.

          Subject to and upon compliance with the provisions of the Indenture,
the Holder of this Security is entitled, at his option, at any time following
the original issue date of the Securities and on or before the close of business
on June 15, 2006, or in case this Security or a portion hereof is called for
redemption or the Holder hereof has exercised his right to require the Company
to repurchase this Security or such portion hereof, then in respect of this
Security until and including, but (unless the Company defaults in making the
payment due upon redemption or repurchase, as the case may be) not after, the
close of business on the Business Day immediately preceding the Redemption Date
or the Repurchase Date, as the case may be, to convert this Security (or any
portion of the principal amount hereof that is an integral multiple of
U.S.$1,000, provided that the unconverted portion of such principal amount is
U.S.$1,000

                                     -28-
<PAGE>

or any integral multiple of U.S.$1,000 in excess thereof) into fully paid and
nonassessable shares of Common Stock of the Company at an initial Conversion
Rate of 24.9389 (or at the current adjusted Conversion Rate if an adjustment has
been made as provided in the Indenture) by surrender of this Security, duly
endorsed or assigned to the Company or in blank and, in case such surrender
shall be made during the period from the close of business on any Regular Record
Date next preceding any Interest Payment Date to the opening of business on such
Interest Payment Date (except if this Security has been called for redemption on
a Redemption Date or is repurchasable on a Repurchase Date, with the consequence
that the conversion right of such Security would terminate between such Regular
Record Date and the close of business on such Interest Payment Date), also
accompanied by payment in New York Clearing House or other funds acceptable to
the Company of an amount equal to the interest payable on such Interest Payment
Date on the principal amount of this Security then being converted, and also the
conversion notice hereon duly executed, to the Company at the Corporate Trust
Office of the Trustee, or at such other office or agency of the Company, subject
to any laws or regulations applicable thereto and subject to the right of the
Company to terminate the appointment of any Conversion Agent (as defined below)
as may be designated by it for such purpose in the State of Minnesota, County of
Ramsey, City of St. Paul, or at such other offices or agencies as the Company
may designate (each a "Conversion Agent"), provided, further, that in case
surrender of this Security for conversion shall be made during the period from
the close of business on any Regular Record Date next preceding any Interest
Payment Date to the opening of business on such Interest Payment Date and if
this Security or portion hereof has been called for redemption on a Redemption
Date or is repurchasable on a Repurchase Date, with the consequence that the
conversion right of such Security would terminate between such Regular Record
Date and the close of business on such Interest Payment Date, then the Holder of
this Security will be entitled to receive the interest accruing hereon from the
Interest Payment Date next preceding the date of such conversion to such
succeeding Interest Payment Date and shall not be required to pay such interest
upon surrender of this Security for conversion. Subject to the provisions of the
preceding sentence and, in the case of a conversion after the close of business
on the Regular Record Date next preceding any Interest Payment Date and on or
before the close of business on such Interest Payment Date, to the right of the
Holder of this Security (or any Predecessor Security of record as of such
Regular Record Date) to receive the related installment of

                                     -29-
<PAGE>

interest to the extent and under the circumstances provided in the Indenture, no
cash payment or adjustment is to be made on conversion for interest accrued
hereon from the Interest Payment Date next preceding the day of conversion, or
for dividends on the Common Stock issued on conversion hereof. The Company shall
thereafter deliver to the Holder the fixed number of shares of Common Stock
(together with any cash adjustment, as provided in the Indenture) into which
this Security is convertible and such delivery will be deemed to satisfy the
Company's obligation to pay the principal amount of this Security. No fractions
of shares or scrip representing fractions of shares will be issued on
conversion, but instead of any fractional interest (calculated to the nearest
1/100th of a share) the Company shall pay a cash adjustment as provided in the
Indenture. The Conversion Rate is subject to adjustment as provided in the
Indenture. In addition, the Indenture provides that in case of certain
consolidations or mergers to which the Company is a party or the conveyance,
transfer, sale or lease of all or substantially all of the property and assets
of the Company, the Indenture shall be amended, without the consent of any
Holders of Securities, so that this Security, if then Outstanding, will be
convertible thereafter, during the period this Security shall be convertible as
specified above, only into the kind and amount of securities, cash and other
property receivable upon such consolidation, merger, conveyance, transfer, sale
or lease by a holder of the number of shares of Common Stock of the Company into
which this Security could have been converted immediately prior to such
consolidation, merger, conveyance, transfer, sale or lease (assuming such holder
of Common Stock is not a Constituent Person, failed to exercise any rights of
election and received per share the kind and amount received per share by a
plurality of Non-electing Shares). No adjustment in the Conversion Rate will be
made until such adjustment would require an increase or decrease of at least one
percent of such rate, provided that any adjustment that would otherwise be made
will be carried forward and taken into account in the computation of any
subsequent adjustment.

          Subject to certain limitations in the Indenture, at any time when the
Company is not subject to Section 13 or 15(d) of the United States Securities
Exchange Act of 1934, as amended, upon the request of a Holder of a Security or
the holder of shares of Common Stock issued upon conversion thereof, the Company
will promptly furnish or cause to be furnished Rule 144A Information (as defined
below) to such Holder of Securities or such holder of shares of Common Stock
issued upon conversion of Securities, or to a prospective purchaser of any such

                                     -30-
<PAGE>

security designated by any such Holder or holder, as the case may be, to the
extent required to permit compliance by such Holder or holder with Rule 144A
under the Securities Act of 1933, as amended (the "Securities Act"), in
connection with the resale of any such security. "Rule 144A Information" shall
be such information as is specified pursuant to Rule 144A(d)(4) under the
Securities Act (or any successor provision thereto).

          The Holder of this Security [if this Security is a Global Security,
then insert-- (including any Person that has a beneficial interest in this
Security)] and the Common Stock issuable upon conversion hereof is entitled to
the benefits of a Registration Rights Agreement, dated as of June 11, 2001 (the
"Registration Rights Agreement"), executed by the Company. Pursuant to the
Registration Rights Agreement, the Company has agreed for the benefit of the
Holders from time to time of Registered Securities and the Common Stock issuable
upon conversion thereof, in each case, that are Registrable Securities, at the
Company's expense, (a) to file within 90 days after the first date of original
issuance of the Securities, a shelf registration statement (the "Shelf
Registration Statement") with the Commission with respect to resales of the
Registrable Securities, (b) thereafter to use its best efforts to cause such
Shelf Registration Statement to be declared effective by the Commission within
180 days after the first date of original issuance of the Securities, and (c) to
use its reasonable efforts to maintain such Shelf Registration Statement
continuously effective under the Securities Act until a period of the two years
from the date of the effectiveness of the Shelf Registration Statement or, if
earlier, until (A) there are no outstanding Registrable Securities registered
under the Shelf Registration Statement or (B) the expiration of the period
referred to in Rule 144(k) (or any successor provision thereto) under the
Securities Act with respect to all Registrable Securities held by Persons that
are not Affiliates of the Company.

          Section 2(a) of the Registration Rights Agreement provides that, upon
written notice to each Holder of a Registrable Security, the Company may
postpone having the Shelf Registration Statement declared effective as required
by Section 2(a) of the Registration Rights Agreement for a reasonable time
specified in the notice but not exceeding 90 days if the Company is in
possession of material non-public information the disclosure of which would have
a material adverse effect on the business, operations, prospects, condition
(financial or otherwise) of the Company and its subsidiaries, taken as a

                                     -31-
<PAGE>

whole. Notwithstanding any postponement pursuant to Section 2(a) of the
Registration Rights Agreement, if (i) on or prior to 90 days following the date
of original issuance of the Registrable Securities, a Shelf Registration
Statement has not been filed with the Commission, or (ii) on or prior to the
180th day following the date of original issuance of the Registrable Securities,
such Shelf Registration Statement is not declared effective (each, a
"Registration Default"), additional interest ("Liquidated Damages") will accrue
on this Security from and including the day following such Registration Default
to but excluding the day on which such Registration Default has been cured or,
if earlier, the last day upon which the Shelf Registration Statement is required
to be kept effective. See (S) 7(a) of Registration Rights. Liquidated Damages
will be paid semi-annually in arrears, with the first semi-annual payment due on
the first interest payment date in respect of the Registrable Securities
following the date on which such Liquidated Damages begin to accrue, and will
accrue at a rate per annum equal to an additional one-quarter of one percent
(.25%) of the principal amount of the Registrable Securities to and including
the 90th day following such Registration Default and at a rate per annum equal
to one-half of one percent (.50%) thereof from and after the 91st day following
such Registration Default. In the event that the Shelf Registration Statement
ceases to be effective prior to the second annual anniversary of the initial
effective date of the Shelf Registration Statement or such earlier date as is
provided in the Registration Rights Agreement for a period in excess of 45 days,
whether or not consecutive, during any 90-day period or more than 90 days,
whether or not consecutive, during any 12-month period, then the interest rate
borne by the Registrable Securities shall increase by an additional one-half of
one percent (.50%) per annum from the 46th day of the 90-day period or the 91st
day of the applicable 12-month period such Shelf Registration Statement ceases
to be effective to but excluding the day on which the Shelf Registration
Statement again becomes effective or, if earlier, the last day upon which the
Shelf Registration Statement is required to be kept effective.

          Whenever in this Security there is a reference, in any context, to the
payment of the principal of, premium, if any, or interest on, or in respect of,
any Security such mention shall be deemed to include mention of the payment of
Liquidated Damages payable as described in the preceding paragraph to the extent
that, in such context, Liquidated Damages are, were or would be payable in
respect of this Security pursuant to such paragraph, and an express mention of
the payment of Liquidated

                                     -32-
<PAGE>

Damages (if applicable) in any provisions of this Security shall not be
construed as excluding Liquidated Damages in those provisions of this Security
where such express mention is not made.

          If the Holder of this Security [if this Security is a Global Security,
then insert-- (including any Person that has a beneficial interest in this
Security)] elects to sell this Security pursuant to the Shelf Registration
Statement then, by its acceptance hereof, such Holder of this Security agrees to
be bound by the terms of the Registration Rights Agreement relating to the
Registrable Securities which are the subject of such election.

          If a Change in Control occurs, the Holder of this Security, at the
Holder's option, shall have the right, in accordance with the provisions of the
Indenture, to require the Company to repurchase this Security (or any portion of
the principal amount hereof that is equal to U.S.$5,000 or any greater integral
multiple of U.S.$1,000) for cash at a Repurchase Price equal to 100% of the
principal amount thereof plus interest accrued to the Repurchase Date. At the
option of the Company, the Repurchase Price may be paid in cash or, subject to
the conditions provided in the Indenture, by delivery of shares of Common Stock
having a fair market value equal to the Repurchase Price. For purposes of this
paragraph, the fair market value of shares of Common Stock shall be determined
by the Company and shall be equal to 95% of the average of the Closing Price Per
Share for the five consecutive Trading Days immediately preceding and including
the third Trading Day prior to the Repurchase Date. Whenever in this Security
there is a reference, in any context, to the principal of any Security as of any
time, such reference shall be deemed to include reference to the Repurchase
Price payable in respect of such Security to the extent that such Repurchase
Price is, was or would be so payable at such time, and express mention of the
Repurchase Price in any provision of this Security shall not be construed as
excluding the Repurchase Price so payable in those provisions of this Security
when such express mention is not made; provided, however, that, for the purposes
                                       --------  -------
of the paragraph below concerning the consequences of an Event of Default, such
reference shall be deemed to include reference to the Repurchase Price only to
the extent the Repurchase Price is payable in cash.

          The Securities shall be "Designated Senior Debt" for purposes of the
Indenture, dated as of February 24, 2000, between the Company and Firstar Bank,
N.A., as trustee, with

                                     -33-
<PAGE>

respect to the Company's 5.00% Convertible Subordinated Notes due March 1, 2007
(the "Previous Indenture") and for purposes of any similar indenture, loan
agreement or other applicable instrument respecting the issuance, after the date
hereof, of other subordinated debt of the Company (the "Other Subordinated
Instruments"). For purposes of giving payment blockage notices under Section
12.2 of the Previous Indenture, and (where applicable) giving similar notices
under the Other Subordinated Instruments, the Trustee or the holders of at least
25% in principal amount of the Outstanding Securities are each authorized to
give such notices, whenever the conditions permitting such notices are met.

          [The following paragraph shall appear in each Registered Security that
is not a Global Security:

          In the event of redemption, repurchase or conversion of this Security
in part only, a new Registered Security or Registered Securities for the
unredeemed, unrepurchased or unconverted portion hereof will be issued in the
name of the Holder hereof.]

          [The following paragraph shall appear in each Global Security:

          In the event of a deposit or withdrawal of an interest in this
Security, including an exchange, transfer, redemption, repurchase or conversion
of this Security in part only, the Trustee, as custodian of the Depositary,
shall make an adjustment on its records to reflect such deposit or withdrawal in
accordance with the Applicable Procedures.]

          If an Event of Default shall occur and be continuing, the principal of
all the Securities, together with accrued interest to the date of declaration,
may be declared due and payable in the manner and with the effect provided in
the Indenture. Upon payment (i) of the amount of principal so declared due and
payable, together with accrued interest to the date of declaration, and (ii) of
interest on any overdue principal and, to the extent permitted by applicable
law, overdue interest, all of the Company's obligations in respect of the
payment of the principal of and interest on the Securities shall terminate.

          The Indenture permits, with certain exceptions as therein provided,
the amendment thereof and the modification of the rights and obligations of the
Company and the rights of the Holders of the Securities under the Indenture at
any time by the

                                     -34-
<PAGE>

Company and the Trustee with the written consent of the Holders of a majority in
principal amount of the Securities at the time Outstanding. The Indenture also
contains provisions permitting the Holders of specified percentages in principal
amount of the Securities at the time Outstanding, on behalf of the Holders of
all the Securities, to waive compliance by the Company with certain provisions
of the Indenture and certain past defaults under the Indenture and their
consequences. Any such consent or waiver by the Holder of this Security shall be
conclusive and binding upon such Holder and upon all future Holders of this
Security and of any Security issued in exchange herefor or in lieu hereof,
whether or not notation of such consent or waiver is made upon this Security or
such other Security.

          As provided in and subject to the provisions of the Indenture, the
Holder of this Security shall not have the right to institute any proceeding
with respect to the Indenture or for the appointment of a receiver or trustee or
for any other remedy thereunder, unless such Holder shall have previously given
the Trustee written notice of a continuing Event of Default, the Holders of not
less than 25% in principal amount of the Outstanding Securities shall have made
written request to the Trustee to institute proceedings in respect of such Event
of Default as Trustee and offered the Trustee reasonable indemnity, and shall
have failed to institute any such proceeding, for 60 days after receipt of such
notice, request and offer of indemnity. The foregoing shall not apply to any
suit instituted by the Holder of this Security for the enforcement of any
payment of principal hereof, premium, if any, or interest hereon (including
Liquidated Damages) on or after the respective due dates expressed herein or for
the enforcement of the right to convert this Security as provided in the
Indenture.

          No reference herein to the Indenture and no provision of this Security
or of the Indenture shall alter or impair the obligation of the Company, which
is absolute and unconditional, to pay the principal of, premium, if any, and
interest on (including Liquidated Damages) this Security at the times, places
and rate, and in the coin or currency, herein prescribed or to convert this
Security as provided in the Indenture.

          As provided in the Indenture and subject to certain limitations
therein set forth, the transfer of Registered Securities is registrable on the
Security Register upon surrender of a Registered Security for registration of
transfer at the Corporate Trust Office of the Trustee or at such other office or
agency of the Company as may be designated by it for such purpose in the State
of Minnesota, County of Ramsey, City

                                     -35-
<PAGE>

of St. Paul, or at such other offices or agencies as the Company may designate,
duly endorsed by, or accompanied by a written instrument of transfer in form
satisfactory to the Company and the Security Registrar duly executed by, the
Holder thereof or his attorney duly authorized in writing, and thereupon one or
more new Registered Securities, of authorized denominations and for the same
aggregate principal amount, will be issued to the designated transferee or
transferees by the Registrar. No service charge shall be made for any such
registration of transfer or exchange, but the Company may require payment of a
sum sufficient to recover any tax or other governmental charge payable in
connection therewith.

          Prior to due presentation of a Registered Security for registration of
transfer, the Company, the Trustee and any agent of the Company or the Trustee
may treat the Person in whose name such Registered Security is registered as the
owner thereof for all purposes, whether or not such Security be overdue, and
neither the Company, the Trustee nor any such agent shall be affected by notice
to the contrary.

          Interest on the Securities (including any Liquidated Damages) shall be
computed on the basis of a 360-day year of twelve 30-day months.

          The Indenture and this Security shall be governed by and construed in
accordance with the laws of the State of New York, United States of America,
without regard to the conflicts of laws principles thereof.

          All terms used in this Security which are defined in the Indenture
shall have the meanings assigned to them in the Indenture.

                   ELECTION OF HOLDER TO REQUIRE REPURCHASE

          (1)  Pursuant to Section 12.1 of the Indenture, the undersigned hereby
                           ------------
elects to have this Security repurchased by the Company.

          (2)  The undersigned hereby directs the Trustee or the Company to pay
it or _________________ an amount in cash or, at the Company's election, Common
Stock valued as set forth in the Indenture, equal to 100% of the principal
amount to be repurchased (as set forth below), plus interest accrued to the
Repurchase Date, as provided in the Indenture.

                                     -36-
<PAGE>

                                                  Dated: _______________________


                                                         _______________________
                                                                Signature


                                                         _______________________
                                                          Signature Guaranteed

Principal amount to be repurchased
(must be equal to U.S. $5,000 or any
greater integral multiple of U.S.$1,000):

Remaining principal amount following such repurchase:

                            ______________________

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.

SECTION 2.3    Form of Certificate of Authentication.
               -------------------------------------

          The Trustee's certificates of authentication shall be in substantially
the following form:

Dated:  [Date of Authentication]

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

                              ______________________________
                                as Trustee


                              By:___________________________
                                    Authorized Signatory

SECTION 2.4    Form of Conversion Notice.
               -------------------------

                               CONVERSION NOTICE

          The undersigned Holder of this Security hereby irrevocably exercises
the option to convert this Security, or any portion of the principal amount
hereof (which is an integral multiple of U.S.$1,000) below designated, into
shares of Common Stock in accordance with the terms of the Indenture referred

                                     -37-
<PAGE>

to in this Security, and directs that such shares, together with a check in
payment for any fractional share and any Securities representing any unconverted
principal amount hereof, be delivered to and be registered in the name of the
undersigned unless a different name has been indicated below. If shares of
Common Stock or Securities are to be registered in the name of a Person other
than the undersigned, the undersigned will pay all transfer taxes payable with
respect thereto. Any amount required to be paid by the undersigned on account of
interest accompanies this Security.

Dated: _______________________          __________________________
                                                Signature

If shares or Registered                 If only a portion of the
Securities are to be registered         Securities is to be converted,
in the name of a Person other           please indicate:
than the Holder, please print
such Person's name and address:
                                        1.   Principal amount to be converted:

_________________________
           Name                         U.S.$___________

                                        (any integral multiple of U.S.$1,000)
_________________________
          Address                       2.   Principal amount and denomination
                                             of Registered Securities
                                             representing unconverted principal
                                             amount to be issued:
_________________________
Social Security or other Taxpayer       Amount: U.S.$________
Identification Number, if any

                                        Denominations:
                                        U.S.$______
                                        (any integral multiple of U.S.$1,000)

                                             [Signature Guaranteed]

_________________________

                                 ARTICLE THREE

                                     -38-
<PAGE>

                                 ARTICLE THREE

                                THE SECURITIES

SECTION 3.1    Title and Terms.
               ---------------

          The aggregate principal amount of Securities which may be
authenticated and delivered under this Indenture is limited to U.S.$300,000,000,
except for Securities authenticated and delivered in exchange for, or in lieu
of, other Securities pursuant to Section 3.4, 3.5, 3.6, 8.5, 10.8, 11.2 or
                                 -----------------------------------------
12.3(e).
-------

          The Securities shall be known and designated as the "4.50% Convertible
Senior Notes due June 15, 2006" of the Company. Their Stated Maturity shall be
June 15, 2006 and they shall bear interest on their principal amount from June
11, 2001, payable semi-annually in arrears on June 15 and December 15 in each
year, commencing December 15, 2001, at the rate of 4.50% per annum until the
principal thereof is due and at the rate of 4.50% per annum on any overdue
principal and, to the extent permitted by law, on any overdue interest;
provided, however, that payments shall only be made on Business Days as provided
--------  -------
in Section 1.12.
   ------------

          The principal of, premium, if any, and interest on the Securities
shall be payable as provided in the form of Securities set forth in Section 2.2,
                                                                    -----------
and the Repurchase Price, whether payable in cash or in shares of Common Stock,
shall be payable at such places as are identified in the Company Notice given
pursuant to Section 12.3 (any city in which any Paying Agent is located being
            ------------
herein called a "Place of Payment").

          The Registrable Securities are entitled to the benefits of a
Registration Rights Agreement as provided by Sections 2.2 and 9.11. The
Securities are entitled to the payment of Liquidated Damages and additional
interest as provided by Section 9.11.
                        ------------

          The Securities shall be redeemable at the option of the Company, as
provided in Article Ten and in the form of Securities set forth in Section 2.2.
            -----------                                            -----------

          The Securities shall be convertible as provided in Article Eleven
                                                             --------------
(any city in which any Conversion Agent is located being herein called a "Place
of Conversion").

                                     -39-
<PAGE>

          The Securities shall be subject to repurchase by the Company at the
option of the Holders as provided in Article Twelve.
                                     --------------

          The Securities shall be "Designated Senior Debt" for purposes of the
Indenture, dated as of February 24, 2000, between the Company and Firstar Bank,
N.A., as trustee, with respect to the Company's 5.00% Convertible Subordinated
Notes due March 1, 2007 (the "Previous Indenture") and for purposes of any
similar indenture, loan agreement or other applicable instrument respecting the
issuance, after the date hereof, of other subordinated debt of the Company (the
"Other Subordinated Instruments"). For purposes of giving payment blockage
notices under Section 12.2 of the Previous Indenture, and (where applicable)
giving similar notices under the Other Subordinated Instruments, the Trustee or
the holders of at least 25% in principal amount of the Outstanding Securities
are each authorized to give such notices, whenever the conditions permitting
such notices are met.

SECTION 3.2    Denominations.
               -------------

          The Securities shall be issuable only in registered form, without
coupons, in denominations of U.S.$1,000 and integral multiples thereof.

SECTION 3.3    Execution, Authentication, Delivery and Dating.
               ----------------------------------------------

          The Securities shall be executed on behalf of the Company by its
Chairman of the Board, its Vice Chairman of the Board, its Chief Executive
Officer, its President or one of its Vice Presidents, under a facsimile of its
corporate seal reproduced thereon attested by its Secretary or one of its
Assistant Secretaries. Any such signature may be manual or facsimile.

          Securities bearing the manual or facsimile signature of individuals
who were at any time the proper officers of the Company shall bind the Company,
notwithstanding that such individuals or any of them have ceased to hold such
offices prior to the authentication and delivery of such Securities or did not
hold such offices at the date of such Securities.

          At any time and from time to time after the execution and delivery of
this Indenture, the Company may deliver Securities executed by the Company to
the Trustee or to its order for authentication, together with a Company Order
for the authentication and delivery of such Securities, and the Trustee

                                     -40-
<PAGE>

in accordance with such Company Order shall authenticate and make available for
delivery such Securities as in this Indenture provided and not otherwise.

          Each Security shall be dated the date of its authentication.

          No Security shall be entitled to any benefit under this Indenture or
be valid or obligatory for any purpose unless there appears on such Security a
certificate of authentication substantially in the form provided for herein
executed by the Trustee by manual signature of an authorized signatory, and such
certificate upon any Security shall be conclusive evidence, and the only
evidence, that such Security has been duly authenticated and delivered
hereunder.

SECTION 3.4         Global Securities; Non-Global Securities.
                    ----------------------------------------

     (A)  Global Securities

          (a)  Each Global Security authenticated under this Indenture shall be
registered in the name of the Depositary designated by the Company for such
Global Security or a nominee thereof and delivered to such Depositary or a
nominee thereof or custodian therefor, and each such Global Security shall
constitute a single Security for all purposes of this Indenture.

          (b)  Notwithstanding any other provision in this Indenture, no Global
Security may be exchanged in whole or in part for Securities registered, and no
transfer of a Global Security in whole or in part may be registered, in the name
of any Person other than the Depositary for such Global Security or a nominee
thereof unless (i) such Depositary (A) has notified the Company that it is
unwilling or unable to continue as Depositary for such Global Security or (B)
has ceased to be a clearing agency registered as such under the Exchange Act or
announces an intention permanently to cease business or does in fact do so or
(ii) there shall have occurred and be continuing an Event of Default with
respect to such Global Security.

          (c)  If any Global Security is to be exchanged for other Securities or
canceled in whole, it shall be surrendered by or on behalf of the Depositary or
its nominee to the Trustee, as Security Registrar, for exchange or cancellation,
as provided in this Article Three.  If any Global Security is to be exchanged
                    -------------
for other Securities or cancelled in part, or if another Security is to be
exchanged in whole or in part for a beneficial interest in any Global Security,
in each case, as

                                     -41-
<PAGE>

provided in Section 3.5, then either (i) such Global Security shall be so
            -----------
surrendered for exchange or cancellation, as provided in this Article Three, or
                                                              -------------
(ii) the principal amount thereof shall be reduced or increased by an amount
equal to the portion thereof to be so exchanged or cancelled, or equal to the
principal amount of such other Security to be so exchanged for a beneficial
interest therein, as the case may be, by means of an appropriate adjustment made
on the records of the Trustee, as Security Registrar, whereupon the Trustee, in
accordance with the Applicable Procedures, shall instruct the Depositary or its
authorized representative to make a corresponding adjustment to its records.
Upon any such surrender or adjustment of a Global Security, the Trustee shall,
subject to Section 3.5(c) and as otherwise provided in this Article Three,
           -------------                                    -------------
authenticate and make available for delivery any Securities issuable in exchange
for such Global Security (or any portion thereof) to or upon the order of, and
registered in such names as may be directed by, the Depositary or its authorized
representative. Upon the request of the Trustee in connection with the
occurrence of any of the events specified in the preceding paragraph, the
Company shall promptly make available to the Trustee a reasonable supply of
Securities that are not in the form of Global Securities. The Trustee shall be
entitled to rely upon any order, direction or request of the Depositary or its
authorized representative which is given or made pursuant to this Article Three
                                                                  -------------
if such order, direction or request is given or made in accordance with the
Applicable Procedures.


     (d)  Every Security authenticated and delivered upon registration of
transfer of, or in exchange for or in lieu of, a Global Security or any portion
thereof, whether pursuant to this Article Three or otherwise, shall be
                                  -------------
authenticated and delivered in the form of, and shall be, a registered Global
Security, unless such Security is registered in the name of a Person other than
the Depositary for such Global Security or a nominee thereof, in which case such
Registered Security shall be authenticated and delivered in definitive, fully
registered form, without interest coupons.

     (e)  The Depositary or its nominee, as registered owner of a Global
Security, shall be the Holder of such Global Security for all purposes under the
Indenture and the Registered Securities, and owners of beneficial interests in a
Global Security shall hold such interests pursuant to the Applicable Procedures.
Accordingly, any such owner's beneficial interest in a Global Security will be
shown only on, and the transfer of such interest shall be effected only through,
records maintained

                                     -42-
<PAGE>

by the Depositary or its nominee or its Agent Members and such owners of
beneficial interests in a Global Security will not be considered the owners or
holders thereof.

     (B)  Non-Global Securities

          Pending the preparation of definitive Securities, the Company may
execute, and upon Company Order the Trustee shall authenticate and make
available for delivery, temporary Securities which are printed, lithographed,
typewritten, mimeographed or otherwise produced, in any authorized denomination,
substantially of the tenor of the definitive Registered Securities in lieu of
which they are issued and with such appropriate insertions, omissions,
substitutions and other variations as the officers executing such Registered
Securities may determine, as evidenced by their execution of such Securities.

          If temporary Securities are issued, the Company will cause definitive
Securities to be prepared without unreasonable delay.  After the preparation of
definitive Securities, the temporary Securities shall be exchangeable for
definitive Securities upon surrender of the temporary Securities at any office
or agency of the Company designated pursuant to Section 9.2, without charge to
                                                -----------
the Holder.  Upon surrender for cancellation of any one or more temporary
Securities the Company shall execute and the Trustee shall authenticate and make
available for delivery in exchange therefor a like principal amount of
definitive Securities of authorized denominations.  Until so exchanged the
temporary Securities shall in all respects be entitled to the same benefits
under this Indenture as definitive Securities.

SECTION 3.5    Registration, Registration of Transfer and Exchange;
               ---------------------------------------------------
               Restrictions on Transfer.
               ------------------------

          (a)  The Company shall cause to be kept at the Corporate Trust Office
of the Trustee a register (the register maintained in such office and in any
other office or agency of the Company designated pursuant to Section 9.2 being
                                                             -----------
herein sometimes collectively referred to as the "Security Register") in which,
subject to such reasonable regulations as it may prescribe, the Company shall
provide for the registration of Registered Securities and of transfers of
Registered Securities. The Trustee is hereby appointed "Security Registrar" for
the purpose of registering Registered Securities and transfers and exchanges of
Registered Securities as herein provided.

                                     -43-
<PAGE>

          Upon surrender for registration of transfer of any Security at an
office or agency of the Company designated pursuant to Section 9.2 for such
                                                       -----------
purpose, the Company shall execute, and the Trustee shall authenticate and
deliver, in the name of the designated transferee or transferees, one or more
new Securities of any authorized denominations and of a like aggregate principal
amount and bearing such restrictive legends as may be required by this
Indenture.

          At the option of the Holder, and subject to the other provisions of
this Section 3.5, Securities may be exchanged for other Securities of any
     -----------
authorized denomination and of a like aggregate principal amount, upon surrender
of the Securities to be exchanged at any such office or agency.  Whenever any
Securities are so surrendered for exchange, and subject to the other provisions
of this Section 3.5, the Company shall execute, and the Trustee shall
        -----------
authenticate and make available for delivery, the Securities which the Holder
making the exchange is entitled to receive.  Every Security presented or
surrendered for registration of transfer or for exchange shall (if so required
by the Company or the Security Registrar) be duly endorsed, or be accompanied by
a written instrument of transfer in form satisfactory to the Company and the
Security Registrar duly executed, by the Holder thereof or his attorney duly
authorized in writing.

          All Securities issued upon any registration of transfer or exchange of
Securities shall be the valid obligations of the Company, evidencing the same
debt, and subject to the other provisions of this Section 3.5, entitled to the
                                                  -----------
same benefits under this Indenture, as the Securities surrendered upon such
registration of transfer or exchange.

          No service charge shall be made for any registration of transfer or
exchange of Securities except as provided in Section 3.6, but the Company may
                                             -----------
require payment of a sum sufficient to cover any tax or other governmental
charge that may be imposed in connection with any registration of transfer or
exchange of Securities, other than exchanges pursuant to Section 3.4, 8.5, 10.8,
                                                         -----------------------
11.2 or 12.3 (other than where the shares of Common Stock are to be issued or
------------
delivered in a name other than that of the Holder of the Security) not involving
any transfer and other than any stamp and other duties, if any, which may be
imposed in connection with any such transfer or exchange by the United States or
any political subdivision thereof or therein, which shall be paid by the
Company.

                                     -44-
<PAGE>

          In the event of a redemption of the Securities, the Company will not
be required (a) to register the transfer of or exchange Securities for a period
of 15 days immediately preceding the date notice is given identifying the serial
numbers of the Securities called for such redemption or (b) to register the
transfer of or exchange any Security, or portion thereof, called for redemption.

          (b)  Securities Act Legends.  All Securities shall bear the applicable
Restricted Securities Legend subject to the following:

               (i)    subject to the following Clauses of this Section 3.5(b), a
                                                               -------------
     Security or any portion thereof which is exchanged, upon transfer or
     otherwise, for a Global Security or any portion thereof shall bear the
     Securities Act Legend borne by such Global Security while represented
     thereby;


               (ii)   subject to the following Clauses of this Section 3.5(b), a
                                                               --------------
     new Security which is not a Global Security and is issued in exchange for
     another Security (including a Global Security) or any portion thereof, upon
     transfer or otherwise, shall bear the Securities Act Legend borne by such
     other Security;

               (iii)  any Securities which are sold or otherwise disposed of
     pursuant to an effective registration statement under the Securities Act
     (including the Shelf Registration Statement), together with their Successor
     Securities shall not bear a Securities Act Legend; the Company shall inform
     the Trustee in writing of the effective date of any such registration
     statement registering the Securities under the Securities Act and shall
     notify the Trustee at any time when prospectuses may not be delivered with
     respect to Securities to be sold pursuant to such registration statement.
     The Trustee shall not be liable for any action taken or omitted to be taken
     by it in good faith in accordance with the aforementioned registration
     statement;

               (iv)   at any time after the Securities may be freely transferred
     without registration under the Securities Act or without being subject to
     transfer restrictions pursuant to the Securities Act, a new Security which
     does not bear a Securities Act Legend may be issued in exchange for or in
     lieu of a Security (other than a Global Security) or any portion thereof
     which bears such a legend if the Trustee has received an Unrestricted

                                     -45-
<PAGE>


     Securities Certificate, satisfactory to the Trustee and duly executed by
     the Holder of such legended Security or his attorney duly authorized in
     writing, and after such date and receipt of such certificate, the Trustee
     shall authenticate and make available for delivery such a new Security in
     exchange for or in lieu of such other Security as provided in this Article
                                                                        -------
     Three;
     -----

               (v) a new Security which does not bear a Securities Act Legend
     may be issued in exchange for or in lieu of a Security (other than a Global
     Security) or any portion thereof which bears such a legend if, in the
     Company's judgment, placing such a legend upon such new Security is not
     necessary to ensure compliance with the registration requirements of the
     Securities Act, and the Trustee, at the direction of the Company, shall
     authenticate and make available for delivery such a new Security as
     provided in this Article Three; and
                      -------------

               (vi) notwithstanding the foregoing provisions of this Section
                                                                     -------
     3.5(b), a Successor Security of a Security that does not bear a particular
     ------
     form of Securities Act Legend shall not bear such form of legend unless the
     Company has reasonable cause to believe that such Successor Security is a
     "restricted security" within the meaning of Rule 144, in which case the
     Trustee, at the direction of the Company, shall authenticate and make
     available for delivery a new Security bearing a Restricted Securities
     Legend in exchange for such Successor Security as provided in this Article
                                                                        -------
     Three.
     -----

          (c)  Neither the Trustee, the Paying Agent nor any of their agents
shall (1) have any duty to monitor compliance with or with respect to any
federal or state or other securities or tax laws or (2) have any duty to obtain
documentation on any transfers or exchanges other than as specifically required
hereunder.

SECTION 3.6    Mutilated, Destroyed, Lost or Stolen Securities.
               -----------------------------------------------

          If any mutilated Security is surrendered to the Trustee, the Company
shall execute and the Trustee shall authenticate and make available for delivery
in exchange therefor a new Security of like tenor and principal amount and
bearing a number not contemporaneously outstanding.

          If there be delivered to the Company and to the Trustee:

                                     -46-
<PAGE>

          (1)  evidence to their satisfaction of the destruction, loss or theft
     of any Security, and

          (2)  such security or indemnity as may be satisfactory to the Company
     and the Trustee to save each of them and any agent of either of them
     harmless,

then, in the absence of actual notice to the Company or the Trustee that such
Security has been acquired by a bona fide purchaser, the Company shall execute
and the Trustee shall authenticate and make available for delivery, in lieu of
any such destroyed, lost or stolen Security, a new Security of like tenor and
principal amount and 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, the Company in its discretion, but
subject to any conversion rights, may, instead of issuing a new Security, pay
such Security, upon satisfaction of the conditions set forth in the preceding
paragraph.

          Upon the issuance of any new Security under this Section 3.6, 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 (other than any
stamp and other duties, if any, which may be imposed in connection therewith by
the United States or any political subdivision thereof or therein, which shall
be paid by the Company) and any other expenses (including the fees and expenses
of the Trustee) connected therewith.

          Every new Security issued pursuant to this Section 3.6 in lieu of any
                                                     -----------
mutilated, destroyed, lost or stolen Security shall constitute an original
additional contractual obligation of the Company, whether or not the mutilated,
destroyed, lost or stolen Security shall be at any time enforceable by anyone,
and such new Security shall be entitled to all the benefits of this Indenture
equally and proportionately with any and all other Securities duly issued
hereunder.

          The provisions of this Section 3.6 are exclusive and shall preclude
                                 -----------
(to the extent lawful) all other rights and remedies of any Holder with respect
to the replacement or payment of mutilated, destroyed, lost or stolen
Securities.

                                     -47-
<PAGE>

SECTION 3.7    Payment of Interest; Interest Rights Preserved.
               ----------------------------------------------

          Interest on any Security which is payable, and is punctually paid or
duly provided for, on any Interest Payment Date shall be paid to the Person in
whose name that Security (or one or more Predecessor Securities) is registered
at the close of business on the Regular Record Date for such interest.

          Any interest on any Security which is payable, but is not punctually
paid or duly provided for, on any Interest Payment Date (herein called
"Defaulted Interest") shall forthwith cease to be payable to the Holder on the
relevant Regular Record Date by virtue of having been such Holder, and such
Defaulted Interest may be paid by the Company, at its election in each case, as
provided in Clause (1) or (2) below:

     (1)  The Company may elect to make payment of any Defaulted Interest to the
Persons in whose names the Securities (or their respective Predecessor
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, the date of the
proposed payment and the Special Record Date, 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 Clause
provided.  The Special Record Date for the payment of such Defaulted Interest
shall be not more than 15 days and not less than 10 days prior to the date of
the proposed payment and not less than 10 days after the receipt by the Trustee
of the notice of the proposed payment.  The Trustee, in the name and at the
expense of the Company, shall cause notice of the proposed payment of such
Defaulted Interest and the Special Record Date therefor to be mailed, first-
class postage prepaid, to each Holder at such Holder's address as it appears in
the Security Register, 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 (or their respective Predecessor
Securities) are registered at the close of business on such Special Record Date
and shall no longer be payable pursuant to the following Clause (2).

                                     -48-
<PAGE>

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

          Subject to the foregoing provisions of this Section and Section 3.5,
                                                                  -----------
each Security delivered under this Indenture upon registration of transfer of or
in exchange for or in lieu of any other Security shall carry the rights to
interest accrued and unpaid, and to accrue, which were carried by such other
Security.

          Interest on any Security which is converted in accordance with Section
                                                                         -------
11.2 during a Record Date Period shall be payable in accordance with the
----
provisions of Section 11.2.
              ------------

SECTION 3.8         Persons Deemed Owners.
                    ---------------------

          Prior to due presentment of a Security for registration of transfer,
the Company, the Trustee and any agent of the Company or the Trustee may treat
the Person in whose name such Security is registered as the owner of such
Security for the purpose of receiving payment of principal of, premium, if any,
and (subject to Section 3.7) interest on such Security and for all other
                -----------
purposes whatsoever, whether or not such Security be overdue, and neither the
Company, the Trustee nor any agent of the Company or the Trustee shall be
affected by notice to the contrary.

SECTION 3.9         Cancellation.
                    ------------

          All Securities surrendered for payment, redemption, repurchase,
registration of transfer or exchange or conversion shall, if surrendered to any
Person other than the Trustee, be delivered to the Trustee.  All Securities so
delivered to the Trustee shall be canceled promptly by the Trustee.  No
Securities shall be authenticated in lieu of or in exchange for any Securities
canceled as provided in this Section 3.9.  The Trustee shall dispose of all
                             -----------
canceled Securities in accordance with applicable law and its customary
practices in effect from time to time.

                                     -49-
<PAGE>

SECTION 3.10        Computation of Interest.
                    -----------------------

          Interest on the Securities (including any Liquidated Damages) shall be
computed on the basis of a 360-day year of twelve 30-day months.

SECTION 3.11        CUSIP Numbers.
                    -------------

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

                                 ARTICLE FOUR

                           SATISFACTION AND DISCHARGE


SECTION 4.1         Satisfaction and Discharge of Indenture.
                    ---------------------------------------

          This Indenture shall upon Company Request cease to be of further
effect (except as to any surviving rights of conversion, or registration of
transfer or exchange, or replacement of Securities herein expressly provided for
and any right to receive Liquidated Damages as provided in the form of
Securities set forth in Section 2.2 and the Company's obligations to the Trustee
                        -----------
pursuant to Section 6.7), and the Trustee, at the expense of the Company, shall
            -----------
execute proper instruments in form and substance satisfactory to the Trustee
acknowledging satisfaction and discharge of this Indenture, when

          (1)  either

               (A) all Securities theretofore authenticated and delivered (other
          than (i) Securities which have been destroyed, lost or stolen and
          which have been replaced

                                     -50-
<PAGE>

          or paid as provided in Section 3.6 and (ii) Securities for whose
                                 -----------
          payment money has theretofore been deposited in trust or segregated
          and held in trust by the Company and thereafter repaid to the Company
          or discharged from such trust, as provided in Section 9.3) have been
                                                        -----------
          delivered to the Trustee for cancellation; or

               (B)  all such Securities not theretofore delivered to the Trustee
          or its agent for cancellation (other than Securities referred to in
          clauses (i) and (ii) of clause (1)(A) above)

               (i)   become due and payable, or

               (ii)  will have become due and payable at their Stated Maturity
          within one year, or

               (iii) are to be called for redemption within one year under
          arrangements satisfactory to the Trustee for the giving of notice of
          redemption by the Trustee in the name, and at the expense, of the
          Company,

          and the Company, in the case of clause (i), (ii) or (iii) above, has
deposited or caused to be deposited with the Trustee as trust funds (immediately
available to the Holders in the case of clause (i)) in trust for the purpose an
amount sufficient to pay and discharge the entire indebtedness on such
Securities not theretofore delivered to the Trustee for cancellation, for
principal, premium, if any, and interest (including any Liquidated Damages) to
the date of such deposit (in the case of Securities which have become due and
payable) or to the Stated Maturity 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 6.7, the obligations of
                                                -----------
the Company to any Authenticating Agent under Section 6.12, the obligation of
                                              ------------
the Company to pay Liquidated Damages, if money shall have been

                                     -51-
<PAGE>

deposited with the Trustee pursuant to clause (1)(B) of this Section 4.1, the
                                                             -----------
obligations of the Trustee under Section 4.2 and the last paragraph of Section
                                 -----------                           -------
9.3 and the obligations of the Company and the Trustee under Section 3.5 and
---                                                          -----------
Article Eleven shall survive.
--------------

SECTION 4.2    Application of Trust Money.
               --------------------------

          Subject to the provisions of the last paragraph of Section 9.3, all
                                                             -----------
money deposited with the Trustee pursuant to Section 4.1 shall be held in trust
                                             -----------
and applied by it, in accordance with the provisions of the Securities and this
Indenture, to the payment, either directly or through any Paying Agent
(including the Company acting as its own Paying Agent), to the Persons entitled
thereto, of the principal, premium, if any, and interest for whose payment such
money has been deposited with the Trustee.

          All moneys deposited with the Trustee pursuant to Section 4.1 (and
                                                            -----------
held by it or any Paying Agent) for the payment of Securities subsequently
converted shall be returned to the Company upon Company Request.

                                 ARTICLE FIVE

                                    REMEDIES

SECTION 5.1    Events of Default.
               -----------------

          "Event of Default", wherever used herein, means any one of the
following events (whatever the reason for such Event of Default and whether it
shall be voluntary or involuntary or be effected by operation of law or pursuant
to any judgment, decree or order of any court or any order, rule or regulation
of any administrative or governmental body):

          (1)  default in the payment of the principal of or premium, if any, on
any Security at its Maturity; or

          (2)  default in the payment of any interest (including any Liquidated
Damages) upon any Security when it becomes due and payable, and continuance of
such default for a period of 30 days; or

          (3)  failure by the Company to give the Company notice in accordance
with Section 12.3; or
     ------------

                                     -52-
<PAGE>

          (4)  default in the performance, or breach, of any covenant or
warranty of the Company in this Indenture (other than a covenant or warranty a
default in the performance or breach of which is specifically dealt with
elsewhere in this Section), and continuance of such default or breach for a
period of 60 days after there has been given, by registered or certified mail,
to the Company by the Trustee or to the Company and the Trustee by the Holders
of at least 25% in principal amount of the Outstanding Securities, a written
notice specifying such default or breach and requiring it to be remedied and
stating that such notice is a "Notice of Default" hereunder;

          (5)  a default in the payment when due of the principal of, or
acceleration of, any indebtedness under any bond, debenture, note or other
evidence of indebtedness for money borrowed by the Company or any Subsidiary of
the Company or under any mortgage, indenture or instrument under which there may
be issued or by which there may be secured or evidenced any indebtedness for
money borrowed by the Company or any Subsidiary of the Company with a principal
amount then outstanding in excess of U.S.$10,000,000, whether such indebtedness
now exists or shall hereafter be created, if such indebtedness is not
discharged, or such acceleration is not rescinded or annulled, within a period
of 30 days after there shall have been given, by registered or certified mail,
to the Company by the Trustee or to the Company and the Trustee by the Holders
of at least 25% in principal amount of the Outstanding Securities a written
notice specifying such default and requiring the Company to cause such
indebtedness to be discharged or such acceleration to be rescinded or annulled
and stating that such notice is a "Notice of Default" hereunder; or

          (6)  the entry by a court having jurisdiction in the premises of (A) a
decree or order for relief in respect of the Company in an involuntary case or
proceeding under any applicable Federal or State bankruptcy, insolvency,
reorganization or other similar law or (B) a decree or order adjudging the
Company a bankrupt or insolvent, or approving as properly filed a petition
seeking reorganization, arrangement, adjustment or composition of or in respect
of the Company under any applicable Federal or State law, or appointing a
custodian, receiver, liquidator, assignee, trustee, sequestrator or other
similar official of the Company or of any substantial part of its property, or
ordering the winding up or liquidation of its affairs, and the continuance of
any such decree or order for

                                     -53-
<PAGE>

relief or any such other decree or order unstayed and in effect for a period of
60 consecutive days; or

          (7)  the commencement by the Company of a voluntary case or proceeding
under any applicable Federal or State bankruptcy, insolvency, reorganization or
other similar law or of any other case or proceeding to be adjudicated a
bankrupt or insolvent, or the consent by it to the entry of a decree or order
for relief in respect of the Company in an involuntary case or proceeding under
any applicable Federal or State bankruptcy, insolvency, reorganization or other
similar law or to the commencement of any bankruptcy or insolvency case or
proceeding against it, or the filing by it of a petition or answer or consent
seeking reorganization or similar relief under any applicable Federal or State
law, or the consent by it to the filing of such petition or to the appointment
of or taking possession by a custodian, receiver, liquidator, assignee, trustee,
sequestrator or other similar official of the Company or of any substantial part
of its property, or the making by it of an assignment for the benefit of
creditors, or the admission by it in writing of its inability to pay its debts
generally as they become due, or the taking of corporate action by the Company
in furtherance of any such action.

SECTION 5.2    Acceleration of Maturity; Rescission and Annulment.
               --------------------------------------------------

          If an Event of Default (other than an Event of Default specified in
Section 5.1(6) or 5.1(7)) occurs and is continuing, then in every such case the
--------------    ------
Trustee or the Holders of not less than 25% in principal amount of the
Outstanding Securities may declare the principal of all the Securities to be due
and payable immediately, by a notice in writing to the Company (and to the
Trustee if given by the Holders), and upon any such declaration such principal
and all accrued interest thereon shall become immediately due and payable.  If
an Event of Default specified in Section 5.1(6) or 5.1(7) occurs, the principal
                                 --------------    ------
of, and accrued interest on, all the Securities shall ipso facto become
immediately due and payable without any declaration or other Act of the Holder
or any act on the part of the Trustee.

          At any time after such declaration of acceleration has been made and
before a judgment or decree for payment of the money due has been obtained by
the Trustee as hereinafter in this Article Five provided, the Holders of a
                                   ------------
majority in principal amount of the Outstanding Securities, by written

                                     -54-
<PAGE>

notice to the Company and the Trustee, may rescind and annul such declaration
and its consequences if

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

               (A)  all overdue interest (including any Liquidated Damages) on
          all Securities,

               (B)  the principal of and premium, if any, on any Securities
          which have become due otherwise than by such declaration of
          acceleration and any interest (including any Liquidated Damages)
          thereon at the rate borne by the Securities,

               (C)  to the extent permitted by applicable law, interest upon
          overdue interest at a rate of 4.50% per annum, and

               (D)  all sums paid or advanced by the Trustee hereunder and the
          reasonable compensation, expenses, disbursements and advances of the
          Trustee, its agents and its counsel;

and

          (2)  all Events of Default, other than the nonpayment of the principal
of, and any premium and interest on, Securities which have become due solely by
such declaration of acceleration, have been cured or waived as provided in
Section 5.13.
------------

          No rescission or annulment referred to above shall affect any
subsequent default or impair any right consequent thereon.

SECTION 5.3    Collection of Indebtedness and Suits for Enforcement by Trustee.
               ---------------------------------------------------------------

          The Company covenants that if

          (1)  default is made in the payment of any interest (including any
     Liquidated Damages) on any Security when it becomes due and payable and
     such default continues for a period of 30 days, or

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

                                     -55-
<PAGE>

the Company will upon demand of the Trustee pay to it, for the benefit of the
Holders of such Securities the whole amount then due and payable on such
Securities for principal and interest (including any Liquidated Damages) and
interest on any overdue principal and premium, if any, and, to the extent
permitted by applicable law, on any overdue interest (including any Liquidated
Damages), at a rate of 4.50% per annum, and in addition thereto, such further
amount as shall be sufficient to cover the reasonable costs and expenses of
collection, including the reasonable compensation, expenses, disbursements and
advances of the Trustee, its agents and its counsel.

          If the Company fails to pay such amounts forthwith upon such demand,
the Trustee, in its own name and as trustee of an express trust, may institute a
judicial proceeding for the collection of the sums so due and unpaid, may
prosecute such proceeding to judgment or final decree and may enforce the same
against the Company or any other obligor upon the Securities and collect the
moneys adjudged or decreed to be payable in the manner provided by law out of
the property of the Company or any other obligor upon the Securities, wherever
situated.

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

SECTION 5.4    Trustee May File Proofs of Claim.
               --------------------------------

          In case of the pendency of any receivership, insolvency, liquidation,
bankruptcy, reorganization, arrangement, adjustment, composition or other
judicial proceeding relative to the Company or any other obligor upon the
Securities or the property of the Company or of such other obligor or the
creditors of either, the Trustee (irrespective of whether the principal of, and
any interest on, the Securities shall then be due and payable as therein
expressed or by declaration or otherwise and irrespective of whether the Trustee
shall have made any demand on the Company for the payment of overdue principal
or interest) shall be entitled and empowered, by intervention in such proceeding
or otherwise,

          (1)  to file and prove a claim for the whole amount of principal,
     premium, if any, and interest (including any

                                     -56-
<PAGE>

     Liquidated Damages) owing and unpaid in respect of the Securities and take
     such other actions, including participating as a member, voting or
     otherwise, of any official committee of creditors appointed in such matter,
     and to file such other papers or documents, in each of the foregoing cases,
     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 its counsel) and
     of the Holders of Securities allowed in such judicial proceeding, and

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

and any custodian, receiver, assignee, trustee, liquidator, sequestrator or
other similar official in any such judicial proceeding is hereby authorized by
each Holder of Securities to make such payments to the Trustee and, in the event
that the Trustee shall consent to the making of such payments directly to the
Holders of Securities to pay to the Trustee any amount due to it for the
reasonable compensation, expenses, disbursements and advances of the Trustee,
its agents and its counsel and any other amounts due the Trustee under Section
                                                                       -------
6.7.
---

          Nothing herein contained shall be deemed to authorize the Trustee to
authorize or consent to or accept or adopt on behalf of any Holder of a Security
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 of a Security in any such proceeding;
provided, however, that the Trustee may, on behalf of such Holders, vote for the
--------  -------
election of a trustee in bankruptcy or similar official.

SECTION 5.5    Trustee May Enforce Claims Without Possession of Securities.
               -----------------------------------------------------------

          All rights of action and claims under this Indenture or the Securities
may be prosecuted and enforced by the Trustee without the possession of any of
the Securities or the production thereof in any proceeding relating thereto, and
any such proceeding instituted by the Trustee shall be brought in its own name
as trustee of an express trust, and any recovery of judgment shall, after
provision for the payment of the reasonable compensation, expenses,
disbursements and advances of the Trustee, its agents and its counsel, be for
the ratable

                                     -57-
<PAGE>

benefit of the Holders of the Securities in respect of which judgment has been
recovered.

SECTION 5.6    Application of Money Collected.
               ------------------------------

          Any money collected by the Trustee pursuant to this Article Five shall
                                                              ------------
be applied in the following order, at the date or dates fixed by the Trustee
and, in case of the distribution of such money on account of principal, premium,
if any, or interest, upon presentation of the Securities and the notation
thereon of the payment if only partially paid and upon surrender thereof if
fully paid:

          FIRST:  To the payment of all amounts due the Trustee under Section
                                                                      -------
     6.7;
     ---

          SECOND:  To the payment of the amounts then due and unpaid for
     principal of, premium, if any, or interest (including any Liquidated
     Damages) on, the Securities in respect of which or for the benefit of which
     such money has been collected, ratably, without preference or priority of
     any kind, according to the amounts due and payable on such Securities for
     principal, premium, if any, and interest (including any Liquidated
     Damages), respectively; and

          THIRD:  Any remaining amounts shall be repaid to the Company.

SECTION 5.7    Limitation on Suits.
               -------------------

          No Holder of any Security shall have any right to institute any
proceeding, judicial or otherwise, with respect to this Indenture, or for the
appointment of a receiver or trustee, or for any other remedy hereunder, unless:

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

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

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

                                     -58-
<PAGE>

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

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

SECTION 5.8    Unconditional Right of Holders to Receive
               -----------------------------------------
               Principal, Premium and Interest and to Convert.
               ----------------------------------------------

          Notwithstanding any other provision in this Indenture, the Holder of
any Security shall have the right, which is absolute and unconditional, to
receive payment of the principal of, premium, if any, and (subject to Section
                                                                      -------
3.7) interest (including any Liquidated Damages) on such Security on the
---
respective Stated Maturities expressed in such Security (or, in the case of
redemption or repurchase, on the Redemption Date or Repurchase Date, as the case
may be), and to convert such Security in accordance with Article Eleven, and to
                                                         --------------
institute suit for the enforcement of any such payment and right to convert, and
such rights shall not be impaired without the consent of such Holder.

SECTION 5.9    Restoration of Rights and Remedies.
               ----------------------------------

          If the Trustee or any Holder of a Security has instituted any
proceeding to enforce any right or remedy under this Indenture and such
proceeding has been discontinued or abandoned for any reason, or has been
determined adversely to the Trustee or to such Holder, then and in every such
case, subject to any determination in such proceeding, the Company, the Trustee
and the Holders of Securities shall be restored severally and respectively to
their former positions hereunder and thereafter all rights and remedies of the
Trustee and such Holders shall continue as though no such proceeding had been
instituted.

SECTION 5.10   Rights and Remedies Cumulative.
               ------------------------------

          Except as otherwise provided with respect to the replacement or
payment of mutilated, destroyed, lost or stolen Securities in the last paragraph
of Section 3.6, no right or
   -----------

                                     -59-
<PAGE>

remedy herein conferred upon or reserved to the Trustee or to the Holders of
Securities is intended to be exclusive of any other right or remedy, and every
right and remedy shall, to the extent permitted by law, be cumulative and in
addition to every other right and remedy given hereunder or now or hereafter
existing at law or in equity or otherwise. The assertion or employment of any
right or remedy hereunder, or otherwise, shall not prevent the concurrent
assertion or employment of any other appropriate right or remedy.

SECTION 5.11   Delay or Omission Not Waiver.
               ----------------------------

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

SECTION 5.12   Control by Holders of Securities.
               --------------------------------

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

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

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

SECTION 5.13   Waiver of Past Defaults.
               -----------------------

          The Holders, either (a) through the written consent of not less than a
majority in principal amount of the Outstanding Securities, or (b) by the
adoption of a resolution, at a meeting of Holders of the Outstanding Securities
at which a quorum is present, by the Holders of at least a majority in principal
amount of the Outstanding Securities represented at such meeting, may on behalf
of the Holders of all the Securities waive any past default hereunder and its
consequences, except a

                                     -60-
<PAGE>

default (1) in the payment of the principal of, premium, if any, or interest
(including any Liquidated Damages) on any Security, or (2) in respect of a
covenant or provision hereof which under Article Eight cannot be modified or
                                         -------------
amended without the consent of the Holder of each Outstanding Security affected.

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

SECTION 5.14   Undertaking for Costs.
               ---------------------

          All parties to this Indenture agree, and each Holder of any Security
by his acceptance thereof shall be deemed to have agreed, that any court may in
its discretion require, in any suit for the enforcement of any right or remedy
under this Indenture, or in any suit against the Trustee for any action taken,
suffered or omitted by it as Trustee, the filing by any party litigant in such
suit of an undertaking to pay the costs of such suit, and that such court may in
its discretion assess reasonable costs, including reasonable attorneys' fees and
expenses, against any party litigant in such suit, having due regard to the
merits and good faith of the claims or defenses made by such party litigant; but
the provisions of this Section 5.14 shall not apply to any suit instituted by
                       ------------
the Company, to any suit instituted by the Trustee, to any suit instituted by
any Holder, or group of Holders, holding in the aggregate more than 10% in
principal amount of the Outstanding Securities, or to any suit instituted by any
Holder of any Security for the enforcement of the payment of the principal of,
premium, if any, or interest (including any Liquidated Damages) on any Security
on or after the respective Stated Maturity or Maturities expressed in such
Security (or, in the case of redemption or repurchase, on or after the
Redemption Date or Repurchase Date, as the case may be) or for the enforcement
of the right to convert any Security in accordance with Article Eleven.
                                                        --------------

SECTION 5.15   Waiver of Stay, Usury or Extension Laws.
               ---------------------------------------

          The Company covenants (to the extent that it may lawfully do so) that
it will not at any time insist upon, or plead, or in any manner whatsoever claim
or take the benefit or advantage of, any stay, usury or extension law wherever
enacted, now or at any time hereafter in force, which may affect the covenants
or the performance of this Indenture; and the Company (to the extent that it may
lawfully do so) hereby expressly

                                     -61-
<PAGE>

waives all benefit or advantage of any such law and covenants that it will not
hinder, delay or impede by reason of such law 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.

                                  ARTICLE SIX

                                  THE TRUSTEE

SECTION 6.1    Certain Duties and Responsibilities.
               -----------------------------------

          (a)  Except during the continuance of an Event of Default,

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

          (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; but in
     the case of any such certificates or opinions which by any provision hereof
     are specifically required to be furnished to the Trustee, the Trustee shall
     be under a duty to examine the same to determine whether or not they
     conform to the requirements of this Indenture, but not to verify the
     contents thereof.

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

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

                                     -62-
<PAGE>

          (1)  this paragraph (c) shall not be construed to limit the effect of
     paragraph (a) of this Section;

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

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

          (4)  no provision of this Indenture shall require the Trustee to
     expend or risk its own funds or otherwise incur any financial liability in
     the performance of any of its duties hereunder, or in the exercise of any
     of its rights or powers, if it shall have reasonable grounds for believing
     that repayment of such funds or adequate indemnity against such risk or
     liability is not reasonably assured to it.

          (d)  Whether or not therein expressly so provided, every provision of
this Indenture relating to the conduct or affecting the liability of or
affording protection to the Trustee shall be subject to the provisions of this
Section.

SECTION 6.2    Notice of Defaults.
               ------------------

          Within 90 days after the occurrence of any default hereunder as to
which the Trustee has actually received written notice, the Trustee shall give
to all Holders of Securities, in the manner provided in Section 1.6, notice of
                                                        -----------
such default, unless such default shall have been cured or waived; provided,
                                                                   --------
however, that, except in the case of a default in the payment of the principal
-------
of, premium, if any, or interest on any Security the Trustee shall be protected
in withholding such notice if and so long as the board of directors, the
executive committee or a trust committee of directors or Responsible Officers of
the Trustee in good faith determine that the withholding of such notice is in
the interest of the Holders; and provided, further, that in the case of any
default of the character specified in Section 5.1(4), no such notice to Holders
                                      --------------
of Securities shall be given until at least 60 days after the occurrence
thereof.  For

                                     -63-
<PAGE>

the purpose of this Section, the term "default" means any event which is, or
after notice or lapse of time or both would become, an Event of Default.

SECTION 6.3    Certain Rights of Trustee.
               -------------------------

          Subject to the provisions of Section 6.1:
                                       -----------

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

          (2)  any request or direction of the Company mentioned herein shall be
     sufficiently evidenced by a Company Request or Company Order and any
     resolution of the Board of Directors shall be sufficiently evidenced by a
     Board Resolution;

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

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

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

          (6)  the Trustee shall not be bound to make any investigation into the
     facts or matters stated in any

                                     -64-
<PAGE>

     resolution, certificate, statement, instrument, opinion, report, notice,
     request, direction, consent, order, bond, debenture, note, coupon, other
     evidence of indebtedness or other paper or document, but the Trustee may
     make 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;
     and

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

SECTION 6.4    Not Responsible for Recitals or Issuance of Securities.
               ------------------------------------------------------

          The recitals contained herein and in the Securities (except the
Trustee's certificates of authentication) shall be taken as the statements of
the Company, and the Trustee assumes no responsibility for their correctness.
The Trustee makes no representations as to the validity or sufficiency of this
Indenture, of the Securities or of the Common Stock issuable upon the conversion
of the Securities.  The Trustee shall not be accountable for the use or
application by the Company of Securities or the proceeds thereof.

SECTION 6.5    May Hold Securities, Act as Trustee Under Other Indentures.
               ----------------------------------------------------------

          The Trustee, any Authenticating Agent, any Paying Agent, any
Conversion Agent or any other agent of the Company or the Trustee, in its
individual or any other capacity, may become the owner or pledgee of Securities
and may otherwise deal with the Company with the same rights it would have if it
were not Trustee, Authenticating Agent, Paying Agent, Conversion Agent or such
other agent.

          The Trustee may become and act as trustee under other indentures under
which other securities, or certificates of interest or participation in other
securities, of the Company are outstanding in the same manner as if it were not
Trustee hereunder.

                                     -65-
<PAGE>

SECTION 6.6    Money Held in Trust.
               -------------------

          Money held by the Trustee in trust hereunder need not be segregated
from other funds except to the extent required by law.  The Trustee shall be
under no liability for interest on any money received by it hereunder except as
otherwise agreed in writing with the Company.

SECTION 6.7    Compensation and Reimbursement.
               ------------------------------

          The Company agrees

          (1)  to pay to the Trustee from time to time such compensation as the
     Company and the Trustee shall from time to time agree in writing for all
     services rendered by it hereunder (which compensation shall not be limited
     by any provision of law in regard to the compensation of a trustee of an
     express trust);

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

          (3)  to indemnify the Trustee (and its directors, officers, employees
     and agents) for, and to hold it harmless against, any and all loss, damage,
     claim, liability or expense, including taxes (other than taxes based on the
     income of the Trustee), incurred without negligence or bad faith on its
     part, arising out of or in connection with the acceptance or administration
     of this trust, including the reasonable costs, expenses and reasonable
     attorneys' fees of defending itself against any claim or liability in
     connection with the exercise or performance of any of its powers or duties
     hereunder.

          When the Trustee incurs expenses or renders services in connection
with an Event of Default specified in Section 5.1(6) or Section 5.1(7), the
                                      --------------    --------------
expenses (including the reasonable charges of its counsel) and the compensation
for the services are intended to constitute expenses of the administration under
any applicable Federal or State bankruptcy, insolvency or other similar law.

                                     -66-
<PAGE>

          The Trustee shall have a lien prior to the Securities as to all
property and funds held by it hereunder for any amount owing it or any
predecessor Trustee pursuant to this Section 6.7, except with respect to funds
                                     -----------
held in trust for the benefit of the Holders of particular Securities.

          The provisions of this Section shall survive the termination of this
Indenture or the earlier resignation or removal of the Trustee.

SECTION 6.8    Corporate Trustee Required; Eligibility.
               ---------------------------------------

          There shall at all times be a Trustee hereunder which shall be a
Person that is eligible pursuant to the Trust Indenture Act to act as such,
having a combined capital and surplus (or for such purposes, the combined
capital and surplus of any parent holding company) of at least U.S.$25,000,000,
subject to supervision or examination by Federal or State authority, in good
standing and having an office or agent in the Borough of Manhattan, The City of
New York.  If such corporation publishes reports of condition at least annually,
pursuant to law or to the requirements of said supervising or examining
authority, then for the purposes of this Section, the combined capital and
surplus of such corporation shall be deemed to be its combined capital and
surplus as set forth in its most recent report of condition so published.  If at
any time the Trustee shall cease to be eligible in accordance with the
provisions of this Section, it shall resign immediately in the manner and with
the effect hereinafter specified in this Article and a successor shall be
appointed pursuant to Section 6.9.
                      -----------

SECTION 6.9    Resignation and Removal; Appointment of Successor.
               ------------------------------------------------

          (a)  No resignation or removal of the Trustee and no appointment of a
successor Trustee pursuant to this Article shall become effective until the
acceptance of appointment by the successor Trustee in accordance with the
applicable requirements of Section 6.10.
                           ------------

          (b)  The Trustee may resign at any time by giving written notice
thereof to the Company. If the instrument of acceptance by a successor Trustee
required by Section 6.10 shall not have been delivered to the Trustee within 30
            ------------
days after the giving of such notice of resignation, the resigning Trustee may
petition any court of competent jurisdiction for the appointment of a successor
Trustee.

                                     -67-
<PAGE>

          (c)  The Trustee may be removed at any time by Act of the Holders of a
majority in principal amount of the Outstanding Securities, delivered to the
Trustee and the Company. If the instrument of acceptance by a successor Trustee
required by Section 6.10 shall not have been delivered to the Trustee within 30
            ------------
days after the giving of such notice of removal, the removed Trustee may
petition any court of competent jurisdiction for the appointment of a successor
Trustee.

          (d)  If at any time:

          (1)  the Trustee shall cease to be eligible under Section 6.8 and
                                                            -----------
     shall fail to resign after written request therefor by the Company or by
     any Holder of a Security who has been a bona fide Holder of a Security for
     at least six months, or

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

then, in any such case (i) the Company by a Board Resolution may remove the
Trustee, or (ii) subject to Section 5.14, any Holder of a Security who has been
                            ------------
a bona fide Holder of a Security for at least six months may, on behalf of
himself and all others similarly situated, petition any court of competent
jurisdiction for the removal of the Trustee and the appointment of a successor
Trustee.

          (e)  If the Trustee shall resign, be removed or become incapable of
acting, or if a vacancy shall occur in the office of Trustee for any cause, the
Company, by a Board Resolution, shall promptly appoint a successor Trustee and
shall comply with the applicable requirements of this Section and Section 6.10.
                                                                  ------------
If, within one year after such resignation, removal or incapability, or
occurrence of such vacancy, a successor Trustee shall be appointed by Act of the
Holders of a majority in principal amount of the Outstanding Securities
delivered to the Company and the retiring Trustee, the successor Trustee so
appointed shall, forthwith upon its acceptance of such appointment in accordance
with the applicable requirements of Section 6.10, become the successor Trustee
                                    -------
and supersede the successor Trustee appointed by the Company. If no successor
Trustee shall have been so appointed by the Company or the Holders of Securities
and accepted appointment in the manner

                                     -68-
<PAGE>

required by this Section and Section 6.10, any Holder of a Security who has been
                             ------------
a bona fide Holder of a Security for at least six months may, on behalf of
himself and all others similarly situated, petition any court of competent
jurisdiction for the appointment of a successor Trustee.

          (f)  The Company shall give notice of each resignation and each
removal of the Trustee and each appointment of a successor Trustee to all
Holders of Securities in the manner provided in Section 1.6. Each notice shall
                                                -----------
include the name of the successor Trustee and the address of its Corporate
Trust Office.

SECTION 6.10   Acceptance of Appointment by Successor.
               --------------------------------------

          Every successor Trustee appointed hereunder shall execute, acknowledge
and deliver to the Company and to the retiring Trustee an instrument accepting
such appointment, and thereupon the resignation or removal of the retiring
Trustee shall become effective and such successor Trustee, without any further
act, deed or conveyance, shall become vested with all the rights, powers, trusts
and duties of the retiring Trustee; but, on the request of the Company or the
successor Trustee, such retiring Trustee shall, upon payment of its charges,
execute and deliver an instrument transferring to such successor Trustee all the
rights, powers and trusts of the retiring Trustee and shall duly assign,
transfer and deliver to such successor Trustee all property and money held by
such retiring Trustee hereunder.  Upon request of any such successor Trustee,
the Company shall execute any and all instruments for more fully and certainly
vesting in and confirming to such successor Trustee all such rights, powers and
trusts.

          No successor Trustee shall accept its appointment unless at the time
of such acceptance such successor Trustee shall be eligible under this Article.

SECTION 6.11   Merger, Conversion, Consolidation or Succession to Business.
               -----------------------------------------------------------

          Any corporation into which the Trustee may be merged or converted or
with which it may be consolidated, or any corporation resulting from any merger,
conversion or consolidation to which the Trustee shall be a party, or any
corporation succeeding to all or substantially all of the corporate trust
business of the Trustee, shall be the successor of the Trustee hereunder,
provided such corporation shall be otherwise eligible under this Article,
without the execution or

                                     -69-
<PAGE>

filing of any paper or any further act on the part of
any of the parties hereto.  In case any Securities shall have been
authenticated, but not delivered, by the Trustee then in office, any successor
by merger, conversion or consolidation to such authenticating Trustee may adopt
such authentication and deliver the Securities so authenticated with the same
effect as if such successor Trustee had itself authenticated such Securities.

SECTION 6.12   Authenticating Agents.
               ---------------------

          The Trustee may, with the consent of the Company, appoint an
Authenticating Agent or Agents acceptable to the Company with respect to the
Securities which shall be authorized to act on behalf of the Trustee to
authenticate Securities issued upon exchange or substitution pursuant to this
Indenture.

          Securities authenticated by an Authenticating Agent shall be entitled
to the benefits of this Indenture and shall be valid and obligatory for all
purposes as if authenticated by the Trustee hereunder, and every reference in
this Indenture to the authentication and delivery of Securities by the Trustee
or the Trustee's certificate of authentication shall be deemed to include
authentication and delivery on behalf of the Trustee by an Authenticating Agent
and a certificate of authentication executed on behalf of the Trustee by an
Authenticating Agent.  Each Authenticating Agent shall be subject to acceptance
by the Company and shall at all times be a corporation organized and doing
business under the laws of the United States of America, any State thereof or
the District of Columbia, authorized under such laws to act as Authenticating
Agent and subject to supervision or examination by government or other fiscal
authority.  If at any time an Authenticating Agent shall cease to be eligible in
accordance with the provisions of this Section 6.12, such Authenticating Agent
                                       ------------
shall resign immediately in the manner and with the effect specified in this
Section 6.12.
------------

          Any corporation into which an Authenticating Agent may be merged or
converted or with which it may be consolidated, or any corporation resulting
from any merger, conversion or consolidation to which such Authenticating Agent
shall be a party, or any corporation succeeding to the corporate agency or
corporate trust business of an Authenticating Agent, shall continue to be an
Authenticating Agent, provided such corporation shall be otherwise eligible
under this Section 6.12, without the execution or filing of any paper or any
           ------------
further act on the part of the Trustee or the Authenticating Agent.

                                     -70-
<PAGE>

          An Authenticating Agent may resign at any time by giving written
notice thereof to the Trustee and to the Company.  The Trustee may at any time
terminate the agency of an Authenticating Agent by giving written notice thereof
to such Authenticating Agent and to the Company.  Upon receiving such a notice
of resignation or upon such a termination, or in case at any time such
Authenticating Agent shall cease to be eligible in accordance with the
provisions of this Section 6.12, the Trustee may appoint a successor
                   ------------
Authenticating Agent which shall be subject to acceptance by the Company.  Any
successor Authenticating Agent upon acceptance of its appointment hereunder
shall become vested with all the rights, powers and duties of its predecessor
hereunder, with like effect as if originally named as an Authenticating Agent.
No successor Authenticating Agent shall be appointed unless eligible under the
provisions of this Section 6.12.
                   ------------

          The Company agrees to pay to each Authenticating Agent from time to
time reasonable compensation for its services under this Section 6.12.
                                                         ------------

          If an Authenticating Agent is appointed with respect to the Securities
pursuant to this Section 6.12, the Securities may have endorsed thereon, in
                 ------------
addition to or in lieu of the Trustee's certification of authentication, an
alternative certificate of authentication in the following form:

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

                                        ______________________________,
                                        as Trustee
                                        By [Authenticating Agent],
                                        as Authenticating Agent


                                        By ___________________________
                                               Authorized Signature

SECTION 6.13   Disqualification; Conflicting Interests.
               ---------------------------------------

          If the Trustee has or shall acquire a conflicting interest within the
meaning of the Trust Indenture Act, the Trustee shall either eliminate such
interest or resign, to the extent and in the manner provided by, and subject to
the provisions of, the Trust Indenture Act and this Indenture.

                                     -71-
<PAGE>

SECTION 6.14   Preferential Collection of Claims Against Company.
               -------------------------------------------------

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

                                 ARTICLE SEVEN

             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
or convey, transfer or lease all its properties and assets substantially as an
entirety to any Person, and the Company shall not permit any Person to
consolidate with or merge into the Company or convey, transfer or lease all or
substantially all of its properties and assets to the Company, unless:

          (1)  in case the Company shall consolidate with or merge into another
     Person 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, limited
     liability company, partnership or trust, shall be 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, premium, if any, and interest (including Liquidated Damages, if any,
     payable pursuant to Section 9.11) on all of the Securities as applicable,
                         ------------
     and the performance or observance of every covenant of this Indenture on
     the part of the Company to be performed or observed and shall have provided
     for conversion rights in accordance with Article Eleven;
                                              --------------

                                     -72-
<PAGE>

          (2)  immediately after giving effect to such transaction, no Event of
     Default, and no event that after notice or lapse of time or both, would
     become an 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, together with any
     documents required under Section 8.3.
                              -----------

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 all or
substantially all the properties and assets of the Company in accordance with
Section 7.1, the successor Person formed by such consolidation or into or with
-----------
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 EIGHT

                            SUPPLEMENTAL INDENTURES

SECTION 8.1    Supplemental Indentures Without Consent of Holders of Securities.
               ----------------------------------------------------------------

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

                                     -73-
<PAGE>

          (1)  to evidence the succession of another Person to the Company and
     the assumption by any such successor of the covenants and obligations of
     the Company herein and in the Securities as permitted by this Indenture; or

          (2)  to add to the covenants of the Company for the benefit of the
     Holders of Securities or to surrender any right or power herein conferred
     upon the Company; or

          (3)  to secure the Securities; or

          (4)  to make provision with respect to the conversion rights of
     Holders of Securities pursuant to Section 11.11; or
                                       -------------

          (5)  to make any changes or modifications to this Indenture necessary
     in connection with the registration of any Registrable Securities under the
     Securities Act as contemplated by Section 9.11, provided, such action
                                       ------------
     pursuant to this clause (5) shall not, in the judgment of the Company,
     adversely affect the interests of the Holders of Securities in any material
     respect; or

          (6)  to comply with the requirements of the Trust Indenture Act or the
     rules and regulations of the Commission thereunder in order to effect or
     maintain the qualification of this Indenture under the Trust Indenture Act,
     as contemplated by this Indenture or otherwise; or

          (7)  to evidence and provide for the acceptance of appointment
     hereunder by a successor Trustee; or

          (8)  to cure any ambiguity, to correct or supplement any provision
     herein which may be inconsistent with any other provision herein or which
     is otherwise defective, or to make any other provisions with respect to
     matters or questions arising under this Indenture as the Company and the
     Trustee may deem necessary or desirable, provided such action pursuant to
     this clause (8) shall not, in the judgment of the Company, adversely affect
     the interests of the Holders of Securities in any material respect.

          Upon Company Request, accompanied by a Board Resolution authorizing
the execution of any such supplemental indenture, and subject to and upon
receipt by the Trustee of the documents described in Section 8.3 hereof, the
                                                     -----------
Trustee shall join with the Company in the execution of any supplemental
indenture authorized or permitted by the terms of this indenture

                                     -74-
<PAGE>

and to make any further appropriate agreements and stipulations which may be
therein contained.

SECTION 8.2    Supplemental Indentures with Consent of Holders of Securities.
               -------------------------------------------------------------

          With either (a) the written consent of the Holders of not less than a
majority in principal amount of the Outstanding Securities, by the Act of said
Holders delivered to the Company and the Trustee, or (b) by the adoption of a
resolution, at a meeting of Holders of the Outstanding Securities at which a
quorum is present, by the Holders of a majority in principal amount of the
Outstanding Securities represented at such meeting, the Company, when authorized
by a Board Resolution, and the Trustee may enter into an indenture or indentures
supplemental hereto for the purpose of adding any provisions to or changing in
any manner or eliminating any of the provisions of this Indenture or of
modifying in any manner the rights of the Holders of Securities under this
Indenture; provided, however, that no such supplemental indenture shall, without
           --------  -------
the consent or affirmative vote of the Holder of each Outstanding Security
affected thereby,

          (1)  change the Stated Maturity of the principal of, or any
     installment of interest on, any Security, or reduce the principal amount or
     the rate of interest payable thereon or any amount payable upon redemption
     or repurchase pursuant to Article Twelve hereof, or change the obligation
                               --------------
     of the Company to pay Liquidated Damages pursuant to Section 9.11 in a
                                                          ------------
     manner adverse to the Holders, or change the coin or currency in which any
     Security or the interest or any premium thereon or any other amount in
     respect thereof is payable, or impair the right to institute suit for the
     enforcement of any payment in respect of any Security on or after the
     Stated Maturity thereof (or, in the case of redemption or any repurchase,
     on or after the Redemption Date or Repurchase Date, as the case may be) or,
     except as permitted by Section 11.11, adversely affect the right to convert
                            -------------
     any Security as provided in Article Eleven; or
                                 --------------

          (2)  reduce the percentage in principal amount of the Outstanding
     Securities the consent of whose Holders is required for any such
     supplemental indenture or the consent of whose Holders is required for any
     waiver (of compliance with certain provisions of this Indenture or certain
     defaults hereunder and their consequences) provided for in this Indenture;
     or

                                     -75-
<PAGE>

          (3)  modify any of the provisions of this Section and Section 5.13 or
                                                                ------------
     9.12, except to increase any percentage contained herein or therein
     ----
     or to provide that certain other provisions of this Indenture cannot be
     modified or waived without the consent of the Holder of each Outstanding
     Security affected thereby; or

          (4)  modify the provisions of Article Twelve in a manner adverse to
                                        --------------
     the Holders; or

          (5)  modify any of the provisions of Section 9.9 or 9.10.
                                               -----------    ----

          It shall not be necessary for any Act of Holders of Securities under
this Section to approve the particular form of any proposed supplemental
indenture, but it shall be sufficient if such Act shall approve the substance
thereof.

SECTION 8.3    Execution of Supplemental Indentures.
               ------------------------------------

          In executing, or accepting the additional trusts created by, any
supplemental indenture permitted by this Article or the modifications thereby of
the trusts created by this Indenture, the Trustee shall be entitled to receive,
and (subject to Sections 6.1 and 6.3) shall be fully protected in relying upon,
                ------------     ---
an Opinion of Counsel stating that the execution of such supplemental indenture
is authorized or permitted by this Indenture, and that such supplemental
indenture has been duly authorized, executed and delivered by the Company and
constitutes a valid and legally binding obligation of the Company enforceable
against the Company in accordance with its terms.  The Trustee may, but shall
not be obligated to, enter into any such supplemental indenture which affects
the Trustee's own rights, duties or immunities under this Indenture or
otherwise.

SECTION 8.4    Effect of Supplemental Indentures.
               ---------------------------------

          Upon the execution of any supplemental indenture under this Article,
this Indenture shall be modified in accordance therewith, and such supplemental
indenture shall form a part of this Indenture for all purposes; and every Holder
of Securities theretofore or thereafter authenticated and delivered hereunder
appertaining thereto shall be bound thereby.

                                     -76-
<PAGE>

SECTION 8.5    Reference in Securities to Supplemental Indentures.
               --------------------------------------------------

          Securities authenticated and delivered after the execution of any
supplemental indenture pursuant to this Article may, and shall if required by
the Trustee, bear a notation in form approved by the Trustee as to any matter
provided for in such supplemental indenture.  If the Company shall so determine,
new Securities so modified as to conform, in the opinion of the Company and the
Trustee, to any such supplemental indenture may be prepared and executed by the
Company and authenticated and delivered by the Trustee in exchange for
Outstanding Securities.

SECTION 8.6    Notice of Supplemental Indentures.
               ---------------------------------

          Promptly after the execution by the Company and the Trustee of any
supplemental indenture pursuant to the provisions of Section 8.2, the Company
                                                     -----------
shall give notice to all Holders of Securities of such fact, setting forth in
general terms the substance of such supplemental indenture, in the manner
provided in Section 1.6.  Any failure of the Company to give such notice, or any
            -----------
defect therein, shall not in any way impair or affect the validity of any such
supplemental indenture.

                                 ARTICLE NINE

                                   COVENANTS

SECTION 9.1    of Principal, Premium and Interest.
               ----------------------------------

          The Company covenants and agrees that it will duly and punctually pay
the principal of and premium, if any, and interest on the Securities in
accordance with the terms of the Securities and this Indenture.  The Company
will deposit or cause to be deposited with the Trustee, no later than the
opening of business on the date of the Stated Maturity of any Security or no
later than the opening of business on the due date for any installment of
interest, all payments so due, which payments shall be in immediately available
funds on the date of such Stated Maturity or due date, as the case may be.

SECTION 9.2    Maintenance of Offices or Agencies.
               ----------------------------------

          The Company hereby appoints the Corporate Trust Office of the Trustee
or such other office or agency of the Trustee as

                                     -77-
<PAGE>

its agent in the Borough of Manhattan, The City of New York, where Securities
may be presented or surrendered for payment, where Securities may be surrendered
for registration of transfer or exchange, where Securities may be surrendered
for conversion, and where notices and demands to or upon the Company in respect
of the Securities and this Indenture may be served.

          The Company may at any time and from time to time vary or terminate
the appointment of any such agent or appoint any additional agents for any or
all of such purposes; provided, however, that until all of the Securities have
                      --------  -------
been delivered to the Trustee for cancellation, or moneys sufficient to pay the
principal of, premium, if any, and interest on the Securities have been made
available for payment and either paid or returned to the Company pursuant to the
provisions of Section 9.3, the Company will maintain in the State of Minnesota,
              -----------
County of Ramsey, The City of St. Paul, an office or agency where Securities may
be presented or surrendered for payment and conversion, where Securities may be
surrendered for registration of transfer or exchange and where notices and
demands to or upon the Company in respect of the Securities and this Indenture
may be served.  The Company will give prompt written notice to the Trustee, and
notice to the Holders in accordance with Section 1.6, of the appointment or
                                         -----------
termination of any such agents and of the location and any change in the
location of any such office or agency.

          If at any time the Company shall fail to maintain any such required
office or agency, or shall fail to furnish the Trustee with the address thereof,
presentations and surrenders may be made and notices and demands may be served
on the Corporate Trust Office of the Trustee.

SECTION 9.3    Money for Security Payments To Be Held in Trust.
               -----------------------------------------------

          If the Company shall act as its own Paying Agent, it will, on or
before each due date of the principal of, premium, if any, or interest on any of
the Securities, segregate and hold in trust for the benefit of the Persons
entitled thereto a sum sufficient to pay the principal, premium, if any, or
interest so becoming due until such sums shall be paid to such Persons or
otherwise disposed of as herein provided and the Company will promptly notify
the Trustee of its action or failure so to act.

          Whenever the Company shall have one or more Paying Agents, it will, no
later than the opening of business on each due date of the principal of,
premium, if any, or interest on any Securities, deposit with the Trustee a sum
sufficient to pay

                                     -78-
<PAGE>

the principal, premium, if any, or interest so becoming due, such sum to be held
for the benefit of the Persons entitled to such principal, premium, if any, or
interest, and (unless such Paying Agent is the Trustee) the Company will
promptly notify the Trustee of any failure so to act.

          The Company will cause each Paying Agent other than the Trustee to
execute and deliver to the Trustee an instrument in which such Paying Agent
shall agree with the Trustee, subject to the provisions of this Section, that
such Paying Agent will:

          (1)  hold all sums held by it for the payment of the principal of,
     premium, if any, or interest on Securities for the benefit of the Persons
     entitled thereto until such sums shall be paid to such Persons or otherwise
     disposed of as herein provided;

          (2)  give the Trustee notice of any default by the Company (or any
     other obligor upon the Securities) in the making of any payment of
     principal, premium, if any, or interest; and

          (3)  at any time during the continuance of any such default, upon the
     written request of the Trustee, forthwith pay to the Trustee all sums so
     held by such Paying Agent.

          The Company may at any time, for the purpose of obtaining the
satisfaction and discharge of this Indenture or for any other purpose, pay, or
by Company Order direct any Paying Agent to pay, to the Trustee all sums held in
trust by the Company or such Paying Agent, such sums to be held by the Trustee
upon the same trusts as those upon which such sums were held by the Company or
such Paying Agent; and, upon such payment by any Paying Agent to the Trustee,
such Paying Agent shall be released from all further liability with respect to
such money.

          Anything contained herein to the contrary notwithstanding, any money
held by the Trustee or any Paying Agent in trust for the payment and discharge
of the principal of, premium, if any, or interest on any Security which remains
unclaimed for two (2) years after the date when each payment of such principal,
premium or interest has become payable shall be repaid within sixty (60) days of
such date by the Trustee to the Company as its absolute property free from
trust, and the Trustee shall thereupon be released and discharged with respect
thereto and the Holders shall look only to the Company for the payment of the
principal, premium or interest on such Security.  The Trustee shall not be
liable to the Company or any Holder for

                                     -79-
<PAGE>

interest on funds held by it for the payment and discharge of the principal,
premium or interest on any of the Securities to any Holder. The Company shall
not be liable for any interest on the sums paid to it pursuant to this paragraph
and shall not be regarded as a trustee of such money.

SECTION 9.4    Existence.
               ---------

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

SECTION 9.5    Maintenance of Properties.
               -------------------------

          The Company will cause all properties used or useful in the conduct of
its business or the business of any Subsidiary to be maintained and kept in good
condition, repair and working order and supplied with all necessary equipment
and will cause to be made all necessary repairs, renewals, replacements,
betterments and improvements thereof, all as in the judgment of the Company may
be necessary so that the business carried on in connection therewith may be
properly and advantageously conducted at all times; provided, however, that
                                                    --------  -------
nothing in this Section shall prevent the Company from discontinuing the
operation or maintenance of any of such properties if such discontinuance is, in
the judgment of the Company, desirable in the conduct of its business or the
business of any Subsidiary and not disadvantageous in any material respect to
the Holders.

SECTION 9.6    Payment of Taxes and Other Claims.
               ---------------------------------

          The Company will pay or discharge, or cause to be paid or discharged,
before the same may become delinquent, (1) all taxes, assessments and
governmental charges levied or imposed upon the Company or any Subsidiary or
upon the income, profits or property of the Company or any Subsidiary, (2) all
claims for labor, materials and supplies which, if unpaid, might by law become a
lien or charge upon the property of the Company or any Subsidiary, and (3) all
stamps and other duties, if any, which may be imposed by the United States or
any political subdivision thereof or therein in connection with the issuance,
transfer, exchange or conversion of any Securities or with respect to this

                                     -80-
<PAGE>

Indenture; provided, however, that, in the case of clauses (1) and (2), the
           --------  -------
Company shall not be required to pay or discharge or cause to be paid or
discharged any such tax, assessment, charge or claim (a) if the failure to do so
will not, in the aggregate, have a material adverse impact on the Company, or
(b) if the amount, applicability or validity is being contested in good faith by
appropriate proceedings.

SECTION 9.7  Registration and Listing.
             ------------------------

          Within a reasonable time after the issuance of the Global Security,
the Company (i) will effect all registrations with, and obtain all approvals by,
all governmental authorities that may be necessary under any United States
Federal or state law (including the Securities Act, the Exchange Act and state
securities and Blue Sky laws) before the shares of Common Stock issuable upon
conversion of Securities may be lawfully issued and delivered, and qualified or
listed as contemplated by clause (ii) (it being understood that the Company
shall not be required to register the Securities under the Securities Act,
except pursuant to the Registration Rights Agreement referred to in Section
                                                                    -------
9.11); and (ii) will cause the shares of Common Stock required to be issued and
delivered upon conversion of Securities, prior to such issuance or delivery, to
be listed on the New York Stock Exchange or, if the Common Stock is not then
listed on the New York Stock Exchange, list the Common Stock or qualify the
Common Stock for quotation on each national securities exchange or quotation
system on which outstanding Common Stock is listed or quoted at the time of such
delivery.  Nothing in this Section 9.7 will limit the application of Section
                           -----------                               -------
9.11.
----

SECTION 9.8  Statement by Officers as to Default.
             -----------------------------------

          The Company shall deliver to the Trustee, within 120 days after the
end of each fiscal year of the Company ending after the date hereof, an
Officers' Certificate (one of the signers of which shall be the Company's
principal executive, principal financial or principal accounting officer),
stating whether or not to the best knowledge of the signers thereof the Company
is in default in the performance and observance of any of the terms, provisions
and conditions of this Indenture (without regard to any period of grace or
requirement of notice provided hereunder) and, if the Company shall be in
default, specifying all such defaults and the nature and status thereof of which
they may have knowledge.

                                     -81-
<PAGE>

          The Company will deliver to the Trustee, forthwith upon becoming aware
of any default in the performance or observance of any covenant, agreement or
condition contained in this Indenture, or any Event of Default, an Officers'
Certificate specifying with particularity such default or Event of Default and
further stating what action the Company has taken, is taking or proposes to take
with respect thereto.

          Any notice required to be given under this Section 9.8 shall be
                                                     -----------
delivered to the Trustee at its Corporate Trust Office.

SECTION 9.9  Delivery of Certain Information.
             -------------------------------

          At any time when the Company is not subject to Section 13 or 15(d) of
                                                         ----------    -----
the Exchange Act, upon the request of a Holder of a Security or the holder of
shares of Common Stock issued upon conversion thereof, the Company will promptly
furnish or cause to be furnished Rule 144A Information (as defined below) to
such Holder of Securities or such holder of shares of Common Stock issued upon
conversion of Securities, or to a prospective purchaser of any such security
designated by any such Holder or holder, as the case may be, to the extent
required to permit compliance by such Holder or holder with Rule 144A under the
Securities Act (or any successor provision thereto) in connection with the
resale of any such security; provided, however, that the Company shall not be
                             --------  -------
required to furnish such information in connection with any request made on or
after the date which is two years from the later of (i) the date such a security
(or any such predecessor security) was last acquired from the Company or (ii)
the date such a security (or any such predecessor security) was last acquired
from an "affiliate" of the Company within the meaning of Rule 144 under the
Securities Act (or any successor provision thereto).  "Rule 144A Information"
shall be such information as is specified pursuant to Rule 144A(d)(4) under the
Securities Act (or any successor provision thereto).

SECTION 9.10  Resale of Certain Securities; Reporting Issuer.
              ----------------------------------------------

          During the period beginning on the last date of original issuance of
the Securities and ending on the date that is two years from such date, the
Company will not, and will not permit any of its subsidiaries or other
"affiliates" (as defined under Rule 144 under the Securities Act or any
successor provision thereto) controlled by it to, resell (x) any Securities
which constitute "restricted

                                     -82-
<PAGE>

securities" under Rule 144 that in either case have been reacquired by any of
them. The Trustee shall have no responsibility in respect of the Company's
performance of its agreement in the preceding sentence.

SECTION 9.11  Registration Rights.
              -------------------

          The Company agrees that the Holders from time to time of Registrable
Securities (as defined below) are entitled to the benefits of a Registration
Rights Agreement, dated as of June 11, 2001 (the "Registration Rights
Agreement"), executed by the Company. Pursuant to the Registration Rights
Agreement, the Company has agreed for the benefit of the Holders from time to
time of Registrable Securities, at the Company's expense, (i) to file within 90
days after the first date of original issuance of the Securities, a shelf
registration statement (the "Shelf Registration Statement") with the Commission
with respect to resales of the Registrable Securities, (ii) thereafter use
reasonable efforts to cause such Shelf Registration Statement to be declared
effective by the Commission within 180 days after the first date of original
issuance of the Securities, and (iii) to use reasonable efforts to maintain such
Shelf Registration Statement continuously effective under the Securities Act of
1933, as amended, until a period of two years from the date of the effectiveness
of the Shelf Registration Statement or, if earlier, until (A) there are no
outstanding Registrable Securities registered under the Shelf Registration
Statement or (B) the expiration of the period referred to in Rule 144(k) (or any
successor provision thereto) under the Securities Act with respect to all
Registrable Securities held by Persons that are not Affiliates of the Company.

          Section 2(a) of the Registration Rights Agreement provides that, upon
written notice to each Holder of a Registrable Security, the Company may
postpone having the Shelf Registration Statement declared effective as required
by Section 2(a) of the Registration Rights Agreement for a reasonable time
specified in the notice but not exceeding 90 days if the Company is in
possession of material non-public information the disclosure of which would have
a material adverse effect on the business, operations, prospects, condition
(financial or otherwise) of the Company and its subsidiaries, taken as a whole.
Notwithstanding any postponement pursuant to Section 2(a) of the Registration
Rights Agreement, if (i) on or prior to 90 days following the date of original
issuance of the Registrable

                                     -83-
<PAGE>

Securities, such Shelf Registration Statement is not declared effective (each, a
"Registration Default"), additional interest ("Liquidated Damages") will accrue
on the Registrable Securities from and including the day following such
Registration Default to but excluding the day on which such Registration Default
has been cured or, if earlier, the last day upon which the Shelf Registration
Statement is required to be kept effective. Liquidated Damages will be paid
semi-annually in arrears, with the first semi-annual payment due on the first
Interest Payment Date in respect of the Registrable Securities following the
date on which such Liquidated Damages begin to accrue, and will accrue at a rate
per annum equal to an additional one-quarter of one percent (.25%) of the
principal amount of the Registrable Securities to and including the 90th day
following such Registration Default and at a rate per annum equal to one-half of
one percent (.50%) thereof from and after the 91st day following such
Registration Default. In the event that the Shelf Registration Statement ceases
to be effective prior to the second annual anniversary of the initial effective
date of the Shelf Registration Statement or such earlier date as is provided in
the Registration Rights Agreement for a period in excess of 45 days, whether or
not consecutive, during any 90-day period or more than 90 days, whether or not
consecutive, during any 12-month period, then the interest rate borne by the
Registrable Securities shall increase by an additional one-half of one percent
(.50%) per annum on the 46th day of the 90-day period or the 91st day of the
applicable 12-month period such Shelf Registration Statement ceases to be
effective to but excluding the day on which the Shelf Registration Statement
again becomes effective, or if earlier, the last day upon which the Shelf
Registration Statement is required to be kept effective.

          Whenever in this Indenture there is mentioned, in any context, the
payment of the principal of, premium, if any, or interest on, or in respect of,
any Registrable Security, such mention shall be deemed to include mention of the
payment of Liquidated Damages provided for in this Section to the extent that,
in such context, Liquidated Damages are, were or would be payable in respect
thereof pursuant to the provisions of this Section, and express mention of the
payment of Liquidated Damages (if applicable) in any provisions hereof shall not
be construed as excluding Liquidated Damages in those provisions hereof where
such express mention is not made.

          For the purposes of the Registration Rights Agreement, "Registrable
Securities" means all or any portion of the Registered Securities issued from
time to time under this

                                     -84-
<PAGE>

Indenture and the shares of Common Stock issuable upon conversion of such
Securities; provided, however, that a Security or the shares of Common Stock
            --------  -------
issuable upon conversion of a Security ceases to be a Registrable Security when
it (i) has been effectively registered under the Securities Act and sold in a
manner contemplated by the Shelf Registration Statement, (ii) has been
transferred in compliance with Rule 144 under the Securities Act (or any
successor provisions thereto)or is transferable pursuant to paragraph (k) of
Rule 144 (or any successor provision thereto) or (iii) otherwise has been
transferred and a new Security or share of Common Stock not subject to transfer
restrictions under the Securities Act has been delivered by or on behalf of the
Company in accordance with Section 3.5(b).
                           --------------

          If a Security, or the shares of Common Stock issuable upon conversion
of a Security, is a Registrable Security, and the Holder thereof elects to sell
such Registrable Security pursuant to the Shelf Registration Statement then, by
its acceptance thereof, the Holder of such Registrable Security will have agreed
to be bound by the terms of the Registration Rights Agreement relating to the
Registrable Securities which are the subject of such election.

          For the purposes of the Registration Rights Agreement, the term
"Holder" includes any Person that has a beneficial interest in any Global
Security or any beneficial interest in a global security representing shares of
Common Stock issuable upon conversion of a Security.  The Company will give the
Trustee prompt written notice of any Registration Default, and of any cure
thereof.

SECTION 9.12  Waiver of Certain Covenants.
              ---------------------------

          The Company may omit in any particular instance to comply with any
covenant or conditions set forth in Sections 9.5 and 9.6, inclusive (other than
                                    ------------     ---
a covenant or condition which under Article Eight cannot be modified or amended
                                    -------------
without the consent of the Holder of each Outstanding Security affected), if
before the time for such compliance the Holders shall, through the written
consent of, not less than a majority in principal amount of the Outstanding
Securities, either waive such compliance in such instance or generally waive
compliance with such covenant or condition, but no such waiver shall extend to
or affect such covenant or condition except to the extent so expressly waived,
and, until such waiver shall become effective, the obligations of the Company
and the duties of the Trustee or

                                     -85-
<PAGE>

any Paying or Conversion Agent in respect of any such covenant or condition
shall remain in full force and effect.




                                  ARTICLE TEN

                            REDEMPTION OF SECURITIES

SECTION 10.1  Right of Redemption.
              -------------------

          The Securities may be redeemed in accordance with the provisions of
the form of Securities set forth in Section 2.2.
                                    -----------

SECTION 10.2  Applicability of Article.
              ------------------------

          Redemption of Securities at the election of the Company or otherwise,
as permitted or required by any provision of the Securities or this Indenture,
shall be made in accordance with such provision and this Article Ten.
                                                         -----------

SECTION 10.3  Election to Redeem; Notice to Trustee.
              -------------------------------------

          The election of the Company to redeem any Securities shall be
evidenced by a Board Resolution.  In case of any redemption at the election of
the Company of any of the Securities, the Company shall, at least 45 days prior
to the Redemption Date fixed by the Company (unless a shorter notice shall be
satisfactory to the Trustee), notify the Trustee in writing of such Redemption
Date.  If the Securities are to be redeemed pursuant to an election of the
Company which is subject to a condition specified in the form of Securities set
forth in Section 2.2, the Company shall furnish the Trustee with an Officers'
         -----------
Certificate stating that the Company is entitled to effect such redemption and
setting forth a statement of facts showing that the conditions precedent to the
right of the Company so to redeem have occurred.

SECTION 10.4  Selection by Trustee of Securities To Be Redeemed.
              -------------------------------------------------

          If less than all the Securities are to be redeemed, the particular
Securities to be redeemed shall be selected by the Trustee within three Business
Days after it receives the notice described in Section 10.3, from the
                                               ------------
Outstanding Securities not previously called for redemption, by such method as
the Trustee may deem fair and appropriate.

                                     -86-
<PAGE>

          If any Registered 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 (so far as may be) to be the portion selected for redemption.
Securities which have been converted during a selection of Securities to be
redeemed may be treated by the Trustee as Outstanding for the purpose of such
selection.

          The Trustee shall promptly notify the Company and each Security
Registrar in writing of the Securities selected for redemption and, in the case
of any Securities selected for partial redemption, the principal amount and
certificate numbers thereof to be redeemed.

          For all purposes of this Indenture, unless the context otherwise
requires, all provisions relating to the redemption of Securities shall relate,
in the case of any Securities redeemed or to be redeemed only in part, to the
portion of the principal amount of such Securities which has been or is to be
redeemed.

SECTION 10.5  Notice of Redemption.
              --------------------

          Notice of redemption shall be given in the manner provided in Section
                                                                        -------
1.6 to the Holders of Securities to be redeemed not less than 30 nor more than
---
60 days prior to the Redemption Date, and such notice shall be irrevocable.

          All notices of redemption shall identify the Securities to be redeemed
(including CUSIP numbers) and shall state:

          (1)  the Redemption Date,

          (2)  the Redemption Price, and accrued interest, if any,

          (3)  if less than all Outstanding Securities are to be redeemed, the
     aggregate principal amount of Securities to be redeemed,

          (4)  that on the Redemption Date the Redemption Price, and accrued
     interest, if any, will become due and payable upon each such Security to be
     redeemed, and that interest thereon shall cease to accrue on and after said
     date,

          (5)  the Conversion Rate, the date on which the right to convert the
     Securities to be redeemed will terminate and

                                     -87-
<PAGE>

     the places where such Securities may be surrendered for conversion, and

          (6)  the place or places where such Securities are to be surrendered
     for payment of the Redemption Price and accrued interest, if any.

          Notice of redemption of Securities to be redeemed at the election of
the Company shall be given by the Company or, at the Company's written request,
by the Trustee in the name of and at the expense of the Company.  Notice of
redemption of Securities to be redeemed at the election of the Company received
by the Trustee shall be given by the Trustee to each Paying Agent in the name of
and at the expense of the Company.

SECTION 10.6   Deposit of Redemption Price.
               ---------------------------

          Not less than one Business Day prior to any Redemption Date, the
Company shall deposit with the Trustee (or, if the Company is acting as its own
Paying Agent, segregate and hold in trust as provided in Section 9.3) an amount
                                                         -----------
of money (which shall be in immediately available funds on such Redemption Date)
sufficient to pay the Redemption Price of, and (except if the Redemption Date
shall be an Interest Payment Date) accrued interest on, all the Securities which
are to be redeemed on that date other than any Securities called for redemption
on that date which have been converted prior to the date of such deposit.

          If any Security called for redemption is converted, any money
deposited with the Trustee or so segregated and held in trust for the redemption
of such Security shall (subject to any right of the Holder of such Security or
any Predecessor Security to receive interest as provided in the last paragraph
of Section 3.7) be paid to the Company on Company Request or, if then held by
   -----------
the Company, shall be discharged from such trust.

SECTION 10.7  Securities Payable on Redemption Date.
              -------------------------------------

          Notice of redemption having been given as aforesaid, the Securities so
to be redeemed shall, on the Redemption Date, become due and payable at the
Redemption Price therein specified and from and after such date (unless the
Company shall default in the payment of the Redemption Price, including accrued
interest) such Securities shall cease to bear interest.  Upon surrender of any
Security for redemption in accordance with said notice such Security shall be
paid by the Company at the Redemption Price together with accrued and unpaid
interest to

                                     -88-
<PAGE>

the Redemption Date; provided, however, that installments of interest on
                     --------  -------
Securities whose Stated Maturity is on or prior to the Redemption Date shall be
payable to the Holders of such Securities, or one or more Predecessor
Securities, registered as such on the relevant Record Date according to their
terms and the provisions of Section 3.7.
                            -----------

          If any Security called for redemption shall not be so paid upon
surrender thereof for redemption, the principal amount of, premium, if any, and,
to the extent permitted by applicable law, accrued interest on such Security
shall, until paid, bear interest from the Redemption Date at a rate of 4.50% per
annum and such Security shall remain convertible until the principal of such
Security (or portion thereof, as the case may be) shall have been paid or duly
provided for.

SECTION 10.8  Securities Redeemed in Part.
              ---------------------------

          Any Security which is to be redeemed only in part shall be surrendered
at an office or agency of the Company designated for that purpose pursuant to
Section 9.2 (with, if the Company or the Trustee so requires, due endorsement
by, or a written instrument of transfer in form satisfactory to the Company and
the Trustee duly executed by, the Holder thereof or his attorney duly authorized
in writing), and the Company shall execute, and the Trustee shall authenticate
and make available for delivery to the Holder of such Security without service
charge, a new Registered Security or Securities, of any authorized denomination
as requested by such Holder, in aggregate principal amount equal to and in
exchange for the unredeemed portion of the principal of the Security so
surrendered.

SECTION 10.9  Conversion Arrangement on Call for Redemption.
              ---------------------------------------------

          In connection with any redemption of the Securities, the Company may
arrange for the purchase and conversion of any Securities by an agreement with
one or more investment bankers or other purchasers (the "Purchasers") to
purchase such Securities by paying to the Trustee in trust for the Holders, on
or before the Redemption Date, an amount not less than the applicable Redemption
Price, together with interest accrued and unpaid to the Redemption Date, of such
Securities. Notwithstanding anything to the contrary contained in this Article
                                                                       -------
Ten, the obligation of the Company to pay the Redemption Price, together with
---
interest accrued and unpaid to the Redemption Date, shall be deemed to be
satisfied and discharged to the extent such amount is so paid by such
Purchasers. If such

                                     -89-
<PAGE>

an agreement is entered into (a copy of which shall be filed with the Trustee
prior to the close of business on the second Business Day immediately prior to
the Redemption Date), any Securities called for redemption that are not duly
surrendered for conversion by the Holders thereof may, at the option of the
Company, be deemed, to the fullest extent permitted by law, and consistent with
any agreement or agreements with such Purchasers, to be acquired by such
Purchasers from such Holders and (notwithstanding anything to the contrary
contained in this Article Ten) surrendered by such Purchasers for
                  -----------
conversion, all as of immediately prior to the close of business on the
Redemption Date (and the right to convert any such Securities shall be extended
through such time), subject to payment of the above amount as aforesaid. At the
direction of the Company, the Trustee shall hold and dispose of any such amount
paid to it by the Purchasers to the Holders in the same manner as it would
monies deposited with it by the Company for the redemption of Securities.
Without the Trustee'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 Trustee as set forth in this Indenture, and the Company
agrees to indemnify the Trustee 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, including reasonable legal fees,
incurred by the Trustee 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.

                                ARTICLE ELEVEN


                            CONVERSION OF SECURITIES

SECTION 11.1  Conversion Privilege and Conversion Rate.
              ----------------------------------------

          Subject to and upon compliance with the provisions of this Article, at
the option of the Holder thereof, any Security or any portion of the principal
amount thereof that is U.S.$1,000 or an integral multiple of U.S.$1,000 may be
converted into fully paid and nonassessable shares (calculated as to each
conversion to the nearest 1/100th of a share) of Common Stock of the Company at
the Conversion Rate, determined

                                     -90-
<PAGE>

as hereinafter provided, in effect at the time of conversion. Such conversion
right shall commence upon the original issuance of the Securities and expire at
the close of business on June 15, 2006, subject, in the case of conversion of
any Global Security, to any Applicable Procedures. In case a Security or portion
thereof is called for redemption at the election of the Company or the Holder
thereof exercises his right to require the Company to repurchase the Security,
such conversion right in respect of the Security, or portion thereof so called,
shall expire at the close of business on the Business Day immediately preceding
the Redemption Date or the Repurchase Date, as the case may be, unless the
Company defaults in making the payment due upon redemption or repurchase, as the
case may be (in each case subject as aforesaid to any Applicable Procedures with
respect to any Global Security).

          The rate at which shares of Common Stock shall be delivered upon
conversion (herein called the "Conversion Rate") shall be initially 24.9389
shares of Common Stock for each U.S.$1,000 principal amount of Securities.  The
Conversion Rate shall be adjusted in certain instances as provided in this
Article Eleven.
--------------

SECTION 11.2  Exercise of Conversion Privilege.
              --------------------------------

          In order to exercise the conversion privilege, the Holder of any
Security to be converted shall surrender such Security, duly endorsed or
assigned to the Company or in blank, at any office or agency of the Company
maintained for that purpose pursuant to Section 9.2, accompanied by a duly
                                        -----------
signed conversion notice substantially in the form set forth in Section 2.4
                                                                -----------
stating that the Holder elects to convert such Security or, if less than the
entire principal amount thereof is to be converted, the portion thereof to be
converted.  Each Security surrendered for conversion (in whole or in part)
during the period from the close of business on any Regular Record Date next
preceding any Interest Payment Date to the opening of business on such Interest
Payment Date shall (except in the case of any Security or portion thereof which
has been called for redemption on a Redemption Date, or is to be repurchased on
a Repurchase Date, with the consequence that the conversion right of such
Security would terminate between such Regular Record Date and the close of
business on such Interest Payment Date) be accompanied by payment in New York
Clearing House funds or other 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 (or part thereof, as the case may be) being surrendered for
conversion. The interest so payable on

                                     -91-
<PAGE>

such Interest Payment Date with respect to any Security (or portion thereof, if
applicable) which is surrendered for conversion during the period from the close
of business on any Record Date next preceding any Interest Payment Date to the
opening of business on such Interest Payment Date and which Security has been
called for redemption on a Redemption Date, or is repurchasable on a Repurchase
Date, with the consequence that the conversion right of such Security would
terminate between such Regular Record Date and the close of business on such
Interest Payment Date, shall be paid to the Holder of such Security being
converted in an amount equal to the interest that would have been payable on
such Security if such Security had been converted as of the close of business on
such Interest Payment Date. The interest so payable on such Interest Payment
Date in respect of any Security (or portion thereof, as the case may be) which
has not been called for redemption on a Redemption Date, or is not eligible for
repurchase on a Repurchase Date, with the consequence of termination of the
conversion right as aforesaid, which Security (or portion thereof, as the case
may be) is surrendered for conversion during the period from the close of
business on any Record Date next preceding any Interest Payment Date to the
opening of business on such Interest Payment Date, shall be paid to the Holder
of such Security as of such Regular Record Date. Interest payable in respect of
any Security surrendered for conversion on or after an Interest Payment Date
shall be paid to the Holder of such Security as of the next preceding Regular
Record Date, notwithstanding the exercise of the right of conversion. Except as
provided in this paragraph and subject to the last paragraph of Section 3.7, no
                                                                -----------
cash payment or adjustment shall be made upon any conversion on account of any
interest accrued from the Interest Payment Date next preceding the conversion
date, in respect of any Security (or part thereof, as the case may be)
surrendered for conversion, or on account of any dividends on the Common Stock
issued upon conversion. The Company's delivery to the Holder of the number of
shares of Common Stock (and cash in lieu of fractions thereof, as provided in
this Indenture) into which a Security is convertible will be deemed to satisfy
the Company's obligation to pay the principal amount of the Security.

          Securities shall be deemed to have been converted on the day of
surrender of such Securities for conversion in accordance with the foregoing
provisions, and at such time the rights of the Holders of such Securities as
Holders shall cease, and the Person or Persons entitled to receive the Common
Stock issuable upon conversion shall be treated for all purposes as the record
holder or holders of such Common Stock at such time.

                                     -92-
<PAGE>

As promptly as practicable on or after the conversion date, the Company shall
issue and deliver to the Trustee, for delivery to the Holder, a certificate or
certificates for the number of full shares of Common Stock issuable upon
conversion, together with payment in lieu of any fraction of a share, as
provided in Section 11.3.
            ------------

          All shares of Common Stock delivered upon such conversion of
Securities shall bear restrictive legends substantially in the form of the
legends required to be set forth on the Securities pursuant to Section 3.5 and
                                                               -----------
shall be subject to the restrictions on transfer provided in such legends.
Neither the Trustee nor any agent maintained for the purpose of such conversion
shall have any responsibility for the inclusion or content of any such
restrictive legends on such Common Stock; provided, however, that the Trustee or
                                          --------  -------
any agent maintained for the purpose of such conversion shall have provided to
the Company or to the Company's transfer agent for such Common Stock, prior to
or concurrently with a request to the Company to deliver such Common Stock,
written notice that the Securities delivered for conversion are Securities.

In the case of any Security which is converted in part only, upon such
conversion the Company shall execute and the Trustee shall authenticate and make
available for delivery to the Holder thereof, at the expense of the Company, a
new Registered Security or Securities of authorized denominations in an
aggregate principal amount equal to the unconverted portion of the principal
amount of such Security.  A Security may be converted in part, but only if the
principal amount of such Security to be converted is any integral multiple of
U.S.$1,000 and the principal amount of such security to remain Outstanding after
such conversion is equal to U.S.$1,000 or any integral multiple of U.S.$1,000 in
excess thereof.

SECTION 11.3  Fractions of Shares.
              -------------------

          No fractional shares of Common Stock shall be issued upon conversion
of any Security or Securities.  If more than one Security shall be surrendered
for conversion at one time by the same Holder, the number of full shares which
shall be issuable upon conversion thereof shall be computed on the basis of the
aggregate principal amount of the Securities (or specified portions thereof) so
surrendered.  Instead of any fractional share of Common Stock which would
otherwise be issuable upon conversion of any Security or Securities (or
specified portions thereof), the Company shall calculate and pay a cash
adjustment in respect of such fraction (calculated to the nearest 1/100th

                                     -93-
<PAGE>

of a share) in an amount equal to the same fraction of the Closing Price Per
Share at the close of business on the day of conversion.

SECTION 11.4  Adjustment of Conversion Rate.
              -----------------------------

          The Conversion Rate shall be subject to adjustments from time to time
as follows:

          (1)  (1)  In case the Company shall pay or make a dividend or other
distribution on any class of capital stock of the Company payable in shares of
Common Stock, the Conversion Rate in effect at the opening of business on the
day following the date fixed for the determination of stockholders entitled to
receive such dividend or other distribution shall be increased by dividing such
Conversion Rate by a fraction of which the numerator shall be the number of
shares of Common Stock outstanding at the close of business on the date fixed
for such determination and the denominator shall be the sum of such number of
shares and the total number of shares constituting such dividend or other
distribution, such increase to become effective immediately after the opening of
business on the day following the date fixed for such determination. If, after
any such date fixed for determination, any dividend or distribution is not in
fact paid, the Conversion Rate shall be immediately readjusted, effective as of
the date the Board of Directors determines not to pay such dividend or
distribution, to the Conversion Rate that would have been in effect if such
determination date had not been fixed. For the purposes of this paragraph (1),
the number of shares of Common Stock at any time outstanding shall not include
shares held in the treasury of the Company but shall include shares issuable in
respect of scrip certificates issued in lieu of fractions of shares of Common
Stock. The Company will not pay any dividend or make any distribution on shares
of Common Stock held in the treasury of the Company.

          (2)  (2)  In case the Company shall issue rights, options or warrants
to all holders of its Common Stock entitling them to subscribe for or purchase
shares of Common Stock at a price per share less than the current market price
per share (determined as provided in paragraph (8) of this Section 11.4) of the
                                                           ------------
Common Stock on the date fixed for the determination of stockholders entitled to
receive such rights, options or warrants (other than any rights, options or
warrants that by their terms will also be issued to any Holder upon conversion
of a Security into shares of Common Stock without any action required by the
Company or any other Person), the Conversion

                                     -94-
<PAGE>

Rate in effect at the opening of business on the day following the date fixed
for such determination shall be increased by dividing such Conversion Rate by a
fraction of which the numerator shall be the number of shares of Common Stock
outstanding at the close of business on the date fixed for such determination
plus the number of shares of Common Stock which the aggregate of the offering
price of the total number of shares of Common Stock so offered for subscription
or purchase would purchase at such current market price and the denominator
shall be the number of shares of Common Stock outstanding at the close of
business on the date fixed for such determination plus the number of shares of
Common Stock so offered for subscription or purchase, such increase to become
effective immediately after the opening of business on the day following the
date fixed for such determination. If, after any such date fixed for
determination, any such rights, options or warrants are not in fact issued, the
Conversion Rate shall be immediately readjusted, effective as of the date the
Board of Directors determines not to issue such rights, options or warrants, to
the Conversion Rate that would have been in effect if such determination date
had not been fixed. For the purposes of this paragraph (2), the number of shares
of Common Stock at any time outstanding shall not include shares held in the
treasury of the Company but shall include shares issuable in respect of scrip
certificates issued in lieu of fractions of shares of Common Stock. The Company
will not issue any rights, options or warrants in respect of shares of Common
Stock held in the treasury of the Company.

          (3)  In case outstanding shares of Common Stock shall be subdivided
into a greater number of shares of Common Stock, the Conversion Rate in effect
at the opening of business on the day following the day upon which such
subdivision becomes effective shall be proportionately increased, and,
conversely, in case outstanding shares of Common Stock shall each be combined
into a smaller number of shares of Common Stock, the Conversion Rate in effect
at the opening of business on the day following the day upon which such
combination becomes effective shall be proportionately reduced, such increase or
reduction, as the case may be, to become effective immediately after the opening
of business on the day following the day upon which such subdivision or
combination becomes effective.

          (4)  In case the Company shall, by dividend or otherwise, distribute
to all holders of its Common Stock evidences of its indebtedness, shares of any
class of capital stock, or other property (including cash or assets or

                                     -95-
<PAGE>

securities, but excluding (i) any rights, options or warrants referred to in
paragraph (2) of this Section, (ii) any dividend or distribution paid
exclusively in cash, (iii) any dividend or distribution referred to in paragraph
(1) of this Section and (iv) any merger or consolidation to which Section 11.11
                                                                  -------------
applies), the Conversion Rate shall be adjusted so that the same shall equal the
rate determined by dividing the Conversion Rate in effect immediately prior to
the close of business on the date fixed for the determination of stockholders
entitled to receive such distribution by a fraction of which the numerator shall
be the current market price per share (determined as provided in paragraph (8)
of this Section 11.4) of the Common Stock on the date fixed for such
        ------------
determination less the then fair market value (as determined by the Board of
Directors, whose determination shall be conclusive and described in a Board
Resolution filed with the Trustee) of the portion of the assets, shares or
evidences of indebtedness so distributed applicable to one share of Common Stock
and the denominator shall be such current market price per share of the Common
Stock, such adjustment to become effective immediately prior to the opening of
business on the day following the date fixed for the determination of
stockholders entitled to receive such distribution. If, after any such date
fixed for determination, any such distribution is not in fact made, the
Conversion Rate shall be immediately readjusted, effective as of the date the
Board of Directors determines not to make such distribution, to the Conversion
Rate that would have been in effect if such determination date had not been
fixed.

          (5)  In case the Company shall, by dividend or otherwise, distribute
to all holders of its Common Stock cash (excluding any cash that is distributed
upon a merger or consolidation to which Section 11.11 applies or as part of a
                                        -------------
distribution referred to in paragraph (4) of this Section) in an aggregate
amount that, combined together with (I) the aggregate amount of any other cash
distributions to all holders of its Common Stock made exclusively in cash within
the 12 months preceding the date of payment of such distribution and in respect
of which no adjustment pursuant to this paragraph (5) has been made and (II) the
aggregate of any cash plus the fair market value (as determined by the Board of
Directors, whose determination shall be conclusive and described in a Board
Resolution) of consideration payable in respect of any tender offer by the
Company or any of its subsidiaries for all or any portion of the Common Stock
concluded within the 12 months preceding the date of payment of such
distribution and in respect of which no adjustment pursuant to paragraph (6) of
this

                                     -96-
<PAGE>

Section 11.4 has been made (the "combined cash and tender amount") exceeds
------------
10% of the product of the current market price per share (determined as provided
in paragraph (8) of this Section 11.4) of the Common Stock on the date for the
                         ------------
determination of holders of shares of Common Stock entitled to receive such
distribution times the number of shares of Common Stock outstanding on such date
(the "aggregate current market price"), then, and in each such case, immediately
after the close of business on such date for determination, the Conversion Rate
shall be adjusted so that the same shall equal the rate determined by dividing
the Conversion Rate in effect immediately prior to the close of business on the
date fixed for determination of the stockholders entitled to receive such
distribution by a fraction (i) the numerator of which shall be equal to the
current market price per share (determined as provided in paragraph (8) of this
Section) of the Common Stock on the date fixed for such determination less an
amount equal to the quotient of (x) the excess of such combined cash and tender
amount over such aggregate current market price divided by (y) the number of
shares of Common Stock outstanding on such date for determination and (ii) the
denominator of which shall be equal to the current market price per share
(determined as provided in paragraph (8) of this Section 11.4) of the Common
                                                 ------------
Stock on such date for determination.


          (6) (6) In case a tender offer made by the Company or any Subsidiary
for all or any portion of the Common Stock shall expire and such tender offer
(as amended upon the expiration thereof) shall require the payment to
stockholders (based on the acceptance (up to any maximum specified in the terms
of the tender offer) of Purchased Shares (as defined below)) of an aggregate
consideration having a fair market value (as determined by the Board of
Directors, whose determination shall be conclusive and described in a Board
Resolution) that combined together with (I) the aggregate of the cash plus the
fair market value (as determined by the Board of Directors, whose determination
shall be conclusive and described in a Board Resolution), as of the expiration
of such tender offer, of consideration payable in respect of any other tender
offer by the Company or any Subsidiary for all or any portion of the Common
Stock expiring within the 12 months preceding the expiration of such tender
offer and in respect of which no adjustment pursuant to this paragraph (6) has
been made and (II) the aggregate amount of any cash distributions to all holders
of the Company's Common Stock within 12 months preceding the expiration of such
tender offer and in respect of which no adjustment pursuant to paragraph (5) of
this Section has been

                                     -97-
<PAGE>

made (the "combined tender and cash amount") exceeds 10% of the product of the
current market price per share of the Common Stock (determined as provided in
paragraph (8) of this Section 11.4) as of the last time (the "Expiration Time")
                      ------------
tenders could have been made pursuant to such tender offer (as it may be
amended) times the number of shares of Common Stock outstanding (including any
tendered shares) as of the Expiration Time, then, and in each such case,
immediately prior to the opening of business on the day after the date of the
Expiration Time, the Conversion Rate shall be adjusted so that the same shall
equal the rate determined by dividing the Conversion Rate immediately prior to
close of business on the date of the Expiration Time by a fraction (i) the
numerator of which shall be equal to (A) the product of (I) the current market
price per share of the Common Stock (determined as provided in paragraph (8) of
this Section 11.4) on the date of the Expiration Time multiplied by (II) the
     ------------
number of shares of Common Stock outstanding (including any tendered shares) on
the Expiration Time less (B) the combined tender and cash amount, and (ii) the
denominator of which shall be equal to the product of (A) the current market
price per share of the Common Stock (determined as provided in paragraph (8) of
this Section 11.4) as of the Expiration Time multiplied by (B) the number of
     ------------
shares of Common Stock outstanding (including any tendered shares) as of the
Expiration Time less the number 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").

          (7)  The reclassification of Common Stock into securities including
other than Common Stock (other than any reclassification upon a consolidation or
merger to which Section 11.11 applies) shall be deemed to involve (a) a
                -------------
distribution of such securities other than Common Stock to all holders of Common
Stock (and the effective date of such reclassification shall be deemed to be
"the date fixed for the determination of stockholders entitled to receive such
distribution" and "the date fixed for such determination" within the meaning of
paragraph (4) of this Section), and (b) a subdivision or combination, as the
case may be, of the number of shares of Common Stock outstanding immediately
prior to such reclassification into the number of shares of Common Stock
outstanding immediately thereafter (and the effective date of such
reclassification shall be deemed to be "the day upon which such subdivision
becomes effective" or "the day upon which such combination becomes effective",
as the case may be, and "the day upon which such subdivision or combination
becomes effective" within the meaning of paragraph (3) of this Section 11.4).
                                                               ------------

                                     -98-
<PAGE>

          (8)  For the purpose of any computation under paragraphs (2), (4), (5)
or (6) of this Section 11.4, the current market price per share of Common Stock
               ------------
on any date shall be calculated by the Company and be deemed to be the average
of the daily Closing Prices Per Share for the five consecutive Trading Days
selected by the Company commencing not more than 10 Trading Days before, and
ending not later than, the earlier of the day in question and the day before the
"ex" date with respect to the issuance or distribution requiring such
computation. For purposes of this paragraph, the term "`ex' date", when used
with respect to any issuance or distribution, means the first date on which the
Common Stock trades regular way in the applicable securities market or on the
applicable securities exchange without the right to receive such issuance or
distribution.

          (9)  No adjustment in the Conversion Rate shall be required unless
such adjustment (plus any adjustments not previously made by reason of this
paragraph (9)) would require an increase or decrease of at least one percent in
such rate; provided, however, that any adjustments which by reason of this
           --------  -------
paragraph (9) are not required to be made shall be carried forward and taken
into account in any subsequent adjustment. All calculations under this Article
shall be made to the nearest cent or to the nearest one-hundredth of a share, as
the case may be.

          (10) The Company may make such increases in the Conversion Rate, for
the remaining term of the Securities or any shorter term, in addition to those
required by paragraphs (1), (2), (3), (4), (5) and (6) of this Section 11.4, as
                                                               ------------
it considers to be advisable in order to avoid or diminish any income tax
liability to any holders of shares of Common Stock resulting from any dividend
or distribution of Common Stock or issuance of rights or warrants to purchase or
subscribe for Common Stock or from any event treated as such for income tax
purposes.

          To the extent permitted by applicable law, the Company from time to
time may increase the Conversion Rate by any amount for any period of time if
the period is at least twenty (20) days and the Board of Directors shall have
made a determination that such increase would be in the best interests of the
Company, which determination shall be conclusive; provided, however, that such
increase shall not be taken into account for purposes of determining whether the
Closing Price Per Share of the Common Stock exceeds the Conversion Price by 105%
in connection with an event which would otherwise be a Change in Control.
Whenever the Conversion Rate is increased pursuant to

                                     -99-
<PAGE>

the preceding sentence, the Company shall give notice of the increase to the
Holders of Securities in the manner provided in Section 1.6 at least fifteen
                                                -----------
(15) days prior to the date the increased Conversion Rate takes effect, and such
notice shall state the increased Conversion Rate and the period during which it
will be in effect.

          (11) Notwithstanding the foregoing provisions of this Section, no
     adjustment of the Conversion Rate shall be required to be made (a) upon the
     issuance of shares of Common Stock pursuant to any present or future plan
     for the reinvestment of dividends or (b) because of a tender or exchange
     offer of the character described in Rule 13e-4(h)(5) under the Exchange Act
     or any successor rule thereto.

SECTION 11.5   Notice of Adjustments of Conversion Rate.
               ----------------------------------------

          Whenever the Conversion Rate is adjusted as herein provided:

          (1)  the Company shall compute the adjusted Conversion Rate in
     accordance with Section 11.4 and shall prepare a certificate signed by the
                     ------------
     Chief Financial Officer of the Company setting forth the adjusted
     Conversion Rate and showing in reasonable detail the facts upon which such
     adjustment is based, and such certificate shall promptly be filed with the
     Trustee and with each Conversion Agent; and

          (2)  upon each such adjustment, a notice stating that the Conversion
     Rate has been adjusted and setting forth the adjusted Conversion Rate shall
     be required, and as soon as practicable after it is required, such notice
     shall be provided by the Company to all Holders in accordance with
     Section 1.6.
     -----------

Neither the Trustee nor any Conversion Agent shall be under any duty or
responsibility with respect to any such certificate or the information and
calculations contained therein, except to exhibit the same to any Holder of
Securities desiring inspection thereof at its office during normal business
hours.

SECTION 11.6   Notice of Certain Corporate Action.
               ----------------------------------

          In case:

          (a)  the Company shall declare a dividend (or any other distribution)
     on its Common Stock payable (i) otherwise than exclusively in cash or (ii)
     exclusively in

                                     -100-
<PAGE>

     cash in an amount that would require any adjustment pursuant to
     Section 11.4; or
     ------------

          (b) the Company shall authorize the granting to the holders of its
     Common Stock of rights, options or warrants to subscribe for or purchase
     any shares of capital stock of any class or of any other rights; or

          (c) of any reclassification of the Common Stock of the Company, or of
     any consolidation, merger or share exchange to which the Company is a party
     and for which approval of any stockholders of the Company is required, or
     of the conveyance, sale, transfer or lease of all or substantially all of
     the assets of the Company; or

          (d) of the voluntary or involuntary dissolution, liquidation or
     winding up of the Company;

then the Company shall cause to be filed at each office or agency maintained for
the purpose of conversion of Securities pursuant to Section 9.2, and shall cause
                                                    -----------
to be provided to all Holders in accordance with Section 1.6, at least 20 days
                                                 -----------
(or 10 days in any case specified in clause (a) or (b) above) prior to the
applicable record or effective date hereinafter specified, a notice stating (x)
the date on which a record is to be taken for the purpose of such dividend,
distribution, rights, options or warrants, or, if a record is not to be taken,
the date as of which the holders of Common Stock of record to be entitled to
such dividend, distribution, rights, options or warrants are to be determined or
(y) the date on which such reclassification, consolidation, merger, conveyance,
transfer, sale, lease, dissolution, liquidation or winding up is expected to
become effective, and the date as of which it is expected that holders of Common
Stock of record shall be entitled to exchange their shares of Common Stock for
securities, cash or other property deliverable upon such reclassification,
consolidation, merger, conveyance, transfer, sale, lease, dissolution,
liquidation or winding up.  Neither the failure to give such notice or the
notice referred to in the following paragraph nor any defect therein shall
affect the legality or validity of the proceedings described in clauses (a)
through (d) of this Section 11.6.  If at the time the Trustee shall not be the
                    ------------
Conversion Agent, a copy of such notice shall also forthwith be filed by the
Company with the Trustee.

          The Company shall cause to be filed at each office or agency
maintained for the purpose of conversion of Securities pursuant to Section 9.2,
                                                                   -----------
and shall cause to be provided to all

                                     -101-
<PAGE>

Holders in accordance with Section 1.6, notice of any tender offer by the
                           -----------
Company or any Subsidiary for all or any portion of the Common Stock at or about
the time that such notice of tender offer is provided to the public generally.

SECTION 11.7  Company to Reserve Common Stock.
              -------------------------------

          The Company shall at all times reserve and keep available, free from
preemptive rights, out of its authorized but unissued Common Stock, for the
purpose of effecting the conversion of Securities, the full number of shares of
Common Stock then issuable upon the conversion of all Outstanding Securities.

SECTION 11.8  Taxes on Conversions.
              --------------------

          Except as provided in the next sentence, the Company will pay any and
all taxes and duties that may be payable in respect of the issue or delivery of
shares of Common Stock on conversion of Securities pursuant hereto.  The Company
shall not, however, be required to pay any tax or duty which may be payable in
respect of any transfer involved in the issue and delivery of shares of Common
Stock in a name other than that of the Holder of the Security or Securities to
be converted, and no such issue or delivery shall be made unless and until the
Person requesting such issue has paid to the Company the amount of any such tax
or duty, or has established to the satisfaction of the Company that such tax or
duty has been paid.

SECTION 11.9  Covenant as to Common Stock.
              ---------------------------

          The Company agrees that all shares of Common Stock which may be
delivered upon conversion of Securities, upon such delivery, will be newly
issued shares and will have been duly authorized and validly issued and will be
fully paid and nonassessable and, except as provided in Section 11.8, the
                                                        ------------
Company will pay all taxes, liens and charges with respect to the issue thereof.

SECTION 11.10  Cancellation of Converted Securities.
               ------------------------------------

          All Securities delivered for conversion shall be delivered to the
Trustee or its agent to be canceled by or at the direction of the Trustee, which
shall dispose of the same as provided in Section 3.9.
                                         -----------

                                     -102-
<PAGE>

SECTION 11.11  Provision in Case of Consolidation, Merger or Sale of Assets.
               ------------------------------------------------------------

          In case of any consolidation or merger of the Company with or into any
other Person, any merger of another Person with or into the Company (other than
a merger which does not result in any reclassification, conversion, exchange or
cancellation of outstanding shares of Common Stock of the Company) or any
conveyance, sale, transfer or lease of all or substantially all of the assets of
the Company, the Person formed by such consolidation or resulting from such
merger or which acquires such assets, as the case may be, shall execute and
deliver to the Trustee a supplemental indenture providing that the Holder of
each Security then Outstanding shall have the right thereafter, during the
period such Security shall be convertible as specified in Section 11.1, to
                                                          ------------
convert such Security only into the kind and amount of securities, cash and
other property receivable upon such consolidation, merger, conveyance, sale,
transfer or lease by a holder of the number of shares of Common Stock of the
Company into which such Security might have been converted immediately prior to
such consolidation, merger, conveyance, sale, transfer or lease, assuming such
holder of Common Stock of the Company (i) is not a Person with which the Company
consolidated or merged with or into or which merged into or with the Company or
to which such conveyance, sale, transfer or lease was made, as the case may be
("Constituent Person"), or an Affiliate of a Constituent Person and (ii) failed
to exercise his rights of election, if any, as to the kind or amount of
securities, cash and other property receivable upon such consolidation, merger,
conveyance, sale, transfer or lease (provided that if the kind or amount of
securities, cash and other property receivable upon such consolidation, merger,
conveyance, sale, transfer, or lease is not the same for each share of Common
Stock of the Company held immediately prior to such consolidation, merger,
conveyance, sale, transfer or lease by others than a Constituent Person or an
Affiliate thereof and in respect of which such rights of election shall not have
been exercised ("Non-electing Share"), then for the purpose of this Section
                                                                    -------
11.11 the kind and amount of securities, cash and other property receivable upon
-----
such consolidation, merger, conveyance, sale, transfer or lease by the holders
of each Non-electing Share shall be deemed to be the kind and amount so
receivable per share by a plurality of the Non-electing Shares).  Such
supplemental indenture shall provide for adjustments which, for events
subsequent to the effective date of such supplemental indenture, shall be as
nearly equivalent as may be practicable to the adjustments provided for in this
Article.  The above

                                     -103-
<PAGE>

provisions of this Section 11.11 shall similarly apply to successive
                   -------------
consolidations, mergers, conveyances, sales, transfers or leases. Notice of the
execution of such a supplemental indenture shall be given by the Company to the
Holder of each Security as provided in Section 1.6 promptly upon such execution.
                                       -----------

          Neither the Trustee nor any Conversion Agent shall be under any
responsibility to determine the correctness of any provisions contained in any
such supplemental indenture relating either to the kind or amount of shares of
stock or other securities or property or cash receivable by Holders of
Securities upon the conversion of their Securities after any such consolidation,
merger, conveyance, transfer, sale or lease or to any such adjustment, but may
accept as conclusive evidence of the correctness of any such provisions, and
shall be protected in relying upon, an Officers Certificate or an Opinion of
Counsel with respect thereto, which the Company shall cause to be furnished to
the Trustee upon request.

SECTION 11.12  Responsibility of Trustee for Conversion Provisions.
               ---------------------------------------------------

          The Trustee, subject to the provisions of Section 6.1, and any
                                                    -----------
Conversion Agent shall not at any time be under any duty or responsibility to
any Holder of Securities to determine whether any facts exist which may require
any adjustment of the Conversion Rate, or with respect to the nature or extent
of any such adjustment when made, or with respect to the method employed, or
herein or in any supplemental indenture provided to be employed, in making the
same, or whether a supplemental indenture need be entered into.  Neither the
Trustee, subject to the provisions of Section 6.1, nor any Conversion Agent
                                      -----------
shall be accountable with respect to the validity or value (or the kind or
amount) of any Common Stock, or of any other securities or property or cash,
which may at any time be issued or delivered upon the conversion of any
Security; and it or they do not make any representation with respect thereto.
Neither the Trustee, subject to the provisions of Section 6.1, nor any
                                                  -----------
Conversion Agent shall be responsible for any failure of the Company to make or
calculate any cash payment or to issue, transfer or deliver any shares of Common
Stock or share certificates or other securities or property or cash upon the
surrender of any Security for the purpose of conversion; and the Trustee,
subject to the provisions of Section 6.1, and any Conversion Agent shall not be
                             -----------
responsible for any failure of the Company to comply with any of the covenants
of the Company contained in this Article.

                                     -104-
<PAGE>

                                ARTICLE TWELVE

                 REPURCHASE OF SECURITIES AT THE OPTION OF THE
                        HOLDER UPON A CHANGE IN CONTROL

SECTION 12.1  Right to Require Repurchase.
              ---------------------------

          In the event that a Change in Control (as hereinafter defined) shall
occur, then each Holder shall have the right, at the Holder's option, but
subject to the provisions of Section 12.2, to require the Company to repurchase,
                             ------------
and upon the exercise of such right the Company shall repurchase, all of such
Holder's Securities not theretofore called for redemption, or any portion of the
principal amount thereof that is equal to U.S.$5,000 or any greater integral
multiple of U.S.$1,000, on the date (the "Repurchase Date") that is 45 days
after the date of the Company Notice (as defined in Section 12.3) at a purchase
                                                    ------------
price equal to 100% of the principal amount of the Securities to be repurchased
plus interest accrued to the Repurchase Date (the "Repurchase Price"); provided,
                                                                       --------
however, that installments of interest on Securities whose Stated Maturity is on
-------
or prior to the Repurchase Date shall be payable to the Holders of such
Securities, or one or more Predecessor Securities, registered as such on the
relevant Record Date according to their terms and the provisions of Section 3.7.
                                                                    -----------
Such right to require the repurchase of the Securities shall not continue after
a discharge of the Company from its obligations with respect to the Securities
in accordance with Article Four, unless a Change in Control shall have occurred
                   ------------
prior to such discharge.  At the option of the Company, the Repurchase Price may
be paid in cash or, subject to the fulfillment by the Company of the conditions
set forth Section 12.2, by delivery of shares of Common Stock having a fair
          ------------
market value equal to the Repurchase Price.  Whenever in this Indenture
(including Sections 2.2, 3.1, 5.1(1) and 5.8) there is a reference, in any
           ------------  ---  ------     ---
context, to the principal of any Security as of any time, such reference shall
be deemed to include reference to the Repurchase Price payable in respect of
such Security to the extent that such Repurchase Price is, was or would be so
payable at such time, and express mention of the Repurchase Price in any
provision of this Indenture shall not be construed as excluding the Repurchase
Price in those provisions of this Indenture when such express mention is not
made.

                                     -105-
<PAGE>

SECTION 12.2  Conditions to the Company's Election to Pay the Repurchase Price
              ----------------------------------------------------------------
              in Common Stock.
              ---------------

          The Company may elect to pay the Repurchase Price by delivery of
shares of Common Stock pursuant to Section 12.1 if and only if the following
                                   ------------
conditions shall have been satisfied:

          (a)  The shares of Common Stock deliverable in payment of the
     Repurchase Price shall have a fair market value as of the Repurchase Date
     of not less than the Repurchase Price. For purposes of Section 12.1 and
                                                            ------------
     this Section 12.2, the fair market value of shares of Common Stock shall be
          ------------
     determined by the Company and shall be equal to 95% of the average of the
     Closing Price Per Share for the five consecutive Trading Days immediately
     preceding and including the third Trading Day prior to the Repurchase Date;

          (b)  As to each Holder, the Repurchase Price shall be paid only in
     cash in the event any shares of Common Stock to be issued upon repurchase
     of Securities hereunder (i) require registration under any federal
     securities law before such shares may be freely transferrable without being
     subject to any transfer restrictions under the Securities Act upon
     repurchase and if such registration is not completed or does not become
     effective prior to the Repurchase Date, and/or (ii) require registration
     with or approval of any governmental authority under any state law or any
     other federal law before such shares may be validly issued or delivered
     upon repurchase and if such registration is not completed or does not
     become effective or such approval is not obtained prior to the Repurchase
     Date;

          (c)  Payment of the Repurchase Price may not be made in Common Stock
     unless such stock is, or shall have been, approved for listing on the New
     York Stock Exchange or listed or quoted on a national securities exchange
     or quotation system, in either case, prior to the Repurchase Date; and

          (d)  All shares of Common Stock which may be issued upon repurchase of
     Securities will be issued out of the Company's authorized but unissued
     Common Stock and, will upon issue, be duly and validly issued and fully
     paid and non-assessable and free of any preemptive rights.

          If all of the conditions set forth in this Section 12.2 are not
                                                     ------------
satisfied in accordance with the terms thereof, the Repurchase Price shall be
paid by the Company only in cash.

                                     -106-
<PAGE>

SECTION 12.3   Notices; Method of Exercising Repurchase Right, Etc.
               ----------------------------------------------------

     (a)  Unless the Company shall have theretofore called for redemption all of
the Outstanding Securities, on or before the 30th day after the occurrence of a
Change in Control, the Company or, at the request and expense of the Company on
or before the 30th day after such occurrence, the Trustee, shall give to all
Holders of Securities, in the manner provided in Section 1.6, notice (the
                                                 -----------
"Company Notice") of the occurrence of the Change of Control and of the
repurchase right set forth herein arising as a result thereof. The Company shall
also deliver a copy of such notice of a repurchase right to the Trustee.

     Each notice of a repurchase right shall state:

     (1)  the Repurchase Date,

     (2)  the date by which the repurchase right must be exercised,

     (3)  the Repurchase Price, and whether the Repurchase Price shall be paid
  by the Company in cash or by delivery of shares of Common Stock,

     (4)  a description of the procedure which a Holder must follow to exercise
  a repurchase right, and the place or places where such Securities, are to be
  surrendered for payment of the Repurchase Price and accrued interest, if any,

     (5)  that on the Repurchase Date the Repurchase Price, and accrued
  interest, if any, will become due and payable upon each such Security
  designated by the Holder to be repurchased, and that interest thereon shall
  cease to accrue on and after said date,

     (6)  the Conversion Rate then in effect, the date on which the right to
  convert the principal amount of the Securities to be repurchased will
  terminate and the place or places where such Securities may be surrendered for
  conversion,

     (7)  the place or places that the Notice of Election of Holder To Require
  Repurchase as provided in Section 2.2 shall be delivered, and the form of such
                            -----------
  Notice, and

                                     -107-
<PAGE>

          (8)  the Cusip number or numbers of such Securities.

          No failure of the Company to give the foregoing notices or defect
therein shall limit any Holder's right to exercise a repurchase right or affect
the validity of the proceedings for the repurchase of Securities.

          If any of the foregoing provisions or other provisions of this Article
                                                                         -------
Twelve are inconsistent with applicable law, such law shall govern.
------

          (b)  To exercise a repurchase right, a Holder shall deliver to the
Trustee on or before the 30th day after the date of the Company Notice (i)
written notice of the Holder's exercise of such right, which notice shall set
forth the name of the Holder, the principal amount of the Securities to be
repurchased (and, if any Security is to repurchased in part, the serial number
thereof, the portion of the principal amount thereof to be repurchased and the
name of the Person in which the portion thereof to remain Outstanding after such
repurchase is to be registered) and a statement that an election to exercise the
repurchase right is being made thereby, and, in the event that the Repurchase
Price shall be paid in shares of Common Stock, the name or names (with
addresses) in which the certificate or certificates for shares of Common Stock
shall be issued, and (ii) the Securities with respect to which the repurchase
right is being exercised. Such written notice shall be irrevocable, except that
the right of the Holder to convert the Securities with respect to which the
repurchase right is being exercised shall continue until the close of business
on the Repurchase Date.

          (c)  In the event a repurchase right shall be exercised in accordance
with the terms hereof, the Company shall pay or cause to be paid to the Trustee
the Repurchase Price in cash or shares of Common Stock, as provided above, for
payment to the Holder on the Repurchase Date or, if shares of Common Stock are
to be paid, as promptly after the Repurchase Date as practicable, together with
accrued and unpaid interest to the Repurchase Date payable with respect to the
Securities as to which the purchase right has been exercised; provided, however,
                                                              --------  -------
that installments of interest that mature on or prior to the Repurchase Date
shall be payable in cash to the Holders of such Securities, or one or more
Predecessor Securities, registered as such at the close of business on the
relevant Regular Record Date.

                                     -108-
<PAGE>

          (d)  If any Security (or portion thereof) surrendered for repurchase
shall not be so paid on the Repurchase Date, the principal amount of such
Security (or portion thereof, as the case may be) shall, until paid, bear
interest to the extent permitted by applicable law from the Repurchase Date at
the rate of 4.50% per annum, and each Security shall remain convertible into
Common Stock until the principal of such Security (or portion thereof, as the
case may be) shall have been paid or duly provided for.

          (e)  Any Security which is to be repurchased only in part shall be
surrendered to the Trustee (with, if the Company or the Trustee so requires, due
endorsement by, or a written instrument of transfer in form satisfactory to the
Company and the Trustee duly executed by, the Holder thereof or his attorney
duly authorized in writing), and the Company shall execute, and the Trustee
shall authenticate and make available for delivery to the Holder of such
Security without service charge, a new Security or Securities, containing
identical terms and conditions, each in an authorized denomination in aggregate
principal amount equal to and in exchange for the unrepurchased portion of the
principal of the Security so surrendered.

          (f)  Any issuance of shares of Common Stock in respect of the
Repurchase Price shall be deemed to have been effected immediately prior to the
close of business on the Repurchase Date and the Person or Persons in whose name
or names any certificate or certificates for shares of Common Stock shall be
issuable upon such repurchase shall be deemed to have become on the Repurchase
Date the holder or holders of record of the shares represented thereby;
provided, however, that any surrender for repurchase on a date when the stock
--------  -------
transfer books of the Company shall be closed shall constitute the Person or
Persons in whose name or names the certificate or certificates for such shares
are to be issued as the record holder or holders thereof for all purposes at the
opening of business on the next succeeding day on which such stock transfer
books are open. No payment or adjustment shall be made for dividends or
distributions on any Common Stock issued upon repurchase of any Security
declared prior to the Repurchase Date.

          (g)  No fractions of shares shall be issued upon repurchase of
Securities. If more than one Security shall be repurchased from the same Holder
and the Repurchase Price shall be payable in shares of Common Stock, the number
of full shares which shall be issuable upon such repurchase shall be computed on
the basis of the aggregate principal amount of the Securities so repurchased.
Instead of any fractional share of Common Stock

                                     -109-
<PAGE>

which would otherwise be issuable on the repurchase of any Security or
Securities, the Company will deliver to the applicable Holder its check for the
current market value of such fractional share. The current market value of a
fraction of a share is determined by multiplying the current market price of a
full share by the fraction, and rounding the result to the nearest cent. For
purposes of this Section, the current market price of a share of Common Stock is
the Closing Price Per Share of the Common Stock on the Trading Day immediately
preceding the Repurchase Date.

          (h)  Any issuance and delivery of certificates for shares of Common
Stock on repurchase of Securities shall be made without charge to the Holder of
Securities being repurchased for such certificates or for any tax or duty in
respect of the issuance or delivery of such certificates or the securities
represented thereby; provided, however, that the Company shall not be required
                     --------  -------
to pay any tax or duty which may be payable in respect of (i) income of the
Holder or (ii) any transfer involved in the issuance or delivery of certificates
for shares of Common Stock in a name other than that of the Holder of the
Securities being repurchased, and no such issuance or delivery shall be made
unless and until the Person requesting such issuance or delivery has paid to the
Company the amount of any such tax or duty or has established, to the
satisfaction of the Company, that such tax or duty has been paid.

          (i)  All Securities delivered for repurchase shall be delivered to the
Trustee to be canceled at the direction of the Trustee, which shall dispose of
the same as provided in Section 3.9.
                        -----------

SECTION 12.4   Certain Definitions.
               -------------------

          For purposes of this Article Twelve,
                               --------------

          (a)  the term "beneficial owner" shall be determined in accordance
with Rule 13d-3, as in effect on the date of the original execution of this
Indenture, promulgated by the Commission pursuant to the Exchange Act;

          (b)  a "Change in Control" shall be deemed to have occurred at the
time, after the original issuance of the Securities, of:

          (i)       the acquisition by any person of beneficial ownership,
                    directly or indirectly, through a purchase, merger or other
                    acquisition

                                     -110-
<PAGE>

                    transaction or series of transactions, of shares of capital
                    stock of the Company entitling such person to exercise 50%
                    or more of the total voting power of all shares of capital
                    stock of the Company entitled to vote generally in the
                    elections of directors (any shares of voting stock of which
                    such person or group is the beneficial owner that are not
                    then outstanding being deemed outstanding for purposes of
                    calculating such percentage), other than any such
                    acquisition by the Company, any Subsidiary of the Company or
                    any employee benefit plan of the Company existing on the
                    date of this Indenture; or

          (ii)      any consolidation or merger of the Company with or into any
                    other person, or any merger of another person with or into
                    the Company(other than (a) any such transaction (x) which
                    does not result in any reclassification, conversion,
                    exchange or cancellation of outstanding shares of Common
                    Stock and (y) pursuant to which holders of Common Stock
                    immediately prior to such transaction have the entitlement
                    to exercise, directly or indirectly, 50% or more of the
                    total voting power of all shares of capital stock entitled
                    to vote generally in the election of directors of the
                    continuing or surviving person immediately after such
                    transaction and (b) any merger which is effected solely to
                    change the jurisdiction of incorporation of the Company and
                    results in a reclassification, conversion or exchange of
                    outstanding shares of Common Stock into solely shares of
                    common stock); or

          (iii)     any conveyance, transfer, sale, lease or similar disposition
                    of all or substantially all of the Company's assets to
                    another person;

provided, however, that a Change in Control shall not be deemed to have occurred
--------  -------
if the Closing Price Per Share on any five Trading Days within the period of 10
consecutive Trading Days ending immediately after the later of the date of the
Change in Control or the date of the public announcement of the Change in
Control (in the case of a Change in Control under Clause (i) above) or the
period of 10 consecutive Trading Days ending

                                     -111-
<PAGE>

immediately prior to the date of the Change in Control (in the case of a Change
in Control under Clause (ii) above) shall equal or exceed 105% of the Conversion
Price of the Securities in effect on each such Trading Day;

          (c)  the term "Conversion Price" shall equal U.S.$1,000 divided by the
Conversion Rate; and

          (d)  for purposes of Section 12.4(b)(i), the term "person" shall
                               ------------------
include any syndicate or group which would be deemed to be a "person" under
Section 13(d)(3) of the Exchange Act, as in effect on the date of the original
----------------
execution of this Indenture.

                               ARTICLE THIRTEEN

                           HOLDERS LISTS AND REPORTS
                     BY TRUSTEE AND COMPANY; NON-RECOURSE

SECTION 13.1   Company to Furnish Trustee Names and Addresses of Holders.
               ---------------------------------------------------------

          The Company will furnish or cause to be furnished to the Trustee:

          (a)  semi-annually, not more than 15 days after the Regular Record
     Date, a list, in such form as the Trustee may reasonably require, of the
     names and addresses of the Holders of Securities as of such Regular Record
     Date, and

          (b)  at such other times as the Trustee may reasonably request in
     writing, within 30 days after the receipt by the Company of any such
     request, a list of similar form and content as of a date not more than 15
     days prior to the time such list is furnished;

excluding from any such list names and addresses received by the Trustee in its
capacity as Security Registrar.

SECTION 13.2   Preservation of Information.
               ---------------------------

          (a)  The Trustee shall preserve, in as current a form as is reasonably
practicable, the names and addresses of Holders contained in the most recent
list furnished to the Trustee as provided in Section 13.1 and the names and
                                             ------------
addresses of Holders received by the Trustee in its capacity as Security
Registrar.

                                     -112-
<PAGE>

The Trustee may destroy any list furnished to it as provided in Section 13.1
                                                                ------------
upon receipt of a new list so furnished.

          (b)  After this Indenture has been qualified under the Trust Indenture
Act, the rights of Holders to communicate with other Holders with respect to
their rights under this Indenture or under the Securities, and the corresponding
rights and duties of the Trustee, shall be as provided by the Trust Indenture
Act.

          (c)  Every Holder of Securities, by receiving and holding the same,
agrees with the Company and the Trustee that neither the Company nor the Trustee
nor any agent of either of them shall be held accountable by reason of any
disclosure of information as to names and addresses of Holders made pursuant to
the Trust Indenture Act.

SECTION 13.3   No Recourse Against Others.
               --------------------------

          An incorporator or any past, present or future director, officer,
employee or stockholder, as such, of the Company shall not have any liability
for any obligations of the Company under the Securities or this Indenture or for
any claim based on, in respect of or by reason of such obligations or their
creation.  By accepting a Security, each Holder shall waive and release all such
liability.  Such waiver and release shall be part of the consideration for the
issue of the Securities.

SECTION 13.4   Reports by Trustee.
               ------------------

          (a)  After this Indenture has been qualified under the Trust Indenture
Act, the Trustee shall transmit to Holders such reports concerning the Trustee
and its actions under this Indenture as may be required pursuant to the Trust
Indenture Act at the times and in the manner provided pursuant thereto. If
required by Section 313(a) of the Trust Indenture Act, the Trustee shall, within
sixty days after each July 15 following the date of this Indenture, deliver to
Holders a brief report, dated as of such July 15, which complies with the
provisions of such Section 313(a).

          (b)  After this Indenture has been qualified under the Trust Indenture
Act, a copy of each such report shall, at the time of such transmission to
Holders, be filed by the Trustee with each stock exchange upon which the
Securities are listed, with the Commission and with the Company. The Company
will promptly notify the Trustee when the Securities are listed on any stock
exchange.

                                     -113-
<PAGE>

SECTION 13.5   Reports by Company.
               ------------------

          After this Indenture has been qualified under the Trust Indenture Act,
the Company shall file with the Trustee and the Commission, and transmit to
Holders, such information, documents and other reports, and such summaries
thereof, as may be required pursuant to the Trust Indenture Act at the times and
in the manner provided pursuant to such Act; provided that any such information,
documents or reports required to be filed with the Commission pursuant to
Section 13 or 15(d) of the Exchange Act shall be filed with the Trustee within
15 days after the same is so required to be filed with the Commission.

          Delivery of such reports, information and documents to the Trustee is
for informational purposes only and the Trustee's receipt thereof 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).

                             _____________________

          This instrument may be executed in any number of counterparts, each of
which so executed shall be deemed to be an original, but all such counterparts
shall together constitute but one and the same instrument.

                                     -114-
<PAGE>

          IN WITNESS WHEREOF, the parties hereto have caused this Indenture to
be duly executed, all as of the day and year first above written.

                              COR THERAPEUTICS, INC.


                              By /s/ Peter S. Roddy
                                -----------------------------
                              Name:  Peter S. Roddy
                              Title:  Vice President, Finance



                              FIRSTAR BANK, N.A., Trustee


                              By /s/ Frank P. Leslie
                                -----------------------------
                              Name:  Frank P. Leslie
                              Title:  Vice President

                                     -115-