<PAGE>

                                                                     Exhibit 4.5

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


                             BLACK HILLS CORPORATION

                                       AND

                      [___________________________________]
                                   AS TRUSTEE

                                    INDENTURE

                          DATED AS OF __________, 200__

                             SENIOR DEBT SECURITIES


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

<PAGE>

                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                               Page
                                                                                               ----
<S>            <C>                                                                               <C>

                                    ARTICLE I
                        DEFINITIONS AND OTHER PROVISIONS
                             OF GENERAL APPLICATION

SECTION 1.1    DEFINITIONS. ....................................................................  1
SECTION 1.2    COMPLIANCE CERTIFICATES AND OPINIONS.............................................  9
SECTION 1.3    FORM OF DOCUMENTS DELIVERED TO TRUSTEE .......................................... 10
SECTION 1.4    ACTS OF HOLDERS; RECORD DATES. .................................................. 10
SECTION 1.5    NOTICES, ETC., TO TRUSTEE AND COMPANY ........................................... 13
SECTION 1.6    NOTICE TO HOLDERS; WAIVER. ...................................................... 13
SECTION 1.7    CONFLICT WITH TRUST INDENTURE ACT ............................................... 14
SECTION 1.8    EFFECT OF HEADINGS AND TABLE OF CONTENTS......................................... 14
SECTION 1.9    SUCCESSORS AND ASSIGNS .......................................................... 14
SECTION 1.10   SEPARABILITY CLAUSE ............................................................. 14
SECTION 1.11   BENEFITS OF INDENTURE. .......................................................... 14
SECTION 1.12   GOVERNING LAW. .................................................................. 15
SECTION 1.13   LEGAL HOLIDAYS .................................................................. 15
SECTION 1.14   INDENTURE AND SECURITIES SOLELY CORPORATE OBLIGATIONS. .......................... 15
SECTION 1.15   INDENTURE MAY BE EXECUTED IN COUNTERPARTS........................................ 15

                                   ARTICLE II
                                 SECURITY FORMS

SECTION 2.1    FORMS GENERALLY ................................................................. 16
SECTION 2.2    FORM OF LEGEND FOR GLOBAL SECURITIES ............................................ 16
SECTION 2.3    FORM OF TRUSTEE'S CERTIFICATE OF AUTHENTICATION. ................................ 17
SECTION 2.4    FORM OF CONVERSION NOTICE........................................................ 17
</TABLE>

                                        i

<PAGE>

<TABLE>
<S>            <C>                                                                               <C>
                                   ARTICLE III
                                 THE SECURITIES

SECTION 3.1    AMOUNT UNLIMITED; ISSUABLE IN SERIES............................................. 18
SECTION 3.2    DENOMINATIONS.................................................................... 22
SECTION 3.3    EXECUTION, AUTHENTICATION, DELIVERY AND DATING................................... 22
SECTION 3.4    TEMPORARY SECURITIES ............................................................ 24
SECTION 3.5    REGISTRATION; REGISTRATION OF TRANSFER AND EXCHANGE. ............................ 25
SECTION 3.6    MUTILATED, DESTROYED, LOST AND STOLEN SECURITIES ................................ 27
SECTION 3.7    PAYMENT OF INTEREST; INTEREST RIGHTS PRESERVED .................................. 28
SECTION 3.8    PERSONS DEEMED OWNERS ........................................................... 30
SECTION 3.9    CANCELLATION. ................................................................... 30
SECTION 3.10   COMPUTATION OF INTEREST ......................................................... 30

                                   ARTICLE IV
                           SATISFACTION AND DISCHARGE

SECTION 4.1    SATISFACTION AND DISCHARGE OF INDENTURE ......................................... 30
SECTION 4.2    APPLICATION OF TRUST MONEY ...................................................... 32

                                    ARTICLE V
                                    REMEDIES

SECTION 5.1    EVENTS OF DEFAULT ............................................................... 32
SECTION 5.2    ACCELERATION OF MATURITY; RESCISSION AND ANNULMENT. ............................. 34
SECTION 5.3    COLLECTION OF INDEBTEDNESS AND SUITS FOR ENFORCEMENT BY TRUSTEE. ................ 35
SECTION 5.4    TRUSTEE MAY FILE PROOFS OF CLAIM ................................................ 36
SECTION 5.5    TRUSTEE MAY ENFORCE CLAIMS WITHOUT POSSESSION OF SECURITIES. .................... 36
SECTION 5.6    APPLICATION OF MONEY COLLECTED .................................................. 37
</TABLE>

                                       ii

<PAGE>

<TABLE>
<S>            <C>                                                                               <C>
SECTION 5.7    LIMITATION ON SUITS.............................................................. 37
SECTION 5.8    UNCONDITIONAL RIGHT OF HOLDERS TO RECEIVE PRINCIPAL,
                PREMIUM AND INTEREST AND TO CONVERT. ........................................... 38
SECTION 5.9    RESTORATION OF RIGHTS AND REMEDIES................................................38
SECTION 5.10   RIGHTS AND REMEDIES CUMULATIVE. ................................................. 38
SECTION 5.11   DELAY OR OMISSION NOT WAIVER. ................................................... 39
SECTION 5.12   CONTROL BY HOLDERS............................................................... 39
SECTION 5.13   WAIVER OF PAST DEFAULTS. ........................................................ 39
SECTION 5.14   UNDERTAKING FOR COSTS. .......................................................... 40
SECTION 5.15   WAIVER OF USURY, STAY OR EXTENSION LAWS ......................................... 40

                                   ARTICLE VI
                                   THE TRUSTEE

SECTION 6.1    CERTAIN DUTIES AND RESPONSIBILITIES. ............................................ 41
SECTION 6.2    NOTICE OF DEFAULTS............................................................... 41
SECTION 6.3    CERTAIN RIGHTS OF TRUSTEE ....................................................... 41
SECTION 6.4    NOT RESPONSIBLE FOR RECITALS OR ISSUANCE OF SECURITIES .......................... 43
SECTION 6.5    MAY HOLD SECURITIES AND ACT AS TRUSTEE UNDER OTHER INDENTURES.................... 43
SECTION 6.6    MONEY HELD IN TRUST ............................................................. 43
SECTION 6.7    COMPENSATION AND REIMBURSEMENT .................................................. 43
SECTION 6.8    CONFLICTING INTERESTS............................................................ 44
SECTION 6.9    CORPORATE TRUSTEE REQUIRED; ELIGIBILITY ......................................... 44
SECTION 6.10   RESIGNATION AND REMOVAL; APPOINTMENT OF SUCCESSOR ............................... 45
SECTION 6.11   ACCEPTANCE OF APPOINTMENT BY SUCCESSOR........................................... 46
SECTION 6.12   MERGER, CONVERSION, CONSOLIDATION OR SUCCESSION TO BUSINESS...................... 48
SECTION 6.13   PREFERENTIAL COLLECTION OF CLAIMS AGAINST COMPANY ............................... 48
SECTION 6.14   APPOINTMENT OF AUTHENTICATING AGENT.............................................. 48
</TABLE>

                                       iii

<PAGE>

<TABLE>
<S>            <C>                                                                               <C>
                                   ARTICLE VII
                HOLDERS' LISTS AND REPORTS BY TRUSTEE AND COMPANY

SECTION 7.1    COMPANY TO FURNISH TRUSTEE NAMES AND ADDRESSES OF HOLDERS ....................... 50
SECTION 7.2    PRESERVATION OF INFORMATION; COMMUNICATIONS TO HOLDERS........................... 50
SECTION 7.3    REPORTS BY TRUSTEE. ............................................................. 51
SECTION 7.4    REPORTS BY COMPANY .............................................................. 51

                                  ARTICLE VIII
              CONSOLIDATION, MERGER, CONVEYANCE, TRANSFER OR LEASE

SECTION 8.1    COMPANY MAY CONSOLIDATE, ETC., ONLY ON CERTAIN TERMS ............................ 52
SECTION 8.2    SUCCESSOR SUBSTITUTED............................................................ 53

                                   ARTICLE IX
                             SUPPLEMENTAL INDENTURES

SECTION 9.1    SUPPLEMENTAL INDENTURES WITHOUT CONSENT OF HOLDERS .............................. 53
SECTION 9.2    SUPPLEMENTAL INDENTURES WITH CONSENT OF HOLDERS. ................................ 55
SECTION 9.3    EXECUTION OF SUPPLEMENTAL INDENTURES............................................. 56
SECTION 9.4    EFFECT OF SUPPLEMENTAL INDENTURES................................................ 57
SECTION 9.5    CONFORMITY WITH TRUST INDENTURE ACT ............................................. 57
SECTION 9.6    REFERENCE IN SECURITIES TO SUPPLEMENTAL INDENTURES............................... 57

                                    ARTICLE X
                                    COVENANTS

SECTION 10.1   PAYMENT OF PRINCIPAL, PREMIUM AND INTEREST....................................... 57
SECTION 10.2   MAINTENANCE OF OFFICE OR AGENCY ................................................. 58
</TABLE>

                                       iv

<PAGE>

<TABLE>
<S>            <C>                                                                               <C>
SECTION 10.3   MONEY FOR SECURITIES PAYMENTS TO BE HELD IN TRUST ............................... 58
SECTION 10.4   STATEMENT BY OFFICERS AS TO DEFAULT ............................................. 60
SECTION 10.5   EXISTENCE........................................................................ 60
SECTION 10.6   WAIVER OF CERTAIN COVENANTS ..................................................... 60

                                   ARTICLE XI
                            REDEMPTION OF SECURITIES

SECTION 11.1   APPLICABILITY OF ARTICLE......................................................... 60
SECTION 11.2   ELECTION TO REDEEM; NOTICE TO TRUSTEE............................................ 61
SECTION 11.3   SELECTION BY TRUSTEE OF SECURITIES TO BE REDEEMED. .............................. 61
SECTION 11.4   NOTICE OF REDEMPTION. ........................................................... 62
SECTION 11.5   DEPOSIT OF REDEMPTION PRICE...................................................... 63
SECTION 11.6   SECURITIES PAYABLE ON REDEMPTION DATE............................................ 63
SECTION 11.7   SECURITIES REDEEMED IN PART...................................................... 64

                                   ARTICLE XII
                                  SINKING FUNDS

SECTION 12.1   APPLICABILITY OF ARTICLE ........................................................ 64
SECTION 12.2   SATISFACTION OF SINKING FUND PAYMENTS WITH SECURITIES. .......................... 65
SECTION 12.3   REDEMPTION OF SECURITIES FOR SINKING FUND ....................................... 65

                                  ARTICLE XIII
                       DEFEASANCE AND COVENANT DEFEASANCE

SECTION 13.1   COMPANY'S OPTION TO EFFECT DEFEASANCE OR COVENANT DEFEASANCE .................... 66
SECTION 13.2   DEFEASANCE AND DISCHARGE......................................................... 66
SECTION 13.3   COVENANT DEFEASANCE ............................................................. 67
SECTION 13.4   CONDITIONS TO DEFEASANCE OR COVENANT DEFEASANCE ................................. 68
</TABLE>

                                        v

<PAGE>

<TABLE>
<S>            <C>                                                                               <C>
SECTION 13.5   DEPOSITED MONEY AND U.S. GOVERNMENT OBLIGATIONS TO BE HELD IN TRUST;
                MISCELLANEOUS PROVISIONS ....................................................... 70
SECTION 13.6   REINSTATEMENT. .................................................................. 70

                                   ARTICLE XIV
                            CONVERSION OF SECURITIES

SECTION 14.1   APPLICABILITY OF ARTICLE ........................................................ 71
SECTION 14.2   EXERCISE OF CONVERSION PRIVILEGE ................................................ 71
SECTION 14.3   NO FRACTIONAL SHARES ............................................................ 72
SECTION 14.4   ADJUSTMENT OF CONVERSION PRICE .................................................. 73
SECTION 14.5   NOTICE OF CERTAIN CORPORATE ACTIONS ............................................. 74
SECTION 14.6   RESERVATION OF SHARES OF COMMON STOCK ........................................... 75
SECTION 14.7   PAYMENT OF CERTAIN TAXES UPON CONVERSION......................................... 75
SECTION 14.8   NONASSESSABILITY. ............................................................... 75
SECTION 14.9   PROVISION IN CASE OF CONSOLIDATION, MERGER OR SALE OF ASSETS. ................... 75
SECTION 14.10  DUTIES OF TRUSTEE REGARDING CONVERSION .......................................... 76
SECTION 14.11  REPAYMENT OF CERTAIN FUNDS UPON CONVERSION ...................................... 77
</TABLE>

                                       vi

<PAGE>

          INDENTURE, dated as of ___________, 200__, between Black Hills
Corporation, a corporation duly organized and existing under the laws of the
State of South Dakota (herein called the "Company"), having its principal
executive office at 625 Ninth Street, Rapid City, South Dakota 57701, and
[___________________], as Trustee (herein called the "Trustee").

                                   WITNESSETH:

          WHEREAS, the Company has duly authorized the execution and delivery of
this Indenture to provide for the issuance from time to time of its unsecured
debentures, notes or other evidences of indebtedness (herein called the
"Securities"), to be issued in one or more series as provided in this Indenture;
and

          WHEREAS, all things necessary to make this Indenture a valid agreement
of the Company, in accordance with its terms, have been done;

          NOW, THEREFORE, 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 or of
series thereof appertaining, as follows:

                                    ARTICLE I

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

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

                                        1

<PAGE>

               (3)  all accounting terms not otherwise defined herein have the
     meanings assigned to them in accordance with generally accepted accounting
     principles, 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;

               (4)  unless the context otherwise requires, any reference to an
     "Article" or a "Section" refers to an Article or a Section, as the case may
     be, of this Indenture; and

               (5)  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, 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.

          "Authenticating Agent" means any Person authorized by the Trustee
pursuant to Section 6.14 to act on behalf of the Trustee to authenticate
Securities of one or more series.

          "Board of Directors" means either the board of directors of the
Company or any duly authorized committee of that board empowered to act for it
with respect to this Indenture.

          "Board Resolution" means a copy of a resolution 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, and delivered to the Trustee.

          "Business Day," when used with respect to any Place of Payment, means
each Monday, Tuesday, Wednesday, Thursday and Friday which is not a day

                                        2

<PAGE>

on which banking institutions in that Place of Payment are authorized or
obligated by law or executive order to close.

          "Commission" means the Securities and Exchange Commission, 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" includes any stock of any class of the Company, which
has no preference in respect of dividends or of amounts payable in the event of
any voluntary or involuntary liquidation, dissolution or winding-up of the
Company and which is not subject to redemption by the Company; provided,
however, subject to the provisions of Section 14.9, shares issuable upon
conversion of Securities shall include only shares of the class designated as
Common Stock of the Company at the date of this Indenture or shares of any class
or classes resulting from any reclassification or reclassifications thereof and
which have no preference in respect of dividends or of amounts payable in the
event of any voluntary or involuntary liquidation, dissolution or winding-up of
the Company and which are not subject to redemption by the Company; provided,
further that if at any time there shall be more than one such resulting class,
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 corporation 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 Request" or "Company Order" means a written request or order
signed in the name of the Company by its Chairman of the Board, its President or
a Vice President, and by its principal financial officer, its Treasurer, an
Assistant Treasurer, its Secretary or an Assistant Secretary, and delivered to
the Trustee.

          "Constituent Person" has the meaning specified in Section 14.9.

          "Corporate Trust Office" means the corporate trust office of the
Trustee at [___________________________], Attention: Corporate Trust Department,
or such other office, designated by the Trustee by written notice to the
Company, at which at any particular time its corporate trust business shall be
administered.

                                        3

<PAGE>

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

          "Covenant Defeasance" has the meaning specified in Section 13.3.

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

          "Defeasance" has the meaning specified in Section 13.2.

          "Depositary" means, with respect to Securities of any series issuable
in whole or in part in the form of one or more Global Securities, a clearing
agency registered under the Exchange Act that is designated to act as Depositary
for such Securities as contemplated by Section 3.1.

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

          "Exchange Act" means the Securities Exchange Act of 1934 and any
statute successor thereto, in each case as amended from time to time.

          "Expiration Date" has the meaning specified in Section 1.4.

          "Global Security" means a Security that evidences all or part of the
Securities of any series and bears the legend set forth in Section 2.2 (or such
legend as may be specified as contemplated by Section 3.1 for such Securities).

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

          "Indenture" means this instrument as originally executed and 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. The term "Indenture" shall also include the terms of particular
series of Securities established as contemplated by Section 3.1; provided,
however, that if at any time more than one Person is acting as Trustee under
this Indenture due to the appointment of one or more separate Trustees for any
one or more separate series of Securities, "Indenture" shall mean, with respect
to such series of Securities for which any such Person is Trustee, 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 and shall include the terms of

                                        4

<PAGE>

particular series of Securities for which such Person is Trustee established as
contemplated by Section 3.1, exclusive, however, of any provisions or terms
which relate solely to other series of Securities for which such Person is not
Trustee, regardless of when such terms or provisions were adopted, and exclusive
of any provisions or terms adopted by means of one or more indentures
supplemental hereto executed and delivered after such Person had become such
Trustee, but to which such person, as such Trustee, was not a party; provided,
further that in the event that this Indenture is supplemented or amended by one
or more indentures supplemental hereto which are only applicable to certain
series of Securities, the term "Indenture" for a particular series of Securities
shall only include the supplemental indentures applicable thereto.

          "interest," when used with respect to an Original Issue Discount
Security which by its terms bears interest only after Maturity, means interest
payable after Maturity.

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

          "Investment Company Act" means the Investment Company Act of 1940 and
any statute successor thereto, in each case as amended from time to time.

          "Maturity," when used with respect to any Security, means the date on
which the principal of such Security or an installment of principal becomes due
and payable as therein or herein provided, whether at the Stated Maturity or by
declaration of acceleration, call for redemption or otherwise.

          "Notice of Default" means a written notice of the kind specified in
Section 5.1(4).

          "Officers' Certificate" means a certificate signed by the Chairman of
the Board, 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. One of the officers
signing an Officers' Certificate given pursuant to Section 10.4 shall be the
principal executive, financial or accounting officer of the Company.

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

                                        5

<PAGE>

          "Original Issue Discount Security" means any Security which provides
for an amount less than the principal amount thereof to be due and payable upon
a declaration of acceleration of the Maturity thereof pursuant to Section 5.2.

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

               (1)  Securities theretofore canceled by the Trustee or delivered
     to the Trustee for cancellation;

               (2)  Securities for whose payment or redemption 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;

               (3)  Securities as to which Defeasance has been effected pursuant
     to Section 13.2; and

               (4)  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 the Outstanding Securities have given, made or taken any
request, demand, authorization, direction, notice, consent, waiver or other
action hereunder as of any date, (A) the principal amount of an Original Issue
Discount Security which shall be deemed to be Outstanding shall be the amount of
the principal thereof which would be due and payable as of such date upon
acceleration of the Maturity thereof to such date pursuant to Section 5.2, (B)
if, as of such date, the principal amount payable at the Stated Maturity of a
Security is not determinable, the principal amount of such Security which shall
be deemed to be Outstanding shall be the amount as specified or determined as
contemplated by Section 3.1, (C) the principal amount of a Security denominated
in one or more foreign currencies or currency units which shall be

                                        6

<PAGE>

deemed to be Outstanding shall be the U.S. dollar equivalent, determined as of
such date in the manner provided as contemplated by Section 3.1, of the
principal amount of such Security (or, in the case of a Security described in
Clause (A) or (B) above, of the amount determined as provided in such Clause),
and (D) Securities owned by the Company or any other obligor upon the Securities
or any Affiliate of the Company or of 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 request, demand,
authorization, direction, notice, consent, waiver or other action, only
Securities which the Trustee 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 of such other obligor.

          "Paying Agent" means any Person authorized by the Company to pay the
principal of or any premium or interest on any Securities on behalf of the
Company.

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

          "Place of Payment," when used with respect to the Securities of any
series, means the place or places where the principal of and any premium and
interest on the Securities of that series are payable as specified as
contemplated by 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.

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

                                        7

<PAGE>

          "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.

          "Regular Record Date" for the interest payable on any Interest Payment
Date on the Securities of any series means the date specified for that purpose
as contemplated by Section 3.1.

          "Securities" has the meaning stated in the first recital of this
Indenture and more particularly means any Securities authenticated and delivered
under this Indenture.

          "Securities Act" means the Securities Act of 1933 and any statute
successor thereto, in each case as amended from time to time.

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

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

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

          "Subsidiary" means, with respect to any Person, (i) any corporation or
trust of which a majority of the outstanding voting securities is at the time,
and (ii) any partnership of which a majority of the equity capital or profit
interest is at the time, owned, directly or indirectly, by the Company, by one
or more other Subsidiaries or by the Company and one or more Subsidiaries. For
the purposes of this definition, "voting securities" means securities which
ordinarily have voting power for the election of directors, whether at all times
or only so long as no senior class of securities has such voting power by reason
of any contingency.

          "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.

          "Trustee" means the Person named as the "Trustee" in the first
paragraph of this instrument until a successor Trustee shall have become such

                                        8

<PAGE>

pursuant to the applicable provisions of this Indenture, and thereafter
"Trustee" shall mean or include each Person who is then a Trustee hereunder, and
if at any time there is more than one such Person, "Trustee" as used with
respect to the Securities of any series shall mean the Trustee with respect to
Securities of that series.

          "U.S. Government Obligation" has the meaning specified in Section
13.4.

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

SECTION 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 such certificates and opinions as may be required under the Trust
Indenture Act. Each such certificate or opinion shall be given in the form of an
Officers' Certificate, if to be given by an officer of the Company, or an
Opinion of Counsel, if to be given by counsel, and shall comply with the
requirements of the Trust Indenture Act and any other requirements set forth in
this Indenture.

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

               (1)  a statement that each individual signing such certificate or
     opinion has read such 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 or opinions
     contained in such certificate or opinion are based;

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

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

                                        9

<PAGE>

SECTION 1.3   FORM OF DOCUMENTS DELIVERED TO TRUSTEE.

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

          Any certificate or opinion of an officer of the Company 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 his or her 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 stating that the
information with respect to such factual matters is in the possession of the
Company, 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.

SECTION 1.4   ACTS OF HOLDERS; RECORD DATES.

          Any request, demand, authorization, direction, notice, consent, waiver
or other action provided or permitted by this Indenture to be given, made or
taken by Holders may be embodied in and evidenced by one or more instruments of
substantially similar tenor signed by such Holders in person or by agent duly
appointed in writing; and, except as herein otherwise expressly provided, such
action shall become effective when such instrument or instruments are 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 instrument or
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 signing such instrument or instruments. Proof of
execution of any such instrument or of a writing appointing any such agent shall
be sufficient for any

                                       10

<PAGE>

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.

          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 or her the execution thereof.
Where such execution is by a signer acting in a capacity other than his or her
individual capacity, such certificate or affidavit shall also constitute
sufficient proof of his or her authority. The fact and date of the execution of
any such instrument or writing, or the authority of the Person executing the
same, may also be proved in any other manner which the Trustee deems sufficient.

          The ownership of Securities shall be proved by the Security Register.

          Any request, demand, authorization, direction, notice, consent, 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.

          The Company may set any day as a record date for the purpose of
determining the Holders of Outstanding Securities of any series entitled to
give, make or take any request, demand, authorization, direction, vote, notice,
consent, waiver or other action provided or permitted by this Indenture to be
given, made or taken by Holders of Securities of such series, provided that the
Company may not set a record date for, and the provisions of this paragraph
shall not apply with respect to, the giving or making of any notice,
declaration, request or direction referred to in the next paragraph. If any
record date is set pursuant to this paragraph, the Holders of Outstanding
Securities of the relevant series on such record date, and no other Holders,
shall be entitled to take the relevant action, whether or not such Holders
remain Holders after such record date; provided that no such action shall be
effective hereunder unless taken on or prior to the applicable Expiration Date
by Holders of the requisite principal amount of Outstanding Securities of such
series on such record date. Nothing in this paragraph shall be construed to
prevent the Company from setting a new record date for any action for which a
record date has previously been set pursuant to this paragraph (whereupon the
record date previously set shall automatically and with no action by any Person
be canceled and of no effect), and nothing in this paragraph shall be construed
to render ineffective any action taken by Holders of the requisite principal
amount of Outstanding Securities of the relevant

                                       11

<PAGE>

series on the date such action is taken. Promptly after any record date is set
pursuant to this paragraph, the Company, at its own expense, shall cause notice
of such record date, the proposed action by Holders and the applicable
Expiration Date to be given to the Trustee in writing and to each Holder of
Securities of the relevant series in the manner set forth in Section 1.6.

          The Trustee may set any day as a record date for the purpose of
determining the Holders of Outstanding Securities of any series entitled to join
in the giving or making of (i) any Notice of Default, (ii) any declaration of
acceleration referred to in Section 5.2, (iii) any request to institute
proceedings referred to in Section 5.7(2) or (iv) any direction referred to in
Section 5.12, in each case with respect to Securities of such series. If any
record date is set pursuant to this paragraph, the Holders of Outstanding
Securities of such series on such record date, and no other Holders, shall be
entitled to join in such notice, declaration, request or direction, whether or
not such Holders remain Holders after such record date; provided that no such
action shall be effective hereunder unless taken on or prior to the applicable
Expiration Date by Holders of the requisite principal amount of Outstanding
Securities of such series on such record date. Nothing in this paragraph shall
be construed to prevent the Trustee from setting a new record date for any
action for which a record date has previously been set pursuant to this
paragraph (whereupon the record date previously set shall automatically and with
no action by any Person be canceled and of no effect), and nothing in this
paragraph shall be construed to render ineffective any action taken by Holders
of the requisite principal amount of Outstanding Securities of the relevant
series on the date such action is taken. Promptly after any record date is set
pursuant to this paragraph, the Trustee, at the Company's expense, shall cause
notice of such record date, the proposed action by Holders and the applicable
Expiration Date to be given to the Company in writing and to each Holder of
Securities of the relevant series in the manner set forth in Section 1.6.

          With respect to any record date set pursuant to this Section, the
party hereto which sets such record dates may designate any day as the
"Expiration Date" and from time to time may change the Expiration Date to any
earlier or later day; provided that no such change shall be effective unless
notice of the proposed new Expiration Date is given to the other party hereto in
writing, and to each Holder of Securities of the relevant series in the manner
set forth in Section 1.6, on or prior to the existing Expiration Date. If an
Expiration Date is not designated with respect to any record date set pursuant
to this Section, the party hereto which set such record date shall be deemed to
have initially designated the 180th day after such record date as the Expiration
Date with respect thereto, subject to its right to change the Expiration Date as
provided in this paragraph. Notwithstanding the foregoing, no Expiration Date
shall be later than the 180th day after the applicable record date.

                                       12

<PAGE>

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

SECTION 1.5   NOTICES, ETC., TO TRUSTEE AND COMPANY.

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

               (1)  the Trustee by any Holder or by the Company shall be
     sufficient for every purpose hereunder if made, given, furnished or filed
     in writing (or by facsimile transmissions, provided that oral confirmation
     of receipt shall have been received) to or with the Trustee at its
     Corporate Trust Office, Attention: Corporate Trust Department, or

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

SECTION 1.6   NOTICE TO HOLDERS; WAIVER.

          Where this Indenture provides for notice to Holders of any event, such
notice shall be sufficiently given (unless otherwise herein expressly provided)
if in writing and mailed, first-class postage prepaid, or delivered by hand or
overnight courier to each Holder affected by such event, at its address as it
appears in the Security Register, not later than the latest date (if any), and
not earlier than the earliest date (if any), prescribed for the giving of such
notice. Neither the failure to mail or deliver by hand or overnight courier any
such notice, nor any defect in any such notice so mailed or delivered by hand or
overnight courier, to any particular Holder shall affect the sufficiency of such
notice with respect to other Holders. 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

                                       13

<PAGE>

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.

          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 as shall be made with the approval of the Trustee shall
constitute a sufficient notification for every purpose hereunder.

SECTION 1.7   CONFLICT WITH TRUST INDENTURE ACT.

          If any provision hereof limits, qualifies or conflicts with a
provision of the Trust Indenture Act which 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 which 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.

SECTION 1.8   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 1.9   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 1.10  SEPARABILITY CLAUSE.

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

SECTION 1.11  BENEFITS OF INDENTURE.

          Nothing in this Indenture or in the Securities, express or implied,
shall give to any Person, other than the parties hereto and their successors
hereunder and the Holders, any benefit or any legal or equitable right, remedy
or claim under this Indenture.

                                       14

<PAGE>

SECTION 1.12  GOVERNING LAW.

          THIS INDENTURE AND THE SECURITIES SHALL BE GOVERNED BY AND CONSTRUED
IN ACCORDANCE WITH THE LAW OF THE STATE OF NEW YORK, WITHOUT GIVING EFFECT TO
SUCH STATE'S CONFLICTS OF LAWS PRINCIPLES.

SECTION 1.13  LEGAL HOLIDAYS.

          In any case where any Interest Payment Date, Redemption Date or Stated
Maturity of any Security or the last date on which a Holder has the right to
convert a Security at a particular conversion price shall not be a Business Day
at any Place of Payment, then (notwithstanding any other provision of this
Indenture or of the Securities (other than a provision of any Security which
specifically states that such provision shall apply in lieu of this Section))
payment of interest or principal (and premium, if any) or, if applicable to a
particular series of Securities, conversion need not be made at such Place of
Payment on such date, but may be made on the next succeeding Business Day at
such Place of Payment with the same force and effect as if made on the Interest
Payment Date or Redemption Date, at the Stated Maturity or on such last day for
conversion, as the case may be.

SECTION 1.14  INDENTURE AND SECURITIES SOLELY CORPORATE OBLIGATIONS.

          No recourse for the payment of the principal of or premium, if any, or
interest on any Security, or for any claim based thereon or otherwise in respect
thereof, and no recourse under or upon any obligation, covenant or agreement of
the Company in this Indenture or in any supplemental indenture or in any
Security, or because of the creation of any indebtedness represented thereby,
shall be had against any incorporator, stockholder, employee, agent, officer, or
director or subsidiary, as such, past, present or future, of the Company or of
any successor corporation, either directly or through the Company or any
successor corporation, whether by virtue of any constitution, statute or rule of
law, or by the enforcement of any assessment or penalty or otherwise; it being
expressly understood that all such liability is hereby expressly waived and
released as a condition of, and as a consideration for, the execution of this
Indenture and the issue of the Securities.

SECTION 1.15  INDENTURE MAY BE EXECUTED IN COUNTERPARTS.

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

                                       15

<PAGE>

                                   ARTICLE II

                                 SECURITY FORMS

SECTION 2.1   FORMS GENERALLY.

          The Securities of each series shall be in substantially the form set
forth in this Article, or in such other form as shall be established by or
pursuant to a Board Resolution or in one or more indentures supplemental hereto,
in each case with such appropriate insertions, omissions, substitutions and
other variations as are required or permitted by this Indenture, and may have
such letters, numbers or other marks of identification and such legends or
endorsements placed thereon as may be required to comply with the rules of any
securities exchange or Depositary therefor or as may, consistently herewith, be
determined by the officers executing such Securities, as evidenced by their
execution thereof. If the form of Securities of any series is established by
action taken pursuant to a Board Resolution, a copy of an appropriate record of
such action shall be certified by the Secretary or an Assistant Secretary of the
Company and delivered to the Trustee at or prior to the delivery of the Company
Order contemplated by Section 3.3 for the authentication and delivery of such
Securities. Any such Board Resolution or record of such action shall have
attached thereto a true and correct copy of the form of Security referred to
therein approved by or pursuant to such Board Resolution.

SECTION 2.2   FORM OF LEGEND FOR GLOBAL SECURITIES.

          Unless otherwise specified as contemplated by Section 3.1 for the
Securities evidenced thereby, every Global Security authenticated and delivered
hereunder shall bear a legend in substantially the following form:

          THIS SECURITY IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE
HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITARY OR A
NOMINEE THEREOF. THIS SECURITY MAY NOT BE EXCHANGED IN WHOLE OR IN PART FOR A
SECURITY REGISTERED, AND NO TRANSFER OF THIS SECURITY IN WHOLE OR IN PART MAY BE
REGISTERED, IN THE NAME OF ANY PERSON OTHER THAN SUCH DEPOSITARY OR A NOMINEE
THEREOF, EXCEPT IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE.

                                       16

<PAGE>

SECTION 2.3   FORM OF TRUSTEE'S CERTIFICATE OF AUTHENTICATION.

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

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

                            [_____________________],
                              as Trustee


                            By:
                               ------------------------
                                  Authorized Officer

SECTION 2.4   FORM OF CONVERSION NOTICE.

          Conversion notices shall be in substantially the following form:

To Black Hills Corporation:

          The undersigned owner of this Security hereby irrevocably exercises
the option to convert this Security, or portion hereof (which is $1,000 or an
integral multiple thereof) below designated, into shares of Common Stock of the
Company in accordance with the terms of the Indenture referred to in this
Security, and directs that the shares issuable and deliverable upon the
conversion, together with any check in payment for fractional shares and any
Securities representing any unconverted principal amount hereof, be issued and
delivered to the registered holder hereof unless a different name has been
indicated below. If this Notice is being delivered on a date after the close of
business on a Regular Record Date and prior to the opening of business on the
related Interest Payment Date (unless this Security or the portion thereof being
converted has been called for redemption on a Redemption Date during the period
beginning at the close of business on a Regular Record Date and ending at the
opening of business on the first Business Day after the next succeeding Interest
Payment Date, or if such Interest Payment Date is not a Business Day, the second
such Business Day), this Notice is accompanied by payment, in funds acceptable
to the Company, of an amount equal to the interest payable on such Interest
Payment Date of the principal of this Security to be converted. If shares are to
be issued in the name of a person other than the undersigned, the undersigned
will pay all transfer taxes payable with respect hereto. Any amount required to
be paid by the undersigned on account of interest accompanies this Security.

                                       17

<PAGE>

                Principal Amount to be Converted
      (in an integral multiple of $1,000, if less than all)

U.S. $_____________
Dated:  ____________
                                    Signature(s) must be guaranteed by an
                                    eligible guarantor institution (banks, stock
                                    brokers, savings and loan associations and
                                    credit unions with membership in an approved
                                    signature guarantee medallion program)
                                    pursuant to Securities and Exchange
                                    Commission Rule 17Ad-15.

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

          Fill in for registration of shares of Common Stock and Security if to
be issued otherwise than to the registered Holder.


-------------------------           ----------------------------------------
(Name)                              Social Security or Other Taxpayer
                                    Identification Number

-------------------------
(Address)


---------------------------------
Please print Name and Address
(including zip code number)

[The above conversion notice is to be modified, as appropriate, for conversion
into other securities or property of the Company.]

                                   ARTICLE III

                                 THE SECURITIES

SECTION 3.1   AMOUNT UNLIMITED; ISSUABLE IN SERIES.

          The aggregate principal amount of Securities which may be
authenticated and delivered under this Indenture is unlimited.

                                       18

<PAGE>

          The Securities may be issued in one or more series. There shall be
established in or pursuant to a Board Resolution and, subject to Section 3.3,
set forth, or determined in the manner provided, in an Officers' Certificate, or
established in one or more indentures supplemental hereto, prior to the issuance
of Securities of any series,

               (1)  the title of the Securities of the series (which shall
     distinguish the Securities of the series from Securities of any other
     series);

               (2)  any limit upon the aggregate principal amount of the
     Securities of the series which may be authenticated and delivered under
     this Indenture (except for Securities authenticated and delivered upon
     registration of transfer of, or in exchange for, or in lieu of, other
     Securities of the series pursuant to Section 3.4, 3.5, 3.6, 9.6 or 11.7 and
     except for any Securities which, pursuant to Section 3.3, are deemed never
     to have been authenticated and delivered hereunder);

               (3)  the Person to whom any interest on a Security of the series
     shall be payable, if other than 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;

               (4)  the date or dates on which the principal of any Securities
     of the series is payable;

               (5)  the rate or rates at which any Securities of the series
     shall bear interest, if any, the date or dates from which any such interest
     shall accrue, the Interest Payment Dates on which any such interest shall
     be payable and the Regular Record Date for any such interest payable on any
     Interest Payment Date;

               (6)  the place or places where the principal of and any premium
     and interest on any Securities of the series shall be payable;

               (7)  the period or periods within which, the price or prices at
     which and the terms and conditions upon which any Securities of the series
     may be redeemed, in whole or in part, at the option of the Company and, if
     other than by a Board Resolution, the

                                       19

<PAGE>

     manner in which any election by the Company to redeem the Securities shall
     be evidenced;

               (8)  the obligation, if any, of the Company to redeem or purchase
     any Securities of the series pursuant to any sinking fund or analogous
     provisions or at the option of the Holder thereof and the period or periods
     within which, the price or prices at which and the terms and conditions
     upon which any Securities of the series shall be redeemed or purchased, in
     whole or in part, pursuant to such obligation;

               (9)  if other than denominations of $1,000 and any integral
     multiple thereof, the denominations in which any Securities of the series
     shall be issuable;

               (10) if the amount of principal of or any premium or interest on
     any Securities of the series may be determined with reference to an index
     or pursuant to a formula, the manner in which such amounts shall be
     determined;

               (11) if other than the currency of the United States of America,
     the currency, currencies or currency units in which the principal of or any
     premium or interest on any Securities of the series shall be payable and
     the manner of determining the equivalent thereof in the currency of the
     United States of America for any purpose, including for purposes of the
     definition of "Outstanding" in Section 1.1;

               (12) if the principal of or any premium or interest on any
     Securities of the series is to be payable, at the election of the Company
     or the Holder thereof, in one or more currencies or currency units other
     than that or those in which such Securities are stated to be payable, the
     currency, currencies or currency units in which the principal of or any
     premium or interest on such Securities as to which such election is made
     shall be payable, the periods within which and the terms and conditions
     upon which such election is to be made and the amount so payable (or the
     manner in which such amount shall be determined);

               (13) if other than the entire principal amount thereof, the
     portion of the principal amount of any Securities of the series

                                       20

<PAGE>

     which shall be payable upon declaration of acceleration of the Maturity
     thereof pursuant to Section 5.2;

               (14) if the principal amount payable at the Stated Maturity of
     any Securities of the series will not be determinable as of any one or more
     dates prior to the Stated Maturity, the amount which shall be deemed to be
     the principal amount of such Securities as of any such date for any purpose
     thereunder or hereunder, including the principal amount thereof which shall
     be due and payable upon any Maturity other than the Stated Maturity or
     which shall be deemed to be Outstanding as of any date prior to the Stated
     Maturity (or, in any such case, the manner in which such amount deemed to
     be the principal amount shall be determined);

               (15) if applicable, that the Securities of the series, in whole
     or any specified part, shall be defeasible pursuant to Section 13.2 or
     Section 13.3 or both such Sections and, if other than by a Board
     Resolution, the manner in which any election by the Company to defease such
     Securities shall be evidenced;

               (16) if applicable, the terms of any right to convert Securities
     of the series into shares of Common Stock of the Company or other
     securities or property;

               (17) if applicable, that any Securities of the series shall be
     issuable in whole or in part in the form of one or more Global Securities
     and, in such case, the respective Depositaries for such Global Securities,
     the form of any legend or legends which shall be borne by any such Global
     Security in addition to or in lieu of that set forth in Section 2.2 and any
     circumstances in addition to or in lieu of those set forth in Clause (2) of
     the last paragraph of Section 3.5 in which any such Global Security may be
     exchanged in whole or in part for Securities registered, and any transfer
     of such Global Security in whole or in part may be registered, in the name
     or names of Persons other than the Depositary for such Global Security or a
     nominee thereof;

               (18) any addition to or change in the Events of Default which
     applies to any Securities of the series and any change in the right of the
     Trustee or the requisite Holders of such Securities to declare the
     principal amount thereof due and payable pursuant to Section 5.2;

                                       21

<PAGE>

               (19) any addition to or change in the covenants set forth in
     Article 10 which applies to Securities of the series; and

               (20) any other terms of the series (which terms shall not be
     inconsistent with the provisions of this Indenture, except as permitted by
     Section 9.1(5)).

          All Securities of any one series shall be substantially identical
except as to denomination and except as may otherwise be provided in or pursuant
to the Board Resolution referred to above and (subject to Section 3.3) set
forth, or determined in the manner provided, in the Officers' Certificate
referred to above or in any such indenture supplemental hereto.

          If any of the terms of the series are established by action taken
pursuant to a Board Resolution, a copy of an appropriate record of such action
shall be certified by the Secretary or an Assistant Secretary of the Company and
delivered to the Trustee at or prior to the delivery of the Officers'
Certificate setting forth the terms of the series.

SECTION 3.2   DENOMINATIONS.

          The Securities of each series shall be issuable only in registered
form without coupons and only in such denominations as shall be specified as
contemplated by Section 3.1. In the absence of any such specified denomination
with respect to the Securities of any series, the Securities of such series
shall be issuable in denominations of $1,000 and any integral multiple 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 Chief Executive Officer, its principal financial
officer, its President or one of its Vice Presidents, attested by its Treasurer,
Secretary or one of its Assistant Treasurers or Assistant Secretaries. The
signature of any of these officers on the Securities may be manual or facsimile.

          Securities bearing the manual or facsimile signatures 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.

                                       22

<PAGE>

          At any time and from time to time after the execution and delivery of
this Indenture, the Company may deliver Securities of any series executed by the
Company to the Trustee for authentication, together with a Company Order for the
authentication and delivery of such Securities, and the Trustee in accordance
with the Company Order shall authenticate and deliver such Securities. If the
form or terms of the Securities of the series have been established by or
pursuant to one or more Board Resolutions as permitted by Sections 2.1 and 3.1,
in authenticating such Securities, and accepting the additional responsibilities
under this Indenture in relation to such Securities, the Trustee shall be
entitled to receive, and (subject to Section 6.1) shall be fully protected in
relying upon, a copy of such Board Resolution, the Officers' Certificate setting
forth the terms of the series and an Opinion of Counsel, with such Opinion of
Counsel stating,

               (1)  if the form of such Securities has been established by or
     pursuant to Board Resolution as permitted by Section 2.1, that such form
     has been established in conformity with the provisions of this Indenture;

               (2)  if the terms of such Securities have been established by or
     pursuant to Board Resolution as permitted by Section 3.1, that such terms
     have been established in conformity with the provisions of this Indenture;
     and

               (3)  that such Securities, when authenticated and delivered by
     the Trustee and issued by the Company in the manner and subject to any
     conditions specified in such Opinion of Counsel, will constitute valid and
     legally binding obligations of the Company enforceable in accordance with
     their terms, subject to bankruptcy, insolvency, fraudulent transfer,
     reorganization, moratorium and similar laws of general applicability
     relating to or affecting creditors' rights and to general equity
     principles.

          If such form or terms have been so established, the Trustee shall not
be required to authenticate such Securities if the issue of such Securities
pursuant to this Indenture will affect the Trustee's own rights, duties or
immunities under the Securities and this Indenture or otherwise in a manner
which is not reasonably acceptable to the Trustee.

          Notwithstanding the provisions of Section 3.1 and of the preceding
paragraph, if all Securities of a series are not to be originally issued at one
time, it shall not be necessary to deliver the Officers' Certificate otherwise
required pursuant to Section 3.1 or the Company Order and Opinion of Counsel
otherwise required

                                       23

<PAGE>

pursuant to such preceding paragraph at or prior to the authentication of each
Security of such series if such documents are delivered at or prior to the
authentication upon original issuance of the first Security of such series to be
issued.

          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, and such certificate upon any
Security shall be conclusive evidence, and the only evidence, that such Security
has been duly authenticated and delivered hereunder. Notwithstanding the
foregoing, if any Security shall have been authenticated and delivered hereunder
but never issued and sold by the Company, and the Company shall deliver such
Security to the Trustee for cancellation as provided in Section 3.9, for all
purposes of this Indenture such Security shall be deemed never to have been
authenticated and delivered hereunder and shall never be entitled to the
benefits of this Indenture.

          Neither the Company nor the Trustee shall have any responsibility for
any defect in the CUSIP number that appears on any Security, check, advice of
payment or redemption notice, and any such document may contain a statement to
the effect that CUSIP numbers have been assigned by an independent service for
convenience of reference and that neither the Company nor the Trustee shall be
liable for any inaccuracy in such numbers.

SECTION 3.4   TEMPORARY SECURITIES.

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

          If temporary Securities of any series are issued, the Company will
cause definitive Securities of that series to be prepared without unreasonable
delay. After the preparation of definitive Securities of such series, the
temporary Securities of such series shall be exchangeable for definitive
Securities of such series upon surrender of the temporary Securities of such
series at the office or agency of the Company in a Place of Payment for that
series, without charge to the Holder. Upon

                                       24

<PAGE>

surrender for cancellation of any one or more temporary Securities of any
series, the Company shall execute and the Trustee shall authenticate and deliver
in exchange therefor one or more definitive Securities of the same series, of
any authorized denominations and of like tenor and aggregate principal amount.
Until so exchanged, the temporary Securities of any series shall in all respects
be entitled to the same benefits under this Indenture as definitive Securities
of such series and tenor.

SECTION 3.5   REGISTRATION; REGISTRATION OF TRANSFER AND EXCHANGE.

          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 in a Place of Payment 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 Securities and of transfers of Securities. The Trustee is hereby
appointed "Security Registrar" for the purpose of registering Securities and
transfers of Securities as herein provided.

          Upon surrender for registration of transfer of any Security of a
series at the office or agency of the Company in a Place of Payment for that
series, the Company shall execute, and the Trustee shall authenticate and
deliver, in the name of the designated transferee or transferees, one or more
new Securities of the same series, of any authorized denominations and of like
tenor and aggregate principal amount.

          At the option of the Holder, Securities of any series may be exchanged
for other Securities of the same series, of any authorized denominations and of
like tenor and aggregate principal amount, upon surrender of the Securities to
be exchanged at such office or agency. Whenever any Securities are so
surrendered for exchange, the Company shall execute, and the Trustee shall
authenticate and deliver, the Securities which the Holder making the exchange is
entitled to receive.

          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 entitled to the same benefits under this Indenture, as the Securities
surrendered upon such registration of transfer or exchange.

          Every Security presented or surrendered for registration of transfer
or for exchange shall (if so required by the Company or the Trustee) 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 its attorney duly authorized in writing.

                                       25

<PAGE>

          No service charge shall be made for any registration of transfer or
exchange of Securities, 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, 9.6 or 11.7 not involving any transfer.

          If the Securities of any series (or of any series and specified tenor)
are to be redeemed in part, the Company shall not be required (A) to issue,
register the transfer of or exchange any Securities of that series (or of that
series and specified tenor, as the case may be) during a period beginning at the
opening of business 15 days before the day of the mailing of a notice of
redemption of any such Securities selected for redemption under Section 11.3 and
ending at the close of business on the day of such mailing, or (B) to register
the transfer of or exchange any Security so selected for redemption in whole or
in part, except the unredeemed portion of any Security being redeemed in part.

          The provisions of Clauses (1), (2), (3) and (4) below shall apply only
to Global Securities:

               (1)  Each Global Security authenticated under this Indenture
     shall be registered in the name of the Depositary designated 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.

               (2)  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 (A) such Depositary (i) has
     notified the Company that it is unwilling or unable to continue as
     Depositary for such Global Security or (ii) has ceased to be a clearing
     agency registered under the Exchange Act, (B) there shall have occurred and
     be continuing an Event of Default with respect to such Global Security or
     (C) there shall exist such circumstances, if any, in addition to or in lieu
     of the foregoing as have been specified for this purpose as contemplated by
     Section 3.1.

               (3)  Subject to Clause (2) above, any exchange of a Global
     Security for other Securities may be made in whole or in part, and all
     Securities issued in exchange for a Global Security or any

                                       26

<PAGE>

     portion thereof shall be registered in such names as the Depositary for
     such Global Security shall direct.

               (4)  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 Section, Section 3.4, 3.6, 9.6 or
     11.7 or otherwise, shall be authenticated and delivered in the form of, and
     shall be, a 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.

SECTION 3.6   MUTILATED, DESTROYED, LOST AND STOLEN SECURITIES.

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

          If there shall be delivered to the Company and the Trustee (i)
evidence to their satisfaction of the destruction, loss or theft of any Security
and (ii) such security or indemnity as may be required by them to save each of
them and any agent of either of them harmless, then, in the absence of notice to
the Company or the Trustee that such Security has been acquired by a bona fide
purchaser, the Company shall execute and the Trustee shall authenticate and
deliver, in lieu of any such destroyed, lost or stolen Security, a new Security
of the same series and 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 may,
instead of issuing a new Security, pay such Security.

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

          Every new Security of any series issued pursuant to this Section in
lieu of any destroyed, lost or stolen Security shall constitute an original
additional contractual obligation of the Company, whether or not the destroyed,
lost or stolen Security shall be at any time enforceable by anyone, and shall be
entitled to all the

                                       27

<PAGE>

benefits of this Indenture equally and proportionately with any and all other
Securities of that series duly issued hereunder.

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

SECTION 3.7   PAYMENT OF INTEREST; INTEREST RIGHTS PRESERVED.

          Except as otherwise provided as contemplated by Section 3.1 with
respect to any series of Securities, 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 of any series 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 of such series (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 of such series and the date of the proposed
     payment, and at the same time the Company shall deposit with the Trustee an
     amount of money equal to the aggregate amount proposed to be paid in
     respect of such Defaulted Interest or shall make arrangements satisfactory
     to the Trustee for such deposit prior to the date of the proposed payment,
     such money when deposited to be held in trust for the benefit of the
     Persons entitled to such Defaulted Interest as in this Clause provided.
     Thereupon the Trustee shall fix a Special Record Date for the payment of
     such Defaulted Interest which shall be not more than 15 days and not less
     than 10 days prior to the date of the proposed payment and not less than 10
     days after the receipt by the Trustee of the notice of the proposed
     payment. The Trustee shall promptly notify the Company of such Special
     Record Date and, in the name and at the expense of the Company, shall cause

                                       28

<PAGE>

     notice of the proposed payment of such Defaulted Interest and the Special
     Record Date therefor to be given to each Holder of Securities of such
     series in the manner set forth in Section 1.6, 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 of such series (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).

               (2)  The Company may make payment of any Defaulted Interest on
     the Securities of any series in any other lawful manner not inconsistent
     with the requirements of any securities exchange on which such 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, 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.

          Subject to the provisions of Section 14.2, in the case of any Security
(or any part thereof) which is converted after any Regular Record Date and on or
prior to the next succeeding Interest Payment Date (other than any Security the
principal of (or premium, if any, on) which shall become due and payable,
whether at Stated Maturity or by declaration of acceleration prior to such
Interest Payment Date), interest whose Stated Maturity is on such Interest
Payment Date shall be payable on such Interest Payment Date notwithstanding such
conversion and such interest (whether or not punctually paid or duly provided
for) shall be paid to the Person in whose name that Security (or any one or more
Predecessor Securities) is registered at the close of business on such Regular
Record Date. Except as otherwise expressly provided in the immediately preceding
sentence or in Section 14.2, in the case of any Security (or any part thereof)
which is converted, interest whose Stated Maturity is after the date of
conversion of such Security (or such part thereof) shall not be payable.

                                       29

<PAGE>

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 and any premium
and (subject to Section 3.7) any 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, registration of
transfer or exchange or for credit against any sinking fund payment shall, if
surrendered to any Person other than the Trustee, be delivered to the Trustee
and shall be promptly canceled by it. The Company may at any time deliver to the
Trustee for cancellation any Securities previously authenticated and delivered
hereunder which the Company may have acquired in any manner whatsoever, and may
deliver to the Trustee (or to any other Person for delivery to the Trustee) for
cancellation any Securities previously authenticated hereunder which the Company
has not issued and sold, and all Securities so delivered shall be promptly
canceled by the Trustee. No Securities shall be authenticated in lieu of or in
exchange for any Securities canceled as provided in this Section, except as
expressly permitted by this Indenture. All canceled Securities held by the
Trustee shall be disposed of as directed by a Company Order.

SECTION 3.10   COMPUTATION OF INTEREST.

          Except as otherwise specified as contemplated by Section 3.1 for
Securities of any series, interest on the Securities of each series shall be
computed on the basis of a 360-day year of twelve 30-day months.

                                   ARTICLE IV

                           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 registration of transfer or
exchange of Securities herein expressly provided for), and the Trustee, at the
expense of the

                                       30

<PAGE>

Company, shall execute proper instruments 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 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 Trustee or the Company
          and thereafter repaid to the Company or discharged from such trust, as
          provided in Section 10.3) have been delivered to the Trustee for
          cancellation; or

                    (B) all such Securities not theretofore delivered to the
          Trustee for cancellation

                        (i)   have become due and payable, or

                        (ii)  will 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 (i), (ii) or (iii)
          above, has deposited or caused to be deposited with the Trustee as
          trust funds in trust for the purpose of making the following payments,
          money in an amount sufficient to pay and discharge the entire
          indebtedness on such Securities not theretofore delivered to the
          Trustee for cancellation, for principal and any premium and interest
          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.

                                       31

<PAGE>

          Notwithstanding the satisfaction and discharge of this Indenture, the
obligations of the Company to the Trustee under Section 6.7, the obligations of
the Trustee to any Authenticating Agent under Section 6.14 and, if money shall
have been deposited with the Trustee pursuant to subclause (B) of Clause (1) of
this Section, the obligations of the Trustee under Section 4.2 and the last
paragraph of Section 10.3 shall survive.

SECTION 4.2   APPLICATION OF TRUST MONEY.

          Subject to the provisions of the last paragraph of Section 10.3, 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) as the Trustee may
determine, to the Persons entitled thereto, of the principal and any premium and
interest for whose payment such money has been deposited with the Trustee.

                                    ARTICLE V

                                    REMEDIES

SECTION 5.1   EVENTS OF DEFAULT.

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

               (1)  default in the payment of any interest upon any Security of
     that series when it becomes due and payable, and continuance of such
     default for a period of 30 days; or

               (2)  default in the payment of the principal of or any premium on
     any Security of that series at its Maturity; or

               (3)  default in the deposit of any sinking fund payment, when and
     as due by the terms of a Security of that series; or

                                       32

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

               (5)  the 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, equestrator 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 relief
     or any such other decree or order unstayed and in effect for a period of 90
     consecutive days; or

               (6)  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 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

                                       33

<PAGE>

     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; or

               (7)  any other Event of Default provided with respect to
     Securities of that series.

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(5) or 5.1(6)) with respect to Securities of any series at the time
Outstanding 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
of that series may declare the principal amount of all the Securities of that
series (or, if any Securities of that series are Original Issue Discount
Securities, such portion of the principal amount of such Securities as may be
specified by the terms thereof) to be due and payable immediately, by a notice
in writing to the Company (and to the Trustee if given by Holders), and upon any
such declaration such principal amount (or specified amount) shall become
immediately due and payable. If an Event of Default specified in Section 5.1(5)
or 5.1(6) with respect to Securities of any series at the time Outstanding
occurs, the principal amount of all the Securities of that series (or, if any
Securities of that series are Original Issue Discount Securities, such portion
of the principal amount of such Securities as may be specified by the terms
thereof) shall automatically, and without any declaration or other action on the
part of the Trustee or any Holder, become immediately due and payable.

          At any time after such a declaration of acceleration with respect to
Securities of any series 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 provided, the Holders of a majority in principal amount of the
Outstanding Securities of that series, by written 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 on all Securities of that series,

                    (B) the principal of (and premium, if any, on) any
          Securities of that series which have become due otherwise

                                       34

<PAGE>

          than by such declaration of acceleration and any interest thereon at
          the rate or rates prescribed therefor in such Securities,

                    (C) to the extent that payment of such interest is lawful,
          interest upon overdue interest at the rate or rates prescribed
          therefor in such Securities, and

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

               (2)  all Events of Default with respect to Securities of that
     series, other than the non-payment of the principal of Securities of that
     series which have become due solely by such declaration of acceleration,
     have been cured or waived as provided in Section 5.13. No such rescission
     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 on any
     Security when such interest 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, 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 any premium and interest and, to the extent
     that payment of such interest shall be legally enforceable, interest on any
     overdue principal and premium and on any overdue interest, at the rate or
     rates prescribed therefor in such Securities, and, in addition thereto,
     such further amount as shall be sufficient to cover the costs and expenses
     of collection, including the reasonable compensation, expenses,
     disbursements and advances of the Trustee, its agents and counsel.

          If an Event of Default with respect to Securities of any series occurs
and is continuing, the Trustee may in its discretion proceed to protect and
enforce its rights

                                       35

<PAGE>

and the rights of the Holders of Securities of such series 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 any judicial proceeding relative to the Company (or any
other obligor upon the Securities), its property or its creditors, the Trustee
shall be entitled and empowered, by intervention in such proceeding or
otherwise, to take any and all actions authorized under the Trust Indenture Act
in order to have claims of the Holders and the Trustee allowed in any such
proceeding. In particular, the Trustee shall be authorized to collect and
receive any moneys or other property payable or deliverable on any such claims
and to distribute the same; and any custodian, receiver, assignee, trustee,
liquidator, sequestrator or other similar official in any such judicial
proceeding is hereby authorized by each Holder to make such payments to the
Trustee and, in the event that the Trustee shall consent to the making of such
payments directly to the Holders, to pay to the Trustee any amount due it for
the reasonable compensation, expenses, disbursements and advances of the
Trustee, its agents and counsel, and any other amounts due the Trustee under
Section 6.7.

          No provision of this Indenture shall be deemed to authorize the
Trustee to authorize or consent to or accept or adopt on behalf of any Holder
any plan of reorganization, arrangement, adjustment or composition affecting the
Securities or the rights of any Holder thereof or to authorize the Trustee to
vote in respect of the claim of any Holder in any such proceeding; provided,
however, that the Trustee may, on behalf of the Holders, vote for the election
of a trustee in bankruptcy or similar official and be a member of a creditors'
or other similar committee.

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 counsel, be for the
ratable benefit of the Holders of the Securities in respect of which such
judgment has been recovered.

                                       36

<PAGE>

SECTION 5.6   APPLICATION OF MONEY COLLECTED.

          Any money collected by the Trustee pursuant to this Article shall be
applied in the following order, at the date or dates fixed by the Trustee and,
in case of the distribution of such money on account of principal or any premium
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 and any premium, if any, and interest 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 and any premium, if any, and interest,
respectively; and

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

SECTION 5.7   LIMITATION ON SUITS.

          No Holder of any Security of any series 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 with respect to the Securities of
     that series;

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

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

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

                                       37

<PAGE>

               (5)  no direction inconsistent with such written request has been
     given to the Trustee during such 60-day period by the Holders of a majority
     in principal amount of the Outstanding Securities of that series; it being
     understood and intended that no one or more of such Holders shall have any
     right in any manner whatever by virtue of, or by availing of, any provision
     of this Indenture to affect, disturb or prejudice the rights of any other
     of such Holders, or to obtain or to 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 of 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 and any premium and (subject to Section 3.7)
interest on such Security on the respective Stated Maturities expressed in such
Security (or, in the case of redemption, on the Redemption Date), to convert
such Securities in accordance with Article 14 to the extent that such right to
convert is applicable to such Security and to institute suit for the enforcement
of any such payment, 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 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 shall
be restored severally and respectively to their former positions hereunder and
thereafter all rights and remedies of the Trustee and the 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 remedy herein conferred upon or reserved to the
Trustee or to the Holders 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.

                                       38

<PAGE>

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 Securities
to exercise any right or remedy accruing upon any Event of Default shall impair
any such right or remedy or constitute a waiver of any such Event of Default or
an acquiescence therein. Every right and remedy given by this Article or by law
to the Trustee or to the Holders may be exercised from time to time, and as
often as may be deemed expedient, by the Trustee (subject to the limitations
contained in this Indenture) or by the Holders, as the case may be.

SECTION 5.12  CONTROL BY HOLDERS.

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

               (1)  such direction shall not be in conflict with any rule of law
     or with this Indenture and the Trustee shall not have determined that the
     action so directed would be unjustly prejudicial to Holders of Securities
     of that series, or any other series, not taking part in such direction; and

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

SECTION 5.13  WAIVER OF PAST DEFAULTS.

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

               (1)  a default in the payment of the principal of or any premium
     or interest on any Security of such series; or

                                       39

<PAGE>

               (2)  to the extent such right is applicable to such Security, a
     failure by the Company on request to convert any Security into Common
     Stock; or

               (3)  in respect of a covenant or provision hereof which under
     Article 9 cannot be modified or amended without the consent of the Holder
     of each Outstanding Security of such series affected.

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

SECTION 5.14  UNDERTAKING FOR COSTS.

          In any suit for the enforcement of any right or remedy under this
Indenture, or in any suit against the Trustee for any action taken, suffered or
omitted by it as Trustee, a court may require any party litigant in such suit to
file an undertaking to pay the costs of such suit, and may assess costs against
any such party litigant, in the manner and to the extent provided in the Trust
Indenture Act; provided that neither this Section nor the Trust Indenture Act
shall be deemed to authorize any court to require such an undertaking or to make
such an assessment in any suit instituted by the Company or in any suit for the
enforcement of the right to convert any Security in accordance with Article 14.

SECTION 5.15  WAIVER OF USURY, STAY 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 usury, stay or extension law wherever
enacted, now or at any time hereafter in force, which may affect the covenants
or the performance of this Indenture; and the Company (to the extent that it may
lawfully do so) hereby expressly waives all benefit or advantage of any such law
and covenants that it will not hinder, delay or impede the execution of any
power herein granted to the Trustee, but will suffer and permit the execution of
every such power as though no such law had been enacted.

                                       40

<PAGE>

                                   ARTICLE VI

                                   THE TRUSTEE

SECTION 6.1   CERTAIN DUTIES AND RESPONSIBILITIES.

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

SECTION 6.2   NOTICE OF DEFAULTS.

          If a default occurs hereunder with respect to Securities of any
series, the Trustee shall give the Holders of Securities of such series notice
of such default as and to the extent provided by the Trust Indenture Act;
provided, however, that in the case of any default of the character specified in
Section 5.1(4) with respect to Securities of such series, no such notice to
Holders shall be given until at least 30 days after the occurrence thereof. For
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 with
respect to Securities of such series.

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, certificate, statement,
     instrument, opinion, report, notice, request, direction, consent, order,
     bond, debenture, note, 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) is entitled to and

                                       41

<PAGE>

     may, in the absence of bad faith on its part, rely upon an Officers'
     Certificate;

               (4)  the Trustee may consult with counsel and the written 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 pursuant to this Indenture, unless such
     Holders shall have offered to the Trustee reasonable security or indemnity
     against the costs, expenses and liabilities which might be incurred by it
     in compliance with such request or direction;

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

                                       42

<PAGE>

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 neither the Trustee nor any Authenticating Agent assumes any
responsibility for their correctness. The Trustee makes no representations as to
the validity, sufficiency or priority of this Indenture or of the Securities.
Neither the Trustee nor any Authenticating Agent shall be accountable for the
use or application by the Company of Securities or the proceeds thereof.

SECTION 6.5   MAY HOLD SECURITIES AND ACT AS TRUSTEE UNDER OTHER INDENTURES.

          The Trustee, any Authenticating Agent, any Paying Agent, any Security
Registrar or any other agent of the Company, in its individual or any other
capacity, may become the owner or pledgee of Securities and, subject to Sections
6.8 and 6.13, may otherwise deal with the Company with the same rights it would
have if it were not Trustee, Authenticating Agent, Paying Agent, Security
Registrar or such other agent.

          Subject to the limitations imposed by the Trust Indenture Act, nothing
in this Indenture shall prohibit the Trustee from becoming and acting as trustee
under other indentures under which other securities, or certificates of interest
of participation in other securities, of the Company are outstanding in the same
manner as if it were not Trustee hereunder.

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 with the Company.

SECTION 6.7   COMPENSATION AND REIMBURSEMENT.

          The Company agrees:

               (1)  to pay to the Trustee from time to time reasonable
     compensation 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);

                                       43

<PAGE>

               (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 for, and to hold it harmless
     against, any loss, liability or expense incurred without negligence or bad
     faith on its part, arising out of or in connection with the acceptance or
     administration of the trust or trusts hereunder, including the costs and
     expenses of defending itself against any claim or liability in connection
     with the exercise or performance of any of its powers or duties hereunder.

SECTION 6.8   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. To the extent
permitted by such Act, the Trustee shall not be deemed to have a conflicting
interest by virtue of being a trustee under this Indenture with respect to
Securities of more than one series.

SECTION 6.9   CORPORATE TRUSTEE REQUIRED; ELIGIBILITY.

          There shall at all times be one (and only one) Trustee hereunder with
respect to the Securities of each series, which may be Trustee hereunder for
Securities of one or more other series. Each Trustee shall be a Person that is
eligible pursuant to the Trust Indenture Act to act as such and has (or if the
Trustee is a member of a bank holding company system, its bank holding company
has) a combined capital and surplus of at least $50,000,000. If any such Person
or bank holding company publishes reports of condition at least annually,
pursuant to law or to the requirements of its supervising or examining
authority, then for the purposes of this Section and to the extent permitted by
the Trust Indenture Act, the combined capital and surplus of such Person or bank
holding company 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 with respect to the Securities of any series 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.

                                       44

<PAGE>

SECTION 6.10  RESIGNATION AND REMOVAL; APPOINTMENT OF SUCCESSOR.

          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 6.11.

          The Trustee may resign at any time with respect to the Securities of
one or more series by giving written notice thereof to the Company. If the
instrument of acceptance by a successor Trustee required by Section 6.11 shall
not have been delivered to the Trustee within 30 days after the giving of such
notice of resignation, the resigning Trustee may petition any court of competent
jurisdiction for the appointment of a successor Trustee with respect to the
Securities of such series.

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

          If at any time:

               (1)  the Trustee shall fail to comply with Section 6.8 after
     written request therefor by the Company or by any Holder who has been a
     bona fide Holder of a Security for at least six months, or

               (2)  the Trustee shall cease to be eligible under Section 6.9 and
     shall fail to resign after written request therefor by the Company or by
     any such Holder, or

               (3)  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, (A)
     the Company by a Board Resolution may remove the Trustee with respect to
     all Securities, or (B) subject to Section 5.14, any Holder 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 with respect to all Securities
     and the appointment of a successor Trustee or Trustees.

                                       45

<PAGE>

          If the Trustee shall resign, be removed or become incapable of acting,
or if a vacancy shall occur in the office of Trustee for any cause, with respect
to the Securities of one or more series, the Company, by a Board Resolution,
shall promptly appoint a successor Trustee or Trustees with respect to the
Securities of that or those series (it being understood that any such successor
Trustee may be appointed with respect to the Securities of one or more or all of
such series and that at any time there shall be only one Trustee with respect to
the Securities of any particular series) and shall comply with the applicable
requirements of Section 6.11. If, within one year after such resignation,
removal or incapability, or the occurrence of such vacancy, a successor Trustee
with respect to the Securities of any series shall be appointed by Act of the
Holders of a majority in principal amount of the Outstanding Securities of such
series delivered to the Company and the retiring Trustee, the successor Trustee
so appointed shall, forthwith upon its acceptance of such appointment in
accordance with the applicable requirements of Section 6.11, become the
successor Trustee with respect to the Securities of such series and to that
extent supersede the successor Trustee appointed by the Company. If no successor
Trustee with respect to the Securities of any series shall have been so
appointed by the Company or the Holders and accepted appointment in the manner
required by Section 6.11, the retiring Trustee may petition, or any Holder who
has been a bona fide Holder of a Security of such series for at least six months
may, on behalf of himself and all others similarly situated, petition any court
of competent jurisdiction for the appointment of a successor Trustee with
respect to the Securities of such series.

          The Company shall give notice of each resignation and each removal of
the Trustee with respect to the Securities of any series and each appointment of
a successor Trustee with respect to the Securities of any series to all Holders
of Securities of such series in the manner provided in Section 1.6. Each notice
shall include the name of the successor Trustee with respect to the Securities
of such series and the address of its Corporate Trust Office.

SECTION 6.11  ACCEPTANCE OF APPOINTMENT BY SUCCESSOR.

          In case of the appointment hereunder of a successor Trustee with
respect to all Securities, every such successor Trustee so appointed 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

                                       46

<PAGE>

Trustee and shall duly assign, transfer and deliver to such successor Trustee
all property and money held by such retiring Trustee hereunder.

          In case of the appointment hereunder of a successor Trustee with
respect to the Securities of one or more (but not all) series, the Company, the
retiring Trustee and each successor Trustee with respect to the Securities of
one or more series shall execute and deliver an indenture supplemental hereto
wherein each successor Trustee shall accept such appointment and which (1) shall
contain such provisions as shall be necessary or desirable to transfer and
confirm to, and to vest in, each successor Trustee all the rights, powers,
trusts and duties of the retiring Trustee with respect to the Securities of that
or those series to which the appointment of such successor Trustee relates, (2)
if the retiring Trustee is not retiring with respect to all Securities, shall
contain such provisions as shall be deemed necessary or desirable to confirm
that all the rights, powers, trusts and duties of the retiring Trustee with
respect to the Securities of that or those series as to which the retiring
Trustee is not retiring shall continue to be vested in the retiring Trustee, and
(3) shall add to or change any of the provisions of this Indenture as shall be
necessary to provide for or facilitate the administration of the trusts
hereunder by more than one Trustee, it being understood that nothing herein or
in such supplemental indenture shall constitute such Trustees co-trustees of the
same trust and that each such Trustee shall be trustee of a trust or trusts
hereunder separate and apart from any trust or trusts hereunder administered by
any other such Trustee; and upon the execution and delivery of such supplemental
indenture the resignation or removal of the retiring Trustee shall become
effective to the extent provided therein and each such successor Trustee,
without any further act, deed or conveyance, shall become vested with all the
rights, powers, trusts and duties of the retiring Trustee with respect to the
Securities of that or those series to which the appointment of such successor
Trustee relates; but, on request of the Company or any successor Trustee, such
retiring Trustee shall duly assign, transfer and deliver to such successor
Trustee all property and money held by such retiring Trustee hereunder with
respect to the Securities of that or those series to which the appointment of
such successor Trustee relates.

          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 referred to in the
first or second preceding paragraph, as the case may be.

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

                                       47

<PAGE>

SECTION 6.12  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 the corporate trust business
of the Trustee, shall be the successor of the Trustee hereunder, provided such
corporation shall be otherwise qualified and eligible under this Article,
without the execution or filing of any paper or any further act on the part of
any of the parties hereto. In case any Securities shall have been authenticated,
but not delivered, by the Trustee then in office, any successor by merger,
conversion or consolidation to such authenticating Trustee may adopt such
authentication and deliver the Securities so authenticated with the same effect
as if such successor Trustee had itself authenticated such Securities.

SECTION 6.13  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).

SECTION 6.14  APPOINTMENT OF AUTHENTICATING AGENT.

          The Trustee may appoint an Authenticating Agent or Agents with respect
to one or more series of Securities which shall be authorized to act on behalf
of the Trustee to authenticate Securities of such series issued upon original
issue and upon exchange, registration of transfer or partial redemption thereof
or pursuant to Section 3.6, and Securities so authenticated shall be entitled to
the benefits of this Indenture and shall be valid and obligatory for all
purposes as if authenticated by the Trustee hereunder. Wherever reference is
made in this Indenture to the authentication and delivery of Securities by the
Trustee or the Trustee's certificate of authentication, such reference shall be
deemed to include authentication and delivery on behalf of the Trustee by an
Authenticating Agent and a certificate of authentication executed on behalf of
the Trustee by an Authenticating Agent. Each Authenticating Agent shall be
acceptable to the Company and 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, having (or if the Authenticating Agent is a member of a bank holding
company system, its bank holding company has) a combined capital and surplus of
not less than $50,000,000 and subject to supervision or examination by Federal
or State authority. If such Authenticating

                                       48

<PAGE>

Agent 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
Authenticating Agent 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 an
Authenticating Agent shall cease to be eligible in accordance with the
provisions of this Section, such Authenticating Agent shall resign immediately
in the manner and with the effect specified in this Section.

          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, without the execution or filing of any paper or any further
act on the part of the Trustee or the Authenticating Agent.

          An Authenticating Agent may resign at any time by giving written
notice thereof to the Trustee 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, the Trustee may appoint a successor Authenticating
Agent which shall be acceptable to the Company and shall give notice of such
appointment in the manner provided in Section 1.6 to all Holders of Securities
of the series with respect to which such Authenticating Agent will serve. Any
successor Authenticating Agent upon acceptance of its appointment hereunder
shall become vested with all the rights, powers and duties of its predecessor
hereunder, with like effect as if originally named as an Authenticating Agent.
No successor Authenticating Agent shall be appointed unless eligible under the
provisions of this Section.

          The Trustee agrees to pay to each Authenticating Agent from time to
time reasonable compensation for its services under this Section, and the
Trustee shall be entitled to be reimbursed for such payments, subject to the
provisions of Section 6.7.

          If an appointment with respect to one or more series is made pursuant
to this Section 6.12, the Securities of such series may have endorsed thereon,
in addition to the Trustee's certificate of authentication, an alternative
certificate of authentication in the following form:

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

                                       49

<PAGE>


                                             [_________________________],
                                               as Trustee

                                             By:
                                                ----------------------------
                                                    As Authenticating Agent

                                             By:
                                                ----------------------------
                                                    Authorized Officer

                                   ARTICLE VII

                HOLDERS' LISTS AND REPORTS BY TRUSTEE AND COMPANY

SECTION 7.1   COMPANY TO FURNISH TRUSTEE NAMES AND ADDRESSES OF HOLDERS.

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

               (1)  semi-annually, not later 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 of each series as of
     such Regular Record Date, as the case may be; and

               (2)  at such other times as the Trustee may 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; provided that no such list need be furnished
     by the Company to the Trustee so long as the Trustee is acting as Security
     Registrar.

SECTION 7.2   PRESERVATION OF INFORMATION; COMMUNICATIONS TO HOLDERS.

          The Trustee shall preserve, in as current a form as is reasonably
practicable, the names and addresses of Holders contained in the most recent
list furnished to the Trustee as provided in Section 7.1 and the names and
addresses of Holders received by the Trustee in its capacity as Security
Registrar. The Trustee may destroy any list furnished to it as provided in
Section 7.1 upon receipt of a new list so furnished.

                                       50

<PAGE>

          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 privileges of the Trustee, shall be as provided by the
Trust Indenture Act.

          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 7.3   REPORTS BY TRUSTEE.

          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.

          Reports so required to be transmitted at stated intervals of not more
than 12 months shall be transmitted no later than July 1 in each calendar year,
commencing with the first July 1 after the first issuance of Securities pursuant
to this Indenture.

          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 any
Securities are listed, with the Commission and with the Company. The Company
will notify the Trustee when any Securities are listed on any stock exchange.

SECTION 7.4   REPORTS BY COMPANY.

          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 the Trust Indenture 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.

                                       51

<PAGE>

                                  ARTICLE VIII

              CONSOLIDATION, MERGER, CONVEYANCE, TRANSFER OR LEASE

SECTION 8.1   COMPANY MAY CONSOLIDATE, ETC., ONLY ON CERTAIN TERMS.

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

               (1)  in case the Company shall consolidate with or merge into
     another Person (in a transaction in which the Company is not the surviving
     corporation) or convey, transfer or lease its properties and assets
     substantially as an entirety to any Person, the Person formed by such
     consolidation or into which the Company is merged or the Person which
     acquires by conveyance or transfer, or which leases, the properties and
     assets of the Company substantially as an entirety shall be a corporation,
     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 and any premium and interest on all the Securities and the
     performance or observance of every covenant of this Indenture on the part
     of the Company to be performed or observed and the conversion rights shall
     be provided for in accordance with Article 14, if applicable, or as
     otherwise specified pursuant to Section 3.1, by supplemental indenture
     satisfactory in form to the Trustee, executed and delivered to the Trustee,
     by the Person (if other than the Company) formed by such consolidation or
     into which the Company shall have been merged or by the Person which shall
     have acquired the Company's assets;

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

               (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.

                                       52

<PAGE>

SECTION 8.2   SUCCESSOR SUBSTITUTED.

          Upon any consolidation of the Company with, or merger of the Company
into, any other Person or any conveyance, transfer or lease of the properties
and assets of the Company substantially as an entirety in accordance with
Section 8.1, the successor Person formed by such consolidation or into which the
Company is merged or to which such conveyance, transfer or lease is made shall
succeed to, and be substituted for, and may exercise every right and power of,
the Company under this Indenture with the same effect as if such successor
Person had been named as the Company herein, and thereafter, except in the case
of a lease, the predecessor Person shall be relieved of all obligations and
covenants under this Indenture and the Securities.

                                   ARTICLE IX

                             SUPPLEMENTAL INDENTURES

SECTION 9.1   SUPPLEMENTAL INDENTURES WITHOUT CONSENT OF HOLDERS.

          Without the consent of any Holders, 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, in form satisfactory to the
Trustee, for any of the following purposes:

               (1)  to evidence the succession of another Person to the Company,
     or successive successions, and the assumption by any such successor of the
     covenants of the Company herein and in the Securities; or

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

               (3)  to add any additional Events of Default for the benefit of
     the Holders of all or any series of Securities (and if such additional
     Events of Default are to be for the benefit of less than all series

                                       53

<PAGE>

     of Securities, stating that such additional Events of Default are expressly
     being included solely for the benefit of such series); or

               (4)  to add to or change any of the provisions of this Indenture
     to such extent as shall be necessary to permit or facilitate the issuance
     of Securities in bearer form, registrable or not registrable as to
     principal, and with or without interest coupons, or to permit or facilitate
     the issuance of Securities in uncertificated form; or

               (5)  to add to, change or eliminate any of the provisions of this
     Indenture in respect of one or more series of Securities, provided that any
     such addition, change or elimination (A) shall neither (i) apply to any
     Security of any series created prior to the execution of such supplemental
     indenture and entitled to the benefit of such provision nor (ii) modify the
     rights of the Holder of any such Security with respect to such provision or
     (B) shall become effective only when there is no such Security Outstanding;
     or

               (6)  to secure the Securities; or

               (7)  to establish the form or terms of Securities of any series
     as permitted by Sections 2.1 and 3.1; or

               (8)  to evidence and provide for the acceptance of appointment
     hereunder by a successor Trustee with respect to the Securities of one or
     more series and to add to or change any of the provisions of this Indenture
     as shall be necessary to provide for or facilitate the administration of
     the trusts hereunder by more than one Trustee, pursuant to the requirements
     of Section 6.11; or

               (9)  to make provision with respect to the conversion rights of
     Holders pursuant to the requirements of Article 14, including providing for
     the conversion of the securities into any security (other than the Common
     Stock of the Company) or property of the Company; or

               (10) to cure any ambiguity, to correct or supplement any
     provision herein which may be defective or inconsistent with any other
     provision herein, or to make any other provisions with respect to matters
     or questions arising under this Indenture, provided that such action
     pursuant to this Clause (10) shall not adversely affect the interests of
     the Holders of Securities of any series in any material respect; or

                                       54

<PAGE>

               (11) to supplement any of the provisions of the Indenture to such
     extent as shall be necessary to permit or facilitate the defeasance and
     discharge of any series of Securities pursuant to Articles Four and
     Thirteen, provided that any such action shall not adversely affect the
     interests of the Holders of Securities of such series or any other series
     of Securities in any material respect.

SECTION 9.2   SUPPLEMENTAL INDENTURES WITH CONSENT OF HOLDERS.

          With the consent of the Holders of a majority in principal amount of
the Outstanding Securities of each series affected by such supplemental
indenture, by Act of said Holders delivered to the Company and the Trustee, 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 of such series under this Indenture; provided, however, that no such
supplemental indenture shall, without the consent of the Holder of each
Outstanding Security affected thereby,

               (1)  change the Stated Maturity of the principal of, or any
     installment of principal of or interest on, any Security, or reduce the
     principal amount thereof or the rate of interest thereon or any premium
     payable upon the redemption thereof, or reduce the amount of the principal
     of an Original Issue Discount Security or any other Security which would be
     due and payable upon a declaration of acceleration of the Maturity thereof
     pursuant to Section 5.2, or change any Place of Payment where, or the coin
     or currency in which, any Security or any premium or interest thereon is
     payable, or impair the right to institute suit for the enforcement of any
     such payment on or after the Stated Maturity thereof (or, in the case of
     redemption, on or after the Redemption Date), or

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

               (3)  modify any of the provisions of this Section, Section 5.13
     or Section 10.06, except to increase any such percentage or

                                       55

<PAGE>

     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; provided, however, that this clause shall not be
     deemed to require the consent of any Holder with respect to changes in the
     references to "the Trustee" and concomitant changes in this Section and
     Section 10.6, or the deletion of this proviso, in accordance with the
     requirements of Sections 6.11 and 9.1(8), or

               (4)  if applicable, make any change that adversely affects the
     right to convert any security as provided in Article 14 or pursuant to
     Section 3.1 (except as permitted by Section 9.1(9)) or decrease the
     conversion rate or increase the conversion price of any such security. A
     supplemental indenture which changes or eliminates any covenant or other
     provision of this Indenture which has expressly been included solely for
     the benefit of one or more particular series of Securities, or which
     modifies the rights of the Holders of Securities of such series with
     respect to such covenant or other provision, shall be deemed not to affect
     the rights under this Indenture of the Holders of Securities of any other
     series.

It shall not be necessary for any Act of Holders 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 9.3   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. 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 9.4   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
shall be bound thereby.

                                       56

<PAGE>

SECTION 9.5   CONFORMITY WITH TRUST INDENTURE ACT.

          Every supplemental indenture executed pursuant to this Article shall
conform to the requirements of the Trust Indenture Act.

SECTION 9.6   REFERENCE IN SECURITIES TO SUPPLEMENTAL INDENTURES.

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

                                    ARTICLE X

                                    COVENANTS

SECTION 10.1  PAYMENT OF PRINCIPAL, PREMIUM AND INTEREST.

          The Company covenants and agrees for the benefit of each series of
Securities that it will duly and punctually pay the principal of and any premium
and interest on the Securities of that series in accordance with the terms of
the Securities and this Indenture.

                                       57

<PAGE>

SECTION 10.2  MAINTENANCE OF OFFICE OR AGENCY.

          The Company will maintain in each Place of Payment for any series of
Securities an office or agency where Securities of that series may be presented
or surrendered for payment, where Securities of that series may be surrendered
for registration of transfer or exchange, where Securities of that series may be
surrendered for conversion and where notices and demands to or upon the Company
in respect of the Securities of that series and this Indenture may be served.
The Company will give prompt written notice to the Trustee of the location, and
any change in the location, of such office or agency. If at any time the Company
shall fail to maintain any such required office or agency or shall fail to
furnish the Trustee with the address thereof, such presentations, surrenders,
notices and demands may be made or served at the Corporate Trust Office of the
Trustee, and the Company hereby appoints the Trustee as its agent to receive all
such presentations, surrenders, notices and demands. Unless otherwise provided
in a supplemental indenture or pursuant to Section 3.1 hereof, the Place of
Payment for any series of Securities shall be the Corporate Trust Office of the
Trustee.

          The Company may also from time to time designate one or more other
offices or agencies where the Securities of one or more series may be presented
or surrendered for any or all such purposes and may from time to time rescind
such designations; provided, however, that no such designation or rescission
shall in any manner relieve the Company of its obligation to maintain an office
or agency in each Place of Payment for Securities of any series for such
purposes. The Company will give prompt written notice to the Trustee of any such
designation or rescission and of any change in the location of any such other
office or agency.

SECTION 10.3  MONEY FOR SECURITIES PAYMENTS TO BE HELD IN TRUST.

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

          Whenever the Company shall have one or more Paying Agents for any
series of Securities, it will, on or prior to each due date of the principal of
or any premium or interest on any Securities of that series, deposit with a
Paying Agent a sum sufficient to pay such amount, such sum to be held as
provided by the Trust Indenture

                                       58

<PAGE>

Act, and (unless such Paying Agent is the Trustee) the Company will promptly
notify the Trustee of its action or failure so to act.

          The Company will cause each Paying Agent for any series of Securities
other than the Trustee to execute and deliver to the Trustee an instrument in
which such Paying Agent shall agree with the Trustee, subject to the provisions
of this Section, that such Paying Agent will (1) comply with the provisions of
the Trust Indenture Act applicable to it as a Paying Agent and (2) during the
continuance of any default by the Company (or any other obligor upon the
Securities of that series) in the making of any payment in respect of the
Securities of that series, upon the written request of the Trustee, forthwith
pay to the Trustee all sums held in trust by such Paying Agent for payment in
respect of the Securities of that series.

          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.

          Any money deposited with the Trustee or any Paying Agent, or then held
by the Company, in trust for the payment of the principal of or any premium or
interest on any Security of any series and remaining unclaimed for a period
ending on the earlier of the date that is ten Business Days prior to the date
such money would escheat to the State or two years after such principal, premium
or interest has become due and payable shall be paid to the Company on Company
Request, or (if then held by the Company) shall be discharged from such trust;
and the Holder of such Security shall thereafter, as an unsecured general
creditor, look only to the Company for payment thereof, and all liability of the
Trustee or such Paying Agent with respect to such trust money, and all liability
of the Company as trustee thereof, shall thereupon cease; provided, however,
that the Trustee or such Paying Agent, before being required to make any such
repayment, may at the expense of the Company cause to be published once, in a
newspaper published in the English language, customarily published on each
Business Day and of general circulation in each Place of Payment, notice that
such money remains unclaimed and that, after a date specified therein, which
shall not be less than 30 days from the date of such publication, any unclaimed
balance of such money then remaining will be repaid to the Company.

                                       59

<PAGE>

SECTION 10.4  STATEMENT BY OFFICERS AS TO DEFAULT.

          The Company will 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, 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. The fiscal year of the Company currently ends on
December 31; and the Company will give the Trustee prompt written notice of any
change of its fiscal year.

SECTION 10.5  EXISTENCE.

          Subject to Article 8, the Company will do or cause to be done all
things necessary to preserve and keep in full force and effect its existence.

SECTION 10.6  WAIVER OF CERTAIN COVENANTS.

          Except as otherwise specified as contemplated by Section 3.1 for
Securities of such series, the Company may, with respect to the Securities of
any series, omit in any particular instance to comply with any term, provision
or condition set forth in any covenant provided pursuant to Section 3.1(19) or
9.1(2) for the benefit of the Holders of such series if before the time for such
compliance the Holders of at least a majority in principal amount of the
Outstanding Securities of such series shall, by Act of such Holders, either
waive such compliance in such instance or generally waive compliance with such
term, provision or condition, but no such waiver shall extend to or affect such
term, provision 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 in respect of any such term, provision or condition shall
remain in full force and effect.

                                   ARTICLE XI

                            REDEMPTION OF SECURITIES

SECTION 11.1   APPLICABILITY OF ARTICLE.

          Securities of any series which are redeemable before their Stated
Maturity shall be redeemable in accordance with their terms and (except as
otherwise

                                       60

<PAGE>

specified as contemplated by Section 3.1 for such Securities) in accordance with
this Article.

SECTION 11.2  ELECTION TO REDEEM; NOTICE TO TRUSTEE.

          The election of the Company to redeem any Securities shall be
evidenced by a Board Resolution or in another manner specified as contemplated
by Section 3.1 for such Securities. In case of any redemption at the election of
the Company of less than all the Securities of any series (including any such
redemption affecting only a single Security), 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 of such Redemption
Date, of the principal amount of Securities of such series to be redeemed and,
if applicable, of the tenor of the Securities to be redeemed. In the case of any
redemption of Securities prior to the expiration of any restriction on such
redemption provided in the terms of such Securities or elsewhere in this
Indenture, the Company shall furnish the Trustee with an Officers' Certificate
evidencing compliance with such restriction.

SECTION 11.3  SELECTION BY TRUSTEE OF SECURITIES TO BE REDEEMED.

          If less than all the Securities of any series are to be redeemed
(unless all the Securities of such series and of a specified tenor are to be
redeemed or unless such redemption affects only a single Security), the
particular Securities to be redeemed shall be selected not more than 45 days
prior to the Redemption Date by the Trustee, from the Outstanding Securities of
such series not previously called for redemption, by lot, or in the Trustee's
discretion, on a pro-rata basis, provided that the unredeemed portion of the
principal amount of any Security shall be in an authorized denomination (which
shall not be less than the minimum authorized denomination) for such Security.
If less than all the Securities of such series and of a specified tenor are to
be redeemed (unless such redemption affects only a single Security), the
particular Securities to be redeemed shall be selected not more than 45 days
prior to the Redemption Date by the Trustee, from the Outstanding Securities of
such series and specified tenor not previously called for redemption in
accordance with the preceding sentence.

          If any Security selected for partial redemption is converted in part
before termination of the conversion right with respect to the portion of the
Security so selected, the converted portion of such Security shall be deemed (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 shall be treated
by the Trustee as Outstanding for the purpose of such selection.

                                       61

<PAGE>

          The Trustee shall promptly notify the Company in writing of the
Securities selected for redemption as aforesaid and, in case of any Securities
selected for partial redemption as aforesaid, the principal amount thereof to be
redeemed.

          The provisions of the two preceding paragraphs shall not apply with
respect to any redemption affecting only a single Security, whether such
Security is to be redeemed in whole or in part. In the case of any such
redemption in part, the unredeemed portion of the principal amount of the
Security shall be in an authorized denomination (which shall not be less than
the minimum authorized denomination) for such Security.

          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 11.4  NOTICE OF REDEMPTION.

          Notice of redemption shall be given by first-class mail, postage
prepaid, mailed not less than 30 nor more than 60 days prior to the Redemption
Date, unless a shorter period is specified in the Securities to be redeemed, to
each Holder of Securities to be redeemed, at its address appearing in the
Security Register.

          All notices of redemption shall state:

               (1)  the Redemption Date,

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

               (3)  if less than all the Outstanding Securities of any series
     consisting of more than a single Security are to be redeemed, the
     identification (and, in the case of partial redemption of any such
     Securities, the principal amounts) of the particular Securities to be
     redeemed and, if less than all the Outstanding Securities of any series
     consisting of a single Security are to be redeemed, the principal amount of
     the particular Security to be redeemed,

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

                                       62

<PAGE>

               (5)  the place or places where each such Security is to be
     surrendered for payment of the Redemption Price,

               (6)  if applicable, the conversion price, the date on which the
     right to convert the principal of the Securities or the portions thereof to
     be redeemed will terminate, and the place or places where such Securities
     may be surrendered for conversion, and

               (7)  that the redemption is for a sinking fund, if such is the
     case.

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

SECTION 11.5  DEPOSIT OF REDEMPTION PRICE.

          On or prior to any Redemption Date, the Company shall deposit with the
Trustee or with a Paying Agent (or, if the Company is acting as its own Paying
Agent, segregate and hold in trust as provided in Section 10.3) an amount of
money 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.

          If any Security called for redemption is converted, any money
deposited with the Trustee or with a Paying Agent or so segregated and held in
trust for the redemption of such Security shall (subject to the right of any
Holder of such 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 11.6  SECURITIES PAYABLE ON REDEMPTION DATE.

          Notice of redemption having been given as aforesaid, the Securities so
to be redeemed shall, on the Redemption Date, become due and payable at the
Redemption Price therein specified, and from and after such date (unless the
Company shall default in the payment of the Redemption Price and accrued
interest) such Securities shall cease to bear interest. Upon surrender of any
such Security for redemption in accordance with said notice, such Security shall
be paid by the Company at the Redemption Price, together with accrued interest
to the Redemption Date; provided, however, that, unless otherwise specified as
contemplated by Section 3.1, installments of interest whose

                                       63

<PAGE>

Stated Maturity is on or prior to the Redemption Date will be payable to the
Holders of such Securities, or one or more Predecessor Securities, registered as
such at the close of business on the relevant Record Dates according to their
terms and the provisions of Section 3.7.

          If any Security called for redemption shall not be so paid upon
surrender thereof for redemption, the principal and any premium shall, until
paid, bear interest from the Redemption Date at the rate prescribed therefor in
the Security.

SECTION 11.7  SECURITIES REDEEMED IN PART.

          Any Security which is to be redeemed only in part shall be surrendered
at a Place of Payment therefor (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 its attorney
duly authorized in writing), and the Company shall execute, and the Trustee
shall authenticate and deliver to the Holder of such Security without service
charge, a new Security or Securities of the same series and of like tenor, 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.

                                   ARTICLE XII

                                  SINKING FUNDS

SECTION 12.1  APPLICABILITY OF ARTICLE.

          The provisions of this Article shall be applicable to any sinking fund
for the retirement of Securities of any series except as otherwise specified as
contemplated by Section 3.1 for such Securities.

          The minimum amount of any sinking fund payment provided for by the
terms of any Securities is herein referred to as a "mandatory sinking fund
payment," and any payment in excess of such minimum amount provided for by the
terms of such Securities is herein referred to as an "optional sinking fund
payment." If provided for by the terms of any Securities, the cash amount of any
sinking fund payment may be subject to reduction as provided in Section 12.2.
Each sinking fund payment shall be applied to the redemption of Securities as
provided for by the terms of such Securities.

                                       64

<PAGE>

SECTION 12.2  SATISFACTION OF SINKING FUND PAYMENTS WITH SECURITIES.

          The Company (1) may deliver Outstanding Securities of a series (other
than any previously called for redemption) and (2) may apply as a credit
Securities of a series which have been redeemed either at the election of the
Company pursuant to the terms of such Securities or through the application of
permitted optional sinking fund payments pursuant to the terms of such
Securities, in each case in satisfaction of all or any part of any sinking fund
payment with respect to any Securities of such series required to be made
pursuant to the terms of such Securities as and to the extent provided for by
the terms of such Securities; provided that the Securities to be so credited
have not been previously so credited. The Securities to be so credited shall be
received and credited for such purpose by the Trustee at the Redemption Price,
as specified in the Securities so to be redeemed, for redemption through
operation of the sinking fund and the amount of such sinking fund payment shall
be reduced accordingly.

SECTION 12.3  REDEMPTION OF SECURITIES FOR SINKING FUND.

          Not less than 60 days prior to each sinking fund payment date for any
Securities, the Company will deliver to the Trustee an Officers' Certificate
specifying the amount of the next ensuing sinking fund payment for such
Securities pursuant to the terms of such Securities, the portion thereof, if
any, which is to be satisfied by payment of cash and the portion thereof, if
any, which is to be satisfied by delivering and crediting Securities pursuant to
Section 12.2 and will also deliver to the Trustee any Securities to be so
delivered. Not less than 30 days prior to each such sinking fund payment date,
the Trustee shall select the Securities to be redeemed upon such sinking fund
payment date in the manner specified in Section 11.3 and cause notice of the
redemption thereof to be given in the name of and at the expense of the Company
in the manner provided in Section 11.4. Such notice having been duly given, the
redemption of such Securities shall be made upon the terms and in the manner
stated in Sections 11.6 and 11.7.

                                       65

<PAGE>

                                  ARTICLE XIII

                       DEFEASANCE AND COVENANT DEFEASANCE

SECTION 13.1  COMPANY'S OPTION TO EFFECT DEFEASANCE OR COVENANT DEFEASANCE.

          The Company may elect, at its option at any time, to have Section 13.2
or Section 13.3 applied to any Securities or any series of Securities, as the
case may be, designated pursuant to Section 3.1 as being defeasible pursuant to
such Section 13.2 or 13.3, in accordance with any applicable requirements
provided pursuant to Section 3.1 and upon compliance with the conditions set
forth below in this Article. Any such election shall be evidenced by a Board
Resolution or in another manner specified as contemplated by Section 3.1 for
such Securities.

SECTION 13.2  DEFEASANCE AND DISCHARGE.

          Upon the Company's exercise of its option (if any) to have this
Section applied to any Securities or any series of Securities, as the case may
be, the Company shall be deemed to have been discharged from its obligations
with respect to such Securities as provided in this Section on and after the
date the conditions set forth in Section 13.4 are satisfied (hereinafter called
"Defeasance"). For this purpose, such Defeasance means that the Company shall be
deemed to have paid and discharged the entire indebtedness represented by such
Securities and to have satisfied all its other obligations under such Securities
and this Indenture insofar as such Securities are concerned (and the Trustee, at
the expense of the Company, shall execute proper instruments acknowledging the
same), subject to the following which shall survive until otherwise terminated
or discharged hereunder:

               (1)  the rights of Holders of such Securities to receive, solely
     from the trust fund described in Section 13.4 and as more fully set forth
     in such Section, payments in respect of the principal of and any premium
     and interest on such Securities when payments are due;

               (2)  the Company's obligations with respect to such Securities
     under Sections 3.4, 3.5, 3.6, 10.2 and 10.3, and, if applicable, Article
     14;

               (3)  the rights, powers, trusts, duties and immunities of the
     Trustee hereunder; and

               (4)  this Article.

                                       66

<PAGE>

          Subject to compliance with this Article, the Company may exercise its
option (if any) to have this Section applied to any Securities notwithstanding
the prior exercise of its option (if any) to have Section 13.3 applied to such
Securities.

SECTION 13.3  COVENANT DEFEASANCE.

          Upon the Company's exercise of its option (if any) to have this
Section applied to any Securities or any series of Securities, as the case may
be:

               (1)  the Company shall be released from its obligations under any
     covenants provided pursuant to Section 3.1(19) or 9.1(2) or for the benefit
     of the Holders of such Securities; and

               (2)  the occurrence of any event specified in any covenants
     provided pursuant to Section 3.1(19) or 9.1(2) shall be deemed not to be or
     result in an Event of Default,

in each case with respect to such Securities as provided in this Section on and
after the date the conditions set forth in Section 13.4 are satisfied
(hereinafter called "Covenant Defeasance"). For this purpose, such Covenant
Defeasance means that, with respect to such Securities, the Company may omit to
comply with and shall have no liability in respect of any term, condition or
limitation set forth in any such specified Section (to the extent so specified
in the case of Section 5.1(4)), whether directly or indirectly by reason of any
reference elsewhere herein to any such Section or by reason of any reference in
any such Section to any other provision herein or in any other document, but the
remainder of this Indenture and such Securities shall be unaffected thereby.

SECTION 13.4  CONDITIONS TO DEFEASANCE OR COVENANT DEFEASANCE.

          The following shall be the conditions to the application of Section
13.2 or Section 13.3 to any Securities or any series of Securities, as the case
may be:

               (1)  The Company shall irrevocably have deposited or caused to be
     deposited with the Trustee (or another trustee which satisfies the
     requirements contemplated by Section 6.9 and agrees to comply with the
     provisions of this Article applicable to it) as trust funds in trust for
     the purpose of making the following payments, specifically pledged as
     security for, and dedicated solely to, the benefits of the Holders of such
     Securities, (A) money in an amount, or (B) U.S. Government Obligations
     which through the scheduled payment of principal and interest in respect
     thereof in accordance with their terms

                                       67

<PAGE>

     will provide, not later than one day before the due date of any payment,
     money in an amount, or (C) a combination thereof, in each case sufficient,
     in the opinion of a nationally recognized firm of independent public
     accountants expressed in a written certification thereof delivered to the
     Trustee, to pay and discharge, and which shall be applied by the Trustee
     (or any such other qualifying trustee) to pay and discharge, the principal
     of and any premium and interest on such Securities on the respective Stated
     Maturities, in accordance with the terms of this Indenture and such
     Securities. As used herein, "U.S. Government Obligation" means (x) any
     security which is (i) a direct obligation of the United States of America
     for the payment of which the full faith and credit of the United States of
     America is pledged or (ii) an obligation of a Person controlled or
     supervised by and acting as an agency or instrumentality of the United
     States of America the payment of which is unconditionally guaranteed as a
     full faith and credit obligation by the United States of America, which, in
     either case (i) or (ii), is not callable or redeemable at the option of the
     issuer thereof, and (y) any depositary receipt issued by a bank (as defined
     in Section 3(a)(2) of the Securities Act) as custodian with respect to any
     U.S. Government Obligation which is specified in Clause (x) above and held
     by such bank for the account of the holder of such depositary receipt, or
     with respect to any specific payment of principal of or interest on any
     U.S. Government Obligation which is so specified and held, provided that
     (except as required by law) such custodian is not authorized to make any
     deduction from the amount payable to the holder of such depositary receipt
     from any amount received by the custodian in respect of the U.S. Government
     Obligation or the specific payment of principal or interest evidenced by
     such depositary receipt.

               (2)  In the event of an election to have Section 13.2 apply to
     any Securities or any series of Securities, as the case may be, the Company
     shall have delivered to the Trustee an Opinion of Counsel stating that (A)
     the Company has received from, or there has been published by, the Internal
     Revenue Service a ruling or (B) since the date of this instrument, there
     has been a change in the applicable Federal income tax law, in either case
     (A) or (B) to the effect that, and based thereon such opinion shall confirm
     that, the Holders of such Securities will not recognize gain or loss for
     Federal income tax purposes as a result of the deposit, Defeasance and
     discharge to be effected with respect to such Securities and will be
     subject to Federal income tax on the same amount, in the same manner and at
     the same times as would be the case if such deposit, Defeasance and
     discharge were not to occur.

                                       68

<PAGE>

               (3)  In the event of an election to have Section 13.3 apply to
     any Securities or any series of Securities, as the case may be, the Company
     shall have delivered to the Trustee an Opinion of Counsel to the effect
     that the Holders of such Securities will not recognize gain or loss for
     Federal income tax purposes as a result of the deposit and Covenant
     Defeasance to be effected with respect to such Securities and will be
     subject to Federal income tax on the same amount, in the same manner and at
     the same times as would be the case if such deposit and Covenant Defeasance
     were not to occur.

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

               (5)  No event which is, or after notice or lapse of time or both
     would become, an Event of Default with respect to such Securities or any
     other Securities shall have occurred and be continuing at the time of such
     deposit or, with regard to any such event specified in Sections 5.1(5) and
     (6), at any time on or prior to the 90th day after the date of such deposit
     (it being understood that this condition shall not be deemed satisfied
     until after such 90th day).

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

               (7)  Such Defeasance or Covenant Defeasance shall not result in a
     breach or violation of, or constitute a default under, any other agreement
     or instrument to which the Company is a party or by which it is bound.

               (8)  Such Defeasance or Covenant Defeasance shall not result in
     the trust arising from such deposit constituting an investment company
     within the meaning of the Investment Company Act unless such trust shall be
     registered under such Act or exempt from registration thereunder.

               (9)  The Company shall have delivered to the Trustee an Officers'
     Certificate and an Opinion of Counsel, each stating that all

                                       69

<PAGE>

     conditions precedent with respect to such Defeasance or Covenant Defeasance
     have been complied with.

SECTION 13.5  DEPOSITED MONEY AND U.S. GOVERNMENT OBLIGATIONS TO BE HELD IN
              TRUST; MISCELLANEOUS PROVISIONS.

          Subject to the provisions of the last paragraph of Section 10.3, all
money and U.S. Government Obligations (including the proceeds thereof) deposited
with the Trustee or other qualifying trustee (solely for purposes of this
Section and Section 13.6, the Trustee and any such other trustee are referred to
collectively as the "Trustee") pursuant to Section 13.4 in respect of any
Securities shall be held in trust and applied by the Trustee, in accordance with
the provisions of such Securities and this Indenture, to the payment, either
directly or through any such Paying Agent (including the Company acting as its
own Paying Agent) as the Trustee may determine, to the Holders of such
Securities, of all sums due and to become due thereon in respect of principal
and any premium and interest, but money so held in trust need not be segregated
from other funds except to the extent required by law.

          The Company shall pay and indemnify the Trustee against any tax, fee
or other charge imposed on or assessed against the U.S. Government Obligations
deposited pursuant to Section 13.4 or the principal and interest received in
respect thereof other than any such tax, fee or other charge which by law is for
the account of the Holders of Outstanding Securities.

          Anything in this Article to the contrary notwithstanding, the Trustee
shall deliver or pay to the Company from time to time upon Company Request any
money or U.S. Government Obligations held by it as provided in Section 13.4 with
respect to any Securities which, in the opinion of a nationally recognized firm
of independent public accountants expressed in a written certification thereof
delivered to the Trustee, are in excess of the amount thereof which would then
be required to be deposited to effect the Defeasance or Covenant Defeasance, as
the case may be, with respect to such Securities.

SECTION 13.6  REINSTATEMENT.

          If the Trustee or the Paying Agent is unable to apply any money in
accordance with this Article with respect to any Securities by reason of any
order or judgment of any court or governmental authority enjoining, restraining
or otherwise prohibiting such application, then the obligations under this
Indenture and such Securities from which the Company has been discharged or
released pursuant to Section 13.2 or 13.3 shall be revived and reinstated as
though no deposit had occurred pursuant to this Article with respect to such
Securities, until such time as the Trustee or Paying Agent is permitted to apply
all money held in trust pursuant to Section 13.5 with respect

                                       70

<PAGE>

to such Securities in accordance with this Article; provided, however, that if
the Company makes any payment of principal of or any premium or interest on any
such Security following such reinstatement of its obligations, the Company shall
be subrogated to the rights (if any) of the Holders of such Securities to
receive such payment from the money so held in trust.

                                   ARTICLE XIV

                            CONVERSION OF SECURITIES

SECTION 14.1  APPLICABILITY OF ARTICLE.

          The provisions of this Article shall be applicable to the Securities
of any series which are convertible into shares of Common Stock of the Company,
and the issuance of such shares of Common Stock upon the conversion of such
Securities, except as otherwise specified as contemplated by Section 3.1 for the
Securities of such series.

SECTION 14.2  EXERCISE OF CONVERSION PRIVILEGE.

          In order to exercise a conversion privilege, the Holder of a Security
of a series with such a privilege shall surrender such Security to the Company
at the office or agency maintained for that purpose pursuant to Section 10.2,
accompanied by a duly executed conversion notice to the Company substantially in
the form set forth in Section 2.4 stating that the Holder elects to convert such
Security or a specified portion thereof. Such notice shall also state, if
different from the name and address of such Holder, the name or names (with
address) in which the certificate or certificates for shares of Common Stock
which shall be issuable on such conversion shall be issued. Securities
surrendered for conversion shall (if so required by the Company or the Trustee)
be duly endorsed by or accompanied by instruments of transfer in forms
satisfactory to the Company and the Trustee duly executed by the registered
Holder or its attorney duly authorized in writing; and Securities so surrendered
for conversion (in whole or in part) during the period from the close of
business on any Regular Record Date to the opening of business on the next
succeeding Interest Payment Date (excluding Securities or portions thereof
called for redemption during the period beginning at the close of business on a
Regular Record Date and ending at the opening of business on the first Business
Day after the next succeeding Interest Payment Date, or if such Interest Payment
Date is not a Business Day, the second such Business Day) shall also be
accompanied by payment in funds acceptable to the Company of an amount equal to
the interest payable on such Interest Payment Date on the principal amount of
such Security then being converted, and such interest shall be payable to such
registered Holder

                                       71

<PAGE>

notwithstanding the conversion of such Security, subject to the provisions of
Section 3.7 relating to the payment of Defaulted Interest by the Company. As
promptly as practicable after the receipt of such notice and of any payment
required pursuant to a Board Resolution and, subject to Section 3.3, set forth,
or determined in the manner provided, in an Officers' Certificate, or
established in one or more indentures supplemental hereto setting forth the
terms of such series of Security, and the surrender of such Security in
accordance with such reasonable regulations as the Company may prescribe, the
Company shall issue and shall deliver, at the office or agency at which such
Security is surrendered, to such Holder or on its written order, a certificate
or certificates for the number of full shares of Common Stock issuable upon the
conversion of such Security (or specified portion thereof), in accordance with
the provisions of such Board Resolution, Officers' Certificate or supplemental
indenture, and cash as provided therein in respect of any fractional share of
such Common Stock otherwise issuable upon such conversion. Such conversion shall
be deemed to have been effected immediately prior to the close of business on
the date on which such notice and such payment, if required, shall have been
received in proper order for conversion by the Company and such Security shall
have been surrendered as aforesaid (unless such Holder shall have so surrendered
such Security and shall have instructed the Company to effect the conversion on
a particular date following such surrender and such Holder shall be entitled to
convert such Security on such date, in which case such conversion shall be
deemed to be effected immediately prior to the close of business on such date)
and at such time the rights of the Holder of such Security as such Security
Holder shall cease and the person or persons in whose name or names any
certificate or certificates for shares of Common Stock of the Company shall be
issuable upon such conversion shall be deemed to have become the Holder or
Holders of record of the shares represented thereby. Except as set forth above
and subject to the final paragraph of Section 3.7, no payment or adjustment
shall be made upon any conversion on account of any interest accrued on the
Securities (or any part thereof) surrendered for conversion or on account of any
dividends on the Common Stock of the Company issued upon such conversion. 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 deliver to or on
the order of the Holder thereof, at the expense of the Company, a new Security
or Securities of the same series, of authorized denominations, in aggregate
principal amount equal to the unconverted portion of such Security.

SECTION 14.3  NO FRACTIONAL SHARES.

          No fractional share of Common Stock of the Company shall be issued
upon conversions of Securities of any series. 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 shall be computed on the basis of
the aggregate principal amount of the Securities (or specified portions thereof
to the extent permitted

                                       72

<PAGE>

hereby) so surrendered. If, except for the provisions of this Section 14.3, any
Holder of a Security or Securities would be entitled to a fractional share of
Common Stock of the Company upon the conversion of such Security or Securities,
or specified portions thereof, the Company shall pay to such Holder an amount in
cash equal to the current market value of such fractional share computed, (i) if
such Common Stock is listed or admitted to unlisted trading privileges on a
national securities exchange or market, on the basis of the last reported sale
price on such exchange or market on the last trading day prior to the date of
conversion upon which such a sale shall have been effected, or (ii) if such
Common Stock is not at the time so listed or admitted to unlisted trading
privileges on a national securities exchange or market, on the basis of the
average of the bid and asked prices of such Common Stock in the over-the-counter
market, on the last trading day prior to the date of conversion, as reported by
the National Quotation Bureau, Incorporated or similar organization if the
National Quotation Bureau, Incorporated is no longer reporting such information,
or if not so available, the fair market price as determined by the Board of
Directors. For purposes of this Section, "trading day" shall mean each Monday,
Tuesday, Wednesday, Thursday and Friday other than any day on which the Common
Stock is not traded on the New York Stock Exchange, or if the Common Stock is
not traded on the New York Stock Exchange, on the principal exchange or market
on which the Common Stock is traded or quoted.

SECTION 14.4  ADJUSTMENT OF CONVERSION PRICE.

          The conversion price of Securities of any series that is convertible
into Common Stock of the Company shall be adjusted for any stock dividends,
stock splits, reclassifications, combinations or similar transactions in
accordance with the terms of the supplemental indenture or Board Resolutions
setting forth the terms of the Securities of such series. Whenever the
conversion price is adjusted, the Company shall compute the adjusted conversion
price in accordance with terms of the applicable Board Resolution or
supplemental indenture and shall prepare an Officers' Certificate setting forth
the adjusted conversion price and showing in reasonable detail the facts upon
which such adjustment is based, and such certificate shall forthwith be filed at
each office or agency maintained for the purpose of conversion of Securities
pursuant to Section 10.2 and, if different, with the Trustee. The Company shall
forthwith cause a notice setting forth the adjusted conversion price to be
mailed, first class postage prepaid, to each Holder of Securities of such series
at its address appearing on the Security Register and to any conversion agent
other than the Trustee.

                                       73

<PAGE>

SECTION 14.5  NOTICE OF CERTAIN CORPORATE ACTIONS.

          In case:

               (1)  the Company shall declare a dividend (or any other
     distribution) on its Common Stock payable otherwise than in cash out of its
     retained earnings (other than a dividend for which approval of any
     shareholders of the Company is required) that would require an adjustment
     pursuant to Section 14.4; or

               (2)  the Company shall authorize the granting to all or
     substantially all of the holders of its Common Stock of rights, options or
     warrants to subscribe for or purchase any shares of capital stock of any
     class or of any other rights (other than any such grant for which approval
     of any shareholders of the Company is required); or

               (3)  of any reclassification of the Common Stock of the Company
     (other than a subdivision or combination of its outstanding shares of
     Common Stock, or of any consolidation, merger or share exchange to which
     the Company is a party and for which approval of any shareholders of the
     Company is required), or of the sale of all or substantially all of the
     assets of the Company; or

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

then the Company shall cause to be filed with the Trustee, and shall cause to be
mailed to all Holders at their last addresses as they shall appear in the
Security Register, at least 20 days (or 10 days in any case specified in Clause
(1) or (2) above) prior to the applicable record date hereinafter specified, a
notice stating (i) 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 (ii) the date on which such reclassification, consolidation,
merger, share exchange, sale, dissolution, liquidation or winding up is expected
to become effective, and the date as of which it is expected that holders of
Common Stock of record shall be entitled to exchange their shares of Common
Stock for securities, cash or other property deliverable upon such
reclassification, consolidation, merger, share exchange, sale, dissolution,
liquidation or winding up. If at any 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.

                                       74

<PAGE>

SECTION 14.6  RESERVATION OF SHARES OF 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 of the Company then issuable upon the conversion of all outstanding
Securities of any series that has conversion rights.

SECTION 14.7  PAYMENT OF CERTAIN TAXES UPON CONVERSION.

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

SECTION 14.8  NONASSESSABILITY.

          The Company covenants that all shares of its Common Stock which may be
issued upon conversion of Securities will upon issue in accordance with the
terms hereof be duly and validly issued and fully paid and nonassessable.

SECTION 14.9  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 of a series then Outstanding that is convertible into Common Stock
of the Company shall have the right thereafter (which right shall be the
exclusive conversion right thereafter available to said Holder), during the
period such Security shall be convertible, 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

                                       75

<PAGE>

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 (a "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 14.9 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 or in accordance with the terms of
the supplemental indenture or Board Resolutions setting forth the terms of such
adjustments. The above provisions of this Section 14.9 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 of a series that is convertible into
Common Stock of the Company as provided in Section 1.6 promptly upon such
execution. Neither the Trustee nor any conversion agent, if any, 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 of a series convertible into Common Stock of the Company 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 Opinion of Counsel with respect thereto, which the Company
shall cause to be furnished to the Trustee upon request.

SECTION 14.10 DUTIES OF TRUSTEE REGARDING CONVERSION.

          Neither the Trustee nor any conversion agent shall at any time be
under any duty or responsibility to any Holder of Securities of any series that
is convertible into Common Stock of the Company to determine whether any facts
exist which may

                                       76

<PAGE>

require any adjustment of the conversion price, or with respect to the nature or
extent of any such adjustment when made, or with respect to the method employed,
whether herein or in any supplemental indenture, any resolutions of the Board of
Directors or written instrument executed by one or more officers of the Company
provided to be employed in making the same. Neither the Trustee nor any
conversion agent shall be accountable with respect to the validity or value (or
the kind or amount) of any shares of Common Stock of the Company, or of any
securities or property, which may at any time be issued or delivered upon the
conversion of any Securities and neither the Trustee nor any conversion agent
makes any representation with respect thereto. Subject to the provisions of
Section 6.1, neither the Trustee nor any conversion agent shall be responsible
for any failure of the Company to issue, transfer or deliver any shares of its
Common Stock or stock certificates or other securities or property upon the
surrender of any Security for the purpose of conversion or to comply with any of
the covenants of the Company contained in this Article 14 or in the applicable
supplemental indenture, resolutions of the Board of Directors or written
instrument executed by one or more duly authorized officers of the Company.

SECTION 14.11 REPAYMENT OF CERTAIN FUNDS UPON CONVERSION.

          Any funds which at any time shall have been deposited by the Company
or on its behalf with the Trustee or any other paying agent for the purpose of
paying the principal of and any premium and interest on any of the Securities
(including, but not limited to, funds deposited for the sinking fund referred to
in Article 12 hereof and funds deposited pursuant to Article 13 hereof) and
which shall not be required for such purposes because of the conversion of such
Securities as provided in this Article 14 shall after such conversion be repaid
to the Company by the Trustee upon the Company's written request.

                                       77

<PAGE>

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

                                        BLACK HILLS CORPORATION


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


                                        ATTEST:

                                        [_________________________],
                                                as Trustee

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

                                       78