<PAGE>   1
                                                                     EXHIBIT 4.1

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




                           ALLEGIANCE TELECOM, INC.,
                                                    as Issuer


                                      and


                              THE BANK OF NEW YORK




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

                                   Indenture

                       Dated as of [             ], 1998

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


                         [    ]% Senior Notes due 2008




================================================================================
<PAGE>   2
                             CROSS-REFERENCE TABLE

<TABLE>
<CAPTION>
TIA Sections                                                  Indenture Sections
------------                                                  ------------------
<S>                                                           <C>
Section  310(a)(1)  . . . . . . . . . . . . . . . . . . . . . .   7.10
            (a)(2)  . . . . . . . . . . . . . . . . . . . . . .   7.10
            (b)   . . . . . . . . . . . . . . . . . . . . . . .   7.08
Section  313(c) . . . . . . . . . . . . . . . . . . . . . . . .   7.06; 10.02
Section  314(a) . . . . . . . . . . . . . . . . . . . . . . . .   4.17; 10.02
            (a)(4). . . . . . . . . . . . . . . . . . . . . . .   4.16; 10.02
            (c)(1). . . . . . . . . . . . . . . . . . . . . . .   10.03
            (c)(2). . . . . . . . . . . . . . . . . . . . . . .   10.03
            (e) . . . . . . . . . . . . . . . . . . . . . . . .   10.04
Section  315(b) . . . . . . . . . . . . . . . . . . . . . . . .   7.05; 10.02
Section  316(a)(1)(A) . . . . . . . . . . . . . . . . . . . . .   6.05
            (a)(1)(B) . . . . . . . . . . . . . . . . . . . . .   6.04
            (b) . . . . . . . . . . . . . . . . . . . . . . . .   6.07
Section  317(a)(1). . . . . . . . . . . . . . . . . . . . . . .   6.08
            (a)(2). . . . . . . . . . . . . . . . . . . . . . .   6.09
Section  318(a) . . . . . . . . . . . . . . . . . . . . . . . .   10.01
            (c)   . . . . . . . . . . . . . . . . . . . . . . .   10.01
</TABLE>

Note:    The Cross-Reference Table shall not for any purpose be deemed to be a
         part of the Indenture.
<PAGE>   3
                               TABLE OF CONTENTS
<TABLE>
<CAPTION>
                                                                                                                      Page
                                                                                                                      ----
   <S>                                                                                                                 <C>
   RECITALS OF THE COMPANY  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

                                                       ARTICLE ONE
                                        DEFINITIONS AND INCORPORATION BY REFERENCE

   SECTION 1.01.  Definitions   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
   SECTION 1.02.  Incorporation by Reference of Trust Indenture Act   . . . . . . . . . . . . . . . . . . . . . . . .  20
   SECTION 1.03.  Rules of Construction   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  21

                                                       ARTICLE TWO
                                                        THE NOTES

   SECTION 2.01.  Form and Dating   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  21
   SECTION 2.02.  Execution, Authentication and Denominations   . . . . . . . . . . . . . . . . . . . . . . . . . . .  22
   SECTION 2.03.  Registrar and Paying Agent  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  23
   SECTION 2.04.  Paying Agent to Hold Money in Trust   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  23
   SECTION 2.05.  Transfer and Exchange   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  24
   SECTION 2.06.  Book-Entry Provisions for Global Notes  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  25
   SECTION 2.07.  Replacement Notes   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  26
   SECTION 2.08.  Outstanding Notes   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  26
   SECTION 2.09.  Temporary Notes   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  27
   SECTION 2.10.  Cancellation  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  27
   SECTION 2.11.  CUSIP Numbers   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  27
   SECTION 2.12.  Defaulted Interest  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  27
   SECTION 2.13.  Issuance of Additional Notes  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  28

                                                      ARTICLE THREE
                                                        REDEMPTION

   SECTION 3.01.  Right of Redemption   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  28
   SECTION 3.02.  Notices to Trustee  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  29
   SECTION 3.03.  Selection of Notes to Be Redeemed   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  29
   SECTION 3.04.  Notice of Redemption  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  29
   SECTION 3.05.  Effect of Notice of Redemption  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  30
   SECTION 3.06.  Deposit of Redemption Price   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  30
   SECTION 3.07.  Payment of Notes Called for Redemption  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  31
   SECTION 3.08.  Notes Redeemed in Part  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  31
</TABLE>



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

Note:    The Table of Contents shall not for any purposes be deemed to be a
         part of the Indenture.
<PAGE>   4
                                       ii

<TABLE>
   <S>            <C>                                                                                                  <C>
                                                       ARTICLE FOUR
                                                        COVENANTS

   SECTION 4.01.  Payment of Notes  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  31
   SECTION 4.02.  Maintenance of Office or Agency   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  32
   SECTION 4.03.  Limitation on Indebtedness  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  32
   SECTION 4.04.  Limitation on Restricted Payments   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  35
   SECTION 4.05.  Limitation on Dividend and Other Payment Restrictions Affecting
                  Restricted    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  38
   SECTION 4.06.  Limitation on the Issuance and Sale of Capital Stock of Restricted    . . . . . . . . . . . . . . .  39
   SECTION 4.07.  Limitation on Issuances of Guarantees by Restricted Subsidiaries  . . . . . . . . . . . . . . . . .  40
   SECTION 4.08.  Limitation on Transactions with Shareholders and Affiliates   . . . . . . . . . . . . . . . . . . .  40
   SECTION 4.09.  Limitation on Liens   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  41
   SECTION 4.10.  Limitation on Asset Sales   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  42
   SECTION 4.11.  Repurchase of Notes upon a Change of Control  . . . . . . . . . . . . . . . . . . . . . . . . . . .  43
   SECTION 4.12.  Existence   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  43
   SECTION 4.13.  Payment of Taxes and Other Claims   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  43
   SECTION 4.14.  Maintenance of Properties and Insurance   . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  44
   SECTION 4.15.  Notice of Defaults  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  44
   SECTION 4.16.  Compliance Certificates   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  44
   SECTION 4.17.  Commission Reports and Reports to Holders   . . . . . . . . . . . . . . . . . . . . . . . . . . . .  45
   SECTION 4.18.  Waiver of Stay, Extension or Usury Laws   . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  46
   SECTION 4.19.  Limitation on Sale-Leaseback Transactions   . . . . . . . . . . . . . . . . . . . . . . . . . . . .  46

                                                       ARTICLE FIVE
                                                  SUCCESSOR CORPORATION

   SECTION 5.01.  When Company May Merge, Etc.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  47
   SECTION 5.02.  Successor Substituted   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  48

                                                       ARTICLE SIX
                                                   DEFAULT AND REMEDIES

   SECTION 6.01.  Events of Default   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  48
   SECTION 6.02.  Acceleration  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  50
   SECTION 6.03.  Other Remedies  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  50
   SECTION 6.04.  Waiver of Past Defaults   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  50
   SECTION 6.05.  Control by Majority   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  51
   SECTION 6.06.  Limitation on Suits   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  51
   SECTION 6.07.  Rights of Holders to Receive Payment  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  52
   SECTION 6.08.  Collection Suit by Trustee  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  52
   SECTION 6.09.  Trustee May File Proofs of Claim  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  52
</TABLE>
<PAGE>   5
                                      iii

<TABLE>
   <S>            <C>                                                                                                  <C>
   SECTION 6.10.  Priorities  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  52
   SECTION 6.11.  Undertaking for Costs   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  53
   SECTION 6.12.  Restoration of Rights and Remedies  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  53
   SECTION 6.13.  Rights and Remedies Cumulative  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  53
   SECTION 6.14.  Delay or Omission Not Waiver  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  54

                                                      ARTICLE SEVEN
                                                         TRUSTEE

   SECTION 7.01.  General   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  54
   SECTION 7.02.  Certain Rights of Trustee   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  54
   SECTION 7.03.  Individual Rights of Trustee  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  55
   SECTION 7.04.  Trustee's Disclaimer  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  55
   SECTION 7.05.  Notice of Default   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  56
   SECTION 7.06.  Reports by Trustee to Holders   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  56
   SECTION 7.07.  Compensation and Indemnity  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  56
   SECTION 7.08.  Replacement of Trustee  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  57
   SECTION 7.09.  Successor Trustee by Merger, Etc.   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  58
   SECTION 7.10.  Eligibility   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  58
   SECTION 7.11.  Money Held in Trust   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  58
   SECTION 7.12.  Withholding Taxes   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  58

                                                      ARTICLE EIGHT
                                                  DISCHARGE OF INDENTURE

   SECTION 8.01.  Termination of Company's Obligations  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  58
   SECTION 8.02.  Defeasance and Discharge of Indenture   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  59
   SECTION 8.03.  Defeasance of Certain Obligations   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  61
   SECTION 8.04.  Application of Trust Money  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  63
   SECTION 8.05.  Repayment to Company  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  63
   SECTION 8.06.  Reinstatement   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  64

                                                       ARTICLE NINE
                                           AMENDMENTS, SUPPLEMENTS AND WAIVERS

   SECTION 9.01.  Without Consent of Holders  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  64
   SECTION 9.02.  With Consent of Holders   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  65
   SECTION 9.03.  Revocation and Effect of Consent  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  66
   SECTION 9.04.  Notation on or Exchange of Notes  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  66
   SECTION 9.05.  Trustee to Sign Amendments, Etc.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  67
   SECTION 9.06.  Conformity with Trust Indenture Act   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  67
</TABLE>
<PAGE>   6
                                       iv

<TABLE>
   <S>             <C>                                                                                                 <C>
                                                       ARTICLE TEN
                                                         SECURITY

   SECTION 10.01   Security   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  67

                                                      ARTICLE ELEVEN
                                                      MISCELLANEOUS

   SECTION 11.01.  Trust Indenture Act of 1939  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  67
   SECTION 11.02.  Notices  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  67
   SECTION 11.03.  Certificate and Opinion as to Conditions Precedent   . . . . . . . . . . . . . . . . . . . . . . .  68
   SECTION 11.04.  Statements Required in Certificate   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  68
   SECTION 11.05.  Rules by Trustee, Paying Agent or Registrar  . . . . . . . . . . . . . . . . . . . . . . . . . . .  69
   SECTION 11.06.  Payment Date Other Than a Business Day   . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  69
   SECTION 11.07.  Governing Law  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  69
   SECTION 11.08.  No Adverse Interpretation of Other Agreements  . . . . . . . . . . . . . . . . . . . . . . . . . .  69
   SECTION 11.09.  No Recourse Against Others   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  69
   SECTION 11.10.  Successors   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  70
   SECTION 11.11.  Duplicate Originals  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  70
   SECTION 11.12.  Separability   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  70
   SECTION 11.13.  Table of Contents, Headings, Etc.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  70
</TABLE>
<PAGE>   7
                       INDENTURE, dated as of [              ], 1998, between
ALLEGIANCE TELECOM, INC., a Delaware corporation, (the "Company"), and THE BANK
OF NEW YORK, a New York banking corporation, (the "Trustee").

                            RECITALS OF THE COMPANY

                       The Company has duly authorized the execution and
delivery of this Indenture to provide for the issuance initially of up to
$200,000,000 aggregate principal amount of the Company's [    ]% Senior Notes
due 2008 (the "Notes") issuable as provided in this Indenture.  All things
necessary to make this Indenture a valid agreement of the Company, in
accordance with its terms, have been done, and the Company has done all things
necessary to make the Notes, when executed by the Company and authenticated and
delivered by the Trustee hereunder and duly issued by the Company, the valid
obligations of the Company as hereinafter provided.

                       This Indenture is subject to, and shall be governed by,
the provisions of the Trust Indenture Act of 1939, as amended, that are
required to be a part of and to govern indentures qualified under the Trust
Indenture Act of 1939, as amended.

                     AND THIS INDENTURE FURTHER WITNESSETH

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


                                  ARTICLE ONE
                   DEFINITIONS AND INCORPORATION BY REFERENCE

                       SECTION 1.01.  Definitions.

         "Acquired Indebtedness" means Indebtedness of a Person existing at the
time such Person becomes a Restricted Subsidiary or assumed in connection with
an Asset Acquisition by a Restricted Subsidiary and not Incurred in connection
with, or in anticipation of, such Person becoming a Restricted Subsidiary or
such Asset Acquisition.

         "Adjusted Consolidated Net Income" means, for any period, the
aggregate net income (or loss) of the Company and its Restricted Subsidiaries
for such period determined in conformity with GAAP; provided that the following
items shall be excluded in computing Adjusted Consolidated Net Income (without
duplication): (i) the net income (or loss) of any Person that is not a
Restricted Subsidiary, except (x) with respect to net income, to the extent of
the amount of dividends or other distributions actually paid to the Company or
any of its Restricted Subsidiaries by such Person during such period and (y)
with respect to net losses, to the extent of the amount of Investments made by
the Company or any Restricted Subsidiary in such Person during such
<PAGE>   8
                                       2

period; (ii) solely for the purposes of calculating the amount of Restricted
Payments that may be made pursuant to clause (C) of the first paragraph of
Section 4.04 (and in such case, except to the extent includable pursuant to
clause (i) above), the net income (or loss) of any Person accrued prior to the
date it becomes a Restricted Subsidiary or is merged into or consolidated with
the Company or any of its Restricted Subsidiaries or all or substantially all
of the property and assets of such Person are acquired by the Company or any of
its Restricted Subsidiaries; (iii) the net income of any Restricted Subsidiary
to the extent that the declaration or payment of dividends or similar
distributions by such Restricted Subsidiary of such net income is not at the
time permitted by the operation of the terms of its charter or any agreement,
instrument, judgment, decree, order, statute, rule or governmental regulation
applicable to such Restricted Subsidiary; (iv) any gains or losses (on an
after-tax basis) attributable to Asset Sales; (v) except for purposes of
calculating the amount of Restricted Payments that may be made pursuant to
clause (C) of the first paragraph of Section 4.04, any amount paid or accrued
as dividends on Preferred Stock of the Company or any Restricted Subsidiary
owned by Persons other than the Company and any of its Restricted Subsidiaries;
(vi) all extraordinary gains and extraordinary losses; and (vii) any
compensation expense paid or payable solely with Capital Stock (other than
Disqualified Stock) of the Company or any options, warrants or other rights to
acquire Capital Stock (other than Disqualified Stock) of the Company.

         "Adjusted Consolidated Net Tangible Assets" means the total amount of
assets of the Company and its Restricted Subsidiaries (less applicable
depreciation, amortization and other valuation reserves), except to the extent
resulting from write-ups of capital assets (excluding write-ups in connection
with accounting for acquisitions in conformity with GAAP), after deducting
therefrom (i) all current liabilities of the Company and its Restricted
Subsidiaries (excluding intercompany items) and (ii) all goodwill, trade names,
trademarks, patents, unamortized debt discount and expense and other like
intangibles, all as set forth on the most recent quarterly or annual
consolidated balance sheet of the Company and its Restricted Subsidiaries,
prepared in conformity with GAAP and filed with the Commission or provided to
the Trustee pursuant to Section 4.17.

         "Affiliate" means, as applied to any Person, any other Person directly
or indirectly controlling, controlled by, or under direct or indirect common
control with, such Person.  For purposes of this definition, "control"
(including, with correlative meanings, the terms "controlling," "controlled by"
and "under common control with"), as applied to any Person, means the
possession, directly or indirectly, of the power to direct or cause the
direction of the management and policies of such Person, whether through the
ownership of voting securities, by contract or otherwise.

         "Agent" means any Registrar, Paying Agent, authenticating agent or
co-Registrar.

         "Agent Members" has the meaning provided in Section 2.06(a).
<PAGE>   9
                                       3

         "Asset Acquisition" means (i) an investment by the Company or any of
its Restricted Subsidiaries in any other Person pursuant to which such Person
shall become a Restricted Subsidiary or shall be merged into or consolidated
with the Company or any of its Restricted Subsidiaries; provided that such
Person's primary business is related, ancillary or complementary to the
businesses of the Company and its Restricted Subsidiaries on the date of such
investment or (ii) an acquisition by the Company or any of its Restricted
Subsidiaries of the property and assets of any Person other than the Company or
any of its Restricted Subsidiaries that constitute substantially all of a
division or line of business of such Person; provided that the property and
assets acquired are related, ancillary or complementary to the businesses of
the Company and its Restricted Subsidiaries on the date of such acquisition.

         "Asset Disposition" means the sale or other disposition by the Company
or any of its Restricted Subsidiaries (other than to the Company or another
Restricted Subsidiary) of (i) all or substantially all of the Capital Stock of
any Restricted Subsidiary or (ii) all or substantially all of the assets that
constitute a division or line of business of the Company or any of its
Restricted Subsidiaries.

         "Asset Sale" means any sale, transfer or other disposition (including
by way of merger, consolidation or sale- leaseback transaction) in one
transaction or a series of related transactions by the Company or any of its
Restricted Subsidiaries to any Person other than the Company or any of its
Restricted Subsidiaries of (i) all or any of the Capital Stock of any
Restricted Subsidiary, (ii) all or substantially all of the property and assets
of an operating unit or business of the Company or any of its Restricted
Subsidiaries or (iii) any other property and assets (other than the Capital
Stock or other Investment in an Unrestricted Subsidiary) of the Company or any
of its Restricted Subsidiaries outside the ordinary course of business of the
Company or such Restricted Subsidiary and, in each case, that is not governed
by the provisions of Article Five; provided that "Asset Sale" shall not include
(a) sales or other dispositions of inventory, receivables and other current
assets, (b) sales, transfers or other dispositions of assets constituting a
Restricted Payment permitted to be made under Section 4.04, (c) sales,
transfers or other dispositions of assets with a fair market value (as
certified in an Officers' Certificate) not in excess of $1 million in any
transaction or series of related transactions, or (d) sales or other
dispositions of assets for consideration at least equal to the fair market
value of the assets sold or disposed of, to the extent that the consideration
received would constitute property or assets of the kind described in clause
(B) of Section 4.10.

         "Average Life" means, at any date of determination with respect to any
debt security, the quotient obtained by dividing (i) the sum of the products of
(a) the number of years from such date of determination to the dates of each
successive scheduled principal payment of such debt security and (b) the amount
of such principal payment by (ii) the sum of all such principal payments.
<PAGE>   10
                                       4

         "Board of Directors" means the Board of Directors of the Company or
any committee of such Board of Directors duly authorized to act under this
Indenture.

         "Board Resolution" means a copy of a resolution, certified by the
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" means any day except a Saturday, Sunday or other day on
which commercial banks in The City of New York, or in the city of the Corporate
Trust Office of the Trustee, are authorized by law to close.

         "Capital Stock" means, with respect to any Person, any and all shares,
interests, participations or other equivalents (however designated, whether
voting or non-voting) in equity of such Person, whether outstanding on the
Closing Date or issued thereafter, including, without limitation, all Common
Stock and Preferred Stock.

         "Capitalized Lease" means, as applied to any Person, any lease of any
property (whether real, personal or mixed) of which the discounted present
value of the rental obligations of such Person as lessee, in conformity with
GAAP, is required to be capitalized on the balance sheet of such Person.

         "Capitalized Lease Obligations" means the discounted present value of
the rental obligations under a Capitalized Lease.

         "Change of Control" means such time as (i) a "person" or "group"
(within the meaning of Sections 13(d) and 14(d)(2) of the Exchange Act) becomes
the ultimate "beneficial owner" (as defined in Rule 13d-3 under the Exchange
Act) of more than 35% of the total voting power of the Voting Stock of the
Company on a fully diluted basis and such ownership represents a greater
percentage of the total voting power of the Voting Stock of the Company, on a
fully diluted basis, than is held by the Existing Stockholders on such date; or
(ii) individuals who on the Closing Date constitute the Board of Directors
(together with any new directors whose election by the Board of Directors or
whose nomination by the Board of Directors for election by the Company's
stockholders was approved by a vote of at least two- thirds of the members of
the Board of Directors then in office who either were members of the Board of
Directors on the Closing Date or whose election or nomination for election was
previously so approved) cease for any reason to constitute a majority of the
members of the Board of Directors then in office.

         "Closing Date" means the date on which the Notes are originally issued
under this Indenture.

         "Commission" means the Securities and Exchange Commission, as from
time to time constituted, created under the Exchange Act or, if at any time
after the execution of this
<PAGE>   11
                                       5

instrument such Commission is not existing and performing the duties now
assigned to it under the TIA, then the body performing such duties at such
time.

         "Common Stock" means, with respect to any Person, any and all shares,
interests, participations or other equivalents (however designated, whether
voting or non-voting) of such Person's common stock, whether now outstanding or
issued after the date of this Indenture, including, without limitation, all
series and classes of such common stock.

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

         "Company Order" means a written request or order signed in the name of
the Company (i) by its Chairman, a Vice Chairman, its President or a Vice
President and (ii) by its Treasurer, an Assistant Treasurer, its Secretary or
an Assistant Secretary and delivered to the Trustee; provided, however, that
such written request or order may be signed by any two of the officers or
directors listed in clause (i) above in lieu of being signed by one of such
officers or directors listed in such clause (i) and one of the officers listed
in clause (ii) above.

         "Consolidated EBITDA" means, for any period, Adjusted Consolidated Net
Income for such period plus, to the extent such amount was deducted in
calculating such Adjusted Consolidated Net Income, (i) Consolidated Interest
Expense, (ii) income taxes (other than income taxes (either positive or
negative) attributable to extraordinary and non-recurring gains or losses or
sales of assets), (iii) depreciation expense, (iv) amortization expense and (v)
all other non-cash items reducing Adjusted Consolidated Net Income (other than
items that will require cash payments and for which an accrual or reserve is,
or is required by GAAP to be, made), less all non-cash items increasing
Adjusted Consolidated Net Income, all as determined on a consolidated basis for
the Company and its Restricted Subsidiaries in conformity with GAAP; provided
that, if any Restricted Subsidiary is not a Wholly Owned Restricted Subsidiary,
Consolidated EBITDA shall be reduced (to the extent not otherwise reduced in
accordance with GAAP) by an amount equal to (A) the amount of the Adjusted
Consolidated Net Income attributable to such Restricted Subsidiary multiplied
by (B) the percentage ownership interest in the income of such Restricted
Subsidiary not owned on the last day of such period by the Company or any of
its Restricted Subsidiaries.

         "Consolidated Interest Expense" means, for any period, the aggregate
amount of interest in respect of Indebtedness (including, without limitation,
amortization of original issue discount on any Indebtedness and the interest
portion of any deferred payment obligation, calculated in accordance with the
effective interest method of accounting; all commissions, discounts and other
fees and charges owed with respect to letters of credit and bankers' acceptance
financing; the net costs associated with Interest Rate Agreements; and
Indebtedness that is Guaranteed or secured by the Company or any of its
Restricted Subsidiaries) and all but the principal
<PAGE>   12
                                       6

component of rentals in respect of Capitalized Lease Obligations paid, accrued
or scheduled to be paid or to be accrued by the Company and its Restricted
Subsidiaries during such period; excluding, however, (i) any amount of such
interest of any Restricted Subsidiary if the net income of such Restricted
Subsidiary is excluded in the calculation of Adjusted Consolidated Net Income
pursuant to clause (iii) of the definition thereof (but only in the same
proportion as the net income of such Restricted Subsidiary is excluded from the
calculation of Adjusted Consolidated Net Income pursuant to clause (iii) of the
definition thereof) and (ii) any premiums, fees and expenses (and any
amortization thereof) payable in connection with the offering of the Notes and
the concurrent offering of common stock, par value $.01 per share, of the
Company, all as determined on a consolidated basis (without taking into account
Unrestricted Subsidiaries) in conformity with GAAP.

         "Consolidated Leverage Ratio" means, on any Transaction Date, the
ratio of (i) the aggregate amount of Indebtedness of the Company and its
Restricted Subsidiaries on a consolidated basis outstanding on such Transaction
Date to (ii) the aggregate amount of Consolidated EBITDA for the then most
recent four fiscal quarters for which financial statements of the Company have
been filed with the Commission or provided to the Trustee pursuant to Section
4.17 (such four fiscal quarter period being the "Four Quarter Period");
provided that, in making the foregoing calculation, (A) pro forma effect shall
be given to any Indebtedness to be Incurred or repaid on the Transaction Date;
(B) pro forma effect shall be given to Asset Dispositions and Asset
Acquisitions (including giving pro forma effect to the application of proceeds
of any Asset Disposition) that occur from the beginning of the Four Quarter
Period through the Transaction Date (the "Reference Period"), as if they had
occurred and such proceeds had been applied on the first day of such Reference
Period; (C) pro forma effect shall be given to asset dispositions and asset
acquisitions (including giving pro forma effect to the application of proceeds
of any asset disposition) that have been made by any Person that has become a
Restricted Subsidiary or has been merged with or into the Company or any
Restricted Subsidiary during such Reference Period and that would have
constituted Asset Dispositions or Asset Acquisitions had such transactions
occurred when such Person was a Restricted Subsidiary as if such asset
dispositions or asset acquisitions were Asset Dispositions or Asset
Acquisitions that occurred on the first day of such Reference Period; provided
that to the extent that clause (B) or (C) of this sentence requires that pro
forma effect be given to an Asset Acquisition or Asset Disposition, such pro
forma calculation shall be based upon the four full fiscal quarters immediately
preceding the Transaction Date of the Person, or division or line of business
of the Person, that is acquired or disposed of for which financial information
is available; and (D) the aggregate amount of Indebtedness outstanding as of
the end of the Reference Period will be deemed to include the total amount of
funds outstanding and/or available on the Transaction Date under any revolving
credit or similar facilities of the Company or its Restricted Subsidiaries.

         "Consolidated Net Worth" means, at any date of determination,
stockholders' equity as set forth on the most recently available quarterly or
annual consolidated balance sheet of the Company and its Restricted
Subsidiaries (which shall be as of a date not more than 90 days prior
<PAGE>   13
                                       7

to the date of such computation, and which shall not take into account
Unrestricted Subsidiaries), less any amounts attributable to Disqualified Stock
or any equity security convertible into or exchangeable for Indebtedness, the
cost of treasury stock and the principal amount of any promissory notes
receivable from the sale of the Capital Stock of the Company or any of its
Restricted Subsidiaries, each item to be determined in conformity with GAAP
(excluding the effects of foreign currency exchange adjustments under Financial
Accounting Standards Board Statement of Financial Accounting Standards No. 52).

         "Corporate Trust Office" means the office of the Trustee at which the
corporate trust business of the Trustee shall, at any particular time, be
principally administered, which office is, at the date of this Indenture,
located at 101 Barclay Street, 21 West, New York, New York 10286, Attention:
Corporate Trust Administration.

         "Currency Agreement" means any foreign exchange contract, currency
swap agreement or other similar agreement or arrangement.

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

         "Depositary" means The Depository Trust Company, its nominees, and
their respective successors.

         "Disqualified Stock" means any class or series of Capital Stock of any
Person that by its terms or otherwise is (i) required to be redeemed prior to
the Stated Maturity of the Notes, (ii) redeemable at the option of the holder
of such class or series of Capital Stock at any time prior to the Stated
Maturity of the Notes or (iii) convertible into or exchangeable for Capital
Stock referred to in clause (i) or (ii) above or Indebtedness having a
scheduled maturity prior to the Stated Maturity of the Notes; provided that any
Capital Stock that would not constitute Disqualified Stock but for provisions
thereof giving holders thereof the right to require such Person to repurchase
or redeem such Capital Stock upon the occurrence of an "asset sale" or "change
of control" occurring prior to the Stated Maturity of the Notes shall not
constitute Disqualified Stock if the "asset sale" or "change of control"
provisions applicable to such Capital Stock are no more favorable to the
holders of such Capital Stock than the provisions contained in Section 4.10 and
Section 4.11 and such Capital Stock, or the agreements or instruments governing
the redemption rights thereof, specifically provides that such Person will not
repurchase or redeem any such stock pursuant to such provision prior to the
Company's repurchase of such Notes as are required to be repurchased pursuant
to Section 4.10 and Section 4.11.

         "Event of Default" has the meaning provided in Section 6.01.

         "Excess Proceeds" has the meaning provided in Section 4.10.
<PAGE>   14
                                       8


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

         "Existing Stockholders" means Madison Dearborn Partners, Inc., Morgan
Stanley Capital Partners III, Inc., Frontenac Company, Battery Partners IV,
L.P. and Battery Investment Partners IV, LLC and their respective Affiliates.

         "fair market value" means the price that would be paid in an
arm's-length transaction between an informed and willing seller under no
compulsion to sell and an informed and willing buyer under no compulsion to
buy, as determined in good faith by the Board of Directors, whose determination
shall be conclusive if evidenced by a Board Resolution; provided that for
purposes of clause (viii) of the second paragraph of Section 4.03, (x) the fair
market value of any security registered under the Exchange Act shall be the
average of the closing prices, regular way, of such security for the 20
consecutive trading days immediately preceding the sale of Capital Stock and
(y) in the event the aggregate fair market value of any other property (other
than cash or cash equivalents) received by the Company exceeds $10 million, the
fair market value of such property shall be determined by a nationally
recognized investment banking firm and set forth in their written opinion which
shall be delivered to the Trustee.

         "Fund Investors" has the meaning specified in the definition of
"Existing Stockholders."

         "GAAP" means generally accepted accounting principles in the United
States of America as in effect as of the Closing Date, including, without
limitation, those set forth in the opinions and pronouncements of the
Accounting Principles Board of the American Institute of Certified Public
Accountants and statements and pronouncements of the Financial Accounting
Standards Board or in such other statements by such other entity as approved by
a significant segment of the accounting profession. All ratios and computations
contained or referred to in this Indenture shall be computed in conformity with
GAAP applied on a consistent basis, except that calculations made for purposes
of determining compliance with the terms of the covenants and with other
provisions of this Indenture shall be made without giving effect to (i) the
amortization of any expenses incurred in connection with the offering of the
Notes and the concurrent offering of common stock, par value $.01 per share, of
the Company and (ii) except as otherwise provided, the amortization of any
amounts required or permitted by Accounting Principles Board Opinion Nos. 16
and 17.

         "Global Notes" has the meaning provided in Section 2.01.

         "Guarantee" means any obligation, contingent or otherwise, of any
Person directly or indirectly guaranteeing any Indebtedness of any other Person
and, without limiting the generality of the foregoing, any obligation, direct
or indirect, contingent or otherwise, of such Person (i) to purchase or pay (or
advance or supply funds for the purchase or payment of) such Indebtedness of
such other Person (whether arising by virtue of partnership arrangements, or by
agreements to keep-well, to purchase assets, goods, securities or services
(unless such purchase arrangements
<PAGE>   15
                                       9

are on arm's-length terms and are entered into in the ordinary course of
business), to take-or-pay, or to maintain financial statement conditions or
otherwise) or (ii) entered into for purposes of assuring in any other manner
the obligee of such Indebtedness of the payment thereof or to protect such
obligee against loss in respect thereof (in whole or in part); provided that
the term "Guarantee" shall not include endorsements for collection or deposit
in the ordinary course of business. The term "Guarantee" used as a verb has a
corresponding meaning.

         "Guaranteed Indebtedness" has the meaning provided in Section 4.07.

         "Holder" or "Noteholder" means the registered holder of any Note.

         "Incur" means, with respect to any Indebtedness, to incur, create,
issue, assume, Guarantee or otherwise become liable for or with respect to, or
become responsible for, the payment of, contingently or otherwise, such
Indebtedness, including an "Incurrence" of Acquired Indebtedness; provided that
neither the accrual of interest nor the accretion of original issue discount
shall be considered an Incurrence of Indebtedness.

         "Indebtedness" means, with respect to any Person at any date of
determination (without duplication), (i) all indebtedness of such Person for
borrowed money, (ii) all obligations of such Person evidenced by bonds,
debentures, notes or other similar instruments, (iii) all obligations of such
Person in respect of letters of credit or other similar instruments (including
reimbursement obligations with respect thereto, but excluding obligations with
respect to letters of credit (including trade letters of credit) securing
obligations (other than obligations described in (i) or (ii) above or (v), (vi)
or (vii) below) entered into in the ordinary course of business of such Person
to the extent such letters of credit are not drawn upon or, if drawn upon, to
the extent such drawing is reimbursed no later than the third Business Day
following receipt by such Person of a demand for reimbursement), (iv) all
obligations of such Person to pay the deferred and unpaid purchase price of
property or services, which purchase price is due more than six months after
the date of placing such property in service or taking delivery and title
thereto or the completion of such services, except Trade Payables, (v) all
Capitalized Lease Obligations of such Person, (vi) all Indebtedness of other
Persons secured by a Lien on any asset of such Person, whether or not such
Indebtedness is assumed by such Person; provided that the amount of such
Indebtedness shall be the lesser of (A) the fair market value of such asset at
such date of determination and (B) the amount of such Indebtedness, (vii) all
Indebtedness of other Persons Guaranteed by such Person to the extent such
Indebtedness is Guaranteed by such Person and (viii) to the extent not
otherwise included in this definition, obligations under Currency Agreements
and Interest Rate Agreements. The amount of Indebtedness of any Person at any
date shall be the outstanding balance at such date (or, in the case of a
revolving credit or other similar facility, the total amount of funds
outstanding and/or available on the date of determination) of all unconditional
obligations as described above and, with respect to contingent obligations, the
maximum liability upon the occurrence of the contingency giving rise to the
obligation, provided (A) that the amount outstanding at any time of any
Indebtedness issued with original issue discount is the
<PAGE>   16
                                       10

face amount of such Indebtedness less the remaining unamortized portion of the
original issue discount of such Indebtedness at the time of its issuance as
determined in conformity with GAAP, (B) that money borrowed and set aside at
the time of the Incurrence of any Indebtedness in order to prefund the payment
of the interest on such Indebtedness shall not be deemed to be "Indebtedness"
so long as such money is held to secure the payment of such interest and (C)
that Indebtedness shall not include any liability for federal, state, local or
other taxes.

         "Indenture" means this Indenture as originally executed or as it may
be amended or supplemented from time to time by one or more indentures
supplemental to this Indenture entered into pursuant to the applicable
provisions of this Indenture.

         "Interest Payment Date" means each semiannual interest payment date on
May 15 and November 15, of each year, commencing November 15, 1998.

         "Interest Rate Agreement" means any interest rate protection
agreement, interest rate future agreement, interest rate option agreement,
interest rate swap agreement, interest rate cap agreement, interest rate collar
agreement, interest rate hedge agreement, option or future contract or other
similar agreement or arrangement.

         "Investment" in any Person means any direct or indirect advance, loan
or other extension of credit (including, without limitation, by way of
Guarantee or similar arrangement; but excluding advances to customers in the
ordinary course of business that are, in conformity with GAAP, recorded as
accounts receivable on the balance sheet of the Company or its Restricted
Subsidiaries) or capital contribution to (by means of any transfer of cash or
other property to others or any payment for property or services for the
account or use of others), or any purchase or acquisition of Capital Stock,
bonds, notes, debentures or other similar instruments issued by, such Person
and shall include (i) the designation of a Restricted Subsidiary as an
Unrestricted Subsidiary and (ii) the fair market value of the Capital Stock (or
any other Investment), held by the Company or any of its Restricted
Subsidiaries, of (or in) any Person that has ceased to be a Restricted
Subsidiary, including without limitation, by reason of any transaction
permitted by clause (iii) of Section 4.06; provided that the fair market value
of the Investment remaining in any Person that has ceased to be a Restricted
Subsidiary shall not exceed the aggregate amount of Investments previously made
in such Person valued at the time such Investments were made less the net
reduction of such Investments. For purposes of the definition of "Unrestricted
Subsidiary" and Section 4.04, (i) "Investment" shall include the fair market
value of the assets (net of liabilities (other than liabilities to the Company
or any of its Restricted Subsidiaries)) of any Restricted Subsidiary at the
time that such Restricted Subsidiary is designated an Unrestricted Subsidiary,
(ii) the fair market value of the assets (net of liabilities (other than
liabilities to the Company or any of its Restricted Subsidiaries)) of any
Unrestricted Subsidiary at the time that such Unrestricted Subsidiary is
designated a Restricted Subsidiary shall be considered a reduction in
outstanding Investments and (iii) any property transferred to or from an
Unrestricted Subsidiary shall be valued at its fair market value at the time of
such transfer.
<PAGE>   17
                                       11

         "Lien" means any mortgage, pledge, security interest, encumbrance,
lien or charge of any kind (including, without limitation, any conditional sale
or other title retention agreement or lease in the nature thereof or any
agreement to give any security interest).

         "Moody's" means Moody's Investors Service, Inc. and its successors.

         "Net Cash Proceeds" means, (a) with respect to any Asset Sale, the
proceeds of such Asset Sale in the form of cash or cash equivalents, including
payments in respect of deferred payment obligations (to the extent
corresponding to the principal, but not interest, component thereof) when
received in the form of cash or cash equivalents (except to the extent such
obligations are financed or sold with recourse to the Company or any Restricted
Subsidiary) and proceeds from the conversion of other property received when
converted to cash or cash equivalents, net of (i) brokerage commissions and
other fees and expenses (including fees and expenses of counsel and investment
bankers) related to such Asset Sale, (ii) provisions for all taxes (whether or
not such taxes will actually be paid or are payable) as a result of such Asset
Sale without regard to the consolidated results of operations of the Company
and its Restricted Subsidiaries, taken as a whole, (iii) payments made to repay
Indebtedness or any other obligation outstanding at the time of such Asset Sale
that either (A) is secured by a Lien on the property or assets sold or (B) is
required to be paid as a result of such sale and (iv) appropriate amounts to be
provided by the Company or any Restricted Subsidiary as a reserve against any
liabilities associated with such Asset Sale, including, without limitation,
pension and other post-employment benefit liabilities, liabilities related to
environmental matters and liabilities under any indemnification obligations
associated with such Asset Sale, all as determined in conformity with GAAP and
(b) with respect to any issuance or sale of Capital Stock, the proceeds of such
issuance or sale in the form of cash or cash equivalents, including payments in
respect of deferred payment obligations (to the extent corresponding to the
principal, but not interest, component thereof) when received in the form of
cash or cash equivalents (except to the extent such obligations are financed or
sold with recourse to the Company or any Restricted Subsidiary) and proceeds
from the conversion of other property received when converted to cash or cash
equivalents, net of attorney's fees, accountants' fees, underwriters' or
placement agents' fees, discounts or commissions and brokerage, consultant and
other fees incurred in connection with such issuance or sale and net of taxes
paid or payable as a result thereof.

         "Notes" means any of the securities, as defined in the first paragraph
of the recitals hereof, that are authenticated and delivered under this
Indenture.  For all purposes of this Indenture, the term "Notes" shall include
the Notes initially issued on the Closing Date and any other Notes issued after
the Closing Date under this Indenture.  For purposes of this Indenture, all
Notes shall vote together as one series of Notes under this Indenture.

         "Offer to Purchase" means an offer to purchase Notes by the Company
from the Holders commenced by mailing a notice to the Trustee and each Holder
stating: (i) the covenant pursuant to which the offer is being made and that
all Notes validly tendered will be accepted for payment
<PAGE>   18
                                       12

on a pro rata basis; (ii) the purchase price and the date of purchase (which
shall be a Business Day no earlier than 30 days nor later than 60 days from the
date such notice is mailed) (the "Payment Date"); (iii) that any Note not
tendered will continue to accrue interest pursuant to its terms; (iv) that,
unless the Company defaults in the payment of the purchase price, any Note
accepted for payment pursuant to the Offer to Purchase shall cease to accrue
interest on and after the Payment Date; (v) that Holders electing to have a
Note purchased pursuant to the Offer to Purchase will be required to surrender
the Note, together with the form entitled "Option of the Holder to Elect
Purchase" on the reverse side of the Note completed, to the Paying Agent at the
address specified in the notice prior to the close of business on the Business
Day immediately preceding the Payment Date; (vi) that Holders will be entitled
to withdraw their election if the Paying Agent receives, not later than the
close of business on the third Business Day immediately preceding the Payment
Date, a telegram, facsimile transmission or letter setting forth the name of
such Holder, the principal amount of Notes delivered for purchase and a
statement that such Holder is withdrawing his election to have such Notes
purchased; and (vii) that Holders whose Notes are being purchased only in part
will be issued new Notes equal in principal amount to the unpurchased portion
of the Notes surrendered; provided that each Note purchased and each new Note
issued shall be in a principal amount of $1,000 or an integral multiple
thereof. On the Payment Date, the Company shall (i) accept for payment on a pro
rata basis Notes or portions thereof tendered pursuant to an Offer to Purchase;
(ii) deposit with the Paying Agent money sufficient to pay the purchase price
of all Notes or portions thereof so accepted; and (iii) deliver, or cause to be
delivered, to the Trustee all Notes or portions thereof so accepted together
with an Officers' Certificate specifying the Notes or portions thereof accepted
for payment by the Company. The Paying Agent shall promptly mail to the Holders
of Notes so accepted payment in an amount equal to the purchase price, and the
Trustee shall promptly authenticate and mail to such Holders a new Note equal
in principal amount to any unpurchased portion of the Note surrendered;
provided that each Note purchased and each new Note issued shall be in a
principal amount of $1,000 or an integral multiple thereof. The Company will
publicly announce the results of an Offer to Purchase as soon as practicable
after the Payment Date. The Trustee shall act as the Paying Agent for an Offer
to Purchase. The Company will comply with Rule 14e-1 under the Exchange Act and
any other securities laws and regulations thereunder to the extent such laws
and regulations are applicable, in the event that the Company is required to
repurchase Notes pursuant to an Offer to Purchase.

         "Officer" means, with respect to the Company, (i) the Chairman of the
Board, the President, any Vice President, the Chief Financial Officer, and (ii)
the Treasurer or any Assistant Treasurer, or the Secretary or any Assistant
Secretary.

         "Officers' Certificate" means a certificate signed by one Officer
listed in clause (i) of the definition thereof and one Officer listed in clause
(ii) of the definition thereof.  Each Officers' Certificate (other than
certificates provided pursuant to TIA Section 314(a)(4)) shall include the
statements provided for in TIA Section 314(e).
<PAGE>   19
                                       13

         "Opinion of Counsel" means a written opinion signed by legal counsel
who may be an employee of or counsel to the Company.  Each such Opinion of
Counsel shall include the statements provided for in TIA Section 314(e) to the
extent required by law.

         "Paying Agent" has the meaning provided in Section 2.03, except that,
for the purposes of Article Eight, the Paying Agent shall not be the Company or
a Subsidiary of the Company or an Affiliate of any of them.  The term "Paying
Agent" includes any additional Paying Agent.

         "Payment Date" has the meaning specified in the definition of "Offer to
Purchase."

         "Permitted Investment" means (i) an Investment in the Company or a
Restricted Subsidiary or a Person which will, upon the making of such
Investment, become a Restricted Subsidiary or be merged or consolidated with or
into or transfer or convey all or substantially all its assets to, the Company
or a Restricted Subsidiary; provided that such person's primary business is
related, ancillary or complementary to the businesses of the Company and its
Restricted Subsidiaries on the date of such Investment; (ii) Temporary Cash
Investments; (iii) payroll, travel and similar advances to cover matters that
are expected at the time of such advances ultimately to be treated as expenses
in accordance with GAAP; (iv) stock, obligations or securities received in
satisfaction of judgments; (v) Investments in prepaid expenses, negotiable
instruments held for collection and lease, utility and worker's compensation,
performance and other similar deposits; (vi) Interest Rate Agreements and
Currency Agreements designed solely to protect the Company or its Restricted
Subsidiaries against fluctuations in interest rates or foreign currency
exchange rates; and (vii) loans or advances to officers or employees of the
Company or any Restricted Subsidiary that do not in the aggregate exceed $2
million at any time outstanding.

         "Permitted Liens" means (i) Liens for taxes, assessments, governmental
charges or claims that are being contested in good faith by appropriate legal
proceedings promptly instituted and diligently conducted and for which a
reserve or other appropriate provision, if any, as shall be required in
conformity with GAAP shall have been made; (ii) statutory and common law Liens
of landlords and carriers, warehousemen, mechanics, suppliers, materialmen,
repairmen or other similar Liens arising in the ordinary course of business and
with respect to amounts not yet delinquent or being contested in good faith by
appropriate legal proceedings promptly instituted and diligently conducted and
for which a reserve or other appropriate provision, if any, as shall be
required in conformity with GAAP shall have been made; (iii) Liens incurred or
deposits made in the ordinary course of business in connection with workers'
compensation, unemployment insurance and other types of social security; (iv)
Liens incurred or deposits made to secure the performance of tenders, bids,
leases, statutory or regulatory obligations, bankers' acceptances, surety and
appeal bonds, government contracts, performance and return-of-money bonds and
other obligations of a similar nature incurred in the ordinary course of
business (exclusive of obligations for the payment of borrowed money); (v)
easements, rights-of- way, municipal and zoning ordinances and similar charges,
encumbrances, title defects or other
<PAGE>   20
                                       14

irregularities that do not materially interfere with the ordinary course of
business of the Company or any of its Restricted Subsidiaries; (vi) Liens
(including extensions and renewals thereof) upon real or personal property
acquired after the Closing Date; provided that (a) such Lien is created solely
for the purpose of securing Indebtedness Incurred, in accordance with Section
4.03, to finance the cost (including the cost of design, development,
acquisition, construction, installation, improvement, transportation or
integration) of the item of property or assets subject thereto and such Lien is
created prior to, at the time of or within six months after the later of the
acquisition, the completion of construction or the commencement of full
operation of such property, (b) the principal amount of the Indebtedness
secured by such Lien does not exceed 100% of such cost and (c) any such Lien
shall not extend to or cover any property or assets other than such item of
property or assets and any improvements on such item; (vii) leases or subleases
granted to others that do not materially interfere with the ordinary course of
business of the Company and its Restricted Subsidiaries, taken as a whole;
(viii) Liens encumbering property or assets under construction arising from
progress or partial payments by a customer of the Company or its Restricted
Subsidiaries relating to such property or assets; (ix) any interest or title of
a lessor in the property subject to any Capitalized Lease or operating lease;
(x) Liens arising from filing Uniform Commercial Code financing statements
regarding leases; (xi) Liens on property of, or on shares of Capital Stock or
Indebtedness of, any Person existing at the time such Person becomes, or
becomes a part of, any Restricted Subsidiary; provided that such Liens do not
extend to or cover any property or assets of the Company or any Restricted
Subsidiary other than the property or assets acquired; (xii) Liens in favor of
the Company or any Restricted Subsidiary; (xiii) Liens arising from the
rendering of a final judgment or order against the Company or any Restricted
Subsidiary that does not give rise to an Event of Default; (xiv) Liens securing
reimbursement obligations with respect to letters of credit that encumber
documents and other property relating to such letters of credit and the
products and proceeds thereof; (xv) Liens in favor of customs and revenue
authorities arising as a matter of law to secure payment of customs duties in
connection with the importation of goods; (xvi) Liens encumbering customary
initial deposits and margin deposits, and other Liens that are within the
general parameters customary in the industry and incurred in the ordinary
course of business, in each case, securing Indebtedness under Interest Rate
Agreements and Currency Agreements and forward contracts, options, future
contracts, futures options or similar agreements or arrangements designed
solely to protect the Company or any of its Restricted Subsidiaries from
fluctuations in interest rates, currencies or the price of commodities; (xvii)
Liens arising out of conditional sale, title retention, consignment or similar
arrangements for the sale of goods entered into by the Company or any of its
Restricted Subsidiaries in the ordinary course of business in accordance with
the past practices of the Company and its Restricted Subsidiaries prior to the
Closing Date; (xviii) Liens on or sales of receivables; and (xix) Liens that
secure Indebtedness with an aggregate principal amount not in excess of $5
million at any time outstanding.

         "Person" means an individual, a corporation, a partnership, a limited
liability company, an association, a trust or any other entity or organization,
including a government or political subdivision or an agency or instrumentality
thereof.
<PAGE>   21
                                       15


         "Physical Notes" has the meaning provided in Section 2.06.

         "Pledge Account" means an account established with the Trustee
pursuant to the terms of the Pledge Agreement for the deposit of the Pledged
Securities to be purchased by the Company with the net proceeds from the sale
of the Notes.

         "Pledge Agreement" means the Collateral Pledge and Security Agreement,
dated as of the Closing Date, made by the Company in favor of the Trustee,
governing the disbursement of funds from the Pledge Account, as such agreement
may be amended, restated, supplemented or otherwise modified from time to time.

         "Pledged Securities" means the U.S. government securities to be
purchased by the Company and held in the Pledge Account in accordance with the
Pledge Agreement

         "Preferred Stock" means, with respect to any Person, any and all
shares, interests, participations or other equivalents (however designated,
whether voting or non-voting) of such Person's preferred or preference stock,
whether now outstanding or issued after the date of this Indenture, including,
without limitation, all series and classes of such preferred or preference
stock.

         "principal" of a debt security, including the Notes, means the
principal amount due on the Stated Maturity as shown on such debt security.

         "Public Equity Offering" means an underwritten primary public offering
of Common Stock of the Company pursuant to an effective registration statement
under the Securities Act.

         A "Public Market" shall be deemed to exist if (i) a Public Equity
Offering has been consummated and (ii) at least 15% of the total issued and
outstanding Common Stock of the Company immediately prior to the consummation
of such Public Equity Offering has been distributed by means of an effective
registration statement under the Securities Act or sales pursuant to Rule 144
under the Securities Act.

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

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

         "Registrar" has the meaning provided in Section 2.03.
<PAGE>   22
                                       16

         "Regular Record Date" for the interest payable on any Interest Payment
Date means the May 1 or November 1 (whether or not a Business Day), as the case
may be, next preceding such Interest Payment Date.

         "Repurchase Offer" has the meaning provided in the Warrant Agreement,
dated as of February 3, 1998, between the Company and The Bank of New York, as
warrant agent.

         "Responsible Officer", when used with respect to the Trustee, means
the chairman or any vice chairman of the board of directors, the chairman or
any vice chairman of the executive committee of the board of directors, the
chairman of the trust committee, the president, any vice president, any
assistant vice president, the secretary, any assistant secretary, the
treasurer, any assistant treasurer, the cashier, any assistant cashier, any
trust officer or assistant trust officer, the controller or any assistant
controller or any other officer of the Trustee customarily performing functions
similar to those performed by any of the above designated officers and also
means, with respect to a particular corporate trust matter, any other officer
to whom such matter is referred because of his or her knowledge of and
familiarity with the particular subject.

         "Restricted Payments" has the meaning provided in Section 4.04.

         "Restricted Subsidiary" means any Subsidiary of the Company other than
an Unrestricted Subsidiary.

         "Security Register" has the meaning provided in Section 2.03.

         "Securities Act" means the Securities Act of 1933, as amended.

         "Significant Subsidiary" means, at any date of determination, any
Restricted Subsidiary that, together with its Subsidiaries, (i) for the most
recent fiscal year of the Company, accounted for more than 10% of the
consolidated revenues of the Company and its Restricted Subsidiaries or (ii) as
of the end of such fiscal year, was the owner of more than 10% of the
consolidated assets of the Company and its Restricted Subsidiaries, all as set
forth on the most recently available consolidated financial statements of the
Company for such fiscal year.

         "S&P" means Standard & Poor's Ratings Services and its successors.

         "Stated Maturity" means, (i) with respect to any debt security, the
date specified in such debt security as the fixed date on which the final
installment of principal of such debt security is due and payable and (ii) with
respect to any scheduled installment of principal of or interest on any debt
security, the date specified in such debt security as the fixed date on which
such installment is due and payable.
<PAGE>   23
                                       17

         "Strategic Subordinated Indebtedness" means Indebtedness of the
Company Incurred to finance the acquisition of a Person engaged in a business
that is related, ancillary or complementary to the business conducted by the
Company or any of its Restricted Subsidiaries, which Indebtedness by its terms,
or by the terms of any agreement or instrument pursuant to which such
Indebtedness is Incurred, (i) is expressly made subordinate in right of payment
to the Notes and (ii) provides that no payment of principal, premium or
interest on, or any other payment with respect to, such Indebtedness may be
made prior to the payment in full of all of the Company's obligations under the
Notes; provided that such Indebtedness may provide for and be repaid at any
time from the proceeds of a capital contribution or the sale of Capital Stock
(other than Disqualified Stock) of the Company after the Incurrence of such
Indebtedness.

         "Subsidiary" means, with respect to any Person, any corporation,
association or other business entity of which more than 50% of the voting power
of the outstanding Voting Stock is owned, directly or indirectly, by such
Person and one or more other Subsidiaries of such Person.

         "Temporary Cash Investment" means any of the following:  (i) direct
obligations of the United States of America or any agency thereof or
obligations fully and unconditionally guaranteed by the United States of
America or any agency thereof, (ii) time deposit accounts, certificates of
deposit and money market deposits maturing within one year of the date of
acquisition thereof issued by a bank or trust company which is organized under
the laws of the United States of America, any state thereof or any foreign
country recognized by the United States of America, and which bank or trust
company has capital, surplus and undivided profits aggregating in excess of $50
million (or the foreign currency equivalent thereof) and has outstanding debt
which is rated "A" (or such similar equivalent rating) or higher by at least
one nationally recognized statistical rating organization (as defined in Rule
436 under the Securities Act) or any money-market fund sponsored by a
registered broker dealer or mutual fund distributor, (iii) repurchase
obligations with a term of not more than 30 days for underlying securities of
the types described in clause (i) above entered into with a bank meeting the
qualifications described in clause (ii) above, (iv) commercial paper, maturing
not more than one year after the date of acquisition, issued by a corporation
(other than an Affiliate of the Company) organized and in existence under the
laws of the United States of America, any state thereof or any foreign country
recognized by the United States of America with a rating at the time as of
which any investment therein is made of "P-1" (or higher) according to Moody's
or "A-1" (or higher) according to S&P, and (v) securities with maturities of
six months or less from the date of acquisition issued or fully and
unconditionally guaranteed by any state, commonwealth or territory of the
United States of America, or by any political subdivision or taxing authority
thereof, and rated at least "A" by S&P or Moody's.

         "TIA" or "Trust Indenture Act" means the Trust Indenture Act of 1939,
as amended (15 U.S. Code Sections  77aaa- 77bbb), as in effect on the date this
Indenture was executed, except as provided in Section 9.06.
<PAGE>   24
                                       18

         "Trade Payables" means, with respect to any Person, any accounts
payable or any other indebtedness or monetary obligation to trade creditors
created, assumed or Guaranteed by such Person or any of its Subsidiaries
arising in the ordinary course of business in connection with the acquisition
of goods or services.

         "Transaction Date" means, with respect to the Incurrence of any
Indebtedness by the Company or any of its Restricted Subsidiaries, the date
such Indebtedness is to be Incurred and, with respect to any Restricted
Payment, the date such Restricted Payment is to be made.

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

         "United States Bankruptcy Code" means the Bankruptcy Reform Act of
1978, as amended and as codified in Title 11 of the United States Code, as
amended from time to time hereafter, or any successor federal bankruptcy law.

         "U.S. Government Obligations" means securities that are (i) direct
obligations of the United States of America for the payment of which its full
faith and credit is pledged or (ii) obligations 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,
are not callable or redeemable at the option of the issuer thereof at any time
prior to the Stated Maturity of the Notes, and shall also include a depository
receipt issued by a bank or trust company as custodian with respect to any such
U.S.  Government Obligation or a specific payment of interest on or principal
of any such U.S. Government Obligation held by such custodian for the account
of the holder of a depository receipt; 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 depository receipt from any amount received by
the custodian in respect of the U.S. Government Obligation or the specific
payment of interest on or principal of the U.S. Government Obligation evidenced
by such depository receipt.

         "Unrestricted Subsidiary" means (i) any Subsidiary of the Company that
at the time of determination shall be designated an Unrestricted Subsidiary by
the Board of Directors in the manner provided below; and (ii) any Subsidiary of
an Unrestricted Subsidiary. The Board of Directors may designate any Restricted
Subsidiary (including any newly acquired or newly formed Subsidiary of the
Company) to be an Unrestricted Subsidiary unless such Subsidiary owns any
Capital Stock of, or owns or holds any Lien on any property of, the Company or
any Restricted Subsidiary; provided that (A) any Guarantee by the Company or
any Restricted Subsidiary of any Indebtedness of the Subsidiary being so
designated shall be deemed an "Incurrence" of such Indebtedness and an
"Investment" by the Company or such Restricted Subsidiary (or both, if
applicable) at the time of such designation; (B) either (I) the Subsidiary to
<PAGE>   25
                                       19

be so designated has total assets of $1,000 or less or (II) if such Subsidiary
has assets greater than $1,000, such designation would be permitted under
Section 4.04 and (C) if applicable, the Incurrence of Indebtedness and the
Investment referred to in clause (A) of this proviso would be permitted under
Section 4.03 and Section 4.04.  The Board of Directors may designate any
Unrestricted Subsidiary to be a Restricted Subsidiary; provided that (i) no
Default or Event of Default shall have occurred and be continuing at the time
of or after giving effect to such designation and (ii) all Liens and
Indebtedness of such Unrestricted Subsidiary outstanding immediately after such
designation would, if Incurred at such time, have been permitted to be Incurred
(and shall be deemed to have been Incurred) for all purposes of this Indenture.
Any such designation by the Board of Directors shall be evidenced to the
Trustee by promptly filing with the Trustee a copy of the Board Resolution
giving effect to such designation and an Officers' Certificate certifying that
such designation complied with the foregoing provisions.

         "Voting Stock" means with respect to any Person, Capital Stock of any
class or kind ordinarily having the power to vote for the election of
directors, managers or other voting members of the governing body of such
Person.

         "Warrants" means the warrants to purchase Common Stock of the Company
issued pursuant to a Warrant Agreement, dated as of February 3, 1998, between
the Company and The Bank of New York, as warrant agent.

         "Wholly Owned" means, with respect to any Subsidiary of any Person,
the ownership of all of the outstanding Capital Stock of such Subsidiary (other
than any director's qualifying shares or Investments by foreign nationals
mandated by applicable law) by such Person or one or more Wholly Owned
Subsidiaries of such Person.

                 SECTION 1.02.  Incorporation by Reference of Trust Indenture
Act.  Whenever this Indenture refers to a provision of the TIA, the provision
is incorporated by reference in and made a part of this Indenture.  The
following TIA terms used in this Indenture have the following meanings:

                 "indenture notes" means the Notes;

                 "indenture note holder" means a Holder or a Noteholder;

                 "indenture to be qualified" means this Indenture;

                 "indenture trustee" or "institutional trustee" means the
         Trustee; and

                 "obligor" on the indenture securities means the Company or any
         other obligor on the Notes.
<PAGE>   26
                                       20

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

                 SECTION 1.03.  Rules of Construction.  Unless the context
otherwise requires:

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

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

                 (iii)    "or" is not exclusive;

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

                 (v)      provisions apply to successive events and
         transactions;

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

                 (vii)    all ratios and computations based on GAAP contained
         in this Indenture shall be computed in accordance with the definition
         of GAAP set forth in Section 1.01; and

                 (viii)   all references to Sections or Articles refer to
         Sections or Articles of this Indenture unless otherwise indicated.


                                  ARTICLE TWO
                                   THE NOTES

                 SECTION 2.01.  Form and Dating.  The Notes and the Trustee's
certificate of authentication shall be substantially in the form annexed hereto
as Exhibit A with such appropriate insertions, omissions, substitutions and
other variations as are required or permitted by this Indenture.  The Notes may
have notations, legends or endorsements required by law, stock exchange
agreements to which the Company is subject or usage.  The Company shall approve
the form of the Notes and any notation, legend or endorsement on the Notes.
Each Note shall be dated the date of its authentication.

                 The terms and provisions contained in the form of the Notes
annexed hereto as Exhibit A shall constitute, and are hereby expressly made, a
part of this Indenture.  To the extent
<PAGE>   27
                                       21

applicable, the Company and the Trustee, by their execution and delivery of
this Indenture, expressly agree to such terms and provisions and to be bound
thereby.

                 The Notes shall be issued initially in the form of one or more
global Notes in registered form, substantially in the form set forth in Exhibit
A (the "Global Notes"), deposited with the Trustee, as custodian for the
Depositary, duly executed by the Company and authenticated by the Trustee as
hereinafter provided.  Each Global Note shall bear such legends as may be
required or reasonably requested by the Depositary.

                 The definitive Notes shall be typed, printed, lithographed or
engraved or produced by any combination of these methods or may be produced in
any other manner permitted by the rules of any securities exchange on which the
Notes may be listed, all as determined by the Officers executing such Notes, as
evidenced by their execution of such Notes.

                 Each Global Note shall also bear the following legend on the
face thereof:

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

         TRANSFERS OF THIS GLOBAL NOTE SHALL BE LIMITED TO TRANSFERS IN WHOLE,
         BUT NOT IN PART, TO NOMINEES OF CEDE & CO. OR TO A SUCCESSOR THEREOF
         OR SUCH SUCCESSOR'S NOMINEE AND TRANSFERS OF PORTIONS OF THIS GLOBAL
         NOTE  SHALL BE LIMITED TO TRANSFERS MADE IN ACCORDANCE WITH THE
         PROVISIONS OF SECTION 2.06 OF THE INDENTURE.

                 SECTION 2.02.  Execution, Authentication and Denominations.
Subject to Article Four, the aggregate principal amount of Notes which may be
authenticated and delivered under this Indenture is unlimited.  The Notes shall
be executed by two Officers of the Company.
<PAGE>   28
                                       22

The signature of any of these Officers on the Notes may be by facsimile or
manual signature in the name and on behalf of the Company.

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

                 A Note shall not be valid until the Trustee or authenticating
agent manually signs the certificate of authentication on the Note.  The
signature shall be conclusive evidence that the Note has been authenticated
under this Indenture.

                 At any time and from time to time after the execution of this
Indenture, the Trustee or an authenticating agent shall upon receipt of a
Company Order authenticate for original issue Notes in the aggregate principal
amount specified in such Company Order; provided that the Trustee shall be
entitled to receive an Officers' Certificate and an Opinion of Counsel of the
Company in connection with such authentication of Notes.  Such Company Order
shall specify the amount of Notes to be authenticated and the date on which the
original issue of Notes is to be authenticated and in case of an issuance of
Notes pursuant to Section 2.13, shall certify that such issuance is in
compliance with Article Four.

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

                 The Notes shall be issuable only in registered form without
coupons and only in denominations of $1,000 in principal amount and any
integral multiple of $1,000 in excess thereof.

                 SECTION 2.03.  Registrar and Paying Agent.  The Company shall
maintain an office or agency where Notes may be presented for registration of
transfer or for exchange (the "Registrar"), an office or agency where Notes may
be presented for payment (the "Paying Agent") and an office or agency where
notices and demands to or upon the Company in respect of the Notes and this
Indenture may be served, which shall be in the Borough of Manhattan, The City
of New York.  The Company shall cause the Registrar to keep a register of the
Notes and of their transfer and exchange (the "Security Register").  The
Company may have one or more co-Registrars and one or more additional Paying
Agents.

                 The Company shall enter into an appropriate agency agreement
with any Agent not a party to this Indenture.  The agreement shall implement
the provisions of this Indenture that relate to such Agent.  The Company shall
give prompt written notice to the Trustee of the name and address of any such
Agent and any change in the address of such Agent.  If the Company
<PAGE>   29
                                       23

fails to maintain a Registrar, Paying Agent and/or agent for service of notices
and demands, the Trustee shall act as such Registrar, Paying Agent and/or agent
for service of notices and demands.  The Company may remove any Agent upon
written notice to such Agent and the Trustee; provided that no such removal
shall become effective until (i) the acceptance of an appointment by a
successor Agent to such Agent as evidenced by an appropriate agency agreement
entered into by the Company and such successor Agent and delivered to the
Trustee or (ii) notification to the Trustee that the Trustee shall serve as
such Agent until the appointment of a successor Agent in accordance with clause
(i) of this proviso.  The Company, any Subsidiary of the Company, or any
Affiliate of any of them may act as Paying Agent, Registrar or co-Registrar,
and/or agent for service of notice and demands.

                 The Company initially appoints the Trustee as Registrar,
Paying Agent, authenticating agent and agent for service of notice and demands.
If, at any time, the Trustee is not the Registrar, the Registrar shall make
available to the Trustee on or before each Interest Payment Date and at such
other times as the Trustee may reasonably request, the names and addresses of
the Holders as they appear in the Security Register.

                 SECTION 2.04.  Paying Agent to Hold Money in Trust.  Not later
than each due date of the principal, premium, if any, and interest on any
Notes, the Company shall deposit with the Paying Agent money in immediately
available funds sufficient to pay such principal, premium, if any, and interest
so becoming due.  The Company shall require each Paying Agent other than the
Trustee to agree in writing that such Paying Agent shall hold in trust for the
benefit of the Holders or the Trustee all money held by the Paying Agent for
the payment of principal of, premium, if any, and interest on the Notes
(whether such money has been paid to it by the Company or any other obligor on
the Notes), and such Paying Agent shall promptly notify the Trustee of any
default by the Company (or any other obligor on the Notes) in making any such
payment.  The Company at any time may require a Paying Agent to pay all money
held by it to the Trustee and account for any funds disbursed, and the Trustee
may at any time during the continuance of any payment default, upon written
request to a Paying Agent, require such Paying Agent to pay all money held by
it to the Trustee and to account for any funds disbursed.  Upon doing so, the
Paying Agent shall have no further liability for the money so paid over to the
Trustee.  If the Company or any Subsidiary of the Company or any Affiliate of
any of them acts as Paying Agent, it will, on or before each due date of any
principal of, premium, if any, or interest on the Notes, segregate and hold in
a separate trust fund for the benefit of the Holders a sum of money sufficient
to pay such principal, premium, if any, or interest so becoming due until such
sum of money shall be paid to such Holders or otherwise disposed of as provided
in this Indenture, and will promptly notify the Trustee of its action or
failure to act.

                 SECTION 2.05.  Transfer and Exchange.  A Holder may transfer a
Note only by written application to the Registrar stating the name of the
proposed transferee and otherwise complying with the terms of this Indenture.
No such transfer shall be effected until, and such transferee shall succeed to
the rights of a Holder only upon, final acceptance and registration of
<PAGE>   30
                                       24

the transfer by the Registrar in the Security Register.  Prior to the
registration of any transfer by a Holder as provided herein, the Company, the
Trustee, and any agent of the Company shall treat the person in whose name the
Note is registered as the owner thereof for all purposes whether or not the
Note shall be overdue, and neither the Company, the Trustee, nor any such agent
shall be affected by notice to the contrary.  Furthermore, any Holder of a
Global Note shall, by acceptance of such Global Note, agree that transfers of
beneficial interests in such Global Note may be effected only through a book
entry system maintained by the Holder of such Global Note (or its agent) and
that ownership of a beneficial interest in the Note shall be required to be
reflected in a book entry.  When Notes are presented to the Registrar or a
co-Registrar with a request to register the transfer or to exchange them for an
equal principal amount of Notes of other authorized denominations, the
Registrar shall register the transfer or make the exchange as requested if its
requirements for such transactions are met.  To permit registrations of
transfers and exchanges, the Company shall execute and the Trustee shall
authenticate Notes at the Registrar's request.  No service charge shall be made
for any registration of transfer or exchange or redemption of the Notes, but
the Company may require payment of a sum sufficient to cover any transfer tax
or similar governmental charge payable in connection therewith (other than any
such transfer taxes or other similar governmental charge payable upon exchanges
pursuant to Section 2.09, 3.08 or 9.04).

                 The Registrar shall not be required (i) to issue, register the
transfer of or exchange any Note during a period beginning at the opening of
business 15 days before the day of the mailing of a notice of redemption of
Notes selected for redemption under Section 3.03 and ending at the close of
business on the day of such mailing, or (ii) to register the transfer of or
exchange any Note so selected for redemption in whole or in part, except the
unredeemed portion of any Note being redeemed in part.

                 SECTION 2.06.  Book-Entry Provisions for Global Notes.  (a)
The Global Notes shall (i) be registered in the name of the Depositary for such
Global Notes or the nominee of such Depositary and (ii) be delivered to the
Trustee as custodian for such Depositary.

                 Members of, or participants in, the Depositary ("Agent
Members") shall have no rights under this Indenture with respect to any Global
Note held on their behalf by the Depositary, or the Trustee as its custodian,
or under the Global Note, and the Depositary may be treated by the Company, the
Trustee and any agent of the Company or the Trustee as the absolute owner of
such Global Note for all purposes whatsoever. Notwithstanding the foregoing,
nothing herein shall prevent the Company, the Trustee or any agent of the
Company or the Trustee, from giving effect to any written certification, proxy
or other authorization furnished by the Depositary or impair, as between the
Depositary and its Agent Members, the operation of customary practices
governing the exercise of the rights of a holder of any Note.

                 (b)      Transfers of a Global Note shall be limited to
transfers of such Global Note in whole, but not in part, to the Depositary, its
successors or their respective nominees.
<PAGE>   31
                                       25

Interests of beneficial owners in a Global Note may be transferred in
accordance with the rules and procedures of the Depositary.  Permanent
certificated Notes in registered form in substantially the form set forth in
Exhibit A ("Physical Notes") shall be transferred to all beneficial owners in
exchange for their beneficial interests in the Global Notes (i) if the
Depositary notifies the Company that it is unwilling or unable to continue as
Depositary for the Global Notes and a successor depositary is not appointed by
the Company within 90 days of such notice, (ii) if an Event of Default has
occurred and is continuing and the Registrar has received a request therefor
from the Depositary or (iii) in accordance with the rules and procedures of the
Depositary.  In addition, the Company may at any time and in its sole
discretion determine that the Notes shall no longer be represented by Global
Notes.

                 (c)      In connection with any transfer of a portion of the
beneficial interests in the Global Notes to beneficial owners pursuant to
paragraph (b) of this Section 2.06, the Registrar shall reflect on its books
and records the date and a decrease in the principal amount of the Global Notes
in an amount equal to the principal amount of the beneficial interest in the
Global Notes to be exchanged for Physical Notes, and the Company shall execute,
and the Trustee shall authenticate and deliver, one or more Physical Notes of
like tenor and amount.

                 (d)      In connection with the transfer of all Notes
represented by Global Notes to beneficial owners pursuant to paragraph (b) of
this Section 2.06, the Global Notes shall be deemed to be surrendered to the
Trustee for cancellation, and the Company shall execute, and the Trustee shall
authenticate and deliver, to each beneficial owner identified by the Depositary
in exchange for its beneficial interest in the Global Notes an equal aggregate
principal amount of Physical Notes of authorized denominations.

                 (e)      The registered holder of a Global Note may grant
proxies and otherwise authorize any person, including Agent Members and persons
that may hold interests through Agent Members, to take any action which a
Holder is entitled to take under this Indenture or the Notes.

                 SECTION 2.07.  Replacement Notes.  If a mutilated Note is
surrendered to the Trustee or if the Holder claims that the Note has been lost,
destroyed or wrongfully taken, the Company shall issue and the Trustee shall
authenticate a replacement Note of like tenor and amount and bearing a number
not contemporaneously outstanding; provided that the requirements of this
Section 2.07 are met.  If required by the Trustee or the Company, an indemnity
bond must be furnished that is sufficient in the judgment of both the Trustee
and the Company to protect the Company, the Trustee or any Agent from any loss
that any of them may suffer if a Note is replaced.  The Company may charge such
Holder for its expenses and the expenses of the Trustee in replacing a Note.
In case any such mutilated, lost, destroyed or wrongfully taken Note has become
or is about to become due and payable, the Company in its discretion may pay
such Note instead of issuing a new Note in replacement thereof.
<PAGE>   32
                                       26

                 Every replacement Note is an additional obligation of the
Company and shall be entitled to the benefits of this Indenture.

                 SECTION 2.08.  Outstanding Notes.  Notes outstanding at any
time are all Notes that have been authenticated by the Trustee except for those
cancelled by it, those delivered to it for cancellation and those described in
this Section 2.08 as not outstanding.

                 If a Note is replaced pursuant to Section 2.07, it ceases to
be outstanding unless and until the Trustee and the Company receive proof
satisfactory to them that the replaced Note is held by a bona fide purchaser.

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

                 A Note does not cease to be outstanding because the Company or
one of its Affiliates holds such Note, provided, however, that, in determining
whether the Holders of the requisite principal amount of the outstanding Notes
have given any request, demand, authorization, direction, notice, consent or
waiver hereunder, Notes owned by the Company or any other obligor upon the
Notes 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 or waiver, only Notes which a
Responsible Officer of the Trustee actually knows to be so owned shall be so
disregarded.  Notes 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 Notes and that the
pledgee is not the Company or any other obligor upon the Notes or any Affiliate
of the Company or of such other obligor.

                 SECTION 2.09.  Temporary Notes.  Until definitive Notes are
ready for delivery, the Company may prepare and the Trustee shall authenticate
temporary Notes.  Temporary Notes shall be substantially in the form of
definitive Notes but may have insertions, substitutions, omissions and other
variations determined to be appropriate by the Officers executing the temporary
Notes, as evidenced by their execution of such temporary Notes.  If temporary
Notes are issued, the Company will cause definitive Notes to be prepared
without unreasonable delay.  After the preparation of definitive Notes, the
temporary Notes shall be exchangeable for definitive Notes upon surrender of
the temporary Notes at the office or agency of the Company designated for such
purpose pursuant to Section 4.02, without charge to the Holder.  Upon surrender
for cancellation of any one or more temporary Notes the Company shall execute
and the Trustee shall authenticate and make available for delivery in exchange
therefor a like principal amount of definitive Notes of authorized
denominations.  Until so exchanged, the temporary Notes shall be entitled to
the same benefits under this Indenture as definitive Notes.
<PAGE>   33
                                       27

                 SECTION 2.10.  Cancellation.  The Company at any time may
deliver to the Trustee for cancellation any Notes previously authenticated and
delivered hereunder which the Company may have acquired in any manner
whatsoever, and may deliver to the Trustee for cancellation any Notes
previously authenticated hereunder which the Company has not issued and sold.
The Registrar and the Paying Agent shall forward to the Trustee any Notes
surrendered to them for transfer, exchange or payment.  The Trustee shall
cancel all Notes surrendered for transfer, exchange, payment or cancellation in
accordance with its normal procedure.

                 SECTION 2.11.  CUSIP Numbers.  The Company in issuing the
Notes may use "CUSIP," "CINS" or "ISIN" numbers (if then generally in use), and
the Trustee shall use CUSIP, CINS or ISIN numbers, as the case may be, in
notices of redemption or exchange as a convenience to Holders; provided that
any such notice shall state that no representation is made as to the
correctness of such numbers either as printed on the Notes or as contained in
any notice of redemption or exchange and that reliance may be placed only on
the other identification numbers printed on the Notes, and any such redemption
shall not be affected by any defect or omission of such numbers.  The Company
will promptly notify the Trustee of any change in the "CUSIP," "CINS" or "ISIN"
numbers.

                 SECTION 2.12.  Defaulted Interest.  If the Company defaults in
a payment of interest on the Notes, it shall pay, or shall deposit with the
Paying Agent money in immediately available funds sufficient to pay the
defaulted interest, plus (to the extent lawful) any interest payable on the
defaulted interest, to the Persons who are Holders on a subsequent special
record date.  A special record date, as used in this Section 2.12 with respect
to the payment of any defaulted interest, shall mean the 15th day next
preceding the date fixed by the Company for the payment of defaulted interest,
whether or not such day is a Business Day.  At least 15 days before the
subsequent special record date, the Company shall mail to each Holder and to a
Responsible Officer of the Trustee a notice that states the subsequent special
record date, the payment date and the amount of defaulted interest to be paid.

                 SECTION 2.13.  Issuance of Additional Notes.  The Company may,
subject to Article Four of this Indenture, issue additional Notes under this
Indenture.  The Notes issued on the Closing Date and any additional Notes
subsequently issued shall be treated as a single class for all purposes under
this Indenture.


                                 ARTICLE THREE
                                   REDEMPTION

                 SECTION 3.01.  Right of Redemption.  (a)  The Notes may be
redeemed, at the Company's option, in whole or in part, at any time or from
time to time, on or after May 15, 2003 and prior to maturity, upon not less
than 30 nor more than 60 days' prior notice mailed by first class mail to each
Holder's last address as it appears in the Security Register, at
<PAGE>   34
                                       28

the Redemption Prices (expressed in percentages of principal amount) set forth
below, plus accrued and unpaid interest to the Redemption Date (subject to the
right of Holders of record on the relevant Regular Record Date that is on or
prior to the Redemption Date to receive interest due on an Interest Payment
Date), if redeemed during the 12-month period commencing May 15 of the years
set forth below:

<TABLE>
<CAPTION>
                                                               Redemption
                          Year                                   Price    
                          ----                                 ----------
                          <S>                                  <C>   
                          2003                                 [     ]%
                          2004                                 [     ]%
                          2005                                 [     ]%
                          2006 and thereafter                  100.000%
</TABLE>

                 (b)      In addition, at any time prior to May 15, 2001, the
Company may redeem up to 35% of the principal amount of the Notes originally
issued with the proceeds of one or more Public Equity Offerings following which
there is a Public Market, at any time or from time to time in part, at a
Redemption Price (expressed as a percentage principal amount) of [
]% plus accrued and unpaid interest to the Redemption Date (subject to the
right of Holders of record on the relevant Regular Record Date that is on or
prior to the Redemption Date to receive interest due on an Interest Payment
Date); provided that at least 65% of the aggregate principal amount of Notes
originally issued remains outstanding after each such redemption and notice of
any such redemption is mailed within 60 days after the related Public Equity
Offering.

                 SECTION 3.02.  Notices to Trustee.  If the Company elects to
redeem Notes pursuant to Section 3.01(a) or 3.01(b), it shall notify the
Trustee in writing of the Redemption Date and the principal amount of Notes to
be redeemed.

                 The Company shall give each notice provided for in this
Section 3.02 in an Officers' Certificate at least 45 days before the Redemption
Date (unless a shorter period shall be satisfactory to the Trustee).

                 SECTION 3.03.  Selection of Notes to Be Redeemed.  If less
than all of the Notes are to be redeemed at any time, the Trustee shall select
the Notes to be redeemed in compliance with the requirements, as certified to
it by the Company, of the principal national securities exchange, if any, on
which the Notes are listed or, if the Notes are not listed on a national
securities exchange, by lot or by such other method as the Trustee in its sole
discretion shall deem fair and appropriate; provided that no Notes of $1,000 in
principal amount or less shall be redeemed in part.

                 The Trustee shall make the selection from the Notes
outstanding and not previously called for redemption.  Notes in denominations
of $1,000 in principal amount may only be redeemed in whole.  The Trustee may
select for redemption portions (equal to $1,000 in
<PAGE>   35
                                       29

principal amount or any integral multiple thereof) of Notes that have
denominations larger than $1,000 in principal amount.  Provisions of this
Indenture that apply to Notes called for redemption also apply to portions of
Notes called for redemption.  The Trustee shall notify the Company and the
Registrar promptly in writing of the Notes or portions of Notes to be called
for redemption.

                 SECTION 3.04.  Notice of Redemption.  With respect to any
redemption of Notes pursuant to Section 3.01(a) or 3.01(b), at least 30 days
but not more than 60 days before a Redemption Date, the Company shall mail a
notice of redemption by first class mail to each Holder whose Notes are to be
redeemed.

                 The notice shall identify the Notes (including CUSIP, CINS or
ISIN numbers) to be redeemed and shall state:

                 (i)      the Redemption Date;

                 (ii)     the Redemption Price;

                 (iii)    the name and address of the Paying Agent;

                 (iv)     that Notes called for redemption must be surrendered
         to the Paying Agent in order to collect the Redemption Price;

                 (v)      that, unless the Company defaults in making the
         redemption payment, interest on Notes called for redemption ceases to
         accrue on and after the Redemption Date and the only remaining right
         of the Holders is to receive payment of the Redemption Price plus
         accrued interest to the Redemption Date upon surrender of the Notes to
         the Paying Agent;

                 (vi)     that, if any Note is being redeemed in part, the
         portion of the principal amount (equal to $1,000 in principal amount
         or any integral multiple thereof) of such Note to be redeemed and
         that, on and after the Redemption Date, upon surrender of such Note, a
         new Note or Notes in principal amount equal to the unredeemed portion
         thereof will be reissued; and

                 (vii)    that, if any Note contains a CUSIP, CINS or ISIN
         number as provided in Section 2.11, no representation is being made as
         to the correctness of the CUSIP, CINS or ISIN number either as printed
         on the Notes or as contained in the notice of redemption and that
         reliance may be placed only on the other identification numbers
         printed on the Notes.
<PAGE>   36
                                       30

                 At the Company's request (which request may be revoked by the
Company at any time prior to the time at which the Trustee shall have given
such notice to the Holders), made in writing to the Trustee at least 30 days
(or such shorter period as shall be satisfactory to the Trustee) before a
Redemption Date, the Trustee shall give the notice of redemption in the name
and at the expense of the Company.  If, however, the Company gives such notice
to the Holders, the Company shall concurrently deliver to the Trustee an
Officers' Certificate stating that such notice has been given.

                 SECTION 3.05.  Effect of Notice of Redemption.  Once notice of
redemption is mailed, Notes called for redemption become due and payable on the
Redemption Date and at the Redemption Price.  Upon surrender of any Notes to
the Paying Agent, such Notes shall be paid at the Redemption Price, plus
accrued interest, if any, to the Redemption Date.

                 Notice of redemption shall be deemed to be given when mailed,
whether or not the Holder receives the notice.  In any event, failure to give
such notice, or any defect therein, shall not affect the validity of the
proceedings for the redemption of Notes held by Holders to whom such notice was
properly given.

                 SECTION 3.06.  Deposit of Redemption Price.  On or prior to
any Redemption Date, the Company shall deposit with the Paying Agent (or, if
the Company is acting as its own Paying Agent, shall segregate and hold in
trust as provided in Section 2.04) money sufficient to pay the Redemption Price
of and accrued interest on all Notes to be redeemed on that date other than
Notes or portions thereof called for redemption on that date that have been
delivered by the Company to the Trustee for cancellation.

                 SECTION 3.07.  Payment of Notes Called for Redemption.  If
notice of redemption has been given in the manner provided above, the Notes or
portion of Notes specified in such notice to be redeemed shall become due and
payable on the Redemption Date at the Redemption Price stated therein, together
with accrued interest to such Redemption Date, and on and after such date
(unless the Company shall default in the payment of such Notes at the
Redemption Price and accrued interest to the Redemption Date, in which case the
principal, until paid, shall bear interest from the Redemption Date at the rate
prescribed in the Notes), such Notes shall cease to accrue interest.  Upon
surrender of any Note for redemption in accordance with a notice of redemption,
such Note shall be paid and redeemed by the Company at the Redemption Price,
together with accrued interest, if any, to the Redemption Date; provided that
installments of interest whose Stated Maturity is on or prior to the Redemption
Date shall be payable to the Holders registered as such at the close of
business on the relevant Regular Record Date.

                 SECTION 3.08.  Notes Redeemed in Part.  Upon surrender of any
Note that is redeemed in part, the Company shall execute and the Trustee shall
authenticate and deliver to the
<PAGE>   37
                                       31

Holder a new Note equal in principal amount to the unredeemed portion of such
surrendered Note.


                                  ARTICLE FOUR
                                   COVENANTS

                 SECTION 4.01.  Payment of Notes.  The Company shall pay the
principal of, premium, if any, and interest on the Notes on the dates and in
the manner provided in the Notes and this Indenture.  An installment of
principal, premium, if any, or interest shall be considered paid on the date
due if the Trustee or Paying Agent (other than the Company, a Subsidiary of the
Company, or any Affiliate of any of them) holds on that date money designated
for and sufficient to pay the installment.  If the Company or any Subsidiary of
the Company or any Affiliate of any of them, acts as Paying Agent, an
installment of principal, premium, if any, or interest shall be considered paid
on the due date if the entity acting as Paying Agent complies with the last
sentence of Section 2.04.  As provided in Section 6.09, upon any bankruptcy or
reorganization procedure relative to the Company, the Trustee shall serve as
the Paying Agent and conversion agent, if any, for the Notes.

                 The Company shall pay interest on overdue principal, premium,
if any, and interest on overdue installments of interest, to the extent lawful,
at the rate per annum specified in the Notes.

                 SECTION 4.02.  Maintenance of Office or Agency.  The Company
will maintain in the Borough of Manhattan, The City of New York an office or
agency where Notes may be surrendered for registration of transfer or exchange
or for presentation for payment and where notices and demands to or upon the
Company in respect of the Notes 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 address of the Trustee set forth in
Section 11.02.

                 The Company may also from time to time designate one or more
other offices or agencies where the Notes may be presented or surrendered for
any or all such purposes and may from time to time rescind such designations;
provided that no such designation or rescission shall in any manner relieve the
Company of its obligation to maintain an office or agency in the Borough of
Manhattan, The City of New York 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.
<PAGE>   38
                                       32

                 The Company hereby initially designates the Corporate Trust
Office of the Trustee, located in the Borough of Manhattan, The City of New
York, as such office of the Company in accordance with Section 2.03.

                 SECTION 4.03.  Limitation on Indebtedness.  (a)  The Company
will not, and will not permit any of its Restricted Subsidiaries to, Incur any
Indebtedness (other than the Notes and Indebtedness existing on the Closing
Date); provided that the Company may Incur Indebtedness if, after giving effect
to the Incurrence of such Indebtedness and the receipt and application of the
proceeds therefrom, the Consolidated Leverage Ratio would be greater than zero
and less than 6:1.

                 Notwithstanding the foregoing, the Company and any Restricted
Subsidiary (except as specified below) may Incur each and all of the following:

                 (i)      Indebtedness outstanding at any time in an aggregate
         principal amount not to exceed $100 million, less any amount of such
         Indebtedness permanently repaid as provided under Section 4.10;

                 (ii)     Indebtedness owed (A) to the Company evidenced by a
         promissory note or (B) to any Restricted Subsidiary; provided that any
         event which results in any such Restricted Subsidiary ceasing to be a
         Restricted Subsidiary or any subsequent transfer of such Indebtedness
         (other than to the Company or another Restricted Subsidiary) shall be
         deemed, in each case, to constitute an Incurrence of such Indebtedness
         not permitted by this clause (ii);

                 (iii)    Indebtedness issued in exchange for, or the net
         proceeds of which are used to refinance or refund, then outstanding
         Indebtedness (other than Indebtedness Incurred under clause (i), (ii),
         (iv), (vi), (viii) or (ix) of this paragraph of this Section 4.03) and
         any refinancings thereof in an amount not to exceed the amount so
         refinanced or refunded (plus premiums, accrued interest, fees and
         expenses); provided that Indebtedness the proceeds of which are used
         to refinance or refund the Notes or Indebtedness that is pari passu
         with, or subordinated in right of payment to, the Notes shall only be
         permitted under this clause (iii) if (A) in case the Notes are
         refinanced in part or the Indebtedness to be refinanced is pari passu
         with the Notes, such new Indebtedness, by its terms or by the terms of
         any agreement or instrument pursuant to which such new Indebtedness is
         outstanding, is expressly made pari passu with, or subordinate in
         right of payment to, the remaining Notes, (B) in case the Indebtedness
         to be refinanced is subordinated in right of payment to the Notes,
         such new Indebtedness, by its terms or by the terms of any agreement
         or instrument pursuant to which such new Indebtedness is issued or
         remains outstanding, is expressly made subordinate in right of payment
         to the Notes at least to the extent that the Indebtedness to be
         refinanced is subordinated to the Notes and (C) such new Indebtedness,
         determined as of the date of Incurrence of such new Indebtedness,
<PAGE>   39
                                       33

         does not mature prior to the Stated Maturity of the Indebtedness to be
         refinanced or refunded, and the Average Life of such new Indebtedness
         is at least equal to the remaining Average Life of the Indebtedness to
         be refinanced or refunded; and provided further that in no event may
         Indebtedness of the Company be refinanced by means of any Indebtedness
         of any Restricted Subsidiary pursuant to this clause (iii);

                 (iv)     Indebtedness (A) in respect of performance, surety or
         appeal bonds provided in the ordinary course of business, (B) under
         Currency Agreements and Interest Rate Agreements; provided that such
         agreements (a) are designed solely to protect the Company or its
         Restricted Subsidiaries against fluctuations in foreign currency
         exchange rates or interest rates and (b) do not increase the
         Indebtedness of the obligor outstanding at any time other than as a
         result of fluctuations in foreign currency exchange rates or interest
         rates or by reason of fees, indemnities and compensation payable
         thereunder; and (C) arising from agreements providing for
         indemnification, adjustment of purchase price or similar obligations,
         or from Guarantees or letters of credit, surety bonds or performance
         bonds securing any obligations of the Company or any of its Restricted
         Subsidiaries pursuant to such agreements, in any case Incurred in
         connection with the disposition of any business, assets or Restricted
         Subsidiary (other than Guarantees of Indebtedness Incurred by any
         Person acquiring all or any portion of such business, assets or
         Restricted Subsidiary for the purpose of financing such acquisition),
         in a principal amount not to exceed the gross proceeds actually
         received by the Company or any Restricted Subsidiary in connection
         with such disposition;

                 (v)      Indebtedness of the Company, to the extent the net
         proceeds thereof are promptly (A) used to purchase Notes tendered in
         an Offer to Purchase made as a result of a Change in Control or (B)
         deposited to defease the Notes as set forth in Article Eight;

                 (vi)     Guarantees of the Notes and Guarantees of
         Indebtedness of the Company by any Restricted Subsidiary provided the
         Guarantee of such Indebtedness is permitted by and made in accordance
         with Section 4.07;

                 (vii)    Indebtedness (including Guarantees) Incurred to
         finance the cost (including the cost of design, development,
         acquisition, construction, installation, improvement, transportation
         or integration) to acquire equipment, inventory or network assets
         (including acquisitions by way of Capitalized Lease and acquisitions
         of the Capital Stock of a Person that becomes a Restricted Subsidiary
         to the extent of the fair market value of the equipment, inventory or
         network assets so acquired) by the Company or a Restricted Subsidiary
         after the Closing Date;

                 (viii)   Indebtedness of the Company not to exceed, at any one
         time outstanding, two times (A) the Net Cash Proceeds received by the
         Company after February 3, 1998 as a capital contribution or from the
         issuance and sale of its Capital Stock (other than
<PAGE>   40
                                       34

         Disqualified Stock) to a Person that is not a Subsidiary of the
         Company, to the extent (I) such capital contribution or Net Cash
         Proceeds have not been used pursuant to clause (C)(2) of the first
         paragraph or clause (iii), (iv), (vi), (vii) or (viii) of the second
         paragraph of Section 4.04 to make a Restricted Payment and (II) if
         such capital contribution or Net Cash Proceeds are used to consummate
         a transaction pursuant to which the Company Incurs Acquired
         Indebtedness, the amount of such Net Cash Proceeds exceeds one-half of
         the amount of Acquired Indebtedness so Incurred and (B) 80% of the
         fair market value of property (other than cash and cash equivalents)
         received by the Company after February 3, 1998 from the sale of its
         Capital Stock (other than Disqualified Stock) to a Person that is not
         a Subsidiary of the Company, to the extent (I) such capital
         contribution or sale of Capital Stock has not been used pursuant to
         clause (iii), (iv), (vi) or (vii) of the second paragraph of Section
         4.04 to make a Restricted Payment and (II) if such capital
         contribution or Capital Stock is used to consummate a transaction
         pursuant to which the Company Incurs Acquired Indebtedness, 80% of the
         fair market value of the property received exceeds one-half of the
         amount of Acquired Indebtedness so Incurred provided that such
         Indebtedness does not mature prior to the Stated Maturity of the Notes
         and has an Average Life longer than the Notes;

                 (ix)     Acquired Indebtedness;

                 (x)      Strategic Subordinated Indebtedness; and

                 (xi)     subordinated Indebtedness of the Company (in addition
         to Indebtedness permitted under clauses (i) through (x) above) in an
         aggregate principal amount outstanding at any time not to exceed $100
         million, less any amount of such Indebtedness permanently repaid as
         provided under Section 4.10.

                 (b)      Notwithstanding any other provision of this Section
4.03, the maximum amount of Indebtedness that the Company or a Restricted
Subsidiary may Incur pursuant to this Section 4.03 shall not be deemed to be
exceeded, with respect to any outstanding Indebtedness due solely to the result
of fluctuations in the exchange rates of currencies.

                 (c)      For purposes of determining any particular amount of
Indebtedness under this Section 4.03, (1) Guarantees, Liens or obligations with
respect to letters of credit supporting Indebtedness otherwise included in the
determination of such particular amount shall not be included and (2) any Liens
granted pursuant to the equal and ratable provisions referred to in Section
4.09 shall not be treated as Indebtedness. For purposes of determining
compliance with this Section 4.03, in the event that an item of Indebtedness
meets the criteria of more than one of the types of Indebtedness described in
the above clauses, the Company, in its sole discretion, shall classify, and
from time to time may reclassify, such item of Indebtedness and only be
required to include the amount and type of such Indebtedness in one of such
clauses.
<PAGE>   41
                                       35

                 SECTION 4.04.  Limitation on Restricted Payments.  The Company
will not, and will not permit any Restricted Subsidiary to, directly or
indirectly, (i) declare or pay any dividend or make any distribution on or with
respect to its Capital Stock (other than (x) dividends or distributions payable
solely in shares of its Capital Stock (other than Disqualified Stock) or in
options, warrants or other rights to acquire shares of such Capital Stock and
(y) pro rata dividends or distributions on Common Stock of Restricted
Subsidiaries held by minority stockholders) held by Persons other than the
Company or any of its Restricted Subsidiaries, (ii) purchase, redeem, retire or
otherwise acquire for value any shares of Capital Stock of (A) the Company or
an Unrestricted Subsidiary (including options, warrants or other rights to
acquire such shares of Capital Stock) held by any Person or (B) a Restricted
Subsidiary (including options, warrants or other rights to acquire such shares
of Capital Stock) held by any Affiliate of the Company (other than a Wholly
Owned Restricted Subsidiary) or any holder (or any Affiliate of such holder) of
5% or more of the Capital Stock of the Company, (iii) make any voluntary or
optional principal payment, or voluntary or optional redemption, repurchase,
defeasance, or other acquisition or retirement for value, of Indebtedness of
the Company that is subordinated in right of payment to the Notes or (iv) make
any Investment, other than a Permitted Investment, in any Person (such payments
or any other actions described in clauses (i) through (iv) above being
collectively "Restricted Payments") if, at the time of, and after giving effect
to, the proposed Restricted Payment: (A) a Default or Event of Default shall
have occurred and be continuing, (B) the Company could not Incur at least $1.00
of Indebtedness under the first paragraph of Section 4.03 or (C) the aggregate
amount of all Restricted Payments (the amount, if other than in cash, to be
determined in good faith by the Board of Directors, whose determination shall
be conclusive and evidenced by a Board Resolution) made after the Closing Date
shall exceed the sum of (1) 50% of the aggregate amount of the Adjusted
Consolidated Net Income (or, if the Adjusted Consolidated Net Income is a loss,
minus 100% of the amount of such loss) (determined by excluding income
resulting from transfers of assets by the Company or a Restricted Subsidiary to
an Unrestricted Subsidiary) accrued on a cumulative basis during the period
(taken as one accounting period) beginning on April 1, 1998 and ending on the
last day of the last fiscal quarter preceding the Transaction Date for which
reports have been filed with the Commission or provided to the Trustee pursuant
to Section 4.17 plus (2) the aggregate Net Cash Proceeds received by the
Company after February 3, 1998 as a capital contribution or from the issuance
and sale permitted by this Indenture of its Capital Stock (other than
Disqualified Stock) to a Person who is not a Subsidiary of the Company,
including an issuance or sale permitted by this Indenture of Indebtedness of
the Company for cash subsequent to February 3, 1998 upon the conversion of such
Indebtedness into Capital Stock (other than Disqualified Stock) of the Company,
or from the issuance to a Person who is not a Subsidiary of the Company of any
options, warrants or other rights to acquire Capital Stock of the Company (in
each case, exclusive of any Disqualified Stock or any options, warrants or
other rights that are redeemable at the option of the holder, or are required
to be redeemed, prior to the Stated Maturity of the Notes), in each case except
to the extent such Net Cash Proceeds are used to Incur Indebtedness pursuant to
clause (viii) of the second paragraph under Section 4.03, plus (3) an amount
equal to the net reduction in Investments (other than reductions in Permitted
Investments) in any Person resulting
<PAGE>   42
                                       36

from payments of interest on Indebtedness, dividends, repayments of loans or
advances, or other transfers of assets, in each case to the Company or any
Restricted Subsidiary or from the Net Cash Proceeds from the sale of any such
Investment (except, in each case, to the extent any such payment or proceeds
are included in the calculation of Adjusted Consolidated Net Income), or from
redesignations of Unrestricted Subsidiaries as Restricted Subsidiaries (valued
in each case as provided in the definition of "Investments"), not to exceed, in
each case, the amount of Investments previously made by the Company or any
Restricted Subsidiary in such Person or Unrestricted Subsidiary.

                 The foregoing provision shall not be violated by reason of:

                 (i)      the payment of any dividend within 60 days after the
         date of declaration thereof if, at said date of declaration, such
         payment would comply with the foregoing paragraph;

                 (ii)     the redemption, repurchase, defeasance or other
         acquisition or retirement for value of Indebtedness that is
         subordinated in right of payment to the Notes including premium, if
         any, and accrued and unpaid interest, with the proceeds of, or in
         exchange for, Indebtedness Incurred under clause (iii) of the second
         paragraph of Section 4.03(a);

                 (iii)    the repurchase, redemption or other acquisition of
         Capital Stock of the Company or an Unrestricted Subsidiary (or
         options, warrants or other rights to acquire such Capital Stock) in
         exchange for, or out of the proceeds of a capital contribution or a
         substantially concurrent offering of, shares of Capital Stock (other
         than Disqualified Stock) of the Company (or options, warrants or other
         rights to acquire such Capital Stock);

                 (iv)     the making of any principal payment or the
         repurchase, redemption, retirement, defeasance or other acquisition
         for value of Indebtedness of the Company which is subordinated in
         right of payment to the Notes in exchange for, or out of the proceeds
         of a capital contribution or a substantially concurrent offering of,
         shares of the Capital Stock (other than Disqualified Stock) of the
         Company (or options, warrants or other rights to acquire such Capital
         Stock);

                 (v)      payments or distributions, to dissenting stockholders
         pursuant to applicable law, pursuant to or in connection with a
         consolidation, merger or transfer of assets that complies with the
         provisions of Article Five;

                 (vi)     Investments in any Person the primary business of
         which is related, ancillary or complementary to the business of the
         Company and its Restricted Subsidiaries on the date of such
         Investments; provided that the aggregate amount of Investments made
         pursuant to this clause (vi) does not exceed the sum of (a) $20
         million
<PAGE>   43
                                       37

         and (b) the amount of Net Cash Proceeds received by the Company after
         February 3, 1998 as a capital contribution or from the sale of its
         Capital Stock (other than Disqualified Stock) to a Person who is not a
         Subsidiary of the Company, except to the extent such Net Cash Proceeds
         are used to Incur Indebtedness pursuant to clause (viii) of the second
         paragraph of Section 4.03(a) or to make Restricted Payments pursuant
         to clause (C)(2) of the first paragraph, or clauses (iii), (iv) or
         (viii) of this paragraph, of this Section 4.04, plus (z) the net
         reduction in Investments made pursuant to this clause (vi) resulting
         from distributions on or repayments of such Investments or from the
         Net Cash Proceeds from the sale of any such Investment (except in each
         case to the extent any such payment or proceeds is included in the
         calculation of Adjusted Consolidated Net Income) or from such Person
         becoming a Restricted Subsidiary (valued in each case as provided in
         the definition of "Investments"), provided that the net reduction in
         any Investment shall not exceed the amount of such Investment;

                 (vii)    Investments acquired in exchange for Capital Stock
         (other than Disqualified Stock) of the Company;

                 (viii)   the declaration or payment of dividends on Capital
         Stock (other than Disqualified Stock) of the Company in an aggregate
         annual amount not to exceed 6% of the Net Cash Proceeds received by
         the Company from the sale of such Capital Stock after the Closing
         Date;

                 (ix)     repurchases of Warrants pursuant to a Repurchase
         Offer;

                 (x)      any purchase of any fractional shares of Common Stock
         (or other Capital Stock of the Company issuable upon exercise of the
         Warrants) in connection with an exercise of the Warrants; and

                 (xi)     other Restricted Payments in an aggregate amount not
         to exceed $2 million;

provided that, except in the case of clauses (i) and (iii), no Default or Event
of Default shall have occurred and be continuing or occur as a consequence of
the actions or payments set forth therein.

                 Each Restricted Payment permitted pursuant to the preceding
paragraph (other than the Restricted Payment referred to in clause (ii)
thereof, an exchange of Capital Stock for Capital Stock or Indebtedness
referred to in clause (iii) or (iv) thereof and an Investment referred to in
clause (vi) thereof), and the Net Cash Proceeds from any capital contribution
or any issuance of Capital Stock referred to in clauses (iii), (iv) and (vi),
shall be included in calculating whether the conditions of clause (C) of the
first paragraph of this Section 4.04 have been met with respect to any
subsequent Restricted Payments. In the event the proceeds of an issuance of
<PAGE>   44
                                       38

Capital Stock of the Company are used for the redemption, repurchase or other
acquisition of the Notes, or Indebtedness that is pari passu with the Notes,
then the Net Cash Proceeds of such issuance shall be included in clause (C) of
the first paragraph of this Section 4.04 only to the extent such proceeds are
not used for such redemption, repurchase or other acquisition of Indebtedness.

                 SECTION 4.05.  Limitation on Dividend and Other Payment
Restrictions Affecting Restricted Subsidiaries.  The Company will not, and will
not permit any Restricted Subsidiary to, create or otherwise cause or suffer to
exist or become effective any consensual encumbrance or restriction of any kind
on the ability of any Restricted Subsidiary to (i) pay dividends or make any
other distributions permitted by applicable law on any Capital Stock of such
Restricted Subsidiary owned by the Company or any other Restricted Subsidiary,
(ii) pay any Indebtedness owed to the Company or any other Restricted
Subsidiary, (iii) make loans or advances to the Company or any other Restricted
Subsidiary or (iv) transfer any of its property or assets to the Company or any
other Restricted Subsidiary.

                 The foregoing provisions shall not restrict any encumbrances
or restrictions:

                 (i)      existing on the Closing Date in this Indenture or any
         other agreements in effect on the Closing Date, and any extensions,
         refinancings, renewals or replacements of such agreements; provided
         that the encumbrances and restrictions in any such extensions,
         refinancings, renewals or replacements are no less favorable in any
         material respect to the Holders than those encumbrances or
         restrictions that are then in effect and that are being extended,
         refinanced, renewed or replaced;

                 (ii)     existing under or by reason of applicable law;

                 (iii)    existing with respect to any Person or the property
         or assets of such Person acquired by the Company or any Restricted
         Subsidiary, existing at the time of such acquisition and not incurred
         in contemplation thereof, which encumbrances or restrictions are not
         applicable to any Person or the property or assets of any Person other
         than such Person or the property or assets of such Person so acquired;

                 (iv)     in the case of clause (iv) of the first paragraph of
         this Section 4.05, (A) that restrict in a customary manner the
         subletting, assignment or transfer of any property or asset that is a
         lease, license, conveyance or contract or similar property or asset,
         (B) existing by virtue of any transfer of, agreement to transfer,
         option or right with respect to, or Lien on, any property or assets of
         the Company or any Restricted Subsidiary not otherwise prohibited by
         this Indenture or (C) arising or agreed to in the ordinary course of
         business, not relating to any Indebtedness, and that do not,
         individually or in the aggregate, detract from the value of property
         or assets of the Company or any Restricted Subsidiary in any manner
         material to the Company or any Restricted Subsidiary;
<PAGE>   45
                                       39


                 (v)      with respect to a Restricted Subsidiary and imposed
         pursuant to an agreement that has been entered into for the sale or
         disposition of all or substantially all of the Capital Stock of, or
         property and assets of, such Restricted Subsidiary; or

                 (vi)     contained in the terms of any Indebtedness or any
         agreement pursuant to which such Indebtedness was issued if (A) the
         encumbrance or restriction applies only in the event of a payment
         default or a default with respect to a financial covenant contained in
         such Indebtedness or agreement, (B) the encumbrance or restriction is
         not materially more disadvantageous to the Holders of the Notes than
         is customary in comparable financings (as determined by the Company)
         and (C) the Company determines that any such encumbrance or
         restriction will not materially affect the Company's ability to make
         principal or interest payments on the Notes.

Nothing contained in this Section 4.05 shall prevent the Company or any
Restricted Subsidiary from (1) creating, incurring, assuming or suffering to
exist any Liens otherwise permitted in Section 4.09 or (2) restricting the sale
or other disposition of property or assets of the Company or any of its
Restricted Subsidiaries that secure Indebtedness of the Company or any of its
Restricted Subsidiaries.

                 SECTION 4.06.  Limitation on the Issuance and Sale of Capital
Stock of Restricted Subsidiaries.  The Company will not sell, and will not
permit any Restricted Subsidiary, directly or indirectly, to issue or sell, any
shares of Capital Stock of a Restricted Subsidiary (including options, warrants
or other rights to purchase shares of such Capital Stock) except (i) to the
Company or a Wholly Owned Restricted Subsidiary; (ii) issuances of director's
qualifying shares or sales to foreign nationals of shares of Capital Stock of
foreign Restricted Subsidiaries, to the extent required by applicable law;
(iii) if, immediately after giving effect to such issuance or sale, such
Restricted Subsidiary would no longer constitute a Restricted Subsidiary and
any Investment in such Person remaining after giving effect to such issuance or
sale would have been permitted to be made under Section 4.04 if made on the
date of such issuance or sale; or (iv) issuances or sales of Common Stock of a
Restricted Subsidiary, provided that the Company or such Restricted Subsidiary
applies the Net Cash Proceeds, if any, of any such sale in accordance with
clause (A) or (B) of Section 4.10.

                 SECTION 4.07.  Limitation on Issuances of Guarantees by
Restricted Subsidiaries.  The Company will not permit any Restricted
Subsidiary, directly or indirectly, to Guarantee any Indebtedness of the
Company which is pari passu with or subordinate in right of payment to the
Notes ("Guaranteed Indebtedness"), unless (i) such Restricted Subsidiary
simultaneously executes and delivers a supplemental indenture to this Indenture
providing for a Guarantee (a "Subsidiary Guarantee") of payment of the Notes by
such Restricted Subsidiary and (ii) such Restricted Subsidiary waives and will
not in any manner whatsoever claim or take the benefit or advantage of, any
rights of reimbursement, indemnity or subrogation or any other rights against
the Company or any other Restricted Subsidiary as a result of any payment by
such
<PAGE>   46
                                       40

Restricted Subsidiary under its Subsidiary Guarantee; provided that this
paragraph shall not be applicable to any Guarantee of any Restricted Subsidiary
that existed at the time such Person became a Restricted Subsidiary and was not
Incurred in connection with, or in contemplation of, such Person becoming a
Restricted Subsidiary. If the Guaranteed Indebtedness is (A) pari passu with
the Notes, then the Guarantee of such Guaranteed Indebtedness shall be pari
passu with, or subordinated to, the Subsidiary Guarantee or (B) subordinated to
the Notes, then the Guarantee of such Guaranteed Indebtedness shall be
subordinated to the Subsidiary Guarantee at least to the extent that the
Guaranteed Indebtedness is subordinated to the Notes.

                 Notwithstanding the foregoing, any Subsidiary Guarantee by a
Restricted Subsidiary may provide by its terms that it shall be automatically
and unconditionally released and discharged upon (i) any sale, exchange or
transfer, to any Person not an Affiliate of the Company, of all of the
Company's and each Restricted Subsidiary's Capital Stock in, or all or
substantially all the assets of, such Restricted Subsidiary (which sale,
exchange or transfer is not prohibited by this Indenture) or (ii) the release
or discharge of the Guarantee which resulted in the creation of such Subsidiary
Guarantee, except a discharge or release by or as a result of payment under
such Guarantee.

                 SECTION 4.08.  Limitation on Transactions with Shareholders
and Affiliates.  The Company will not, and will not permit any Restricted
Subsidiary to, directly or indirectly, enter into, renew or extend any
transaction (including, without limitation, the purchase, sale, lease or
exchange of property or assets, or the rendering of any service) with any
holder (or any Affiliate of such holder) of 5% or more of any class of Capital
Stock of the Company or with any Affiliate of the Company or any Restricted
Subsidiary, except upon fair and reasonable terms no less favorable to the
Company or such Restricted Subsidiary than could be obtained, at the time of
such transaction or, if such transaction is pursuant to a written agreement, at
the time of the execution of the agreement providing therefor, in a comparable
arm's-length transaction with a Person that is not such a holder or an
Affiliate.

                 The foregoing limitation does not limit, and shall not apply
to:

                 (i)      transactions (A) approved by a majority of the
         disinterested members of the Board of Directors or (B) for which the
         Company or a Restricted Subsidiary delivers to the Trustee a written
         opinion of a nationally recognized investment banking firm stating
         that the transaction is fair to the Company or such Restricted
         Subsidiary from a financial point of view;

                 (ii)     any transaction solely between the Company and any of
         its Wholly Owned Restricted Subsidiaries or solely between Wholly
         Owned Restricted Subsidiaries;

                 (iii)    the payment of reasonable and customary regular fees
         to directors of the Company who are not employees of the Company;
<PAGE>   47
                                       41


                 (iv)     any payments or other transactions pursuant to any
         tax-sharing agreement between the Company and any other Person with
         which the Company files a consolidated tax return or with which the
         Company is part of a consolidated group for tax purposes; or

                 (v)      any Restricted Payments not prohibited by Section
         4.04.

Notwithstanding the foregoing, any transaction or series of related
transactions covered by the first paragraph of this Section 4.08 and not
covered by clauses (ii) through (v) of this paragraph, the aggregate amount of
which exceeds $1 million in value, must be approved or determined to be fair in
the manner provided for in clause (i)(A) or (B) above.

                 SECTION 4.09.  Limitation on Liens.  The Company will not, and
will not permit any Restricted Subsidiary to, create, incur, assume or suffer
to exist any Lien on any of its assets or properties of any character
(including, without limitation, licenses), or any shares of Capital Stock or
Indebtedness of any Restricted Subsidiary, without making effective provision
for all of the Notes and all other amounts due under this Indenture to be
directly secured equally and ratably with (or, if the obligation or liability
to be secured by such Lien is subordinated in right of payment to the Notes,
prior to) the obligation or liability secured by such Lien.

                 The foregoing limitation does not apply to:

                 (i)      Liens existing on the Closing Date;

                 (ii)     Liens granted after the Closing Date on any assets or
         Capital Stock of the Company or its Restricted Subsidiaries created in
         favor of the Holders;

                 (iii)    Liens with respect to the assets of a Restricted
         Subsidiary granted by such Restricted Subsidiary to the Company or a
         Wholly Owned Restricted Subsidiary to secure Indebtedness owing to the
         Company or such other Restricted Subsidiary;

                 (iv)     Liens securing Indebtedness which is Incurred to
         refinance secured Indebtedness which is permitted to be Incurred under
         clause (iii) of the second paragraph of Section 4.03(a); provided that
         such Liens do not extend to or cover any property or assets of the
         Company or any Restricted Subsidiary other than the property or assets
         securing the Indebtedness being refinanced;

                 (v)      Liens on the Capital Stock of, or any property or
         assets of, a Restricted Subsidiary securing Indebtedness of such
         Restricted Subsidiary permitted under Section 4.03;
<PAGE>   48
                                       42

                 (vi)     Liens on the Capital Stock of Restricted Subsidiaries
         securing up to $100.0 million of Indebtedness Incurred under clause
         (vii) of the second paragraph of Section 4.03(a); or

                 (vii)    Permitted Liens.

                 SECTION 4.10.  Limitation on Asset Sales.  The Company will
not, and will not permit any Restricted Subsidiary to, consummate any Asset
Sale, unless (i) the consideration received by the Company or such Restricted
Subsidiary is at least equal to the fair market value of the assets sold or
disposed of and (ii) at least 75% of the consideration received consists of
cash or Temporary Cash Investments; provided, however, that this clause (ii)
shall not apply to long-term assignments in capacity in a telecommunications
network. In the event and to the extent that the Net Cash Proceeds received by
the Company or any of its Restricted Subsidiaries from one or more Asset Sales
occurring on or after the Closing Date in any period of 12 consecutive months
exceed 10% of Adjusted Consolidated Net Tangible Assets (determined as of the
date closest to the commencement of such 12-month period for which a
consolidated balance sheet of the Company and its Subsidiaries has been filed
with the Commission pursuant to Section 4.17), then the Company shall or shall
cause the relevant Restricted Subsidiary to (i) within 12 months after the date
Net Cash Proceeds so received exceed 10% of Adjusted Consolidated Net Tangible
Assets (A) apply an amount equal to such excess Net Cash Proceeds to
permanently repay unsubordinated Indebtedness of the Company, or any Restricted
Subsidiary providing a Subsidiary Guarantee pursuant to Section 4.07 or
Indebtedness of any other Restricted Subsidiary, in each case owing to a Person
other than the Company or any of its Restricted Subsidiaries or (B) invest an
equal amount, or the amount not so applied pursuant to clause (A) (or enter
into a definitive agreement committing to so invest within 12 months after the
date of such agreement), in property or assets (other than current assets) of a
nature or type or that are used in a business (or in a company having property
and assets of a nature or type, or engaged in a business) similar or related to
the nature or type of the property and assets of, or the business of, the
Company and its Restricted Subsidiaries existing on the date of such investment
(as determined in good faith by the Board of Directors, whose determination
shall be conclusive and evidenced by a Board Resolution) and (ii) apply (no
later than the end of the 12-month period referred to in clause (i)) such
excess Net Cash Proceeds (to the extent not applied pursuant to clause (i)) as
provided in the following paragraph of this Section 4.10. The amount of such
excess Net Cash Proceeds required to be applied (or to be committed to be
applied) during such 12-month period as set forth in clause (i) of the
preceding sentence and not applied as so required by the end of such period
shall constitute "Excess Proceeds."

                 If, as of the first day of any calendar month, the aggregate
amount of Excess Proceeds not theretofore subject to an Offer to Purchase
pursuant to this Section 4.10 totals at least $5 million, the Company must
commence, not later than the fifteenth Business Day of such month, and
consummate an Offer to Purchase from the Holders on a pro rata basis an
aggregate principal amount of Notes equal to the Excess Proceeds on such date,
at a purchase price equal to
<PAGE>   49
                                       43

100% of the principal amount of the Notes, plus, in each case, accrued interest
to the Payment Date.

                 SECTION 4.11.  Repurchase of Notes upon a Change of Control.
The Company must commence, within 30 days of the occurrence of a Change of
Control, and consummate an Offer to Purchase for all Notes then outstanding, at
a purchase price equal to 101% of the principal amount thereof, plus accrued
interest to the Payment Date.

                 SECTION 4.12.  Existence.  Subject to Articles Four and Five
of this Indenture, the Company will do or cause to be done all things necessary
to preserve and keep in full force and effect its existence and the existence
of each Restricted Subsidiary in accordance with the respective organizational
documents of the Company and each Restricted Subsidiary and the rights (whether
pursuant to charter, partnership certificate, agreement, statute or otherwise),
material licenses and franchises of the Company and each Restricted Subsidiary;
provided that the Company shall not be required to preserve any such right,
license or franchise, or the existence of any Restricted Subsidiary, if the
maintenance or preservation thereof is no longer desirable in the conduct of
the business of the Company and its Restricted Subsidiaries taken as a whole.

                 SECTION 4.13.  Payment of Taxes and Other Claims.  The Company
will pay or discharge and shall cause each of its Restricted Subsidiaries to
pay or discharge, or cause to be paid or discharged, before the same shall
become delinquent (i) all material taxes, assessments and governmental charges
levied or imposed upon (a) the Company or any such Restricted Subsidiary, (b)
the income or profits of any such Restricted Subsidiary which is a corporation
or (c) the property of the Company or any such Restricted Subsidiaries and (ii)
all material lawful claims for labor, materials and supplies that, if unpaid,
might by law become a lien upon the property of the Company or any such
Restricted Subsidiary; provided that the Company shall not be required to pay
or discharge, or cause to be paid or discharged, any such tax, assessment,
charge or claim the amount, applicability or validity of which is being
contested in good faith by appropriate proceedings and for which adequate
reserves have been established.

                 SECTION 4.14.  Maintenance of Properties and Insurance.  The
Company will cause all properties used or useful in the conduct of its business
or the business of any of its Restricted Subsidiaries, to be maintained and
kept in good condition, repair and working order and supplied with all
necessary equipment and will cause to be made all necessary repairs, renewals,
replacements, betterments and improvements thereof, all as in the judgment of
the Company may be necessary so that the business carried on in connection
therewith may be properly conducted at all times; provided that nothing in this
Section 4.14 shall prevent the Company or any such Restricted Subsidiary from
discontinuing the use, operation or maintenance of any of such properties or
disposing of any of them, if such discontinuance or disposal is, in the
judgment of the Company, desirable in the conduct of the business of the
Company or such Restricted Subsidiary.
<PAGE>   50
                                       44


                 The Company will provide or cause to be provided, for itself
and its Restricted Subsidiaries, insurance (including appropriate
self-insurance) against loss or damage of the kinds customarily insured against
by corporations similarly situated and owning like properties, with reputable
insurers or with the government of the United States of America, or an agency
or instrumentality thereof, in such amounts, with such deductibles and by such
methods as shall be customary for corporations similarly situated in the
industry in which the Company or such Restricted Subsidiary, as the case may
be, is then conducting business.

                 SECTION 4.15.  Notice of Defaults.  In the event that the
Company becomes aware of any Default or Event of Default the Company, promptly
after it becomes aware thereof, will give written notice thereof to the
Trustee.

                 SECTION 4.16.  Compliance Certificates.  (a)  The Company
shall deliver to the Trustee, within 45 days after the end of each fiscal
quarter (90 days after the end of the last fiscal quarter of each year), an
Officers' Certificate stating whether or not the signers know of any Default or
Event of Default that occurred during such fiscal quarter.  In the case of the
Officers' Certificate delivered within 90 days of the end of the Company's
fiscal year, such certificate shall contain a certification from the principal
executive officer, principal financial officer or principal accounting officer
that a review has been conducted of the activities of the Company and its
Restricted Subsidiaries and the Company's and its Restricted Subsidiaries'
performance under this Indenture and that, to the knowledge of such Officers,
the Company has complied with all conditions and covenants under this
Indenture.  For purposes of this Section 4.16, such compliance shall be
determined without regard to any period of grace or requirement of notice
provided under this Indenture.  If they do know of such a Default or Event of
Default, the certificate shall describe any such Default or Event of Default
and its status.  The first certificate to be delivered pursuant to this Section
4.16(a) shall be for the first fiscal quarter beginning after the execution of
this Indenture.

                 (b)      So long as (and to the extent) not prohibited by the
then current recommendations of the American Institute of Certified Public
Accountants, the Company shall deliver to the Trustee, within 90 days after the
end of the Company's fiscal year, a certificate signed by the Company's
independent certified public accountants stating (i) that their audit
examination has included a review of the terms of this Indenture and the Notes
as they relate to accounting matters, (ii) that they have read the most recent
Officers' Certificate delivered to the Trustee pursuant to paragraph (a) of
this Section 4.16 and (iii) whether, in connection with their audit
examination, anything came to their attention that caused them to believe that
the Company was not in compliance with any of the terms, covenants, provisions
or conditions of Article Four and Section 5.01 of this Indenture as they
pertain to accounting matters and, if any Default or Event of Default has come
to their attention, specifying the nature and period of existence thereof;
provided that such independent certified public accountants shall not be liable
in respect of such statement by reason of any failure to obtain knowledge of
any such Default or Event of Default that would not come to the attention of
such accountants in the course of an audit
<PAGE>   51
                                       45

examination conducted in accordance with generally accepted auditing standards
in effect at the date of such examination.

                 (c)      Within 90 days of the end of each of the Company's
fiscal years, the Company shall deliver to the Trustee a list of all
Significant Subsidiaries.  The Trustee shall have no duty with respect to any
such list except to keep it on file and available for inspection by the
Holders.

                 SECTION 4.17.  Commission Reports and Reports to Holders.  The
Company shall file with the Commission the annual, quarterly and other reports
and other information required by Sections 13(a) or 15(d) under the Securities
Exchange Act of 1934, regardless of whether such Sections of the Exchange Act
are applicable to the Company.  The Company shall supply the Trustee and each
Holder or shall supply to the Trustee for forwarding to each such Holder,
without cost to such Holder, copies of such reports and other information.
Delivery of such reports, information and documents to the Trustee is for
informational purposes only and the Trustee's receipt of such shall not
constitute constructive notice of any information contained therein or
determinable from information (including mathematical calculations) contained
therein, including the Company's compliance with any of its covenants hereunder
(as to which the Trustee is entitled to rely exclusively on Officers'
Certificates).  The Company also shall comply with the other provisions of TIA
Section 314(a).

                 SECTION 4.18.  Waiver of Stay, Extension or Usury Laws.  The
Company covenants (to the extent that it may lawfully do so) that it will not
at any time insist upon, or plead, or in any manner whatsoever claim or take
the benefit or advantage of, any stay or extension law or any usury law or
other law that would prohibit or forgive the Company from paying all or any
portion of the principal of, premium, if any, or interest on the Notes as
contemplated herein, wherever enacted, now or at any time hereafter in force,
or that may affect the covenants or the performance of this Indenture; and (to
the extent that it may lawfully do so) the Company 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.

                 SECTION 4.19.  Limitation on Sale-Leaseback Transactions.  The
Company will not, and will not permit any Restricted Subsidiary to, enter into
any sale-leaseback transaction involving any of its assets or properties
whether now owned or hereafter acquired, whereby the Company or a Restricted
Subsidiary sells or transfers such assets or properties and then or thereafter
leases such assets or properties or any part thereof or any other assets or
properties which the Company or such Restricted Subsidiary, as the case may be,
intends to use for substantially the same purpose or purposes as the assets or
properties sold or transferred.

                 The foregoing restriction does not apply to any sale-leaseback
transaction if:
<PAGE>   52
                                       46

                 (i)      the lease is for a period, including renewal rights,
         of not in excess of three years;

                 (ii)     the lease secures or relates to industrial revenue or
         pollution control bonds;

                 (iii)    the transaction is solely between the Company and any
         Wholly Owned Restricted Subsidiary or solely between Wholly Owned
         Restricted Subsidiaries; or

                 (iv)     the Company or such Restricted Subsidiary, within 12
         months after the sale or transfer of any assets or properties is
         completed, applies an amount not less than the net proceeds received
         from such sale in accordance with clause (A) or (B) of the first
         paragraph of Section 4.10.


                                  ARTICLE FIVE
                             SUCCESSOR CORPORATION

                 SECTION 5.01.  When Company May Merge, Etc.  The Company shall
not consolidate with, merge with or into, or sell, convey, transfer, lease or
otherwise dispose of all or substantially all of its property and assets (as an
entirety or substantially an entirety in one transaction or a series of related
transactions) to, any Person or permit any Person to merge with or into the
Company unless:

                 (i)      the Company shall be the continuing Person, or the
         Person (if other than the Company) formed by such consolidation or
         into which the Company is merged or that acquired or leased such
         property and assets of the Company shall be a corporation organized
         and validly existing under the laws of the United States of America or
         any jurisdiction thereof and shall expressly assume, by a supplemental
         indenture, executed and delivered to the Trustee, all of the
         obligations of the Company on all of the Notes and under this
         Indenture;

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

                 (iii)    immediately after giving effect to such transaction
         on a pro forma basis, the Company or any Person becoming the successor
         obligor of the Notes shall have a Consolidated Net Worth equal to or
         greater than the Consolidated Net Worth of the Company immediately
         prior to such transaction;

                 (iv)     immediately after giving effect to such transaction
         on a pro forma basis the Company, or any Person becoming the successor
         obligor of the Notes, as the case may be, could Incur at least $1.00
         of Indebtedness under the first paragraph of Section 4.03;
<PAGE>   53
                                       47

         provided that this clause (iv) shall not apply to (x) a consolidation,
         merger or sale of all (but not less than all) of the assets of the
         Company if all Liens and Indebtedness of the Company or any Person
         becoming the successor obligor on the Notes, as the case may be, and
         its Restricted Subsidiaries outstanding immediately after such
         transaction would, if Incurred at such time, have been permitted to be
         Incurred (and all such Liens and Indebtedness, other than Liens and
         Indebtedness of the Company and its Restricted Subsidiaries
         outstanding immediately prior to the transaction, shall be deemed to
         have been Incurred) for all purposes of this Indenture or (y) a
         consolidation, merger or sale of all or substantially all of the
         assets of the Company if immediately after giving effect to such
         transaction on a pro forma basis, the Company or any Person becoming
         the successor obligor of the Notes shall have a Consolidated Leverage
         Ratio equal to or less than the Consolidated Leverage Ratio of the
         Company immediately prior to such transaction; and

                 (v)      the Company delivers to the Trustee an Officers'
         Certificate (attaching the arithmetic computations to demonstrate
         compliance with clauses (iii) and (iv) above) and Opinion of Counsel,
         in each case stating that such consolidation, merger or transfer and
         such supplemental indenture complies with this provision and that all
         conditions precedent provided for herein relating to such transaction
         have been complied with;

provided, however, that clauses (iii) and (iv) above do not apply if, in the
good faith determination of the Board of Directors of the Company, whose
determination shall be evidenced by a Board Resolution, the principal purpose
of such transaction is to change the state of incorporation of the Company; and
provided further that any such transaction shall not have as one of its
purposes the evasion of the foregoing limitations.

                 SECTION 5.02.  Successor Substituted.  Upon any consolidation
or merger, or any sale, conveyance, transfer, lease or other disposition of all
or substantially all of the property and assets of the Company in accordance
with Section 5.01 of this Indenture, the successor Person formed by such
consolidation or into which the Company is merged or to which such sale,
conveyance, transfer, lease or other disposition 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 the predecessor corporation shall be
relieved of all obligations and covenants under this Indenture and the Notes;
provided that the Company shall not be released from its obligation to pay the
principal of, premium, if any, or interest on the Notes in the case of a lease
of all or substantially all of its property and assets.
<PAGE>   54
                                       48

                                  ARTICLE SIX
                              DEFAULT AND REMEDIES

                 SECTION 6.01.  Events of Default.  An "Event of Default" shall
occur with respect to the Notes if:

                 (a)      the Company defaults in the payment of principal of
         (or premium, if any, on) any Note when the same becomes due and
         payable at maturity, upon acceleration, redemption or otherwise;

                 (b)      the Company defaults in the payment of interest on
         any Note when the same becomes due and payable, and such default
         continues for a period of 30 days; provided that a failure to make any
         of the first six scheduled interest payments on the Notes on the
         applicable Interest Payment Date will constitute an Event of Default
         with no grace or cure period;

                 (c)      the Company defaults in the performance, or breaches
         the provisions of Article Five or the fails to make or consummate an
         Offer to Purchase in accordance with Section 4.10 or Section 4.11;

                 (d)      the Company defaults in the performance of or
         breaches any other covenant or agreement of the Company in this
         Indenture or under the Notes (other than a default specified in clause
         (a), (b) or (c) above) and such default or breach continues for a
         period of 30 consecutive days after written notice by the Trustee or
         the Holders of 25% or more in aggregate principal amount of the Notes,

                 (e)      there occurs with respect to any issue or issues of
         Indebtedness of the Company or any Significant Subsidiary having an
         outstanding principal amount of $5 million or more in the aggregate
         for all such issues of all such Persons, whether such Indebtedness now
         exists or shall hereafter be created, (I) an event of default that has
         caused the holder thereof to declare such Indebtedness to be due and
         payable prior to its Stated Maturity and such Indebtedness has not
         been discharged in full or such acceleration has not been rescinded or
         annulled within 30 days of such acceleration and/or (II) the failure
         to make a principal payment at the final (but not any interim) fixed
         maturity and such defaulted payment shall not have been made, waived
         or extended within 30 days of such payment default;

                 (f)      any final judgment or order (not covered by
         insurance) for the payment of money in excess of $5 million in the
         aggregate for all such final judgments or orders against all such
         Persons (treating any deductibles, self-insurance or retention as not
         so covered) shall be rendered against the Company or any Significant
         Subsidiary and shall not be paid or discharged, and there shall be any
         period of 30 consecutive days following
<PAGE>   55
                                       49

         entry of the final judgment or order that causes the aggregate amount
         for all such final judgments or orders outstanding and not paid or
         discharged against all such Persons to exceed $5 million during which
         a stay of enforcement of such final judgment or order, by reason of a
         pending appeal or otherwise, shall not be in effect;

                 (g)      a court having jurisdiction in the premises enters a
         decree or order for (A) relief in respect of the Company or any
         Significant Subsidiary in an involuntary case under any applicable
         bankruptcy, insolvency or other similar law now or hereafter in
         effect, (B) appointment of a receiver, liquidator, assignee,
         custodian, trustee, sequestrator or similar official of the Company or
         any Significant Subsidiary or for all or substantially all of the
         property and assets of the Company or any Significant Subsidiary or
         (C) the winding up or liquidation of the affairs of the Company or any
         Significant Subsidiary and, in each case, such decree or order shall
         remain unstayed and in effect for a period of 30 consecutive days;

                 (h)      the Company or any Significant Subsidiary (A)
         commences a voluntary case under any applicable bankruptcy, insolvency
         or other similar law now or hereafter in effect, or consents to the
         entry of an order for relief in an involuntary case under any such
         law, (B) consents to the appointment of or taking possession by a
         receiver, liquidator, assignee, custodian, trustee, sequestrator or
         similar official of the Company or any Significant Subsidiary or for
         all or substantially all of the property and assets of the Company or
         any Significant Subsidiary or (C) effects any general assignment for
         the benefit of creditors; or

                 (i)      the Pledge Agreement shall cease to be in full force
         and effect or enforceable in accordance with its terms, other than in
         accordance with its terms.

                 SECTION 6.02.  Acceleration.  If an Event of Default (other
than an Event of Default specified in clause (g) or (h) of Section 6.01 that
occurs with respect to the Company) occurs and is continuing under this
Indenture, the Trustee or the Holders of at least 25% in aggregate principal
amount of the Notes, then outstanding, by written notice to the Company (and to
the Trustee if such notice is given by the Holders), may, and the Trustee at
the request of such Holders shall, declare the principal of, premium, if any,
and accrued interest on the Notes to be immediately due and payable. Upon a
declaration of acceleration, such principal of, premium, if any, and accrued
interest shall be immediately due and payable. In the event of a declaration of
acceleration because an Event of Default set forth in clause (e) of Section
6.01 has occurred and is continuing, such declaration of acceleration shall be
automatically rescinded and annulled if the event of default triggering such
Event of Default pursuant to clause (e) shall be remedied or cured by the
Company or the relevant Significant Subsidiary or waived by the holders of the
relevant Indebtedness within 60 days after the declaration of acceleration with
respect thereto. If an Event of Default specified in clause (g) or (h) of
Section 6.01 occurs with respect to the Company, the principal of, premium, if
any, and accrued interest on the Notes then outstanding
<PAGE>   56
                                       50

shall ipso facto become and be immediately due and payable without any
declaration or other act on the part of the Trustee or any Holder.

                 At any time after such a declaration of acceleration, but
before a judgment or decree for the payment of the money due has been obtained
by the Trustee, the Holders of at least a majority in principal amount of the
outstanding Notes by written notice to the Company and to the Trustee, may
waive all past Defaults and rescind and annul such declaration of acceleration
and its consequences if (i) all existing Events of Default, other than the
non-payment of the principal of, premium, if any, and accrued interest on the
Notes that have become due solely by such declaration of acceleration, have
been cured or waived and (ii) the rescission would not conflict with any
judgment or decree of a court of competent jurisdiction.

                 SECTION 6.03.  Other Remedies.  If an Event of Default occurs
and is continuing, the Trustee may pursue any available remedy by proceeding at
law or in equity to collect the payment of principal of, premium, if any, or
interest on the Notes or to enforce the performance of any provision of the
Notes or this Indenture.

                 The Trustee may maintain a proceeding even if it does not
possess any of the Notes or does not produce any of them in the proceeding.

                 SECTION 6.04.  Waiver of Past Defaults.  Subject to Sections
6.02, 6.07 and 9.02, the Holders of at least a majority in principal amount of
the outstanding Notes, by notice to the Trustee, may waive an existing Default
or Event of Default and its consequences, except a Default in the payment of
principal of, premium, if any, or interest on any Note as specified in clause
(a) or (b) of Section 6.01 or in respect of a covenant or provision of this
Indenture which cannot be modified or amended without the consent of the holder
of each outstanding Note 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 Event of Default or impair any
right consequent thereto.

                 SECTION 6.05.  Control by Majority.  The Holders of at least a
majority in aggregate principal amount of the outstanding Notes may direct the
time, method and place of conducting any proceeding for any remedy available to
the Trustee or exercising any trust or power conferred on the Trustee. However,
the Trustee may refuse to follow any direction that conflicts with law or this
Indenture, that may involve the Trustee in personal liability, or that the
Trustee determines in good faith may be unduly prejudicial to the rights of
Holders of Notes not joining in the giving of such direction and may take any
other action it deems proper that is not inconsistent with any such direction
received from Holders of Notes.
<PAGE>   57
                                       51

                 SECTION 6.06.  Limitation on Suits.  A Holder may not
institute any proceeding, judicial or otherwise, with respect to this Indenture
or the Notes, or for the appointment of a receiver or trustee, or for any other
remedy hereunder unless:

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

                 (ii)     the Holders of at least 25% in aggregate principal
         amount of outstanding Notes make a written request to the Trustee to
         pursue the remedy;

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

                 (iv)     the Trustee does not comply with the request within
         60 days after receipt of the request and the offer of indemnity; and

                 (v)      during such 60-day period, the Holders of a majority
         in aggregate principal amount of the outstanding Notes do not give the
         Trustee a direction that is inconsistent with the request.

                 For purposes of Section 6.05 of this Indenture and this
Section 6.06, the Trustee shall comply with TIA Section 316(a) in making any
determination of whether the Holders of the required aggregate principal amount
of outstanding Notes have concurred in any request or direction of the Trustee
to pursue any remedy available to the Trustee or the Holders with respect to
this Indenture or the Notes or otherwise under the law.

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

                 SECTION 6.07.  Rights of Holders to Receive Payment.
Notwithstanding any other provision of this Indenture, the right of any Holder
of a Note to receive payment of the principal of, premium, if any, or interest
on, such Note or to bring suit for the enforcement of any such payment, on or
after the due date expressed in the Notes, shall not be impaired or affected
without the consent of such Holder.

                 SECTION 6.08.  Collection Suit by Trustee.  If an Event of
Default in payment of principal, premium or interest specified in clause (a),
(b) or (c) of Section 6.01 occurs and is continuing, the Trustee may recover
judgment in its own name and as trustee of an express trust against the Company
or any other obligor of the Notes for the whole amount of principal, premium,
if any, and accrued interest remaining unpaid, together with interest on
overdue principal, premium, if any, and, to the extent that payment of such
interest is lawful, interest on overdue installments of interest, in each case
at the rate specified in the Notes, and such further
<PAGE>   58
                                       52

amount as shall be sufficient to cover the costs and expenses of collection,
including the reasonable compensation, expenses, disbursements and advances of
the Trustee, its agents and counsel.

                 SECTION 6.09.  Trustee May File Proofs of Claim.  The Trustee
may file such proofs of claim and other papers or documents as may be necessary
or advisable in order to have the claims of the Trustee (including any claim
for the reasonable compensation, expenses, disbursements and advances of the
Trustee, its agents and counsel, and any other amounts due the Trustee under
Section 7.07) and the Holders allowed in any judicial proceedings relative to
the Company (or any other obligor of the Notes), its creditors or its property
and shall be entitled and empowered to collect and receive any monies,
securities or other property payable or deliverable upon conversion or exchange
of the Notes or upon 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 to it for the reasonable compensation, expenses,
disbursements and advances of the Trustee, its agent and counsel, and any other
amounts due the Trustee under Section 7.07.  Nothing herein contained shall be
deemed to empower 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 Notes or the rights of any Holder thereof, or to
authorize the Trustee to vote in respect of the claim of any Holder in any such
proceeding.

                 SECTION 6.10.  Priorities.  If the Trustee collects any money
pursuant to this Article Six, it shall pay out the money in the following
order:

                 First:  to the Trustee for all amounts due under Section 7.07;

                 Second:  to Holders for amounts then due and unpaid for
         principal of, premium, if any, and interest on the Notes 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 Notes for principal, premium, if any,
         and interest, respectively; and

                 Third:  to the Company or any other obligors of the Notes, as
         their interests may appear, or as a court of competent jurisdiction
         may direct.

                 The Trustee, upon prior written notice to the Company, may fix
a record date and payment date for any payment to Holders pursuant to this
Section 6.10.

                 SECTION 6.11.  Undertaking for Costs.  In any suit for the
enforcement of any right or remedy under this Indenture or in any suit against
the Trustee for any action taken or
<PAGE>   59
                                       53

omitted by it as Trustee, a court may require any party litigant in such suit
to file an undertaking to pay the costs of the suit, and the court may assess
reasonable costs, including reasonable attorneys' fees and expenses, against
any party litigant in the suit having due regard to the merits and good faith
of the claims or defenses made by the party litigant.  This Section 6.11 does
not apply to a suit by the Trustee, a suit by a Holder pursuant to Section 6.07
of this Indenture, or a suit by Holders of more than 10% in principal amount of
the outstanding Notes.

                 SECTION 6.12.  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 Company, Trustee and the Holders shall continue
as though no such proceeding had been instituted.

                 SECTION 6.13.  Rights and Remedies Cumulative.  Except as
otherwise provided with respect to the replacement or payment of mutilated,
destroyed, lost or wrongfully taken Notes in Section 2.07, 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.  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 6.14.  Delay or Omission Not Waiver.  No delay or
omission of the Trustee or of any Holder 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 Six 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 or by the Holders, as the case may be.


                                 ARTICLE SEVEN
                                    TRUSTEE

                 SECTION 7.01.  General.  The duties and responsibilities of
the Trustee shall be as provided by the TIA and as set forth herein.
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
<PAGE>   60
                                       54

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 Article Seven.

                 SECTION 7.02.  Certain Rights of Trustee.  Subject to TIA
Sections 315(a) through (d):

                 (i)      the Trustee may conclusively 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 (whether in its original or
         facsimile form) believed by it to be genuine and to have been signed
         or presented by the proper person.  The Trustee need not investigate
         any fact or matter stated in the document;

                 (ii)     before the Trustee acts or refrains from acting, it
         may require an Officers' Certificate and/or an Opinion of Counsel,
         which shall conform to Section 11.03 or Section 11.04, as the case may
         be.  The Trustee shall not be liable for any action it takes or omits
         to take in good faith in reliance on such certificate or opinion;

                 (iii)    the Trustee may act through attorneys and agents of
         its selection and the advice of such attorneys and agents 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.  The Trustee shall not be responsible for the
         misconduct or negligence of any agent appointed with due care;

                 (iv)     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, unless such Holders shall
         have offered to the Trustee reasonable security or indemnity against
         the costs, expenses and liabilities that might be incurred by it in
         compliance with such request or direction;

                 (v)      the Trustee shall not be liable for any action it
         takes or omits to take in good faith that it believes to be authorized
         or within its rights or powers or for any action it takes or omits to
         take in accordance with the direction of the Holders of a majority in
         principal amount of the outstanding Notes relating to the time, method
         and place of conducting any proceeding for any remedy available to the
         Trustee, or exercising any trust or power conferred upon the Trustee,
         under this Indenture; provided that the Trustee's conduct does not
         constitute gross negligence or bad faith;

                 (vi)     whenever in the administration of this Indenture the
         Trustee shall deem it desirable that a making be proved or established
         prior to taking, suffering or omitting any action hereunder, the
         Trustee (unless other evidence be herein specifically prescribed)
<PAGE>   61
                                       55

         may, in the absence of bad faith on its part, conclusively rely upon
         an Officer's Certificate; and

                 (vii)    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 at the sole cost of the Company and
         shall incur no liability or additional liability of any kind by reason
         of such inquiry or investigation.

                 SECTION 7.03.  Individual Rights of Trustee.  The Trustee, in
its individual or any other capacity, may become the owner or pledgee of Notes
and may otherwise deal with the Company or its Affiliates with the same rights
it would have if it were not the Trustee.  Any Agent may do the same with like
rights.  However, the Trustee is subject to TIA Sections 310(b) and 311.

                 SECTION 7.04.  Trustee's Disclaimer.  The Trustee (i) makes no
representation as to the validity or adequacy of this Indenture or the Notes,
(ii) shall not be accountable for the Company's use or application of the
proceeds from the Notes and (iii) shall not be responsible for any statement in
the Notes other than its certificate of authentication.

                 SECTION 7.05.  Notice of Default.  If any Default or any Event
of Default occurs and is continuing and if such Default or Event of Default is
actually known to a Responsible Officer of the Trustee, the Trustee shall mail
to each Holder in the manner and to the extent provided in TIA Section 313(c)
notice of the Default or Event of Default within 45 days after it occurs,
unless such Default or Event of Default has been cured; provided, however,
that, except in the case of a default in the payment of the principal of,
premium, if any, or interest on any Note, the Trustee shall be protected in
withholding such notice if and so long as the board of directors, the executive
committee or a trust committee of directors and/or Responsible Officers of the
Trustee in good faith determine that the withholding of such notice is in the
interest of the Holders.

                 SECTION 7.06.  Reports by Trustee to Holders.  Within 60 days
after each May 15, beginning with May 15, 1999, the Trustee shall mail to each
Holder as provided in TIA Section 313(c) a brief report dated as of such May
15, if required by TIA Section 313(a).

                 SECTION 7.07.  Compensation and Indemnity.  The Company shall
pay to the Trustee such compensation as shall be agreed upon in writing for its
services.  The compensation of the Trustee shall not be limited by any law on
compensation of a trustee of an express trust.
<PAGE>   62
                                       56

The Company shall reimburse the Trustee upon request for all reasonable
out-of-pocket expenses and advances incurred or made by the Trustee.  Such
expenses shall include the reasonable compensation and expenses of the
Trustee's agents and counsel.

                 The Company shall indemnify each of the Trustee and any
predecessor Trustee for, and hold it harmless against, any and all claim,
damage, loss or liability or expense, including taxes (other than taxes based
upon, measured by or determined by the income of the Trustee) incurred by it
without negligence or bad faith on its part in connection with the acceptance
or administration of this Indenture and its duties under this Indenture and the
Notes, including the costs and expenses of defending itself against any claim
or liability and of complying with any process served upon it or any of its
officers in connection with the exercise or performance of any of its powers or
duties under this Indenture and the Notes.

                 To secure the Company's payment obligations in this Section
7.07, the Trustee shall have a lien prior to the Notes on all money or property
held or collected by the Trustee, in its capacity as Trustee, except money or
property held in trust pursuant to the Pledge Agreement and money or property
held in trust to pay principal of, premium, if any, and interest on particular
Notes.

                 If the Trustee incurs expenses or renders services after the
occurrence of an Event of Default specified in clause (g) or (h) of Section
6.01, the expenses and the compensation for the services will be intended to
constitute expenses of administration under Title 11 of the United States
Bankruptcy Code or any applicable federal or state law for the relief of
debtors.

                 The provisions of this Section 7.07 shall survive the
termination of this Indenture.

                 SECTION 7.08.  Replacement of Trustee.  A resignation or
removal of the Trustee and appointment of a successor Trustee shall become
effective only upon the successor Trustee's acceptance of appointment as
provided in this Section 7.08.

                 The Trustee may resign at any time by so notifying the Company
in writing at least 30 days prior to the date of the proposed resignation.  The
Holders of a majority in principal amount of the outstanding Notes may remove
the Trustee by so notifying the Trustee in writing and may appoint a successor
Trustee with the consent of the Company.  The Company may remove the Trustee
if: (i) the Trustee is no longer eligible under Section 7.10; (ii) the Trustee
is adjudged a bankrupt or an insolvent; (iii) a receiver or other public
officer takes charge of the Trustee or its property; or (iv) the Trustee
becomes incapable of acting.

                 If the Trustee resigns or is removed, or if a vacancy exists
in the office of Trustee for any reason, the Company shall promptly appoint a
successor Trustee.  Within one year after the successor Trustee takes office,
the Holders of a majority in principal amount of the outstanding Notes may
appoint a successor Trustee to replace the successor Trustee appointed by
<PAGE>   63
                                       57

the Company.  If the successor Trustee does not deliver its written acceptance
required by the next succeeding paragraph of this Section 7.08 within 30 days
after the retiring Trustee resigns or is removed, the retiring Trustee, the
Company or the Holders of a majority in principal amount of the outstanding
Notes may, at the expense of the Company, petition any court of competent
jurisdiction for the appointment of a successor Trustee.

                 A successor Trustee shall deliver a written acceptance of its
appointment to the retiring Trustee and to the Company.  Immediately after the
delivery of such written acceptance, subject to the lien provided in Section
7.07, (i) the retiring Trustee shall transfer all property held by it as
Trustee to the successor Trustee, (ii) the resignation or removal of the
retiring Trustee shall become effective and (iii) the successor Trustee shall
have all the rights, powers and duties of the Trustee under this Indenture.  A
successor Trustee shall mail notice of its succession to each Holder.

                 If the Trustee is no longer eligible under Section 7.10, any
Holder who satisfies the requirements of TIA Section 310(b) may petition any
court of competent jurisdiction for the removal of the Trustee and the
appointment of a successor Trustee.

                 The Company shall give notice of any resignation and any
removal of the Trustee and each appointment of a successor Trustee to all
Holders.  Each notice shall include the name of the successor Trustee and the
address of its Corporate Trust Office.

                 Notwithstanding replacement of the Trustee pursuant to this
Section 7.08, the Company's obligation under Section 7.07 shall continue for
the benefit of the retiring Trustee.

                 SECTION 7.09.  Successor Trustee by Merger, Etc.  If the
Trustee consolidates with, merges or converts into, or transfers all or
substantially all of its corporate trust business to, another corporation or
national banking association, the resulting, surviving or transferee
corporation or national banking association without any further act shall be
the successor Trustee with the same effect as if the successor Trustee had been
named as the Trustee herein.

                 SECTION 7.10.  Eligibility.  This Indenture shall always have
a Trustee who satisfies the requirements of TIA Section 310(a)(1).  The Trustee
shall have a combined capital and surplus of at least $25,000,000 as set forth
in its most recent published annual report of condition.

                 SECTION 7.11.  Money Held in Trust.  The Trustee shall not be
liable for interest on any money received by it except as the Trustee may agree
with the Company.  Money held in trust by the Trustee need not be segregated
from other funds except to the extent required by law and except for money held
in trust pursuant to the Pledge Agreement and under Article Eight of this
Indenture.
<PAGE>   64
                                       58

                 SECTION 7.12.  Withholding Taxes.  The Trustee, as agent for
the Company, shall exclude and withhold from each payment of principal and
interest and other amounts due hereunder or under the Notes any and all
withholding taxes applicable thereto as required by law.  The Trustee agrees to
act as such withholding agent and, in connection therewith, whenever any
present or future taxes or similar charges are required to be withheld with
respect to any amounts payable in respect of the Notes, to withhold such
amounts and timely pay the same to the appropriate authority in the name of and
on behalf of the holders of the Notes, that it will file any necessary
withholding tax returns or statements when due.  The Company or the Trustee
shall, as promptly as possible after the payment of the taxes described above,
deliver to each holder of a Note appropriate documentation showing the payment
thereof, together with such additional documentary evidence as such holders may
reasonably request from time to time.


                                 ARTICLE EIGHT
                             DISCHARGE OF INDENTURE

                 SECTION 8.01.  Termination of Company's Obligations.  Except
as otherwise provided in this Section 8.01, the Company may terminate its
obligations under the Notes and this Indenture if:

                 (i)      all Notes previously authenticated and delivered
         (other than destroyed, lost or stolen Notes that have been replaced or
         Notes that are paid pursuant to Section 4.01 or Notes for whose
         payment money or securities have theretofore been held in trust and
         thereafter repaid to the Company, as provided in Section 8.05) have
         been delivered to the Trustee for cancellation and the Company has
         paid all sums payable by it hereunder; or

                 (ii)     (A) the Notes mature within one year or all of them
         are to be called for redemption within one year under arrangements
         satisfactory to the Trustee for giving the notice of redemption, (B)
         the Company irrevocably deposits in trust with the Trustee during such
         one-year period, under the terms of an irrevocable trust agreement in
         form and substance satisfactory to the Trustee, as trust funds solely
         for the benefit of the Holders for that purpose, money or U.S.
         Government Obligations sufficient (in the opinion of a nationally
         recognized firm of independent public accountants expressed in a
         written certification thereof delivered to the Trustee), without
         consideration of any reinvestment of any interest thereon, to pay
         principal, premium, if, any, and interest on the Notes to maturity or
         redemption, as the case may be, and to pay all other sums payable by
         it hereunder, (C) no Default or Event of Default with respect to the
         Notes shall have occurred and be continuing on the date of such
         deposit, (D) such deposit will not result in a breach or violation of,
         or constitute a default under, this Indenture or any other agreement
         or instrument to which the Company is a party or by which it is bound
         and (E) the Company has delivered to the Trustee an Officers'
         Certificate and an Opinion of
<PAGE>   65
                                       59

         Counsel, in each case stating that all conditions precedent provided
         for herein relating to the satisfaction and discharge of this
         Indenture have been complied with.

                 With respect to the foregoing clause (i), the Company's
obligations under Section 7.07 shall survive.  With respect to the foregoing
clause (ii), the Company's obligations in Sections 2.02, 2.03, 2.04, 2.05,
2.06, 2.07, 2.12, 4.01, 4.02, 7.07, 7.08, 8.04, 8.05 and 8.06 shall survive
until the Notes are no longer outstanding.  Thereafter, only the Company's
obligations in Sections 7.07, 8.05 and 8.06 shall survive.  After any such
irrevocable deposit, the Trustee upon request shall acknowledge in writing the
discharge of the Company's obligations under the Notes and this Indenture
except for those surviving obligations specified above.

                 SECTION 8.02.  Defeasance and Discharge of Indenture.  The
Company will be deemed to have paid and will be discharged from any and all
obligations in respect of the Notes on the 123rd day after the date of the
deposit referred to in clause (A) of this Section 8.02, and the provisions of
this Indenture will no longer be in effect with respect to the Notes, and the
Trustee, at the expense of the Company, shall execute proper instruments
acknowledging the same, except as to (i) rights of registration of transfer and
exchange, (ii) substitution of apparently mutilated, defaced, destroyed, lost
or stolen Notes, (iii) rights of Holders to receive payments of principal
thereof and interest thereon, (iv) the Company's obligations under Section
4.02, (v) the rights, obligations and immunities of the Trustee hereunder and
(vi) the rights of the Holders as beneficiaries of this Indenture with respect
to the property so deposited with the Trustee payable to all or any of them;
provided that the following conditions shall have been satisfied:

                 (A)      with reference to this Section 8.02, the Company has
         irrevocably deposited or caused to be irrevocably deposited with the
         Trustee (or another trustee satisfying the requirements of Section
         7.10 of this Indenture) and conveyed all right, title and interest for
         the benefit of the Holders, under the terms of an irrevocable trust
         agreement in form and substance satisfactory to the Trustee as trust
         funds in trust, specifically pledged to the Trustee for the benefit of
         the Holders as security for payment of the principal of, premium, if
         any, and interest, if any, on the Notes, and dedicated solely to, the
         benefit of the Holders, in and to (1) money in an amount, (2) U.S.
         Government Obligations that, through the payment of interest, premium,
         if any, and principal in respect thereof in accordance with their
         terms, will provide, not later than one day before the due date of any
         payment referred to in this clause (A), money in an amount or (3) a
         combination thereof in an amount 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, without consideration of the reinvestment of such
         interest and after payment of all federal, state and local taxes or
         other charges and assessments in respect thereof payable by the
         Trustee, the principal of, premium, if any, and accrued interest on
         the outstanding Notes at the Stated Maturity of such principal or
         interest; provided that the Trustee shall have been irrevocably
         instructed to apply such
<PAGE>   66
                                       60

         money or the proceeds of such U.S. Government Obligations to the
         payment of such principal, premium, if any, and interest with respect
         to the Notes;

                 (B)      such deposit will not result in a breach or violation
         of, or constitute a default under, this Indenture or any other
         agreement or instrument to which the Company is a party or by which it
         is bound;

                 (C)      immediately after giving effect to such deposit on a
         pro forma basis, no Default or Event of Default shall have occurred
         and be continuing on the date of such deposit or during the period
         ending on the 123rd day after such date of deposit;

                 (D)      the Company shall have delivered to the Trustee (1)
         either (x) a ruling directed to the Trustee received from the Internal
         Revenue Service to the effect that the Holders will not recognize
         income, gain or loss for federal income tax purposes as a result of
         the Company's exercise of its option under this Section 8.02 and will
         be subject to federal income tax on the same amount and in the same
         manner and at the same times as would have been the case if such
         option had not been exercised or (y) an Opinion of Counsel to the same
         effect as the ruling described in clause (x) above accompanied by a
         ruling to that effect published by the Internal Revenue Service,
         unless there has been a change in the applicable federal income tax
         law since the date of this Indenture such that a ruling from the
         Internal Revenue Service is no longer required and (2) an Opinion of
         Counsel to the effect that (x) the creation of the defeasance trust
         does not violate the Investment Company Act of 1940 and (y) after the
         passage of 123 days following the deposit (except, with respect to any
         trust funds for the account of any Holder who may be deemed to be an
         "insider" for purposes of the United States Bankruptcy Code, after one
         year following the deposit), the trust funds will not be subject to
         the effect of Section 547 of the United States Bankruptcy Code or
         Section 15 of the New York Debtor and Creditor Law in a case commenced
         by or against the Company under either such statute, and either (I)
         the trust funds will no longer remain the property of the Company (and
         therefore will not be subject to the effect of any applicable
         bankruptcy, insolvency, reorganization or similar laws affecting
         creditors' rights generally) or (II) if a court were to rule under any
         such law in any case or proceeding that the trust funds remained
         property of the Company, (a) assuming such trust funds remained in the
         possession of the Trustee prior to such court ruling to the extent not
         paid to the Holders, the Trustee will hold, for the benefit of the
         Holders, a valid and perfected security interest in such trust funds
         that is not avoidable in bankruptcy or otherwise except for the effect
         of Section 552(b) of the United States Bankruptcy Code on interest on
         the trust funds accruing after the commencement of a case under such
         statute and (b) the Holders will be entitled to receive adequate
         protection of their interests in such trust funds if such trust funds
         are used in such case or proceeding;
<PAGE>   67
                                       61

                 (E)      if the Notes are then listed on a national securities
         exchange, the Company shall have delivered to the Trustee an Opinion
         of Counsel to the effect that such deposit defeasance and discharge
         will not cause the Notes to be delisted; and

                 (F)      the Company has delivered to the Trustee an Officers'
         Certificate and an Opinion of Counsel, in each case stating that all
         conditions precedent provided for herein relating to the defeasance
         contemplated by this Section 8.02 have been complied with.

                 Notwithstanding the foregoing, prior to the end of the 123-day
(or one year) period referred to in clause (D)(2)(y) of this Section 8.02, none
of the Company's obligations under this Indenture shall be discharged.
Subsequent to the end of such 123-day (or one year) period with respect to this
Section 8.02, the Company's obligations in Sections 2.02, 2.03, 2.04, 2.05,
2.06, 2.07, 2.12, 4.01, 4.02, 7.07, 7.08, 8.05 and 8.06 shall survive until the
Notes are no longer outstanding.  Thereafter, only the Company's obligations in
Sections 7.07, 8.05 and 8.06 shall survive.  If and when a ruling from the
Internal Revenue Service or an Opinion of Counsel referred to in clause (D)(1)
of this Section 8.02 is able to be provided specifically without regard to, and
not in reliance upon, the continuance of the Company's obligations under
Section 4.01, then the Company's obligations under such Section 4.01 shall
cease upon delivery to the Trustee of such ruling or Opinion of Counsel and
compliance with the other conditions precedent provided for herein relating to
the defeasance contemplated by this Section 8.02.

                 After any such irrevocable deposit, the Trustee upon request
shall acknowledge in writing the discharge of the Company's obligations under
the Notes and this Indenture except for those surviving obligations in the
immediately preceding paragraph.

                 SECTION 8.03.  Defeasance of Certain Obligations.  The Company
may omit to comply with any term, provision or condition set forth in clauses
(iii) and (iv) under Section 5.01 and Sections 4.03 through 4.10 and Section
4.19, clause (c) under Section 6.01 with respect to such clauses (iii) and (iv)
under Section 5.01, clause (d) under Section 6.01 with respect to Sections
4.01, 4.02, 4.11 through 4.18 and 4.20 and clauses (e) and (f) under Section
6.01 shall be deemed not to be Events of Default, in each case with respect to
the outstanding Notes if:

                 (i)      with reference to this Section 8.03, the Company has
         irrevocably deposited or caused to be irrevocably deposited with the
         Trustee (or another trustee satisfying the requirements of Section
         7.10) and conveyed all right, title and interest to the Trustee for
         the benefit of the Holders, under the terms of an irrevocable trust
         agreement in form and substance satisfactory to the Trustee as trust
         funds in trust, specifically pledged to the Trustee for the benefit of
         the Holders as security for payment of the principal of, premium, if
         any, and interest, if any, on the Notes, and dedicated solely to, the
         benefit of the Holders, in and to (A) money in an amount, (B) U.S.
         Government Obligations that, through the payment of interest and
         principal in respect thereof in accordance with their terms, will
         provide, not later than one day before the due date of any payment
         referred to
<PAGE>   68
                                       62

         in this clause (i), money in an amount or (C) a combination thereof in
         an amount 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, without
         consideration of the reinvestment of such interest and after payment
         of all federal, state and local taxes or other charges and assessments
         in respect thereof payable by the Trustee, the principal of, premium,
         if any, and interest on the outstanding Notes on the Stated Maturity
         of such principal or interest; provided that the Trustee shall have
         been irrevocably instructed to apply such money or the proceeds of
         such U.S. Government Obligations to the payment of such principal,
         premium, if any, and interest with respect to the Notes;

                 (ii)     such deposit will not result in a breach or violation
         of, or constitute a default under, this Indenture or any other
         agreement or instrument to which the Company is a party or by which it
         is bound;

                 (iii)    no Default or Event of Default shall have occurred
         and be continuing on the date of such deposit;

                 (iv)     the Company has delivered to the Trustee an Opinion
         of Counsel to the effect that (A) the creation of the defeasance trust
         does not violate the Investment Company Act of 1940, (B) the Holders
         have a valid first-priority security interest in the trust funds, (C)
         the Holders will not recognize income, gain or loss for federal income
         tax purposes as a result of such deposit and defeasance of certain
         obligations and will be subject to federal income tax on the same
         amount and in the same manner and at the same times as would have been
         the case if such deposit and defeasance had not occurred and (D) after
         the passage of 123 days following the deposit (except, with respect to
         any trust funds for the account of any Holder who may be deemed to be
         an "insider" for purposes of the United States Bankruptcy Code, after
         one year following the deposit), the trust funds will not be subject
         to the effect of Section 547 of the United States Bankruptcy Code or
         Section 15 of the New York Debtor and Creditor Law in a case commenced
         by or against the Company under either such statute, and either (1)
         the trust funds will no longer remain the property of the Company (and
         therefore will not be subject to the effect of any applicable
         bankruptcy, insolvency, reorganization or similar laws affecting
         creditors' rights generally) or (2) if a court were to rule under any
         such law in any case or proceeding that the trust funds remained
         property of the Company, (x) assuming such trust funds remained in the
         possession of the Trustee prior to such court ruling to the extent not
         paid to the Holders, the Trustee will hold, for the benefit of the
         Holders, a valid and perfected security interest in such trust funds
         that is not avoidable in bankruptcy or otherwise (except for the
         effect of Section 552(b) of the United States Bankruptcy Code on
         interest on the trust funds accruing after the commencement of a case
         under such statute), (y) the Holders will be entitled to receive
         adequate protection of their interests in such trust funds if such
         trust funds are used in such case or proceeding and (z) no
<PAGE>   69
                                       63

         property, rights in property or other interests granted to the Trustee
         or the Holders in exchange for, or with respect to, such trust funds
         will be subject to any prior rights of holders of other Indebtedness
         of the Company or any of its Subsidiaries;

                 (v)      if the Notes are then listed on a national securities
         exchange, the Company shall have delivered to the Trustee an Opinion
         of Counsel to the effect that such deposit defeasance and discharge
         will not cause the Notes to be delisted; and

                 (vi)     the Company has delivered to the Trustee an Officers'
         Certificate and an Opinion of Counsel, in each case stating that all
         conditions precedent provided for herein relating to the defeasance
         contemplated by this Section 8.03 have been complied with.

                 SECTION 8.04.  Application of Trust Money.  Subject to Section
8.06, the Trustee or Paying Agent shall hold in trust money or U.S. Government
Obligations deposited with it pursuant to Section 8.01, 8.02 or 8.03, as the
case may be, and shall apply the deposited money and the money from U.S.
Government Obligations in accordance with the Notes and this Indenture to the
payment of principal of, premium, if any, and interest on the Notes; but such
money need not be segregated from other funds except to the extent required by
law.

                 SECTION 8.05.  Repayment to Company.  Subject to Sections
7.07, 8.01, 8.02 and 8.03, the Trustee and the Paying Agent shall promptly pay
to the Company upon request set forth in an Officers' Certificate any excess
money held by them at any time and thereupon shall be relieved from all
liability with respect to such money.  The Trustee and the Paying Agent shall
pay to the Company upon request any money held by them for the payment of
principal, premium, if any, or interest that remains unclaimed for two years;
provided that the Trustee or such Paying Agent before being required to make
any payment may cause to be published at the expense of the Company once in a
newspaper of general circulation in the City of New York or mail to each Holder
entitled to such money at such Holder's address (as set forth in the Security
Register) notice that such money remains unclaimed and that after a date
specified therein (which shall be at least 30 days from the date of such
publication or mailing) any unclaimed balance of such money then remaining will
be repaid to the Company.  After payment to the Company, Holders entitled to
such money must look to the Company for payment as general creditors unless an
applicable law designates another Person, and all liability of the Trustee and
such Paying Agent with respect to such money shall cease.

                 SECTION 8.06.  Reinstatement.  If the Trustee or Paying Agent
is unable to apply any money or U.S.  Government Obligations in accordance with
Section 8.01, 8.02 or 8.03, as the case may be, by reason of any legal
proceeding or by reason of any order or judgment of any court or governmental
authority enjoining, restraining or otherwise prohibiting such application, the
Company's obligations under this Indenture and the Notes shall be revived and
reinstated as though no deposit had occurred pursuant to Section 8.01, 8.02 or
8.03, as the case may be, until such time as the Trustee or Paying Agent is
permitted to apply all such money or U.S.
<PAGE>   70
                                       64

Government Obligations in accordance with Section 8.01, 8.02 or 8.03, as the
case may be; provided that, if the Company has made any payment of principal
of, premium, if any, or interest on any Notes because of the reinstatement of
its obligations, the Company shall be subrogated to the rights of the Holders
of such Notes to receive such payment from the money or U.S. Government
Obligations held by the Trustee or Paying Agent.


                                  ARTICLE NINE
                      AMENDMENTS, SUPPLEMENTS AND WAIVERS

                 SECTION 9.01.  Without Consent of Holders.  The Company, when
authorized by a resolution of its Board of Directors, and the Trustee may amend
or supplement this Indenture or the Notes without notice to or the consent of
any Holder:

                 (1)      to cure any ambiguity, defect or inconsistency in
         this Indenture; provided that such amendments or supplements shall not
         adversely affect the interests of the Holders in any material respect;

                 (2)      to comply with Article Five;

                 (3)      to comply with any requirements of the Commission in
         connection with the qualification of this Indenture under the TIA;

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

                 (5)      to make any change that, in the good faith opinion of
         the Board of Directors as evidenced by a Board Resolution, does not
         materially and adversely affect the rights of any Holder.

                 SECTION 9.02.  With Consent of Holders.  Subject to Sections
6.04 and 6.07 and without prior notice to the Holders, the Company, when
authorized by its Board of Directors (as evidenced by a Board Resolution), and
the Trustee may amend this Indenture, the Pledge Agreement and the Notes with
the written consent of the Holders of a majority in aggregate principal amount
of the Notes then outstanding, and the Holders of a majority in aggregate
principal amount of the Notes then outstanding by written notice to the Trustee
may waive future compliance by the Company with any provision of this
Indenture, the Notes or the Pledge Agreement.

                 Notwithstanding the provisions of this Section 9.02, without
the consent of each Holder affected, an amendment or waiver, including a waiver
pursuant to Section 6.04, may not:
<PAGE>   71
                                       65

                 (i)      change the Stated Maturity of the principal of, or
         any installment of interest on, any Note,

                 (ii)     reduce the principal of, or premium, if any, or
         interest on, any Note,

                 (iii)    change the place or currency of payment of principal
         of, or premium, if any, or interest on, any Note or adversely affect
         any right of repayment at the option of any Holder of any Note,

                 (iv)     impair the right to institute suit for the
         enforcement of any payment on or after the Stated Maturity (or, in the
         case of a redemption, on or after the Redemption Date) of any Note,

                 (v)      reduce the above-stated percentage of outstanding
         Notes the consent of whose Holders is necessary to modify or amend
         this Indenture,

                 (vi)     waive a Default in the payment of principal of,
         premium, if any, or interest on the Notes,

                 (vii)    modify any of the provisions of this Section 9.02,
         except to increase any such percentage or to provide that certain
         other provisions of this Indenture cannot be modified or waived
         without the consent of the Holder of each outstanding Note affected
         thereby,

                 (viii)   reduce the percentage or aggregate principal amount
         of outstanding Notes the consent of whose Holders is necessary for
         waiver of compliance with certain provisions of this Indenture or for
         waiver of certain defaults, or

                 (ix)     modify Article Ten or the Pledge Agreement in a
         manner that adversely affects the right of any Holder in any material
         respect.

                 It shall not be necessary for the consent of the Holders under
this Section 9.02 to approve the particular form of any proposed amendment,
supplement or waiver, but it shall be sufficient if such consent approves the
substance thereof.

                 After an amendment, supplement or waiver under this Section
9.02 becomes effective, the Company shall mail to the Holders affected thereby
a notice briefly describing the amendment, supplement or waiver.  The Company
will mail supplemental indentures to Holders upon request.  Any failure of the
Company to mail such notice, or any defect therein, shall not, however, in any
way impair or affect the validity of any such supplemental indenture or waiver.
<PAGE>   72
                                       66

                 SECTION 9.03.  Revocation and Effect of Consent.  Until an
amendment or waiver becomes effective, a consent to it by a Holder is a
continuing consent by the Holder and every subsequent Holder of a Note or
portion of a Note that evidences the same debt as the Note of the consenting
Holder, even if notation of the consent is not made on any Note.  However, any
such Holder or subsequent Holder may revoke the consent as to its Note or
portion of its Note.  Such revocation shall be effective only if the Trustee
receives the notice of revocation before the date the amendment, supplement or
waiver becomes effective.  An amendment, supplement or waiver shall become
effective on receipt by the Trustee of written consents from the Holders of the
requisite percentage in principal amount of the outstanding Notes.

                 The Company may, but shall not be obligated to, fix a record
date for the purpose of determining the Holders entitled to consent to any
amendment, supplement or waiver.  If a record date is fixed, then,
notwithstanding the last two sentences of the immediately preceding paragraph,
those persons who were Holders at such record date (or their duly designated
proxies) and only those persons shall be entitled to consent to such amendment,
supplement or waiver or to revoke any consent previously given, whether or not
such persons continue to be Holders after such record date.  No such consent
shall be valid or effective for more than 90 days after such record date.

                 After an amendment, supplement or waiver becomes effective, it
shall bind every Holder unless it is of the type described in any of clauses
(i) through (viii) of Section 9.02.  In case of an amendment or waiver of the
type described in clauses (i) through (viii) of Section 9.02, the amendment or
waiver shall bind each Holder who has consented to it and every subsequent
Holder of a Note that evidences the same indebtedness as the Note of the
consenting Holder.

                 SECTION 9.04.  Notation on or Exchange of Notes.  If an
amendment, supplement or waiver changes the terms of a Note, the Trustee may
require the Holder to deliver it to the Trustee.  The Trustee may place an
appropriate notation on the Note about the changed terms and return it to the
Holder and the Trustee may place an appropriate notation on any Note thereafter
authenticated.  Alternatively, if the Company or the Trustee so determines, the
Company in exchange for the Note shall issue and the Trustee shall authenticate
a new Note that reflects the changed terms.

                 SECTION 9.05.  Trustee to Sign Amendments, Etc.  The Trustee
shall be entitled to receive, and shall be fully protected in relying upon, an
Opinion of Counsel stating that the execution of any amendment, supplement or
waiver authorized pursuant to this Article Nine is authorized or permitted by
this Indenture.  Subject to the preceding sentence, the Trustee shall sign such
amendment, supplement or waiver if the same does not adversely affect the
rights of the Trustee.  The Trustee may, but shall not be obligated to, execute
any such amendment, supplement or waiver that affects the Trustee's own rights,
duties or immunities under this Indenture or otherwise.
<PAGE>   73
                                       67


                 SECTION 9.06.  Conformity with Trust Indenture Act.  Every
supplemental indenture executed pursuant to this Article Nine shall conform to
the requirements of the TIA as then in effect.


                                  ARTICLE TEN
                                    SECURITY

                 SECTION 10.01.  Security.  (a)  On the Closing Date, the
Company shall (i) enter into the Pledge Agreement and comply with the terms and
provisions thereof and (ii) purchase the Pledged Securities to be pledged to
the Trustee for the benefit of the Holders in such amount as will be sufficient
upon receipt of scheduled interest and/or principal payments of such Pledged
Securities, in the opinion of a nationally recognized firm of independent
public accountants selected by the Company, to provide for payment in full of
the first six scheduled interest payments due on the Notes.  The Pledged
Securities shall be pledged by the Company to the Trustee for the benefit of
the Holders and shall be held by the Trustee in the Pledge Account pending
disposition pursuant to the Pledge Agreement.

                 (b)      Each Holder, by its acceptance of a Note, consents
and agrees to the terms of the Pledge Agreement (including, without limitation,
the provisions providing for foreclosure and release of the Pledged Securities)
as the same may be in effect or may be amended from time to time in accordance
with its terms, and authorizes and directs the Trustee to enter into the Pledge
Agreement and to perform its respective obligations and exercise its respective
rights thereunder in accordance therewith.  The Company will do or cause to be
done all such acts and things as may be necessary or proper, or as may be
required by the provisions of the Pledge Agreement, to assure and confirm to
the Trustee the security interest in the Pledged Securities contemplated
hereby, by the Pledge Agreement or any part thereof, as from time to time
constituted, so as to render the same available for the security and benefit of
this Indenture and of the Notes secured hereby, according to the intent and
purposes herein expressed.  The Company shall take, or shall cause to be taken,
upon request of the Trustee, any and all actions reasonably required to cause
the Pledge Agreement to create and maintain, as security for the obligations of
the Company under this Indenture and the Notes, valid and enforceable first
priority liens in and on all the Pledged Securities, in favor of the Trustee,
superior to and prior to the rights of third Persons and subject to no other
Liens.

                 (c)      The release of any Pledged Securities pursuant to the
Pledge Agreement will not be deemed to impair the security under this Indenture
in contravention of the provisions hereof if and to the extent the Pledged
Securities are released pursuant to this Indenture and the Pledge Agreement.
To the extent applicable, the Company shall cause TIA Section 314(d) relating
to the release of property or securities from the Lien and security interest of
the Pledge Agreement and relating to the substitution therefor of any property
or securities to be subjected to the Lien and security interest of the Pledge
Agreement to be complied with.  Any certificate or
<PAGE>   74
                                       68

opinion required by TIA Section 314(d) may be made by an officer of the
Company, except in cases where TIA Section 314(d) requires that such
certificate or opinion be made by an independent Person, which Person shall be
an independent engineer, appraiser or other expert selected by the Company.

                 (d)      The Company shall cause TIA Section 314(b), relating
to opinions of counsel regarding the Lien under the Pledge Agreement, to be
complied with. The Trustee may, to the extent permitted by Sections 7.01 and
7.02 hereof, accept as conclusive evidence of compliance with the foregoing
provisions the appropriate statements contained in such instruments.

                 (e)      The Trustee may, in its sole discretion and without
the consent of the Holders, on behalf of the Holders, take all actions it deems
necessary or appropriate in order to (i) enforce any of the terms of the Pledge
Agreement and (ii) collect and receive any and all amounts payable in respect
of the obligations of the Company thereunder. The Trustee shall have power to
institute and to maintain such suits and proceedings as the Trustee may deem
expedient to preserve or protect its interests and the interests of the Holders
in the Pledged Securities (including power to institute and maintain suits or
proceedings to restrain the enforcement of or compliance with any legislative
or other governmental enactment, rule or order that may be unconstitutional or
otherwise invalid if the enforcement of, or compliance with, such enactment,
rule or order would impair the security interest hereunder or be prejudicial to
the interests of the Holders or of the Trustee).


                                 ARTICLE ELEVEN
                                 MISCELLANEOUS

                 SECTION 11.01.  Trust Indenture Act of 1939.  This Indenture
is subject to the provisions of the TIA that are required to be a part of this
Indenture and shall, to the extent applicable, be governed by such provisions.

                 SECTION 11.02.  Notices.  Any notice or communication shall be
sufficiently given if in writing and delivered in person or mailed by first
class mail addressed as follows:

                 if to the Company:

                          Allegiance Telecom, Inc.
                          1950 Stemmons Frwy., Suite 3026
                          Dallas, Texas 75207
                          Attention:  Chief Financial Officer
<PAGE>   75
                                      69

                 if to the Trustee:

                          The Bank of New York
                          101 Barclay Street
                          Floor 21 West
                          New York, New York  10286
                          Attention:  Corporate Trust Administration

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

                 Any notice or communication mailed to a Holder shall be mailed
to him at his address as it appears on the Security Register by first class
mail and shall be sufficiently given to him if so mailed within the time
prescribed.  Copies of any such communication or notice to a Holder shall also
be mailed to the Trustee and each Agent at the same time.

                 Failure to mail a notice or communication to a Holder or any
defect in it shall not affect its sufficiency with respect to other Holders.
Except for a notice to the Trustee, which is deemed given only when received,
and except as otherwise provided in this Indenture, if a notice or
communication is mailed in the manner provided in this Section 11.02, it is
duly given, whether or not the addressee receives it.

                 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 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 11.03.  Certificate and Opinion as to Conditions
Precedent.  Upon any request or application by the Company to the Trustee to
take any action under this Indenture, the Company shall furnish to the Trustee:

                 (i)      an Officers' Certificate stating that, in the opinion
         of the signers, all conditions precedent, if any, provided for in this
         Indenture relating to the proposed action have been complied with; and
<PAGE>   76
                                       70

                 (ii)     an Opinion of Counsel in form and substance
         reasonably satisfactory to the Trustee stating that, in the opinion of
         such Counsel, all such conditions precedent have been complied with;
         provided, however, that, with respect to matters of fact, an Opinion
         of Counsel may rely on an Officers' Certificate or certificates of
         public officials.

                 SECTION 11.04.  Statements Required in Certificate.  Each
certificate with respect to compliance with a condition or covenant provided
for in this Indenture shall include:

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

                 (ii)     a brief statement as to the nature and scope of the
         examination or investigation upon which the statements contained in
         such certificate are based;

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

                 (iv)     a statement as to whether or not, in the opinion of
         each such person, such condition or covenant has been complied with.

                 SECTION 11.05.  Rules by Trustee, Paying Agent or Registrar.
The Trustee may make reasonable rules for action by or at a meeting of Holders.
The Paying Agent or Registrar may make reasonable rules for its functions.

                 SECTION 11.06.  Payment Date Other Than a Business Day.  If an
Interest Payment Date, Redemption Date, Payment Date, Stated Maturity or date
of maturity of any Note shall not be a Business Day, then payment of principal
of, premium, if any, or interest on such Note, as the case may be, need not be
made on such date, but may be made on the next succeeding Business Day with the
same force and effect as if made on the Interest Payment Date, Payment Date, or
Redemption Date, or at the Stated Maturity or date of maturity of such Note;
provided that no interest shall accrue for the period from and after such
Interest Payment Date, Payment Date, Redemption Date, Stated Maturity or date
of maturity, as the case may be.

                 SECTION 11.07.  Governing Law.  The laws of the State of New
York shall govern this Indenture and the Notes.  The Trustee, the Company and
the Holders agree to submit to the jurisdiction of the courts of the State of
New York in any action or proceeding arising out of or relating to this
Indenture or the Notes.

                 SECTION 11.08.  No Adverse Interpretation of Other Agreements.
This Indenture may not be used to interpret another indenture, loan or debt
agreement of the Company
<PAGE>   77
                                       71

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

                 SECTION 11.09.  No Recourse Against Others.  No recourse for
the payment of the principal of, premium, if any, or interest on any of the
Notes, 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
contained in this Indenture, or in any of the Notes, or because of the creation
of any Indebtedness represented thereby, shall be had against any incorporator
or against any past, present or future partner, shareholder, other
equityholder, officer, director, employee or controlling person, as such, of
the Company or of any successor Person, either directly or through the Company
or any successor Person, 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 Notes.

                 SECTION 11.10.  Successors.  All agreements of the Company in
this Indenture and the Notes shall bind its successors.  All agreements of the
Trustee in this Indenture shall bind its successor.

                 SECTION 11.11.  Duplicate Originals.  The parties may sign any
number of copies of this Indenture.  Each signed copy shall be an original, but
all of them together represent the same agreement.

                 SECTION 11.12.  Separability.  In case any provision in this
Indenture or in the Notes 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 11.13.  Table of Contents, Headings, Etc.  The Table
of Contents, Cross-Reference Table and headings of the Articles and Sections of
this Indenture have been inserted for convenience of reference only, are not to
be considered a part hereof and shall in no way modify or restrict any of the
terms and provisions hereof.
<PAGE>   78
                                   SIGNATURES

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


                                            ALLEGIANCE TELECOM, INC.


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



                                            THE BANK OF NEW YORK


                                            By:                               
                                               -------------------------------
                                               Name:
                                               Title:
<PAGE>   79
                                                                       EXHIBIT A


                                 [FACE OF NOTE]

                            ALLEGIANCE TELECOM, INC.

                         [     ]% Senior Note Due 2008

                                                                CUSIP __________


No.                                                                   $_________

                 ALLEGIANCE TELECOM, INC., a Delaware corporation (the
"Company", which term includes any successor under the Indenture hereinafter
referred to), for value received, promises to pay to ________________, or its
registered assigns, the principal sum of ___________________ ($______) on May
15, 2008.

                 Interest Payment Dates: May 15 and November 15, commencing
November 15, 1998.

                 Regular Record Dates: May 1 and November 1.

               Reference is hereby made to the further provisions of this Note
set forth on the reverse hereof, which further provisions shall for all
purposes have the same effect as if set forth at this place.
<PAGE>   80
               IN WITNESS WHEREOF, the Company has caused this Note to be
signed manually or by facsimile by its duly authorized officers.


                                             ALLEGIANCE TELECOM, INC.


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


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


                  (Trustee's Certificate of Authentication)

               This is one of the [       ]% Senior Notes due 2008 described 
in the within-mentioned Indenture.


Date:                                        THE BANK OF NEW YORK,
                                             as Trustee


                                             By:
                                                ------------------------------
                                                Authorized Signatory
<PAGE>   81
                                      A-3

                             [REVERSE SIDE OF NOTE]

                            ALLEGIANCE TELECOM, INC.

                          [    ]% Senior Note due 2008



1.  Principal and Interest.

                 The Company will pay the principal of this Note on May 15,
2008.

                 The Company promises to pay interest on the principal amount
of this Note on each Interest Payment Date, as set forth below, at the rate per
annum shown above.

                 Interest will be payable semiannually (to the holders of
record of the Notes at the close of business on the May 1 or November 1
immediately preceding the Interest Payment Date) on each Interest Payment Date,
commencing November 15, 1998.

                 Interest on the Notes will accrue from the most recent date to
which interest has been paid or, if no interest has been paid, from [
], 1998; provided that, if there is no existing default in the payment of
interest and this Note is authenticated between a Regular Record Date referred
to on the face hereof and the next succeeding Interest Payment Date, interest
shall accrue from such Interest Payment Date.  Interest will be computed on the
basis of a 360-day year of twelve 30-day months.

                 The Company shall pay interest on overdue principal and
premium, if any, and interest on overdue installments of interest, to the
extent lawful, at a rate per annum that is 2% in excess of the rate otherwise
payable.

2.  Method of Payment.

                 The Company will pay interest (except defaulted interest) on
the principal amount of the Notes as provided above on each May 15 and November
15 to the persons who are Holders (as reflected in the Security Register at the
close of business on such May 1 and November 1 immediately preceding the
Interest Payment Date), in each case, even if the Note is cancelled on
registration of transfer or registration of exchange after such record date;
provided that, with respect to the payment of principal, the Company will make
payment to the Holder that surrenders this Note to a Paying Agent on or after
May 15, 2008.

                 The Company will pay principal, premium, if any, and as
provided above, interest in money of the United States that at the time of
payment is legal tender for payment of public and
<PAGE>   82
                                      A-4

private debts.  However, the Company may pay principal, premium, if any, and
interest by its check payable in such money.  It may mail an interest check to
a Holder's registered address (as reflected in the Security Register).  If a
payment date is a date other than a Business Day at a place of payment, payment
may be made at that place on the next succeeding day that is a Business Day and
no interest shall accrue for the intervening period.

3.  Paying Agent and Registrar.

                 Initially, the Trustee will act as authenticating agent,
Paying Agent and Registrar.  The Company may change any authenticating agent,
Paying Agent or Registrar without notice.  The Company, any Subsidiary or any
Affiliate of any of them may act as Paying Agent, Registrar or co-Registrar.

4.  Indenture; Limitations.

                 The Company issued the Notes under an Indenture dated as of [
], 1998 (the "Indenture"), between the Company and The Bank of New York (the
"Trustee").  Capitalized terms herein are used as defined in the Indenture
unless otherwise indicated.  The terms of the Notes include those stated in the
Indenture and those made part of the Indenture by reference to the Trust
Indenture Act.  The Notes are subject to all such terms, and Holders are
referred to the Indenture and the Trust Indenture Act for a statement of all
such terms.  To the extent permitted by applicable law, in the event of any
inconsistency between the terms of this Note and the terms of the Indenture,
the terms of the Indenture shall control.

                 The Notes are general unsecured obligations of the Company.

                 The Company may, subject to Article Four of the Indenture and
applicable law, issue additional Notes under the Indenture.

5.  Redemption.

                 The Notes may be redeemed, at the Company's option, in whole
or in part, at any time or from time to time, on or after May 15, 2003 and
prior to maturity, upon not less than 30 nor more than 60 days' prior notice
mailed by first class mail to each Holder's last address as it appears in the
Security Register, at the Redemption Prices (expressed in percentages of
principal amount) set forth below, plus accrued and unpaid interest to the
Redemption Date (subject to the right of Holders of record on the relevant
Regular Record Date that is on or prior to the
<PAGE>   83
                                      A-5

Redemption Date to receive interest due on an Interest Payment Date), if
redeemed during the 12-month period commencing May 15 of the years set forth
below:

<TABLE>
<CAPTION>
                                                          Redemption
                          Year                              Price    
                          ----                            ----------
                          <S>                             <C>   
                          2003                            [     ]%
                          2004                            [     ]%
                          2005                            [     ]%
                          2006 and thereafter             100.000%
</TABLE>

                 In addition, at any time prior to May 15, 2001, the Company
may redeem up to 35% of the principal amount of the Notes originally issued
with the proceeds of one or more Public Equity Offerings following which there
is a Public Market, at any time or from time to time in part, at a Redemption
Price (expressed as a percentage of principal amount) of [            ]% plus
accrued and unpaid interest to the Redemption Date (subject to the right of
Holders of record on the relevant Regular Record Date that is on or prior to
the Redemption Date to receive interest due on an Interest Payment Date);
provided that at least 65% of the aggregate principal amount of Notes
originally issued remains outstanding after each such redemption and notice of
any such redemption is mailed within 60 days after the related Public Equity
Offering.

                 Notice of any optional redemption will be mailed at least 30
days but not more than 60 days before the Redemption Date to each Holder of
Notes to be redeemed at his last address as it appears in the Security
Register.  Notes in original denominations larger than $1,000 may be redeemed
in part.  On and after the Redemption Date, interest ceases to accrue on Notes
or portions of Notes called for redemption, unless the Company defaults in the
payment of the Redemption Price.

6.  Repurchase upon Change in Control.

                 Upon the occurrence of any Change of Control, each Holder
shall have the right to require the repurchase of its Notes by the Company in
cash pursuant to the offer described in the Indenture at a purchase price equal
to 101% of the principal amount thereof plus accrued interest, if any, to the
date of purchase (the "Change of Control Payment").

                 A notice of such Change of Control will be mailed within 30
days after any Change of Control occurs to each Holder at his last address as
it appears in the Security Register.  Notes in original denominations larger
than $1,000 may be sold to the Company in part.  On and after the Change of
Control Payment Date, interest ceases to accrue on Notes or portions of Notes
surrendered for purchase by the Company, unless the Company defaults in the
payment of the Change of Control Payment.
<PAGE>   84
                                      A-6

7.  Denominations; Transfer; Exchange.

                 The Notes are in registered form without coupons in
denominations of $1,000 of principal amount and multiples of $1,000 in excess
thereof.  A Holder may register the transfer or exchange of Notes in accordance
with the Indenture.  The Registrar may require a Holder, among other things, to
furnish appropriate endorsements and transfer documents and to pay any taxes
and fees required by law or permitted by the Indenture.  The Registrar need not
register the transfer or exchange of any Notes selected for redemption.  Also,
it need not register the transfer or exchange of any Notes for a period of 15
days before a selection of Notes to be redeemed is made.

8.  Persons Deemed Owners.

                 A Holder shall be treated as the owner of a Note for all
purposes.

9.  Unclaimed Money.

                 If money for the payment of principal, premium, if any, or
interest remains unclaimed for two years, the Trustee and the Paying Agent will
pay the money back to the Company at its request.  After that, Holders entitled
to the money must look to the Company for payment, unless an abandoned property
law designates another Person, and all liability of the Trustee and such Paying
Agent with respect to such money shall cease.

10.  Discharge Prior to Redemption or Maturity.

                 If the Company deposits with the Trustee money or U.S.
Government Obligations sufficient to pay the then outstanding principal of,
premium, if any, and accrued interest on the Notes (a) to redemption or
maturity, the Company will be discharged from the Indenture and the Notes,
except in certain circumstances for certain sections thereof, and (b) to the
Stated Maturity, the Company will be discharged from certain covenants set
forth in the Indenture.

11.  Amendment; Supplement; Waiver.

                 Subject to certain exceptions, the Indenture, the Pledge
Agreement or the Notes may be amended or supplemented with the consent of the
Holders of at least a majority in principal amount of the Notes then
outstanding, and any existing default or compliance with any provision may be
waived with the consent of the Holders of at least a majority in principal
amount of the Notes then outstanding.  Without notice to or the consent of any
Holder, the parties thereto may amend or supplement the Indenture or the Notes
to, among other things, cure any ambiguity, defect or inconsistency and make
any change that does not materially and adversely affect the rights of any
Holder.
<PAGE>   85
                                      A-7

12.  Restrictive Covenants.

                 The Indenture imposes certain limitations on the ability of
the Company and its Restricted Subsidiaries, among other things, to Incur
additional Indebtedness, make Restricted Payments, use the proceeds from Asset
Sales, engage in transactions with Affiliates or merge, consolidate or transfer
substantially all of its assets.  Within 45 days after the end of each fiscal
quarter (90 days after the end of the last fiscal quarter of each year), the
Company must report to the Trustee on compliance with such limitations.

13.  Successor Persons.

                 When a successor person or other entity assumes all the
obligations of its predecessor under the Notes and the Indenture, the
predecessor person will be released from those obligations.

14.  Defaults and Remedies.

                 The following events constitute "Events of Default" under the
Indenture:  (a) default in the payment of principal of (or premium, if any, on)
any Note when the same becomes due and payable, upon acceleration, redemption
or otherwise; (b) default in the payment of interest on any Note when the same
becomes due and payable, and such default continues for a period of 30 days;
provided that a failure to make any of the first six scheduled interest
payments on the Notes on the applicable Interest Payment Date will constitute
an Event of Default with no grace or cure period; (c) default in the
performance, or breach of the provisions of Article Five or the failure to make
or consummate an Offer to Purchase in accordance with Section 4.10 or Section
4.11; (d) default in the performance of or breach of any other covenant or
agreement of the Company in the Indenture or under the Notes (other than a
default specified in clause (a), (b) or (c) above) and such default or breach
continues for a period of 30 consecutive days after written notice by the
Trustee or the Holders of 25% or more in aggregate principal amount of the
Notes, (e) there occurs with respect to any issue or issues of Indebtedness of
the Company or any Significant Subsidiary having an outstanding principal
amount of $5 million or more in the aggregate for all such issues of all such
Persons, whether such Indebtedness now exists or shall hereafter be created,
(I) an event of default that has caused the holder thereof to declare such
Indebtedness to be due and payable prior to its Stated Maturity and such
Indebtedness has not been discharged in full or such acceleration has not been
rescinded or annulled within 30 days of such acceleration and/or (II) the
failure to make a principal payment at the final (but not any interim) fixed
maturity and such defaulted payment shall not have been made, waived or
extended within 30 days of such payment default; (f) any final judgment or
order (not covered by insurance) for the payment of money in excess of $5
million in the aggregate for all such final judgments or orders against all
such Persons (treating any deductibles, self-insurance or retention as not so
covered) shall be rendered against the Company or any Significant Subsidiary
and shall not be paid or discharged, and there shall be any period of 30
consecutive days following entry of the final judgment or order that causes the
aggregate amount for all such final judgments or orders outstanding and not
paid or discharged against all such Persons to exceed $5 million during which
<PAGE>   86
                                      A-8

a stay of enforcement of such final judgment or order, by reason of a pending
appeal or otherwise, shall not be in effect; (g) a court having jurisdiction in
the premises enters a decree or order for (A) relief in respect of the Company
or any Significant Subsidiary in an involuntary case under any applicable
bankruptcy, insolvency or other similar law now or hereafter in effect, (B)
appointment of a receiver, liquidator, assignee, custodian, trustee,
sequestrator or similar official of the Company or any Significant Subsidiary
or for all or substantially all of the property and assets of the Company or
any Significant Subsidiary or (C) the winding up or liquidation of the affairs
of the Company or any Significant Subsidiary and, in each case, such decree or
order shall remain unstayed and in effect for a period of 30 consecutive days;
(h) the Company or any Significant Subsidiary (A) commences a voluntary case
under any applicable bankruptcy, insolvency or other similar law now or
hereafter in effect, or consents to the entry of an order for relief in an
involuntary case under any such law, (B) consents to the appointment of or
taking possession by a receiver, liquidator, assignee, custodian, trustee,
sequestrator or similar official of the Company or any Significant Subsidiary
or for all or substantially all of the property and assets of the Company or
any Significant Subsidiary or (C) effects any general assignment for the
benefit of creditors; or (i) the Pledge agreement shall cease to be in full
force and effect or enforceable in accordance with its terms, other than in
accordance with its terms.

                 If an Event of Default (other than an Event of Default
specified in clauses (g) or (h) of Section 6.01 of the Indenture that occur
with respect to the Company) occurs and is continuing, the Trustee or the
Holders of at least 25% in principal amount of the Notes may declare all the
Notes to be due and payable.  If a bankruptcy or insolvency default with
respect to the Company occurs and is continuing, the Notes automatically become
due and payable.  Holders may not enforce the Indenture or the Notes except as
provided in the Indenture.  The Trustee may require indemnity satisfactory to
it before it enforces the Indenture or the Notes.  Subject to certain
limitations, Holders of at least a majority in principal amount of the Notes
then outstanding may direct the Trustee in its exercise of any trust or power.

15.  Security.

         The Company has entered into the Pledge Agreement and purchased and
pledged to the Trustee for the benefit of the Holders Pledged Securities in an
amount sufficient upon receipt of scheduled interest and principal payments on
such securities to provide for payment in full of the first six scheduled
interest payments due on the Notes.  The Pledged Securities will be pledged by
the Company to the Trustee for the benefit of the Holders and will be held by
the Trustee in the Pledge Account pending disbursement pursuant to the Pledge
Agreement.

16.  Trustee Dealings with Company.

                 The Trustee under the Indenture, in its individual or any
other capacity, may make loans to, accept deposits from and perform services
for the Company or its Affiliates and may otherwise deal with the Company or
its Affiliates as if it were not the Trustee.
<PAGE>   87
                                      A-9

17.  No Recourse Against Others.

                 No incorporator or any past, present or future partner,
shareholder, other equity holder, officer, director, employee or controlling
person as such, of the Company or of any successor Person shall have any
liability for any obligations of the Company under the Notes or the Indenture
or for any claim based on, in respect of or by reason of, such obligations or
their creation.  Each Holder by accepting a Note waives and releases all such
liability.  The waiver and release are part of the consideration for the
issuance of the Notes.

18.  Authentication.

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

19.  Abbreviations.

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

                 The Company will furnish to any Holder upon written request
and without charge a copy of the Indenture.  Requests may be made to Allegiance
Telecom, Inc., 1950 Stemmons Frwy., Suite 3026, Dallas, Texas 75207, Attention:
Chief Financial Officer.
<PAGE>   88
                                      A-10

                           [FORM OF TRANSFER NOTICE]


                 FOR VALUE RECEIVED the undersigned registered holder hereby
sell(s), assign(s) and transfer(s) unto

Insert Taxpayer Identification No.

--------------------------------------------------------------------------------
Please print or typewrite name and address including zip code of assignee

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the within Note and all rights thereunder, hereby irrevocably constituting and
appointing _______________________________ attorney to transfer said Note on the
books of the Company with full power of substitution in the premises.
<PAGE>   89
                                      A-11


                       OPTION OF HOLDER TO ELECT PURCHASE


                 If you wish to have this Note purchased by the Company
pursuant to Section 4.10 or Section 4.11 of the Indenture, check the Box:  [ ]

                 If you wish to have a portion of this Note purchased by the
Company pursuant to Section 4.10 or Section 4.11 of the Indenture, state the
amount (in principal amount):  $___________________.

Date:
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Your Signature:
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               (Sign exactly as your name appears on the other side 
               of this Note)

Signature Guarantee:
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