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                                                                   EXHIBIT 4.11





                           LIBERTY MEDIA CORPORATION

                                      AND

                              THE BANK OF NEW YORK

                                    Trustee

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

                         FOURTH SUPPLEMENTAL INDENTURE

                            Dated February 10, 2000

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

                          Supplementing the Indenture

                            Dated as of July 7, 1999

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

                 3 3/4% Senior Exchangeable Debentures Due 2030




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         FOURTH SUPPLEMENTAL INDENTURE, dated the 10th day of February, 2000,
between LIBERTY MEDIA CORPORATION, a corporation existing under the laws of the
State of Delaware (the "Company"), and THE BANK OF NEW YORK, a New York banking
corporation, having its principal corporate trust office in The City of New
York, New York, as trustee (the "Trustee").

         WHEREAS, the Company has heretofore executed and delivered to the
Trustee an Indenture dated as of July 7, 1999 (the "Original Indenture" and, as
supplemented to the date hereof, the "Indenture"), providing for the issuance
by the Company from time to time of its senior debt securities to be issued in
one or more series (in the Original Indenture and herein called the
"Securities");

         WHEREAS, the Company, in the exercise of the power and authority
conferred upon and reserved to it under the provisions of the Original
Indenture and pursuant to appropriate resolutions of the Board of Directors,
has duly determined to make, execute and deliver to the Trustee this Fourth
Supplemental Indenture to the Original Indenture in order to establish the form
and terms of, and to provide for the creation and issue of, a series of
Securities designated as the "3 3/4% Senior Exchangeable Debentures due 2030"
under the Original Indenture in an aggregate principal amount of up to
$1,000,000,000 (the "Debentures");

         WHEREAS, Section 901 of the Original Indenture provides, among other
things, that the Company, when authorized by a Board Resolution, and the
Trustee, at any time and from time to time, without the consent of any Holders,
may enter into an indenture supplemental to the Original Indenture to establish
the terms of Securities of any series as permitted by Sections 201 and 301 of
the Original Indenture; and

         WHEREAS, all things necessary to make the Securities, when executed by
the Company and authenticated and delivered by the Trustee or any
Authenticating Agent and issued upon the terms and subject to the conditions
hereinafter and in the Indenture set forth against payment therefor, the valid,
binding and legal obligations of the Company and to make this Fourth
Supplemental Indenture a valid, binding and legal agreement of the Company,
have been done.

         NOW, THEREFORE, THIS FOURTH SUPPLEMENTAL INDENTURE WITNESSETH that, in
order to establish the terms of the series of Securities designated as the

"3 3/4% Senior Exchangeable Debentures due 2030," and for and in consideration
of the premises and of the covenants contained in the Original Indenture and in
this Fourth Supplemental Indenture and for other good and valuable consideration
the receipt and sufficiency of which are hereby acknowledged, it is mutually
covenanted and agreed as follows:





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                                  ARTICLE ONE

                             DEFINITIONS AND OTHER
                       PROVISIONS OF GENERAL APPLICATION


         Section  101. Definitions.

         Each capitalized term that is used herein and is defined in the
Original Indenture shall have the meaning specified in the Original Indenture
unless such term is otherwise defined herein, in which case such term shall
have the meaning specified herein.

         "Additional Distribution" shall mean any distribution to Holders of
the Debentures made pursuant to Section 206 as a result of a Reference Share
Distribution.

         "Adjusted Principal Amount" shall mean, for each $1,000 Original
Principal Amount of the Debentures, $1,000, minus any and all Extraordinary
Additional Distributions and any Yield Adjustments made in respect to such
Original Principal Amount of Debentures pursuant to Section 204.

         "Average Transaction Consideration" shall mean, with respect to a
holder of one Reference Share in a Reference Share Offer, (a) the aggregate
consideration actually paid or distributed in respect of all Reference Shares
accepted in such Reference Share Offer, divided by (b) the total number of
Reference Shares outstanding immediately prior to the expiration of the
Reference Share Offer and entitled to participate in such Reference Share
Offer.

         "Borrow Cost Period" shall mean the period beginning on May 15, 2000
and ending on February 15, 2004.

         "Business Day" shall mean any day that is not a Saturday, Sunday or
legal holiday, on which banking institutions or trust companies in The City of
New York are authorized or obligated by law or regulation to close.

         "Closing Price" shall mean, with respect to any security on any date
of determination, the closing sale price (or, if no closing sale price is
reported, the last reported sale price) of that security (regular way) on the
New York Stock Exchange on that date or, if the security is not listed for
trading on the New York Stock Exchange on that date, as reported in the
composite transactions for the principal United States national or regional
securities exchange on which the security is so listed, or if the security is
not so listed on a United States national or regional securities exchange, as
reported by the Nasdaq National Market or, if the security is not so reported,
the last quoted bid price for the security in the over-the-counter market as
reported by the National Quotation Bureau or a similar organization. In the
event that no such quotation is available for that day, the Board of Directors
will be entitled to determine the Closing Price on the basis of those
quotations that it in good faith considers appropriate, unless "Closing Price"
is to be determined for purposes of valuing securities to be distributed
pursuant to a Reference Share Distribution and such securities have an
aggregate value in excess of $100,000,000, in which event the Closing Price
will be determined by a nationally recognized investment banking or appraisal
firm appointed by the Company for such purpose. With respect to options,
warrants and other rights to purchase a security, the Closing Price shall be
the value of the underlying



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security determined as aforesaid, minus the exercise price; and with respect to
securities exchangeable for or convertible into a relevant security, the
Closing Price shall be the Closing Price of the exchangeable or convertible
security determined as aforesaid or, if it has no Closing Price, the fully
converted value based upon the Closing Price of the underlying security
determined as aforesaid. If an "ex-dividend" date for a security occurs during
the period used in determining the security's Current Market Value or Exchange
Market Value, the Closing Price of the security on any day prior to the
"ex-dividend" date used in such determination shall be reduced by the amount of
the dividend. For this purpose, the amount of a non-cash dividend will be equal
to the amount of the dividend, as of the record date therefor, as determined by
a nationally recognized investment banking firm retained by the Company for
this purpose. To the extent that trading (regular way) of, or quotations for,
any security as to which "Closing Price" is to be determined continues past
4:00 p.m., New York City time, on the applicable securities exchange, the
National Market System or over-the-counter market, as the case may be, "Closing
Price" shall be deemed to refer to the price or bid at the time that is then
customary for determining the trading day's index levels for stocks traded on
such securities exchange, the National Market System or over-the-counter
market.

         "Common Equity Securities" shall mean any securities (i) that are
common stock or participate without limitation in earnings and dividends in
parity with common stock and (ii) that are Marketable Securities. For greater
certainty, the term "Common Equity Securities" does not mean warrants, options
or other rights to purchase, or securities exchangeable or convertible into,
Common Equity Securities.

         "Company" shall mean the Person named as the "Company" in the first
paragraph of this instrument until a successor Person shall have become such
pursuant to the applicable provisions of the Indenture, and thereafter
"Company" shall mean such successor Person, and any other obligor upon the
Debentures.

         "Current Market Value" shall mean, with respect to any Reference
Share, the average of the Closing Prices for such Reference Share over the 20
Trading Day period immediately prior to (but not including) the fifth Trading
Day preceding the applicable Redemption Date (or, in the case of Section
204(b), Stated Maturity).

         "Debenture" shall mean $1,000 Original Principal Amount of the
Debentures.

         "Debentures" shall mean the Company's 3 3/4% Senior Exchangeable
Debentures due 2030.

         "Depository" shall have the meaning assigned to it in the Original
Indenture.

         "Determination Agent" shall mean Salomon Smith Barney Inc. or any
successor designated by the Company.

         "DTC" shall mean The Depository Trust Company.

         "Excess Borrow Cost" shall mean the determination by the Determination
Agent that, for any Trading Day, (i) the weighted average rebate paid on cash
collateral posted to borrow Reference Shares from the Determination Agent, as
principal or agent, is less than 200 basis



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points below the Federal Funds Rate and (ii) the Determination Agent is not
able to effectively lend Reference Shares to beneficial owners of the
Debentures for a rebate that is not less than 200 basis points below the
Federal Funds Rate.

         "Excess Borrow Cost Period" shall mean each quarter ending February
15, May 15, August 15 or November 15, during the Borrow Cost Period, in which
the Determination Agent determines that Excess Borrow Costs exist for 20 or
more Trading Days in such quarter.

         "Excess Borrow Cost Redemption" shall mean the redemption of the
Debentures pursuant to Section 208(d) following the occurrence of an Excess
Borrow Cost Period.

         "Exchange Agent" shall mean any Person authorized by the Company to
act as Exchange Agent under the Indenture. The Company initially authorizes the
Trustee to act as Exchange Agent for the Debentures on its behalf. The Company
may at any time and from time to time authorize one or more Persons (including
the Company) to act as Exchange Agent in addition to or in place of the Trustee
with respect to the Debentures.

         "Exchange Date" shall mean, with respect to any Notice of Exchange,
the date on which the Notice of Exchange and all documents, instruments and
payments required to be tendered in connection with the related exchange have
been received by the Exchange Agent.

         "Exchange Market Value" shall mean, for each Reference Share
attributable to the Debentures at the date of determination, (a) in the case of
a Notice of Exchange delivered to the Exchange Agent prior to February 15,
2001, the Closing Price for such Reference Share on the twentieth Trading Day
following the Exchange Date (unless more than $1,000,000 aggregate Original
Principal Amount of Debentures have been validly tendered for exchange on such
date, in which case Exchange Market Value shall mean the average of the Closing
Prices for such Reference Share over the five Trading Day period ending on the
twentieth Trading Day immediately following the Exchange Date); and (b) in the
case of a Notice of Exchange delivered to the Exchange Agent on or after
February 15, 2001, the Closing Price for such Reference Share on the Trading
Day following the Exchange Date (unless more than $1,000,000 aggregate Original
Principal Amount of Debentures have been validly tendered for exchange on such
date, in which case the Exchange Market Value shall mean the average of the
Closing Prices for such Reference Share over the five Trading Day period
immediately following the Exchange Date). The aggregate Exchange Market Value
of the Reference Shares attributable to any Debenture for which a Notice of
Exchange is delivered to the Trustee shall equal the sum of the Exchange Market
Values of the Reference Shares attributable to such Debenture.

         "Extraordinary Additional Distribution" shall mean any Additional
Distribution other than a Regular Additional Distribution, whether of cash or
property; provided that in the event of a Reference Share Offer, the amount of
the Extraordinary Additional Distribution on each Debenture in respect of such
Reference Share Offer shall equal the portion of the Average Transaction
Consideration deemed to be received on the Reference Shares of the class or
series subject to the Reference Share Offer attributable to such Debenture
(immediately prior to giving effect to the Reference Share Proportionate
Reduction relating to that Reference Share Offer) other than the portion of the
Average Transaction Consideration that consists of Common Equity



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Securities, which themselves become part of the Reference Shares as a result of
the Reference Share Offer Adjustment.

         "Extraordinary Distribution" shall mean any Reference Share
Distribution other than a Regular Cash Dividend.

         "Federal Funds Rate," for any date of determination, shall mean:

         (1)      the rate on the applicable date for United States dollar
                  federal funds as published in H.15(519) under the caption
                  "Federal Funds (Effective)" as displayed on Bridge Telerate,
                  Inc. or any successor service on page 120 or any other page
                  as may replace the applicable page on that service ("Telerate
                  Page 120"); or

         (2)      if the rate referred to in clause (1) does not appear on
                  Telerate Page 120 or is not so published by 3:00 P.M., New
                  York City time, on the applicable date, the rate on the
                  applicable date for United States dollar federal funds as
                  published in H.15 Daily Update, or other recognized
                  electronic source used for the purpose of displaying the
                  applicable rate, under the caption "Federal Funds/Effective
                  Rate;" or

         (3)      if the rate referred to in clause (2) is not published by
                  3:00 P.M., New York City time, on the applicable date, the
                  rate on the applicable date calculated by the determination
                  agent as the arithmetic mean of the rates for the last
                  transaction in overnight United States dollar federal funds
                  arranged by three leading brokers of United States dollar
                  federal funds transactions in The City of New York, selected
                  by the Determination Agent before 9:00 A.M., New York City
                  time, on the Trading Day immediately following the applicable
                  date; or

         (4)      if the brokers selected by the Determination Agent are not
                  quoting as mentioned in clause (3), the rate in effect on the
                  most recent preceding date for which a rate may be determined
                  in accordance with the foregoing.

         "Final Period Distribution" shall mean, for each Debenture, (a) all
Regular Cash Dividends on any Reference Shares attributable to such Debenture
for which the ex-dividend date has occurred but which, at the date of
determination, have not been received by the holders of such Reference Shares
and (b) all Extraordinary Distributions on any Reference Shares attributable to
such Debenture for which the ex-dividend date has occurred but which, at the
date of determination, have not been received by the holders of such Reference
Shares, but only to the extent that the value of such Extraordinary
Distributions (determined in accordance with Section 206(d) or (e)) exceeds the
Adjusted Principal Amount of such Debenture.

         "H.15 Daily Update" shall mean the daily update of H.15(519),
available through the world-wide-web site of the Board of Governors of the
Federal Reserve System at http://www.bog.frb.fed.us/releases/h15/update, or any
successor site or publication.

         "H.15(519)" shall mean the weekly statistical release designated as
H.15(519), or any successor publication, published by the Board of Governors of
the Federal Reserve System.




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         "Initial Purchaser" shall mean Salomon Smith Barney Inc.

         "Interest Payment Date" shall have the meaning assigned to it in
Section 205.

         "Maturity Repayment Amount" shall have the meaning assigned to it in
the form of Debenture attached hereto as Exhibit A.

         "Notice of Exchange" shall mean the notice of exchange given to the
Exchange Agent by a Holder of its request to exchange Debentures pursuant to
Section 209(c).

         "Optional Redemption" shall mean any redemption of the Debentures, in
whole or in part, at the option of the Company pursuant to Section 208(a).

         "Original Principal Amount" shall mean the face value of $1,000
principal amount per Debenture.

         "Permanent Regulation S Debenture" shall have the meaning assigned to
it in Section 213(c).

         "Premium Adjustment" shall mean the factor by which the Exchange
Market Value or the Current Market Value of the Reference Shares attributable
to a Debenture, as the case may be, is to be multiplied pursuant to Section
218(a). The initial Premium Adjustment shall equal a factor of 1.00625, and
each additional Premium Adjustment shall increase such factor by an additional
 .00625. For greater certainty, and by way of example, two Premium Adjustments
would require the Exchange Market Value or the Current Market Value of the
Reference Shares attributable to a Debenture, as the case may be, to be
multiplied by a factor of 1.0125.

         "Reference Company" shall mean Sprint Corporation, for so long as any
Reference Shares are Sprint PCS Stock, and any other issuer of a Reference
Share.

         "Reference Share" shall initially mean one share of Sprint PCS Stock;
and after the date hereof shall mean and include each share or fraction of a
share of Common Equity Securities received by a holder of a Reference Share in
respect of that Reference Share, and, to the extent the Reference Share remains
outstanding after any of the following events but without duplication,
including the Reference Share outstanding immediately prior thereto, in each
case directly or as the result of successive applications of this paragraph
upon any of the following events: (i) a distribution on or in respect of a
Reference Share, made in Reference Shares; (ii) the combination of a Reference
Share into a smaller number of shares or other units; (iii) the subdivision of
outstanding shares or other units of a Reference Share; (iv) the conversion or
reclassification of Reference Shares by issuance or exchange of other Common
Equity Securities; (v) any Common Equity Securities issued for a Reference
Share in any consolidation or merger of a Reference Company, or any surviving
entity or subsequent surviving entity of a Reference Company (referred to
herein as a "Reference Company Successor"), with or into another entity (other
than any Common Equity Securities issued in connection with (A) a Reference
Share Offer or (B) a merger or consolidation in which (x) the Reference Company
is the continuing corporation and in which the Reference Shares outstanding
immediately prior to the merger or consolidation are not exchanged for cash,
securities or other property of the



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Reference Company or another corporation or (y) an election is given as to the
consideration to be received by a holder of Reference Shares); (vi) any Common
Equity Securities issued in exchange for a Reference Share in any statutory
exchange of securities of a Reference Company or any Reference Company
Successor with another corporation (other than any Common Equity Securities
issued in connection with (A) a Reference Share Offer or (B) a statutory
exchange of securities in which (x) the Reference Company is the continuing
corporation and in which the Reference Shares outstanding immediately prior to
the statutory exchange are not exchanged for cash, securities or other property
of the Reference Company or another corporation or (y) an election is given as
to the consideration to be received by a holder of Reference Shares); (vii) any
Common Equity Securities issued with respect to a Reference Share in connection
with any liquidation, dissolution or winding up of the Reference Company or any
Reference Company Successor; and (viii) any Common Equity Securities received
in exchange for a Reference Share as part of the Average Transaction
Consideration deemed received in any Reference Share Offer. For purposes of
this definition, (I) a conversion or redemption by Sprint Corporation of all
shares of Sprint PCS Stock pursuant to Article Sixth, Section 7.1 of its
Articles of Incorporation shall be deemed a consolidation or merger; and (II) a
redemption by Sprint Corporation pursuant to Article Sixth, Section 7.2 of its
Articles of Incorporation of all of the outstanding shares of Sprint PCS Stock
in exchange for common stock of one or more wholly-owned subsidiaries that
collectively hold all of the assets and liabilities attributed to its PCS Group
shall be deemed a statutory exchange of shares of Sprint PCS Stock for shares
of common stock of the relevant subsidiary or subsidiaries; provided, however,
that if there is an election given to holders of Sprint PCS Stock in connection
with any such conversion or redemption, the transaction shall be deemed a
Reference Share Offer.

         "Reference Share Distribution" shall mean any dividend or distribution
on or in respect of the Reference Shares, including payments and distributions
in connection with (i) the consolidation or merger of a Reference Company or
Reference Company Successor, a statutory exchange of securities of a Reference
Company or Reference Company Successor or a liquidation or dissolution of a
Reference Company or Reference Company Successor or (ii) any Reference Share
Offer, but shall not include any dividend or distribution made in the form of
additional Reference Shares.

         "Reference Shares Eligibility Date" shall mean the later of (i)
February 15, 2002, and (ii) the date on which an Officers' Certificate is
delivered to the Trustee which certifies that the Company and the Trust, taken
together, no longer have a direct or indirect ownership interest of 10% or more
of the outstanding shares of any class or series of Reference Shares that are
equity securities registered under the Securities Exchange Act, assuming the
exercise and conversion by the Company and the Trust (but not by any other
holder) of all securities that are convertible into, or exchangeable or
exercisable for, shares or such class or series (but without regard to any
restriction or limitation on the conversion, exchange or exercise thereof). The
Company shall issue a press release announcing the Reference Shares Eligibility
Date, and provide it to DTC for dissemination through the DTC broadcast
facility.

         "Reference Share Offer" shall mean any tender offer or exchange offer
made for 30% or more of the outstanding shares of a class or series of
Reference Shares of a Reference Company or any consolidation, merger or
statutory exchange involving a class or series of Reference Shares of a
Reference Company in which an election is given to holders of such Reference






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Shares as to the consideration to be received in the transaction. A "Reference
Share Offer" shall include a conversion or redemption by Sprint Corporation of
less than all shares of Sprint PCS stock pursuant to Article Sixth, Section 7.1
of its Articles of Incorporation or any conversion or redemption by Sprint
Corporation of all shares of Sprint PCS Stock pursuant to Article Sixth,
Section 7.1 or Section 7.2 of its Articles of Incorporation in which a holder
of Sprint PCS Stock is given an election as to the consideration that he or she
may receive.

         "Reference Share Offer Adjustment" shall mean (a) an adjustment to the
Reference Shares attributable to each Debenture to include the portion of the
Average Transaction Consideration received in a Reference Share Offer that
consists of Reference Shares, and (b) a reduction in the number of Reference
Shares attributable to each Debenture prior to such Reference Share Offer by
the Reference Share Proportionate Reduction.

         "Reference Share Proportionate Reduction" shall mean a proportionate
reduction in the number of Reference Shares which are the subject of the
applicable Reference Share Offer and attributable to each Debenture, calculated
in accordance with the following formula:

                                         X
                                    R = ---
                                         N

where:

         R =      the fraction by which the number of Reference Shares of the
                  class or series of Reference Shares subject to the Reference
                  Share Offer and attributable to each Debenture will be
                  reduced;

         X =      the aggregate number of Reference Shares of the class or
                  series of Reference Shares subject to the Reference Share
                  Offer accepted in the Reference Share Offer; and

         N =      the aggregate number of Reference Shares of the class or
                  series of Reference Shares subject to the Reference Share
                  Offer outstanding immediately prior to the expiration of the
                  Reference Share Offer.

         "Registration Default" shall mean either (a) the Shelf Registration
Statement is not filed with the Securities and Exchange Commission on or prior
to the 90th calendar day following the date of original issuance of the
Debentures or (b) such Shelf Registration Statement has not been declared
effective on or prior to the 180th calendar day following the date of original
issuance of the Debentures.

         "Registration Rights Agreement" shall mean the Registration Rights
Agreement, dated as of February 10, 2000, among the Company and the Initial
Purchaser.

         "Registration Suspension" shall mean any period of more than an
aggregate of 30 calendar days in any consecutive twelve-month period, occurring
after the Shelf Registration Statement has been declared effective, during
which such Shelf Registration Statement is not usable as contemplated by the
Registration Rights Agreement.




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         "Regular Additional Distribution" shall mean any Additional
Distribution as a result of a Reference Share Distribution that consists of a
Regular Cash Dividend.

         "Regular Cash Dividend" shall mean any cash dividend declared by a
Reference Company on its Reference Shares in accordance with the Reference
Company's publicly announced regular common equity dividend policy.

         "Regulation S" shall mean Regulation S under the Securities Act.

         "Restricted Period" shall have the meaning assigned to it in Section
207.

         "Rule 144A" shall mean Rule 144A under the Securities Act, as such
rule may be amended from time to time.

         "Rule 144A Debentures" shall have the meaning assigned to it in
Section 215.

         "Securities Act" shall mean the United States Securities Act of 1933,
as amended.

         "Securities Exchange Act" shall mean the United States Securities
Exchange Act of 1934, as amended.

         "Share Event" shall mean that the Trustee shall have received an
Officers' Certificate which states that the Trust no longer holds the entire
pecuniary interest in an amount of Sprint PCS Stock or securities convertible
or exercisable therefor, or in Reference Shares received by the trustee of the
Trust for such securities, free and clear of any rights or other claims of
others, including rights or claims relating to the market value of such
securities, that are equal to or greater than the aggregate amount of Reference
Shares attributable to all Debentures then outstanding; provided, however, that
a Share Event shall not be deemed to have occurred if the Trust no longer holds
the prescribed securities by reason of its transfer of such securities to or
upon the order of the Company.

         "Share Event Redemption" shall mean the redemption of the Debentures
pursuant to Section 208(c) following the occurrence of a Share Event.

         "Shelf Registration Statement" shall mean the registration statement
required to be filed by the Company pursuant to the Registration Rights
Agreement.

         "Special Payment Adjustment" shall mean each special interest payment
on a Debenture in an amount equal to 0.625% of the Original Principal Amount of
each Debenture.

         "Sprint Corporation" shall mean Sprint Corporation, a Kansas
corporation.

         "Sprint PCS Stock" shall mean the Sprint Corporation PCS common
stock-Series 1, par value $1.00 per share.

         "Tax Event" shall mean that the Trustee shall have received an opinion
of nationally recognized independent tax counsel experienced in such matters to
the effect that as a result of (a) any amendment to, clarification of, or
change in the laws, or any regulations thereunder, of




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the United States or any political subdivision or taxing authority thereof or
therein, or (b) any judicial decision, official administrative pronouncement,
ruling, regulatory procedure, notice or announcement, including any
announcement of proposed procedures or regulations, in each case, on or after
February 3, 2000 (a "change in tax law"), there is the creation by such change
in tax law of a substantial risk that, pursuant to Section 263(g) of the
Internal Revenue Code, the Company will not be able to deduct all of the
interest (including original issue discount) paid or accrued with respect to
the Debentures in calculating its U.S. federal income tax liability.

         "Tax Event Redemption" shall mean the redemption of the Debentures
pursuant to Section 208(b) following the occurrence of a Tax Event.

         "Temporary Regulation S Debenture" shall have the meaning assigned to
it in Section 213(c).

         "Trading Day" shall mean (i) where the Closing Price of a security is
to be determined, a day on which the security (a) is not suspended from trading
or quotation at the close of business on the national or regional securities
exchange, the National Market System or over-the-counter market that is the
primary market for the trading or quotation of that security and (b) has traded
or been quoted at least once on the national or regional securities exchange,
the National Market System or over-the-counter market that is the primary
market for the trading or quotation of that security and (ii), for any other
purpose under this Fourth Supplemental Indenture, any day on which the Nasdaq
National Market and the New York Stock Exchange are open for the transaction of
business.

         "Trust" shall mean the Liberty PCS Trust created by that certain trust
agreement, entered into as of March 9, 1999, between TCI Wireless Holdings,
Inc., as grantor, and M. LaVoy Robison, as trustee, as the same may be amended
from time to time.

         "Yield Adjustment" shall mean any adjustment required to be made to
the Adjusted Principal Amount on any Interest Payment Date following any
Extraordinary Additional Distribution (except for the Interest Payment Date
immediately following such Extraordinary Additional Distribution) so that the
interest payment on such Interest Payment Date does not represent an annualized
yield in excess of 3 3/4% on the Adjusted Principal Amount (exclusive of any
Special Payment Adjustment) of the Debentures during the semi-annual period
immediately preceding such Interest Payment Date.

         Section 102.  Section References.

         Each reference to a particular section set forth in this Fourth
Supplemental Indenture shall, unless the context otherwise requires, refer to
this Fourth Supplemental Indenture.

         Section 103.  Conflict with Original Indenture.

         To the extent that any of the terms set forth in this Fourth
Supplemental Indenture or the certificates representing the Debentures shall
conflict with any of the terms of the Original Indenture, the terms of this
Fourth Supplemental Indenture and the certificates representing the Debentures
shall be controlling with respect to the Debentures.





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                                  ARTICLE TWO

                       TITLE AND TERMS OF THE SECURITIES


         Section  201. Title of the Securities.

         The title of the Securities of the series established hereby is the

"3 3/4% Senior Exchangeable Debentures due 2030".

         Section  202. Amount and Denominations.

         The aggregate Original Principal Amount of the Debentures which may be
authenticated and delivered under the Indenture is initially limited to
$1,000,000,000, except for Debentures authenticated and delivered upon
registration of transfer of, or in exchange for, or in lieu of, other
Debentures pursuant to Section 304, 305, 306, 904 or 1107 of the Original
Indenture; provided, however, that the series of Securities established hereby
may be reopened, without the consent of the Holders of Outstanding Debentures,
for issuance of additional Debentures.

         Section  203. Registered Securities.

         The certificates for the Debentures shall be Registered Securities and
shall be in substantially the forms attached hereto as Exhibits A-1, A-2 or
A-3, and shall bear the legends as are inscribed thereon.

         Section  204. Stated Maturity; Changes to Original Principal Amount or
Adjusted Principal Amount.

         (a)      The Stated Maturity of the principal of the Debentures shall
be February 15, 2030.

         (b)      Not less than 30 Business Days prior to the Stated Maturity
of the principal of the Debentures, the Company shall issue a press release and
provide it to DTC for dissemination through the DTC broadcast facility, as to
whether or not the Company will deliver, or cause to be delivered, Reference
Shares in exchange for any Debentures submitted for exchange, in accordance
with Section 209, from the date of such notice through 5:00 p.m., New York City
time, on the Trading Day next preceding such Stated Maturity. If Reference
Shares are to be delivered in connection with any such exchange, Debentures
validly exchanged during that period, in accordance with Section 209, will be
exchanged for the Reference Shares attributable to such Debentures, and the
Company shall pay at Stated Maturity to Holders that do not exchange their
Debentures an amount, in cash, determined in the same manner as the Redemption
Price is determined in Section 208(a)(ii) (substituting the term "Stated
Maturity" for "Redemption Date" therein), in full payment for such Debentures.
If Reference Shares are not to be delivered in connection with any such
exchange, the exchange right set forth in Section 209 will terminate as of the
30th Business Day prior to the Stated Maturity of the principal of the
Debentures and the Company shall pay at Stated Maturity to Holders of
Debentures an amount, in cash, determined in the same manner as the Redemption
Price is determined in Section 208(a)(i)(B) (substituting the term "Stated
Maturity" for "Redemption Date" therein), in full payment for such Debentures.
Any notice by the Company as to whether or not it will deliver Reference Shares
in exchange for Debentures pursuant to this Section 204(b) shall be
irrevocable.


                                      10
<PAGE>   13


         (c)      The principal amount of each Debenture shall initially equal
the Original Principal Amount. Thereafter, the principal amount of each
Debenture, as of any date of determination, shall equal the Adjusted Principal
Amount. In calculating the Adjusted Principal Amount, (i) the value of any
Extraordinary Additional Distribution shall be subtracted as of the date it is
distributed to holders of the Debentures, and (ii) the amount of each Yield
Adjustment shall be subtracted on the Interest Payment Date to which such Yield
Adjustment relates. In no event will the Adjusted Principal Amount be less than
zero. The Company shall issue a press release upon the occurrence of each
reduction to the Adjusted Principal Amount, and provide it to DTC for
dissemination through the DTC broadcast facility.

         (d)      At least five Business Days prior to the Stated Maturity of
the principal of Debentures, the Company shall deliver an Officers' Certificate
to the Trustee which: (i) sets forth the amount to be paid in accordance with
Section 204(b) at such Stated Maturity for each Debenture and for all
Debentures then Outstanding, (ii) sets forth a reasonably detailed calculation
of such amounts, and (iii) directs the Trustee to adjust its records
accordingly and to request the Depository to adjust its records accordingly. At
or prior to 10:00 a.m., New York City time, on the date of Stated Maturity of
the principal of the Debentures, the Company shall deposit with the Trustee or
with a Paying Agent (or, if the Company is acting as its own Paying Agent,
segregate and hold in trust as provided in Section 1003 of the Original
Indenture) an amount in cash sufficient to pay, in accordance with Section
204(b), the amount due on all Debentures that are Outstanding at 5:00 p.m., New
York City time, on the date of such Stated Maturity.

         (e)      In the event of an acceleration of maturity of the Debentures
pursuant to Section 502 of the Original Indenture, there shall become
immediately due and payable an amount equal to the sum of (1) the greater of
(a) the Adjusted Principal Amount of the Debentures then Outstanding and (b)
the Current Market Value of the Reference Shares attributable to the
Debentures, (2) any accrued and unpaid interest on the Debentures, (3) the
amount of any payment required to made pursuant to Section 218 in respect of
any Special Payment Adjustment and (4), subject to Section 211, any Final
Period Distribution on the Debentures, determined as if (i) in the case of an
Event of Default specified in clause (8) or (9) of Section 501 of the Original
Indenture (as supplemented by Section 217(c) hereof), the date of such Event of
Default were the Stated Maturity of the principal of the Debentures and (ii) in
the case of any other Event of Default, the date of declaration of acceleration
were the Stated Maturity of the principal of the Debentures.

         Section  205. Interest.

         (a)      The Debentures shall bear interest from February 10, 2000 or
from the most recent Interest Payment Date to which interest has been paid or
provided for, payable semiannually on February 15 and August 15 of each year
(each, an "Interest Payment Date"), commencing August 15, 2000, to the Persons
in whose names the Debentures (or one or more Predecessor Securities) are
registered at the close of business on the February 1 or August 1 immediately
preceding such Interest Payment Date. Calculations of interest on each
Debenture




                                      11
<PAGE>   14




shall be based on the Original Principal Amount, without regard to changes in
the Adjusted Principal Amount. Interest on the Debentures shall be computed on
the basis of a 360-day year of twelve 30-day months. The amount of interest
payable on the Debentures on the initial Interest Payment Date shall be
computed on the basis of six 30-day months and an additional five days.

         (b)      Interest on the Debentures will accrue at the rate of 3 3/4%
per annum until the principal thereof is paid or made available for payment;
provided, however, that such interest rate shall be subject to increase as
follows:

                  (i) the interest rate shall be increased ("Additional
         Interest") by one quarter of one percent (0.25%) per annum upon the
         occurrence of each Registration Default or Registration Suspension,
         which rate will increase by one quarter of one percent (0.25%) at the
         beginning of each 90-day period (or portion thereof) that such
         Additional Interest continues to accrue under any such circumstance,
         provided that the maximum amount of Additional Interest will in no
         event exceed one percent (1%) per annum. Immediately following the
         cure of a Registration Default, the accrual of Additional Interest
         with respect to such Registration Default will cease;

                  (ii) accrual of Additional Interest will cease and the
         interest rate will revert to the original rate, in the case of a
         Registration Default, upon the earlier to occur of (A) the cure of all
         Registration Defaults or (B) the date on which the Debentures are
         saleable pursuant to Rule 144(k) under the Securities Act or any
         successor provision; and in the case of a Registration Suspension,
         upon the Shelf Registration Statement once again becoming usable as
         contemplated under the Registration Rights Agreement;

                  (iii) Additional Interest shall accrue from and including the
         day following the applicable Event Date (as defined below), and shall
         be computed based on the actual number of days elapsed in each 90-day
         period; and

                  (iv) the Company shall deliver to the Trustee an Officers'
         Certificate within three Business Days after each and every date on
         which an event occurs in respect of which Additional Interest is
         required to be paid (an "Event Date").

         (c)      At least five Business Days prior to each Interest Payment
Date, the Company shall deliver an Officers' Certificate to the Trustee setting
forth: (i) the amount of interest per Debenture due for that interest period,
(ii) the amount of any payment required to be made under Section 206(b) in
respect of any Regular Cash Dividends, (iii) the amount of any payment required
to be made pursuant to Section 218 in respect of any Special Payment Adjustment
and (iv) the total payment due for that period on all Debentures outstanding.

         Section  206. Additional Distributions.

         (a)      The Company shall distribute, or cause to be distributed, as
an Additional Distribution to all Holders of Debentures, any Reference Share
Distribution received by holders of Reference Shares, or the cash value
thereof, in accordance with this Section 206.




                                      12
<PAGE>   15



         (b)      In the case of any Regular Cash Dividend, the Company shall
pay, to the Holder of each Debenture, as a Regular Additional Distribution, the
amount of cash received by a holder of the number of Reference Shares
attributable to such Debenture in respect of such Regular Cash Dividend. Such
payment shall be made by the Company on the next Interest Payment Date to
Holders of Debentures as of 5:00 p.m., New York City time, on the Regular
Record Date for such Interest Payment Date.

         (c)      In the case of any Extraordinary Dividend, the Company shall
deliver, to the Holder of each Debenture, as an Extraordinary Additional
Distribution, all dividends and distributions, or the fair market value thereof
(determined in accordance with Section 206(d) or (e)), received by a holder of
the number of Reference Shares attributable to such Debenture in respect of
such Extraordinary Dividend. Any distribution pursuant to this subsection (c)
shall be made by the Company to Holders of Debentures as of a special record
date which shall be the 10th Business Day after the date of the payment of the
Extraordinary Distribution by the applicable Reference Company, and shall be
distributed to such Holders on the 10th Business Day following such special
record date.

         (d)      If an Extraordinary Distribution consists of securities or
units that are Marketable Securities (other than securities which are, or
become, Reference Shares), such securities or units will be distributed by the
Company to Holders of the Debentures in accordance with Section 206(c);
provided, that the Company shall not distribute fractional securities or units.
In lieu of fractional securities or units, the Company shall pay the Holders of
Debentures an amount in cash equal to the Closing Price, as of the special
record date, of the security or unit to be distributed multiplied by such
fractional interest. For purposes of determining the existence of fractional
interests, all Debentures held by a Holder shall be considered together (no
matter how many separate certificates such Holder may have). In the event the
Company is unable to distribute any securities or units as part of an
Extraordinary Additional Distribution because any necessary qualifications or
registrations of such securities or units under applicable state or federal
securities laws cannot be obtained on a timely basis, the Company may instead
deliver, in lieu of such securities or units, cash based on the average of the
Closing Prices of such securities or units over the five Trading Days ending on
the Trading Day next preceding the distribution by the Company of such
Extraordinary Additional Distribution.

         (e)      If an Extraordinary Distribution consists of cash, assets or
property other than securities or units that are Marketable Securities, the
Company shall pay to Holders of the Debentures an amount of cash equal to the
fair market value thereof; such fair market value to be determined as of the
date such Extraordinary Distribution is made or paid to holders of the
applicable Reference Shares. Such fair market value shall be equal to the
amount determined in good faith by the Board of Directors, unless the Board of
Directors determines in good faith that there is a substantial likelihood that
the aggregate fair market value will be in excess of $100,000,000, in which
case such fair market value shall be determined by a nationally recognized
investment banking or appraisal firm retained by the Company for this purpose.
The fair market value so determined shall be set forth in a Board Resolution
or, in the case of a determination by an investment banking or appraisal firm,
an Officers' Certificate.

         (f)      At least five Business Days prior to the payment or delivery
of an Extraordinary Additional Distribution by the Company pursuant to Section
206(c), the Company shall deliver



                                      13
<PAGE>   16



to the Trustee a Board Resolution setting a special record date for such
Extraordinary Additional Distribution and an Officers' Certificate setting
forth: (i) the exact amount of Marketable Securities or cash to be distributed
on or with respect to the Reference Shares attributable to each Debenture, and
(ii) the total amount of Marketable Securities or cash to be distributed on or
with respect to the Reference Shares attributable to all Debentures that are
Outstanding as of such special record date. If any distribution relates to any
assets or other property that is not publicly traded, then at least five
Business Days prior to such distribution, the Company shall deliver to the
Trustee: (i) a Board Resolution establishing the fair market value of the
assets or other property, unless such fair market value is determined by a
nationally recognized investment banking or appraisal firm, in which case the
Company shall deliver to the Trustee the report of such firm and (ii) an
Officers' Certificate setting forth (a) the exact amount of cash to be
distributed on or with respect to the Reference Shares attributable to each
Debenture and (b) the total amount of cash to be distributed on or with respect
to the Reference Shares attributable to all Debentures that are Outstanding as
of such special record date in respect of any assets or other property that is
not publicly traded. The Trustee is only responsible for distributing
Marketable Securities in the form of global book entry securities that are DTC
eligible. At or prior to 10:00 a.m., New York City time, on the date an
Extraordinary Additional Distribution is to be made pursuant to Section 206(c),
the Company shall (i) in the case of an Extraordinary Additional Distribution
consisting of cash, deposit with the Trustee or with a Paying Agent an amount
of cash equal to the Extraordinary Additional Distribution to be paid on such
date and (ii) in the case of an Extraordinary Additional Distribution
consisting of Marketable Securities, transfer by book-entry to the account of
the Trustee or a Paying Agent at DTC (or any successor Depository) the amount
of Marketable Securities to be distributed in such Extraordinary Additional
Distribution on such date. The Company shall act as its own Paying Agent for
any Marketable Securities to be delivered other than through book-entry. The
Company shall issue a press release setting forth the amount and composition,
per Debenture, of any Extraordinary Additional Distribution, and shall deliver
such press release to DTC for dissemination through the DTC broadcast facility.

         Section  207. Registration, Transfer and Exchange.

         The principal of and interest on the Debentures shall be payable and
the Debentures may be surrendered or presented for payment, the Debentures may
be surrendered for registration of transfer or exchange, and notices and
demands to or upon the Company in respect of the Debentures and the Indenture
may be served, at the office or agency of the Company maintained for such
purposes in The City of New York, State of New York from time to time, and the
Company hereby appoints the Trustee, acting through its office or agency in The
City of New York designated from time to time for such purpose, as its agent
for the foregoing purposes; provided, however, that at the option of the
Company payment of interest on the Debentures may be made by check mailed to
the address of the Persons entitled thereto, as such addresses shall appear in
the Security Register; and provided, further, that (subject to Section 1002 of
the Original Indenture) the Company may at any time remove the Trustee as its
office or agency in The City of New York designated for the foregoing purposes
and may from time to time designate one or more other offices or agencies for
the foregoing purposes and may from time to time rescind such designations.
Notwithstanding the foregoing, a Holder of $10 million or more in aggregate
Original Principal Amount of Debentures on a Regular Record Date shall be
entitled to receive interest payments on the next succeeding Interest Payment
Date, other than an Interest



                                      14
<PAGE>   17



Payment Date that is also the date of Maturity, by wire transfer of immediately
available funds if appropriate wire transfer instructions have been received in
writing by the Trustee not less than 15 calendar days prior to the applicable
Interest Payment Date. Any wire transfer instructions received by the Trustee
will remain in effect until revoked by the Holder.

         (a)      Rule 144A Debenture to Temporary Regulation S Debenture.
Prior to the expiration of the "40-day restricted period" (within the meaning
of Rule 903(c)(3) of Regulation S) (the "Restricted Period"), if a holder of a
beneficial interest in a Rule 144A Debenture deposited with the Depository
wishes at any time to exchange all or a portion of its interest in such Rule
144A Debenture for an interest in the Temporary Regulation S Debenture, or to
transfer all or a portion of its interest in such Rule 144A Debenture to a
Person who wishes to take delivery thereof in the form of an interest in such
Temporary Regulation S Debenture, such holder may, subject to the rules and
procedures of the Depository and to the requirements set forth in the following
sentence, exchange or cause the exchange or transfer or cause the transfer of
such interest for an equivalent beneficial interest in such Temporary
Regulation S Debenture. Upon receipt by the Trustee, as transfer agent, at its
principal corporate trust office in The City of New York of (1) instructions
given in accordance with the Depository's procedures from an agent member
directing the Trustee to credit or cause to be credited a beneficial interest
in the Temporary Regulation S Debenture in an amount equal to the beneficial
interest in the Rule 144A Debenture to be exchanged or transferred, (2) a
written order given in accordance with the Depository's procedures containing
information regarding the Euroclear or Cedel account to be credited with such
increase and the name of such account and (3) a certificate substantially in
the form of Exhibit B hereto given by the holder of such beneficial interest,
the Trustee, as transfer agent, shall instruct the Depository, its nominee, or
the custodian for the Depository, as the case may be, to reduce or reflect on
its records a reduction of the Rule 144A Debenture by the aggregate principal
amount of the beneficial interest in such Rule 144A Debenture to be so
exchanged or transferred and the Trustee, as transfer agent, shall instruct the
Depository, its nominee, or the custodian for the Depository, as the case may
be, concurrently with such reduction, to increase or reflect on its records an
increase of the principal amount of such Temporary Regulation S Debenture by
the aggregate principal amount of the beneficial interest in such Rule 144A
Debenture to be so exchanged or transferred, and to credit or cause to be
credited to the account of the Person specified in such instructions (who shall
be the agent member of Euroclear or Cedel, or both, as the case may be) a
beneficial interest in such Temporary Regulation S Debenture equal to the
reduction in the principal amount of such Rule 144A Debenture.

         (b)      Rule 144A Debenture to Permanent Regulation S Debenture.
After the expiration of the Restricted Period, if a holder of a beneficial
interest in the Rule 144A Debenture deposited with the Depository wishes at any
time to exchange all or a portion of its interest in such Rule 144A Debenture
for an interest in the Permanent Regulation S Debenture, or to transfer all or
a portion of its interest in such Rule 144A Debenture to a Person who wishes to
take delivery thereof in the form of an interest in such Permanent Regulation S
Debenture, such holder may, subject to the rules and procedures of the
Depository and to the requirements set forth in the following sentence,
exchange or cause the exchange or transfer or cause the transfer of such
interest for an equivalent beneficial interest in such Permanent Regulation S
Debenture. Upon receipt by the Trustee, as transfer agent, at its principal
corporate trust office in The City of New York of (1) instructions given in
accordance with the Depository's procedures from an agent




                                      15
<PAGE>   18




member directing the Trustee to credit or cause to be credited a beneficial
interest in the Permanent Regulation S Debenture in an amount equal to the
beneficial interest in the Rule 144A Debenture to be exchanged or transferred,
(2) a written order given in accordance with the Depository's procedures
containing information regarding the Euroclear or Cedel account to be credited
with such increase and (3) a certificate substantially in the form of Exhibit C
hereto given by the holder of such beneficial interest, the Trustee, as
transfer agent, shall instruct the Depository, its nominee, or the custodian
for the Depository, as the case may be, to reduce or reflect on its records a
reduction of the Rule 144A Debenture by the aggregate principal amount of the
beneficial interest in such Rule 144A Debenture to be so exchanged or
transferred and the Trustee, as transfer agent, shall instruct the Depository,
its nominee, or the custodian for the Depository, as the case may be,
concurrently with such reduction, to increase or reflect on its records an
increase of the principal amount of such Permanent Regulation S Debenture by
the aggregate principal amount of the beneficial interest in such Rule 144A
Debenture to be so exchanged or transferred, and to credit or cause to be
credited to the account of the Person specified in such instructions (who shall
be the agent member of Euroclear or Cedel, or both, as the case may be) a
beneficial interest in such Permanent Regulation S Debenture equal to the
reduction in the principal amount of such Rule 144A Debenture.

         (c)      Regulation S Security to Rule 144A Debenture. If a holder of
a beneficial interest in the Temporary Regulation S Debenture or the Permanent
Regulation S Debenture which is deposited with the Depository wishes at any
time to exchange its interest for an interest in the Rule 144A Debenture, or to
transfer its interest in such Temporary Regulation S Debenture or Permanent
Regulation S Debenture to a Person who wishes to take delivery thereof in the
form of an interest in such Rule 144A Debenture, such holder may, subject to
the rules and procedures of Euroclear or Cedel and the Depository, as the case
may be, and to the requirements set forth in the following sentence, exchange
or cause the exchange or transfer or cause the transfer of such interest for an
equivalent beneficial interest in such Rule 144A Debenture. Upon receipt by the
Trustee, as transfer agent, at its principal corporate trust office in The City
of New York of (1) instructions from Euroclear or Cedel or the Depository, as
the case may be, directing the Trustee, as transfer agent, to credit or cause
to be credited a beneficial interest in the Rule 144A Debenture in an amount
equal to the beneficial interest in the Temporary Regulation S Debenture or the
Permanent Regulation S Debenture to be exchanged or transferred, such
instructions to contain information regarding the agent member's account with
the Depository to be credited with such increase, and (2) with respect to an
exchange or transfer of an interest in the Temporary Regulation S Debenture
(but not the Permanent Regulation S Debenture) for an interest in the Rule 144A
Debenture, a certificate substantially in the form of Exhibit D hereto given by
the holder of such beneficial interest, the Trustee, as transfer agent, shall
instruct the Depository, its nominee, or the custodian for the Depository, as
the case may be, to reduce or reflect on its records a reduction of the
Temporary Regulation S Debenture or such Permanent Regulation S Debenture, as
the case may be, by the aggregate principal amount of the beneficial interest
in such Temporary Regulation S Debenture or such Permanent Regulation S
Debenture to be exchanged or transferred, and the Trustee, as transfer agent,
shall instruct the Depository, its nominee, or the custodian for the
Depository, as the case may be, concurrently with such reduction, to increase
or reflect on its records an increase of the principal amount of such Rule 144A
Debenture by the aggregate principal amount of the beneficial interest in such
Permanent Regulation S Debenture or such Temporary Regulation S Debenture, as
the case may be, to be so exchanged or transferred, and to credit or cause to
be credited to the account of the Person





                                      16
<PAGE>   19


specified in such instructions a beneficial interest in such Rule 144A
Debenture equal to the reduction in the principal amount of such Permanent
Regulation S Debenture or such Temporary Regulation S Debenture, as the case
may be.

         (d)      Temporary Regulation S Debenture to Permanent Regulation S
Debenture. After the expiration of the Restricted Period, interests in a
Temporary Regulation S Debenture as to which the Trustee has received from
Euroclear or Cedel, as the case may be, a certificate substantially in the form
of Exhibit E hereto to the effect that Euroclear or Cedel, as applicable, has
received a certificate substantially in the form of Exhibit F hereto from the
holder of a beneficial interest in such Temporary Regulation S Debenture, will
be exchanged, on and after the Restricted Period, for interests in the
Permanent Regulation S Debenture. The Trustee shall effect such exchange by
delivering to the Depository for credit to the respective accounts of the
holders of Debentures represented by a beneficial interest in the Temporary
Regulation S Global Debenture, a duly executed and authenticated Permanent
Regulation S Debenture, representing the principal amount of interests in the
Temporary Regulation S Debenture initially exchanged for interests in the
Permanent Regulation S Debenture. The delivery to the Trustee by Euroclear or
Cedel of the certificate or certificates referred to above may be relied upon
by the Company and the Trustee as conclusive evidence that the certificate or
certificates referred to therein has or have been delivered to Euroclear or
Cedel pursuant to the terms of this Fourth Supplemental Indenture and the
Temporary Regulation S Debenture. Upon any exchange of interests in a Temporary
Regulation S Debenture for interests in a Permanent Regulation S Debenture, the
Trustee shall endorse the Temporary Regulation S Debenture to reflect the
reduction in the principal amount represented thereby by the amount so
exchanged and shall endorse the Permanent Regulation S Debenture to reflect the
corresponding increase in the amount represented thereby. Until so exchanged in
full and except as provided therein, the Temporary Regulation S Debenture, and
the Debentures evidenced thereby, shall in all respects be entitled to the same
benefits under the Indenture as the Permanent Regulation S Debenture and the
Rule 144A Debenture authenticated and delivered hereunder.

         Section 208. Redemption of the Debentures.

         (a)      Optional Redemption. The Debentures will be redeemable at the
option of the Company, in whole or in part (provided that immediately after any
partial redemption at least $100,000,000 Original Principal Amount of
Debentures would remain outstanding) at any time or from time to time after
February 15, 2004, on at least 30 Business Days (but not more than 60 days)
prior notice to Holders of the Debentures. In the notice of redemption, the
Company shall specify its irrevocable election of one of the following options:

                  (i) to terminate Holders' right to exchange, in accordance
         with Section 209, Debentures called for redemption (but not affecting
         the exchange rights of Holders of any Debentures not called for
         redemption), in which case (A) no further exchange of such Debentures
         called for redemption pursuant to Section 209 will be permitted on or
         after the 30th Business Day preceding the Redemption Date and (B) on
         the Redemption Date, the Company shall pay Holders, for each Debenture
         to be redeemed, a Redemption Price, in cash, equal to the sum of (1)
         the greater of (a) the Adjusted Principal Amount of such Debenture as
         of the Redemption Date and (b) 100% of the Current Market Value of the
         Reference Shares attributable to such Debenture, subject to adjustment
         pursuant to Section 218 in respect of any Premium Adjustments, (2) any
         accrued and unpaid interest on such Debenture to the Redemption Date,
         (3) the amount of any payment required to made pursuant to



                                      17
<PAGE>   20



         Section 218 in respect of any Special Payment Adjustment and (4),
         subject to Section 211, any Final Period Distribution on such
         Debenture; or

                  (ii) to exchange Debentures surrendered at the option of
         Holders in accordance with Section 209, for Reference Shares until
         5:00 p.m., New York City time, on the Trading Day next preceding the
         Redemption Date, in which case on the Redemption Date the Company
         shall pay Holders who do not elect to exchange Debentures for
         Reference Shares in accordance with Section 209(c), for each Debenture
         to be redeemed, a Redemption Price, in cash, equal to the sum of (1)
         the Adjusted Principal Amount of such Debenture at the Redemption
         Date, (2) any accrued and unpaid interest on such Debenture to the
         Redemption Date, (3) the amount of any payment required to made
         pursuant to Section 218 in respect of any Special Payment Adjustment
         and (4), subject to Section 211, any Final Period Distribution on such
         Debenture.

         (b)      Tax Event Redemption. If at any time on or prior to May 15,
2000, a Tax Event shall have occurred, the Company shall have the right,
exercisable by giving notice of such redemption to the Trustee within 180 days
after the Tax Event, to give notice to Holders of the Debentures of a Tax Event
Redemption, which shall occur not less than twenty-five (25) Business Days
following the giving of such notice. Any Tax Event Redemption must apply to all
Outstanding Debentures. On the Redemption Date specified in the notice of
redemption to Holders of the Debentures, the Company shall pay Holders for each
Debenture a Redemption Price, in cash, equal to the sum of (1) the greater of
(A) 102% of the Adjusted Principal Amount of such Debenture and (B) 100% of the
Current Market Value of the Reference Shares attributable to such Debenture,
subject to adjustment pursuant to Section 218 in respect of any Premium
Adjustments, (2) any accrued and unpaid interest to the Redemption Date, (3)
the amount of any payment required to made pursuant to Section 218 in respect
of any Special Payment Adjustment and (4), subject to Section 211, any Final
Period Distribution on such Debenture. The Holders' right to exchange
Debentures pursuant to Section 209 shall terminate on the later of the date
notice of a Tax Event Redemption is given or the 25th Business Day prior to the
Redemption Date.

         (c)      Share Event Redemption. If at any time on or prior to
February 15, 2004, a Share Event shall have occurred, the Company shall have
the right, exercisable by giving notice of such redemption to the Trustee
within five Business Days after the Share Event, to redeem the Debentures, in
whole but not in part, on not less than twenty-five (25) Business Days (but not
more than 60 days) notice to Holders of the Debentures. On the Redemption Date
specified in the notice of redemption, the Company shall pay Holders for each
Debenture a Redemption Price, in cash, equal to the sum of (1) the greater of
(A) the Adjusted Principal Amount of such Debenture as of the Redemption Date
and (B) the sum of 100% of the Current Market Value of the Reference Shares
attributable to such Debenture, subject to adjustment pursuant to Section 218
in respect of any Premium Adjustments, and $115.04, (2) the remaining scheduled
semi-annual interest payments on such Debenture through and including February
15, 2004, (3) the amount of any payment required to made pursuant to Section
218 in respect of any Special Payment Adjustment and (4), subject to Section
211, any Final Period Distribution on such Debenture. The Holders' right to
exchange Debentures pursuant to Section 209 shall terminate on the later of the
date notice of a Share Event Redemption is given or the 25th Business Day prior
to the Redemption Date.



                                      18
<PAGE>   21



         (d)      Excess Borrow Cost Redemption. If at any time on or prior to
February 15, 2004, an Excess Borrow Cost Period shall have occurred, the
Company shall have the right, exercisable by giving notice of such redemption
to the Trustee within 180 days after the occurrence of the Excess Borrow Cost
Period, to redeem the Debentures, in whole but not in part, on not less than
twenty-five (25) Business Days (but not more than 60 days) notice to Holders of
the Debentures. On the Redemption Date specified in the notice of redemption,
the Company shall pay Holders for each Debenture a Redemption Price, in cash,
equal to the sum of (1) the greater of (A) 102% of the Adjusted Principal
Amount of such Debenture as of the Redemption Date and (B) the sum of 100% of
the Current Market Value of the Reference Shares attributable to such
Debenture, subject to adjustment pursuant to Section 218 in respect of any
Premium Adjustments, (2) any accrued but unpaid interest to the Redemption
Date, (3) the amount of any payment required to made pursuant to Section 218 in
respect of any Special Payment Adjustment and (4), subject to Section 211, any
Final Period Distribution on such Debenture. The Holders' right to exchange
Debentures pursuant to Section 209 shall terminate on the later of the date
notice of a Excess Borrow Cost Redemption is given or the 25th Business Day
prior to the Redemption Date.

         (e)      Notices. In case of any redemption, the Company shall deliver
an Officers' Certificate to the Trustee not less than five Business Days prior
to the Redemption Date which sets forth (i) the Redemption Price to be paid for
each Debenture called for redemption on such Redemption Date and (ii) the
aggregate amount payable for all Debentures called for redemption on such
Redemption Date.

         (f)      Interest Accrual to Cease. Once notice of redemption has been
given and funds are irrevocably deposited with the Trustee, interest on the
Debentures will cease to accrue on and after the Redemption Date and all rights
of the Holders of the Debentures called for redemption will cease, except for
the right of Holders to receive the Redemption Price (but without interest on
such Redemption Price) and any right to receive payment pursuant to Section
211.

         (g)      Payment Failure. In the event that the Company fails to pay
any amount due on redemption of the Debentures on a Redemption Date, interest
on the Debentures called for redemption shall continue to accrue at an annual
rate of 3 3/4% of the Original Principal Amount thereof from the date
originally set for redemption to the actual date of payment, and such actual
date of payment shall be deemed to be the Redemption Date for purposes of
calculating the amount to be paid to the Holders of Debentures on redemption,
except that the amount of the Final Period Distribution shall be determined as
of the date originally set for redemption.

         (h)      Company Notice. Section 1002 of the Original Indenture is
hereby deleted, solely with respect to the Debentures, and in lieu thereof the
following shall be applicable to the Debentures:

                  "The election of the Company to optionally redeem any
         Debentures shall be evidenced by or pursuant to a Board Resolution. In
         the case of any optional redemption by the Company that involves less
         than all of the Debentures, the Company shall, at least 60 days prior
         to the Redemption Date fixed by the Company (unless a shorter period
         shall


                                      19
<PAGE>   22



         be acceptable to the Trustee), notify the Trustee of such Redemption
         Date and of the Original Principal Amount of Debentures to be
         redeemed."

         Section  209. Exchange of the Debentures.

         (a)      Each Debenture will be exchangeable at the option of the
Holder at any time (except as otherwise provided in subsection (f) below) for
the Exchange Market Value of the Reference Shares attributable to that
Debenture. The number of Reference Shares attributable to each Debenture shall
be 16.7764, subject to adjustment as a result of any Reference Share
Proportionate Reduction, any Premium Adjustment, or any other adjustment
contemplated by the definition of "Reference Shares."

         (b)      The Company shall pay 100% of the Exchange Market Value,
subject to adjustment pursuant to Section 218 hereof in respect of any Premium
Adjustments, of the Reference Shares attributable to each Debenture, only in
cash, for all exchanges made on or before the Reference Shares Eligibility
Date. From and after the Reference Shares Eligibility Date, the Company may, at
its option, (i) pay 100% of the Exchange Market Value of the Reference Shares
attributable to each Debenture, subject to adjustment pursuant to Section 218
in respect of any Premium Adjustments, in cash; (ii) deliver the Reference
Shares attributable to such Debenture in payment of such Exchange Market Value;
or (iii) deliver a combination of Reference Shares and cash. Such payment or
delivery will be made as promptly as practicable, but in any event within ten
Trading Days after the date of determination of the Exchange Market Value. The
Company shall notify the Exchange Agent of its election to pay cash or deliver
Reference Shares, or a combination of the foregoing, by no later than 9:30
a.m., New York City time, on the Trading Day next following the applicable
Exchange Date. The Exchange Agent shall notify an exchanging Holder of the
Company's election under this Section 209(b) prior to 10:00 a.m., New York City
time, on the next Trading Day after the Exchange Date.

         (c)      To exchange a Debenture a Holder must (a) in the case of a
Debenture held through the Depository, surrender such Debenture for exchange
through book-entry transfer into the account of the Exchange Agent, transmit an
agent's message requesting such exchange and comply with such other procedures
of the Depository as may be applicable in the case of an exchange and (b) in
the case of a Debenture held in certificated form, (i) complete and manually
sign the Notice of Exchange attached to the Debenture (or complete and sign a
facsimile of the Notice of Exchange) and deliver such Notice of Exchange to the
Exchange Agent, (ii) surrender the Debenture to the Exchange Agent, (iii)
furnish appropriate endorsements and transfer documents, if required by the
Exchange Agent, the Company or the Trustee and (iv) pay any transfer or similar
tax, if required. An exchange shall be deemed to have been effected at 5:00
p.m., New York City time, on the Exchange Date. The delivery of a Notice of
Exchange or, in the case of book-entry, an agent's message requesting exchange,
shall be irrevocable. A Holder may exchange a portion of its Debentures only if
the portion is $1,000 Original Principal Amount or an integral multiple
thereof. Following the Exchange Date for an exchange of Debentures, all rights
of the Holder with respect to such Debentures shall cease, except for the right
of such Holder to receive 100% of the Exchange Market Value, subject to
adjustment pursuant to Section 218 in respect of any Premium Adjustments (but
without interest thereon), of the Reference Shares attributable to such
Debentures.





                                      20
<PAGE>   23






         (d)      By 10:00 a.m., New York City time, on each Trading Day
following receipt by the Exchange Agent of notification from DTC that DTC has
received an agent's message from a DTC participant electing to exercise its
exchange option with respect to its Debentures, and delivery of such Debentures
into the Exchange Agent's DTC participant account, or following receipt of a
complete manually signed Notice of Exchange and receipt of certificated
Debentures from a Holder, the Exchange Agent shall notify the Company of the
principal amount of Debentures which has been tendered. When the Exchange
Market Value has been determined, the Company shall deliver an Officers'
Certificate to the Trustee setting forth the exact amount to be paid or the
amount of Reference Shares to be delivered to the tendering Holder and shall
deposit such amount with the Exchange Agent (except that if the Company elects
to deliver Reference Shares in certificated form, the Company shall act as its
own Paying Agent as to such shares). Upon receipt of such payment or delivery
from the Company, the Exchange Agent shall pay DTC as soon as practicable or,
in the cases of Debentures that are held in certificated form, as directed by
the tendering Holder. Where the Company acts as its own Paying Agent with
respect to certificated Reference Shares, it shall deliver them (i) as directed
by the relevant participants of the Depositary, as identified by the
Depositary, or (ii) to or at the direction of tendering Holders of Debentures.

         (e)      In the case of any exchange made during the period from (but
excluding) a Regular Record Date for any Interest Payment Date to (but
excluding) such Interest Payment Date, the Holder shall tender funds equal to
the interest and any Additional Distribution payable on such Interest Payment
Date.

         (f)      The right to exchange Debentures pursuant to this Section 209
shall terminate at 5:00 p.m., New York City time, (i) in the case of Stated
Maturity of the principal amount of the Debentures, on the Trading Day
immediately preceding such Stated Maturity and (ii) in the case of an optional
redemption, on the Trading Day immediately preceding the Redemption Date. A
Holder's right to exchange Debentures under this Section 209 shall further be
subject to termination by the Company (i) in connection with the payment of the
Debentures at Stated Maturity, during the period set forth in the penultimate
sentence of Section 206(b), (ii) in connection with optional redemption, during
the period set forth in clause (i) of Section 208(a), provided, that any such
termination shall only apply to Debentures that have been called for
redemption, (iii) in connection with a Tax Event Redemption, during the period
set forth in Section 208(b), (iv) in connection with a Share Event Redemption,
during the period set forth in Section 208(c) and (v) in connection with an
Excess Borrow Cost Redemption, during the period set forth in Section 208(d).

         (g)      If more than $1,000,000 aggregate Original Principal Amount
of Debentures are tendered for exchange on any given date, the Company shall
give notice of such event to the Trustee and the Trustee shall give notice
thereof to DTC for distribution through its broadcast facility.

         Section  210. Distributions of Reference Shares or Other Securities.

         (a)      The Company will pay any and all documentary, stamp, transfer
or similar taxes that may be payable in respect of the transfer and delivery of
Reference Shares or in connection with an Extraordinary Additional Distribution
pursuant hereto; provided, however, that the



                                      21
<PAGE>   24



Company shall not be required to pay any such tax which may be payable in
respect of any transfer involved in delivery of such property to a name other
than that in which the Debentures were registered, and no such transfer or
delivery shall be made unless and until the Person requesting such transfer has
paid to the Company the amount of any such tax, or has established, to the
satisfaction of the Company, that such tax has been paid.

         (b)      The Company hereby warrants that upon delivery of any
Reference Shares or any securities in connection with any Extraordinary
Additional Distribution pursuant to this Supplemental Indenture, the Holder of
a Debenture shall receive all rights held by the Company in the securities to
be delivered, free and clear of any and all liens, claims, charges and
encumbrances, other than any liens, claims, charges and encumbrances which may
have been placed thereon by the prior owner thereof prior to the time acquired
by the Company. In addition, the Company further warrants that any securities
to be delivered hereunder shall be free of any transfer restrictions under
federal or state securities laws (other than such as are solely attributable to
any Holder's status as an affiliate of the issuer of such securities).

         Section  211. Balance of Final Period Distribution Payment.

         (a)      In the case of a Final Period Distribution within the meaning
of clause (b) of the definition of "Final Period Distribution," the Company
shall pay such Final Period Distribution to the Holders of Debentures that have
been repaid in accordance with the first sentence of Section 204(b) or redeemed
in accordance with Section 208(a)(ii), (b), (c) or (d) as of a special record
date which shall be the 10th Business Day after the date of the payment of the
relevant Extraordinary Distribution by the applicable Reference Company; and
such payment shall be distributed on the 10th Business Day following such
special record date. The Company shall give notice regarding such distribution
to the Trustee in accordance with the provisions of Section 206(f).

         (b)      In the event that the applicable Reference Company fails to
make the Extraordinary Distribution referred to in subsection (a) above at the
time or in the amount expected, the Company shall pursue any claim it has
against such Reference Company, whether as a securityholder or otherwise, on
behalf of the Holders of Debentures. Reasonable costs of such actions by the
Company may be deducted from the amount of any Extraordinary Distribution
before any distribution is made to Holders of Debentures pursuant to Section
211(a).

         Section  212. Denominations.

         The Debentures shall be issued in denominations of $1,000 and integral
multiples in excess thereof.

         Section  213. Applicability of Certain Original Indenture Provisions.

         Section  402 of the Original Indenture, relating to defeasance and
covenant defeasance, shall not be applicable to the Debentures.




                                      22
<PAGE>   25




         Section  214. Security Registrar and Paying Agent.

         The Trustee shall be the initial Paying Agent and initial transfer
agent for the Debentures (subject to the Company's right (subject to Section
1002 of the Original Indenture) to remove the Trustee as such Paying Agent
and/or transfer agent and, from time to time, to designate one or more
co-registrars and one or more other Paying Agents and transfer agents and to
rescind from time to time any such designations), and The City of New York is
designated as a Place of Payment for the Debentures.

         Section  215. Global Debentures.

         (a)      The Debentures shall be issued in the form of one or more
temporary or global Debentures. The initial Depository for the global
Debentures shall be DTC, and the depositary arrangements shall be those
employed by whoever shall be the Depositary with respect to the Debentures from
time to time.

         (b)      Rule 144A Debentures. Debentures initially offered and sold
in reliance on Rule 144A to Qualified Institutional Buyers (as such term is
defined in Rule 144A) shall be issued in the form of permanent global
Debentures in definitive fully registered form without interest coupons,
substantially in the form of Exhibit A-1 (a "Rule 144A Debenture"). Each Rule
144A Debenture shall be deposited on behalf of the purchasers of the Debentures
represented thereby with the custodian for the Depositary, and registered in
the name of a nominee of the Depositary, duly executed by the Company and
authenticated by the Trustee as provided in the Original Indenture. The
aggregate principal amount of a Rule 144A Debenture may from time to time be
increased or decreased by adjustments made on the records of the custodian for
the Depositary or the Depositary or its nominee, as the case may be.

         (c)      Temporary Regulation S Debentures; Permanent Regulation S
Debentures. Debentures initially offered and sold in reliance on Regulation S
shall be issued in the form of temporary global Debentures in definitive fully
registered form without interest coupons, substantially in the form of Exhibit
A-2 (a "Temporary Regulation S Debenture"). Each Temporary Regulation S
Debenture shall be deposited on behalf of the purchasers of the Debentures
represented thereby with the custodian for the Depositary, and registered in
the name of a nominee of the Depositary, duly executed by the Company and
authenticated by the Trustee as provided herein, for credit to their respective
accounts (or to such other accounts as they may direct) at Euroclear or Cedel.
After the expiration of the Restricted Period, each Temporary Regulation S
Debenture will be exchanged for a permanent global Debenture, substantially in
the form of Exhibit A-3 (a "Permanent Regulation S Debenture"). Until the
expiration of the Restricted Period, interests in a Temporary Regulation S
Debenture may only be held by agent members of Euroclear and Cedel. During the
Restricted Period, interests in a Temporary Regulation S Debenture may be
exchanged for interests in a Rule 144A Debenture. The aggregate principal
amount of a Temporary Regulation S Debenture and a Permanent Regulation S
Debenture may from time to time be increased or decreased by adjustments made
on the records of the custodian for the Depositary or the Depositary or its
nominee, as the case may be, as provided herein.




                                      23
<PAGE>   26



         The provisions of the "Operating Procedures of the Euroclear System"
and the "Terms and Conditions Governing Use of Euroclear" and the "Management
Regulations" and "Instructions to Participants" of Cedel, respectively, shall
be applicable to any global Debenture insofar as interests in such global
Debenture are held by the agent members of Euroclear or Cedel. Account holders
or participants in Euroclear and Cedel shall have no rights under the Indenture
with respect to such global Debenture, and the Depositary or its nominee may be
treated by the Company, the Trustee, and any agent of the Company or the
Trustee as the owner of such global Debenture 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 DTC and its agent members, the operation of customary
practices governing the exercise of the rights of a holder of any Debenture.

         (d)      The Rule 144A Debentures, the Temporary Regulation S
Debentures and the Permanent Regulation S Debentures will be exchangeable for
certificated Debentures of like tenor and terms and of differing authorized
denominations aggregating a like principal amount, only if (i) the Depository
notifies the Company that it is unwilling or unable to continue as Depository
for the Rule 144A Debentures, the Temporary Regulation S Debentures and the
Permanent Regulation S Debentures, (ii) the Depository ceases to be a clearing
agency under the Securities Exchange Act, (iii) the Company in its sole
discretion determines that the Rule 144A Debentures, the Temporary Regulation S
Debentures and the Permanent Regulation S Debentures shall be exchangeable for
certificated Debentures or (iv) there shall have occurred and be continuing an
Event of Default under the Indenture with respect to the Debentures. Upon such
exchange, the certificated Debentures shall be registered in the names of the
beneficial owners of the Rule 144A Debentures which they have replaced; such
names shall be provided to the Trustee by the relevant participants of the
Depository, as identified by the Depository.

         Section  216. Sinking Fund.

         The Debentures shall not be subject to any sinking fund or similar
provision and shall not be redeemable at the option of the holder thereof.

         Section  217. Amendments to Certain Sections of the Original
Indenture.

         (a)      The amendments to the Original Indenture contained in this
Section 217 shall apply only to the series of Debentures established pursuant
to this Fourth Supplemental Indenture.

         (b)      Clause (1) of Section 501 of the Original Indenture is hereby
amended by adding the words "or distributions" following the word "interest" on
the first and third lines and the words "(including any Special Payment
Adjustment)" following the word "Series" on the second line thereof.

         (c)      A new clause (3) is hereby added to Section 501 of the
Original Indenture, to read as follows, and existing clauses (3) through (9)
are renumbered accordingly and all references in the Original Indenture to
existing clauses (3) through (9) are renumbered accordingly:



                                      24
<PAGE>   27



                           (3) failure of the Company to comply with its
                  obligations to deliver cash or Reference Shares in exchange
                  for Debentures pursuant to Section 209 of the Fourth
                  Supplemental Indenture.

         (d)      The first paragraph of Section 502 of the Original Indenture
is hereby amended by adding the words "(including any Special Payment
Adjustment)" following the word "interest" in the eighth line thereof.

         (e) Clauses (1) and (2) of the second paragraph of Section 502 of the
Original Indenture are hereby amended by adding the words "and distributions"
following the word "interest" in the second line of each such clause.

         (f)      Clause (1) of Section 902 of the Original Indenture is hereby
amended by adding the words "or distributions" following the word "interest" on
the second line and the words "(including any Special Payment Adjustment)"
following the word "Series" on the second line of such clause.

         (g)      Section 902 of the Original Indenture is hereby further
amended by adding a new clause (5), to read as follows:

                           (5) reduce the amount of cash or Reference Shares
                  deliverable upon exchange of the Debentures.

         (h)      Unless the context otherwise requires, all references to
payment of principal in the Original Indenture shall include the payment of the
Maturity Repayment Amount, and all references to payment of interest shall
include Additional Distributions and any Special Payment Adjustment.

         Section  218. Adjustment for Excess Borrow Costs.

         (a)      If, during the Borrow Period, the Determination Agent
determines that an Excess Borrow Cost Period exists for any quarter ended
February 15, May 15, August 15 or November 15, then the Company, at its
election, must either:

                  (i) effective as of the first day of the next succeeding
         quarter, apply a Premium Adjustment to the Exchange Market Value or
         the Current Market Value of the Reference Shares attributable to each
         Debenture, as applicable, upon (i) any optional or mandatory
         redemption of such Debenture pursuant to Section 208, (ii) any
         exchange of such Debenture by the Holder thereof pursuant to Section
         209 and (iii) any payment for such Debenture at Stated Maturity or
         upon any acceleration of the maturity of such Debenture pursuant to
         Section 204; or

                  (ii) for the next succeeding quarter, pay a Special Payment
         Adjustment on each Debenture;

provided, however, that the Company shall not be required to effect a Premium
Adjustment or a Special Payment Adjustment, of any combination thereof, more
than eight times.


                                      25
<PAGE>   28


         (b)      If the Company elects to make a Premium Adjustment in respect
of an Excess Borrow Cost Period, such Premium Adjustment shall be added to any
Premium Adjustments elected by the Company in respect of earlier Excess Borrow
Cost Periods.

         (c)      If the Company elects to pay a Special Payment Adjustment,
the amount payable as a result of such adjustment shall be paid by the Company
on the next succeeding Interest Payment Date after (or on the last day of) the
quarter in respect of which such payment is made. If the Company elects to pay
a Special Payment Adjustment in respect of an Excess Borrow Cost Period and,
prior to the payment thereof on the succeeding Interest Payment Date, effects
an optional or mandatory redemption of Debentures pursuant to Section 208 or
repays the Debentures upon any acceleration of the maturity of the Debenture
pursuant to Section 204, the amount of the Special Payment Adjustment required
to paid in connection with such redemption or repayment shall be equal to the
amount of the Special Payment Adjustment that would have been payable on such
succeeding Interest Payment Date. If the Company notifies Holders of Debentures
of the Company's election to redeem the Debentures pursuant to Section 208(d)
and after the giving of such notice, and prior to the related Redemption Date,
an Excess Borrow Cost Period occurs, then the Company shall become obligated to
pay a Special Payment Adjustment in respect of such Excess Borrow Cost Period
(in addition to any Special Payment Adjustment that may be payable on such
Redemption Date in respect of an earlier Excess Borrow Cost Period).

         (d)      Upon any election pursuant to this Section 218, the Company
will give notice of such election to the Trustee and will promptly issue a
press release giving notice of its election to make a Premium Adjustment or to
pay a Special Payment Adjustment and will deliver such press release to DTC for
dissemination through the DTC broadcast facility.


                                 ARTICLE THREE

                            MISCELLANEOUS PROVISIONS

         The Trustee makes no undertaking or representations in respect of, and
shall not be responsible in any manner whatsoever for and in respect of, the
validity or sufficiency of this Fourth Supplemental Indenture or the proper
authorization or the due execution hereof by the Company or for or in respect
of the recitals and statements contained herein, all of which recitals and
statements are made solely by the Company.

         Except as expressly amended hereby, the Original Indenture shall
continue in full force and effect in accordance with the provisions thereof and
the Original Indenture is in all respects hereby ratified and confirmed. This
Fourth Supplemental Indenture and all its provisions shall be deemed a part of
the Original Indenture in the manner and to the extent herein and therein
provided.

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




                                      26
<PAGE>   29




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




                                      27
<PAGE>   30





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

                            LIBERTY MEDIA CORPORATION



                            By:
                                -----------------------------------------------
                                   Name:  Charles Y. Tanabe
                                   Title: Senior Vice President and
                                            General Counsel


                            THE BANK OF NEW YORK, as Trustee



                            By:
                                -----------------------------------------------
                                   Name:  Walter N. Gitlin
                                   Title: Vice President




                                      28
<PAGE>   31





              EXHIBITS A-1 THROUGH A-4 ARE INTENTIONALLY OMITTED.


                                       )





                                      A-1






<PAGE>   32


                                                                     EXHIBIT B





                          FORM OF TRANSFER CERTIFICATE
               FOR EXCHANGE OR TRANSFER FROM RULE 144A DEBENTURE
                      TO TEMPORARY REGULATION S DEBENTURE



The Bank of New York
101 Barclay Street
Floor 21 West
New York, New York  10286

                  Re:      Liberty Media Corporation
                           $750,000,000 3 3/4% Senior Exchangeable Debentures
                           due 2030 (the "Debentures")

         Reference is hereby made to the Indenture dated as of July 7, 1999,
between THE BANK OF NEW YORK (the "Trustee") and LIBERTY MEDIA CORPORATION (the
"Company") (as supplemented by the Fourth Supplemental Indenture, dated as of
February 10, 2000, between the Company and the Trustee, the "Indenture").
Capitalized terms not defined in this Certificate shall have the meanings given
to them in the Indenture.

         This Certificate relates to ______________ Original Principal Amount
of Debentures represented by a beneficial interest in the Rule 144A Debenture
(CUSIP No.____) held through the Depository by or on behalf of _____________ as
beneficial owner (the "Transferor"). The Transferor has requested an exchange
or transfer of its beneficial interest for an interest in the Temporary
Regulation S Debenture (CUSIP (CINS) No._____) to be held with [Euroclear]
[Cedel] (ISIN Code _____) (Common Code _____) through the Depository.

         In connection with such request and in respect of such Debentures, the
Transferor does hereby certify that such exchange or transfer has been effected
in accordance with the transfer restrictions set forth in the Debentures and
pursuant to and in accordance with Rule 903 or Rule 904 (as applicable) of
Regulation S under the Securities Act, and accordingly the Transferor does
hereby certify that:

         (1)      the offer of the Debentures was not made to a person in the
                  United States;

         (2)      either:  (A)      at the time the buy order was originated,
                                    the transferee was outside the United States
                                    or the Transferor and any person acting on
                                    its behalf reasonably believed that the
                                    transferee was outside the United States,
                                    or

                           (B)      the transaction was executed in, on or
                                    through the facilities of a designated
                                    offshore securities market and neither the
                                    Transferor nor any person acting on its
                                    behalf knows that the transaction was
                                    prearranged with a buyer in the United
                                    States;



                                      B-1





<PAGE>   33



         (3)      no directed selling efforts have been made in contravention
                  of the requirements of Rule 903(b) or 904(b) of Regulation S,
                  as applicable;

         (4)      the transaction is not part of a plan or scheme to evade the
                  registration requirements of the Securities Act; and

         (5)      upon completion of the transaction, the beneficial interest
                  being transferred as described above is to be held with the
                  Depository through Euroclear or Cedel or both (Common Code
                  ____ (ISIN Code _____)).

         This Certificate and the statements contained herein are made for your
benefit and the benefit of the Company and the initial purchaser of the
Debentures being exchanged or transferred. Terms used in this Certificate and
not otherwise defined in the Indenture have the meanings set forth in
Regulation S under the Securities Act.

                                           [Insert Name of Transferor]



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


Dated:
       ----------------------------



cc:  Liberty Media Corporation



                                      B-2



<PAGE>   34



                                                                     EXHIBIT C


                   FORM OF TRANSFER CERTIFICATE FOR TRANSFER
                      OR EXCHANGE FROM RULE 144A DEBENTURE
                      TO PERMANENT REGULATION S DEBENTURE


The Bank of New York
101 Barclay Street
Floor 21 West
New York, New York  10286

                  Re:      Liberty Media Corporation
                           $750,000,000 3 3/4% Senior Exchangeable Debentures
                           due 2030 (the "Debentures")

         Reference is hereby made to the Indenture dated as of July 7, 1999,
between THE BANK OF NEW YORK (the "Trustee") and LIBERTY MEDIA CORPORATION (the
"Company") (as supplemented by the Fourth Supplemental Indenture, dated as of
February 10, 2000, between the Company and the Trustee, the "Indenture").
Capitalized terms not defined in this Certificate shall have the meanings given
to them in the Indenture.

         This Certificate relates to ______________ Original Principal Amount
of Debentures represented by a beneficial interest in the Rule 144A Debenture
(CUSIP No.____) held through the Depository by or on behalf of ____________ as
beneficial owner (the "Transferor"). The Transferor has requested an exchange
or transfer of its interest for an interest in the Permanent Regulation S
Debenture (CUSIP (CINS) No. [____]) to be held by [Euroclear][Cedel] (ISIN Code
_______) (Common Code) through the Depositary.

         In connection with such request and in respect of such Debentures, the
Transferor does hereby certify that such exchange or transfer has been effected
in accordance with the transfer restrictions set forth in the Debentures and
that, with respect to transfers made in reliance on Regulation S under the
Securities Act:

         (1)      the offer of the Debentures was not made to a person in the
                  United States;

         (2)      either:  (A)      at the time the buy order was originated,
                                    the transferee was outside the United States
                                    or the Transferor and any person acting on
                                    its behalf reasonably believed that the
                                    transferee was outside the United States, or

                           (B)      the transaction was executed in, on or
                                    through the facilities of, a designated
                                    offshore securities market and neither the
                                    Transferor nor any person acting on its
                                    behalf knows that the transaction was
                                    pre-arranged with a buyer in the United
                                    States;

         (3)      no directed selling efforts have been made in contravention
                  of the requirements of Rule 903(b) or 904(b) of Regulation S,
                  as applicable; and



                                      C-1





<PAGE>   35






         (4)      the transaction is not part of a plan or scheme to evade the
                  registration requirements of the Securities Act.

         This Certificate and the statements contained herein are made for your
benefit and the benefit of the Company and the initial purchaser of the
Debentures being exchanged or transferred. Terms used in this Certificate and
not otherwise defined in the Indenture have the meanings set forth in
Regulation S under the Securities Act.

                                       [Insert Name of Transferor]



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


Dated:
       -----------------------------



cc:      Liberty Media Corporation




                                      C-2

<PAGE>   36






                                                                     EXHIBIT D





                  FORM OF TRANSFER CERTIFICATE FOR TRANSFER OR
                 EXCHANGE FROM TEMPORARY REGULATION S DEBENTURE
                             TO RULE 144A DEBENTURE


The Bank of New York
101 Barclay Street
Floor 21 West
New York, New York  10286

                  Re:      Liberty Media Corporation
                           $750,000,000 3 3/4% Senior Exchangeable Debentures
                           due 2030 (the "Debentures")

         Reference is hereby made to the Indenture dated as of July 7, 1999
between THE BANK OF NEW YORK (the "Trustee") and LIBERTY MEDIA CORPORATION (the
"Company") (as supplemented by the Fourth Supplemental Indenture, dated as of
February 10, 2000, between the Company and the Trustee, the "Indenture").
Capitalized terms not defined in this Certificate shall have the meanings given
to them in the Indenture.

         This Certificate relates to ______________________________________
Original Principal Amount of Debentures which are held in the form of the
Temporary Regulation S Debenture (CUSIP No. ___) with [Euroclear/Cedel] (ISIN
Code [___]) (Common Code [___]) through the Depository by or on behalf of
_____________ as beneficial owner (the "Transferor"). The Transferor has
requested an exchange or transfer of its interest in the Debentures for an
interest in the Rule 144A Debenture (CUSIP NO. [___]).

         In connection with such request, and in respect of such Debentures,
the Transferor does hereby certify that such transfer is being effected in
accordance with the transfer restrictions set forth in the Indenture and
pursuant to and in accordance with Rule 144A under the United States Securities
Act of 1933, as amended (the "Securities Act"), to a transferee that the
Transferor reasonably believes is purchasing the Debentures for its own account
or an account with respect to which the transferee exercises sole investment
discretion and the transferee and any such account is a "qualified
institutional buyer" within the meaning of Rule 144A, in each case in a
transaction meeting the requirements of Rule 144A and in accordance with any
applicable securities laws of any state of the United States or any other
jurisdiction.

         This Certificate and the statements contained herein are made for your
benefit and the benefit of the Company and the initial purchaser of the
Debentures being transferred.

                                       [Insert Name of Transferor]


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




Dated:
       ----------------------------

cc:      Liberty Media Corporation



                                      D-1




<PAGE>   37




                                                                     EXHIBIT E


                      FORM OF CLEARING SYSTEM CERTIFICATE


                  Re:      Liberty Media Corporation
                           $750,000,000 3 3/4% Senior Exchangeable Debentures
                           due 2030 (the "Debentures")


         Reference is hereby made to the Indenture dated as of July 7, 1999
between THE BANK OF NEW YORK (the "Trustee") and LIBERTY MEDIA CORPORATION (the
"Company") (as supplemented by the Fourth Supplemental Indenture, dated as of
February 2, 2000, between the Company and the Trustee, the "Indenture").
Capitalized terms not defined in this Certificate shall have the meanings given
to them in the Indenture.

         This is to certify that, based solely on certifications we have
received in writing, by tested telex or by electronic transmission from member
organizations appearing in our records as persons being entitled to a portion of
the principal amount set forth below (our "Member Organizations") substantially
to the effect set forth in the Indenture, as of the date hereof, $___________
aggregate Original Principal Amount of Debentures represented by the Temporary
Regulation S Global Debenture is owned by (a) non-U.S. Persons or (b) U.S.
Persons who purchased such Debentures in transactions that did not require
registration under the United States Securities Act of 1933, as amended (the
"Securities Act"). As used in this paragraph, the term "U.S. Person" has the
meaning given to it by Regulation S under the Securities Act.(1)

         We further certify (i) that we are not making available herewith for
payment of interest any portion of a Temporary Regulation S Global Debenture
excepted in such certifications and (ii) that as of the date hereof we have not
received any notification from any of our Member Organizations to the effect
that the statements made by such Member Organizations with respect to any
portion of the Temporary Regulation S Global Debenture submitted herewith for
payment of interest are no longer true and cannot be relied upon as the date
hereof.




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

(1)      Note: Unless Morgan Guaranty Brussels and Cedelbank are otherwise
         informed by the Initial Purchaser or the Trustee, the Standard
         Long-Form Certification set out in the Operating Procedures of
         Euroclear will be deemed to meet the requirements of this sentence.




                                      E-1





<PAGE>   38




         We understand that this certification is required in connection with
certain securities laws of the United States. In connection therewith, if
administrative or legal proceedings are commenced or threatened in connection
with which this certification is or would be relevant, we irrevocably authorize
you to produce this certification to any interested party in such proceedings.

                                 Yours faithfully,


                                 [MORGAN GUARANTY TRUST COMPANY OF
                                 NEW YORK, Brussels office, as
                                 operator of the Euroclear System]
                                 or
                                 [CEDELBANK]



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


       --------------------(2)
Dated:











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


(2)      Not earlier than 15 days prior to the relevant Interest Payment Date
         or Redemption Date, as the case may be.





                                      E-2






<PAGE>   39




                                                                      EXHIBIT F


                  FORM OF CERTIFICATE OF BENEFICIAL OWNERSHIP

                  Re:      Liberty Media Corporation
                           $750,000,000 3 3/4% Senior Exchangeable Debentures
                           due 2030 (the "Debentures")

         Reference is hereby made to the Indenture dated as of July 7, 1999
between THE BANK OF NEW YORK (the "Trustee") and LIBERTY MEDIA CORPORATION (the
"Company") (as supplemented by the Fourth Supplemental Indenture, dated as of
February 10, 2000, between the Company and the Trustee, the "Indenture").
Capitalized terms not defined in this Certificate shall have the meanings given
to them in the Indenture.

         This is to certify that as of the date hereof, and except as set forth
below, the above-captioned Securities held by you for our account are
beneficially owned by (a) non-U.S. person(s) or (b) U.S. person(s) who
purchased the Debentures in transactions which did not require registration
under the Securities Act of 1933, as amended (the "Act"). As used in this
paragraph, the term "U.S. person" has the meaning given to it by Regulation S
under the Securities Act.

         We undertake to advise you promptly by tested telex or by electronic
transmission on or prior to the date on which you intend to submit your
certification relating to the Debentures held by you for our account in
accordance with your operating procedures if any applicable statement herein is
not correct on such date, and in the absence of any such notification it may be
assumed that this certification applies as of such date.

         This certification excepts and does not relate to $______________ of
such interest in the above Debentures in respect of which we are not able to
certify and as to which we understand exchange and delivery of definitive
Debentures (or, if relevant, exercise of any rights or collection of any
interest) cannot be made until we do so certify.





                                      F-1


<PAGE>   40






         We understand that this certification is required in connection with
certain securities laws of the United States. In connection therewith, if
administrative or legal proceedings are commenced or threatened in connection
with which this certification is or would be relevant, we irrevocably authorize
you to produce this certification to any interested party in such proceedings.


Date:                  (3)
      -----------------                      By:
                                                  -----------------------------

         As, or as agent for, the beneficial owner(s) of the Debentures to
which this certificate relates.






------------------------
(3)      Not earlier than 15 days prior to the certification event to which the
         certification relates.



                                      F-2




<PAGE>   41




                                                                      EXHIBIT G




                          [FORM OF NOTICE OF EXCHANGE]



The Bank of New York
101 Barclay Street
New York, NY 10286


                  Re:      $750,000,000 3 3/4% Senior Exchangeable
                           Debentures due 2030 (the "Debentures")


Gentlemen:


         The undersigned Holder of debentures hereby gives notice of its
intention to exchange $______________ aggregate Original Principal Amount of
Debentures. This notice, once delivered to the Exchange Agent, is irrevocable.

         If Reference Shares or any other securities are to be delivered as
part of this exchange, they should be delivered to:


         If cash is to be paid as part of this exchange, it should be sent to:


         Any communication to the Holder in connection with this exchange
should be directed to:





                                             Very truly yours,

                                             [Name of Holder]


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




Date of Notice of Exchange:


                                      G-1