Document:

<PAGE>   1
                                                                    EXHIBIT 10.2

"[ * ]" = omitted, confidential material, which material has been separately
filed with the Securities and Exchange Commission pursuant to a request for
confidential treatment.

                     SETTLEMENT AGREEMENT AND MUTUAL RELEASE

THIS SETTLEMENT AGREEMENT AND MUTUAL RELEASE is dated as of this 17th day of
March, 2000, and is by and between ALPHA 1 BIOMEDICALS, INC. ("Alpha1"), a
Delaware corporation, and BACHEM BIOSCIENCE INC. ("Bachem"), a Delaware
corporation.

WHEREAS:

1.      Alpha1 is currently indebted to Bachem in the amount of approximately
        US$543,000 plus simple interest accruing from August 1, 1999 to the
        present (the "Indebtedness");

2.      Bachem is in the process of manufacturing [ * ] grams of GMP Thymosin
        Beta 4 ("Product") for the account of Alpha1; and

3.      Alpha1 and Bachem desire to settle and discharge the Indebtedness and
        provide for Alpha1 to purchase Product on the terms and conditions
        hereinafter set forth.

NOW, THEREFORE, in consideration of the foregoing and for other good and
valuable consideration, the receipt of which is hereby acknowledged, the parties
agree as follows:

1.      Bachem does hereby forever release and discharge Alpha1 from any and all
        actions, causes of action, damages, judgments, liabilities, obligations,
        claims and demands of any kind or nature whatsoever, whether in law or
        in equity, whether known or unknown, which it now has or which it
        hereafter may have, for or by reason of any matter arising out of or in
        connection with the circumstances relating to the Indebtedness, other
        than those obligations arising under this Settlement Agreement and
        Mutual Release.

2.      Alpha1 does hereby forever release and discharge Bachem from any and all
        actions, causes of action, damages, judgments, liabilities, obligations,
        claims and demands of any kind or nature whatsoever, whether in law or
        in equity, whether known or unknown, which it now has or which it
        hereafter may have, for or by reason of any matter arising out of or in
        connection with the circumstances relating to Indebtedness, other than
        those obligations arising under this Settlement Agreement and Mutual
        Release.

3.      In further consideration of, and as a further inducement for, the
        foregoing mutual releases, the parties agree as follows:

        a.     Immediately upon the execution of this Mutual Release, Alpha1
               shall pay to Bachem the sum of US$125,000 (the "Settlement
               Amount") by wire transfer of same day, cash available funds to an
               account designated in writing by Bachem.

        b.     Immediately upon the execution of this Mutual Release, Alpha1
               shall pay to Bachem the sum of US$50,000 (the "Down Payment") by
               wire transfer of same day, cash available funds to an account
               designated in writing by Bachem, as an advance against the
               Initial Order Purchase Price (as hereinafter defined).

<PAGE>   2

        c.     Within thirty (30) days after Alpha1 is granted an exclusive
               license (the "License") from the National Institutes of Health
               ("NIH") to certain rights pertaining to the use of Thymosin Beta
               4, Alpha1 will place an order (the "Initial Order") with Bachem
               for [ * ]grams of Product at a price of US[ * ] per gram, or
               US$100,000 in the aggregate (the "Initial Order Purchase Price").

        d.     Contemporaneously with the placement of the Initial Order, Alpha1
               will tender the balance of the Initial Order Purchase Price (the
               "Balance Payment") of US$50,000 to Silver, Freedman & Taff,
               L.L.P., as Escrow Agent, by wire transfer of same day, cash
               available funds to an account to be designated in writing by the
               Escrow Agent. Interest, if any, earned on funds held by the
               Escrow Agent pursuant to this Settlement Agreement and Mutual
               Release, shall accrue to the benefit of Alpha1.

        e.      Upon Alpha1's receipt of the Initial Order of Product and its
                acceptance thereof, Alpha1 shall instruct the Escrow Agent to
                release the Balance Payment to Bachem. For the purpose hereof,
                acceptance shall be deemed to have occurred when Alpha1 receives
                the full amount of the Initial Order of Product and the Product
                meets or exceeds the Specifications set forth on EXHIBIT A
                hereto. If Alpha1 has received the full amount of the Initial
                Order of Product, but it does not meet or exceed the
                Specifications, then Alpha1 shall so notify Bachem within thirty
                (30) days of Alpha1's receipt of the full amount of the Initial
                Order of Product. If Alpha1 does not notify Bachem within thirty
                (30) days of Alpha1's receipt of the full amount of the Initial
                Order of Product that the Product does not meet or exceed the
                Specifications, then the Initial Order of Product will be deemed
                to have been accepted by Alpha1. If Alpha1 timely notifies
                Bachem in writing that the Product does not meet or exceed the
                Specifications, and if Bachem contests that determination in a
                written notice to Alpha1 within ten (10) calendar days after
                Alpha1's notice is given, then the parties shall appoint a
                mutually-agreeable, qualified independent laboratory (the
                "Laboratory") to test the Product for compliance with the
                Specifications. If the Laboratory concludes in a written report
                delivered to the parties and to the Escrow Agent that the
                Product meets or exceeds the Specifications, then (i) such
                determination shall be final, (ii) the Escrow Agent shall
                release the Balance Payment to Bachem, and (iii) Alpha1 shall be
                solely responsible for the Laboratory's fees. If the Laboratory
                concludes in a written report delivered to the parties and to
                the Escrow Agent that the Product does not meet or exceed the
                Specifications, then (i) such determination shall be final, (ii)
                Bachem shall be solely responsible for the Laboratory's fees,
                and (iii) the Escrow Agent shall retain the Balance Payment
                until such time as Alpha1 receives the full amount of the
                Initial Order of Product and the Product meets or exceeds the
                Specifications.

        f.      The Escrow Agent shall hold and disburse the Balance Payment in
                accordance with the terms of the Escrow Agreement, attached
                hereto as EXHIBIT B.

"[ * ]" = omitted, confidential material, which material has been separately
filed with the Securities and Exchange Commission pursuant to a request for
confidential treatment.

        g.     Bachem agrees to sell to Alpha1, at such time and in such
               quantities as Alpha1 may request, up to an additional [ * ] grams
               of Product at a price of US[ * ] per gram
<PAGE>   3

                and upon such other terms as the parties shall mutually agree.
                To avoid misunderstanding, the foregoing sentence gives Alpha1
                the right to purchase up to an additional [ * ] grams of
                Product, but does not impose an obligation on Alpha1 to do so.

        h.      For Alpha1's requirements of Product in excess of [ * ] grams,
                Alpha1 shall recognize Bachem as a preferred (but not exclusive)
                supplier of Product, and Bachem agrees to sell Product to Alpha1
                upon such pricing and other terms as the parties shall mutually
                agree.

4.      The releases set forth in Paragraphs 1 and 2 above shall become
        effective only upon the payment of the Settlement Amount and the Down
        Payment by Alpha1 to Bachem in accordance with Paragraphs 3.a and 3.b
        above. In the event NIH has not granted the License to Alpha1 within the
        two (2) year period beginning on the date of this Settlement Agreement
        and Mutual Release, then Alpha1 hereby agrees to nevertheless purchase
        the Initial Order on the terms set forth in Paragraphs 3.c, 3.d, 3.e and
        3.f above.

5.      It is the intention of the parties in executing this Settlement
        Agreement and Mutual Release and in providing the consideration
        acknowledged and/or required by this Settlement Agreement and Mutual
        Release that this Settlement Agreement and Mutual Release is a full,
        final, mutual and complete release of and from the matters referred to
        Paragraphs 1 and 2 above.

6.      All notices, requests, demands and other communications between the
        parties shall be in writing and shall be deemed to have been duly given
        (a) if personally delivered and a receipt obtained therefor, then on the
        date and at the time of delivery, (b) if mailed by certified or
        registered mail, postage prepaid, return receipt requested, then three
        (3) business days after mailing, (c) if by overnight courier, then on
        the date following the date given to the courier firm, or (d) if
        transmitted by fax, then on the date of transmission (but only if the
        sending fax machine produces a confirmation that the fax machine to
        which the notice was sent received the fax), to the parties at the
        following addresses or fax numbers (or such other addresses or fax
        numbers which shall be given in writing by either party to the other):

               If to Alpha1:        Alpha 1 Biomedicals, Inc.
                                    3 Bethesda Metro Center
                                    Suite 700
                                    Bethesda, Maryland 20814
                                    Fax: (301) 961-1991

"[ * ]" = omitted, confidential material, which material has been separately
filed with the Securities and Exchange Commission pursuant to a request for
confidential treatment.

               If to Bachem:        Bachem Bioscience Inc.
                                    3700 Horizon Drive
                                    King of Prussia, Pennsylvania 19406
                                    Fax: (610) 239-0800

                                      -3-
<PAGE>   4

7.      This Settlement Agreement and Mutual Release shall inure to the benefit
        of each party's officers, directors, stockholders and employees, their
        respective heirs, administrators, personal representatives and
        executors, and the Company's successors and assigns.

8.      This Settlement Agreement and Mutual Release may be amended only by an
        instrument in writing signed by all of the parties hereto.

9.      This Mutual Release shall be construed and governed by the laws of the
        State of Maryland without regard to its conflict of law rules. If any
        provision of this Mutual Release is held to be invalid or unenforceable,
        such invalidity or unenforceability will not affect the validity or
        enforceability of the other provisions of this Mutual Release, the other
        provisions of this Mutual Release shall be enforced as fully as
        possible, and the unenforceable provision shall be deemed modified to
        the limited extent required to permit its enforcement in a manner most
        closely approximating the intention of the parties as expressed herein.

10.     This Settlement Agreement and Mutual Release may be executed
        simultaneously in one or more counterparts, each of which shall be
        deemed an original, but all of which together will constitute one and
        the same instrument.

11.     Each of the parties agrees to execute all further instruments and
        documents and to take all further action as the other party may
        reasonably request in order to give effect to the terms and purpose of
        this Settlement Agreement and Mutual Release.

12.     Each person executing this Settlement Agreement and Mutual Release on
        behalf of a party to this Settlement Agreement and Mutual Release
        represents and warrants that he or she is duly authorized to do so on
        behalf of such party.

                                      -4-
<PAGE>   5

IN WITNESS WHEREOF, this Settlement Agreement and Mutual Release has been
executed by the parties, the corporate party acting through its duly authorized
officers, as of the date and year first above written.

                                      ALPHA1:

                                      ALPHA 1 BIOMEDICALS, INC.

                                      By:    /s/ Allan L. Goldstein
                                             -----------------------------------
                                             Allan L. Goldstein,
                                             Chief Executive Officer

                                      BACHEM:

                                      BACHEM BIOSCIENCE INC.

                                      By:    /s/ Thomas Fruh
                                             -----------------------------------
                                             Thomas Fruh, Vice President and
                                             Chief Operating Officer

                                      -5-
<PAGE>   6

                                    EXHIBIT A

                             PRODUCT SPECIFICATIONS

                                 (See attached)

<PAGE>   7

[   *   ]

"[ * ]" = omitted, confidential material, which material has been separately
filed with the Securities and Exchange Commission pursuant to a request for
confidential treatment.

<PAGE>   8

                                    EXHIBIT B

                                ESCROW AGREEMENT

                                 (See Attached)

<PAGE>   9

                                ESCROW AGREEMENT

        This Escrow Agreement (this "Agreement") dated this 17th day of March,
2000, by and among ALPHA 1 BIMEDICALS, INC. ("Alpha1"), a Delaware corporation,
BACHEM BIOSCIENCE INC. ("Bachem"), a Delaware corporation, and SILVER, FREEDMAN
& TAFF, L.L.P. (hereinafter referred to as "Escrow Agent"), a registered limited
liability partnership located in Washington, D.C.

                              W I T N E S S E T H:

        WHEREAS, Alpha1 and Bachem are parties to that certain Settlement
Agreement and Mutual Release of even date herewith, (the "Settlement
Agreement"), pursuant to which Alpha1 has agreed to purchase a certain quantity
of Product, as such term is defined in the Settlement Agreement;

        WHEREAS, in accordance with the terms of the Settlement Agreement, the
Balance Payment, as such term is defined in the Settlement Agreement, is to be
delivered to the Escrow Agent and held and disbursed by the Escrow Agent in
accordance with the terms of this Escrow Agreement;

        WHEREAS, Alpha1 and Bachem desire that Silver, Freedman & Taff, L.L.P.
act as the Escrow Agent hereunder, and Silver, Freedman & Taff, L.L.P. is
willing to act as said Escrow Agent, upon the terms and conditions hereafter set
forth; and

        WHEREAS, capitalized terms used in this Escrow Agreement shall have the
meanings ascribed to them in the Settlement Agreement unless otherwise defined
herein.

        NOW, THEREFORE, the parties hereto, intending to be legally bound, agree
as follows:

        1.      Appointment of Escrow Agent. Alpha1 and Bachem hereby appoint
Silver, Freedman & Taff, L.L.P. as the Escrow Agent to accept, hold and disburse
the Balance Payment in accordance with the terms of this Agreement. The Escrow
Agent accepts the appointment and the responsibilities set forth in this
Agreement. Bachem acknowledges that the Escrow Agent is counsel to Alpha1 and
that the Escrow Agent has represented Alpha1 in connection with the transactions
contemplated by this Agreement and the Settlement Agreement. Bachem hereby
waives any actual or apparent conflict of interest that may exist by reason of
the Escrow Agent's serving as such counsel and as the escrow agent under this
Agreement. Bachem agrees that the Escrow Agent may hereafter serve as counsel to
Alpha1 in connection with any dispute that may hereafter arise in connection
with this Agreement, the Settlement Agreement and/or the transactions
contemplated hereby and thereby.

        2.      Duties of Escrow Agent.

                (a)     Upon receipt, the Escrow Agent shall place the Balance
Payment in a segregated, interest-bearing account at First Union National Bank
of Washington, D.C. (the

<PAGE>   10

"Depositary"), under the name of "Alpha 1 Biomedicals, Inc. - Silver, Freedman &
Taff, L.L.P., Escrow Agent" (hereinafter referred to as the "Escrow Account").
The Escrow Account will be otherwise identified by Alpha1's employer
identification number, 52-1253406, and Alpha1 will execute and deliver to the
Escrow Agent an IRS Form W-9, in the form attached hereto as EXHIBIT A,
verifying its employer identification number and stating that it is not subject
to backup withholding. There shall be no obligation or duty on the part of the
Escrow Agent to determine the nature or purpose of any funds delivered to it. To
the contrary, the Escrow Agent is excused from any such obligation or duty, and
shall deposit in the Escrow Account any funds made payable thereto without
requirement of independent verification or certification.

                (b)     Only the Escrow Agent or its designated
representative(s) shall have signature authority over the Escrow Account.

                (c)     Upon establishing the Escrow Account, the Escrow Agent
shall request that the Depositary send a copy of each periodic statement of the
Escrow Account to Alpha1.

                (d)     The Balance Payment shall hereinafter be referred to as
the Escrow Funds, and the interest earned thereon shall hereinafter be referred
to as the Escrow Interest.

                (e)     The Escrow Agent shall continue to hold and maintain the
Escrow Funds and the Escrow Interest in the Escrow Account until authorized
under Paragraph 3 of this Agreement to distribute and disburse same.

        3.      Distributions from the Escrow Account.

                (a)     The Escrow Agent shall release and disburse any Escrow
Interest to Alpha1 at any time upon receipt of a written request from Alpha1.

                (b)     The Escrow Agent shall release and disburse the Escrow
Funds to Bachem and any Escrow Interest to Alpha1 upon either to occur of the
following events:

                        (i)     the Escrow Agent receives instructions from
Alpha1 to release the Balance Payment to Bachem; or

                        (ii)    the Escrow Agent receives a report from the
Laboratory that Initial Order of Product meets or exceeds Specifications.

                (c)     The Escrow Agent shall release and disburse the Escrow
Funds and any Escrow Interest to Alpha1 upon either to occur of the following
events:

                        (i)     Receipt from either Alpha1 or Bachem of Bachem's
written notice that it is unable to produce the Initial Order of Product so that
it meets or exceeds Specifications; or

                                      -2-
<PAGE>   11

                        (ii)    The passage of six (6) months from the Escrow
Agent's receipt of the Escrow Funds.

                (d)     Effect of Complete Disbursement of Escrow Funds. Upon
the complete and final distribution by the Escrow Agent of all of the Escrow
Funds and the Escrow Interest, this Agreement shall terminate and the parties
shall be relieved of all further obligations hereunder.

        4.     Obligations of the Escrow Agent.

                (a)     The Escrow Agent undertakes to perform only such duties
as are specifically set forth herein and shall not be bound in any way by any
agreement or contract between Alpha1 and Bachem (whether or not the Escrow Agent
has knowledge thereof). The Escrow Agent, acting or refraining from acting in
good faith, shall not be liable for any mistake of fact or error of judgment by
it or for any acts or omissions by it of any kind unless caused by willful
misconduct or gross negligence. The Escrow Agent shall be entitled to rely upon
the advice of counsel (which may be of the Escrow Agent's own choosing). The
Escrow Agent shall have no responsibility for the contents of any writing
submitted to it hereunder and shall be entitled in good faith to rely without
any liability upon the contents thereof and may assume that any person
purporting to give any such writing in connection with the provisions of this
Agreement has been duly authorized to do so.

                (b)     In the event any property held by the Escrow Agent
hereunder shall be attached, garnished or levied upon under any court order, or
if the delivery of such property shall be stayed or enjoined by any court order,
or if any court order, judgment or decree shall be made or entered affecting
such property or affecting any act by the Escrow Agent, the Escrow Agent may, in
its sole discretion, obey and comply with all writs, orders, judgments or
decrees so entered or issued, whether with or without jurisdiction,
notwithstanding any provision of this Agreement to the contrary. If the Escrow
Agent obeys and complies with any such writs, orders, judgments or decrees, and
if the Escrow Agent shall have given prompt written notification to Alpha1 and
Bachem, it shall not be liable to any of the parties hereto or to any other
person, firm or corporation, by reason of such compliance, notwithstanding that
such writs, orders, judgments or decrees may be subsequently reversed, modified,
annulled, set aside or vacated.

                (c)     The Escrow Agent makes no representation as to the
validity, value, genuineness or the collectibility of any check, draft or other
instrument deposited to the Escrow Account.

        5.      Resignation of Escrow Agent. The Escrow Agent may resign and be
discharged from its duties hereunder at any time by giving notice of such
resignation to Alpha1 and Bachem specifying a date (not less than thirty (30)
days after the giving of such notice) when such resignation shall take effect.
Promptly after such notice, a successor escrow agent shall be appointed by
Alpha1 and Bachem upon the resignation date specified in such notice. If no
successor escrow agent shall have been so appointed, or if an appointed
successor escrow agent has not accepted such appointment, within thirty (30)
days after the retiring Escrow Agent's giving of notice of resignation, then the
retiring Escrow Agent may either (a) on behalf of the parties hereto, appoint a
successor escrow agent, which shall be a commercial bank organized under the
laws of the United States of

                                      -3-
<PAGE>   12

America or of any State thereof and having a combined capital and surplus of at
least $250,000,000.00; or (b) at the expense of Alpha1 and Bachem, petition any
court of competent jurisdiction for the appointment of a successor escrow agent.

        6.      Expenses of Escrow Agent. The Escrow Agent shall not be entitled
to any fees for serving as Escrow Agent hereunder. The Escrow Agent shall,
however, be entitled to reimbursement from Alpha1 for any expenses incurred in
connection with its acting as Escrow Agent. The Escrow Agent may deduct its
expenses directly from the Escrow Interest, and it shall send a copy of its
invoice for any such expenses to Alpha1.

        7.      Termination and Amendment. This Agreement shall terminate at
such time as the entire Escrow Fund and Escrow Interest shall have been
distributed and disbursed in accordance with the provisions of this Agreement.
Except for the right of the Escrow Agent to resign pursuant to Paragraph 5
hereinabove, this Agreement cannot be terminated, altered or amended except
pursuant to an instrument in writing signed by Alpha1, Bachem and the Escrow
Agent.

        8.      Notices. All notices, requests, demands and other communications
hereunder shall be in writing and shall be deemed to have been duly given as
provided for in the Settlement Agreement. Notices to the Escrow Agent shall be
sent or delivered to Silver, Freedman & Taff, L.L.P., 1100 New York Avenue,
N.W., Seventh Floor, Washington, D.C. 20005, Attention: Sidney J. Silver,
Esquire; Fax No. (202) 682-0354..

        9.      Miscellaneous. This Agreement (a) shall be construed and
governed by the laws of the State of Maryland without regard to its conflict of
law rules; (b) shall inure to the benefit of and shall be binding upon the
parties hereto and their respective successors and assigns; (c) may be executed
in one or more counterparts, each of which shall be deemed an original, but all
of which together shall constitute the one and the same agreement; and (d)
contains section headings for reference purposes only which are not to be
construed as part of the Agreement.

            (The remainder of this page is intentionally left blank.)

                                      -4-
<PAGE>   13

        IN WITNESS WHEREOF, this Agreement has been executed by the parties, the
corporate parties by its duly authorized officers, as of the date and year first
above written.

                                     ALPHA1:

                                     ALPHA 1 BIOMEDICALS, INC.

                                     By:    /s/ Allan L. Goldstein
                                            ------------------------------------
                                            Allan L. Goldstein,
                                            Chief Executive Officer

                                     BACHEM:

                                     BACHEM BIOSCIENCE INC.

                                     By:    /s/ Thomas Fruh
                                            ------------------------------------
                                            Thomas Fruh, Vice President and
                                            Chief Operating Officer

                                     ESCROW AGENT:

                                     SILVER, FREEDMAN & TAFF, L.L.P.

                                     By:    /s/ Sidney J. Silver
                                            ------------------------------------
                                            Sidney J. Silver, Partner

                                      -5-
<PAGE>   14

                                    EXHIBIT A

                                  IRS Form W-9

                                 (See Attached)<PAGE>   1
                             Confidential Treatment

Note: Certain material has been omitted from this document pursuant to a request
for confidential treatment and has been filed separately with the SEC. Notations
of [REDACTED]* have been used to indicate such an omission.

                                                                   EXHIBIT 10.25

                              AMENDMENT AND CONSENT

               AMENDMENT AND CONSENT, dated as of March 30, 2001, to the CREDIT
AGREEMENT, dated as of July 2, 1998 (the "Credit Agreement"), among Teligent,
Inc., a Delaware corporation (the "Borrower"), the Lenders from time to time
parties thereto, Goldman Sachs Credit Partners L.P., as Syndication Agent,
Toronto Dominion (Texas), Inc., as Documentation Agent, and The Chase Manhattan
Bank, as Administrative Agent.

                            W I T N E S S E T H :

               WHEREAS, each of the Lenders is a party to the Credit Agreement
pursuant to which the Borrower may borrow from time to time Optional Term Loans
in an aggregate face amount of up to $400,000,000 (the "Original Optional Term
Facility Amount"); and

               WHEREAS, the Borrower wishes to increase the Original Optional
Term Facility Amount from $400,000,000 up to $600,000,000 (as so increased, the
"New Optional Term Facility Amount"); and

               WHEREAS, the Borrower wishes to utilize a portion, not in excess
of $350,000,000, of the New Optional Term Facility Amount as an optional vendor
financing facility; and

               WHEREAS, the Borrower wishes to allow certain vendors to the
Borrower to become parties to the Credit Agreement from time to time after the
Effective Date (as defined below) until December 31, 2001; and

               WHEREAS, the parties have agreed to modify certain of the
covenants and other terms in the Credit Agreement as set forth herein;

               NOW, THEREFORE, the Borrower, the Administrative Agent, and the
Required Prepayment Lenders hereby agree as follows:

               1.    Defined Terms. Capitalized terms used herein without
definition shall have the meaning ascribed to such terms in the Credit
Agreement.

               2.    Amendment to Section 1.1 - Defined Terms. (a) The following
definitions are hereby amended so that they shall read in their entirety
respectively as follows:

               "Applicable Margin": (a) for Tranche A Term Loans, Delayed Draw
               Term Loans, Conversion Term Loans and Revolving Credit Loans,
               [REDACTED] per annum, in the case of Eurodollar Loans, and
               [REDACTED], in the case of ABR Loans, and (b) for each Type of
               Optional Term Loans of each Tranche, the rate per annum for such
               Tranche and Type determined in accordance with the Optional Term
               Loan Amendment executed for such Tranche pursuant to Section 2.7.

<PAGE>   2
               "Asset Sale": (i) any Disposition of Non-Core Assets (excluding
               any such Disposition permitted by clause (a), (b), (d), (e) or
               (g) of Section 6.5) and (ii) the entering into of one or more
               management agreements with respect to spectrum by any Restricted
               Subsidiary to any Unrestricted Subsidiary or other Person;
               provided, that such agreements are (A) compliant with all
               material terms of this Agreement as determined by the
               Administrative Agent in good faith (including, without
               limitation, that all Net Cash Proceeds of such management
               agreement shall be applied in accordance with Section 2.13) and
               (B) reasonably satisfactory in form and substance to FCC counsel
               to the Lenders.

               "Consolidated Cash Interest Expense": for any fiscal quarter,
               total cash interest expense (including that attributable to
               Capital Lease Obligations) of the Borrower and its Restricted
               Subsidiaries to be paid during such fiscal quarter (including,
               without limitation, all commissions, discounts and other fees and
               charges owed with respect to letters of credit and bankers'
               acceptance financing and net costs under hedge agreements in
               respect of interest rates to the extent such net costs are
               allocable to such fiscal quarter in accordance with GAAP) as
               reasonably determined by the Borrower on the basis of (i) the
               aggregate amount of Indebtedness of the Borrower and its
               Restricted Subsidiaries outstanding on the first day of such
               fiscal quarter and (ii) interest rates applicable to such
               Indebtedness on such date.

               "Consolidated Fixed Charge Coverage Ratio": (a) from the
               Amendment Effective Date through the fiscal quarter ending
               September 30, 2003, on the last day of any fiscal quarter, the
               ratio of (i) the amount of Consolidated EBITDA required pursuant
               to Section 6.1(k) for the fiscal quarter immediately following
               such last day, to the extent that Consolidated EBITDA for such
               fiscal quarter is negative, plus the sum of (A) the amount of
               cash and Cash Equivalents held by the Borrower and its Restricted
               Subsidiaries, (B) the Available Revolving Credit Commitments, (C)
               the Available Tranche A Term Loan Commitments, (D) the Available
               Delayed Draw Term Loan Commitments, and (E) any available unused
               Optional Non-Vendor Loan Commitments, in each case, determined as
               of such last day to (ii) Consolidated Fixed Charges for the
               fiscal quarter immediately following such last day and (b) from
               the fiscal quarter ending December 31, 2003 and thereafter, for
               any period of four consecutive fiscal quarters, the ratio of (i)
               Consolidated EBITDA for such period plus the sum of (A) the
               Available Revolving Credit Commitments, (B) the Available Tranche
               A Term Loan Commitments, (C) the Available Delayed Draw Term Loan
               Commitments, and (D) any available unused Optional Non-Vendor
               Term Loan Commitments, in each case, determined as of the last
               day of such period of four consecutive fiscal quarters to (ii)
               Consolidated Fixed Charges for such period of four consecutive
               fiscal quarters.

               "Consolidated Fixed Charges": (a) from the Amendment Effective
               Date through the fiscal quarter ending September 30, 2003, for
               any fiscal quarter, the sum (without duplication) of (i)
               Consolidated Cash Interest Expense for such fiscal quarter, (ii)
               projected cash income taxes to be paid by the Borrower or any of
               its Restricted Subsidiaries on a consolidated basis in respect of
               such fiscal quarter, (iii) preferred dividends required to be
               paid in cash in such fiscal quarter and (iv)

                                       2
<PAGE>   3

               scheduled payments to be made during such fiscal quarter on
               account of principal of Indebtedness of the Borrower or any of
               its Restricted Subsidiaries and (b) from the fiscal quarter
               ending December 31, 2003 and thereafter, for any period of four
               consecutive fiscal quarters, the sum (without duplication) of (i)
               Consolidated Cash Interest Expense for such period, (ii)
               provision for cash income taxes made by the Borrower or any of
               its Restricted Subsidiaries on a consolidated basis in respect of
               such period and (iii) scheduled payments made during such period
               on account of principal of Indebtedness of the Borrower or any of
               its Restricted Subsidiaries.

               "Consolidated Secured Debt": all Consolidated Total Debt,
               excluding the Convertible Notes, secured pursuant to the Security
               Documents or by any other security interest in any assets of the
               Borrower or any of its Restricted Subsidiaries.

               "Default": any of the events specified in Section 7, whether or
               not any requirement for the giving of notice, the lapse of time,
               or both, has been satisfied.

               "Existing Affiliate Transactions": (a) transactions pursuant to
               the Administrative Services Agreement, dated as of March 5, 1996,
               between the Borrower (formerly DMT, LLC) and Microwave Services,
               Inc., a Subsidiary of Associated Group, Inc. as in effect on the
               date hereof, and as such agreement may be amended from time to
               time in a manner no less favorable to the Lenders, (b)
               transactions pursuant to the Technical Services Agreement, dated
               as of October 22, 1997, between the Company and NTT America, Inc.
               as in effect on the date hereof, and as such agreement may be
               amended from time to time in a manner no less favorable to the
               Lenders, (c) transactions pursuant to the Stockholders Agreement,
               dated as of November 26, 1997, between the Borrower, NTT America,
               Inc. and certain other stockholders of the Borrower as in effect
               on the date hereof and as such agreement may be amended from time
               to time in a manner no less favorable to the Lenders, (d)
               transactions pursuant to the Shareholders Agreement, dated
               January 13, 2000, by and among Alex J. Mandl, Liberty Media
               Corporation, Telcom-DTS Investors, L.L.C. and Microwave Services,
               Inc. as in effect on the date hereof and as such agreement may be
               amended from time to time in a manner no less favorable to the
               Lenders, (e) transactions pursuant to the Joint Venture
               Agreement, dated April 11, 2000, by and between Teligent
               International Ltd., Telcom Ventures LLC, BA Investments, Ltd.,
               and Argentina Telecom Holdings, Ltd. as in effect on the date
               hereof and as such agreement may be amended from time to time in
               a manner no less favorable to the Lenders, and (f) transactions
               pursuant to arrangements in effect on the Closing Date in an
               aggregate amount not to exceed $5,000,000.

               "Facility": each of (a) the Tranche A Term Loan Commitments and
               the Tranche A Term Loans made thereunder (the "Tranche A Term
               Loan Facility"), (b) the Delayed Draw Term Loan Commitments and
               the Delayed Draw Term Loans made thereunder (the "Delayed Draw
               Term Loan Facility"), (c) the Conversion Term Loans (the
               "Conversion Term Loan Facility"), (d) the Optional Non-Vendor
               Loan Commitments, if any, and the Optional Non-Vendor Loans made
               thereunder (the "Optional Non-Vendor Loan Facility"), (e) the
               Optional Vendor Commitments, if any, and the Optional Vendor
               Loans made thereunder (the

                                       3
<PAGE>   4

               "Optional Vendor Loan Facility") and (f) the Revolving Credit
               Commitments and the Revolving Credit Loans made thereunder
               (the "Revolving Credit Facility").

               "Majority Facility Lenders": at any time, with respect to any
               Facility, the holders of more than 50% of the aggregate unpaid
               principal amount of the Loans outstanding under such Facility
               plus the aggregate amount of undrawn Commitments then in effect
               under such Facility.

               "Optional Term Loan": any Optional Non-Vendor Loan and any
               Optional Vendor Loan.

               "Optional Term Loan Commitment": any Optional Non-Vendor Loan
               Commitment and any Optional Vendor Commitment.

               "Optional Term Loan Lender": any Optional Non-Vendor Loan Lender
               and any Optional Vendor Loan Lender.

               "Optional Term Loan Tranche": any Optional Non-Vendor Loan
               Tranche and any Optional Vendor Loan Tranche.

               "Required Lenders": at any time, the holders of more than 50% of
               the aggregate unpaid principal amount of the Loans then
               outstanding plus the aggregate amount of undrawn Commitments
               (other than Optional Vendor Commitments) then in effect.

               (b) Section 1.1 is hereby further amended by adding thereto the
following new definitions in proper alphabetical order:

               "Amendment Effective Date": the "Effective Date" as defined in
               the Amendment, dated as of March 30, 2001, to this Agreement.

               "Collateral and Securities Account":  as defined in Section 6.13.

               "Convertible Notes": notes issued by the Borrower to such Person
               or Persons as determined by the Borrower, substantially in the
               form and having the terms set forth in Exhibit A to the
               Amendment, dated as of March 30, 2001, to this Agreement; such
               terms shall in any event include subordination of such notes, in
               right of payment, to the Obligations, and subordination of any
               security interest securing such notes to the security interest of
               the Collateral Agent, in each case pursuant to subordination and
               intercreditor provisions reasonably acceptable to the
               Administrative Agent.

               "New Lender Supplement": the agreement made pursuant to Section
               2.7 substantially in the form of Exhibit J.

               "Non-Core Assets": at any time of determination (i) all
               international licenses held by the Borrower or any of its
               Subsidiaries in markets where full-scale commercial service has
               not been launched at such time and (ii) all international joint
               ventures and international Subsidiaries, which, in the case of
               clauses (i) and (ii) above, are not material to the business,
               property or condition (financial or otherwise) of the Borrower
               and its Subsidiaries taken as a whole.

                                       4
<PAGE>   5

               "Operating Accounts": as defined in Section 6.13.

               "Optional Non-Vendor Loan Commitment": as to any Lender, the
               obligation of such Lender, if any, to make an Optional Non-Vendor
               Loan to the Borrower hereunder in a principal amount not to
               exceed the amount set forth in the Optional Term Loan Amendment
               related thereto.

               "Optional Non-Vendor Loan":  as defined in Section 2.7.

               "Optional Non-Vendor Loan Lender": each Lender which has an
               Optional Non-Vendor Commitment or which is the holder of an
               Optional Non-Vendor Loan.

               "Optional Non-Vendor Loan Tranche":  as defined in Section 2.7.

               "Optional Vendor Commitment": as to any Optional Vendor Loan
               Lender, the obligation of such Optional Vendor Loan Lender, if
               any, to make an Optional Vendor Loan to the Borrower hereunder in
               a principal amount not to exceed the amount set forth in the
               Optional Term Loan Amendment related thereto.

               "Optional Vendor Loan":  as defined in Section 2.7.

               "Optional Vendor Loan Lender": each Lender which has an Optional
               Vendor Commitment or which is the holder of an Optional Vendor
               Loan.

               "Optional Vendor Loan Tranche":  as defined in Section 2.7.

               "Vendor": a vendor of plant, property, services or equipment
               and/or similar or related Property to the Borrower or its
               Subsidiaries, the sale or other provision of which is financed,
               in whole or in part, pursuant to Optional Vendor Loans.

               (c) Section 1.1 is hereby further amended by deleting the
definition of "Unused Proceeds Basket".

               3.    Amendment to Section 2.7. Section 2.7 is hereby amended so
that it shall read in its entirety as follows:

               (a) Optional Non-Vendor Loans. Subject to the terms and
               conditions hereof, the Borrower may, with the consent of the
               Required Lenders, at any time and from time to time prior to
               December 31, 2001, establish one or more additional non-vendor
               term loan tranches (each, an "Optional Non-Vendor Loan Tranche")
               pursuant to which non-vendor term loans ("Optional Non-Vendor
               Loans") may be made, provided, (i) each Optional Non-Vendor Loan
               Tranche shall be in a principal amount of at least $50,000,000
               and (ii) all Optional Non-Vendor Loan Tranches shall not exceed
               in the aggregate the difference of (A) $600,000,000 less (B) the
               aggregate amount of Optional Vendor Loan Tranches then in effect.
               The Borrower may offer to any existing Lender, or to one or more
               additional banks, financial institutions or other entities
               reasonably acceptable to the Administrative Agent, the
               opportunity to participate in all or a portion of an Optional
               Non-Vendor Loan Tranche.

               (b) Optional Vendor Loans. Subject to the terms and conditions
               hereof, the

                                       5
<PAGE>   6

               Borrower may at any time and from time to time prior to December
               31, 2001, establish one or more vendor loan tranches (each, an
               "Optional Vendor Loan Tranche") pursuant to which vendor loans
               ("Optional Vendor Loans") may be made by one or more Vendors,
               provided, (i) each Optional Vendor Loan Tranche shall be in a
               principal amount of at least $50,000,000 and (ii) all Optional
               Vendor Loan Tranches shall not exceed $350,000,000 in the
               aggregate or, if less, the difference of (A) $600,000,000 less
               (B) the aggregate amount of Optional Non-Vendor Loan Tranches
               then in effect. The Borrower may offer to any existing Optional
               Vendor Loan Lender, or to one or more additional Vendors
               reasonably acceptable to the Administrative Agent, the
               opportunity to participate in all or a portion of an Optional
               Vendor Loan Tranche. Proceeds of Optional Vendor Loans may be
               used only to finance Capital Expenditures and services related to
               Capital Expenditures.

               (c) Optional Term Loan Procedures. The Borrower shall request the
               establishment of an Optional Term Loan Tranche by delivery to the
               Administrative Agent of a written request therefor (an "Optional
               Term Loan Request") which shall be promptly distributed by the
               Administrative Agent to the applicable Lenders. Each Optional
               Term Loan Request shall (i) set forth the aggregate principal
               amount of the requested Optional Term Loan Tranche and the
               Applicable Margin (or, if applicable, the formula for the
               calculation thereof) and the commitment fee rate, if any,
               applicable to the Optional Term Loans to be made under such
               Optional Term Loan Tranche, the amortization and maturity date of
               such Optional Term Loans and the borrowing procedures relating to
               the borrowing by the Borrower of such Optional Term Loans and
               (ii) if applicable, be accompanied by such information as the
               Administrative Agent shall reasonably request for use in
               syndication of the requested Optional Term Loans. All Optional
               Term Loans shall (I) have a Weighted Average Life (calculated on
               the date the related Optional Term Loan Tranche shall become
               effective) that is at least as long as the then Weighted Average
               Life (calculated on such date) of the Revolving Credit
               Commitments and the Term Loans, taken as a whole, (II) have a
               final scheduled maturity date on or after December 31, 2006,
               (III) bear interest at rates no higher than those applicable to
               the Tranche A Term Loans, (IV) otherwise be subject to the same
               terms and conditions as the other Term Loans outstanding
               hereunder, (V) be subject to no other conditions other than, in
               the case of Optional Vendor Loans, the requirement that the
               proceeds be used to purchase equipment and/or services from or
               through the applicable Vendors and (VI) be in form and substance
               otherwise reasonably satisfactory to the Administrative Agent. No
               Lender shall have any obligation to participate in any Optional
               Term Loan Tranche unless it agrees to do so in its sole
               discretion. All Optional Term Loan Tranches shall not exceed
               $600,000,000 in the aggregate.

               (d) New Lenders. In the case of any Optional Non-Vendor Loan
               Tranche, any banks, financial institutions or other entities,
               and, in the case of any Optional Vendor Loan Tranche, any Vendor,
               which elects to become a party to this Agreement and obtain an
               Optional Term Loan Commitment pursuant to this Section 2.7 shall
               execute a New Lender Supplement (each, a "New Lender Supplement")
               with the Borrower and the Administrative Agent, substantially in
               the form of Exhibit J, whereupon such lender (herein called a
               "New Lender")

                                       6
<PAGE>   7

               shall become an Optional Term Loan Lender for all purposes and to
               the same extent as if originally a party hereto and shall be
               bound by and entitled to the benefits of this Agreement and the
               other Loan Documents, and Schedule 1.1 shall be deemed to be
               amended to add the name and Optional Non-Vendor Loan Commitment
               or Optional Vendor Commitment, as applicable, of such New Lender.

               (e) Conditions to Effectiveness. The effectiveness of any
               Optional Term Loan Tranche shall be contingent upon (i) execution
               and delivery by the Administrative Agent, the Borrower and each
               Lender providing Optional Term Loan Commitments under such
               Optional Term Loan Tranche of an Optional Term Loan Amendment
               relating to such Optional Term Loan Tranche, (ii) receipt by the
               Administrative Agent of such corporate resolutions and officer's
               certificates of the Borrower and legal opinions of counsel to the
               Borrower as the Administrative Agent shall reasonably request
               with respect thereto, and (iii), if applicable, execution and
               delivery by the Borrower, the Administrative Agent and each New
               Lender providing Optional Term Loan Commitments under such
               Optional Term Loan Tranche of the New Lender Supplement, in each
               case in form and substance reasonably satisfactory to the
               Administrative Agent. The Borrower and the Administrative Agent
               agree to negotiate in good faith any Optional Term Loan Amendment
               relating to any Optional Term Loan Tranche.

               4.    Amendment to Section 2.12. Section 2.12 is hereby amended
so that it shall read in its entirety as follows:

               Optional Prepayments. The Borrower may at any time and from time
               to time prepay the Term Loans and reduce the Revolving Credit
               Commitments, in whole or in part, without premium or penalty
               except as provided in the last sentence of this Section, upon
               irrevocable notice delivered to the Administrative Agent at least
               three Business Days prior thereto in the case of Eurodollar Loans
               and at least one Business Day prior thereto in the case of ABR
               Loans, which notice shall specify the date and amount of
               prepayment and whether the prepayment is of Eurodollar Loans or
               ABR Loans; provided, that if a Eurodollar Loan is prepaid on any
               day other than the last day of the Interest Period applicable
               thereto, the Borrower shall also pay any amounts owing pursuant
               to Section 2.22; provided, further, that any prepayment made
               pursuant to this Section 2.12 shall be applied pro rata to (i)
               the Tranche A Term Loans, (ii) the Conversion Term Loans, (iii)
               the Optional Term Loans, (iv) the reduction of the Delayed Draw
               Term Loans and (v) the reduction of the Revolving Credit
               Commitments. Upon receipt of any such notice the Administrative
               Agent shall promptly notify each relevant Lender thereof. If any
               such notice is given, the amount specified in such notice shall
               be due and payable on the date specified therein, together with
               accrued interest to such date on the amount prepaid. Any
               reduction of the Revolving Credit Commitments pursuant to this
               Section 2.12 shall be accompanied by prepayment of the Revolving
               Credit Loans to the extent, if any, that the aggregate
               outstanding principal amount of Revolving Credit Loans exceeds
               the amount of the Total Revolving Credit Commitments as so
               reduced. Partial prepayments of Term Loans and Revolving Credit
               Commitments shall be in an aggregate principal amount of
               $1,000,000 or a whole multiple thereof. Optional prepayments of
               the

                                       7
<PAGE>   8

               Term Loans occurring prior to the first anniversary of the
               Closing Date shall be accompanied by a prepayment fee equal to 3%
               of the amount of such prepayment.

               5.    Amendment to Section 2.13. (a) Section 2.13(b) is hereby
amended so that it shall read in its entirety as follows:

               (b) Unless the Required Prepayment Lenders shall otherwise agree,
               if on any date the Borrower or any of its Subsidiaries shall
               receive Net Cash Proceeds from any Asset Sale or Recovery Event
               by the Borrower or its Subsidiaries then, unless a Reinvestment
               Notice shall be delivered in respect thereof within five Business
               Days after receipt of such Net Cash Proceeds, such Net Cash
               Proceeds shall be applied on such date toward the prepayment of
               the Term Loans and the reduction of the Revolving Credit
               Commitments as set forth in Section 2.13(d); provided, that, on
               each Reinvestment Prepayment Date, an amount equal to the
               Reinvestment Prepayment Amount with respect to the relevant
               Reinvestment Event shall be applied toward the prepayment of the
               Term Loans and the reduction of the Revolving Credit Commitments
               as set forth in Section 2.13(d); and provided, further, that (i)
               the Borrower may not at any time deliver a Reinvestment Notice
               with respect to more than 35% of the Net Cash Proceeds of any
               Asset Sale and (ii) any Net Cash Proceeds of Asset Sales in
               respect of which Reinvestment Notices have been delivered shall
               be reinvested in tangible Property, including the installation
               thereof and services reasonably related to such installation,
               located in the United States of America useful in the business of
               the Borrower consistent with its past practice and with normal
               industry practice in accordance with this Section 2.13. If at any
               time the aggregate amount of Net Cash Proceeds of Asset Sales in
               respect of which Reinvestment Notices have been delivered shall
               exceed 35% of the aggregate amount of Net Cash Proceeds
               theretofore received from Asset Sales, then the Borrower promptly
               shall apply such excess over 35% in accordance with Section
               2.13(d). In addition, if at any time the aggregate amount of Net
               Cash Proceeds in respect of which Reinvestment Notices have been
               delivered and which have not been reinvested in accordance with
               such Reinvestment Notices or applied in accordance with Section
               2.13(d) shall exceed $5,000,000, then the Borrower promptly shall
               deliver such excess over $5,000,000 to the Collateral Agent to be
               held by it in accordance with the Collateral Agency and
               Intercreditor Agreement.

               (b) Section 2.13(d) is hereby amended so that it shall read in
its entirety as follows:

               (d) Amounts to be applied in connection with prepayments and
               Commitment reductions made pursuant to Section 2.13(a), (b) or
               (c) or Section 6.6 shall be applied to the prepayment of the Term
               Loans, the reduction of the Revolving Credit Commitments and the
               reduction of any Delayed Draw Term Loan Commitments then unused
               and in effect, pro rata according to the respective amounts of
               the outstanding Term Loans, outstanding Revolving Credit
               Commitments and unused Delayed Draw Term Loan Commitments then in
               effect. Any such reduction of the Revolving Credit Commitments
               shall be accompanied by prepayment of the Revolving Credit Loans
               to the extent, if any, that the aggregate outstanding principal
               amount of Revolving Credit Loans exceeds the

                                       8
<PAGE>   9

               amount of the Total Revolving Credit Commitments as so reduced.
               The application of any prepayment pursuant to this Section shall
               be made first to ABR Loans and second to Eurodollar Loans. Each
               prepayment of the Loans under this Section (except in the case of
               Revolving Credit Loans that are ABR Loans) shall be accompanied
               by accrued interest to the date of such prepayment on the amount
               prepaid. No prepayment fee shall be payable in connection with
               any prepayment or Commitment reduction required by paragraphs (a)
               through (c) above.

               (c) Section 2.13(e) is hereby amended so that it shall read in
its entirety as follows:

               (e) [Reserved.]

               6.    Amendment to Lead-In to Section 5. The lead-in to Section
5 is hereby amended so that it shall read in its entirety as follows:

               The Borrower hereby agrees that, so long as any Commitment
               remains in effect or any Loan or other amount is owing to any
               Lender or any Agent hereunder, the Borrower shall and, except in
               the case of delivery of financial statements and information,
               reports and notices and except in the case of agreements pursuant
               to Section 5.12 and 5.13 hereof, shall cause each of its
               Restricted Subsidiaries to:

               7.    Waiver to Section 5.1(a). The requirement of Section
5.1(a)  of the Credit Agreement that the independent certified public
accountants' report which accompanies the audited financial statements shall
not contain a "`going concern' or like qualification or exception" shall be
waived for the fiscal year ended December 31, 2000 insofar as such "going
concern" qualification results from the Borrower having incurred recurring
operating losses and having a substantial need for working capital.

               8.    Amendment to Section 5.2(d). Section 5.2(d) is hereby
amended so that it shall read in its entirety as follows:

               (d)   concurrently with the delivery of any financial statements
               pursuant to Section 5.1, a narrative discussion and analysis of
               the financial condition and results of operations of the Borrower
               and its Subsidiaries for such fiscal quarter and for the period
               from the beginning of the then current fiscal year to the end of
               such fiscal quarter, as compared to the portion of the
               Projections covering such periods and to the comparable periods
               of the previous year;

               9.    Amendment to Section 5.10. (a) Section 5.10(a) is hereby
amended so that it shall read in its entirety as follows:

               (a) Promptly (i) transfer to LicenseCo any FCC License held by
               the Borrower or any Restricted Subsidiary and take any other
               actions as shall be required to cause the Collateral Agent to
               have a perfected first priority security interest therein (to the
               extent permissible under applicable law), (ii) create on terms
               reasonably acceptable to the Administrative Agent a perfected
               first priority security interest in favor of the Collateral Agent
               in all Personal Property Assets now owned or hereafter acquired
               by the Borrower or any Restricted Subsidiary (including any
               Personal Property Assets owned or hereafter acquired by AssetCo)
               and any

                                       9
<PAGE>   10

               Personal Property Assets of any Person that becomes a Restricted
               Subsidiary or is merged with or into or consolidated with the
               Borrower or any Restricted Subsidiary (in each case other than
               any such Personal Property Assets constituting Excluded Assets)
               and (iii) without limiting the requirements of Section 5.10(c),
               at the option of the Borrower, either (x) transfer to LeasingCo
               any Real Property Assets hereafter acquired by the Borrower or
               any Restricted Subsidiary and any Real Property Assets of any
               Person that becomes a Restricted Subsidiary or is merged with or
               into or consolidated with the Borrower or any Restricted
               Subsidiary (in each case other than any such Real Property Assets
               constituting Excluded Assets) or (y) create on terms reasonably
               acceptable to the Administrative Agent a perfected first priority
               security interest in favor of the Collateral Agent in such Real
               Property Assets, other than Excluded Assets (which security
               interest may be subject to any Liens permitted by Section 6.3
               (other than those referred to in the definition of the term
               "Excluded Assets)) .

               (b) Section 5.10(c) is hereby amended so that it shall read in
its entirety as follows:

               (c) Promptly create a mortgage on terms reasonably acceptable to
               the Administrative Agent in favor of the Collateral Agent on any
               fee simple title in real property owned by the Borrower or any
               Restricted Subsidiary having at the time of acquisition thereof a
               purchase price or fair market value greater than $1,000,000
               (other than Excluded Assets), including any such properties that
               are acquired by the Borrower or any Restricted Subsidiary after
               the date hereof and any such properties of any Person that
               becomes a Restricted Subsidiary or is merged with or into or
               consolidated with the Borrower or any Restricted Subsidiary.

               (b) Section 5.10(d) is hereby amended so that it shall read in
its entirety as follows:

               (d) Promptly cause (i) all Capital Stock of any Subsidiary
               (including, without limitation, any Subsidiary which shall be
               acquired by the Borrower or any Restricted Subsidiary) held by
               the Borrower or its Restricted Subsidiaries to be pledged to the
               Collateral Agent as Collateral; provided, that only 65% of the
               Capital Stock of any Excluded Foreign Subsidiary which is a
               Subsidiary of the Borrower or any Domestic Subsidiary, and none
               of the Capital Stock of any Subsidiary of an Excluded Foreign
               Subsidiary, shall be required to be pledged and (ii) each
               Restricted Subsidiary to become a party to the Guarantee and
               Collateral Agreement.

               10.    Amendment to Section 5. Section 5 is hereby amended to
add, after Section 5.11, the following new Sections 5.12 and 5.13 as follows:

               5.12 Convertible Notes. Deliver to the Administrative Agent, on
               or before April 30, 2001, definitive documentation, duly
               authorized, executed and delivered by the Borrower and such
               Person or Persons as determined by the Borrower with respect to
               the Convertible Notes, on terms and conditions reasonably
               satisfactory to the Administrative Agent and in an aggregate
               principal amount equal to or in excess of $100,000,000.

                                       10
<PAGE>   11

               5.13 Vendor Financing. Deliver to the Administrative Agent, on or
               before April 30, 2001, definitive documentation, duly authorized,
               executed and delivered by the Borrower and one or more Vendors,
               including a New Lender Supplement duly executed and delivered by
               the Borrower and each relevant Vendor, with respect to the
               establishment of one or more Optional Vendor Loan Tranches
               pursuant to Section 2.7 of, and in all material respects in
               accordance with, this Agreement in an aggregate principal amount
               equal to or in excess of $250,000,000.

               11.    Amendment to Section 6.1. (a) Section 6.1(a) is hereby
amended so that it shall read in its entirety as follows:

               (a) Consolidated Total Debt to Consolidated Adjusted
               Capitalization. Permit the ratio of Consolidated Total Debt to
               Consolidated Adjusted Capitalization during any test period set
               forth below to be greater than the ratio set forth below opposite
               such test period:

               Test Period                                Ratio
               -----------                                -----

               Closing Date - 12/31/98                    60%
               1/1/99 - thereafter                        65%

               (b) Section 6.1(b) is hereby amended so that it shall read in its
entirety as follows:

               (b) Consolidated Secured Debt to Consolidated Adjusted
               Capitalization. Permit the ratio of Consolidated Secured Debt to
               Consolidated Adjusted Capitalization during any test period set
               forth below to be greater than the ratio set forth below opposite
               such test period:

               Test Period                                Ratio
               -----------                                -----

               Closing Date - 12/31/98                    30%
               1/1/99 -  thereafter                       40%

               (c) Section 6.1(c) is hereby amended so that it shall read in its
entirety as follows:

               (c) Minimum Consolidated Total Revenue. Permit Consolidated Total
               Revenue for any fiscal quarter set forth below to be less than
               the amount set forth opposite such fiscal quarter below:

               Fiscal Quarter Ending                          Amount
               ---------------------                          ------

                3/31/01                                   [REDACTED]*
                6/30/01                                   [REDACTED]*

               (d) Section 6.1(f) is hereby amended to delete the last sentence
thereof, which read, "In addition to the amounts set forth above, Capital
Expenditures may be funded from the Unused Proceeds Basket".

               (e) Section 6.1(j) is hereby amended so that it shall read in its
entirety as follows:

                                       11
<PAGE>   12

               (j) Consolidated Fixed Charge Coverage Ratio. (a)(i) From the
               fiscal quarter ending June 30, 2001 through the fiscal quarter
               ending September 30, 2003, permit the Consolidated Fixed Charge
               Coverage Ratio on the last day of any fiscal quarter ending on
               any date set forth below to be less than the ratio set forth
               opposite such date below:

                      Fiscal Quarter Ending               Ratio
                      ---------------------               -----

                      6/30/01                             2.00

                      9/30/01                             1.75

                      12/31/01                            2.50

                      3/31/02 through 9/30/03             1.25; and

               (ii) From the fiscal quarter ending December 31, 2003 and
               thereafter, permit the Consolidated Fixed Charge Coverage Ratio
               for any period of four consecutive fiscal quarters ending during
               any test period set forth below to be less than the ratio set
               forth opposite such test period below:

                      12/31/03 through 9/30/04            1.10

                      12/31/04 and thereafter             1.25; or

               (b) From the fiscal quarter ending June 30, 2001 through the
               fiscal quarter ending September 30, 2003, fail to deliver to the
               Administrative Agent and the Lenders, on or before the date which
               is ten Business Days after the end of any fiscal quarter, a
               certificate of a Responsible Officer showing calculations
               demonstrating compliance with the foregoing clause (i) on the
               last day of such fiscal quarter.

               (f) Section 6.1 is hereby amended to add the following new
Section 6.1(k) below:

               (k) Minimum Consolidated EBITDA. Permit Consolidated EBITDA for
               the period ending on the last day of the fiscal quarter set forth
               below to be less than the amount set forth opposite such fiscal
               quarter below:

               Fiscal Quarter Ending                        Amount
               ---------------------                        ------

                     3/31/01                              [REDACTED]*
                     6/30/01                              [REDACTED]*
                     9/30/01                              [REDACTED]*
                     12/31/01                             [REDACTED]*
                     3/31/02                              [REDACTED]*
                     6/30/02                              [REDACTED]*
                     9/30/02                              [REDACTED]*
                     12/31/02                             [REDACTED]*
                     3/31/03                              [REDACTED]*
                     6/30/03                              [REDACTED]*
                     9/30/03                              [REDACTED]*
                     12/31/03                             [REDACTED]*

                                       12
<PAGE>   13

                    3/31/04                               [REDACTED]*
                    6/30/04                               [REDACTED]*
                    9/30/04                               [REDACTED]*
                    12/31/04                              [REDACTED]*

               (g) Section 6.1 is hereby amended to add the following new
Section 6.1(l) below:

               (l) Minimum Liquidity. Permit the aggregate amount of cash and
               Cash Equivalents held in (i) the Operating Accounts of the
               Borrower and (ii) the Collateral and Securities Account of the
               Borrower held at The Chase Manhattan Bank, in each case pursuant
               to Section 6.13 of this Agreement, to be less than $150,000,000
               on March 31, 2001.

               12.    Waiver of Section 6.1(j). The parties hereto hereby agree
that the requirement of Section 6.1(j) that the Consolidated Fixed Charge
Coverage Ratio on the last day of the fiscal quarter ending December 31, 2000 be
equal to or more than 1.10 shall be waived.

               13.    Amendment to Section 6.2. (a) Section 6.2(c) is hereby
amended so that it shall read in its entirety as follows:

               (c) Indebtedness (including, without limitation, Capital Lease
               Obligations) secured by Liens permitted by Section 6.3(g);
               provided, that (i) not more than $25,000,000 of such Indebtedness
               may be incurred to finance the acquisition of Network Assets
               (other than fiber or fiber capacity) and (ii) that not more than
               $[REDACTED]* of such Indebtedness may be incurred to finance the
               acquisition of fiber or fiber capacity;

               (b) Section 6.2 is hereby further amended by (i) deleting the
word "and" at the end of clause (j), (ii) deleting the period at the end of
clause (k) and inserting a semi-colon and the word "and" in lieu thereof and
(iii) adding the following new clause (l):

               (l) Indebtedness incurred under the Convertible Notes in an
               aggregate principal amount not to exceed [REDACTED]*.

               14.    Consent to Section 6.2(g). The parties hereto hereby
agree that the requirement of Section 6.2(g)(x) that unsecured Indebtedness or
preferred stock of the Borrower issued or incurred after July 2, 1998 generating
the first $500,000,000 in Net Cash Proceeds shall provide for interest or
dividends thereon to be paid in kind (or to be paid out of amounts deposited in
escrow or pledged as collateral from the proceeds thereof) for at least three
years after the date of incurrence or issuance thereof shall be deemed
satisfied.

               15.    Amendment to Section 6.3. (a) Section 6.3(g) is hereby
amended to read in its entirety as follows:

               (g) Liens securing Indebtedness of the Borrower or any Restricted
               Subsidiary incurred pursuant to Section 6.2(c) to finance the
               acquisition or capital lease of fixed or capital assets, provided
               that (i) such Liens shall be created within 90 days from the
               acquisition of such fixed or capital assets and (ii) such Liens
               do not at any time encumber any Property other than the Property
               financed by such Indebtedness;

                                       13
<PAGE>   14
               (b) Section 6.3 is hereby further amended by (i) deleting the
word "and" at the end of clause (k), (ii) deleting the period at the end of
clause (l) and inserting a semi-colon in lieu thereof and (iii) adding the
following new clauses (m), (n) and (o):

               (m) Uniform Commercial Code filings with respect to operating
               leases or consignment arrangements entered into in the ordinary
               course of business of the Borrower or any of its Restricted
               Subsidiaries, to the extent filed to reflect the interests of the
               lessor or relevant party in respect of such leases or consignment
               arrangements, as the case may be;

               (n) Liens in favor of banking institutions arising by operation
               of law encumbering deposits held by such banking institution
               incurred by the Borrower or its Restricted Subsidiaries in the
               ordinary course of business; and

               (o) second priority Liens on the Collateral securing the
               obligations under the Convertible Notes permitted pursuant to
               Section 6.2(l), provided, that (i) such Liens shall be subject to
               customary second lien and Indebtedness subordination provisions
               satisfactory to the Administrative Agent providing, among other
               things, that such Liens shall be subject to the priority of Liens
               securing the Obligations (including with respect to the exercise
               of remedies and decisions relating to the Collateral) and that
               the obligations under the Convertible Notes shall be subordinated
               to the Obligations and (ii) the documentation with respect to
               such Liens shall include an intercreditor agreement and such
               other documentation reasonably requested by the Administrative
               Agent, satisfactory in form and substance to the Administrative
               Agent.

               16.    Amendment to Section 6.5. (a) Sections 6.5(c) is hereby
amended so as to read in its entirety as follows:

               (c) so long as after giving effect thereto the Borrower is in Pro
               Forma Compliance, any Asset Sale for fair market value; provided,
               that (i) the aggregate consideration in connection with all Asset
               Sales shall not exceed [REDACTED]* and (ii) the Net Cash Proceeds
               of all Asset Sales shall be applied in accordance with Section
               2.13;

               (b) The proviso at the end of Sections 6.5 is hereby amended so
as to read in its entirety as follows:

               provided that in each case described in clauses (c) and (e)
               above, at least 75% of the consideration received by the
               Borrower or its Restricted Subsidiaries for such Disposition
               shall consist of cash and Cash Equivalents.

               17.    Amendment to Section 6.7. (a) Sections 6.7(d), (e) and (f)
are hereby amended so as to read in their entirety as follows:

               (d) Investments by the Borrower and its Restricted Subsidiaries
               (other than the Special Purpose Subsidiaries) in Unrestricted
               Subsidiaries and joint ventures, provided, that (x) the
               consideration for such Investments made after the Effective Date
               in excess of [REDACTED]* in the aggregate shall be the common
               stock of the Borrower, (y) the consideration for such Investments
               made after the Effective

                                       14
<PAGE>   15

               Date may not include, directly or indirectly, the Disposition of
               any Network Assets of the Borrower or any Restricted Subsidiary
               (including, without limitation, licenses, whether domestic or
               foreign, but excluding, the entering into of one or more
               management agreements with respect to spectrum by any Restricted
               Subsidiary to any Unrestricted Subsidiary or other Person;
               provided, that such agreements are (A) compliant with all
               material terms of this Agreement as determined by the
               Administrative Agent in good faith (including, without
               limitation, that all Net Cash Proceeds of such management
               agreement shall be applied in accordance with Section 2.13) and
               (B) reasonably satisfactory in form and substance to FCC counsel
               to the Lenders), and (z) after giving effect to such Investment
               the Borrower shall be in Pro Forma Compliance;

               (e) Investments in wireless telecommunications licenses issued by
               a governmental authority, including FCC Licenses, and in Persons
               engaged in the telecommunications business and substantially all
               of whose assets consist of wireless telecommunications licenses
               which become Restricted Subsidiaries as a result of such
               Investment, provided, that (w) the consideration for such
               Investments shall be the common stock of the Borrower, (x) with
               respect to Investments in Persons pursuant to this clause (e),
               such Investments shall be made only in Persons which have
               provided to the Administrative Agent financial statements
               certified by the chief financial officer of such Person
               reflecting a positive EBITDA for such Person for the immediately
               preceding consecutive twelve-month period, (y) after giving
               effect to such Investment the Borrower shall be in Pro Forma
               Compliance and (z) the consideration for Investments made in
               telecommunications licenses issued by any Governmental Authority
               outside the United States shall be the common stock of the
               Borrower;

               (f) Investments in additional Telecommunications Assets,
               excluding wireless telecommunications licenses, and in Persons
               engaged in the telecommunications business which become
               Restricted Subsidiaries as a result of such Investment, provided,
               that (x) the consideration for such Investments shall be the
               common stock of the Borrower, (y) with respect to Investments in
               Persons pursuant to this clause (f), such Investments shall be
               made only in Persons which have provided to the Administrative
               Agent financial statements certified by the chief financial
               officer of such Person reflecting a positive EBITDA for such
               Person for the immediately preceding consecutive twelve-month
               period, and (z) after giving effect to each such Investment the
               Borrower shall be in Pro Forma Compliance;

               18.    Amendment to Section 6.12(b). Sections 6.12(b) is hereby
amended so as to read in its entirety as follows:

               (b) Permit LicenseCo to incur any material liabilities (other
               than pursuant to the Loan Documents) or to engage in any business
               or activities other than (i) the holding of Licenses, (ii) the
               entering into of one or more management agreements with respect
               to spectrum with any Unrestricted Subsidiary or other Person
               (provided, that such agreements are (A) compliant with all
               material terms of this Agreement as determined by the
               Administrative Agent in good faith (including, without
               limitation, that all Net Cash Proceeds of such management
               agreement shall be applied in accordance with Section 2.13) and
               (B) reasonably satisfactory

                                       15
<PAGE>   16

               in form and substance to FCC counsel to the Lenders) and (iii) in
               each case, to engage in activities directly incident or directly
               related thereto.

               19.   Addition of Section 6.13. The following shall be added as
Section 6.13:

               6.13. Maintenance of Cash and Cash Equivalents. From and after
               the Amendment Effective Date, hold, directly or indirectly, any
               cash or Cash Equivalents, except as follows:

                     (a) the Borrower and its Restricted Subsidiaries may hold
               cash in operating accounts maintained with any bank or other
               financial institution reasonably satisfactory to the
               Administrative Agent (the "Operating Accounts") so long as, at
               the close of business on any day (after giving effect to any
               transfers at such close of business to the Collateral and
               Securities Account), the amount on deposit in all Operating
               Accounts shall not exceed, in the aggregate, [REDACTED]*; and

                     (b) the Borrower and its Restricted Subsidiaries shall
               maintain all cash and Cash Equivalents, other than cash on
               deposit in an Operating Account to the extent permitted by the
               foregoing paragraph (a), in an account or accounts (collectively,
               the "Collateral and Securities Account") at The Chase Manhattan
               Bank, which shall be established and maintained upon the
               following terms:

                             (i) the Collateral and Securities Account shall be
                     established pursuant to agreements in form and substance
                     reasonably satisfactory to the Administrative Agent, which
                     shall in any event provide that (1) the Collateral and
                     Securities Account, and all cash and Cash Equivalents from
                     time to time credited thereto, and all earnings thereon,
                     shall constitute Collateral in which the Collateral Agent
                     has a security interest to secure the Secured Obligations
                     (as defined in the Collateral Agency and Intercreditor
                     Agreement) and (2) the Collateral Agent shall have sole
                     dominion and control of the Collateral and Securities
                     Account, and neither the Borrower nor any Restricted
                     Subsidiary shall have any right of withdrawal therefrom,
                     except as provided in clause (ii) below;

                             (ii) upon receipt by the Collateral Agent of a
                     request from the Borrower (1) stating that the aggregate
                     amount on deposit in all Operating Accounts as of the
                     close of business on the immediately preceding Business
                     Day was not more than [REDACTED]* and (2) requesting that
                     the Collateral Agent transfer from the Collateral and
                     Securities Account to an Operating Account funds in an
                     amount which, after giving effect to such transfer, will
                     not cause the provisions of this Section 6.13 to be
                     violated, the Collateral Agent will transfer such
                     requested amount in accordance with such request.

               20.   Amendment to Section 7(c). Section 7(c) is hereby amended
to read in its entirety as follows:

               (c) The Borrower shall default in the observance or performance
               of any agreement contained in Section 5.12 or Section 5.13 or any
               Loan Party shall

                                       16
<PAGE>   17

               default in the observance or performance of any agreement
               contained in Section 6;

               21.    Amendment to Section 9.5. Section 9.5 of the Credit
Agreement is hereby amended by deleting clause (a) in its entirety and
substituting the following in lieu thereof:

               (a) to pay or reimburse the Agents, and the formal and informal
               members of any steering committee of Lenders, for all their
               reasonable out-of-pocket costs and expenses incurred in
               connection with the development, preparation and execution of,
               and any amendment, supplement or modification to, this Agreement
               and the other Loan Documents and any other documents prepared in
               connection herewith or therewith, and the consummation and
               administration of the transactions contemplated hereby and
               thereby, including, without limitation, the reasonable fees and
               disbursements of one counsel for all of the Agents and any other
               consultants or professional advisors (including, without
               limitation, financial advisors) retained by the Administrative
               Agent,

               22.    Amendment to Annex A. Annex A to the Credit Agreement is
hereby deleted in its entirety.

               23.    Amendment to Exhibits. Exhibit J attached hereto as Annex
A shall hereby be added as Exhibit J to the Credit Agreement.

               24.    Amendment to Section 3.2 of the Guarantee and Collateral
Agreement. Section 3.2 is hereby amended to read in its entirety as follows:

               3.2 Limitation on Obligation to Perfect. Notwithstanding the
               foregoing, it is understood and agreed that no Grantor will be
               required to take any action to perfect any security interest
               created hereby other than (A) the filing of financing statements
               under the Uniform Commercial Code in the states (and, where
               applicable, counties, towns and parishes) necessary or, in the
               reasonable judgment of the Administrative Agent, desirable to
               create a perfected first priority security interest in the
               Personal Property Assets of such Grantor, (B) the filings
               required in the United States Patent and Trademark Office to
               perfect the security interest created hereby in any material
               United States Patents or U.S. Trademarks owned or held by such
               Grantor, (C) the filings and registrations required in the United
               States Copyright Office to perfect the security interest created
               hereby in any material United States Copyrights owned or held by
               such Grantor, (D) delivery to the Collateral Agent of any
               Possessory Collateral owned by such Grantor and (E) any actions
               required to perfect the security interest created hereby in any
               Non-Excluded Personal Property which, in the case of any Real
               Property Assets, has not been transferred to a LeasingCo;
               provided, that if after the date hereof there is any change in
               law which requires actions in addition to those described above
               to cause the security interests created hereby to be perfected to
               the same extent as the perfection effected by the foregoing
               actions under laws in effect on the date hereof, the Grantors
               will take such additional actions.

               25.    Amendment to Section 5.3(a) of the Guarantee and
Collateral Agreement. Section 5.3(a) is hereby amended by deleting the reference
to "Section 4.5" and substituting in lieu thereof a reference to "Section 4.3".

                                       17
<PAGE>   18

               26.    Amendment to Section 5.6(b)(ii) of the Guarantee and
Collateral Agreement. Section 5.6(b)(ii) is hereby amended by inserting the
following phrase immediately after the word "instruments" and immediately before
the symbol ")":

               , and any such Pledged Securities so sold, assigned, transferred,
               exchanged or otherwise disposed of as permitted by the Secured
               Instruments shall cease to be Pledged Securities hereunder

               27.    Conditions Precedent. Subject to the satisfaction of the
following conditions, this Amendment will become effective as of March 30, 2001
(the "Effective Date"):

              (a) Amendment. The Administrative Agent shall have received
        counterparts of this Amendment, duly executed by the Borrower, the
        Administrative Agent and the Required Lenders.

              (b) No Default or Event of Default. On and as of the Effective
        Date after giving effect to this Amendment, no Default or Event of
        Default shall have occurred and be continuing.

              (c) Representations and Warranties. The representations and
        warranties made by the Borrower in the Credit Agreement and the other
        Loan Documents after giving effect to this Amendment and the
        transactions contemplated hereby shall be true and correct in all
        material respects on and as of the Effective Date as if made on such
        date, except that where such representations and warranties relate to an
        earlier date, such representations and warranties shall have been true
        and correct in all material respects as of such earlier date, provided
        that all references to the Credit Agreement in such representations and
        warranties shall be and are deemed to mean this Amendment as well as the
        Credit Agreement as amended hereby.

              (d) Certificate. The Administrative Agent shall have received a
        Certificate of a Responsible Officer of the Borrower certifying the
        matters referred to in paragraphs (b) and (c).

              (e) Secretary's Certificate. The Administrative Agent shall have
        received a certificate from the Secretary or Assistant Secretary of the
        Borrower dated as of the Effective Date, (i) certifying attached copies
        of resolutions of the Board of Directors of the Borrower, authorizing
        the execution, delivery and performance of this Amendment, including the
        increase in the amount of the Optional Term Loan Commitments,
        contemplated hereby, (ii) certifying that the By-Laws and the
        Certificate of Incorporation of the Borrower have not been amended,
        restated, supplemented or otherwise modified since July 2, 1998, except
        for the amendments, restatements, supplements or modifications attached
        as an exhibit to such certificate, and (iii) evidencing the incumbency
        and signatures of the officers signing this Amendment.

              (f) Opinions. The Administrative Agent shall have received in
        connection with this Amendment (i) an opinion of in-house counsel to the
        Borrower, covering such matters that the Administrative Agent shall
        reasonably request and customary for transactions of this type, and (ii)
        an enforceability opinion of Cravath, Swaine & Moore, special New York
        counsel to the Borrower, which opinion shall also cover the creation and
        perfection of the security interest of the Collateral Agent in the
        Collateral and

                                       18
<PAGE>   19

        Securities Account and the enforceability of the agreements entered
        into in connection therewith.

              (g) Approvals. The Administrative Agent shall have received
        copies of all necessary corporate and governmental approvals (if any) of
        the Borrower for the increase of the aggregate amount of the Optional
        Term Loan Tranches, the addition of the Optional Vendor Loan Tranches
        therein, and any other transactions contemplated hereby.

              (h) Fees and Expenses. The Administrative Agent shall have
        received all fees required to be paid, including, without limitation, an
        amendment fee for the account of each Lender which executes and delivers
        this Amendment on or before the date hereof of 25 basis points on such
        Lender's Commitment, and all expenses for which invoices have been
        presented, including, without limitation, all expenses required to be
        paid pursuant to Section 9.5 (after giving effect to this Amendment), on
        or before the date hereof.

              (i) Subsidiary and Collateral Schedule. The Administrative Agent
        shall have received in connection with this Amendment a schedule or
        schedules listing (i) each direct and indirect Subsidiary of the
        Borrower, (ii) the Borrower's and each such Subsidiary's jurisdiction of
        incorporation, (iii) the location of the chief executive office of the
        Borrower and each Domestic Subsidiary, (iv) the locations of any
        tangible personal property of the Borrower and each Domestic Subsidiary,
        (v) the identity of the owner of the Capital Stock of each direct and
        indirect Subsidiary of the Borrower (and specifying whether such Capital
        Stock is certificated or uncertificated and, with respect to each
        Domestic Subsidiary and each Excluded Foreign Subsidiary which is a
        Subsidiary of the Borrower or any Domestic Subsidiary, if certificated,
        the share certificate number and the number of shares issued and
        outstanding) and (vi) each filing office in which UCC financing
        statements should be filed to perfect the security interest of the
        Collateral Agent in all personal property of the Borrower and each
        Restricted Subsidiary. Such schedules shall be accompanied by a
        certificate of the Borrower certifying such schedules to be true and
        correct.

               28.    Continuing Effect; No Other Amendments. Except as
expressly amended or waived hereby, all of the terms and provisions of the
Credit Agreement and the other Loan Documents are and shall remain in full force
and effect. The amendments and consent contained herein shall not constitute an
amendment or consent of any other provision of the Credit Agreement or the other
Loan Documents or for any purpose except as expressly set forth herein.

               29.    Binding Effect. This Amendment shall apply equally to
each of the Lenders parties to the Credit Agreement, and shall be binding upon
the Borrower, the Lenders, the Administrative Agent, the Arrangers, the
Documentation Agent, the Syndication Agent and all future holders of the Notes.

               30.    Governing Law. THIS AMENDMENT AND THE RIGHTS AND
OBLIGATIONS OF THE PARTIES HEREUNDER SHALL BE CONSTRUED IN ACCORDANCE WITH AND
BE GOVERNED BY THE LAW OF THE STATE OF NEW YORK.

               31.    Counterparts. This Amendment may be executed in any
number of counterparts and by the different parties hereto in separate
counterparts, each of which when so executed and delivered shall be deemed to be
an original and all of which taken together shall

                                       19
<PAGE>   20

constitute one and the same instrument. Delivery of an executed counterpart of a
signature page of this Amendment by facsimile transmission shall be as effective
as delivery of a manually executed counterpart of this Amendment.

               32.    Headings. Section headings in this Amendment are included
herein for convenience of reference only and shall not constitute a part of this
Amendment for any other purpose.

  [Remainder of this page left blank intentionally; Signature page to follow.]

                                       20
<PAGE>   21

               IN WITNESS WHEREOF, the parties hereto have caused this Agreement
to be executed by their duly authorized representatives as of the date first
above written.

                                      TELIGENT, INC.

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

                                      THE CHASE MANHATTAN BANK,
                                      As Administrative Agent

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

                                      [INSERT NAME OF LENDER],
                                      As a Lender

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

<PAGE>   22

                                                                        ANNEX A

                                                                      EXHIBIT J

                          FORM OF NEW LENDER SUPPLEMENT

               SUPPLEMENT, dated _________________, to the Credit Agreement
dated as of July 2, 1998 (as amended, restated, supplemented or otherwise
modified from time to time, the "Credit Agreement"), among Teligent, Inc., a
Delaware corporation (the "Borrower"), the Lenders from time to time parties
thereto, Goldman Sachs Credit Partners L.P., as Syndication Agent, Toronto
Dominion (Texas), Inc., as Documentation Agent, and The Chase Manhattan Bank, as
Administrative Agent. Capitalized terms used herein without definition shall
have the meaning ascribed to such terms in the Credit Agreement.

                              W I T N E S S E T H :

                WHEREAS, the Credit Agreement provides in Section 2.7 thereof
that, in the case of any Optional Non-Vendor Loan Tranche, any banks, financial
institutions or other entities, and, in the case of any Optional Vendor Loan
Tranche, any Vendor, to the Borrower may become a party to the Credit Agreement
as an Optional Term Loan Lender with the consent of the Borrower and the
Administrative Agent (which consent, in the case of the Administrative Agent,
shall not be unreasonably withheld) by executing and delivering to the Borrower
and the Administrative Agent a supplement to the Credit Agreement in
substantially the form of this Supplement; and

               WHEREAS, the undersigned now desires to become a party to the
Credit Agreement;

               NOW, THEREFORE, the undersigned hereby agrees as follows:

               1. The undersigned agrees to be bound by the provisions of the
        Credit Agreement, and agrees that it shall, on the date this Supplement
        is accepted by the Borrower and the Administrative Agent, become an
        Optional [Non-]Vendor Loan Lender for all purposes of the Credit
        Agreement to the same extent as if originally a party thereto, with an
        Optional [Non-]Vendor Loan Commitment of [$____________].

               2. The undersigned (a) represents and warrants that it is legally
        authorized to enter into this Supplement; (b) confirms that it has
        received a copy of the Credit Agreement, together with copies of the
        financial statements referred to in Section 5.1 thereof and such other
        documents and information as it has deemed appropriate to make its own
        credit analysis and decision to enter into this Supplement; (c) agrees
        that it has made and will, independently and without reliance upon any
        Agents or any other Lender and based on such documents and information
        as it shall deem appropriate at the time, continue to make its own
        credit decisions in taking or not taking action under the Credit
        Agreement or any

<PAGE>   23

        instrument or document furnished pursuant hereto or thereto; (d)
        appoints and authorizes the Administrative Agent to take such action as
        agent on its behalf and to exercise such powers and discretion under
        the Credit Agreement or any instrument or document furnished pursuant
        hereto or thereto as are delegated to the Administrative Agent by the
        terms thereof, together with such powers as are incidental thereto;
        and (e) agrees that it will be bound by the provisions of the Credit
        Agreement and will perform in accordance with its terms all the
        obligations which by the terms of the Credit Agreement are required to
        be performed by it as a Lender including, without limitation, if it is
        organized under the laws of a jurisdiction outside the United States,
        its obligation pursuant to Section 2.21 of the Credit Agreement.

               3. The undersigned's address for notices for the purposes of the
        Credit Agreement is as follows:

   [Remainder of the page left blank intentionally; Signature page to follow.]

<PAGE>   24

               IN WITNESS WHEREOF, the undersigned has caused this Supplement to
be executed and delivered by a duly authorized officer on the date first above
written.

                                    [INSERT NAME OF LENDER]

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

Accepted this _____ day of

--------------, ----.

TELIGENT, INC.

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

Accepted this ____ day of

--------------, ----.

THE CHASE MANHATTAN BANK, as Administrative Agent

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

<PAGE>   25

                                                              Exhibit A to the
                                                        Amendment and Consent,
                                                    dated as of March 30, 2001

                              CONVERTIBLE NOTES
                                 TERM SHEET

ISSUER:            Teligent, Inc. (the "Company").

INVESTORS:         Such Persons as determined by the Company.

ISSUE:             Convertible Notes, in one or more series (all series taken
                   together the "Notes").

AMOUNT:            Not to be less than $100 million nor to exceed $150 million.

TERM:              [REDACTED]* from date of first draw down of the respective
                   Series.

INTEREST RATE:
(APPLICABLE TO ALL SERIES)

                   1.     From initial draw down to shareholder approval of the
                          Exchange Rights and Warrants: Libor plus [REDACTED]*
                          basis point, [REDACTED], on drawn Notes.

                   2.     Upon shareholder approval of the Exchange Rights and
                          the Warrants the rate is reset at [REDACTED]*.

                   3.     If the Exchange Rights and the Warrants are not
                          approved at the shareholder's meeting, then the
                          Notes become due and payable [REDACTED]* after such
                          shareholders meeting. The Company will hold the
                          shareholders meeting as soon as practicable, but in
                          no case later than [REDACTED]*.

AVAILABILITY:      Each series shall be available for draw down to the Company
                   in tranches at any time after closing.  All draws must be
                   made within [REDACTED]* after the execution of the definitive
                   agreements for the Notes.

CONDITIONS
PRECEDENT:         The availability of one series, which shall be in an amount
                   equal to or in excess of [REDACTED]* ("Series A"), is
                   contingent only on [REDACTED]*.

                   One series, which shall be in an amount equal to or in
                   excess of [REDACTED]* ("Series B"), shall close after the
                   end of [REDACTED]*, subject only to the [REDACTED]*.

<PAGE>   26

RANKING:           The Notes shall be subordinate, in right of payment, to
                   the Obligations, and any security interest securing the
                   Notes shall be subordinate to the security interest of the
                   Collateral Agent, in each case pursuant to subordination
                   and intercreditor provisions reasonably acceptable to the
                   Administrative Agent.

PURPOSE:           The Company may draw down on the Notes from time to time
                   only to finance the acquisition and development of
                   telecommunications assets.

EXCHANGE RIGHTS:   Subject to shareholders approval, the Note holders may
                   exchange the Notes for the Company's common stock
                   [REDACTED]*.

OPERATING
MILESTONES:        There shall be no financial covenant requirements (i)
                   other than those set forth in Section 6.1 clauses (c) and
                   (k) of the Credit Agreement (as amended by the Amendment)
                   and (ii) for any period except Q1 and Q2 2001.

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