Document:

STATE OF SOUTH CAROLINA
                       )
CITY OF CHARLESTON     )

MUTUAL RELEASE

     THIS MUTUAL  RELEASE is entered  into and  delivered as of this 24th day of
December,  1996, by and among ENWIROMETRtCS,  INC., a corporation  organized and
existing  under the laws of the State of Delaware (the  "Company"'),  THE UNITED
STATES  COMPANY,  a  corporation  organized  and existing  under the laws of the
Commonwealth of Vixginia ("USC"), RICHARD H. GUILFORD, an individual resident of
the Commonwealth of Virginia  ("Gui[ford"),  MAUt~ITIO F. GIABBAI, an individual
resident of the State of Georgia  CGiabbai'),  and ELSIE L. ROSE, and individual
resident of the Commonwealth of Virginia  ("Rose") (USC,  Guilford,  Giabbai and
Rose being  collectively  referred to hereinafter as the "USC Group", and anyone
of them individually as a "USC Member").

                                   WITNESSETH:

     WHEREAS, the parties hereto have entered into an Agreement, dated as of the
date hereof (the '"Agreement"),  whereby certain claims of the USC Group against
the Company,  its subsidiaries  and affiliates,  and certain other claims of the
Company  against the USC Group  and/or  certain USC  Members,  have been finally
settled; and

     WHEREAS,  thc Company and the USC Group, in  consideration  of the benefits
and payments under the Agreement,  lmve agreed to completely  release each other
from claims, actions, causes of action and damages accruing prior to the date of
the Agreement, all as more particularly provided hereinbelow.

     NOW,  THEREFORE,  for valuable  consideration whose receipt and sufficiency
are hereby acknowledged, the parties agree as follows:

     1. Release by the Company.  The Company hereby and forever releases,  holds
harmless  and  discharges  the USC Group and each USC Member  (individually  and
collectively),  together  with each of their  personal  representatives,  heirs,
successors  and  assigns (as  applicable),  from and against any and all claims,
demands,  counterclaims,  actions,  costs,  causes of  action,  damages,  debts,
obligations,   and   liabilities   of  whatever   nature   (collectively,   "USC
Liabilities").  This Release extends to ali USC  Liabilities,  known or unknown,
now existing or existing mdy in the future,  matured or utunatured,  foreseeable
or urfforeseeable,  lo the extent that USC Liabilities result or arise, directly
or  indirectly,  frozn any  relationship(s)  of the USC Group or any' USC Member
with the Company  through the date of this Release  ("Relationships"),  or froth
any act of the USC Group or any USC Member on or before the date of this  Rel~se
("USC  Acts"),  as it relates to that  certain  Agreement  dated July 11,  1995.
Relationships  include,  but are not limited to,  ownership  of shares,  options
and/or warrants of the Company,  services  rendered under that certain Agreement
dated July 11, 1995,  by and between the Comprely and USC, and service  rendered
under any' and all other agreements  between the USC Group or any USC Member and
the  Company,  whether  oral or written,  express or implied.  USC Acts  include
without  limitation those that might give rise to liability in tort, in contract
or by statutory role.

     2. Release by the USC Group. The USC Group and each USC Member, jointly and
severally,  hereby and forever release, hold harmless and discharge the Company,
its past and present directors,  officers,  employees,  agents,  representative,
subsidiaries, '~liates, successors and assigns, from and against any all claims,
demands,  counterclaims,  actions,  costs,  causes of  action,  damages,  debts,
obligations,   and  liabilities  of  whatever  nature  (collectively,   "Company
Liabilities").  This Release extends to all matured or unmatured, foreseeable or
unforeseeable,  to the extent that Company LiabiliQes result or arise,  directly
or indirectly,  from an>'  Relationships,  or from any act of the Company or any
agent, representative, subsidiary, affiliate, successor or assign of the Company
on or before the date of this Release  ("Company  Acts"),  as it relates to that
certain Agreement dated July 11, 1995.  Company Acts include without  limitation
those that might give rise to  liability  in tort,  in eontract or by  statutory
rule.

     IN WITNESS WHREOF,  the parties hereto have executed this Mutual Release as
of the date and year first written above.

                              ENVIROMETRIC, S, INC.

                           By: Walter H. Elliott, III
                                 Its'. President

                            THE UNITED STATES COMPANY

                               RICHARD H. GUILFORD

                               MAURIZIO F. GIABBAI

                                  Individually

                                  ELSIE L. ROSE
                                  Individually

STATE OF SOUTH CAROLINA COUNTY OF CHARLESTON

MEMORANDUM OF AGREEMENT

THIS  AGREEMENT  is made as of this  24th day of  December,  1996,  by and among
ENVIROMETRICS,  INC, a corporation  organized and existing under the laws of the
State of Delaware,  THE UNITED  STATES  COMPANY,  a  corporation  organized  and
existing  under the laws of the  Commonwealth  of  Virginia  (USC),  RICHARD  H.
GUILFORD,  an individual resident of the Commonwealth of Virginia  ("Guilford"),
MAURIZIO  F.  GIABBAI,   an  individual   resident  of  the  State  Of  Georgia,
("Giabbai"),  and ELSIE L. ROSE, an individual  resident of the  Commonwealth of
Virginia  ("Rose")  (Guilford,  Giabbai,  and Rose being  referred to  sometimes
herein as a "USC  Principal" and  collectively  as the "USC  Principals"),  with
respect to all costs,  fees,  expenses or other  compensation owed to USC or any
USC  Principal  by   ENVIROMETRICS,   INC.  and/or  any  of  its  affiliates  or
subsidiaries (the "Company").

The parties to this Agreement agree as follows:

1. No fees,  expenses,  or  compensation  whether in the form of cash,  warrants
equity or other value, shall be due from this date forward by the Company to USC
or any USC Principal except (i) as expressly provided in this Agreement. (ii) as
previously agreed between the Company and USC as to compensation and expenses to
be paid to Rose for her  activities  as an  employee of the  Company,  and (iii)
reasonable  expenses  incurred after the date of this Agreement to be reimbursed
by the Company to USC or any USC Principal provided, however, such expenses must
be agreed  upon in advance  between or among the  Company and USC and/or the USC
Principals  prior to the  time  such  expenses  are  incurred  by USC or any USC
Principal.

2. The parties hereto agree that those two (2) certain Company  promissory notes
made payable to USC and dated on or about February 27, 1996, and August 12, I996
(collectively,  the "First Notes"), on which the Company, on or about October 5,
1996,  made a  partial  payment  of One  Hundred  Twenty-Five  Thousand  Dollars
($125,000.00),  are as of the date  hereof  fully  paid and the  collateral  (as
defined therein) securing the First Notes fully released, and that no other sums
shall be due or payable on account of the First Notes or the documents  executed
in  connection  therewith.   Further,  USC  and  the  USC  Principals  agree  to
immediately return all executed originals, proxies and/or instruments pertaining
to the First Notes and the  collateral  securing  the First Notes to the Company
for cancellation  and/or  destruction by the Company,  and to cooperate with all
reasonable  requests of the Company,  including  but not limited to delivery and
execution  of all  necessary  documents to cancel the First Notes and to release
the collateral.

3. The parties  hereto agree that the sum of the remaining  note payable and all
remaining  expenses and  compensation of any kind whatsoever owed by the Company
to  USC  or any  USC  Principal  is One  Hundred  Seventy-one  Thousand  Dollars
($171,000.00US).  The  Company  hereby  agrees  to pay to USC  the  said  amount
pursuant  to the  promissory  notes dated the date  hereof,  copies of which are
attached as Attachments B and C and expressly  incorporated herein by reference,
in the amount of One Hundred Seventy-One Thousand Dollars ($171,000.00 US) (the,
"New Notes"). The sums due under the New Notes shall be payable as follows:

Principal  of  Thirty-Five  Thousand  Dollars  ($35,000,00  US) shall be due and
payable at the time the Payor shall have received the cash proceeds from the Two
Hundred Fifty-Five  Thousand Dollars  ($255,000.00 US) second mortgage note held
by  Envirometrics,  Inc.,  that  resulted  from the sale of those  certain  real
properties  described in  Attachment A to this Note and  expressly  incorporated
herein by  reference.  Payor  will pay  interest  monthly  at the rate  Payee is
charged by  Regency  Bank (the  "Bank").  (Current  rate  charged by the Bank is
8.75%.)

Principal of One Hundred Thirty-Six  Thousand Dollars  ($136,000.00 US) shall be
due and payable in 60 equal  monthly  installments  of  $2,629.26  US  including
accrued interest thereon,  commeneing on January 15, 1997 and on each 15m day of
each month following  until all Remaining  Principal due under this Note is paid
in full;  provided,  in any event that all sums due  hereunder  shall be due and
payable on December 15, 2001 (the "Maturity Date"). The principal due under this
Note,  shall  bear  interest  at the rate of Six  Percent  (6%) per annum on the
Principal  outstanding  hereunder from time to time.  This note shall be paid to
the Payee  directly from the second  mortgage note interest  payments from James
Miller M.D,,  executed with the company on December 19, 1996. if such payment is
not received by the Company from James Miller,  M.D.,  or if James Miller,  M.D.
then interest only shall be due and payable under this note.

Any unpaid  principal  on the Notes  above shall be due and payable in full with
accrued interest thereon on the settlement date of any sale by the Payor, public
or private, of its securities of any character, if the net proceeds to the Payor
from such sate,  after the payment of fees and expenses  incurred in  connection
wkh the sale, equal or exceed the sum of $1,000,000.00 US.

To secure the repayment of all sums due under the New Notes,  the Company hereby
grants to USC,  pursuant to a security  agreement dated as of the date hereof, a
copy of which is attached as Attachment D and expressly  incorporated  herein by
reference  (the  "Security  Agreement"),  a security  interest in the  Company's
right,  title and interest in and to (i) that certain Promissory Note from Trico
Engineering   Consultants,   inc.,  formerly  Trico   Envirometrics,   Inc.,  to
Envirometrics,  Inc.  dated as of July 26,  1996,  as amended  from time to time
thereafter  in the amount of Six Hundred  Thousand  ($600,000.00  US), a copy of
which is  atittached as  Attachment E E_ and  expressly  incorporated  herein by
reference  (the "Trico  Note"),  and (1) that  certain  Pledge  Agreement by and
between Envkometrics,  Inc. and Andrew C. Gillette dated as of July 26, 1996, as
amended from time to time thereafter,  pursuant to which Gillette pledges to the
Company all of his interest in shares of Trico Envirometrics,  Inc. stock and in
options to purchase  shares of Company common stock, a copy of which is attached
as Attachment F and expressly  incorporated  herein by reference  (the "Gillette
Pledge Agreement").

5. The Company  shall  within a  reasonable  time  following  execution  of this
Agreement,  issue or cause  to be  issued  to USC,  pursuant  to the  reasonable
written  instructions of USC actually received by the Company prior to issuance,
one hundred  twenty-five  thousand  (125,000)  shares of validly  authorized and
previously  unissued  $. 001 par value  Common  Stock of the  Company  (the "USC
Shares"),  which stock  shall not on the date of  issuance to USC be  registered
under the,  Securities Act of 1933 'or under any state securities or other "blue
sky" laws, but which shall have the  Registration  Rights in Paragraph 9 hereof.
The  Company  shall,  in its  sole  discretion,determine  its  tax,  securities,
accounting and other reporting treatment of this transfer of shares,  whether as
(a) a conversion of a liability from USC and any USC Principal,  (b) an exchange
of  warrants,  options,  or other  rights held or  exercisable  by or  otherwise
belonging to USC or any USC Principal to Purchase or receive,  shares of Company
stock or warrants therefor,  or (c) any combination of (a) and (b), or any other
treatment acceptable to the Company's accountants (the "Treatment").

6. Except as  expressly  provided in this  Agreement,  and  notwithstanding  the
Treatment chosen by the Company pursuant to Paragraph 5 hereof,  as of this date
hereof,  any and all outstanding or unissued  options,  warrants or other rights
held or  exercisable  by or otherwise  belonging to USC or any USC  Principal to
purchase or receive shares or warrants of Company stock shall be null and 'void,
and any documents, proxies, or legal instruments providing for such rights shall
be immediately returned to the Company.

7'. In connection  with the closing of the matters agreed  herein,  the Company,
USC and the USC  Principals  shall  deliver  to each  other an  executed  mutual
release in the form  attached as Attachment G expressly  incorporated  herein by
reference.

8. Nothing in this  Agreement  shall affect the  employer/employee  relationship
previously  entered  into by and between  the  Company and Rose.  Rose agrees to
remain  employed by the Company  under the present  terms and  conditions of her
employment.  The Company  agrees to pay on a timely basis all of Rose's fees and
expenses  reasonably  relating to the business of the Company which are approved
by the Company prior to being incurred.

9. In the event that the Company at any time subsequent to the date the Exchange
Shares are issued to USC  hereunder  proposes to file a  registration  statement
(other  than a  registration  statement  on a Form  S-8 of Form  S-14,  or forms
similar  thereto in effect at the time of such filing) under the  Securities Act
of 1933 (as then in effect or any similar statute then in effect), in connection
with a proposed public offering of securities, the Company agrees to immediately
notify USC in writing,  at least thirty (30) days prior to such proposed  filing
date of such registration  statement.  Within 30 days following delivery of such
notice,   USC  may  request  that  the  Company  include  in  such  contemplated
registration  statement any shares of stock owned by USC (whether such ownership
is by virtue of issuance  pursuant to this agreement or pursuant to the exercise
of USers rights under the New Note and related documents).  Upon receipt of such
notice,  the  Company  will cause the  shares of stock made the  subject of such
request to be covered by the Company.

In addition, and without limiting the foregoing,  the Company agrees to register
at least Fifty Thousand  (50,000)  Exchange Shares of the Company stock owned by
USC or its  designee,  prior to June 30, 1997 (if so requested  by USC),  and to
register any remainder of the Exchange Shares so owned by USC on demand,  at any
time after December 31, 1997, the registration to be effective within sixty (60)
days following such written demand.

The Company will pay all expenses  reasonably  incurred by it and USC (including
USC's  attorney's  fees,  commissions  and fees of  underwriters or brokers with
respect  to the  shares  of the  stock  to be  registered  and  sold  by USC) in
connection  with the  registration  statement and any  post-effective  amendment
thereto  and  in  connection  with  qualifying  the  securities  covered  by the
registration  statement under the Blue Sky or other state  securities' laws. USC
shall furnish the Company and the Company  shall  furnish USC,  such  documents,
including  selling  notices  and  opinions  of  counsel,  as are  typically  and
reasonable  requested  and delivered by an issuer and selling  shareholder  in a
"piggy-back" or demand registration  transaction of the type outlined above. USC
and  the  Company,  respectively,   agree  to  provide  such  documentation  and
information on a timely basis to permit the registration  statement covering the
Exchange Shares and other shares of stock owned by USC to become  effective on a
prompt and orderly basis.

USC  agrees  to limit  the  number of  registered  shares it may sell  following
registration to no more than Twelve Thousand Five Hundred (12,500) shares during
any calendar month for the first two (2) years following registration.

10. This Agreement shall bind and inure to the benefit of the parties hereto and
to their respective personal representatives, heirs, successors or assigns.

11. If any term or provision of this Agreement  shall to any extent be held by a
court of competent jurisdiction to be invalid or unenforceable, the remainder of
this  Agreement,  or the  application of such invalid term or provision to other
persons or circumstances, shall not be affected thereby.

12. This Agreement  shall be governed by, and construed in accordance  with, the
laws of the State of South Carolina.  Any disputes under this Agreement shall be
settled only and  exclusively  in the Courts of the State of South  Carolina and
each of the parties  hereto consent to the exclusive  jurisdiction  and venue of
such Courts.

13. This  Agreement may be modified only by an agreement in writing and signed
by the party against whom enforcement of any waiver, charge, modification, or
discharge is sought.

14. All  representations and warranties,  covenants and amendments  contained in
this  Agreement and in all documents and  agreements  incorporated  herein shall
survive the execution of this Agreement.

15. The individuals  actually executing this Agreement  personally represent and
warrant  that they  have the  necessary  power and  authority  to  execute  this
Agreement in behalf of thc party they represent,  and that their  signatures are
sufficient to make this Agreement the binding and enforceable obligation of such
party.

16. This  document may be executed in any number of  counterparts  with the same
effect as if the signatures hereto and thereto are upon the same instrument,

17.  This  Agreement  has been  negotiated  by the Parties  hereto.  The Parties
represent and warrant to one another that each has actively  participated in the
finalization  of this  Agreement,  have been  represented  by and consulted with
counsel  of  their  choice,  and,  in the  event  of a  dispute  concerning  the
interpretation of this Agreement,  each Party hereby waives the doctrine that an
ambiguity  should be  interpreted  against  the  Party  which  has  drafted  the
document.

18. This Agreement  contains the entire agreement between the Parties hereto and
supersedes and emilnates any and all prior agreements and  understandings,  oral
or written,  between the  Parties  hereto with  respect to the matters set forth
herein.

19. The Parties hereto  understand and agree that that certain  contract between
Envirometrics, Inc..and The United States Company, dated as of July 11, 1995, as
the same may have been amended from time to time thereafter (the  "Contract") is
null and void, and that this  Agreement  supersedes and replaces the Contract in
every respect.

IN WITNESS  WHEREOF,  the Parties  hereto have  executed,  or caused their duly
authorized  agents to execute,  this  Agreement  the day and year first  written
above.

COMPANY: ENVIROMETRICS, INC.

Walter H. Elliott, III President

USC: THE UNITED STATES COMPANY

President

GUILFORD: RICHARD

GIABBAI:    MAURIZIO F. GIABBAI

Individually ROSE: ELSIE L. ROSE Individually<PAGE>
                                                                    Exhibit 10.1

                                                                  EXECUTION COPY

                      AMENDED AND RESTATED LOAN AGREEMENT

                                     AMONG

                             AMERICAN TOWER, L.P.,
                             AMERICAN TOWERS, INC.
                                      AND
                             ATC TELEPORTS, INC.,

                                 AS BORROWERS;

                 THE FINANCIAL INSTITUTIONS WHOSE NAMES APPEAR
                   AS LENDERS ON THE SIGNATURE PAGES HEREOF;

                  THE TORONTO DOMINION BANK, NEW YORK BRANCH,
                               AS ISSUING BANK,

                                      AND

                        TORONTO DOMINION (TEXAS), INC.,
                            AS ADMINISTRATIVE AGENT
                               FOR THE LENDERS;

                                     WITH

              TD SECURITIES (USA) INC. AND CHASE SECURITIES INC.,
                  AS CO-LEAD ARRANGERS AND CO-BOOK MANAGERS;

                THE BANK OF NEW YORK AND CHASE SECURITIES INC.,
                           AS CO-SYNDICATION AGENTS;

                                      AND

                          CREDIT SUISSE FIRST BOSTON,
                            AS DOCUMENTATION AGENT;

                          Dated as of January 6, 2000

                    Powell, Goldstein, Frazer & Murphy LLP
                               Atlanta, Georgia
<PAGE>

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                              Page
<S>                                                                                           <C>
ARTICLE 1   DEFINITIONS.....................................................................     2

     Section 1.1   Definitions..............................................................     2
     Section 1.2   Interpretation...........................................................    30
     Section 1.3   Cross References.........................................................    30
     Section 1.4   Accounting Provisions....................................................    30

ARTICLE 2   LOANS...........................................................................    31

     Section 2.1   The Loans................................................................    31
     Section 2.2   Manner of Borrowing and Disbursement.....................................    31
     Section 2.3   Interest.................................................................    34
     Section 2.4   Commitment Fees..........................................................    36
     Section 2.5   Mandatory Commitment Reductions..........................................    38
     Section 2.6   Voluntary Commitment Reductions..........................................    40
     Section 2.7   Prepayments and Repayments...............................................    40
     Section 2.8   Notes; Loan Accounts.....................................................    43
     Section 2.9   Manner of Payment........................................................    43
     Section 2.10  Reimbursement............................................................    45
     Section 2.11  Pro Rata Treatment.......................................................    45
     Section 2.12  Capital Adequacy.........................................................    46
     Section 2.13  Bank Tax Forms...........................................................    46
     Section 2.14  Letters of Credit........................................................    47
     Section 2.15  Incremental Facility Advances............................................    52

ARTICLE 3   CONDITIONS PRECEDENT............................................................    53

     Section 3.1   Conditions Precedent to Effectiveness of this Agreement..................    53
     Section 3.2   Conditions Precedent to Each Advance.....................................    57
     Section 3.3   Conditions Precedent to Issuance of Letters of Credit....................    58

ARTICLE 4   REPRESENTATIONS AND WARRANTIES..................................................    58

     Section 4.1   Representations and Warranties...........................................    58
     Section 4.2   Survival of Representations and Warranties, Etc..........................    65

ARTICLE 5   GENERAL COVENANTS...............................................................    65

     Section 5.1   Preservation of Existence and Similar Matters............................    66
     Section 5.2   Business; Compliance with Applicable Law.................................    66
     Section 5.3   Maintenance of Properties................................................    66
     Section 5.4   Accounting Methods and Financial Records.................................    66
     Section 5.5   Insurance................................................................    66
     Section 5.6   Payment of Taxes and Claims..............................................    67
     Section 5.7   Compliance with ERISA....................................................    67
     Section 5.8   Visits and Inspections...................................................    69
     Section 5.9   Payment of Indebtedness; Loans...........................................    69
     Section 5.10  Use of Proceeds..........................................................    69
</TABLE>
<PAGE>

<TABLE>
<S>                                                                                                          <C>
     Section 5.11  Indemnity..............................................................................   70
     Section 5.12  Interest Rate Hedging..................................................................   70
     Section 5.13  Covenants Regarding Formation of Restricted Subsidiaries and Acquisitions;
                   Partnership, Subsidiaries..............................................................   71
     Section 5.14  Payment of Wages.......................................................................   72
     Section 5.15  Further Assurances.....................................................................   72
     Section 5.16  Special Purpose Subsidiaries...........................................................   72

ARTICLE 6  INFORMATION COVENANTS..........................................................................   73

     Section 6.1   Quarterly Financial Statements and Information.........................................   73
     Section 6.2   Annual Financial Statements and Information............................................   73
     Section 6.3   Performance Certificates...............................................................   73
     Section 6.4   Copies of Other Reports................................................................   74
     Section 6.5   Notice of Litigation and Other Matters.................................................   75

ARTICLE 7  NEGATIVE COVENANTS............................................................................    76

     Section 7.1   Indebtedness of the Borrowers and the Restricted Subsidiaries..........................   76
     Section 7.2   Limitation on Liens....................................................................   77
     Section 7.3   Amendment and Waiver...................................................................   77
     Section 7.4   Liquidation, Merger or Disposition of Assets...........................................   77
     Section 7.5   Limitation on Guaranties...............................................................   78
     Section 7.6   Investments and Acquisitions...........................................................   78
     Section 7.7   Restricted Payments....................................................................   80
     Section 7.8   Leverage Ratio.........................................................................   80
     Section 7.9   Interest Coverage Ratio................................................................   81
     Section 7.10  Annualized Operating Cash Flow to Pro Forma Debt Service...............................   82
     Section 7.11  Fixed Charge Coverage Ratio............................................................   82
     Section 7.12  Affiliate Transactions.................................................................   82
     Section 7.13  ERISA Liabilities......................................................................   82
     Section 7.14  Sales and Leasebacks...................................................................   82

ARTICLE 8  DEFAULT........................................................................................   82

     Section 8.1   Events of Default......................................................................   82
     Section 8.2   Remedies...............................................................................   86
     Section 8.3   Payments Subsequent to Declaration of Event of Default.................................   88

ARTICLE 9  THE ADMINISTRATIVE AGENT.......................................................................   88

     Section 9.1   Appointment and Authorization..........................................................   88
     Section 9.2   Interest Holders.......................................................................   89
     Section 9.3   Consultation with Counsel..............................................................   89
     Section 9.4   Documents..............................................................................   89
     Section 9.5   Administrative Agent and Affiliates....................................................   89
     Section 9.6   Responsibility of the Administrative Agent and Issuing Bank............................   89
     Section 9.7   Action by the Administrative Agent and Issuing Bank....................................   90
</TABLE>

                                     -ii-
<PAGE>

<TABLE>
<S>                                                                                             <C>
     Section 9.8    Notice of Default or Event of Default...................................    90
     Section 9.9    Responsibility Disclaimed...............................................    91
     Section 9.10   Indemnification.........................................................    91
     Section 9.11   Credit Decision.........................................................    91
     Section 9.12   Successor Administrative Agent..........................................    92
     Section 9.13   Delegation of Duties....................................................    92

ARTICLE 10 CHANGES IN CIRCUMSTANCES AFFECTING LIBOR ADVANCES AND INCREASED
           COSTS............................................................................    93

     Section 10.1   LIBOR Basis Determination Inadequate or Unfair..........................    93
     Section 10.2   Illegality..............................................................    93
     Section 10.3   Increased Costs.........................................................    93
     Section 10.4   Effect On Other Advances................................................    95

ARTICLE 11 MISCELLANEOUS....................................................................    96

     Section 11.1   Notices.................................................................    96
     Section 11.2   Expenses................................................................    97
     Section 11.3   Waivers.................................................................    97
     Section 11.4   Set-Off.................................................................    98
     Section 11.5   Assignment and Participation............................................    99
     Section 11.6   Accounting Principles...................................................   103
     Section 11.7   Counterparts............................................................   103
     Section 11.8   Governing Law...........................................................   103
     Section 11.9   Severability............................................................   104
     Section 11.10  Interest................................................................   104
     Section 11.11  Table of Contents and Headings..........................................   104
     Section 11.12  Amendment and Waiver....................................................   104
     Section 11.13  Entire Agreement........................................................   105
     Section 11.14  Other Relationships.....................................................   105
     Section 11.15  Directly or Indirectly..................................................   105
     Section 11.16  Reliance on and Survival of Various Provisions..........................   105
     Section 11.17  Senior Debt.............................................................   105
     Section 11.18  Obligations.............................................................   105
     Section 11.19  Confidentiality.........................................................   105

ARTICLE 12 WAIVER OF JURY TRIAL.............................................................   106

     Section 12.1   Waiver of Jury Trial....................................................   106
</TABLE>

                                     -iii-
<PAGE>

                                   EXHIBITS

     Exhibit A      Form of Assignment of General Partner Interests
     Exhibit B      Form of Assignment of Intercompany Note
     Exhibit C      Form of Assignment of Limited Partner Interests
     Exhibit D      Form of Borrower's Guaranty
     Exhibit E      Form of Certificate of Financial Condition
     Exhibit F      Form of Notice of Incremental Facility Commitments
     Exhibit G      Form of Parent Guaranty
     Exhibit H      Form of Parent Pledge Agreement
     Exhibit I      Form of Request for Advance
     Exhibit J      Form of Request for Issuance of Letter of Credit
     Exhibit K      Form of Revolving Loan Promissory Note
     Exhibit L      Form of Security Agreement
     Exhibit M      Form of Stock Pledge Agreement
     Exhibit N      Form of Subordination Agreement
     Exhibit O      Form of Subsidiary Guaranty
     Exhibit P      Form of Subsidiary Pledge Agreement
     Exhibit Q      Form of Subsidiary Security Agreement
     Exhibit R      Form of Term Loan A Promissory Note
     Exhibit S      Form of Term Loan B Promissory Note
     Exhibit T      Form of Incremental Facility Note
     Exhibit U      Form of Loan Certificate of AT L.P.
     Exhibit V      Form of AT Inc./ATC Teleports Loan Certificate
     Exhibit W      Form of Parent Loan Certificate
     Exhibit X      Form of Subsidiary Loan Certificate
     Exhibit Y      Form of Performance Certificate
     Exhibit Z      Form of Assignment and Assumption Agreement

                                   SCHEDULES

     Schedule 1   - Licenses
     Schedule 2   - Restricted Subsidiaries and Unrestricted Subsidiaries on the
                    Agreement Date
     Schedule 3   - Exceptions to Representations and Warranties
     Schedule 4   - Litigation
     Schedule 5   - Affiliate Transactions
     Schedule 6   - Indebtedness for Money Borrowed
     Schedule 7   - Commitment Ratios, Lender Names and Notice Addresses

                                     -iv-

<PAGE>

                      AMENDED AND RESTATED LOAN AGREEMENT
                                     AMONG
                             AMERICAN TOWER, L.P.,
                             AMERICAN TOWERS INC.
                                      AND
                             ATC TELEPORTS, INC.,
                                 AS BORROWERS;
                 THE FINANCIAL INSTITUTIONS WHOSE NAMES APPEAR
                   AS LENDERS ON THE SIGNATURE PAGES HEREOF;
                  THE TORONTO DOMINION BANK, NEW YORK BRANCH,
                               AS ISSUING BANK;
                                      AND
                        TORONTO DOMINION (TEXAS), INC.,
                   AS ADMINISTRATIVE AGENT FOR THE LENDERS;
                                     WITH
              TD SECURITIES (USA) INC. AND CHASE SECURITIES INC.,
                  AS CO-LEAD ARRANGERS AND CO-BOOK MANAGERS;
                THE BANK OF NEW YORK AND CHASE SECURITIES INC.,
                           AS CO-SYNDICATION AGENTS;
                                      AND
                          CREDIT SUISSE FIRST BOSTON,
                            AS DOCUMENTATION AGENT

     WHEREAS, the Administrative Agent and the Lenders have agreed to amend and
restate the Prior Loan Agreement (as hereinafter defined) in its entirety, as
more fully set forth in this Agreement; and

     WHEREAS, each of the Borrowers acknowledges and agrees that the Security
Interest (as hereinafter defined) granted to the Administrative Agent, for
itself and on behalf of the Lenders, pursuant to certain security documents
executed in connection therewith shall remain outstanding and in full force and
effect and shall continue to secure the Obligations (as hereinafter defined);
and

     WHEREAS, each of the Borrowers acknowledges and agrees that: (i) the
Obligations (as hereinafter defined) represent, among other things, the
amendment, restatement, renewal, extension, consolidation and modification of
the Obligations (as defined in the Prior Loan Agreement) arising in connection
with the Prior Loan Agreement and the Security Documents executed in connection
with the Prior Loan Agreement; (ii) the parties hereto intend that the
collateral pledged in connection with the Prior Loan Agreement shall secure,
without interruption or impairment of any kind, all existing Indebtedness under
the Prior Loan Agreement and the Security Documents executed in connection with
the Prior Loan Agreement, as so amended, restated, restructured, renewed,
extended, consolidated and modified hereunder, together with Obligations (as
hereinafter defined), (iii) all Liens evidenced by the security documents
executed in connection with the Prior Loan Agreement are hereby ratified,
confirmed and continued; and (iv) the Loan Documents (as hereinafter defined)
are intended to restructure,
<PAGE>

restate, renew, extend, consolidate, amend and modify the Prior Loan Agreement
and the Security Documents executed in connection therewith; and

     NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged by each of the parties hereto, the
parties hereby amend and restate the Prior Loan Agreement as follows:

                             ARTICLE 1 Definitions

     Section 1.1  Definitions.  For the purposes of this Agreement:
                  -----------

     "116 Huntington" shall mean ATC Realty, Inc., a Delaware corporation.
      --------------

     "Acquisition" shall mean (whether by purchase, lease, exchange, issuance of
      -----------
stock or other equity or debt securities, merger, reorganization or any other
method) (i) any acquisition of any other Person by any Borrower or any of the
Restricted Subsidiaries, which Person shall then become consolidated with any
Borrower or any of the Restricted Subsidiaries in accordance with GAAP; (ii) any
acquisition by any Borrower or any of the Restricted Subsidiaries of all or any
substantial part of the assets of any other Person;  (iii) any acquisition by
any Borrower or any of the Restricted Subsidiaries of any business (or related
contracts) primarily involving the management of communications sites, towers or
other facilities for third parties, other than in any such case described in
clauses (i) through (iii) any such Acquisition which shall be made by, or of,
any Person which shall have been designated and, to the extent required hereby,
approved as an Unrestricted Subsidiary or (iv) any acquisition by any Borrower
or any of the Restricted Subsidiaries of any communications towers or
communications tower sites.

     "Acquisition Operating Cash Flow" shall mean in the case of an Acquisition
      -------------------------------
permitted hereunder, Operating Cash Flow (Developing Towers), Operating Cash
Flow (Mature Towers) and Operating Cash Flow (Other Business), as applicable, of
the Borrowers and their Restricted Subsidiaries for the period during which such
Acquisition occurs, adjusted to give effect to such Acquisition, as if such
Acquisition had occurred on the first day of such period, by excluding the
Operating Cash Flow (Developing Towers), Operating Cash Flow (Mature Towers) and
Operating Cash Flow (Other Business), as applicable, of such Acquisition during
such period prior to and including the date of such Acquisition and adding to
the Operating Cash Flow (Developing Towers), Operating Cash Flow (Mature Towers)
and Operating Cash Flow (Other Business), as applicable, of the Borrowers and
their Restricted Subsidiaries, if positive, or subtracting from such Operating
Cash Flow (Developing Towers), Operating Cash Flow (Mature Towers) and Operating
Cash Flow (Other Business), as applicable, if negative, the product of (i) the
actual Operating Cash Flow (Developing Towers), Operating Cash Flow (Mature
Towers) and Operating Cash Flow (Other Business), as applicable, of such
Acquisition for that portion of such period from the date of such Acquisition to
the last day of such period, multiplied by (ii) a fraction the numerator of
which is the number of calendar days in such period and the denominator of which
is the number of days in such period from and including the date following such
Acquisition through the last day of such period.

                                      -2-
<PAGE>

     "Administrative Agent" shall mean Toronto Dominion (Texas), Inc., in its
      --------------------
capacity as Administrative Agent for the Lenders and the Issuing Bank, or any
successor Administrative Agent appointed pursuant to Section 9.12 hereof.

     "Administrative Agent's Office" shall mean the office of the Administrative
      -----------------------------
Agent located at 909 Fannin Street, Suite 1700, Houston Texas 77010, or such
other office as may be designated pursuant to the provisions of Section 11.1
hereof.

     "Advance" shall mean the aggregate amounts advanced by the Lenders to any
      -------
Borrower pursuant to Article 2 hereof on the occasion of any borrowing and
having the same Interest Rate Basis and Interest Period; and "Advances" shall
                                                              --------
mean more than one Advance.

     "Affiliate" shall mean, with respect to a Person, any other Person directly
      ---------
or indirectly controlling, controlled by, or under common control with, such
first Person.  For purposes of this definition, "control", when used with
respect to any Person, includes, without limitation, the direct or indirect
beneficial ownership of more than ten percent (10%) of the voting securities or
voting equity of such Person or the power to direct or cause the direction of
the management and policies of such Person whether by contract or otherwise.

     "Agreement" shall mean this Amended and Restated Loan Agreement, as
      ---------
amended, supplemented, restated or otherwise modified from time to time.

     "Agreement Date" shall mean January 6, 2000.
      --------------

     "AirTouch" shall mean Vodafone AirTouch Plc, formerly known as AirTouch
      --------
Communications, Inc., a Delaware corporation.

     "AirTouch Agreement to Sublease" shall mean that certain Agreement to
      ------------------------------
Sublease dated August 6, 1999 by and among AirTouch, the Sublessors (as defined
therein), the Parent and AT L.P.

     "AirTouch Build to Suit Agreement" shall mean that certain Site Development
      --------------------------------
and Build-to-Suit Agreement by and among AirTouch, AT L.P. and the Parent
entered into pursuant to the AirTouch Agreement to Sublease.

     "AirTouch Sublease" shall mean, collectively, any master lease, lease or
      -----------------
sublease entered into pursuant to the AirTouch Agreement to Sublease.

     "AirTouch Towers" shall mean, collectively, all towers operated by the
      ---------------
Borrowers or any of the Restricted Subsidiaries pursuant to the AirTouch
Sublease, which towers have been operated by the Borrowers or the Restricted
Subsidiaries for less than twelve (12) calendar months and excluding all towers
constructed by the Borrowers or any of the Restricted Subsidiaries pursuant to
the AirTouch Build to Suit Agreement.

                                      -3-
<PAGE>

     "Annualized Operating Cash Flow" shall mean, as of any calculation date,
      ------------------------------
(a) the sum of (i) the product of (A) Operating Cash Flow (Mature Towers) for
the fiscal quarter-end being tested, or the most recently completed fiscal
quarter immediately preceding such calculation date, as the case may be, times
                                                                         -----
(B) four (4); and (ii) the product of (A) Operating Cash Flow (Developing
Towers) for the fiscal quarter-end being tested, or the most recently completed
fiscal quarter immediately preceding such calculation date, as the case may be,
times (B) four (4); and (iii) Operating Cash Flow (Other Business) for the four
-----
fiscal quarter period end being tested or the most recently completed four (4)
fiscal quarter period immediately preceding such calculation date, as the case
may be; minus (b) corporate overhead (exclusive of amortization and
        -----
depreciation) of the Borrowers and the Restricted Subsidiaries (on a
consolidated basis) for the four (4) fiscal quarter period then ended or, the
most recently completed four (4) fiscal quarter period immediately preceding the
calculation date, as the case may be; provided, however, that for purposes of
                                      --------  -------
calculating the Leverage Ratio and Borrowing Base Cash Flow only, item (a)(iii)
above shall (1) be reduced by twenty-five percent (25%) and (2) exclude interest
income received in respect of the loan made to TV Azteca described in Section
7.6(f) hereof; and provided further, however, that Annualized Operating Cash
                   -------- -------  -------
Flow shall exclude operating cash flow attributable to Unisite, to the extent
that the restrictions in the Unisite Notes on the ability of Unisite to make
Restricted Payments to the Borrowers are in effect.

     "Applicable Law" shall mean, in respect of any Person, all provisions of
      --------------
constitutions, statutes, rules, regulations and orders of governmental bodies or
regulatory agencies applicable to such Person, including, without limiting the
foregoing, the Licenses, the Communications Act, zoning ordinances and all
Environmental Laws, and all orders, decisions, judgments and decrees of all
courts and arbitrators in proceedings or actions to which the Person in question
is a party or by which it is bound.

     "Applicable Margin" shall mean the interest rate margin applicable to Base
      -----------------
Rate Advances and LIBOR Advances, as the case may be, in each case determined in
accordance with Section 2.3(f) hereof.

     "Approved Fund" means, with respect to any Lender that is a fund that
      -------------
invests in commercial loans, any other fund that invests in commercial loans and
is managed by the same investment advisor as such Lender or by an Affiliate of
such investment advisor.

     "Assignment of General Partner Interests" shall mean that certain Amended
      ---------------------------------------
and Restated Assignment of General Partner Interests, dated the Agreement Date,
made by ATC GP in favor of the Administrative Agent, substantially in the form
of Exhibit A attached hereto.
   ---------

     "Assignments of Intercompany Notes" shall mean, collectively, that certain
      ---------------------------------
Assignment of Intercompany Note of ATC Operating and that certain Assignment of
Intercompany Note of ATC Holding, each dated the Agreement Date in favor of the
Administrative Agent, substantially in the form of Exhibit B attached hereto.
                                                   ---------

                                     -4-
<PAGE>

     "Assignment of Limited Partner Interests" shall mean that certain Amended
      ---------------------------------------
and Restated Assignment of Limited Partner Interests, dated the Agreement Date,
made by ATC LP in favor of the Administrative Agent, substantially in the form
of Exhibit C attached hereto.
   ---------

     "AT L.P." shall mean American Tower, L.P., a Delaware limited partnership
      -------
and one of the Borrowers.

     "AT Inc." shall mean American Towers, Inc., a Delaware corporation and one
      -------
of the Borrowers.

     "AT&T" shall mean AT&T Corporation, a New York corporation.
      ----

     "AT&T Towers" shall mean, collectively, the towers acquired by the
      -----------
Borrowers or any of the Restricted Subsidiaries pursuant to that certain
Purchase and Sale Agreement dated as of September 10, 1999 by and between AT&T
and the Parent, which towers have been operated by the Borrowers and the
Restricted Subsidiaries for less than twelve (12) calendar months.

     "ATC GP" shall mean ATC GP Inc., a Delaware corporation and a wholly-owned
      ------
subsidiary of ATC Holding.

     "ATC GP Guaranty" shall mean that certain Amended and Restated Guaranty,
      ---------------
dated the Agreement Date, made by ATC GP in favor of the Administrative Agent,
the Lenders and the Issuing Bank, in form and substance reasonably satisfactory
to the Administrative Agent.

     "ATC GP Security Agreement"  shall mean that certain Amended and Restated
      -------------------------
Security Agreement dated the Agreement Date, between ATC GP and the
Administrative Agent, for itself and on behalf of the Lenders and the Issuing
Bank, in form and substance reasonably satisfactory to the Administrative Agent.

     "ATC Holding" shall mean ATC Holding Inc., a Delaware corporation and a
      -----------
wholly-owned Subsidiary of the Parent.

     "ATC Holding Guaranty" shall mean that certain Amended and Restated
      --------------------
Guaranty, dated the Agreement Date, made by ATC Holding in favor of the
Administrative Agent, the Lenders and the Issuing Bank, in form and substance
reasonably satisfactory to the Administrative Agent.

     "ATC Holding Security Agreement"  shall mean that certain Amended and
      ------------------------------
Restated Security Agreement dated the Agreement Date, between ATC Holding and
the Administrative Agent, for itself and on behalf of the Lenders and the
Issuing Bank, in form and substance reasonably satisfactory to the
Administrative Agent.

     "ATC LP" shall mean ATC LP Inc., a Delaware corporation and a wholly-owned
      ------
Subsidiary of ATC Operating.

                                      -5-
<PAGE>

     "ATC Operating" shall mean ATC Operating Inc., a Delaware corporation and a
      -------------
wholly-owned Subsidiary of AT Inc.

     "ATC Teleports" shall mean ATC Teleports, Inc., a Delaware corporation, a
      -------------
wholly-owned Subsidiary of the Parent and one of the Borrowers.

     "Authorized Signatory" shall mean such senior personnel of a Person as may
      --------------------
be duly authorized and designated in writing by such Person to execute
documents, agreements and instruments on behalf of such Person.

     "Available Letter of Credit Commitment" shall mean, at any time, the lesser
      -------------------------------------
of (a) (i) $50,000,000.00 minus (ii) all Letter of Credit Obligations then
                          -----
outstanding, and (b) the Available Revolving Loan Commitment then in effect.

     "Available Revolving Loan Commitment" shall mean, as of any date, the
      -----------------------------------
lesser of (a)(i) the Revolving Loan Commitments in effect on such date minus
                                                                       -----
(ii) the sum of (A) the Revolving Loans then outstanding plus (B) the Letter of
                                                         ----
Credit Obligations then outstanding, and (b)(i) the Borrowing Base on such date
minus (ii) the sum of (A) all Loans then outstanding (together with all Term
-----
Loan A Loans to be advanced on such date) plus (B) the Letter of Credit
                                          ----
Obligations then outstanding; provided, however, that for all times on and after
                              --------  -------
the Borrowing Base Termination Date, Available Revolving Loan Commitment shall
be determined using only clause (a) of this definition.

     "Available Term Loan A Commitment" shall mean, as of any date (and subject
      --------------------------------
to Section 2.1(b) hereof), the lesser of (a)  (i) the Term Loan A Commitments in
effect on such date minus (ii) the Term Loan A Loans then outstanding, and
                    -----
(b)(i) the Borrowing Base on such date minus (ii) the sum of (A) all Loans then
                                       -----
outstanding (together with all Revolving Loans to be advanced on such date) plus
                                                                            ----
(B) the Letter of Credit Obligations then outstanding; provided, however, that
                                                       --------  -------
for all times on and after the Borrowing Base Termination Date, Available Term
Loan A Commitment shall be determined using only clause (a) of this definition.

     "Available Term Loan B Commitment" shall mean, as of the Agreement Date,
      --------------------------------
the lesser of (a) the Term Loan B Commitments in effect on such date, and (b)(i)
the Borrowing Base on such date minus (ii) the sum of (A) all Loans other than
                                -----
Term Loan B Loans to be advanced on the Agreement Date plus (B) the Letters of
                                                       ----
Credit outstanding or to be issued on the Agreement Date.

     "Base Rate" shall mean, at any time, a fluctuating interest rate per annum
      ---------
equal to the higher of (a) the rate of interest quoted from time to time by the
Administrative Agent as its "prime rate" or "base rate" or (b) the sum of (i)
the Federal Funds Rate plus (ii) one-half of one percent (1/2%).  The Base Rate
                       ----
is not necessarily the lowest rate of interest charged by the Administrative
Agent in connection with extensions of credit.

     "Base Rate Advance" shall mean an Advance which any Borrower requests to be
      -----------------
made as a Base Rate Advance or is Converted to a Base Rate Advance, in
accordance with the provisions

                                      -6-
<PAGE>

of Section 2.2 hereof, and which shall be in a principal amount of at least
$1,000,000.00 and in an integral multiple of $500,000.00.

     "Base Rate Basis" shall mean a simple interest rate equal to the sum of (i)
      ---------------
the Base Rate and (ii) the Applicable Margin applicable to Base Rate Advances
for the applicable Loans.  The Base Rate Basis shall be adjusted automatically
as of the opening of business on the effective date of each change in the Base
Rate to account for such change, and shall also be adjusted to reflect changes
of the Applicable Margin applicable to Base Rate Advances.

     "Borrowers" shall mean, collectively, AT L.P., AT Inc. and ATC Teleports,
      ---------
and shall include Kline Steel and such other Persons as may be approved by the
Majority Lenders at such time as any such Person executes and delivers to the
Administrative Agent an assignment and assumption agreement in form and
substance satisfactory to the Administrative Agent and each other Loan Document
as executed by the other Borrowers; and "Borrower" shall mean any one of the
                                         --------
foregoing.

     "Borrower Guaranties" shall mean, collectively, that certain Amended and
      -------------------
Restated Borrower Guaranty (AT Inc.), that certain Amended and Restated Borrower
Guaranty (AT L.P.), and that certain Borrower Guaranty (ATC Teleports), each
dated the Agreement Date and each substantially in the form of Exhibit D
                                                               ---------
attached hereto.

     "Borrowing Base" shall mean, for the period from the Agreement Date
      --------------
through, but not including, the Borrowing Base Termination Date, the sum of:

          (a) the product of (i) seven and three-quarters (7.75) times (ii)
Borrowing Base Cash Flow for the immediately preceding fiscal quarter; plus
                                                                       ----

          (b) the lesser of (i) sixty percent (60%) of actual construction costs
for all Developing Towers constructed by any of the Borrowers or the Restricted
Subsidiaries and (ii) the aggregate of $110,000.00 per tower for such Developing
Towers; plus
        ----

          (c) the product of (i) $120,000.00 times (ii) the aggregate number of
Developing Towers acquired by any of the Borrowers or the Restricted
Subsidiaries (excluding AirTouch Towers and excluding AT&T Towers acquired in
excess of 1,000 towers); plus
                         ----

          (d) the product of (i) $130,000.00 times (ii) the number of AirTouch
Towers; plus
        ----

          (e) with respect to any towers not included in (b), (c) or (d) above,
such amounts as agreed to by the Majority Lenders;

provided, however, that, notwithstanding the foregoing, in calculating the
--------  -------
Borrowing Base, the sum of items (b), (c), (d) and (e) of this definition shall
not exceed $625,000,000.00.

                                      -7-
<PAGE>

     "Borrowing Base Cash Flow" shall mean, as of any calculation date, the sum
      ------------------------
of (a) (i) Annualized Operating Cash Flow minus (ii) the product of (A)
                                          -----
Operating Cash Flow (Developing Towers) for the fiscal quarter-end being tested,
or the most recently completed fiscal quarter immediately preceding such
calculation date, as the case may be, times (B) four (4), plus (b) corporate
                                      -----               ----
overhead reasonably satisfactory to the Administrative Agent (exclusive of
amortization and depreciation) with respect to Developing Towers of the
Borrowers and the Restricted Subsidiaries on a consolidated basis for the four
(4) fiscal quarter period then ended, or the most recently completed four (4)
fiscal quarter period immediately preceding the calculation date, as the case
may be.

     "Borrowing Base Termination Date" shall mean the earlier to occur of (a)
      -------------------------------
July 1, 2001 and (b) such date as the Borrowers elect in writing to the
Administrative Agent to terminate the use of the Borrowing Base formula and
convert to a borrowing limitation tied to the Leverage Ratio restrictions set
forth in Section 7.8 hereof.

     "Broker/Dealer" shall mean, with respect to any Investment permitted under
      -------------
Section 7.6(a) hereof, (a) any broker/dealer (acting as principal) registered as
a broker or a dealer under Section 15 of the Exchange Act, the unsecured short-
term debt obligations of which are rated "P-1" by Moody's and at least "A-1" by
Standard and Poor's at the time of entering into such Investment or Acquisition
or (b) an unrated broker/dealer, acting as principal, that is a wholly-owned
Subsidiary of a non-bank or bank holding company, the unsecured short-term debt
obligations of which are rated "P-1" by Moody's and at least "A-1" by Standard
and Poor's at the time of entering into such Investment or Acquisition.

     "Business Day" shall mean a day on which banks and foreign exchange markets
      ------------
are open for the transaction of business required for this Agreement in Houston,
Texas, New York, New York and London, England, as relevant to the determination
to be made or the action to be taken.

     "Capital Expenditures" shall mean, for any period, expenditures (including,
      --------------------
without limitation, the aggregate amount of Capitalized Lease Obligations
required to be paid during such period) incurred by any Person to acquire or
construct fixed assets, plant and equipment (including, without limitation,
renewals, improvements and replacements, but excluding repairs and maintenance)
during such period, that would be required to be capitalized on the balance
sheet of such Person in accordance with GAAP.

     "Capital Raise Proceeds" shall mean, (a) at any time prior to the Borrowing
      ----------------------
Base Termination Date, (i) fifty percent (50%) of the net cash proceeds of any
public or private sale or issuance of the Capital Stock of the Parent in excess
of $100,000,000.00 in the aggregate after the Agreement Date, and (ii) one
hundred percent (100%) of the net cash proceeds of any public or private sale or
issuance of debt instruments of the Parent, any of the Borrowers or any of the
Restricted Subsidiaries (other than (A) net proceeds in an amount not to exceed
$2,000,000.00 in the aggregate after the Agreement Date from the sale or
issuance of Capital Stock in connection with any employee stock option plan of
any such Person, (B) debt among the Borrowers and the Restricted Subsidiaries,
or any of them, (C) the Loans or (D) proceeds received from Capital Stock issued
in connection with an Acquisition hereunder), (b) at any time on or after the

                                      -8-
<PAGE>

Borrowing Base Termination Date when the Leverage Ratio is greater than 5.00 to
1.00 fifty percent (50%) of the net proceeds of any public or private sale or
issuance of debt instruments of the Parent, any of the Borrowers or any of the
Restricted Subsidiaries debt among the Borrowers and the Restricted
Subsidiaries, or any of them, or (B) the Loans), or, (c) at any other time, zero
(0).

     "Capital Stock" shall mean, as applied to any Person, any capital stock of
      -------------
such Person, regardless of class or designation, and all warrants, options,
purchase rights, conversion or exchange rights, voting rights, calls or claims
of any character with respect thereto.

     "Capitalized Lease Obligation" shall mean that portion of any obligation of
      ----------------------------
a Person as lessee under a lease which at the time would be required to be
capitalized on the balance sheet of such lessee in accordance with GAAP.

     "Certificate of Financial Condition" shall mean certificates, substantially
      ----------------------------------
in the form of Exhibit E attached hereto, signed by the chief financial officer
               ---------
of each Borrower, as appropriate, together with any schedules, exhibits or
annexes appended thereto.

     "Change of Control" shall mean (a) the failure of the Parent to own,
      -----------------
directly or indirectly, (i) one hundred percent (100%) of the ownership
interests of each of AT L.P. and AT Inc. and (ii) ninety percent (90%) of the
ownership interests of each of  ATC Teleports and Kline Steel, provided that the
                                                               --------
remaining ten percent (10%) of each such Person is held by other Persons in
connection with an employee stock option plan, (b) the failure of AT Inc. to
own, directly or indirectly, one hundred percent (100%) of the ownership
interests of ATC Operating (unless ATC Operating is merged with or into AT
Inc.), (c) the sale, lease, transfer, in one or a series of related
transactions, of all or substantially all of any of the Borrower's assets to any
Person or group (as such term is used in Section 13(d)(3) of the Exchange Act)
other than to the other Borrowers or any wholly-owned direct or indirect
Restricted Subsidiary of AT Inc., (d) the adoption of a plan relating to the
liquidation or dissolution of the Parent, (e) the acquisition, directly or
indirectly, by any Person or group (as such term is used in Section 13(d)(3) of
the Exchange Act) of forty percent (40%) or more of the voting power of the
voting stock of the Parent by way of merger or consolidation or otherwise and
such Persons own more voting power than the Principal Shareholders, or (f) the
Continuing Directors cease for any reason to constitute a majority of the
directors of the Parent then in office.

     "Code" shall mean the Internal Revenue Code of 1986, as amended from time
      ----
to time.

     "Collateral" shall mean any property of any kind constituting collateral
      ----------
for the Obligations under any of the Security Documents.

     "Commercial Letter of Credit" shall mean a documentary letter of credit
      ---------------------------
issued in respect of the purchase of goods or services by any Borrower or any
Restricted Subsidiary by the Issuing Bank in accordance with the terms of this
Agreement.

                                      -9-
<PAGE>

     "Commitments" shall mean, collectively, the Revolving Loan Commitments, the
      -----------
Term Loan A Commitments, the Term Loan B Commitments and, if applicable, the
Incremental Facility Commitments.

     "Commitment Ratio" shall mean the percentage in which a Lender is severally
      ----------------
bound to fund its portion of Advances to the Borrowers under the Commitments set
forth on Schedule 7 attached hereto (together with dollar amounts) (and which
         ----------
may change from time to time in accordance with Sections 2.15 and 11.5 hereof).

     "Communications Act" shall mean the Communications Act of 1934, and any
      ------------------
similar or successor federal statute, and the rules and regulations of the FCC
thereunder, all as the same may be in effect from time to time.

     "Communications Site" shall mean (a) any undeveloped real property and (b)
      -------------------
communication towers which have no bona fide customers on the date of
acquisition or construction thereof.

     "Continue", "Continuation" and "Continued" shall mean the continuation
      ---------   ------------       ---------
pursuant to Article 2 hereof of a LIBOR Advance as a LIBOR Advance from one
Interest Period to a different Interest Period.

     "Continuing Director" shall mean any member of the Board of Directors of
      -------------------
the Parent who (i) is a member of that Board of Directors on the Agreement Date
or (ii) was nominated for election by either (a) one or more of the Principal
Shareholders (or a Related Party thereof) or (b) the Board of Directors a
majority of whom were directors at the Agreement Date or whose election or
nomination for election was previously approved by one or more of the Principal
Shareholders or such directors.

     "Convert", "Conversion" and "Converted" shall mean a conversion pursuant to
      -------    ----------       ---------
Article 2 hereof of a LIBOR Advance into a Base Rate Advance or of a Base Rate
Advance into a LIBOR Advance, as applicable.

     "Convertible Notes" shall mean, collectively, (a) the $300,000,000.00 6.25%
      -----------------
Convertible Notes Due 2009 issued pursuant to that certain Indenture dated
October 4, 1999 of the Parent, with The Bank of New York as Trustee and (b) the
$425,500,000.00 2.25% Convertible Notes Due 2009 issued pursuant to that certain
Indenture dated October 4, 1999 of the Parent, with The Bank of New York as
Trustee.

     "Default" shall mean any Event of Default, and any of the events specified
      -------
in Section 8.1 hereof, regardless of whether there shall have occurred any
passage of time or giving of notice, or both, that would be necessary in order
to constitute such event an Event of Default.

     "Default Rate" shall mean a simple per annum interest rate equal to the sum
      ------------
of (a) the then applicable Interest Rate Basis (including the Applicable
Margin), and (b) two percent (2.0%).

                                     -10-
<PAGE>

     "Developing Towers" shall mean, as of any date, collectively, (a) any
      -----------------
communications tower constructed by any Borrower or any Restricted Subsidiary
during the twelve (12) calendar months immediately preceding the determination
date and having at least one broadband equivalent tenant reasonably acceptable
to the Administrative Agent under a contract having an original term of not less
than five (5) years, and (b) the Air Touch Towers, the AT&T Towers and any
communications tower acquired from Unisite, Triton or any other Person which has
owned such towers less than twelve (12) calendar months at the time of their
acquisition by any Borrower or any Restricted Subsidiary, in each case, which
was acquired during the twelve (12) calendar months immediately preceding the
determination date; provided, however, that notwithstanding the foregoing, the
                    --------  -------
Borrowers may designate at any time any communications tower that would
otherwise be a "Developing Tower" as a "mature tower" for all purposes under
this Agreement.

     "Developing Tower Operation Business" shall mean the operation by any
      -----------------------------------
Borrower or any Restricted Subsidiary of the Developing Towers.

     "Employee Pension Plan" shall mean any Plan which is maintained by any
      ---------------------
Borrower, any of their Subsidiaries or any ERISA Affiliate.

     "Environmental Laws" shall mean all applicable federal, state or local
      ------------------
laws, statutes, rules, regulations or ordinances, codes, common law, consent
agreements, orders, decrees, judgments or injunctions issued, promulgated,
approved or entered thereunder relating to public health, safety or the
pollution or protection of the environment, including, without limitation, those
relating to releases, discharges, emissions, spills, leaching, or disposals to
air, water, land or ground water, to the withdrawal or use of ground water, to
the use, handling or disposal of polychlorinated biphenyls, asbestos or urea
formaldehyde, to the treatment, storage, disposal or management of hazardous
substances (including, without limitation, petroleum, crude oil or any fraction
thereof, or other hydrocarbons), pollutants or contaminants, to exposure to
toxic, hazardous or other controlled, prohibited, or regulated substances,
including, without limitation, any such provisions under the Comprehensive
Environmental Response, Compensation and Liability Act of 1980, as amended (42
U.S.C. (S) 9601 et seq.), or the Resource Conservation and Recovery Act of 1976,
as amended (42 U.S.C. (S) 6901 et seq.).

     "ERISA" shall mean the Employee Retirement Income Security Act of 1974, as
      -----
in effect from time to time.

     "ERISA Affiliate" shall mean any Person, including a Subsidiary or an
      ---------------
Affiliate of any Borrower, that is a member of any group of organizations of
which any Borrower, as the case may be, is a member and which is covered by a
Plan.

     "Eurodollar Reserve Percentage" shall mean the percentage which is in
      -----------------------------
effect from time to time under Regulation D of the Board of Governors of the
Federal Reserve System, as such regulation may be amended from time to time, as
the maximum reserve requirement applicable with respect to Eurocurrency
Liabilities (as that term is defined in Regulation D), whether or not

                                     -11-
<PAGE>

any Lender has any such Eurocurrency Liabilities subject to such reserve
requirement at that time.

     "Event of Default" shall mean any of the events specified in Section 8.1
      ----------------
hereof; provided, however, that any requirement stated therein for notice or
        --------  -------
lapse of time, or both, has been satisfied.

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

     "Excess Cash Flow" shall mean, as of the end of any fiscal year of the
      ----------------
Borrowers based on the audited financial statements provided under Section 6.2
hereof for such fiscal year if available, the excess, if any, without
duplication, of (a) Operating Cash Flow for such fiscal year (exclusive of
amounts received in connection with loans to 116 Huntington and to TV Azteca),
minus (b) the sum of the following: (i) Capital Expenditures made (other than
-----
from the proceeds of the issuance of Capital Stock of the Borrowers, the
proceeds of the incurrence of Indebtedness or from the reinvestment of the Net
Proceeds of any sale, transfer or other disposition of assets of any Borrower or
any Restricted Subsidiary or any insurance or condemnation proceeding with
respect to such assets, to the extent permitted hereunder), by the Borrowers and
the Restricted Subsidiaries during such fiscal year; (ii) Scheduled Revolving
Loan Payments during such fiscal year; (iii) taxes paid in cash by the Borrowers
and their Restricted Subsidiaries during such fiscal year; (iv) Interest Expense
during such fiscal year; (v) scheduled principal payments made in respect of
Indebtedness for Money Borrowed (other than with respect to the Revolving Loans
and loans by any Borrower or any Restricted Subsidiary to any Borrower or any of
the Restricted Subsidiaries) paid by the Borrowers and the Restricted
Subsidiaries during such fiscal year; and (vi) Restricted Payments made to the
Parent (other than from Excess Cash Flow) during such fiscal year.

     "Facility Usage"  shall mean, as of the end of each calendar quarter, the
      --------------
percentage equivalent of a fraction, the numerator of which is equal to the sum
of the average daily amount during such quarter of (i) the Revolving Loans
outstanding, (ii) the Letters of Credit outstanding and (iii) the Term Loan A
Loans outstanding, and the denominator of which is equal to the sum of (1) the
average daily amount of the Revolving Loan Commitment during such quarter and
(2) the average daily amount of the Term Loan A Commitment during such quarter.

     "FCC" shall mean the Federal Communications Commission, or any other
      ---
similar or successor agency of the federal government administering the
Communications Act.

     "Federal Funds Rate" shall mean, as of any date, the weighted average of
      ------------------
the rates on overnight federal funds transactions with the members of the
Federal Reserve System arranged by federal funds brokers, as published for such
day (or, if such day is not a Business Day, for the next preceding Business Day)
by the Federal Reserve Bank of New York or, if such rate is not so published for
any day which is a Business Day, the average of the quotations for such day on
such transactions received by the Administrative Agent from three (3) federal
funds brokers of recognized standing selected by the Administrative Agent.

                                     -12-
<PAGE>

     "Fixed Charges" shall mean, as of any calculation date, for the twelve (12)
      -------------
calendar month period immediately preceding such date, for the Borrowers and the
Restricted Subsidiaries on a consolidated basis, the sum of (a) Interest Expense
for such period, (b) commitment and other fees incurred in connection with this
Agreement during such period, (c) all scheduled principal repayments with
respect to any Indebtedness for Money Borrowed (other than the Revolving Loans)
during such period, (d) all Scheduled Revolving Loan Payments made during such
period to the extent not included in Interest Expense, (e) taxes paid in cash
during such period, (f) Capital Expenditures made by the Borrowers and the
Restricted Subsidiaries (other than from the reinvestment of the Net Proceeds
of any asset sale and insurance or condemnation proceeding, to the extent
permitted hereunder) during such period and (g) Restricted Payments made to the
Parent (other than from Excess Cash Flow) during such period.

     "GAAP" shall mean, as in effect from time to time, generally accepted
      ----
accounting principles in the United States, consistently applied.

     "Granting Lender" shall have the meaning ascribed thereto in Section
      ---------------
11.5(j) hereof.

     "Guaranty" or "Guaranteed," as applied to an obligation, shall mean and
      --------      ----------
include (a) a guaranty, direct or indirect, in any manner, of all or any part of
such obligation, and (b) any agreement, direct or indirect, contingent or
otherwise, the practical effect of which is to assure in any way the payment or
performance (or payment of damages in the event of non-performance) of all or
any part of such obligation, including, without limiting the foregoing, any
reimbursement obligations as to amounts drawn down by beneficiaries of
outstanding letters of credit or capital call requirements; provided, however,
                                                            --------  -------
that the term "Guarantee" shall not include guarantees entered into in the
ordinary course of business, including, without limitation, the Developing Tower
Operation Business, not involving Indebtedness for Money Borrowed.

     "ICG" shall mean ICG Satellite Services, Inc., a Colorado corporation.
      ---

     "ICG Holdings" shall mean ICG Holdings, Inc., a Colorado corporation.
      ------------

     "Incremental Facility Commitment" shall mean the commitment of any Lender
      -------------------------------
or Lenders to make Advances to the Borrowers in accordance with Section 2.15
hereof (the Borrowers may obtain an Incremental Facility Commitment from more
than one Lender, each of which shall be several obligations of each such
Lender); and "Incremental Facility Commitments" shall mean the aggregate of the
              --------------------------------
Incremental Facility Commitments of each Lender.

     "Incremental Facility Loans" shall mean the amounts advanced by the Lenders
      --------------------------
holding an Incremental Facility Commitment to the Borrowers as Incremental
Facility Loans under the Incremental Facility Commitments, not to exceed the
amount of the Incremental Facility Commitments, and evidenced by the Incremental
Facility Notes.

                                     -13-
<PAGE>

     "Incremental Facility Maturity Date" shall mean the maturity date for the
      ----------------------------------
Incremental Facility Loans as set forth in the Notice of Incremental Facility
Commitment, which date shall not be earlier than six (6) months after the Term
Loan B Maturity Date.

     "Incremental Facility Notes" shall mean, collectively, those certain
      --------------------------
Incremental Facility Notes described in Section 2.15 hereof.

     "Indebtedness" shall mean, with respect to any Person, and without
      ------------
duplication, (a) all items, except items of shareholders' and partners' equity
or capital stock or surplus or general contingency or deferred tax reserves,
which in accordance with GAAP would be included in determining total liabilities
as shown on the liability side of a balance sheet of such Person, including,
without limitation, with respect to any secured non-recourse obligations of such
Person, the higher of the book value or fair market value of the property or
asset securing such obligation (if less than the amount of such obligation), (b)
all direct or indirect obligations of any other Person secured by any Lien to
which any property or asset owned by such Person is subject, but only to the
extent of the higher of the fair market value or the book value of the property
or asset subject to such Lien (if less than the amount of such obligation), if
the obligation secured thereby shall not have been assumed, (c) to the extent
not otherwise included, all Capitalized Lease Obligations of such Person and the
principal portion of all obligations of such Person with respect to leases
constituting part of a sale and lease-back arrangement, (d) all reimbursement
obligations with respect to outstanding letters of credit, (e) to the extent not
otherwise included, all obligations subject to Guaranties of such Person or its
Subsidiaries, and (f) all obligations of such Person under Interest Hedge
Agreements valued on a marked to market basis on the date of determination;
provided, however, that the Intracoastal Notes shall not be deemed to be, and
--------  -------
shall be excluded from, Indebtedness.

     "Indebtedness for Money Borrowed" shall mean, with respect to any Person,
      -------------------------------
Indebtedness for money borrowed and Indebtedness represented by notes payable
and drafts accepted representing extensions of credit, all obligations evidenced
by bonds, debentures, notes or other similar instruments, all Indebtedness upon
which interest charges are customarily paid (other than trade payables arising
in the ordinary course of business, but only if and so long as such accounts are
payable on customary trade terms), all Capitalized Lease Obligations, all
reimbursement obligations with respect to outstanding letters of credit, all
Indebtedness issued or assumed as full or partial payment for property or
services (other than trade payables arising in the ordinary course of business,
but only if and so long as such accounts are payable on customary trade terms),
whether or not any such notes, drafts, obligations or Indebtedness represent
Indebtedness for money borrowed, and, without duplication, Guaranties of any of
the foregoing; provided, however, that the Intracoastal Notes shall not be
               --------  -------
deemed to be, and shall be excluded from, Indebtedness for Money Borrowed.  For
purposes of this definition, interest which is accrued but not paid on the
scheduled due date for such interest shall be deemed Indebtedness for Money
Borrowed.

     "Indemnitee" shall have the meaning ascribed thereto in Section 5.11
      ----------
hereof.

                                     -14-
<PAGE>

     "Interest Expense" shall mean, for any period, all cash interest expense
      ----------------
(including imputed interest with respect to Capitalized Lease Obligations and
fees) with respect to any Indebtedness for Money Borrowed (including, without
limitation, the Obligations) of the Borrowers and the Restricted Subsidiaries on
a consolidated basis during such period pursuant to the terms of such
Indebtedness for Money Borrowed, all as calculated in accordance with GAAP.

     "Interest Hedge Agreements" shall mean the obligations of any Person
      -------------------------
pursuant to any arrangement with any other Person whereby, directly or
indirectly, such Person is entitled to receive from time to time periodic
payments calculated by applying either a floating or a fixed rate of interest on
a stated notional amount in exchange for periodic payments made by such Person
calculated by applying a fixed or a floating rate of interest on the same
notional amount and shall include, without limitation, interest rate swaps,
caps, floors, collars and similar agreements.

     "Interest Period" shall mean (a) in connection with any Base Rate Advance,
      ---------------
the period beginning on the date such Advance is made as or Converted to a Base
Rate Advance and ending on the last day of the calendar quarter in which such
Advance is made as or Converted to a Base Rate Advance; provided, however, that
                                                        --------  -------
if a Base Rate Advance is made or Converted on the last day of any calendar
quarter, it shall have an Interest Period ending on, and its Payment Date shall
be, the last day of the following calendar quarter, and (b) in connection with
any LIBOR Advance, the term of such Advance selected by the Borrowers or
otherwise determined in accordance with this Agreement.  Notwithstanding the
foregoing, however, (i) any applicable Interest Period which would otherwise end
on a day which is not a Business Day shall be extended to the next succeeding
Business Day unless, with respect to LIBOR Advances only, such Business Day
falls in another calendar month, in which case such Interest Period shall end on
the next preceding Business Day, (ii) any applicable Interest Period, with
respect to LIBOR Advances only, which begins on a day for which there is no
numerically corresponding day in the calendar month during which such Interest
Period is to end shall (subject to clause (i) above) end on the last day of such
calendar month, and (iii) the Borrowers shall not select an Interest Period
which extends beyond the Maturity Date or such earlier date as would interfere
with the Borrowers' repayment obligations under Section 2.5, 2.6 or 2.7 hereof.
Interest shall be due and payable with respect to any Advance as provided in
Section 2.3 hereof.

     "Interest Rate Basis" shall mean the Base Rate Basis or the LIBOR Basis, as
      -------------------
appropriate.

     "Interest Reserve" shall mean an escrow account on terms and conditions
      ----------------
satisfactory to the Majority Lenders of not less than $57,000,000.00, which will
be used to make payments on the Convertible Notes beginning with the April 15,
2000 payment and continuing through the October 15, 2001 payment.

     "Intracoastal Notes" shall mean, collectively, the partially non-recourse
      ------------------
notes of AT L.P. (true and correct copies of which have been delivered to the
Administrative Agent), in the aggregate principal amount of $12,000,000.00,
issued by AT L.P. in connection with the merger of Intracoastal Broadcasting,
Inc., a Delaware corporation, into AT Inc.

                                     -15-
<PAGE>

     "Investment" shall mean any investment or loan by any Borrower or any
      ----------
Restricted Subsidiary in or to any Person which Person, (a) after giving to such
investment or loan, is not consolidated with the Borrowers and the Restricted
Subsidiaries in accordance with GAAP, or (b) is designated as an Unrestricted
Subsidiary in accordance with the terms hereof.

     "Issuing Bank" shall mean The Toronto-Dominion Bank, New York Branch, as
      ------------
issuer of the Letters of Credit, and its successors and assigns hereunder.

     "Kline Steel" shall mean Kline Iron & Steel Company, Inc., a Delaware
      -----------
corporation.

     "Known to the Borrower", "to the Knowledge of the Borrower" or any similar
      ---------------------    --------------------------------
phrase, shall mean known by or reasonably should have been known by the
executive officers of any Borrower (which shall include, without limitation, the
chief executive officer, the chief operating officer, if any, the chief
financial officer, the general counsel and any vice president of any Borrower or
of ATC GP).

     "Lenders" shall mean the Persons whose names appear as "Lenders" on the
      -------
signature pages hereof and any other Person which becomes a "Lender" hereunder
after the Agreement Date; and "Lender" shall mean any one of the foregoing
                               ------
Lenders.

     "Letter of Credit Obligations" shall mean, at any time, the sum of (a) an
      ----------------------------
amount equal to the aggregate undrawn and unexpired amount (including the amount
to which any such Letter of Credit can be reinstated pursuant to the terms
hereof) of the then outstanding Letters of Credit and (b) an amount equal to the
aggregate drawn, but unreimbursed, drawings on any Letters of Credit.

     "Letter of Credit Reserve Account" shall mean any account maintained by the
      --------------------------------
Administrative Agent for the benefit of the Issuing Bank, the proceeds of which
shall be applied as provided in Section 8.2(g) hereof.

     "Letters of Credit" shall mean, collectively, each Standby Letter of Credit
      -----------------
or Commercial Letter of Credit issued by the Issuing Bank on behalf of any
Borrower or any Restricted Subsidiaries in accordance with the terms hereof.

     "Leverage Ratio" shall mean, as of any calculation date, the ratio of (a)
      --------------
Total Debt on such date to (b) Annualized Operating Cash Flow as of such date.

     "LIBOR" shall mean, for any Interest Period, the average of the interest
      -----
rates per annum at which deposits in United States Dollars for such Interest
Period are offered to the Administrative Agent in the Eurodollar market at
approximately 11:00 a.m. (London, England time) two (2) Business Days before the
first day of such Interest Period, in an amount approximately equal to the
principal amount of, and for a length of time approximately equal to the
Interest Period for, the LIBOR Advance sought by any Borrower.

                                     -16-
<PAGE>

     "LIBOR Advance" shall mean an Advance which the Borrowers request to be
      -------------
made as, Converted to or Continued as a LIBOR Advance in accordance with the
provisions of Section 2.2 hereof, and which shall be in a principal amount of at
least $5,000,000.00 and in an integral multiple of $1,000,000.00.

     "LIBOR Basis" shall mean a simple per annum interest rate (rounded upward,
      -----------
if necessary, to the nearest one-hundredth (1/100th) of one percent (1%)) equal
to the sum of (a) the quotient of (i) the LIBOR divided by (ii) one (1) minus
                                                ----------              -----
the Eurodollar Reserve Percentage, if any, stated as a decimal, plus (b) the
                                                                ----
Applicable Margin.  The LIBOR Basis shall apply to Interest Periods of one (1),
two (2), three (3), or six (6) months, and, once determined, shall remain
unchanged during the applicable Interest Period, except for changes to reflect
adjustments in the Eurodollar Reserve Percentage and the Applicable Margin as
adjusted pursuant to Section 2.3(f) hereof.  The LIBOR Basis for any LIBOR
Advance shall be adjusted as of the effective date of any change in the
Eurodollar Reserve Percentage.

     "Licenses" shall mean, collectively, any telephone, microwave, radio
      --------
transmissions, personal communications or other license, authorization,
certificate of compliance, franchise, approval or permit, whether for the
construction, the ownership or the operation of any communications tower
facilities, granted or issued by the FCC and held by any Borrower or any of the
Restricted Subsidiaries, all of which as of the Agreement Date are listed on
Schedule 1 attached hereto.
----------

     "Lien" shall mean, with respect to any property, any mortgage, lien,
      ----
pledge, negative pledge or other agreement not to pledge, assignment, charge,
security interest, title retention agreement, levy, execution, seizure,
attachment, garnishment or other encumbrance of any kind in respect of such
property, whether created by statute, contract, the common law or otherwise, and
whether or not choate, vested or perfected.

     "Loan Documents" shall mean, collectively, this Agreement, the Notes, the
      --------------
Security Documents, all fee letters, all Requests for Advance, all Requests for
Issuance of Letters of Credit, all Letters of Credit, all Notices of Incremental
Facility Commitments, all Interest Hedge Agreements between any Borrower, on the
one hand, and the Administrative Agent and any Person that is a Lender (or any
of their Affiliates) on the date such Interest Hedge Agreement was entered into,
or any of them, on the other hand, and all other certificates, documents,
instruments and agreements executed or delivered by any Borrower, any of the
Restricted Subsidiaries, the Parent, ATC Holding or ATC GP in connection with or
contemplated by this Agreement or any other Loan Document.

     "Loans" shall mean, collectively, the Revolving Loans, the Term Loan A
      -----
Loans, the Term Loan B Loans and, if applicable, the Incremental Facility Loans.

     "Loan-Purchase Agreement" shall mean any agreement or related agreements
      -----------------------
between any Borrower or any Restricted Subsidiary and any other Person pursuant
to the terms of which (a) any Borrower or such Restricted Subsidiary has made a
loan to such Person permitted by Section 7.6(d) hereof and (b) any Borrower or
such Restricted Subsidiary shall agree (whether by

                                     -17-
<PAGE>

merger, acquisition of assets or acquisition of capital stock) to acquire all or
substantially all of the assets of such Person within the twelve (12) calendar
month period immediately following the date of such agreement.

     "Majority Lenders" shall mean, collectively, Lenders the total of whose
      ----------------
Commitment Ratios equals or exceeds fifty-one percent (51%) of the Commitment
Ratios of all Lenders entitled to vote hereunder (without giving effect to any
Loans then outstanding).

     "Materially Adverse Effect" shall mean (a) any material adverse effect upon
      -------------------------
the business, assets, business prospects, liabilities, financial condition,
results of operations or properties of the Borrowers and the Restricted
Subsidiaries, taken as a whole, or (b) a material adverse effect upon the
binding nature, validity, or enforceability of this Agreement and the Notes, or
upon the ability of the Borrowers and the Restricted Subsidiaries to perform the
payment obligations or other material obligations under this Agreement or any
other Loan Document, or upon the value of the Collateral or upon the rights,
benefits or interests of the Lenders in and to the Loans or the rights of the
Administrative Agent and the Lenders in the Collateral; in either case, whether
resulting from any single act, omission, situation, status, event or
undertaking, or taken together with other such acts, omissions, situations,
statuses, events or undertakings.

     "Maturity Date" shall mean the Revolving Loan Maturity Date, the Term Loan
      -------------
A Maturity Date, the Term Loan B Maturity Date or the Incremental Facility
Maturity Date, as applicable.

     "Mature Tower Operation Business" shall mean the ownership, leasing and
      -------------------------------
tower management businesses of the Borrowers and their Restricted Subsidiaries
other than with respect to Developing Towers.

     "Moody's" shall mean Moody's Investor's Service, Inc. and its successors.
      -------

     "Multiemployer Plan" shall mean a multiemployer pension plan as defined in
      ------------------
Section 3(37) of ERISA to which any Borrower, any of its Subsidiaries or any
ERISA Affiliate is or has been required to contribute.

     "Necessary Authorizations" shall mean all approvals and licenses from, and
      ------------------------
all filings and registrations with, any governmental or other regulatory
authority, including, without limiting the foregoing, the Licenses and all
approvals, licenses, filings and registrations under the Communications Act,
necessary in order to enable the Borrowers and the Restricted Subsidiaries to
own, construct, maintain, and operate communications tower facilities and to
invest in other Persons who own, construct, maintain, manage and operate
communications tower facilities.

     "Net Proceeds" shall mean, with respect to any sale, lease, transfer or
      ------------
other disposition of assets by, or any insurance or condemnation proceedings
with respect to the assets of, any Borrower or any of the Restricted
Subsidiaries, the aggregate amount of cash received (including, without
limitation, any payments received for noncompetition covenants, consulting or
management fees in connection with such sale, and any portion of the amount
received

                                     -18-
<PAGE>

evidenced by a promissory note or other evidence of Indebtedness issued by the
purchaser), net of (i) amounts reserved, if any, for taxes payable with respect
to any such transaction or proceeding (after application (assuming application,
to the extent permitted by Applicable Law, first to such reserves) of any
available losses, credits or other offsets), (ii) reasonable and customary
transaction costs properly attributable to such transaction or proceeding and
payable by any Borrower or any of the Restricted Subsidiaries (other than to an
Affiliate) in connection with such transaction or proceeding, including, without
limitation, commissions, and (iii) until actually received by any Borrower or
any of the Restricted Subsidiaries, any portion of the amount (x) received and
held in escrow or (y) evidenced by a promissory note or other evidence of
Indebtedness issued by a purchaser or non-compete, consulting or management
agreement or covenant or (z) otherwise for which compensation is paid over time.
Upon receipt by any Borrower or any of the Restricted Subsidiaries of (A)
amounts referred to in item (iii) of the preceding sentence, or (B) if there
shall occur any reduction in the tax reserves referred to in item (i) of the
preceding sentence resulting in a payment to any Borrower or any of the
Restricted Subsidiaries, such amounts shall then be deemed to be "Net Proceeds."

     "Non-Excluded Taxes" shall have the meaning ascribed thereto in Section
      ------------------
10.3(a) hereof.

     "Non-U.S. Bank" shall have the meaning ascribed thereto in Section 2.8(a)
      -------------
hereof.

     "Notes" shall mean, collectively, the Revolving Loan Notes, the Term Loan A
      -----
Notes, the Term Loan B Notes and, if applicable, the Incremental Facility Notes.

     "Notice of Incremental Facility Commitment" shall mean any notice by the
      -----------------------------------------
Borrowers of the Incremental Facility Commitments, which notice shall be in the
form of Exhibit F attached hereto and shall be delivered to the Administrative
        ---------
Agent and the Lenders.

     "Obligations" shall mean all payment and performance obligations of every
      -----------
kind, nature and description of the Borrowers, the Restricted Subsidiaries, and
any other obligors to the Lenders (and with respect to Interest Hedge Agreements
which are Loan Documents, the counter-party to such Interest Hedge Agreement),
the Issuing Bank or the Administrative Agent, or any of them, under this
Agreement and the other Loan Documents (including, without limitation, any
interest, fees and other charges on the Loans or otherwise under the Loan
Documents that would accrue but for the filing of a bankruptcy action with
respect to any Borrower, whether or not such claim is allowed in such bankruptcy
action, Obligations to the Lenders pursuant to Section 5.12 hereof and the
Letter of Credit Obligations), as they may be amended from time to time, or as a
result of making the Loans, whether such obligations are direct or indirect,
absolute or contingent, due or not due, contractual or tortious, liquidated or
unliquidated, arising by operation of law or otherwise, now existing or
hereafter arising.

     "Operating Cash Flow" shall mean, for any fiscal year, (a) the sum of (i)
      -------------------
Operating Cash Flow (Developing Towers), (ii) Operating Cash Flow (Mature
Towers) and (iii) Operating Cash Flow (Other Business) for such year, minus (b)
                                                                      -----
corporate overhead (exclusive of amortization and depreciation) of the Borrowers
and the Restricted Subsidiaries (on a consolidated basis) for the four fiscal
quarters ending on the calculation date.

                                     -19-
<PAGE>

     "Operating Cash Flow (Developing Towers)" shall mean, with respect to the
      ---------------------------------------
Borrowers and the Restricted Subsidiaries on a consolidated basis as of the end
of any period, (a) the sum of (i) operating revenues of the Borrowers and the
Restricted Subsidiaries in connection with the Developing Tower Operation
Business plus (ii) Unrestricted Subsidiary Distributions with respect to
         ----
businesses of such Persons of the same type as the Developing Tower Operation
Business during such period, minus (b) operating expenses attributable to such
                             -----
Developing Tower Operation Business for such period.  In the case of determining
Operating Cash Flow (Developing Towers) under Sections 2.3, 7.8, 7.9, 7.10 and
7.11 hereof following an Acquisition of a Developing Tower Operation Business
permitted hereunder, Operating Cash Flow (Developing Towers) shall include the
Acquisition Operating Cash Flow.  For purposes of calculating Operating Cash
Flow (Developing Towers) in connection with any Advance for an Acquisition of a
Developing Tower Operation Business, Operating Cash Flow (Developing Towers) for
the Borrowers and the Restricted Subsidiaries as of the last day of the
immediately preceding calendar month end shall include "operating cash flow
(developing towers)" for the Acquisition for the same period after giving effect
to adjustments reasonably satisfactory to the Administrative Agent.  For
purposes of this definition, Operating Cash Flow (Developing Towers) shall
include the foregoing items (each calculated in a manner substantially similar
to the financial statements required to be delivered pursuant to Sections 6.1
and 6.2 hereof and otherwise in all respects reasonably satisfactory to the
Administrative Agent) with respect to any Person with whom any Borrower or any
Restricted Subsidiary has entered into a Loan-Purchase Agreement; provided,
                                                                  --------
however, that with respect to any such Person such items shall not be included
-------
for any period exceeding twelve (12) calendar months unless such Person becomes
a Restricted Subsidiary of such Borrower; and provided further, however, that
                                              -------- -------  -------
Operating Cash Flow with respect to any such Persons for any fiscal year shall
not exceed $3,000,000.00 in the aggregate.

     "Operating Cash Flow (Mature Towers)" shall mean, with respect to the
      -----------------------------------
Borrowers and their Restricted Subsidiaries on a consolidated basis as of the
end of any period, (a) the sum of (i) operating revenues of the Borrowers and
the Restricted Subsidiaries in connection with the Mature Tower Operation
Business plus (ii) Unrestricted Subsidiary Distributions with respect to the
         ----
businesses of such Persons of the same type as Mature Tower Operation Business
during such period, minus (b) operating expenses attributable to such Mature
                    -----
Tower Operation Business for such period.  In the case of determining Operating
Cash Flow (Mature Towers) under Sections 2.3, 7.8, 7.9, 7.10 and 7.11 hereof
following an Acquisition of a Mature Tower Operation Business permitted
hereunder, Operating Cash Flow  (Mature Towers) shall include the Acquisition
Operating Cash Flow.  For purposes of calculating Operating Cash Flow (Mature
Towers) in connection with any Advance for an Acquisition of a Mature Tower
Operation Business, Operating Cash Flow (Mature Towers) as of the last day of
the immediately preceding calendar month end shall include "operating cash flow
(mature towers)" for the Acquisition for the same period after giving effect to
adjustments reasonably satisfactory to the Administrative Agent. For purposes of
this definition, Operating Cash Flow (Mature Towers) shall include the foregoing
items (each calculated in a manner substantially similar to the financial
statements required to be delivered pursuant to Sections 6.1 and 6.2 hereof and
otherwise in all respects reasonably satisfactory to the Administrative Agent)
with respect to any Person with whom any

                                     -20-
<PAGE>

Borrower or any Restricted Subsidiary has entered into a Loan-Purchase
Agreement; provided, however, that with respect to any such Person such items
           --------  -------
shall not be included for any period exceeding twelve (12) calendar months
unless such Person becomes a Restricted Subsidiary of such Borrower; and
provided further, however, that Operating Cash Flow with respect to any such
-------- -------  -------
Persons for any fiscal year shall not exceed $3,000,000.00 in the aggregate.

     "Operating Cash Flow (Other Business)" shall mean, with respect to the
      ------------------------------------
Borrowers and their Restricted Subsidiaries on a consolidated basis as of the
end of any period, (a) the sum of (i) operating revenues of the Borrowers and
the Restricted Subsidiaries in connection with the Other Business plus (ii)
                                                                  ----
Unrestricted Subsidiary Distributions with respect to businesses of such Persons
of the same type as the Other Business during such period, minus (b) operating
                                                           -----
expenses attributable to such Other Business for such period.  In the case of
determining Operating Cash Flow (Other Business) under Sections 2.3, 7.8, 7.9,
7.10 and 7.11 hereof following an Acquisition of Other Business permitted
hereunder, Operating Cash Flow (Other Business) shall include the Acquisition
Operating Cash Flow.  For purposes of calculating Operating Cash Flow (Other
Business) in connection with any Advance for an Acquisition of Other Business,
Operating Cash Flow (Other  Business) as of the last day of the immediately
preceding calendar month end shall include "operating cash flow (other
business)" for the Acquisition for the same period after giving effect to
adjustments reasonably satisfactory to the Administrative Agent.  For purposes
of this definition, Operating Cash Flow (Other Business) shall include the
foregoing items (each calculated in a manner substantially similar to the
financial statements required to be delivered pursuant to Sections 6.1 and 6.2
hereof and otherwise in all respects satisfactory to the Administrative Agent)
with respect to any Person with whom any Borrower and/or any Restricted
Subsidiary has entered into a Loan-Purchase Agreement; provided, however, that
                                                       --------  -------
with respect to any such Person such items shall not be included for any period
exceeding twelve (12) calendar months unless such Person becomes a Restricted
Subsidiary of such Borrower; and provided further, however, that Operating Cash
                                 -------- -------  -------
Flow with respect to any such Persons for any fiscal year shall not exceed
$3,000,000.00 in the aggregate.

     "Other Business" shall mean all businesses of the Borrowers and their
      --------------
Restricted Subsidiaries (other than the Mature Tower Business Operations and the
Developing Tower Operations Business), including, without limitation, the
Teleport Business, the video, voice and data transmission business, the site
acquisition business and interest income received in respect of Investments
permitted hereunder.

     "Parent" shall mean American Tower Corporation, a Delaware corporation.
      ------

     "Parent Guaranty" shall mean that certain Amended and Restated Parent
      ---------------
Guaranty dated as of even date herewith made by the Parent for the ratable
benefit of the Administrative Agent, the Lenders and the Issuing Bank,
substantially in the form of Exhibit G attached hereto.
                             ---------

     "Parent Pledge Agreement" shall mean that certain Amended and Restated
      -----------------------
Parent Pledge Agreement dated as of even date herewith by the Parent in favor of
the Administrative Agent, for itself and on behalf of the Lenders and the
Issuing Bank substantially in the form of Exhibit H attached hereto.
                                          ---------

                                     -21-
<PAGE>

     "Payment Date" shall mean the last day of any Interest Period.
      ------------

     "PBGC" shall mean the Pension Benefit Guaranty Corporation, or any
      ----
successor thereto.

     "Permitted Liens" shall mean, collectively, as applied to any Person:
      ---------------

          (a) any Lien in favor of the Administrative Agent, the Lenders and the
Issuing Bank given to secure the Obligations;

          (b) (i) Liens on real estate or other property for taxes, assessments,
governmental charges or levies not yet delinquent and (ii) Liens for taxes,
assessments, judgments, governmental charges or levies or claims the non-payment
of which is being diligently contested in good faith by appropriate proceedings
and for which adequate reserves have been set aside on such Person's books, but
only so long as no foreclosure, distraint, sale or similar proceedings have been
commenced with respect thereto;

          (c) Liens of carriers, warehousemen, mechanics, vendors (solely to the
extent arising by operation of law), laborers and materialmen incurred in the
ordinary course of business for sums not yet due or being diligently contested
in good faith, if reserves or appropriate provisions shall have been made
therefor;

          (d) Liens incurred in the ordinary course of business in connection
with worker's compensation and unemployment insurance, social security
obligations, assessments or government charges which are not overdue for more
than sixty (60) days;

          (e) restrictions on the transfer of the Licenses or assets of any
Borrower or  any of the Restricted Subsidiaries imposed by any of the Licenses
as presently in effect or by the Communications Act and any regulations
thereunder;

          (f) easements, rights-of-way, zoning restrictions, licenses,
reservations or restrictions on use and other similar encumbrances on the use of
real property which do not materially interfere with the ordinary conduct of the
business of such Person or the use of such property;

          (g) Liens arising by operation of law in favor of purchasers in
connection with any asset sale permitted hereunder; provided, however, that such
                                                    --------  -------
Lien only encumbers the property being sold;

          (h) Liens reflected by Uniform Commercial Code financing statements
filed in respect of Capitalized Lease Obligations permitted pursuant to Section
7.1 hereof and true leases of any Borrower or any of the Restricted
Subsidiaries;

          (i) Liens to secure performance of statutory obligations, surety or
appeal bonds, performance bonds, bids or tenders;

                                     -22-
<PAGE>

          (j) judgment Liens which do not result in an Event of Default under
Section 8.1(h) hereof;

          (k) Liens in connection with escrow deposits made in connection with
Acquisitions permitted hereunder; and

          (l) Liens of a nature contemplated by the penultimate sentence of
Section 5.13 hereof.

     "Person" shall mean an individual, corporation, limited liability company,
      ------
association, partnership, joint venture, trust or estate, an unincorporated
organization, a government or any agency or political subdivision thereof, or
any other entity.

     "Plan" shall mean an employee benefit plan within the meaning of Section
      ----
3(3) of ERISA or any other employee benefit plan maintained for employees of any
Person or any affiliate of such Person.

     "Principal Shareholders" shall mean, collectively, (a) Steven B. Dodge, (b)
      ----------------------
the legal heirs of Steven B. Dodge, (c) Thomas H. Stoner, (d) the legal heirs of
Thomas H. Stoner, (e) Hicks, Muse, Tate & Furst Incorporated, (f) Cox Telecom
Towers, Inc., (g) Clear Channel Communications, Inc. and (h) any Person the
securities of which would be deemed to be beneficially owned by any of the
foregoing Persons pursuant to the provisions of Rule 13(d)(3) under the Exchange
Act.

     "Prior Loan Agreement" shall mean that certain ATS Facility A Agreement
      --------------------
dated as of June 16, 1998 by and among American Tower Systems (Delaware), Inc.,
a Delaware corporation, and American Tower Systems, L.P., a Delaware limited
partnership, as Borrowers, the financial institutions parties thereto, as
Lenders, and Toronto Dominion (Texas), Inc., as Administrative Agent, as
heretofore amended, modified, restated and supplemented.

     "Pro Forma Debt Service" shall mean with respect to the twelve (12)
      ----------------------
calendar month period following the calculation date, and after giving effect to
any Interest Hedge Agreements and LIBOR Advances, the sum of the amount of all
of the following with respect to the Borrowers and the Restricted Subsidiaries,
on a consolidated basis: (a) scheduled payments of principal on Indebtedness
for Money Borrowed (determined, with respect to the Revolving Loans only, as the
difference between the outstanding principal amount of the Revolving Loans and
Letter of Credit Obligations on the calculation date and the amount the
Revolving Loan Commitments will be on the last day of such period) for such
period; (b) Interest Expense for such period; (c) fees payable under this
Agreement for such period; (d) other payments payable by such Persons during
such period in respect of Indebtedness for Money Borrowed (other than voluntary
repayments); and (e) after the Interest Reserve has been applied in full
pursuant to the terms hereof, all Restricted Payments to be made by the
Borrowers to the Parent which will be necessary to make interest payments on the
Convertible Notes during such period.  For purposes of this definition, where
interest payments for the twelve (12) month period immediately

                                     -23-
<PAGE>

succeeding the calculation date are not fixed by way of Interest Hedge
Agreements, LIBOR Advances, or otherwise for the entire period, interest shall
be calculated on such Indebtedness for Money Borrowed for periods for which
interest payments are not so fixed at the lesser of (i) the LIBOR Basis (based
on the then current adjustment under Section 2.3(f) hereof) for a LIBOR Advance
having an Interest Period of six (6) months as determined on the date of
calculation and (ii) the Base Rate Basis as in effect on the date of
calculation; provided, however, that if such LIBOR Basis cannot be determined in
             --------  -------
the reasonable opinion of the Administrative Agent, such interest shall be
calculated using the Base Rate Basis as then in effect.

     "Projections" shall have the meaning ascribed thereto in Section 4.1(r)
      -----------
hereof.

     "Register" shall have the meaning ascribed to such term in Section 11.5(g)
      --------
hereof.

     "Registered Noteholder" shall mean each Non-U.S. Bank that requests or
      ---------------------
holds a Registered Note pursuant to Section 2.8(a) hereof or registers its Loans
pursuant to Section 11.5(g) hereof.

     "Registered Notes" shall mean, collectively, those certain Notes that have
      ----------------
been issued in registered form in accordance with Sections 2.8(a) and 11.5(g)
hereof and each of which bears the following legend: "This is a Registered Note,
and this Registered Note and the Loans evidenced hereby may be assigned or
otherwise transferred in whole or in part only by registration of such
assignment or transfer on the Register and in compliance with all other
requirements provided for in the Loan Agreement."

     "Regulations" shall have the meaning ascribed thereto in Section 4.1(n)
      -----------
hereof.

     "Related Party" shall mean with respect to any individual (i) any immediate
      -------------
family member of such individual or (ii) any Person, the beneficiaries,
stockholders, partners, owners or Persons beneficially holding an eighty percent
(80%) or more controlling interest of which consist of such individual or an
immediate family member of such individual.

     "Reportable Event" shall mean, with respect to any Employee Pension Plan,
      ----------------
an event described in Section 4043(b) of ERISA.

     "Request for Advance" shall mean a certificate designated as a "Request for
      -------------------
Advance," signed by an Authorized Signatory of any Borrower requesting an
Advance, Continuation or Conversion hereunder, which shall be in substantially
the form of Exhibit I attached hereto, and shall, among other things, (i)
            ---------
specify the date of the requested Advance, Continuation or Conversion (which
shall be a Business Day), the amount of the Advance, the type of Advance (LIBOR
or Base Rate), and, with respect to LIBOR Advances, the Interest Period with
respect thereto, (ii) state that there shall not exist, on the date of the
requested Advance, Continuation or Conversion and after giving effect thereto, a
Default, (iii) specify the Applicable Margin then in effect and (iv) designate
the amount of the Revolving Loan Commitments, Term Loan A Commitments, Term Loan
B Commitments and, if applicable, Incremental Facility Commitments being drawn,
Continued or Converted.

                                     -24-
<PAGE>

     "Request for Issuance of Letter of Credit" shall mean any certificate
      ----------------------------------------
signed by an Authorized Signatory of any Borrower requesting that the Issuing
Bank issue a Letter of Credit hereunder, which certificate shall be in
substantially the form of Exhibit J attached hereto and shall, among other
                          ---------
things, specify (a) that the requested Letter of Credit is either a Commercial
Letter of Credit or a Standby Letter of Credit, (b) the stated amount of the
Letter of Credit, (c) the effective date for the issuance of the Letter of
Credit (which shall be a Business Day), (d) the date on which the Letter of
Credit is to expire (which shall be a Business Day), (e) the Person for whose
benefit such Letter of Credit is to be issued and (f) other relevant terms of
such Letter of Credit.

     "Restricted Payment" shall mean any direct or indirect distribution,
      ------------------
dividend or other payment to any Person (other than to any Borrower or any of
the Restricted Subsidiaries) on account of (a) any general or limited
partnership interest in, or shares of Capital Stock or other equity securities
of, any Borrower or any Restricted Subsidiary (other than dividends payable
solely in general or limited partnership interests or stock of such Person or in
warrants or other rights or options to acquire such partnership interests or
stock and stock splits), including, without limitation, any direct or indirect
distribution, dividend or other payment to any Person (other than to any
Borrower or any of the Restricted Subsidiaries) on account of any warrants or
other rights or options to acquire shares of Capital Stock of any Borrower or
any of the Restricted Subsidiaries, or (b) any management or similar agreement
with an Affiliate of such Person not (i) in compliance with Section 7.12 hereof
or (ii) in the ordinary course of business.

     "Restricted Subsidiary" shall mean any Subsidiary of any Borrower other
      ---------------------
than an Unrestricted Subsidiary.  The Restricted Subsidiaries as of the
Agreement Date are as set forth on Schedule 2 attached hereto.
                                   ----------

     "Revolving Loan Commitments" shall mean the several obligations of the
      --------------------------
Lenders having a Revolving Loan Commitment to advance to the Borrowers an
aggregate amount of up to $650,000,000.00 at any one time outstanding, in
accordance with their respective Commitment Ratios for Revolving Loans, to the
Borrowers and as such obligations may be reduced from time to time, in each
case, pursuant to the terms hereof; and "Revolving Loan Commitment" shall mean
                                         -------------------------
the individual commitment of each such Lender to advance Revolving Loans
hereunder.

     "Revolving Loan Maturity Date" shall mean June 30, 2007, or such earlier
      ----------------------------
date as payment of the Revolving Loans shall be due (whether by acceleration,
reduction of the Revolving Loan Commitments to zero or otherwise).

     "Revolving Loan Notes" shall mean, collectively, those certain revolving
      --------------------
promissory notes in an aggregate original principal amount of the Revolving Loan
Commitments, one (1) issued by the Borrowers to each of the Lenders having a
Revolving Loan Commitment, each one substantially in the form of Exhibit K
                                                                 ---------
attached hereto, and any extensions, renewals or amendments to, or replacements
of, the foregoing.

                                     -25-
<PAGE>

     "Revolving Loans" shall mean, collectively, the amounts advanced by the
      ---------------
Lenders having Revolving Loan Commitments to the Borrowers under the Revolving
Loan Commitments, and evidenced by the Revolving Loan Notes.

     "Scheduled Revolving Loan Payments" shall mean, collectively, for any
      ---------------------------------
period, with respect to the Revolving Loans, (a) the highest principal amount of
the Revolving Loans outstanding during such period minus (b) the Revolving Loan
                                                   -----
Commitments on the last day of such period.

     "Sconnix Note" shall mean the note of Sconnix Broadcasting Company, a New
      ------------
Hampshire limited partnership (a true and correct copy of which has been
delivered to the Administrative Agent), in the aggregate principal amount of
$12,000,000.00, acquired by AT Inc. in connection with the merger of
Intracoastal Broadcasting, Inc., a Delaware corporation, into AT Inc.

     "Security Agreement" shall mean that certain Amended and Restated Security
      ------------------
Agreement dated as of even date herewith, made by the Borrowers in favor of the
Administrative Agent, for itself and on behalf of the Lenders and the Issuing
Bank, substantially in the form of Exhibit L attached hereto.
                                   ---------

     "Security Documents" shall mean, collectively, the Borrower Guaranties,
      ------------------
each Security Agreement, the Stock Pledge Agreement, all Subsidiary Guaranties,
all Subsidiary Pledge Agreements, all Subsidiary Security Agreements, all
Assignments of Intercompany Notes, all Subordination Agreements, each Assignment
of General Partner Interests, each Assignment of Limited Partner Interests, the
Parent Pledge Agreement, the Parent Guaranty, the ATC GP Guaranty,  the ATC GP
Security Agreement, the ATC Holding Guaranty, the ATC Holding Security
Agreement, any other agreement, document or instrument providing collateral for
the Obligations whether now or hereafter in existence, and any filings,
instruments, agreements, and documents related thereto or to this Agreement, and
providing the Administrative Agent, the Lenders and the Issuing Bank, with
Collateral for the Obligations.

     "Security Interest" shall mean all Liens in favor of the Administrative
      -----------------
Agent, the Lenders and the Issuing Bank, created hereunder or under any of the
Security Documents to secure the Obligations.

     "SPC" shall have the meaning ascribed thereto in Section 11.5(j) hereof.
      ---

     "Special Purpose Subsidiaries" shall mean any and all wholly-owned
      ----------------------------
Restricted Subsidiaries of the Borrowers formed to hold communications towers,
including tower sites acquired and towers acquired or constructed by the
Borrowers and the Restricted Subsidiaries pursuant to Section 5.16 hereof.

     "Standard and Poor's" shall mean Standard and Poor's Ratings Services, a
      -------------------
division of The McGraw-Hill Companies, Inc., and its successors.

                                     -26-
<PAGE>

     "Standby Letter of Credit" shall mean a letter of credit issued by the
      ------------------------
Issuing Bank in accordance with the terms hereof to support obligations of any
Borrower or any of the Restricted Subsidiaries incurred in the ordinary course
of business, and which is not a Commercial Letter of Credit.

     "Stock Pledge Agreement" shall mean that certain Amended and Restated Stock
      ----------------------
Pledge Agreement of AT Inc. dated the Agreement Date between AT Inc. and the
Administrative Agent, substantially in the form of Exhibit M attached hereto,
                                                   ---------
pursuant to which AT Inc. has pledged to the Administrative Agent, for itself
and on behalf of the Lenders and the Issuing Bank, all of its stock ownership in
each of its directly owned Restricted Subsidiaries.

     "Subordination Agreements" shall mean, collectively, (a) that certain
      ------------------------
Subordination Agreement among ATC Operating, ATC LP and the Administrative Agent
and (b) that certain Subordination Agreement among ATC Holding, ATC GP and the
Administrative Agent, in each case dated the Agreement Date and substantially in
the form of Exhibit N attached hereto.
            ---------

     "Subsidiary" shall mean, as applied to any Person, (a) any corporation of
      ----------
which no less than fifty percent (50%) of the outstanding stock (other than
directors' qualifying shares) having ordinary voting power to elect a majority
of its board of directors, regardless of the existence at the time of a right of
the holders of any class or classes of securities of such corporation to
exercise such voting power by reason of the happening of any contingency, or any
partnership or limited liability company of which no less than fifty percent
(50%) of the outstanding partnership or limited liability company interests, is
at the time owned directly or indirectly by such Person, or by one or more
Subsidiaries of such Person, or by such Person and one or more Subsidiaries of
such Person; provided, however, that if such Person and/or such Person's
             --------  -------
Subsidiaries directly or indirectly own no more than fifty percent (50%) of such
Subsidiary's ownership interests, then such Subsidiary's operating or governing
documents must require (i) such Subsidiary's net cash after the establishment of
reserves be distributed to its equity holders no less frequently than quarterly
and (ii) the consent of such Person and/or such Person's Subsidiaries to amend
or otherwise modify the provisions of such operating or governing documents
requiring such distributions, or (b) any other entity which is directly or
indirectly controlled or capable of being controlled by such Person, or by one
or more Subsidiaries of such Person, or by such Person and one or more
Subsidiaries of such Person.

     "Subsidiary Guaranty" shall mean that certain Amended and Restated
      -------------------
Subsidiary Guaranty dated the Agreement Date in favor of the Administrative
Agent, the Lenders and the Issuing Bank, given by each Restricted Subsidiary,
each substantially in the form of Exhibit O attached hereto, and shall include
                                  ---------
any similar agreements executed pursuant to Section 5.13 hereof.

     "Subsidiary Pledge Agreement" shall mean that certain Amended and Restated
      ---------------------------
Subsidiary Pledge Agreement dated the Agreement Date made by each Restricted
Subsidiary having one or more of its own Restricted Subsidiaries, on the one
hand, in favor of the Administrative Agent, for itself and on behalf of the
Lenders and the Issuing Bank, on the other

                                     -27-
<PAGE>

hand, each substantially in the form of Exhibit P attached hereto, and shall
                                        ---------
include any similar agreements executed pursuant to Section 5.13 hereof.

     "Subsidiary Security Agreement" shall mean that certain Amended and
      -----------------------------
Restated Subsidiary Security Agreement dated the Agreement Date made by each
Restricted Subsidiary, on the one hand, in favor of the Administrative Agent,
for itself and on behalf of the Lenders and the Issuing Bank, on the other hand,
each substantially in the form of Exhibit Q attached hereto, and shall include
                                  ---------
any similar agreements executed pursuant to Section 5.13 hereof.

     "Teleport Business" shall mean the business of owning, operating and
      -----------------
managing satellite up-link facilities.

     "Term Loan A Commitments" shall mean the several obligations of the Lenders
      -----------------------
having a Term Loan A Commitment to advance to the Borrowers an aggregate amount
of up to $850,000,000.00 at any one time outstanding, in accordance with their
respective Commitment Ratios for Term Loan A Loans and as such obligations may
be reduced from time to time, in each case, pursuant to the terms hereof; and
"Term Loan A Commitment" shall mean the individual commitment of each such
 ----------------------
Lender to advance Term Loan A Loans hereunder.

     "Term Loan A Loans" shall mean, collectively, the aggregate amounts
      -----------------
advanced by the Lenders having Term Loan A Commitments to the Borrowers as Term
Loan A Loans under the Term Loan A Commitments and evidenced by the Term Loan A
Notes.

     "Term Loan A Maturity Date" shall mean June 30, 2007, or such earlier date
      -------------------------
as the payment of the Term Loan A Loans shall be due (whether by acceleration,
reduction of the Term Loan A Commitments to zero or otherwise).

     "Term Loan A Notes" shall mean, collectively, those certain term promissory
      -----------------
notes in the aggregate original principal amount of the Term Loan A Commitments,
one (1) issued by the Borrowers to each of the Lenders having a Term Loan A
Commitment, each one substantially in the form of Exhibit R attached hereto, and
                                                  ---------
any extensions, modifications, renewals or replacements of, or amendments to,
any of the foregoing.

     "Term Loan B Commitments" shall mean the several obligations of the Lenders
      -----------------------
having a Term Loan B Commitment to advance to the Borrowers on aggregate amount
of up to $500,000,000.00 at any one time outstanding, in accordance with their
respective Commitment Ratios for Term Loan B Loans pursuant to the terms hereof;
and "Term Loan B Commitment" shall mean the individual commitment of each such
     ----------------------
Lender to advance Term Loan B Loans hereunder

     "Term Loan B Loans" shall mean, collectively, the aggregate amounts
      -----------------
advanced by the Lenders having Term Loan B Commitments to the Borrowers as Term
Loan B Loans under the Term Loan B Commitments and evidenced by the Term Loan B
Notes.

                                     -28-
<PAGE>

     "Term Loan B Maturity Date" shall mean December 31, 2007, or such earlier
      -------------------------
date as the payment of the Term Loan B Loans shall be due (whether by
acceleration, or otherwise).

     "Term Loan B Notes" shall mean, collectively, those certain term promissory
      -----------------
notes in the aggregate original principal amount of the Term Loan B Commitments,
one (1) issued by the Borrowers to each of the Lenders having a Term Loan B
Commitment, each one substantially in the form of Exhibit S attached hereto, and
                                                  ---------
any extension, modifications, renewals or replacements of, or amendments to, any
of the foregoing.

     "Total Debt" shall mean, for the Borrowers and the Restricted Subsidiaries
      ----------
on a consolidated basis as of any date, the sum (without duplication) of (i) the
outstanding principal amount of the Loans, (ii) the aggregate amount of
Capitalized Lease Obligations and Indebtedness for Money Borrowed of such
Persons, and (iii) the aggregate amount of all Guaranties by such Persons of
Indebtedness for Money Borrowed.

     "Triton" shall mean Triton PCS, Inc., a Delaware corporation, and its
      ------
Affiliates.

     "TV Azteca" shall mean TV Azteca, S.A. de C.V., a sociedad anonima de
      ---------
capital variable organized under the laws of the United Mexican States.

     "Unisite" shall mean UNIsite, Inc., a Delaware corporation.
      -------

     "Unisite Notes" shall mean, collectively, those certain 13% Subordinated
      -------------
Accrual Notes due December 15, 2004 of Unisite, issued pursuant to the Note and
Warrant Purchase Agreement dated December 18, 1997.

     "Unreinvested Net Proceeds" shall mean the aggregate Net Proceeds with
      -------------------------
respect to which (a) any Borrower has notified the Administrative Agent in
writing that the Borrowers intend to use any or all of such Net Proceeds to
acquire fixed or capital assets permitted by Section 7.6 hereof or for the
construction of new towers within twelve (12) months of the date of receipt of
such Net Proceeds and (b) any Borrower uses or irrevocably commits to be used
within such twelve (12) month period; provided, however, that once applied to
                                      --------  -------
reduce the Commitments or repay Loans hereunder, such Unreinvested Net Proceeds
shall cease to be Unreinvested Net Proceeds.

     "Unrestricted Subsidiary" shall mean any Subsidiary of any Borrower or any
      -----------------------
joint venture (which may represent a minority interest) between any Borrower
and/or any of their Subsidiaries and any other Person, in each case, which any
Borrower has heretofore designated or hereafter designates as an Unrestricted
Subsidiary by written notice to the Administrative Agent and the Lenders prior
to the formation or acquisition of such Subsidiary or joint venture.
Notwithstanding the foregoing, no Restricted Subsidiary may be re-designated as
an Unrestricted Subsidiary without the prior consent of the Majority Lenders and
no Special Purpose Subsidiary, nor either of ATC LP or ATC Operating, may be
designated as an Unrestricted Subsidiary without the consent of all of the
Lenders.  The Unrestricted Subsidiaries as of the Agreement

                                     -29-
<PAGE>

Date are as set forth Schedule 2 attached hereto. All Subsidiaries of any
                      ----------
Unrestricted Subsidiary, now or hereafter existing, shall be Unrestricted
Subsidiaries.

     "Unrestricted Subsidiary Distributions" shall mean, collectively, the
      -------------------------------------
aggregate amount of cash distributions received during such period by any
Borrower or any of the Restricted Subsidiaries from any Unrestricted Subsidiary
(other than in connection with the repayment of intercompany Indebtedness
permitted hereunder).

     "U.S. Person" shall mean a citizen or resident of the United States of
      -----------
America, a corporation, partnership or other entity created or organized in or
under any laws of the United States of America, or any estate or trust that is
subject to Federal income taxation regardless of the source of its income.

     Each definition of an agreement in this Article 1 shall include such
agreement as modified, amended or supplemented from time to time in accordance
herewith.

     Section 1.2  Interpretation.  Except where otherwise specifically
                  --------------
restricted, reference to a party to this Agreement or any other Loan Document
includes that party and its successors and assigns.  All capitalized terms used
herein which are defined in Article 9 of the Uniform Commercial Code in effect
in the State of New York on the date hereof and which are not otherwise defined
herein shall have the same meanings herein as set forth therein.  Whenever any
agreement, promissory note or other instrument or document is defined in this
Agreement, such definition shall be deemed to mean and include, from and after
the date of any amendment, restatement, supplement, confirmation or modification
thereof, such agreement, promissory note or other instrument or document as so
amended, restated, supplemented, confirmed or modified.  All terms defined in
this Agreement in the singular shall have comparable meanings when used in the
plural and vice versa.  The words "hereof," "herein" and "hereunder" and words
of similar import when used in this Agreement shall refer to this Agreement as a
whole and not to any particular provision of this Agreement.

     Section 1.3  Cross References.  Unless otherwise specified, references in
                  ----------------
this Agreement and in each other Loan Document to any Article or Section are
references to such Article or Section of this Agreement or such other Loan
Document, as the case may be, and, unless otherwise specified, references in any
Article, Section or definition to any clause are references to such clause in
such Article, Section or definition.

     Section 1.4  Accounting Provisions.  All accounting terms used in this
                  ---------------------
Agreement which are not expressly defined herein shall have the respective
meanings given to them in accordance with GAAP, all computations shall be made
in accordance with GAAP, and all balance sheets and other financial statements
shall be prepared in accordance with GAAP.  All financial or accounting
calculations or determinations required pursuant to this Agreement, unless
otherwise expressly provided, shall be made on a consolidated basis for the
Borrowers and the Restricted Subsidiaries.

                                     -30-
<PAGE>

                                ARTICLE 2 Loans

     Section 2.1  The Loans.
                  ---------

          (a) Revolving Loans.  The Lenders having Revolving Loan Commitments
              ---------------
agree severally, and not jointly, upon the terms and subject to the conditions
of this Agreement to lend to the Borrowers (on a joint and several basis) from
time to time prior to the Revolving Loan Maturity Date amounts which do not
exceed, (i) in the aggregate at any one time outstanding, the Revolving Loan
Commitments and, (ii) individually, such Lender's Revolving Loan Commitment, in
each case, as in effect from time to time; provided, however, that the Borrowers
                                           --------  -------
may not request (and the Lenders shall have no obligation to make) an Advance
under this Section 2.1(a) in excess of the Available Revolving Loan Commitment
on such date.

          (b) Term Loan A Loans.  The Lenders having Term Loan A Commitments
              -----------------
agree severally, and not jointly, upon the terms and subject to the conditions
of this Agreement to lend to the Borrowers (on a joint and several basis), on or
prior to December 31, 2000, amounts which do not exceed, (i) in the aggregate at
any one time outstanding, the Term Loan A Commitments and, (ii) individually,
such Lender's Term Loan A Commitment, in each case, as in effect from time to
time; provided, however, that the Borrowers may not request (and the Lenders
      --------  -------
shall have no obligation to make) an Advance in excess of the Available Term
Loan A Commitment on such date; and provided, further, however that amounts
                                    --------  -------  -------
repaid under the Term Loan A Commitments may not be reborrowed.  Notwithstanding
the foregoing, from and after July 1, 2000, the Available Term Loan A Commitment
shall not exceed $350,000,000.

          (c) Term Loan B Loans.  The Lenders having Term Loan B Commitments
              -----------------
agree severally, and not jointly, upon the terms and subject to the conditions
of this Agreement to lend to the Borrowers (on a joint and several basis) on the
Agreement Date amounts which do not exceed, (i) in the aggregate at any one time
outstanding, the Term Loan B Commitments and, (ii) individually, such Lender's
Term Loan B Commitment; provided, however, that the Borrowers may not request
                        --------  -------
(and the Lenders shall have no obligation to make) an Advance in excess of the
Available Term Loan B Commitment on such date; and provided further, however,
                                                   -------- -------  -------
that amounts repaid under the Term Loan B Commitments may not be reborrowed.

          (d) Letters of Credit.  Subject to the terms and conditions of this
              ------------------
Agreement, the Issuing Bank agrees to issue Letters of Credit for the account of
the Borrowers on a joint and several basis (and on behalf of the Restricted
Subsidiaries) pursuant to Section 2.14 hereof in an aggregate amount not to
exceed the Available Letter of Credit Commitment determined immediately prior to
giving effect to the issuance thereof.

     Section 2.2  Manner of Borrowing and Disbursement.
                  ------------------------------------

          (a) Choice of Interest Rate, Etc.  Any Advance hereunder shall, at the
              -----------------------------
option of the requesting Borrower, be made as a Base Rate Advance or a LIBOR
Advance; provided, however, that at such time as there shall have occurred and
         --------  -------
be continuing a Default hereunder, none of the Borrowers shall have the right to
receive or Continue a LIBOR Advance or to

                                     -31-
<PAGE>

Convert a Base Rate Advance to a LIBOR Advance. Any notice given to the
Administrative Agent in connection with a requested Advance hereunder shall be
given to the Administrative Agent prior to 11:00 a.m. (New York, New York time)
in order for such Business Day to count toward the minimum number of Business
Days required.

          (b)  Base Rate Advances.
               ------------------

               (i)  Advances.  A Borrower shall give the Administrative Agent in
                    --------
     the case of Base Rate Advances at least one (1) Business Day's irrevocable
     prior telephonic notice followed immediately by a Request for Advance;
     provided, however, that such Borrower's failure to confirm any telephonic
     --------  -------
     notice with a Request for Advance shall not invalidate any notice so given
     if acted upon by the Administrative Agent.  Upon receipt of such notice
     from a Borrower, the Administrative Agent shall promptly notify each Lender
     by telephone or telecopy of the contents thereof.

               (ii) Conversions.  Any Borrower may, without regard to the
                    -----------
     applicable Payment Date and upon at least three (3) Business Days'
     irrevocable prior telephonic notice followed by a Request for Advance,
     Convert all or a portion of the principal of a Base Rate Advance to a LIBOR
     Advance.  On the date indicated by the applicable Borrower, such Base Rate
     Advance shall be so Converted.  The failure to give timely notice hereunder
     with respect to the Payment Date of any Base Rate Advance shall be
     considered a request for a Base Rate Advance.

          (c)  LIBOR Advances.  Upon request, the Administrative Agent, whose
               --------------
determination in absence of manifest error shall be conclusive, shall determine
the available LIBOR Bases and shall notify the requesting Borrower of such LIBOR
Bases to apply for the applicable LIBOR Advance.

               (i)  Advances.  A Borrower shall give the Administrative Agent in
                    --------
     the case of LIBOR Advances at least three (3) Business Days' irrevocable
     prior telephonic notice followed immediately by a Request for Advance;
     provided, however, that such Borrower's failure to confirm any telephonic
     --------  -------
     notice with a Request for Advance shall not invalidate any notice so given
     if acted upon by the Administrative Agent.  Upon receipt of such notice
     from a Borrower, the Administrative Agent shall promptly notify each Lender
     by telephone or telecopy of the contents thereof.

               (ii) Conversions and Continuations.  At least three (3) Business
                    -----------------------------
     Days prior to the Payment Date for each LIBOR Advance, the applicable
     Borrower shall give the Administrative Agent telephonic notice followed by
     written notice specifying whether all or a portion of such LIBOR Advance
     (A) is to be Continued in whole or in part as one or more LIBOR Advances,
     (B) is to be Converted in whole or in part to a Base Rate Advance, or (C)
     is to be repaid.  The failure to give such notice shall preclude the
     Borrowers from Continuing such Advance as a LIBOR Advance on its Payment
     Date and shall be considered a request to Convert such Advance to a Base
     Rate Advance.  Upon

                                     -32-
<PAGE>

     such Payment Date such LIBOR Advance will, subject to the provisions
     hereof, be so Continued, Converted or repaid, as applicable.

          (d)  Notification of Lenders.  Upon receipt of irrevocable prior
               -----------------------
telephonic notice in accordance with Section 2.2(b) or (c) hereof or a Request
for Advance, or a notice of Conversion or Continuation from a Borrower with
respect to any outstanding Advance prior to the Payment Date for such Advance,
the Administrative Agent shall promptly but no later than the close of business
on the day of such notice notify each Lender having the applicable Commitment by
telephone, followed promptly by written notice, or telecopy of the contents
thereof and the amount of such Lender's portion of the Advance.  Each Lender
having the applicable Commitment shall, not later than 12:00 noon (New York, New
York time) on the date of borrowing specified in such notice, make available to
the Administrative Agent at the Administrative Agent's Office, or at such
account as the Administrative Agent shall designate, the amount of its portion
of any Advance that represents an additional borrowing hereunder in immediately
available funds.

          (e)  Disbursement.
               ------------

               (i)   Prior to 2:00 p.m. (New York, New York time) on the date of
     an Advance hereunder, the Administrative Agent shall, subject to the
     satisfaction of the conditions set forth in Article 3 hereof, disburse the
     amounts made available to the Administrative Agent by the Lenders in like
     funds by (A) transferring the amounts so made available by wire transfer
     pursuant to the requesting Borrower's instructions, or (B) in the absence
     of such instructions, crediting the amounts so made available to the
     account of the requesting Borrower maintained with the Administrative
     Agent.

               (ii)  Unless the Administrative Agent shall have received notice
     from a Lender having an applicable Commitment prior to 12:00 noon (New
     York, New York time) on the date of any Advance that such Lender will not
     make available to the Administrative Agent such Lender's ratable portion of
     such Advance, the Administrative Agent may assume that such Lender has made
     or will make such portion available to the Administrative Agent on the date
     of such Advance and the Administrative Agent may in its sole discretion and
     in reliance upon such assumption, make available to the requesting Borrower
     on such date a corresponding amount.  If and to the extent an applicable
     Lender does not make such ratable portion available to the Administrative
     Agent, such Lender agrees to repay to the Administrative Agent on demand
     such corresponding amount together with interest thereon, for each day from
     the date such amount is made available to the requesting Borrower until the
     date such amount is repaid to the Administrative Agent, at the Federal
     Funds Rate.

               (iii) If such Lender shall repay to the Administrative Agent
     such corresponding amount, such amount so repaid shall constitute such
     Lender's portion of the applicable Advance for purposes of this Agreement.
     If such Lender does not repay such corresponding amount immediately upon
     the Administrative Agent's demand therefor, the Administrative Agent shall
     notify the Borrowers, and the Borrowers shall

                                     -33-
<PAGE>

     immediately pay such corresponding amount to the Administrative Agent, with
     interest at the Federal Funds Rate. The failure of any Lender to fund its
     portion of any Advance shall not relieve any other Lender of its
     obligation, if any, hereunder to fund its respective portion of the Advance
     on the date of such borrowing, but no Lender shall be responsible for any
     such failure of any other Lender.

               (iv) In the event that, at any time when there is no Default and
     each of the conditions in Section 3.2 hereof has been satisfied, a Lender
     having an applicable Commitment for any reason fails or refuses to fund its
     portion of an Advance and such failure shall continue for a period in
     excess of thirty (30) days, then, until such time as such Lender has funded
     its portion of such Advance (which late funding shall not absolve such
     Lender from any liability it may have to the Borrowers), or all other
     Lenders have received payment in full from the Borrowers (whether by
     repayment or prepayment) or otherwise of the principal and interest due in
     respect of such Advance, such non-funding Lender shall not have the right
     (A) to vote regarding any issue on which voting is required or advisable
     under this Agreement or any other Loan Document, and such Lender's portion
     of the applicable Loans shall not be counted as outstanding for purposes of
     determining "Majority Lenders" hereunder, and (B) to receive payments of
     principal, interest or fees from the Borrowers, the Administrative Agent or
     the other Lenders in respect of its portion of the applicable Loans until
     all applicable Loans of the other Lenders have been fully paid.

     Section 2.3  Interest.
                  --------

          (a)  On Base Rate Advances.  Interest on each Base Rate Advance shall
               ---------------------
be computed on the basis of a year of 365/366 days for the actual number of days
elapsed and shall be payable at the Base Rate Basis for such Advance, in arrears
on the applicable Payment Date.  Interest on Base Rate Advances then outstanding
shall also be due and payable on the Maturity Date.

          (b)  On LIBOR Advances.  Interest on each LIBOR Advance shall be
               -----------------
computed on the basis of a 360-day year for the actual number of days elapsed
and shall be payable at the LIBOR Basis for such Advance, in arrears on the
applicable Payment Date, and, in addition, if the Interest Period for a LIBOR
Advance exceeds three (3) months, interest on such LIBOR Advance shall also be
due and payable in arrears on every three (3) month anniversary of the beginning
of such Interest Period.  Interest on LIBOR Advances then outstanding shall also
be due and payable on the Maturity Date.

          (c)  Interest if no Notice of Selection of Interest Rate Basis.  If a
               ---------------------------------------------------------
Borrower fails to give the Administrative Agent timely notice of its selection
of a LIBOR Basis, or if for any reason a determination of a LIBOR Basis for any
Advance is not timely concluded, the Base Rate Basis shall apply to such
Advance.

          (d)  Interest Upon Event of Default.  Immediately upon the occurrence
               ------------------------------
of an Event of Default hereunder, the outstanding principal balance of the Loans
shall bear interest at

                                     -34-
<PAGE>

the Default Rate. Such interest shall be payable on demand by the Majority
Lenders and shall accrue until the earlier of (i) waiver or cure of the
applicable Event of Default, (ii) agreement by the Majority Lenders (or, if
applicable to the underlying Event of Default, the Lenders) to rescind the
charging of interest at the Default Rate or (iii) payment in full of the
Obligations.

          (e)  LIBOR Contracts.  At no time may the number of outstanding LIBOR
               ---------------
Advances hereunder exceed twelve (12).

          (f)  Applicable Margin.
               -----------------

               (i)  Revolving Loans and Term Loan A Loans.  With respect to any
                    -------------------------------------
     Advance under the Revolving Loan Commitments or the Term Loan A
     Commitments, the Applicable Margin shall be as set forth in a certificate
     of the chief financial officer of a Borrower delivered to the
     Administrative Agent based upon the Leverage Ratio for the most recent
     fiscal quarter end for which financial statements are furnished by the
     Borrowers to the Administrative Agent and each Lender for the fiscal
     quarter most recently ended as follows:

<TABLE>
<CAPTION>
                 Leverage Ratio                         Base Rate           LIBOR Advance
                 --------------
                                                   Advance Applicable        Applicable
                                                         Margin                Margin
                                                         ------                ------
     <S>                                           <C>                      <C>
     A.   Greater than 7.00 to 1.00                      1.750%                 2.750%

     B.   Greater than 6.50 to 1.00, but less than
          or equal to 7.00 to 1.00                       1.500%                 2.500%

     C.   Greater than 6.00 to 1.00, but less than
          or equal to 6.50 to 1.00                       1.250%                 2.250%

     D.   Greater than 5.00 to 1.00, but less than
          or equal to 6.00 to 1.00                       1.000%                 2.000%

     E.   Greater than 4.00 to 1.00, but less than
          or equal to 5.00 to 1.00                       0.750%                 1.750%

     F.   Less than or equal to 4.00 to 1.00             0.500%                 1.500%
</TABLE>

     Notwithstanding the foregoing, the Applicable Margin with respect to
     Advances under the Revolving Loan Commitments and the Term Loan A
     Commitments from the Agreement Date through and including the Borrowing
     Base Termination Date, shall not be less than, (A) with respect to Base
     Rate Advances, 1.750%, and (B) with respect to LIBOR Advances, 2.750%.

               (ii) Term Loan B Loans.  With respect to any Advance under
                    -----------------

                                     -35-
<PAGE>

     the Term Loan B Commitments, the Applicable Margin shall be, (a) at all
     times from the Agreement Date through and including the Borrowing Base
     Termination Date, (1) with respect to Base Rate Advances, 2.250%, and (2)
     with respect to LIBOR Advances, 3.250%, and (b) at all times after the
     Borrowing Base Termination Date, (1) with respect to Base Rate Advances,
     2.000%, and (2) with respect to LIBOR Advances, 3.000%.

               (iii) With respect to Section 2.3(f)(i), changes to the
     Applicable Margin shall be effective, (i) with respect to an increase in
     the Applicable Margin, as of the second (2nd) Business Day after the day on
     which the financial statements are required to be delivered to the
     Administrative Agent and the Lenders pursuant to Section 6.1 or 6.2 hereof,
     as the case may be, provided, however, that if such financial statements
                         --------  -------
     are not delivered to the Administrative Agent and the Lenders on or before
     the date specified in such Section, such increase shall be effective as of
     the date specified in such Section for delivery of the financial
     statements, and (ii) with respect to a decrease in the Applicable Margin,
     as of the later of (A) the second (2nd) Business Day after the day on which
     such financial statements are required to be delivered pursuant to Section
     6.1 or 6.2 hereof, as the case may be, and (B) the date on which such
     financial statements are actually delivered to the Administrative Agent and
     the Lenders.  With respect to Section 2.3(f)(i) and (ii) upon the
     occurrence and during the continuance of an Event of Default, the
     Applicable Margins shall not be subject to downward adjustment and shall
     automatically revert to the Applicable Margins set forth in, (A) with
     respect to Section 2.3(f)(i), part A of the table in Section 2.3(f)(i)
     above, and (B) with respect to Section 2.3(f)(ii), part (a) of Section
     2.3(f)(ii) above, in each case, until such time as such Event of Default is
     cured or waived.

     Section 2.4  Commitment and Letter of Credit Fees.
                  ------------------------------------

          (a)  Commitment Fees.
               ---------------

               (i)   Revolving Loan Commitment. The Borrowers agree to pay, on a
                     -------------------------
     joint and several basis, to the Administrative Agent for the account of
     each of the Lenders having a Revolving Loan Commitment in accordance with
     such Lender's applicable Commitment Ratio, a commitment fee on the unused
     Revolving Loan Commitment of such Lender for each day from the Agreement
     Date through and including the Revolving Loan Maturity Date, at a rate of
     (A) one percent (1.000%) per annum when the Facility Usage during such
     calendar quarter was less than or equal to thirty-three and one-third
     percent (33-1/3%), (B) three-quarters of one-percent (0.750%) when the
     Facility Usage during such calendar quarter was greater than thirty-three
     and one-third percent (33-1/3%), but less than or equal to sixty-six and
     two-thirds percent (66-2/3%), and (C) one-half of one percent (0.500%) when
     the Facility Usage during such calendar quarter was greater than sixty-six
     and two-thirds percent (66-2/3%). Such commitment fee shall be computed on
     the basis of a year of 365/366 days for the actual number of days elapsed,
     shall be payable quarterly in arrears on the last Business Day of each
     calendar quarter, and shall be fully earned when due and non-refundable
     when paid. A

                                     -36-
<PAGE>

     final payment of any commitment fee then payable with respect to the
     Revolving Loan Commitments shall also be due and payable on the Revolving
     Loan Maturity Date.

               (ii) Term Loan A Commitment.  The Borrowers agree to pay, on a
                    ----------------------
     joint and several basis, to the Administrative Agent for the account of
     each Lender having a Term Loan A Commitment in accordance with such
     Lender's applicable Commitment Ratio, a commitment fee on the unused Term
     Loan A Commitment of such Lender (after giving effect to any required
     reductions to the Available Term Loan A Commitment pursuant to Section
     2.1(b) hereof) for each day from the Agreement Date through and including
     December 31, 2000 at a rate of (A) one percent (1.000%) per annum when the
     Facility Usage during such calendar quarter was less than or equal to
     thirty-three and one-third percent (33-1/3%), (B) three-quarters of one
     percent (0.750%) when the Facility Usage during such calendar quarter was
     greater than thirty-three and one-third percent (33-1/3%), but less than or
     equal to sixty-six and two-thirds percent (66-2/3%), and (C) one-half of
     one percent (0.500%) when the Facility Usage during such calendar quarter
     was greater than sixty-six and two-thirds percent (66-2/3%).  Such
     Commitment Fee shall be computed on the basis of a year of 365/366 days for
     the actual number of days elapsed, shall be payable quarterly in arrears on
     the last Business Day of each calendar quarter, and shall be fully earned
     when due and non-refundable when paid.  A final payment of any commitment
     fee then payable with respect to the Term Loan A Commitments shall be due
     and payable on December 31, 2000.

          (b)  Letter of Credit Fees.
               ---------------------

               (i)  The Borrowers agree to pay, on a joint and several basis, to
     the Issuing Bank a fee on the stated amount (reduced by the amount of any
     draws) of any outstanding Letters of Credit from the date of issuance
     through and including the expiration date of each such Letter of Credit at
     a rate of one eighth of one percent (0.125%) per annum, which fee shall be
     computed on the basis of a year of 365/366 days for the actual number of
     days elapsed, shall be payable quarterly in arrears on the last Business
     Day of each calendar quarter commencing on March 31, 2000, and shall be
     fully earned when due and non-refundable when paid.

               (ii) The Borrowers agree to pay, on a joint and several basis, to
     the Administrative Agent on behalf of the Lenders having a Revolving Loan
     Commitment in accordance with their respective Commitment Ratios for the
     Revolving Loans (and the Administrative Agent shall promptly pay to the
     Lenders having a Revolving Loan Commitment), a fee on the stated amount
     (reduced by the amount of any draws) of any outstanding Letters of Credit
     for each day from the date of issuance thereof through the expiration date
     for each such Letter of Credit at a rate equal to the Applicable Margin for
     LIBOR Advances under the Revolving Loan Commitments.  Such Letter of Credit
     Fee shall be computed on the basis of a year of 365/366 days for the actual
     number of days elapsed, shall be payable quarterly in arrears for each
     quarter on the last Business Day of each calendar quarter commencing on
     March 31, 2000, and shall be fully earned when due and non-refundable when
     paid.  The Letter of Credit Fee set forth in this Section

                                     -37-
<PAGE>

     2.4(b)(ii) shall be subject to increase and decrease on the dates and in
     the amounts set forth in Section 2.3(f)(i) hereof in the same manner as the
     adjustment of the Applicable Margin with respect to LIBOR Advances upon
     satisfaction of the requirements set forth in Section 2.3(f)(i) hereof.

     Section 2.5  Mandatory Commitment Reductions.
                  -------------------------------

          (a) Scheduled Reductions under Revolving Loan Commitments.  Commencing
              -----------------------------------------------------
March 31, 2003, and on the last day of each calendar quarter ending during the
periods set forth below, the Revolving Loan Commitments as of March 30, 2003
shall be automatically and permanently reduced until reduced to zero by the
percentage amounts set forth below:

                                                         Quarterly
                                                   Percentage of Revolving
                                                   Loan Commitment as of
                    Reduction Dates                     March 30, 2003
                    ---------------                     --------------

     March 31, 2003, June 30, 2003, September 30, 2003
     and December 31, 2003                                  1.500%

     March 31, 2004, June 30, 2004,
     September 30, 2004 and December 31, 2004               5.500%

     March 31, 2005, June 30, 2005,
     September 30, 2005 and December 31, 2005               7.000%

     March 31, 2006, June 30, 2006,
     September 30, 2006 and December 31, 2006               7.375%

     March 31, 2007 and June 30, 2007                       7.250%

          (b) Reduction From Excess Cash Flow.  On or prior to April 15, 2004,
              -------------------------------
and on or prior to each April 15/th/ thereafter during the term of this
Agreement, the Revolving Loan Commitments (and, if applicable, the Incremental
Facility Commitments) shall be automatically and permanently reduced by an
amount equal to the repayment of Revolving Loans (and, if applicable, the
Incremental Facility Loans) required under Section 2.7(b)(iv) hereof; provided,
                                                                      --------
however, that if there are no Loans then outstanding, or if the Excess Cash Flow
-------
exceeds the Loans then outstanding, the Revolving Loan Commitments (and, if
applicable, the Incremental Facility Commitments) shall be reduced by an
aggregate amount equal to the Excess Cash Flow, or the excess of the Excess Cash
Flow over the Loans (which reduction shall be in addition to the reduction set
forth in the first part of this Section 2.5(b)), as applicable, regardless of
any repayment of the Revolving Loans.  Reductions under this Section 2.5(b)to
the Revolving Loan Commitments shall be applied to the reductions set forth in
Section 2.5(a) hereof (and, if applicable, to the Incremental Facility
Commitments shall be applied to the reductions set forth

                                     -38-
<PAGE>

in the Notice of Incremental Facility Commitments) in inverse order of the
reductions set forth therein.

          (c) Reduction From Asset Sales and Insurance and Condemnation
              ---------------------------------------------------------
Proceedings.  At any time after the aggregate Unreinvested Net Proceeds from all
-----------
sales, transfers or other dispositions of assets of the Borrowers and their
Restricted Subsidiaries, or from any insurance or condemnation proceeding in
respect of such assets, after the Agreement Date exceeds $10,000,000.00, the
Revolving Loan Commitments (and prior to December 31, 2000 if the full amount of
the Term Loan A Commitments has not been cancelled or borrowed, the Term Loan A
Commitments and, if applicable, the Incremental Facility Commitments) shall be
automatically and permanently reduced by an amount equal to the repayment of
Revolving Loans (and, if applicable, the Term Loan A Loans and/or the
Incremental Facility Loans) required under Section 2.7(b)(iii) hereof; provided,
                                                                       --------
however, that if there are no Loans then outstanding, or if the Unreinvested Net
-------
Proceeds exceeds the Loans then outstanding, the Revolving Loan Commitments
(and, if applicable, the Term Loan A Commitments and/or the Incremental Facility
Commitments) shall be reduced on a pro rata basis by an aggregate amount equal
to such Unreinvested Net Proceeds, or the excess of such Unreinvested Net
Proceeds over the Loans (which reduction shall be in addition to the reduction
set forth in the first part of this Section 2.5(c)), as applicable, regardless
of any repayment of the Revolving Loans (or, if applicable, the Term Loans A
Loans and/or the Incremental Facility Loans).  Reductions under this Section
2.5(c) to the Revolving Loan Commitments shall be applied to the reductions set
forth in Section 2.5(a) hereof (and, if applicable, to the Incremental Facility
Commitments shall be applied to the reductions set forth in the Notice of
Incremental Facility Commitments) in inverse order of the reductions set forth
therein.

          (d) Reduction From Sale of Capital Stock and Debt Instruments.  On the
              ---------------------------------------------------------
Business Day following the date of receipt by the Parent, any Borrower or any
Restricted Subsidiary of any Capital Raise Proceeds, the Revolving Loan
Commitments (and prior to December 31, 2000, if the full amount of the Term Loan
A Commitments has not been cancelled or borrowed, the Term Loan A Commitments
and, if applicable, the Incremental Facility Commitments) shall be automatically
and permanently reduced by an amount equal to the repayment of Revolving Loans
(and, if applicable, Term Loan A Loans and/or the Incremental Facility Loans)
required under Section 2.7(b)(v) hereof; provided, however, that if there are no
                                         --------  -------
Loans then outstanding, or if the Capital Raise Proceeds exceeds the Loans then
outstanding, the Revolving Loan Commitments (and, if applicable, the Term Loan A
Commitments and/or the Incremental Facility Commitments) shall be reduced on a
pro rata basis by an amount equal to the Capital Raise Proceeds, or the excess
of the Capital Raise Proceeds over the Loans (which reduction shall be in
addition to the reduction set forth in the first part of this Section 2.5(d)),
as applicable, regardless of any repayment of the Revolving Loans (or, if
applicable, the Term Loan A Loans and/or Incremental Facility Loans).
Reductions under this Section 2.5(d) to the Revolving Loan Commitments shall be
applied to the reductions set forth in Section 2.5(a) hereof (and, if
applicable, to the Incremental Facility Commitments shall be applied to the
reductions set forth in the Notice of Incremental Facility Commitments) in
inverse order of the reductions set forth therein.

                                     -39-
<PAGE>

     Section 2.6  Voluntary Commitment Reductions.  The Borrowers shall have the
                  -------------------------------
right, at any time and from time to time after the Agreement Date and prior to
the Maturity Date, upon at least three (3) Business Days' prior written notice
to the Administrative Agent, without premium or penalty, to cancel or reduce
permanently all or a portion of the Revolving Loan Commitments, the Term Loan A
Commitments or, if applicable, the Incremental Facility Commitments; provided,
                                                                     --------
however, that any such partial reduction shall be made in an amount not less
-------
than $5,000,000.00 and in an integral multiple of $1,000,000.00.  As of the date
of cancellation or reduction set forth in such notice, the Revolving Loan
Commitments, Term Loan A Commitments or, if applicable, the Incremental Facility
Commitments shall be permanently reduced to the amount stated in such notice for
all purposes herein, and the Borrowers shall, on a joint and several basis, pay
to the Administrative Agent for the applicable Lenders the amount necessary to
reduce the principal amount of the Revolving Loans or, if applicable,
Incremental Facility Loans then outstanding under the Revolving Loan Commitments
or, if applicable, the Incremental Facility Commitments, respectively, to not
more than the amount of Revolving Loan Commitments or, if applicable, the
Incremental Facility Commitments, respectively, as so reduced, together with
accrued interest on the amount so prepaid and commitment fees accrued through
the date of the reduction with respect to the amount reduced.  Commitment
reductions made pursuant to this Section 2.6 shall be applied, with respect to
the Revolving Loan Commitments, pro rata to the reductions in Section 2.5(a)
hereof.

     Section 2.7  Prepayments and Repayments.
                  --------------------------

          (a)  Prepayment.  The principal amount of any Base Rate Advance may be
               ----------
prepaid in full or ratably in part at any time, without premium or penalty and
without regard to the Payment Date for such Advance.  LIBOR Advances may be
prepaid prior to the applicable Payment Date, upon three (3) Business Days'
prior written notice, or telephonic notice followed immediately by written
notice, to the Administrative Agent; provided, however, that the Borrowers
                                     --------  -------
shall, jointly and severally, reimburse the applicable Lenders, on the earlier
of demand by the applicable Lender or the Maturity Date, for any loss or out-of-
pocket expense incurred by any such Lender in connection with such prepayment,
as set forth in Section 2.10 hereof; and provided further, however, that the
                                         -------- -------  -------
Borrowers' failure to confirm any telephonic notice with a written notice shall
not invalidate any notice so given if acted upon by the Administrative Agent.
Any prepayment hereunder shall be in amounts of not less than $5,000,000.00 and
in an integral multiple  of $1,000,000.00.  Amounts prepaid pursuant to this
Section 2.7(a) may, with respect to the Revolving Loans, be reborrowed, subject
to the terms and conditions hereof, and shall be applied, with respect to the
Term Loan A Loans and Term Loan B Loans, pro rata to the repayments in Section
2.7(b)(i) hereof.  Amounts prepaid shall be paid together with accrued interest
on the amount so prepaid and commitment fees accrued through the date of the
reduction with respect to the amount reduced.

          (b)  Repayments.  The Borrowers shall repay the Loans, on a joint and
               ----------
several basis, as follows:

                                     -40-
<PAGE>

               (i)   Scheduled Repayments of the Term Loan A Loans and Term Loan
                     -----------------------------------------------------------
     B Loans. Commencing March 31, 2003, and on the last day of each calendar
     -------
     quarter ending during the periods set forth below, the principal balance of
     the Term Loan A Loans and Term Loan B Loans outstanding on March 30, 2003
     shall be repaid until paid in full by the percentage amounts set forth
     below:

<TABLE>
<CAPTION>
                                                      Quarterly                       Quarterly
                                               Percentage of Principal of      Percentage of Principal of
                                             Term Loan A Loans Outstanding   Term Loan B Loans Outstanding
                                                on March 30, 2003 Due           on March 30, 2003 Due
          Repayment Dates                       on Each Repayment Date          on Each Repayment Date
          ---------------                       ----------------------          ----------------------
<S>                                          <C>                             <C>
March 31, 2003, June 30, 2003,
September 30, 2003 and December 31, 2003                  1.500%                          0.250%

March 31, 2004, June 30, 2004,
September 30, 2004 and December 31, 2004                  5.500%                          0.250%

March 31, 2005, June 30, 2005,
September 30, 2005 and December 31, 2005                  7.000%                          0.250%

March 31, 2006, June 30, 2006,
September 30, 2006 and December 31, 2006                  7.375%                          0.250%

March 31, 2007 and June 30, 2007                          7.250%                          0.250%

September 30, 2007 and December 31, 2007              Not applicable                     47.750%
</TABLE>

               (ii)  Revolving Loans and Letter of Credit Obligations in Excess
                     ----------------------------------------------------------
     of Revolving Loan Commitments (if applicable, and/or Incremental Facility
     -------------------------------------------------------------------------
     Commitments).  If, at any time, the amount of the Revolving Loans and
     ------------
     Letter of Credit Obligations (or, if applicable, the Incremental Facility
     Loans) shall exceed the Revolving Loan Commitments (or, if applicable, the
     Incremental Facility Commitments), the Borrowers shall, on such date and
     subject to Section 2.10 hereof, make a repayment of the principal amount of
     the Revolving Loans (or, if applicable, the Incremental Facility Loans),
     or, if there are no such Loans then outstanding, establish, if applicable,
     a Letter of Credit Reserve Account, in each case, in an amount equal to
     such excess, together with any accrued interest and fees with respect
     thereto.

               (iii) Unreinvested Net Proceeds from Asset Sales and Insurance
                     --------------------------------------------------------
     and Condemnation Proceedings.  At any time after the aggregate Unreinvested
     ----------------------------
     Net Proceeds from all sales, transfers or other dispositions of assets of
     the Borrowers and their Restricted Subsidiaries or from any insurance or
     condemnation proceeding in respect of such assets after the Agreement Date
     exceeds $10,000,000.00, the Loans shall be repaid in an amount equal to, in
     the aggregate, such Unreinvested Net Proceeds.  The amount of the
     Unreinvested Net Proceeds required to be repaid under this Section
     2.7(b)(iii) shall be applied to the Loans then outstanding on a pro rata
     basis.  Accrued interest on the principal amount of the Loans being repaid
     pursuant to this Section 2.7(b)(iii) to the date

                                     -41-
<PAGE>

     of such repayment will be paid by the Borrowers concurrently with such
     principal repayment. All repayments under this Section 2.7(b)(iii) of each
     of the Term Loan A Loans and the Term Loan B Loans shall be applied to the
     repayments for such Loan in Section 2.7(b)(i) hereof in inverse order of
     maturity.

               (iv)   Excess Cash Flow. On or prior to April 15, 2004 and on or
                      ----------------
     prior to each April 15/th/ thereafter during the term of this Agreement,
     the Loans shall be repaid in an amount equal to, in the aggregate, fifty
     percent (50%) of the Excess Cash Flow for the fiscal year ended on the
     immediately preceding December 31/st/.  The amount of the Excess Cash Flow
     required to be repaid under this Section 2.7(b)(iv) shall be applied to the
     Loans then outstanding on a pro rata basis.  Accrued interest on the
     principal amount of the Loans being repaid pursuant to this Section
     2.7(b)(iv) to the date of such repayment will be paid by the Borrowers
     concurrently with such principal repayment.  All repayments under this
     Section 2.7(b)(iv) of each of the Term Loan A Loans and the Term Loan B
     Loans shall be applied to the repayments for such Loans in Section
     2.7(b)(i) hereof in inverse order of maturity.

               (v)    Sale of Capital Stock and Debt Instruments. On the
                      ------------------------------------------
     Business Day following the date of receipt by the Parent, any Borrower or
     any Restricted Subsidiary of any Capital Raise Proceeds, the Loans shall be
     repaid in an amount equal to, in the aggregate, the Capital Raise Proceeds.
     The amount of the Capital Raise Proceeds required to be repaid under this
     Section 2.7(b)(v) shall be applied to the Loans, then outstanding on a pro
     rata basis. Accrued interest on the principal amount of the Loans being
     prepaid pursuant to this Section 2.7(b)(v) to the date of such prepayment
     will be paid by the Borrowers concurrently with such principal prepayment.
     All repayments under this Section 2.7(b)(v) of each of the Term Loan A
     Loans and the Term Loan B Loans shall be applied to the repayments for such
     Loans in Section 2.7(b)(i) hereof in inverse order of maturity.

               (vi)   Loans in Excess of Borrowing Base. If, on any date prior
                      ---------------------------------
     to the Borrowing Base Termination Date, the Loans then outstanding exceed
     the Borrowing Base on such date, the Loans shall be repaid in an amount
     equal to, in the aggregate, such excess. The Borrowers may, at their
     option, apply such reduction to the Revolving Loans, the Term Loan A Loans
     or Term Loan B Loans.

               (vii)  Revolving Loan Maturity Date.  In addition to the
                      ----------------------------
     foregoing, a final payment of all Revolving Loans, together with accrued
     interest and fees with respect thereto, shall be due and payable on the
     Revolving Loan Maturity Date.

               (viii) Term Loan A Maturity Date.  In addition to the foregoing,
                      -------------------------
     a final payment of the Term Loan A Loans, together with accrued interest
     and fees with respect thereto, shall be due and payable on the Term Loan A
     Maturity Date.

               (ix)   Term Loan B Maturity Date. In addition to the foregoing, a
                      -------------------------
     final payment of Term Loan B Loans, together with accrued interest and fees
     with respect

                                     -42-
<PAGE>

     thereto and all other Obligations then outstanding, other than the
     Incremental Facility Loans, if any, shall be due and payable on the Term
     Loan B Maturity Date.

               (x)  Incremental Facility Maturity Date.  If applicable, in
                    ----------------------------------
     addition to the foregoing, a final payment of the Incremental Facility
     Loans, together with accrued interest and fees with respect thereto, shall
     be due and payable on the Incremental Facility Maturity Date.

     Section 2.8  Notes; Loan Accounts.
                  --------------------

          (a)  The Loans shall be repayable in accordance with the terms and
provisions set forth herein and shall be evidenced by the Notes.  One (1)
Revolving Loan Note, one (1) Term Loan A Note, one (1) Term Loan B Note and, if
applicable, one (1) Incremental Facility Note shall be payable to the order of
each applicable Lender in accordance with such Lender's applicable Commitment
Ratio for Revolving Loans, the Term Loan A Loans, the Term Loan B Loans and, if
applicable, the Incremental Facility Loans, as the case may be.  The Notes shall
be issued on a joint and several basis by the Borrowers to the Lenders and shall
be duly executed and delivered by one or more Authorized Signatories.  Any
Lender (i) which is not a U.S. Person (a "Non-U.S. Bank") and (ii) which could
                                          -------------
become completely exempt from withholding of United States federal income taxes
in respect of payment of any obligations due to such Lender hereunder relating
to any of its Loans if such Loans were in registered form for United States
federal income tax purposes may request the Borrowers (through the
Administrative Agent), and the Borrowers agree thereupon, to register such Loans
as provided in Section 11.5(g) hereof and to issue to such Lender Notes
evidencing such Loans as Registered Notes or to exchange Notes evidencing such
Loans for new Registered Notes, as applicable.  Registered Notes may not be
exchanged for Notes that are not in registered form.

          (b)  Each Lender may open and maintain on its books in the name of the
Borrowers a loan account with respect to its portion of the Loans and interest
thereon.  Each Lender which opens such a loan account shall debit such loan
account for the principal amount of its portion of each Advance made by it and
accrued interest thereon, and shall credit such loan account for each payment on
account of principal of or interest on its Loans.  The records of a Lender with
respect to the loan account maintained by it shall be prima facie evidence of
its portion of the Loans and accrued interest thereon absent manifest error, but
the failure of any Lender to make any such notations or any error or mistake in
such notations shall not affect the Borrowers' repayment obligations with
respect to such Loans.

          Section 2.9  Manner of Payment.
                       -----------------

          (a)  Each payment (including, without limitation, any prepayment) by
the Borrowers on account of the principal of or interest on the Loans,
commitment fees and any other amount owed to the Lenders or the Administrative
Agent or any of them under this Agreement or the Notes shall be made not later
than 1:00 p.m. (New York, New York time) on the date specified for payment under
this Agreement to the Administrative Agent at the Administrative Agent's Office,
for the account of the Lenders or the Administrative Agent, as

                                     -43-
<PAGE>

the case may be, in lawful money of the United States of America in immediately
available funds. Any payment received by the Administrative Agent after 1:00
p.m. (New York, New York time) shall be deemed received on the next Business
Day. Receipt by the Administrative Agent of any payment intended for any Lender
or Lenders hereunder prior to 1:00 p.m. (New York, New York time) on any
Business Day shall be deemed to constitute receipt by such Lender or Lenders on
such Business Day. In the case of a payment for the account of a Lender, the
Administrative Agent will promptly, but no later than the close of business on
the date such payment is deemed received, thereafter distribute the amount so
received in like funds to such Lender. If the Administrative Agent shall not
have received any payment from the Borrowers as and when due, the Administrative
Agent will promptly notify the applicable Lenders accordingly. In the event that
the Administrative Agent shall fail to make distribution to any Lender as
required under this Section 2.9, the Administrative Agent agrees to pay such
Lender interest from the date such payment was due until paid at the Federal
Funds Rate.

          (b) The Borrowers agree to pay, on a joint and several basis,
principal, interest, fees and all other amounts due hereunder or under the Notes
without set-off or counterclaim or any deduction whatsoever.

          (c) Prior to the acceleration of the Loans under Section 8.2 hereof,
if some but less than all amounts due from the Borrowers are received by the
Administrative Agent with respect to the Obligations, the Administrative Agent
shall distribute such amounts in the following order of priority, all on a pro
rata basis to the Lenders: (i) to the payment on a pro rata basis of any fees or
expenses then due and payable to the Administrative Agent and the Issuing Bank,
or any of them or expenses then due and payable to the Lenders; (ii) to the
payment of interest then due and payable on the Loans on a pro rata basis and of
fees then due and payable to the Lenders on a pro rata basis; (iii) to the
payment of all other amounts not otherwise referred to in this Section 2.9(c)
then due and payable to the Administrative Agent, the Issuing Bank and the
Lenders, or any of them, hereunder or under the Notes or any other Loan
Document; and (iv) to the payment of principal then due and payable on the Loans
on a pro rata basis.

          (d) Subject to any contrary provisions in the definition of Interest
Period, if any payment under this Agreement or any of the other Loan Documents
is specified to be made on a day which is not a Business Day, it shall be made
on the next Business Day, and such extension of time shall in such case be
included in computing interest and fees, if any, in connection with such
payment.

          (e) Each Registered Noteholder (or, if such Registered Noteholder is
not the beneficial owner thereof, such beneficial owner) shall deliver to the
Borrowers (with a copy to the Administrative Agent) prior to or at the time it
becomes a Registered Noteholder, a Form 1001, 4224 or W-8 (or such successor and
related forms as may from time to time be adopted by the relevant taxing
authorities of the United States of America), together with an annual
certificate stating that such Registered Noteholder or beneficial owner, as the
case may be, is not a "bank" within the meaning of Section 881(c)(3)(A) of the
Code and is not otherwise described in Section 881(c)(3) of the Code.  Each
Registered Noteholder or beneficial owner, as the case may be, shall promptly
notify the Borrowers (with a copy to the Administrative Agent) if at any

                                     -44-
<PAGE>

time, such Registered Noteholder or beneficial owner, as the case may be,
determines that it is no longer in a position to make the certification made in
such certificate to the Borrowers (or any other form of certification adopted by
the relevant taxing authorities of the United States of America for such
purposes).

     Section 2.10  Reimbursement.
                   -------------

          (a)  Whenever any Lender shall sustain or incur any losses or
reasonable out-of-pocket expenses in connection with (i) failure by a Borrower
to borrow, Continue or Convert any LIBOR Advance after having given notice of
its intention to borrow, Continue or Convert such Advance in accordance with
Section 2.2 hereof (whether by reason of such Borrower's election not to proceed
or the non-fulfillment of any of the conditions set forth in Article 3 hereof),
or (ii) prepayment (or failure to prepay after giving notice thereof) of any
LIBOR Advance in whole or in part for any reason, the Borrowers agree to pay, on
a joint and several basis, to such Lender, upon such Lender's demand, an amount
sufficient to compensate such Lender for all such losses and out-of-pocket
expenses.  Such Lender's good faith determination of the amount of such losses
or out-of-pocket expenses, as set forth in writing and accompanied by
calculations in reasonable detail demonstrating the basis for its demand, shall
be presumptively correct absent manifest error.

          (b)  Losses subject to reimbursement hereunder shall include, without
limiting the generality of the foregoing, lost margins, expenses incurred by any
Lender or any participant of such Lender permitted hereunder in connection with
the re-employment of funds prepaid, paid, repaid, not borrowed, or not paid, as
the case may be, and will be payable whether the applicable Maturity Date is
changed by virtue of an amendment hereto (unless such amendment expressly waives
such payment) or as a result of acceleration of the Loans.

     Section 2.11  Pro Rata Treatment.
                   ------------------

          (a)  Advances.  Each Advance under the Revolving Loan Commitments from
               --------
the Lenders hereunder shall be made pro rata on the basis of the applicable
Commitment Ratios of the Lenders having a Revolving Loan Commitment.  Each
Advance under the Term Loan A Commitment shall be made pro rata on the basis of
the applicable Commitment Ratios of the Lenders having Term Loan A Commitments.
Each Advance under the Term Loan B Commitment shall be made pro rata on the
basis of the applicable Commitment Ratios of the Lenders having a Term Loan B
Commitments.

          (b)  Payments.  Each payment and prepayment of principal of the Loans,
               --------
and, except as provided in Section 2.2(e) hereof and Article 10 hereof, each
payment of interest on the Loans, shall be made to the Lenders pro rata on the
basis of their respective unpaid principal amounts outstanding under the
applicable Loans immediately prior to such payment or prepayment.  If any Lender
shall obtain any payment (whether involuntary, through the exercise of any right
of set-off, or otherwise) on account of the Loans in excess of its ratable share
of the Loans under its applicable Commitment Ratio, such Lender shall forthwith
purchase from the other Lenders such participations in the portion of the
applicable Loans made by them as shall be

                                     -45-
<PAGE>

necessary to cause such purchasing Lender to share the excess payment ratably
with each of them; provided, however, that if all or any portion of such excess
                   --------  -------
payment is thereafter recovered from such purchasing Lender, such purchase from
each Lender shall be rescinded and each such other Lender shall repay to the
purchasing Lender the purchase price to the extent of such recovery. The
Borrowers agree that any Lender so purchasing a participation from another
Lender pursuant to this Section 2.11(b) may, to the fullest extent permitted by
law, exercise all its rights of payment (including, without limitation, the
right of set-off) with respect to such participation as fully as if such
purchasing Lender were the direct creditor of the Borrowers in the amount of
such participation.

          (c) Commitment Reductions.  Any reduction of the Revolving Loan
              ---------------------
Commitments or Term Loan A Commitments required or permitted hereunder shall
reduce, as applicable, the Revolving Loan Commitment and Term Loan A Commitment
of each Lender having such a commitment on a pro rata basis based on the
Commitment Ratio of such Lender for such commitment.

     Section 2.12  Capital Adequacy.  If after the date hereof, the adoption of
                   ----------------
any Applicable Law regarding the capital adequacy of banks or bank holding
companies, or any change in Applicable Law (whether adopted before or after the
Agreement Date) or any change in the interpretation or administration thereof by
any governmental authority, central bank or comparable agency charged with the
interpretation or administration thereof, or compliance by such Lender (or the
bank holding company of such Lender) with any directive regarding capital
adequacy (whether or not having the force of law) of any such governmental
authority, central bank or comparable agency, has or would have the effect of
reducing the rate of return on any Lender's capital as a consequence of its
obligations hereunder with respect to the Loans and the Commitments to a level
below that which it could have achieved but for such adoption, change or
compliance (taking into consideration such Lender's policies with respect to
capital adequacy immediately before such adoption, change or compliance and
assuming that such Lender's (or the bank holding company of such Lender) capital
was fully utilized prior to such adoption, change or compliance) by an amount
reasonably deemed by such Lender to be material, then, upon demand by such
Lender, the Borrowers shall promptly pay, on a joint and several basis, to such
Lender such additional amounts as shall be sufficient to compensate such Lender
(on an after-tax basis) for such reduced return, together with interest on such
amount from the fourth (4th) Business Day after the date of demand or the
applicable Maturity Date, as applicable, until payment in full thereof at the
Default Rate.  A certificate of such Lender setting forth the amount to be paid
to such Lender by the Borrowers as a result of any event referred to in this
paragraph and supporting calculations in reasonable detail shall be
presumptively correct absent manifest error.

     Section 2.13  Lender Tax Forms.  On or prior to the Agreement Date and, to
                   ----------------
the extent permitted by applicable U.S. Federal law, on or prior to the first
Business Day of each calendar year thereafter, each Lender which is organized in
a jurisdiction other than the United States shall provide each of the
Administrative Agent and the Borrowers (a), if such Lender is a "bank" under
Section 881(c)(3)(A) of the Code, with a properly executed originals of Forms
4224 or 1001 (or any successor form) prescribed by the Internal Revenue Service
or other documents

                                     -46-
<PAGE>

satisfactory to the Borrowers and the Administrative Agent, and properly
executed Internal Revenue Service Forms W-8 or W-9, as the case may be,
certifying (i) as to such Lender's status for purposes of determining exemption
from United States withholding taxes with respect to all payments to be made to
such Lender hereunder and under the Notes or (ii) that all payments to be made
to such Lender hereunder and under the Notes are subject to such taxes at a rate
reduced to zero by an applicable tax treaty, or (b), if such Lender is not a
"bank" within the meaning of Section 881(c)(3)(A) of the Code and intends to
claim exemption from U.S. Federal withholding tax under Section 871(h) or 881(c)
of the Code with respect to payments of "portfolio interest", a Form W-8, or any
subsequent versions thereof or successors thereto (and, if such Lender delivers
a Form W-8, a certificate representing that such Lender is not a bank for
purposes of Section 881(c) of the Code, is not a ten-percent (10%) shareholder
(within the meaning of Section 871(h)(3)(B) of the Code and is not a controlled
foreign corporation related to the Borrowers (within the meaning of Section
864(d)(4) of the Code)), properly completed and duly executed by such Lender,
indicating that such Lender is entitled to receive payments under this Agreement
without deduction or withholding of any United States federal income taxes as
permitted by the Code. To the extent permitted by applicable U.S. Federal law,
each such Lender agrees to provide the Administrative Agent and the Borrowers
with new forms prescribed by the Internal Revenue Service upon the expiration or
obsolescence of any previously delivered form, or after the occurrence of any
event requiring a change in the most recent forms delivered by it to the
Administrative Agent and the Borrowers.

     Section 2.14  Letters of Credit.
                   -----------------

          (a)  Subject to the terms and conditions hereof, the Issuing Bank, on
behalf of the Lenders having a Revolving Loan Commitment, and in reliance on the
agreements of such Lenders set forth in Section 2.14(d) hereof, hereby agrees to
issue one or more Letters of Credit up to an aggregate face amount equal to the
Available Letter of Credit Commitment determined immediately prior to giving
effect to the issuance thereof; provided, however, that the Issuing Bank shall
                                --------  -------
not issue any Letter of Credit (i) unless the conditions precedent to the
issuance thereof set forth in Section 3.3 hereof have been satisfied, (ii) if
any Default then exists or would be caused thereby, (iii) if, after giving
effect to such issuance, the Available Revolving Loan Commitment would be less
than zero or (iv) within thirty (30) days preceding the Maturity Date; and
provided further, however, that at no time shall the aggregate amount of the
-------- -------  -------
Letter of Credit Obligations outstanding hereunder exceed $50,000,000.00.  Each
Letter of Credit shall (A) be payable at sight, (B) be denominated in United
States dollars, (C) expire, (i) with respect to Standby Letters of Credit, no
later than the earlier to occur of (x) the fifth Business Day preceding the
Revolving Loan Maturity Date and (y) 360 days after its date of issuance (but
may contain provisions for automatic renewal provided that no Default or Event
of Default exists on the renewal date or would be caused by such renewal), and
(ii) with respect to Commercial Letters of Credit, no later than the earlier to
occur of (x) the thirtieth day preceding the Revolving Loan Maturity Date and
(y) 180 days after its date of Issuance (but may contain provisions for
automatic renewal provided that no Default or Event of Default exists on the
renewal date or would be caused by such renewal).  Each Letter of Credit shall
be subject to the Uniform Customs and Practice for Documentary Credits (1993
Revision), International Chamber of Commerce Publication No. 500 and, to the
extent not inconsistent therewith, the laws of the

                                     -47-
<PAGE>

State of New York. The Issuing Bank shall not at any time be obligated to issue,
or cause to be issued, any Letter of Credit if such issuance would conflict
with, or cause the Issuing Bank to exceed any limits imposed by, any Applicable
Law. If a Letter of Credit provides that it is automatically renewable unless
notice is given by the Issuing Bank that it will not be renewed, the Issuing
Bank shall not be bound to give a notice of non-renewal unless directed to do so
by Lenders having in the aggregate at least fifty-one percent (51%) of the
Revolving Loan Commitment at least sixty-five (65) days prior to the then
scheduled expiration date of such Letter of Credit.

          (b) Any Borrower may from time to time request the Issuing Bank to
issue Letters of Credit.  The Borrower shall execute and deliver to the
Administrative Agent and the Issuing Bank a Request for Issuance of Letter of
Credit for each Letter of Credit to be issued by the Issuing Bank not later than
12:00 noon (New York, New York time) on the fifth (5th) Business Day preceding
the date on which the requested Letter of Credit requested is to be issued, or
such shorter notice as may be acceptable to the Issuing Bank and the
Administrative Agent.  Upon receipt of any such Request for Issuance of Letter
of Credit, subject to satisfaction of all conditions precedent thereto as set
forth in Section 3.3 hereof, the Issuing Bank shall process such Request for
Issuance of Letter of Credit and the certificates, documents and other papers
and information delivered to it in connection therewith in accordance with its
customary procedures and shall promptly issue the Letter of Credit requested
thereby.  The Issuing Bank shall furnish a copy of such Letter of Credit (or any
amendment thereto or renewal or extension thereof) to the Borrowers, the
Administrative Agent and each of the Lenders following the issuance thereof.
The Borrower shall pay or reimburse the Issuing Bank for normal and customary
costs and expenses incurred by the Issuing Bank in issuing, effecting payment
under, amending or otherwise administering the Letters of Credit.

          (c) At such time as the Administrative Agent shall be notified by the
Issuing Bank that the beneficiary under any Letter of Credit has drawn on the
same, the Administrative Agent shall promptly notify the Borrowers and each
Lender having a Revolving Loan Commitment, by telephonic notice, followed
promptly by written notice, of the amount of the draw and, in the case of each
such Lender, such Lender's portion of such draw amount as calculated in
accordance with its respective Commitment Ratio under the Revolving Loan
Commitment.

          (d) The Borrowers hereby agree to immediately reimburse the Issuing
Bank for amounts paid by the Issuing Bank in respect of draws under a Letter of
Credit issued at a Borrower's request.  In order to facilitate such repayment,
the Borrowers hereby irrevocably request the Lenders having a Revolving Loan
Commitment, and such Lenders hereby severally agree, on the terms and conditions
of this Agreement (other than as provided in Article 2 hereof with respect to
the amounts of, the timing of requests for, and the repayment of Advances
hereunder and in Article 3 hereof with respect to conditions precedent to
Advances hereunder), with respect to any honoring of any draw under a Letter of
Credit prior to the occurrence of an Event of  Default under Section 8.1(f) or
(g) hereof, to make an Advance (which Advance may be a LIBOR Advance if the
Borrowers so request in a timely manner or may be Converted to a LIBOR Advance
as provided in the Loan Agreement) to the Borrowers on each day on which the

                                     -48-
<PAGE>

Issuing Bank honors a draw is made under any Letter of Credit and in the amount
of such draw, and to pay the proceeds of such Advance directly to the Issuing
Bank to reimburse the Issuing Bank for the amount paid by it upon such draw.
Each Lender having a Revolving Loan Commitment shall pay its share of such
Advance by paying its portion of such Advance to the Administrative Agent in
accordance with Section 2.2(e) hereof and its respective Commitment Ratio under
the Revolving Loan Commitments, without reduction for any set-off or
counterclaim of any nature whatsoever and regardless of whether any Default or
Event of Default (other than with respect to an Event of Default under Section
8.1(f) or (g) hereof) then exists or would be caused thereby. If at any time
that any Letters of Credit are outstanding, any of the events described in
clauses of Section 8.1(f) or (g) hereof shall have occurred and be continuing,
then each Lender having a Revolving Loan Commitment shall, automatically upon
the occurrence of any such event and without any action on the part of the
Issuing Bank, the Borrowers, the Administrative Agent or such Lenders, be deemed
to have purchased an undivided participation in the face amount of all Letters
of Credit then outstanding in an amount equal to such Lender's respective
Commitment Ratio under the Revolving Loan Commitments, and each Lender having a
Revolving Loan Commitment shall, notwithstanding such Event of Default, upon a
drawing being honored under any Letter of Credit, immediately pay to the
Administrative Agent for the account of the Issuing Bank, in immediately
available funds, the amount of such Lender's participation (and the Issuing Bank
shall deliver to such Lender a loan participation certificate dated the date of
the occurrence of such event and in the amount of such Lender's respective
Commitment Ratio under the Revolving Loan Commitments). The disbursement of
funds in connection with a draw under a Letter of Credit pursuant to this
Section 2.14(d) shall be subject to the terms and conditions of Section 2.2(e)
hereof. The obligation of each Lender having a Revolving Loan Commitment to make
payments to the Administrative Agent, for the account of the Issuing Bank, in
accordance with this Section 2.14 shall be absolute and unconditional and no
such Lender shall be relieved of its obligations to make such payments by reason
of noncompliance by any other Person with the terms of the Letter of Credit or
for any other reason. The Administrative Agent shall promptly remit to the
Issuing Bank the amounts so received from the other Lenders. Any overdue amounts
payable by the Lenders having a Revolving Loan Commitment to the Issuing Bank in
respect of a draw under any Letter of Credit shall bear interest, payable on
demand, at the rate on overnight federal funds transactions with members of the
Federal Reserve System arranged by federal funds brokers, as published for such
day by the Federal Reserve Bank of New York.

          (e) The Borrowers agree that any action taken or omitted to be taken
by the Issuing Bank in connection with any Letter of Credit, except for such
actions or omissions as shall constitute gross negligence or willful misconduct
on the part of the Issuing Bank, shall be binding on the Borrowers as between
the Borrowers and the Issuing Bank, and shall not result in any liability of the
Issuing Bank to the Borrowers. The obligation of the Borrowers to reimburse the
Lenders for Advances made to reimburse the Issuing Bank for draws under the
Letter of Credit shall be absolute, unconditional and irrevocable, and shall be
paid strictly in accordance with the terms of this Agreement under all
circumstances whatsoever, including, without limitation, the following
circumstances:

               (i) any lack of validity or enforceability of any Loan Document;

                                     -49-
<PAGE>

               (ii)   any amendment or waiver of or consent to any departure
     from any or all of the Loan Documents;

               (iii)  any improper use which may be made of any Letter of Credit
     or any improper acts or omissions of any beneficiary or transferee of any
     Letter of Credit in connection therewith;

               (iv)   the existence of any claim, set-off, defense or any right
     which the Borrowers may have at any time against any beneficiary or any
     transferee of any Letter of Credit (or Persons for whom any such
     beneficiary or any such transferee may be acting) or any Lender (other than
     the defense of payment to such Lender in accordance with the terms of this
     Agreement) or any other Person, whether in connection with any Letter of
     Credit, any transaction contemplated by any Letter of Credit, this
     Agreement, any other Loan Document, or any unrelated transaction;

               (v)    any statement or any other documents presented under any
     Letter of Credit proving to be insufficient, forged, fraudulent or invalid
     in any respect or any statement therein being untrue or inaccurate in any
     respect whatsoever, provided that the same shall not have resulted from
                         --------
     gross negligence or willful misconduct of the Issuing Bank;

               (vi)   the insolvency of any Person issuing any documents in
     connection with any Letter of Credit;

               (vii)  any breach of any agreement between the Borrowers and any
     beneficiary or transferee of any Letter of Credit, provided that the same
                                                        --------
     shall not have resulted from the gross negligence or willful misconduct of
     the Issuing Bank;

               (viii) any irregularity in the transaction with respect to which
     any Letter of Credit is issued, including any fraud by the beneficiary or
     any transferee of such Letter of Credit, provided that the same shall not
                                              --------
     have resulted from the gross negligence or willful misconduct of the
     Issuing Bank;

               (ix)   any errors, omissions, interruptions or delays in
     transmission or delivery of any messages, by mail, cable, telegraph,
     wireless or otherwise, whether or not they are in code, provided that the
                                                             --------
     same shall not have resulted from the gross negligence or willful
     misconduct of the Issuing Bank;

               (x)    any act, error, neglect or default, omission, insolvency
     or failure of business of any of the correspondents of the Issuing Bank,
     provided that the same shall not have resulted from the gross negligence or
     --------
     willful misconduct of the Issuing Bank;

               (xi)   any other circumstances arising from causes beyond the
     control of the Issuing Bank;

                                     -50-
<PAGE>

               (xii)  payment by the Issuing Bank under any Letter of Credit
     against presentation of a sight draft or a certificate which does not
     comply with the terms of such Letter of Credit, provided that the same
                                                     --------
     shall not have resulted from gross negligence or willful misconduct of the
     Issuing Bank; and

               (xiii) any other circumstance or happening whatsoever, whether
     or not similar to any of the foregoing, provided that the same shall not
                                             --------
     have resulted from the result of gross negligence or willful misconduct of
     the Issuing Bank or any other Lender.

          (f)  If any change in Applicable Law, any change in the interpretation
or administration thereof, or any change in compliance with Applicable Law by
the Issuing Bank or any Lender having a Revolving Loan Commitment as a result of
any official request or directive of any governmental authority, central bank or
comparable agency (whether or not having the force of law) shall (i) impose,
modify or deem applicable any reserve (including, without limitation, any
imposed by the Board of Governors of the Federal Reserve System), special
deposit, capital adequacy, assessment or other requirements or conditions
against Letters of Credit issued by the Issuing Bank or against participations
by any other Lender in the Letters of Credit or (ii) impose on the Issuing Bank
or any other Lender any other condition regarding any Letter of Credit or any
participation therein, and the result of any of the foregoing in the reasonable
determination of the Issuing Bank or such Lender, as the case may be, is to
increase the cost to the Issuing Bank or such Lender of issuing or maintaining
any Letter of Credit or purchasing or maintaining any participation therein, as
the case may be, by an amount (which amount shall be reasonably determined)
deemed by the Issuing Bank or such Lender to be material, and the designation of
a different lending office will not avoid the need for additional compensation
(without creating other unreimbursed costs or disadvantage to such Lender),
then, on request by the Issuing Bank or such Lender, the Borrower shall pay,
within ten (10) days after demand, the Issuing Bank or such Lender, as the case
may be, such additional amount or amounts as the Issuing Bank or such Lender, as
the case may be, so determines will compensate it on an after-tax basis for such
increased costs.  A certificate of the Issuing Bank or such Lender setting forth
the amount, and in reasonable detail the basis for the Issuing Bank or such
Lender's determination of such amount, to be paid to the Issuing Bank or such
Lender by the Borrower as a result of any event referred to in this paragraph
shall, absent manifest error, be conclusive.

          (g)  Each Lender having a Revolving Loan Commitment shall be
responsible for its pro rata share (based on such Lender's respective Commitment
Ratio under the Revolving Loan Commitments) of any and all reasonable out-of-
pocket costs, expenses (including reasonable legal fees) and disbursements which
may be incurred or made by the Issuing Bank in connection with the collection of
any amounts due under, the administration of, or the presentation or enforcement
of any rights conferred by any Letter of Credit, the Borrowers' or any
guarantor's obligations to reimburse or otherwise.  In the event the Borrowers
shall fail to pay such expenses of the Issuing Bank within ten (10) days after
demand for payment by the Issuing Bank, each Lender having a Revolving Loan
Commitment shall thereupon pay to the Issuing Bank its pro rata share (based on
such Lender's respective Commitment Ratio under the Revolving Loan Commitments)
of such expenses within five (5) days from the date of the

                                     -51-
<PAGE>

Issuing Bank's notice to the Lenders having a Revolving Loan Commitment of the
Borrowers' failure to pay; provided, however, that if the Borrowers or any
                           --------  -------
guarantor shall thereafter pay such expense, the Issuing Bank will repay to each
Lender having a Revolving Loan Commitment the amounts received from such Lender
hereunder.

          (h) The Borrowers agree that each Advance by the Lenders having a
Revolving Loan Commitments to reimburse the Issuing Bank for draws under any
Letter of Credit, shall, for all purposes hereunder, be deemed to be an Advance
under the Revolving Loan Commitment to the Borrowers and shall be payable and
bear interest in accordance with all other Revolving Loans to the Borrowers.

          (i) The Borrowers will indemnify and hold harmless the Administrative
Agent, the Issuing Bank and each Lender and each of the foregoing Person's
respective employees, representatives, officers and directors from and against
any and all claims, liabilities, obligations, losses (other than loss of
profits), damages, penalties, actions, judgments, suits, costs, expenses or
disbursements of any kind or nature whatsoever (including reasonable attorneys'
fees, but excluding taxes) which may be imposed on, incurred by or asserted
against the Administrative Agent, the Issuing Bank or any such other Lender in
any way relating to or arising out of the issuance of a Letter of Credit, except
that the Borrowers shall not be liable to the Administrative Agent, the Issuing
Bank or any such Lender for any portion of such claims, liabilities,
obligations, losses, damages, penalties, actions, judgments, suits, costs,
expenses, or disbursements resulting from the gross negligence or willful
misconduct of the Person seeking indemnification as determined by a non-
appealable judicial order.  This Section 2.14(i) shall survive termination of
this Agreement.

     Section 2.15  Incremental Facility Advances.
                   ------------------------------

          (a) Subject to the terms and conditions of this Agreement, the
Borrowers may request the Incremental Facility Commitments on any Business Day;
provided, however, that the Borrowers may not request the Incremental Facility
--------  -------
Commitments, or an Advance thereunder, during the continuance of any Default or
Event of Default, including, without limitation, any Default or Event of Default
that would result after giving effect thereto; and provided, further, that the
                                                   --------  -------
Borrowers may not request Incremental Facility Commitments (each of which
commitments may be from more than one Lender) which exceed $500,000,000.00 in
the aggregate. The sum of the aggregate amount of the Incremental Facility
Commitments and the aggregate amount of outstanding Incremental Facility
Advances shall not exceed $500,000,000.00. The Incremental Facility Maturity
Date shall be no earlier than six (6) calendar months after the Term Loan B
Maturity Date.  The decision of any Lender to make an Incremental Facility
Commitment to the Borrowers shall be at such Lender's sole discretion.  Persons
not then Lenders may be included as Lenders having Incremental Facility
Commitments with the written approval of the Borrowers and the Administrative
Agent (such approval not to be unreasonably withheld, delayed or conditioned).
The Incremental Facility Commitments (i) may be in the form of a revolving or a
term credit facility, and (ii) must be governed by this Agreement and the other
Loan Documents and be on terms and conditions no more restrictive

                                     -52-
<PAGE>

when viewed as a whole than those set forth herein and therein. This Section
2.15 may be amended with the written consent of the Borrowers and the Majority
Lenders.

          (b) Prior to the effectiveness of any Incremental Facility Commitment,
the Borrowers shall (i) deliver to the Administrative Agent and the Lenders a
Notice of Incremental Facility Commitments (which shall set forth the terms and
provisions with respect to, among other things, interest rates, fees and
scheduled amortization with respect to Advances under such Incremental Facility
Commitment) and (ii) provide revised projections to the Administrative Agent and
Lenders, which shall be in form and substance reasonably satisfactory to the
Administrative Agent and which shall demonstrate the Borrowers' ability to
timely repay such Incremental Facility Commitments and any Advances thereunder
and to comply with the covenants contained in Sections 7.8, 7.9, 7.10 and 7.11
hereof.

          (c) No Incremental Facility Commitment shall, by itself, result in any
reduction of the Revolving Loan Commitment or Term Loan A Commitment, or of the
Commitment Ratios with respect thereto, of the Lender making such Incremental
Facility Commitment.

          (d) Advances under the Incremental Facility Commitments shall (i) bear
interest at the Base Rate Basis or the LIBOR Basis or such other reasonable rate
agreed to by the Lenders making such Advances, (ii) subject to Section 2.15(a)
hereof, be repaid as agreed to by the Borrowers and the Lenders making such
Advances, (iii) for all purposes be Loans and Obligations hereunder and under
the Loan Documents, (iv) be represented by Incremental Facility Notes in
substantially the form of Exhibit T attached hereto, and (v) shall rank pari
                          ---------
passu with the other Loans for purposes of Sections 2.9 and 8.2 hereof.

          (e) Advances under the Incremental Facility Commitments shall be
requested by the Borrowers pursuant to a request (which shall be in
substantially the form of a Request for Advance) delivered in the same manner as
a Request for Advance, but shall be funded pro rata only by those Lenders
holding the Incremental Facility Commitments.

                        ARTICLE 3 Conditions Precedent

     Section 3.1  Conditions Precedent to Effectiveness of this Agreement.  The
                  -------------------------------------------------------
effectiveness of this Agreement is subject to the prior or contemporaneous
fulfillment of each of the following conditions:

          (a) the Administrative Agent and the Lenders shall have received each
of the following, each of which shall be in form and substance reasonably
satisfactory to the Administrative Agent and the Lenders:

              (i)  this Agreement duly executed;

              (ii) duly executed Notes;

                                     -53-
<PAGE>

               (iii) duly executed Security Documents;

               (iv)  the loan certificate of AT L.P. dated as of the Agreement
     Date, in substantially the form attached hereto as Exhibit U, including a
                                                        ---------
     certificate of incumbency with respect to each Authorized Signatory of such
     Person, together with the following items: (A) a true, complete and correct
     copy of the Certificate of Formation and Limited Partnership and Agreement
     of Limited Partnership of AT L.P. as in effect on the Agreement Date, (B)
     certificates of good standing for AT L.P. issued by the Secretary of State
     or similar state official for the state of formation of ATS and for each
     state in which AT L.P. is required to qualify to do business and (C) a
     true, complete and correct copy of the corporate resolutions of the general
     partner of AT L.P. authorizing AT L.P. to execute, deliver and perform this
     Agreement and the other Loan Documents;

               (v)   the loan certificate of AT Inc.  dated as of the Agreement
     Date, in substantially the form attached hereto as Exhibit V, including a
                                                        ---------
     certificate of incumbency with respect to each Authorized Signatory of such
     Person, together with the following items: (A) a true, complete and correct
     copy of the Certificate of Incorporation and By-laws of AT Inc. as in
     effect on the Agreement Date, (B) certificates of good standing for AT Inc.
     issued by the Secretary of State or similar state official for the state of
     incorporation of AT Inc. and for each state in which AT Inc. is required to
     qualify to do business, and (C) a true, complete and correct copy of the
     corporate resolutions of AT Inc. authorizing AT Inc. to execute, deliver
     and perform this Agreement and the other Loan Documents;

               (vi)  the loan certificate of ATC Teleports dated as of the
     Agreement Date, in substantially the form attached hereto as Exhibit V,
                                                                  ---------
     including a certificate of incumbency with respect to each Authorized
     Signatory of such Person, together with the following items: (A) a true,
     complete and correct copy of the Certificate of Incorporation and By-laws
     of ATC Teleports as in effect on the Agreement Date, (B) certificates of
     good standing for ATC Teleports issued by the Secretary of State or similar
     state official for the state of incorporation of ATC Teleports and for each
     state in which ATC Teleports is required to qualify to do business, and (C)
     a true, complete and correct copy of the corporate resolutions of ATC
     Teleports authorizing ATC Teleports to execute, deliver and perform this
     Agreement and the other Loan Documents;

               (vii) the loan certificate of the Parent dated as of the
     Agreement Date, in substantially the form attached hereto as Exhibit W,
                                                                  ---------
     including a certificate of incumbency with respect to each Authorized
     Signatory of such Person, together with the following items: (A) a true,
     complete and correct copy of the Certificate of Incorporation and By-laws
     of the Parent as in effect on the Agreement Date, (B) certificates of good
     standing for the Parent issued by the Secretary of State or similar state
     official for the state of incorporation of the Parent and for each state in
     which the Parent is required to qualify to do business, and (C) a true,
     complete and correct copy of the corporate resolutions of the

                                     -54-

<PAGE>

     Parent authorizing the Parent to execute, deliver and perform the Loan
     Documents to which it is a party;

               (viii) the loan certificate of ATC GP dated as of the Agreement
     Date, in substantially the form attached hereto as Exhibit V, including a
                                                        ---------
     certificate of incumbency with respect to each Authorized Signatory of such
     Person, together with the following items: (A) a true, complete and correct
     copy of the Certificate of Incorporation and By-laws of ATC GP as in effect
     on the Agreement Date, (B) certificates of good standing for ATC GP issued
     by the Secretary of State or similar state official for the state of
     incorporation of ATC GP and for each state in which ATC GP is required to
     qualify to do business, and (C) a true, complete and correct copy of the
     corporate resolutions of ATC GP authorizing ATC GP to execute, deliver and
     perform the Loan Documents to which it is a party;

               (ix)   the loan certificate of ATC Holding dated as of the
     Agreement Date, in substantially the form attached hereto as Exhibit V,
                                                                  ---------
     including a certificate of incumbency with respect to each Authorized
     Signatory of such Person, together with the following items: (A) a true,
     complete and correct copy of the Certificate of Incorporation and By-laws
     of ATC Holding as in effect on the Agreement Date, (B) certificates of good
     standing for ATC Holding issued by the Secretary of State or similar state
     official for the state of incorporation of ATC Holding and for each state
     in which ATC Holding is required to qualify to do business, and (C) a true,
     complete and correct copy of the corporate resolutions of ATC Holding
     authorizing ATC Holding to execute, deliver and perform the Loan Documents
     to which it is a party;

               (x)    a loan certificate of each Restricted Subsidiary dated as
     of the Agreement Date, in substantially the form attached hereto as Exhibit
                                                                         -------
     X, including a certificate of incumbency with respect to each Authorized
     -
     Signatory of such Person, together with the following items: (A) a true,
     complete and correct copy of the Articles or Certificate of Incorporation
     or Formation and of the By-laws or Operating or Partnership Agreement of
     such Person as in effect on the Agreement Date, (B) certificates of good
     standing for such Person issued by the Secretary of State or similar state
     official for the state of incorporation or formation of such Person and for
     each state in which such Person is required to qualify to do business, and
     (C) a true, complete and correct copy of the resolutions of such Person (or
     another appropriate Person) authorizing such Person to execute, deliver and
     perform the Loan Documents to which it is a party and (D) a true, complete
     and correct copy of any shareholders' agreements or voting agreements in
     effect with respect to the Ownership Interests of such Person;

               (xi)   copies of insurance binders or certificates covering the
     assets of the Borrowers and the Restricted Subsidiaries, and otherwise
     meeting the requirements of Section 5.5 hereof, together with copies of the
     underlying insurance policies;

                                     -55-
<PAGE>

               (xii)  legal opinion of Sullivan & Worcester LLP, counsel to the
     Borrowers, addressed to each Lender and the Administrative Agent and dated
     as of the Agreement Date;

               (xiii) duly executed Certificate of Financial Condition for the
     Borrowers and the Restricted Subsidiaries on a consolidated and
     consolidating basis, given by the chief financial officer of AT Inc.;

               (xiv)  copies of the most recent quarterly financial statements
     of the Borrowers and the Restricted Subsidiaries, certified by the chief
     financial officer of AT Inc.;

               (xv)   delivery to the Administrative Agent of all possessory
     collateral, including, without limitation, any pledged notes or pledged
     stock;

               (xvi)  certified copies of each of the material documents
     relating to transactions contemplated herein involving AirTouch, AT&T,
     Triton, TV Azteca, 116 Huntington, ICG and Unisite; and

               (xvii) all such other documents as the Administrative Agent may
     reasonably request, certified by an appropriate governmental official or an
     Authorized Signatory if so requested;

          (b)  the Administrative Agent and the Lenders shall have received
evidence satisfactory to them that all Necessary Authorizations, other than
Necessary Authorizations the absence of which could not reasonably be expected
to have, individually or in the aggregate, a Materially Adverse Effect,
including all necessary consents to the closing of this Agreement, have been
obtained or made, are in full force and effect and are not subject to any
pending or, to the Knowledge of the Borrowers, threatened reversal or
cancellation, and the Administrative Agent and the Lenders shall have received a
certificate of an Authorized Signatory so stating;

          (c)  the Borrowers shall certify to the Administrative Agent and the
Lenders that each of the representations and warranties in Article 4 hereof are
true and correct in all material respects as of the Agreement Date, that no
Default or Event of Default then exists or is continuing and that no material
adverse change has occurred in the financial condition, business operations,
prospects or properties of the Borrowers and the Restricted Subsidiaries, on a
consolidated basis, since the most recent fiscal year end and fiscal quarter
end;

          (d)  the Borrowers shall have paid to the Administrative Agent for the
account of each Lender the facility fees set forth in those letter agreements
dated the Agreement Date in favor of each Lender;

          (e)  the Borrowers shall have submitted a Request for Advance
requesting an Advance under the Term Loan B Commitments of an amount equal to
the Available Term Loan B Commitment; and

                                     -56-
<PAGE>

          (f) the Interest Reserve shall have been established on terms and
conditions satisfactory to the Majority Lenders.

     Section 3.2  Conditions Precedent to Each Advance.  The obligation of the
                  ------------------------------------
Lenders to make each Advance on or after the Agreement Date is subject to the
fulfillment of each of the following conditions immediately prior to or
contemporaneously with such Advance:

          (a) all of the representations and warranties of the Borrowers under
this Agreement and the other Loan Documents (including, without limitation, all
representations and warranties with respect to the Restricted Subsidiaries),
which, pursuant to Section 4.2 hereof, are made at and as of the time of such
Advance, shall be true and correct at such time in all material respects, both
before and after giving effect to the application of the proceeds of such
Advance, and after giving effect to any updates to information provided to the
Lenders in accordance with the terms of such representations and warranties, and
no Default or Event of Default hereunder shall then exist or be caused thereby;

          (b) the Administrative Agent shall have received a duly executed
Request for Advance;

          (c) the incumbency of the Authorized Signatories shall be as stated in
the applicable certificate of incumbency contained in the certificates of the
Borrowers delivered pursuant to Section 3.1(a) (iv) and (v) hereof or as
subsequently modified and reflected in a certificate of incumbency delivered to
the Administrative Agent and the Lenders having the applicable Commitment;

          (d) the Administrative Agent and the Lenders having the applicable
Commitment shall have received all such other certificates, reports, statements,
opinions of counsel (if such Advance is in connection with an Acquisition) or
other documents as the Administrative Agent or any Lender having the applicable
Commitment may reasonably request; and

          (e) with respect to any Advance relating to any Acquisition or the
formation of any Restricted Subsidiary which is permitted hereunder, the
Administrative Agent and the Lenders having the applicable Commitment shall have
received such documents and instruments relating to such Acquisition or
formation of a new Restricted Subsidiary as are described in Section 5.13 hereof
or otherwise required herein; and

          (f) with respect to any Advance prior to the Borrowing Base
Termination Date, the Borrowers shall certify to the Administrative Agent and
the Lenders having the applicable Commitment that the Borrowers are in
compliance with the Borrowing Base formula set forth herein after giving effect
to such Advance.

                                     -57-
<PAGE>

     Section 3.3  Conditions Precedent to Issuance of Letters of Credit.  The
                  -----------------------------------------------------
obligation of the Issuing Bank to issue each Letter of Credit hereunder is
subject to the fulfillment of each of the following conditions immediately prior
to or contemporaneously with such issuance:

          (a) all of the representations and warranties of the Borrowers under
this Agreement, which, in accordance with Section 4.2 hereof, are made at and as
of the time of an Advance, shall be true and correct, both before and after
giving effect to the issuance of such Letter of Credit;

          (b) the Administrative Agent shall have received a duly executed
Request for Issuance of Letter of Credit;

          (c) the incumbency of the Authorized Signatories shall be as stated in
the applicable certificate of incumbency contained in the certificate of the
Borrowers delivered pursuant to Section 3.1(a)(iv) and (v) hereof or as
subsequently modified and reflected in a certificate of incumbency delivered to
the Administrative Agent and the Lenders having a Revolving Loan Commitment;

          (d) there shall not exist, on the date of the issuance of such Letter
of Credit and after giving effect thereto, a Default or an Event of Default
hereunder;

          (e) the Administrative Agent, the Issuing Bank and each of the Lenders
having a Revolving Loan Commitment shall have received all such other
certificates, reports, statements, opinions of counsel (if such Letter of Credit
is in connection with an Acquisition) or other documents as any of them may
reasonably request; and

          (f) with respect to any Letter of Credit prior to the Borrowing Base
Termination Date, the Borrowers shall certify to the Administrative Agent and
the Lenders having a Revolving Loan Commitment that the Borrowers are in
compliance with the Borrowing Base formula set forth herein after giving effect
to such Letter of Credit.

                   ARTICLE 4 Representations and Warranties

     Section 4.1  Representations and Warranties.  The Borrowers hereby agree,
                  ------------------------------
represent and warrant, upon the Agreement Date and on the date of each Advance,
in favor of the Administrative Agent and each Lender that:

          (a) Organization; Ownership; Power; Qualification.  AT L.P. is a
              ---------------------------------------------
limited partnership duly organized, validly existing and in good standing under
the laws of the State of Delaware, and each of AT Inc. and ATC Teleports is a
corporation duly organized, validly existing and in good standing under the laws
of the State of Delaware.  Each Borrower has the power and authority to own its
properties and to carry on its business as now being and as proposed hereafter
to be conducted.  Except as set forth on Schedule 3 attached hereto, each
                                         ----------
Restricted Subsidiary is a corporation, limited liability company or limited
partnership duly

                                     -58-
<PAGE>

organized or formed, validly existing and in good standing under the laws of the
state of its formation and has the power and authority to own its properties and
to carry on its business as now being and as proposed hereafter to be conducted.
The Borrowers and the Restricted Subsidiaries are duly qualified, in good
standing and authorized to do business in each jurisdiction in which the
character of their respective properties or the nature of their respective
businesses requires such qualification or authorization, except where failure to
be so qualified, in the aggregate, could not reasonably be expected to have a
Materially Adverse Effect.

          (b) Authorization; Enforceability.  AT L.P. has the partnership power
              -----------------------------
and each of AT Inc. and ATC Teleports has the corporate power and each has taken
all necessary action to authorize it to borrow hereunder, to execute, deliver
and perform this Agreement and each of the other Loan Documents to which it is a
party in accordance with their respective terms, and to consummate the
transactions contemplated hereby and thereby.  This Agreement has been duly
executed and delivered by the Borrowers and is, and each of the other Loan
Documents to which the Borrowers are parties is, a legal, valid and binding
obligation of each Borrower and enforceable against each Borrower in accordance
with its terms, subject, as to enforcement of remedies, to applicable
bankruptcy, insolvency, fraudulent conveyance, reorganization, moratorium and
similar laws affecting creditors' rights and remedies generally, and subject, as
to enforceability, to general principles of equity.

          (c) Subsidiaries: Authorization; Enforceability.  The Restricted
              -------------------------------------------
Subsidiaries and the direct and indirect ownership thereof by AT L.P., AT Inc.
and ATC Teleports as of the Agreement Date are as set forth on Schedule 2
                                                               ----------
attached hereto, and, to the extent such Restricted Subsidiaries are
corporations, AT L.P., AT Inc. and ATC Teleports, as the case may be, have,
subject to the provisions of the Security Documents,  the unrestricted right to
vote the issued and outstanding shares of each directly owned Restricted
Subsidiary shown thereon and such shares of such Restricted Subsidiaries have
been duly authorized and issued and are fully paid and nonassessable.  Each
Restricted Subsidiary that is a corporation has the corporate power and has
taken all necessary corporate action to authorize it to execute, deliver and
perform each of the Loan Documents to which it is a party in accordance with
their respective terms and to consummate the transactions contemplated by this
Agreement and by such Loan Documents.  Each of the Loan Documents to which any
Restricted Subsidiary is party is a legal, valid and binding obligation of such
Restricted Subsidiary enforceable against such Restricted Subsidiary in
accordance with its terms, subject, as to enforcement of remedies, to applicable
bankruptcy, insolvency, fraudulent conveyance, reorganization, moratorium and
similar laws affecting creditors' rights and remedies generally, and subject, as
to enforceability, to general principles of equity.  The ownership interest in
each of the Restricted Subsidiaries represents a direct or indirect controlling
interest by AT L.P., AT Inc. or ATC Teleports of such Restricted Subsidiary for
purposes of directing or causing the direction of the management and policies of
each Restricted Subsidiary.

          (d) Compliance with Other Loan Documents and Contemplated
              -----------------------------------------------------
Transactions.  The execution, delivery and performance, in accordance with their
------------
respective terms, by the Borrowers of this Agreement and the Notes, and by the
Borrowers and the Restricted Subsidiaries of each of the other Loan Documents to
which they are respectively party, and the

                                     -59-
<PAGE>

consummation of the transactions contemplated hereby and thereby, do not and
will not (i) require any consent or approval, governmental or otherwise, not
already obtained, (ii) violate any Applicable Law respecting any Borrower or any
Restricted Subsidiary, (iii) conflict with, result in a breach of, or constitute
a default under the certificate or articles of incorporation or by-laws or
partnership agreements, as the case may be, as amended, of any Borrower or of
any Restricted Subsidiary, or under any material indenture, agreement, or other
instrument, including without limitation the Licenses, to which any Borrower or
any Restricted Subsidiary is a party or by which any of them or their respective
properties may be bound, or (iv) result in or require the creation or imposition
of any Lien upon or with respect to any property now owned or hereafter acquired
by any Borrower or any Restricted Subsidiary, except for Permitted Liens.

          (e) Business.  The Borrowers, together with their Subsidiaries, are
              --------
engaged in the business of owning, constructing, managing, operating, and
investing in communications tower facilities and in the video, voice and data
transmission business.

          (f) Licenses, etc.  The Licenses have been duly issued and are in full
              --------------
force and effect.  The Borrowers and the Restricted Subsidiaries are in
compliance in all material respects with all of the provisions thereof.  The
Borrowers and the Restricted Subsidiaries have secured all Necessary
Authorizations, except for such Necessary Authorizations the failure of which to
secure would not reasonably be expected to have, individually or in the
aggregate, a Materially Adverse Effect, and all such Necessary Authorizations
are in full force and effect.  Neither any License nor any Necessary
Authorization is the subject of any pending or, to the Knowledge of any
Borrower, threatened revocation which, if determined adversely to any Borrower
or any Restricted Subsidiary would not reasonably be expected to have,
individually or in the aggregate, a Materially Adverse Effect.

          (g) Compliance with Law.  The Borrowers and the Restricted
              -------------------
Subsidiaries are in compliance with all Applicable Law, except where the failure
to be in compliance would not individually or in the aggregate have a Materially
Adverse Effect.

          (h) Title to Assets.  As of the Agreement Date, the Borrowers and the
              ---------------
Restricted Subsidiaries have good, legal and marketable title to, or a valid
leasehold interest in, all of their respective assets, except for such
exceptions as would not reasonably be expected to have, individually or in the
aggregate, a Materially Adverse Effect.  None of the properties or assets of any
Borrower or any of the Restricted Subsidiaries is subject to any Liens, except
for Permitted Liens and Liens under the Prior Loan Agreement and related
documents.  Except for financing statements evidencing Permitted Liens, no
financing statement under the Uniform Commercial Code as in effect in any
jurisdiction and no other filing which names any Borrower or any Restricted
Subsidiary as debtor or which covers or purports to cover any of the assets of
any Borrower or any Restricted Subsidiary is currently effective and on file in
any state or other jurisdiction, other than such financing statements, if any,
as to which the obligations secured thereby have been repaid in their entirety,
and no Borrower nor any Restricted Subsidiary has signed any such financing
statement or filing or any security agreement authorizing any secured party
thereunder to file any such financing statement or filing other than the Prior
Loan Agreement and related documents.

                                     -60-
<PAGE>

          (i) Litigation.  As of the Agreement Date, there is no action, suit,
              ----------
proceeding or investigation pending against, or, to the Knowledge of the
Borrowers, threatened against or in any other manner relating adversely to, any
Borrower or any Restricted Subsidiary or any of their respective properties,
including without limitation the Licenses, in any court or before any arbitrator
of any kind or before or by any governmental body (including, without
limitation, the FCC) except as set forth on Schedule 4 attached hereto (as such
                                            ----------
schedule may be updated from time to time).  No such action, suit, proceeding or
investigation (i) calls into question the validity of this Agreement or any
other Loan Document, or (ii) individually or collectively involves the
possibility of any judgment or liability not fully covered by insurance which,
if determined adversely to any Borrower or any Restricted Subsidiary, would have
a Materially Adverse Effect.

          (j) Taxes.  All federal, state and other tax returns of the Borrowers
              -----
and each Restricted Subsidiary required by law to be filed have been duly filed
and all federal, state and other taxes, including, without limitation,
withholding taxes, assessments and other governmental charges or levies required
to be paid by any Borrower or any Restricted Subsidiary or imposed upon any
Borrower or any Restricted Subsidiary or any of their respective properties,
income, profits or assets, which are due and payable, have been paid, except any
such taxes (i) (x) the payment of which any Borrower or any Restricted
Subsidiary is diligently contesting in good faith by appropriate proceedings,
(y) for which adequate reserves have been provided on the books of such Person,
and (z) as to which no Lien other than a Permitted Lien has attached and no
foreclosure, distraint, sale or similar proceedings have been commenced, or (ii)
which may result from audits not yet conducted.  The charges, accruals and
reserves on the books of each Borrower and each of the Restricted Subsidiaries
in respect of taxes are, in the judgment of the Borrowers, adequate.

          (k) Financial Statements.  The Borrowers have furnished or caused to
              --------------------
be furnished to the Administrative Agent and the Lenders as of the Agreement
Date, the audited financial statements for the Parent and its Subsidiaries on a
consolidated basis for the fiscal year ended December 31, 1998, and unaudited
financial statements for the Parent and its Subsidiaries for the fiscal quarter
ended September 30, 1999, all of which have been prepared in accordance with
GAAP and present fairly in all material respects the financial position of the
Borrowers and the Restricted Subsidiaries on a consolidated basis, on and as at
such dates and the results of operations for the periods then ended (subject, in
the case of unaudited financial statements, to normal year-end and audit
adjustments).  None of the Borrowers nor any of the Restricted Subsidiaries has
any material liabilities, contingent or otherwise, other than as disclosed in
the financial statements referred to in the preceding sentence or as set forth
or referred to in this Agreement.

          (l) No Material Adverse Change.  There has occurred no event since
              --------------------------
December 31, 1998 which has or which could reasonably be expected to have a
Materially Adverse Effect.

                                     -61-
<PAGE>

          (m) ERISA. Each Borrower and each Restricted Subsidiary and each of
              -----
their respective Plans are in compliance with ERISA and the Code, except to the
extent that the failure to so comply could not reasonably be expected to have a
Materially Adverse Effect, and none of the Borrowers nor any of their ERISA
Affiliates, including their Subsidiaries, has incurred any accumulated funding
deficiency with respect to any such Plan within the meaning of ERISA or the
Code.  The Borrowers, each of their Restricted Subsidiaries, and each other
ERISA Affiliate have complied in all material respects with all requirements of
ERISA.  No Borrower nor any of its Restricted Subsidiaries has made any promises
of retirement or other benefits to employees, except as set forth in the Plans,
in written agreements with such employees, or in such Person's employee handbook
and memoranda to employees.  No Borrower nor any of its ERISA Affiliates,
including their Subsidiaries, has incurred any material liability to PBGC in
connection with any such Plan.  The assets of each such Plan which is subject to
Title IV of ERISA are sufficient to provide the benefits under such Plan, the
payment of which PBGC would guarantee if such Plan were terminated, and such
assets are also sufficient to provide all other "benefit liabilities" (within
the meaning of Section 4041 of ERISA) due under the Plan upon termination.  No
Reportable Event has occurred and is continuing with respect to any such Plan.
No such Plan or trust created thereunder, or party in interest (as defined in
Section 3(14) of ERISA), or any fiduciary (as defined in Section 3(21) of
ERISA), has engaged in a "prohibited transaction" (as such term is defined in
Section 406 of ERISA or Section 4975 of the Code) which would subject such Plan
or any other Plan of any Borrower or any Restricted Subsidiary, any trust
created thereunder, or any such party in interest or fiduciary, or any party
dealing with any such Plan or any such trust, to the tax or penalty on
"prohibited transactions" imposed by Section 502 of ERISA or Section 4975 of the
Code.  No Borrower nor any of its ERISA Affiliates, including their
Subsidiaries, is or has been obligated to make any payment to a Multiemployer
Plan.

          (n) Compliance with Regulations T, U and X.  No Borrower nor any of
              --------------------------------------
the Restricted Subsidiaries is engaged principally or as one of its important
activities in the business of extending credit for the purpose of purchasing or
carrying, and no Borrower nor any Restricted Subsidiary owns or presently
intends to acquire, any "margin security" or "margin stock" as defined in
Regulations T, U, and X (12 C.F.R. Parts 220, 221 and 224) (the "Regulations")
                                                                 -----------
of the Board of Governors of the Federal Reserve System ("margin stock").  None
                                                          ------------
of the proceeds of the Loans will be used, directly or indirectly, for the
purpose of purchasing or carrying any margin stock or for the purpose of
reducing or retiring any Indebtedness which was originally incurred to purchase
or carry margin stock or for any other purpose which might constitute this
transaction a "purpose credit" within the meaning of the Regulations.  No
Borrower has taken, caused or authorized to be taken, and will not take any
action which might cause this Agreement or the Notes to violate any of the
Regulations or any other regulation of the Board of Governors of the Federal
Reserve System or to violate the Exchange Act, in each case as now in effect or
as the same may hereafter be in effect.  If so requested by the Administrative
Agent, the Borrowers will furnish the Administrative Agent with (i) a statement
or statements in conformity with the requirements of Federal Reserve Form U-I
referred to in Regulation U of the Board of Governors of the Federal Reserve
System and (ii) other documents evidencing its compliance with the margin
regulations, reasonably requested by the Administrative Agent.  Neither the
making of the Loans nor the use of proceeds thereof will violate, or be
inconsistent with, the provisions of any of the Regulations.

                                     -62-
<PAGE>

          (o) Investment Company Act.  No Borrower nor any of the Restricted
              ----------------------
Subsidiaries is required to register under the provisions of the Investment
Company Act of 1940, as amended, and neither the entering into or performance by
the Borrowers and the Restricted Subsidiaries of this Agreement and the Loan
Documents nor the issuance of the Notes violates any provision of such Act or
requires any consent, approval or authorization of, or registration with, the
Securities and Exchange Commission or any other governmental or public body or
authority pursuant to any provisions of such Act.

          (p) Governmental Regulation.  No Borrower nor any of the Restricted
              -----------------------
Subsidiaries is required to obtain any consent, approval, authorization, permit
or license which has not already been obtained from, or effect any filing or
registration which has not already been effected with, any federal, state or
local regulatory authority in connection with the execution and delivery of this
Agreement or any other Loan Document.  No Borrower nor any Restricted Subsidiary
is required to obtain any consent, approval, authorization, permit or license
which has not already been obtained from, or effect any filing or registration
which has not already been effected with, any federal, state or local regulatory
authority in connection with the performance, in accordance with their
respective terms, of this Agreement or any other Loan Document, other than
filing of appropriate Uniform Commercial Code financing statements.

          (q) Absence of Default, Etc.  The Borrowers and the Restricted
              ------------------------
Subsidiaries are in compliance in all respects with all of the provisions of
their respective partnership agreements, Certificates or Articles of
Incorporation and By-Laws, as the case may be, and no event has occurred or
failed to occur (including, without limitation, any matter which could create a
Default hereunder by cross-default) which has not been remedied or waived, the
occurrence or non-occurrence of which constitutes, (i) a Default or (ii) a
material default by any Borrower or any Restricted Subsidiary under any
indenture, agreement or other instrument relating to Indebtedness of such Person
in the amount of $10,000,000.00 or more in the aggregate, any material License,
or any judgment, decree or order to which any Borrower or any Restricted
Subsidiary is a party or by which any Borrower or any Restricted Subsidiary or
any of its respective properties may be bound or affected.

          (r) Accuracy and Completeness of Information.  All information,
              ----------------------------------------
reports, prospectuses and other papers and data relating to the Borrowers or any
Restricted Subsidiary and furnished by or on behalf of the Borrowers or any
Restricted Subsidiary to the Administrative Agent or the Lenders, taken as a
whole, were, at the time furnished, true, complete and correct in all material
respects to the extent necessary to give the Administrative Agent and the
Lenders true and accurate knowledge of the subject matter, and all projections,
consisting of a statement of operating statistics, an income statement summary,
a debt repayment schedule and pro forma compliance calculations (the
"Projections") (i) disclose all assumptions made with respect to costs, general
 -----------
economic conditions, and financial and market conditions formulating the
Projections; (ii) are based on reasonable estimates and assumptions; and (iii)
reflect, as of the date prepared, and continue to reflect, as of the date
hereof, the reasonable estimate of the Borrowers of the results of operations
and other information projected therein for the periods covered thereby.

                                     -63-
<PAGE>

          (s) Agreements with Affiliates.  Except for agreements or arrangements
              --------------------------
with Affiliates wherein the Borrowers or one or more of the Restricted
Subsidiaries provides services to or receives services from such Affiliates for
fair consideration or which are set forth on Schedule 5 attached hereto, no
                                             ----------
Borrower nor any Restricted Subsidiary has (i) any written agreements or binding
arrangements of any kind with any Affiliate or (ii) any management or consulting
agreements of any kind with any Affiliate, other than (x) those among the
Borrowers, the Restricted Subsidiaries (including the Special Purpose
Subsidiaries) and/or the Parent, and (y) employment arrangements with executive
officers, including, without limitation, stock option grants of the Parent.

          (t) Payment of Wages.  Each Borrower and each Restricted Subsidiary is
              ----------------
in compliance with the Fair Labor Standards Act, as amended, in all material
respects, and to the Knowledge of the Borrowers and each Restricted Subsidiary,
such Persons have paid all minimum and overtime wages required by law to be paid
to their respective employees.

          (u) Priority.  The Security Interest is a valid and, upon filing of
              --------
appropriate Uniform Commercial Code financing statements and/or mortgages, will
be a perfected first priority security interest in the Collateral in favor of
the Administrative Agent, for the benefit of itself, the Lenders and the Issuing
Bank, securing, in accordance with the terms of the Security Documents, the
Obligations, and the Collateral is subject to no Liens other than Permitted
Liens.  The Liens created by the Security Documents are enforceable as security
for the Obligations in accordance with their terms with respect to the
Collateral subject, as to enforcement of remedies, to the following
qualifications: (i) an order of specific performance and an injunction are
discretionary remedies and, in particular, may not be available where damages
are considered an adequate remedy at law, and (ii) enforcement may be limited by
bankruptcy, insolvency, liquidation, reorganization, reconstruction and other
similar laws affecting enforcement of creditors' rights generally (insofar as
any such law relates to the bankruptcy, insolvency or similar event of any
Borrower or any of the Restricted Subsidiaries, as the case may be).

          (v) Indebtedness.  Except as shown on the financial statements of the
              ------------
Parent for the fiscal quarter ended September 30, 1999, or as described on
Schedule 6 attached hereto, none of the Parent, any Borrower, nor any of the
----------
Restricted Subsidiaries has outstanding, as of the Agreement Date, and after
giving effect to the initial Advances hereunder on the Agreement Date, any
Indebtedness for Money Borrowed.

          (w) Solvency.  As of the Agreement Date and after giving effect to the
              --------
transactions contemplated by the Loan Documents (i) the property of the
Borrowers, at a fair valuation, will exceed their debt; (ii) the capital of the
Borrowers will not be unreasonably small to conduct their business; (iii) the
Borrowers will not have incurred debts, or have intended to incur debts, beyond
their ability to pay such debts as they mature; and (iv) the present fair
salable value of the assets of the Borrowers will be greater than the amount
that will be required to pay their probable liabilities (including debts) as
they become absolute and matured.  For purposes of this Section, "debt" means
                                                                  ----
any liability on a claim, and "claim" means (i) the right to payment, whether or
                               -----
not such right is reduced to judgment, liquidated, unliquidated, fixed,
contingent,

                                     -64-
<PAGE>

matured, unmatured, undisputed, legal, equitable, secured or unsecured, or (ii)
the right to an equitable remedy for breach of performance if such breach gives
rise to a right to payment, whether or not such right to an equitable remedy is
reduced to judgment, fixed, contingent, matured, unmatured, undisputed, secured
or unsecured.

          (x)  Year 2000 Compliance.
               --------------------

               (i)  The Borrowers developed a plan for becoming Year 2000
     compliant in a timely manner, the implementation of which is on schedule in
     all material respects.  The Borrowers reasonably believe that they will
     become Year 2000 compliant for their operations and those of the Restricted
     Subsidiaries on a timely basis except to the extent that a failure to do so
     could not reasonably be expected to have a Materially Adverse Effect.

               (ii) The Borrowers reasonably believe any suppliers and vendors
     that are material to the operations of the Borrowers or the Restricted
     Subsidiaries will be Year 2000 compliant for their own computer
     applications except to the extent that a failure to do so could not
     reasonably be expected to have a Materially Adverse Effect.

               (iii) The Borrowers will promptly notify the Administrative
     Agent and the Lenders in the event the Borrowers determine that any
     computer application which is material to the operations of the Borrowers,
     the Restricted Subsidiaries or any of their material vendors or suppliers
     will not be fully Year 2000 compliant on a timely basis, except to the
     extent that such failure could not reasonably be expected to have a
     Materially Adverse Effect.

     Section 4.2  Survival of Representations and Warranties, Etc.  All
                  ------------------------------------------------
representations and warranties made under this Agreement and any other Loan
Document shall be deemed to be made, and shall be true and correct in all
material respects, at and as of the Agreement Date and on the date the making of
each Advance except to the extent relating specifically to the Agreement Date.
All representations and warranties made under this Agreement and the other Loan
Documents shall survive, and not be waived by, the execution hereof by the
Lenders and the Administrative Agent, any investigation or inquiry by any Lender
or the Administrative Agent, or the making of any Advance under this Agreement.

                          ARTICLE 5 General Covenants

     So long as any of the Obligations is outstanding and unpaid or the Lenders
have an obligation to fund Advances hereunder or the Issuing Bank has an
obligation to issue Letters of Credit hereunder (in each case, whether or not
the conditions to borrowing or issuing a Letter of Credit, as applicable, have
been or can be fulfilled), and unless the Majority Lenders, or such greater
number of Lenders as may be expressly provided herein, shall otherwise consent
in writing:

                                     -65-
<PAGE>

     Section 5.1  Preservation of Existence and Similar Matters.  Except as
                  ---------------------------------------------
permitted under Section 7.4 hereof, the Borrowers will, and will cause each of
the Restricted Subsidiaries to:

          (a) preserve and maintain its existence, and its material rights,
franchises, licenses and privileges in the state of its incorporation,
including, without limitation, the Licenses and all other Necessary
Authorizations, except where the failure to do so could not reasonably be
expected to have a Materially Adverse Effect; and

          (b) qualify and remain qualified and authorized to do business in each
jurisdiction in which the character of its properties or the nature of its
business requires such qualification or authorization, except for such failure
to so qualify and be so authorized as could not reasonably be expected to have a
Materially Adverse Effect.

     Section 5.2  Business; Compliance with Applicable Law.  The Borrowers will,
                  ----------------------------------------
and will cause each of the Restricted Subsidiaries to, (a) engage in the
business of owning, constructing, managing, operating and investing in
communications tower facilities and related businesses and not engage in any
unrelated activities, and (b) comply in all material respects with the
requirements of all Applicable Law.

     Section 5.3  Maintenance of Properties.  The Borrowers will, and will cause
                  -------------------------
each of the Restricted Subsidiaries to, maintain or cause to be maintained in
the ordinary course of business in good repair, working order and condition
(reasonable wear and tear excepted) all properties used in their respective
businesses (whether owned or held under lease), other than obsolete equipment or
unused assets and from time to time make or cause to be made all needed and
appropriate repairs, renewals, replacements, additions, betterments and
improvements thereto.

     Section 5.4  Accounting Methods and Financial Records.  The Borrowers will,
                  ----------------------------------------
and will cause each of the Restricted Subsidiaries on a consolidated and
consolidating basis to, maintain a system of accounting established and
administered in accordance with GAAP, keep adequate records and books of account
in which complete entries will be made in accordance with GAAP and reflecting
all transactions required to be reflected by GAAP, and keep accurate and
complete records of their respective properties and assets.  The Borrowers and
the Restricted Subsidiaries will maintain a fiscal year ending on December 31st.

     Section 5.5  Insurance.  The Borrowers will, and will cause each of the
                  ---------
Restricted Subsidiaries to:

          (a) maintain insurance including, but not limited to, business
interruption coverage and public liability coverage insurance from responsible
companies in such amounts and against such risks to the Borrowers and each
Restricted Subsidiary as is prudent for similarly situated companies engaged in
the communications tower industry;

          (b) keep their respective assets insured by insurers on terms and in a
manner reasonably acceptable to the Administrative Agent against loss or damage
by fire, theft, burglary, loss in transit, explosions and hazards insured
against by extended coverage, in amounts which

                                     -66-
<PAGE>

are prudent for the communications tower management and operation industry and
reasonably satisfactory to the Administrative Agent, all premiums thereon to be
paid by the Borrowers and the Restricted Subsidiaries; and

             (c) require that each insurance policy provide for at least thirty
(30) days' prior written notice to the Administrative Agent of any termination
of or proposed cancellation or nonrenewal of such policy, and name the
Administrative Agent, on behalf of itself, the Lenders and the Issuing Bank as
additional named lender loss payee and, as appropriate, additional insured, to
the extent of the Obligations.

     Section 5.6 Payment of Taxes and Claims.  The Borrowers will, and will
                 ---------------------------
cause each Restricted Subsidiary to, pay and discharge all taxes, including,
without limitation, withholding taxes, assessments and governmental charges or
levies required to be paid by them or imposed upon them or their income or
profits or upon any properties belonging to them, prior to the date on which
penalties attach thereto, and all lawful claims for labor, materials and
supplies which, if unpaid, might become a Lien or charge upon any of their
properties; provided, however, that no such tax, assessment, charge, levy or
            --------  -------
claim need be paid which is being diligently contested in good faith by
appropriate proceedings and for which adequate reserves shall have been set
aside on the appropriate books, but only so long as such tax, assessment,
charge, levy or claim does not become a Lien or charge other than a Permitted
Lien and no foreclosure, distraint, sale or similar proceedings shall have been
commenced.  The Borrowers will, and will cause each Restricted Subsidiary to,
timely file all information returns required by federal, state or local tax
authorities.

     Section 5.7 Compliance with ERISA.
                 ---------------------

             (a) The Borrowers shall, and shall cause the Restricted
Subsidiaries to, make all contributions to any Employee Pension Plan when such
contributions are due and not incur any "accumulated funding deficiency" within
the meaning of Section 412(a) of the Code, whether or not waived, and will
otherwise comply with the requirements of the Code and ERISA with respect to the
operation of all Plans, except to the extent that the failure to so comply could
not have a Materially Adverse Effect.

             (b) The Borrowers shall, and shall cause the Restricted
Subsidiaries to, comply in all respects with the requirements of ERISA with
respect to any Plans subject to the requirements thereof, except to the extent
that the failure to so comply could not have a Materially Adverse Effect.

             (c) The Borrowers shall furnish to the Administrative Agent (i)
within 30 days after any officer of AT Inc., ATC GP or ATC Teleports obtains
knowledge that a "prohibited transaction" (within the meaning of Section 406 of
ERISA or Section 4975 of the Code) has occurred with respect to any Plan of any
Borrower or their ERISA Affiliates, including the Restricted Subsidiaries, that
any Reportable Event has occurred with respect to any Employee Pension Plan or
that PBGC has instituted or will institute proceedings under Title IV of ERISA
to terminate any Employee Pension Plan or to appoint a trustee to administer any

                                     -67-
<PAGE>

Employee Pension Plan, a statement setting forth the details as to such
prohibited transaction, Reportable Event or termination or appointment
proceedings and the action which it (or any other Employee Pension Plan sponsor
if other than a Borrower) proposes to take with respect thereto, together with a
copy of the notice of such Reportable Event given to PBGC if a copy of such
notice is available to a Borrower, any of the Restricted Subsidiaries or any of
its ERISA Affiliates, (ii) promptly after receipt thereof, a copy of any notice
any Borrower, any of the Restricted Subsidiaries or any of their ERISA
Affiliates or the sponsor of any Plan receives from PBGC or the Internal Revenue
Service or the Department of Labor which sets forth or proposes any action or
determination with respect to such Plan, (iii) promptly after the filing
thereof, any annual report required to be filed pursuant to ERISA in connection
with each Plan maintained by any Borrower or any of its ERISA Affiliates,
including the Restricted Subsidiaries, and (iv) promptly upon the Administrative
Agent's request therefor, such additional information concerning any such Plan
as may be reasonably requested by the Administrative Agent.

          (d) The Borrowers shall promptly notify the Administrative Agent of
any excise taxes which have been assessed or which any Borrower, any of the
Restricted Subsidiaries or any of its ERISA Affiliates has reason to believe may
be assessed against any Borrower, any of the Restricted Subsidiaries or any of
its ERISA Affiliates by the Internal Revenue Service or the Department of Labor
with respect to any Plan of any Borrower or its ERISA Affiliates, including the
Restricted Subsidiaries.

          (e) Within the time required for notice to the PBGC under Section
302(f)(4)(A) of ERISA, the Borrowers will notify the Administrative Agent of any
lien arising under Section 302(f) of ERISA in favor of any Plan of any Borrower
or its ERISA Affiliates, including the Restricted Subsidiaries.

          (f) The Borrowers will not, and will not permit any of the Restricted
Subsidiaries or any of their ERISA Affiliates, to take any of the following
actions or permit any of the following events to occur if such action or event
together with all other such actions or events would subject any Borrower, any
of the Restricted Subsidiaries, or any of its ERISA Affiliates to any tax,
penalty, or other liabilities which could have a Materially Adverse Effect:

              (i)   engage in any transaction in connection with which any
     Borrower, any of the Restricted Subsidiaries or any ERISA Affiliate could
     be subject to either a civil penalty assessed pursuant to Section 502(i) of
     ERISA or a tax imposed by Section 4975 of the Code;

              (ii)  terminate any Employee Pension Plan in a manner, or take any
     other action, which could result in any liability of any Borrower, any of
     the Restricted Subsidiaries or any ERISA Affiliate to the PBGC;

              (iii) fail to make full payment when due of all amounts which,
     under the provisions of any Plan, any Borrower, any of the Restricted
     Subsidiaries or any ERISA Affiliate is required to pay as contributions
     thereto, or permit to exist any

                                     -68-
<PAGE>

     accumulated funding deficiency within the meaning of Section 412(a) of the
     Code, whether or not waived, with respect to any Employee Pension Plan; or

               (iv) permit the present value of all benefit liabilities under
     all Employee Pension Plans which are subject to Title IV of ERISA to exceed
     the present value of the assets of such Plans allocable to such benefit
     liabilities (within the meaning of Section 4041 of ERISA), except as may be
     permitted under actuarial funding standards adopted in accordance with
     Section 412 of the Code.

     Section 5.8  Visits and Inspections.  The Borrowers will, and will cause
                  ----------------------
each Restricted Subsidiary to, permit representatives of the Administrative
Agent and any of the Lenders, upon reasonable notice, to (a) visit and inspect
the properties of the Borrowers or any Restricted Subsidiary during business
hours, (b) inspect and make extracts from and copies of their respective books
and records, and (c) discuss with their respective principal officers their
respective businesses, assets, liabilities, financial positions, results of
operations and business prospects.  The Borrowers and each Restricted Subsidiary
will also permit representatives of the Administrative Agent, any of the Lenders
and the Issuing Bank to discuss with their respective accountants the
businesses, assets, liabilities, financial positions, results of operations and
business prospects of such Person.

     Section 5.9  Payment of Indebtedness; Loans.  Subject to any provisions
                  ------------------------------
herein or in any other Loan Document, the Borrowers will, and will cause each
Restricted Subsidiary to, pay any and all of their respective Indebtedness when
and as it becomes due, other than amounts diligently disputed in good faith and
for which adequate reserves have been set aside in accordance with GAAP.

     Section 5.10 Use of Proceeds.  The Borrowers will use the aggregate
                  ---------------
proceeds of all Advances under the Loans directly or indirectly:

          (a)  to refinance the Indebtedness for Money Borrowed set forth on
Schedule 6 attached hereto;
----------

          (b)  to fund Acquisitions and Investments (including, without
limitation, investments in Unrestricted Subsidiaries) permitted under Section
7.6 hereof;

          (c)  to fund Capital Expenditures; and

          (d)  for working capital needs and other general corporate purposes of
the Borrowers and the Restricted Subsidiaries, including, without limitation,
the fees and expenses incurred in connection with the execution and delivery of
this Agreement, and other costs associated with transactions contemplated by
this Agreement, in each case, which do not otherwise conflict with this Section
5.10.

                                     -69-
<PAGE>

No proceeds of Advances hereunder shall be used for the purchase or carrying or
the extension of credit for the purpose of purchasing or carrying, any margin
stock within the meaning of the Regulations.

     Section 5.11  Indemnity.  The Borrowers jointly and severally agree to
                   ---------
indemnify and hold harmless each Lender, the Administrative Agent, the Issuing
Bank and each of their respective affiliates, employees, representatives,
shareholders, officers and directors (any of the foregoing shall be an
"Indemnitee") from and against any and all claims, liabilities, obligations,
 ----------
losses, damages, actions, reasonable attorneys' fees and expenses (as such fees
and expenses are incurred), penalties, judgments, suits, costs and demands by
any party, including the costs of investigating and defending such claims,
whether or not any Borrower, any Restricted Subsidiary or the Person seeking
indemnification is the prevailing party (a) resulting from any breach or alleged
breach by any Borrower or any Restricted Subsidiary of any representation or
warranty made hereunder or under any Loan Document; or (b) otherwise arising out
of (i) the Commitments or otherwise under this Agreement, any Loan Document or
any transaction contemplated hereby or thereby, including, without limitation,
the use of the proceeds of Loans hereunder in any fashion by any Borrower or the
performance of their respective obligations under the Loan Documents by any
Borrower or any Restricted Subsidiary, (ii) allegations of any participation by
the Lender, the Administrative Agent, the Issuing Bank or any of them, in the
affairs of any Borrower or any of its Subsidiaries, or allegations that any of
them has any joint liability with any Borrower or any of its Restricted
Subsidiaries for any reason, (iii) any claims against the Lenders, the
Administrative Agent, the Issuing Bank or any of them, by any shareholder or
other investor in or lender to any Borrower or any of the Restricted
Subsidiaries, by any brokers or finders or investment advisers or investment
bankers retained by any Borrower or by any other third party, arising out of the
Commitments or otherwise under this Agreement; or (c) in connection with taxes
(not including federal or state income or franchise taxes or other taxes based
solely upon the revenues or income of such Persons), fees, and other charges
payable in connection with the Loans, or the execution, delivery, and
enforcement of this Agreement, the Security Documents, the other Loan Documents,
and any amendments thereto or waivers of any of the provisions thereof, unless
the Person seeking indemnification hereunder is determined in such case to have
acted with gross negligence or willful misconduct, in any case, by a final, non-
appealable judicial order.  The obligations of the Borrowers under this Section
5.11 are in addition to, and shall not otherwise limit, any liabilities which
any Borrower might otherwise have in connection with any warranties or similar
obligations of such Person in any other Loan Document.

     Section 5.12  Interest Rate Hedging.  Within sixty (60) days after the
                   ---------------------
Agreement Date and within forty-five (45) days after each Advance after the
Agreement Date, the Borrowers shall enter into (and shall at all times
thereafter maintain for a period of not less than two (2) years) one or more
Interest Hedge Agreements with respect to the interest obligations on not less
than fifty percent (50%) of the principal amount of the Loans outstanding from
time to time.  Such Interest Hedge Agreements shall provide interest rate
protection in conformity with International Swap Dealers Association standards
and for an average period of at least two (2) years from the date of such
Interest Hedge Agreements or, if earlier, until the Term Loan B Maturity Date on
terms reasonably acceptable to the Administrative Agent, such terms to include

                                     -70-
<PAGE>

consideration of the creditworthiness of the other party to the proposed
Interest Hedge Agreement.  All Obligations of the Borrowers to the
Administrative Agent or any of the Lenders (or any of their Affiliates) pursuant
to any Interest Hedge Agreement and all Liens granted to secure such Obligations
shall rank pari passu with all other Obligations and Liens securing such other
Obligations up to the then effective amount of the Commitments; and any Interest
Hedge Agreement between any Borrower and any other Person shall be unsecured.

     Section 5.13  Covenants Regarding Formation of Restricted Subsidiaries and
                   ------------------------------------------------------------
Acquisitions; Partnership, Subsidiaries.  At the time of (i) any Acquisition
---------------------------------------
permitted hereunder, (ii) the purchase by any Borrower or any of the Restricted
Subsidiaries of any interests in any Restricted Subsidiary or Unrestricted
Subsidiary, or (iii) the formation of any new Restricted Subsidiary or
Unrestricted Subsidiary which is permitted under this Agreement, the Borrowers
will, and will cause the Restricted Subsidiaries, as appropriate, to (a) provide
to the Administrative Agent an executed Subsidiary Security Agreement for any
new Restricted Subsidiary, in substantially the form of Exhibit Q attached
                                                        ---------
hereto, together with appropriate Uniform Commercial Code financing statements,
as well as an executed Subsidiary Guaranty for such new Restricted Subsidiary,
in substantially the form of Exhibit O attached hereto, which shall constitute
                             ---------
both Security Documents and Loan Documents for purposes of this Agreement, as
well as a loan certificate for such new Restricted Subsidiary, substantially in
the form of Exhibit X attached hereto, together with appropriate attachments;
            ---------
(b) pledge to the Administrative Agent all of the stock or partnership interests
(or other instruments or securities evidencing ownership) of such Restricted
Subsidiary or Unrestricted Subsidiary or Person which is acquired or formed,
beneficially owned by any Borrower or any Restricted Subsidiary, as the case may
be, as additional Collateral for the Obligations to be held by the
Administrative Agent in accordance with the terms of the Pledge Agreement or a
new Subsidiary Pledge Agreement in substantially the form of Exhibit P attached
                                                             ---------
hereto, and execute and deliver to the Administrative Agent all such
documentation for such pledge as, in the reasonable opinion of the
Administrative Agent, is appropriate; and (c) with respect to any Acquisition or
Restricted Subsidiary, provide revised financial projections for the remainder
of the fiscal year and for each subsequent year until the Maturity Date which
reflect such Acquisition or formation, certified by the chief financial officer
of AT Inc, together with a statement by such Person that no Default exists or
would be caused by such Acquisition or formation, and all other documentation,
including one or more opinions of counsel, reasonably satisfactory to the
Administrative Agent which in its reasonable opinion is appropriate with respect
to such Acquisition or the formation of such Subsidiary.  Notwithstanding the
foregoing, no Borrower shall be required to pledge any of the stock of or other
ownership interests for any Unrestricted Subsidiary which (x) was not formed or
created in anticipation of such Person's direct or indirect investment therein
(other than to facilitate a transaction of the nature referred to in clause (y)
following) and (y) at the time such stock or ownership interest was acquired by
such Person is subject to a restriction on any such Lien (whether such
restriction is in such Person's formation documents or otherwise), but shall be
required to grant the Administrative Agent (for the benefit of the Lenders) a
Lien upon any right to receive distributions from such Unrestricted Subsidiary.
Any document, agreement or instrument (other than the Projections) executed or
issued pursuant to this Section 5.13 shall be a "Loan Document" for purposes of
this Agreement.  Notwithstanding the foregoing, solely with respect to the
Acquisition of Unisite,  the Borrower shall comply with this Section 5.13 within
a

                                     -71-
<PAGE>

reasonable period of time following such Acquisition not to exceed fifteen (15)
days following the consummation of such Acquisition and the Guaranty of Unisite
shall be limited to the extent necessary to comply with the Unisite Notes.

     Section 5.14  Payment of Wages.  The Borrowers shall, and shall cause each
                   ----------------
Restricted Subsidiary to, at all times comply, in all material respects, with
the material requirements of the Fair Labor Standards Act, as amended,
including, without limitation, the provisions of such Act relating to the
payment of minimum and overtime wages as the same may become due from time to
time.

     Section 5.15  Further Assurances.  The Borrowers will promptly cure, or
                   ------------------
cause to be cured, defects in the creation and issuance of any of the Notes and
the execution and delivery of the Loan Documents (including, without limitation,
this Agreement), resulting from any acts or failure to act by any Borrower or
any of the Restricted Subsidiaries or any employee or officer thereof.  The
Borrowers at their expense will promptly execute and deliver to the
Administrative Agent and the Lenders, or cause to be executed and delivered to
the Administrative Agent and the Lenders, all such other and further documents,
agreements, and instruments in compliance with or accomplishment of the
covenants and agreements in the Loan Documents, including this Agreement, or to
correct any omissions in the Loan Documents, or more fully to state the
obligations set out herein or in any of the Loan Documents, or to obtain any
consents, all as may be necessary or appropriate in connection therewith and as
may be reasonably requested.

     Section 5.16  Special Purpose Subsidiaries.  At the time of (a) any
                   ----------------------------
Acquisition of any Person permitted hereunder, the Borrowers shall use
reasonable efforts (taking into account costs and expenses) to cause each of the
towers, including tower sites and other communications sites, owned by such
Person to be transferred to one or more Special Purpose Subsidiaries and (b) any
other Acquisition permitted hereunder (other than the AT&T Towers acquired in
connection with the "Initial Closing," as such term is defined in that certain
Purchase and Sale Agreement dated as of September 10, 1999 between AT&T Corp.
and the Parent), the Borrowers shall cause the assets acquired to be acquired by
one or more Special Purpose Subsidiaries, in each case, each of which Special
Purpose Subsidiaries shall have as its sole asset or assets the towers, tower
sites and other communications sites and a management and master lease agreement
with the Borrowers and such Restricted Subsidiaries, such that from and after
the date each such Acquisition is consummated neither the Borrowers nor the
Restricted Subsidiaries (other than the Special Purpose Subsidiaries) shall hold
any towers, tower sites and other communications sites that were included as a
part of such Acquisitions (except as noted above with respect to AT&T Towers)
other than through one or more duly created and existing Special Purpose
Subsidiaries.  Notwithstanding any provision in this Agreement or any other Loan
Document to the contrary, the Borrowers shall not permit the Special Purpose
Subsidiaries to have any business activities, operations, liabilities,
Indebtedness, Guaranties or Liens (other than (i) pursuant to a Subsidiary
Guaranty or Subsidiary Security Agreement issued in connection herewith, (ii)
pursuant to any intercompany arrangement, lease or other agreement solely with
the Borrowers or another Restricted Subsidiary or (iii) constituting trade
accounts, assessments, taxes and license fees payable or accrued (other than any
Indebtedness for Money Borrowed) by the Special Purpose Subsidiary in the
ordinary course of its business).

                                     -72-
<PAGE>

                        ARTICLE 6 Information Covenants

     So long as any of the Obligations is outstanding and unpaid or the Lenders
have an obligation to fund Advances hereunder or the Issuing Bank has an
obligation to issue Letters of Credit hereunder (in each case, whether or not
the conditions to borrowing or to issuing a Letter of Credit, as applicable,
have been or can be fulfilled) and unless the Majority Lenders shall otherwise
consent in writing, the Borrowers will furnish or cause to be furnished to each
Lender and the Administrative Agent, at their respective offices:

     Section 6.1  Quarterly Financial Statements and Information.  Within forty-
                  ----------------------------------------------
five (45) days after the last day of each of the first three (3) quarters of
each fiscal year of the Borrowers, the balance sheets of the Borrowers on a
consolidated basis with the Restricted Subsidiaries and a consolidating basis
with their Unrestricted Subsidiaries as at the end of such quarter and as of the
end of the preceding fiscal year, and the related statements of operations and
the related statements of cash flows of the Borrowers on a consolidated basis
with the Restricted Subsidiaries and a consolidating basis with their
Unrestricted Subsidiaries for such quarter and for the elapsed portion of the
year ended with the last day of such quarter, which shall set forth in
comparative form such figures as at the end of and for such quarter and
appropriate prior period and shall be certified by the chief financial officer
of AT Inc. to have been prepared in accordance with GAAP and to present fairly
in all material respects the financial position of the Borrowers on a
consolidated basis with the Restricted Subsidiaries and a consolidating basis
with its Unrestricted Subsidiaries as at the end of such period and the results
of operations for such period, and for the elapsed portion of the year ended
with the last day of such period, subject only to normal year-end and audit
adjustments.

     Section 6.2  Annual Financial Statements and Information.  Within ninety
                  -------------------------------------------
(90) days after the end of each fiscal year of the Borrowers, the audited
consolidated balance sheet of the Borrowers and the Restricted Subsidiaries (and
unaudited consolidating balance sheet of the Borrowers and the Unrestricted
Subsidiaries) as of the end of such fiscal year and the related audited
consolidated and unaudited consolidating statements of operations for such
fiscal year and for the previous fiscal year, the related audited consolidated
statements of cash flow and stockholders' equity for such fiscal year and for
the previous fiscal year, which shall be accompanied by an opinion of Deloitte &
Touche, LLP, or other independent certified public accountants of recognized
national standing reasonably acceptable to the Administrative Agent, which shall
be in scope and substance reasonably satisfactory to the Administrative Agent,
together with a statement of such accountants that in connection with their
audit, nothing came to their attention that caused them to believe that the
Borrowers were not in compliance with the terms, covenants, provisions or
conditions of Sections 7.8, 7.9, 7.10 and 7.11 hereof insofar as they relate to
accounting matters.

     Section 6.3  Performance Certificates.  At the time the financial
                  ------------------------
statements are furnished pursuant to Sections 6.1 and 6.2 hereof, a certificate
of the president or chief financial officer of AT Inc. as to their financial
performance, in substantially the form attached hereto as Exhibit Y:
                                                          ---------

                                     -73-
<PAGE>

          (a) setting forth as and at the end of such quarterly period or fiscal
year, as the case may be, the arithmetical calculations required to establish
(i) any adjustment to the Applicable Margins, as provided for in Section 2.3(f)
hereof, and (ii) whether or not the Borrowers were in compliance with the
requirements of Sections 7.8, 7.9, 7.10 and 7.11 hereof;

          (b) stating that, to the best of his or her knowledge, no Default has
occurred as at the end of such quarterly period or year, as the case may be, or,
if a Default has occurred, disclosing each such Default and its nature, when it
occurred, whether it is continuing and the steps being taken by the Borrowers
with respect to such Default;

          (c) containing a list of all Acquisitions, Investments, Restricted
Payments and dispositions of assets from the Agreement Date through the date of
such certificate together with the total amount for each of the foregoing
categories;

          (d) setting forth the amount of distributions received from
Unrestricted Subsidiaries for such period; and

          (e) setting forth as and at the end of such quarterly period or fiscal
year, as the case may be, the arithmetical calculations demonstrating compliance
with the Borrowing Base.

     Section 6.4  Copies of Other Reports.
                  -----------------------

          (a) Promptly upon receipt thereof, copies of all reports, if any,
submitted to any Borrower by its independent public accountants regarding such
Borrower, including, without limitation, any management report prepared in
connection with the annual audit referred to in Section 6.2 hereof.

          (b) Promptly upon receipt thereof, copies of any material adverse
notice or report regarding any License.

          (c) From time to time and promptly upon each request, such data,
certificates, reports, statements, documents or further information regarding
the business, assets, liabilities, financial position, projections, results of
operations or business prospects of the Borrowers, or any of the Restricted
Subsidiaries, as the Administrative Agent or any Lender may reasonably request.

          (d) Annually, certificates of insurance indicating that the
requirements of Section 5.5 hereof remain satisfied for such fiscal year,
together with copies of any new or replacement insurance policies obtained
during such year.

          (e) Prior to January 31st of each year, the annual budget for the
Borrowers and the Restricted Subsidiaries, including, without limitation,
forecasts of the income statement, the balance sheet, a cash flow statement and
the capital expenditure budget for such year, on a quarter by quarter basis.

                                     -74-
<PAGE>

          (f) Promptly after the sending thereof, copies of all statements,
reports and other information which the Parent sends to public security holders
of the Parent generally or files with the Securities and Exchange Commission or
any national securities exchange.

     Section 6.5  Notice of Litigation and Other Matters.  Notice specifying the
                  --------------------------------------
nature and status of any of the following events, promptly, but in any event not
later than fifteen (15) days after the occurrence of any of the following events
becomes known to any Borrower:

          (a) the commencement of all proceedings and investigations by or
before any governmental body and all actions and proceedings in any court or
before any arbitrator against any Borrower or any Restricted Subsidiary, or, to
the extent known to any Borrower, which could have a Materially Adverse Effect;

          (b) any material adverse change with respect to the business, assets,
liabilities, financial position, results of operations or business prospects of
any Borrower and the Restricted Subsidiaries, taken as a whole, other than
changes in the ordinary course of business which have not had and would not
reasonably be expected to have a Materially Adverse Effect and other than
changes in the industry in which any Borrower or any of the Restricted
Subsidiaries operate which would not reasonably be expected to have a Materially
Adverse Effect;

          (c) any material adverse amendment or change to the projections or
annual budget provided to the Lenders hereunder;

          (d) any Default or the occurrence or non-occurrence of any event (i)
which constitutes, or which with the passage of time or giving of notice or both
would constitute, a default by any Borrower or any of the Restricted
Subsidiaries under any material agreement other than this Agreement and the
other Loan Documents to which any Borrower or any of the Restricted Subsidiaries
is party or by which any of their respective properties may be bound, or (ii)
which could have a Materially Adverse Effect, giving in each case a description
thereof and specifying the action proposed to be taken with respect thereto;

          (e) the occurrence of any Reportable Event or a "prohibited
transaction" (as such term is defined in Section 406 of ERISA or Section 4975 of
the Code) with respect to any Plan of any Borrower or any of its Subsidiaries or
the institution or threatened institution by PBGC of proceedings under ERISA to
terminate or to partially terminate any such Plan or the commencement or
threatened commencement of any litigation regarding any such Plan or naming it
or the trustee of any such Plan with respect to such Plan or any action taken by
any Borrower, any of its Subsidiaries or any ERISA Affiliate of any Borrower to
withdraw or partially withdraw from any Plan or to terminate any Plan; and

          (f) the occurrence of any event subsequent to the Agreement Date
which, if such event had occurred prior to the Agreement Date, would have
constituted an exception to the representation and warranty in Section 4.1(m)
hereof.

                                     -75-
<PAGE>

                         ARTICLE 7 Negative Covenants

     So long as any of the Obligations is outstanding and unpaid or the Lenders
have an obligation to fund Advances hereunder or the Issuing Bank has an
obligation to issue Letters of Credit hereunder (in each case, whether or not
the conditions to borrowing or to issuing a Letter of Credit, as applicable,
have been or can be fulfilled) and unless the Majority Lenders, or such greater
number of Lenders as may be expressly provided herein, shall otherwise give
their prior consent in writing:

     Section 7.1  Indebtedness of the Borrowers and the Restricted Subsidiaries.
                  -------------------------------------------------------------
The Borrowers shall not, and shall not permit any of the Restricted Subsidiaries
to, create, assume, incur or otherwise become or remain obligated in respect of,
or permit to be outstanding, any Indebtedness except:

          (a) the Obligations;

          (b) accounts payable, accrued expenses (including, without limitation,
taxes) and customer advance payments incurred in the ordinary course of
business;

          (c) Indebtedness secured by Permitted Liens;

          (d) obligations under Interest Hedge Agreements with respect to the
Loans;

          (e) Indebtedness of any Borrower or any of the Restricted Subsidiaries
to any Borrower or any other Restricted Subsidiary; provided, however, that the
                                                    --------  -------
corresponding debt instruments are pledged to the Administrative Agent as
security for the Obligations and such Indebtedness is expressly permitted
pursuant to Section 7.5 hereof;

          (f) Indebtedness incurred by any Unrestricted Subsidiary; provided,
                                                                    --------
however, that such Indebtedness is non-recourse to the Parent, any of the
-------
Borrowers or any Restricted Subsidiary and no Lien is placed on the equity
interests of the Parent, any of the Borrowers or any Restricted Subsidiary in
such Unrestricted Subsidiary;

          (g) Capitalized Lease Obligations not to exceed in the aggregate at
any one time outstanding $5,000,000.00;

          (h) Indebtedness of any Borrower or any of the Restricted Subsidiaries
incurred in connection with an Acquisition; provided, however, that (i) such
                                            --------  -------
Indebtedness (A) is owed to the seller thereof or an Affiliate thereof, (B) is
unsecured, (C) has no scheduled payment of principal prior to the full payment
of the Obligations, (D) is subject to terms and conditions and subordination
provisions which are acceptable to the Majority Lenders on the date of
incurrence, (E) when added to all other Indebtedness under this Section 7.1(h)
does not exceed at any time outstanding $30,000,000.00, and (ii) the Borrowers
are, at the time of incurrence of

                                     -76-
<PAGE>

such Indebtedness (and after giving effect thereto), in pro forma compliance
with all of the covenants contained in this Agreement;

             (i)  the Intracoastal Notes;

             (j)  the Unisite Notes; and

             (k)  Indebtedness as of the Agreement Date as set forth on Schedule
                                                                        --------
6 attached hereto.
-
     Section 7.2  Limitation on Liens.  The Borrowers shall not, and shall not
                  -------------------
permit any of the Restricted Subsidiaries to, create, assume, incur or permit to
exist or to be created, assumed, incurred or permitted to exist, directly or
indirectly, any Lien on any of its properties or assets, whether now owned or
hereafter acquired, except for Permitted Liens.

     Section 7.3  Amendment and Waiver.  The Borrowers shall not, and shall not
                  --------------------
permit any of the Restricted Subsidiaries to, enter into any amendment of, or
agree to or accept or consent to any waiver of any of the material provisions of
its Articles or Certificate of Incorporation or partnership agreement, as
appropriate, and any material agreements, instruments or other documents
relating to the transactions contemplated herein involving AirTouch, AT&T,
Triton, TV Azteca, 116 Huntington, ICG and Unisite, in each case, if the effect
thereof would be to materially adversely affect the rights of the Administrative
Agent, the Lenders and the Issuing Bank hereunder or under any Loan Document.

     Section 7.4  Liquidation, Merger or Disposition of Assets.
                  --------------------------------------------

             (a)  Disposition of Assets.  The Borrowers shall not, and shall not
                  ---------------------
permit any of the Restricted Subsidiaries to, at any time sell, lease, abandon,
or otherwise dispose of any assets (other than assets disposed of in the
ordinary course of business) without the prior written consent of the Majority
Lenders; provided, however, that the prior written consent of the Lenders shall
         --------  -------
not be required for (i) the transfer of assets (including cash or cash
equivalents) among the Borrowers and the Restricted Subsidiaries (excluding
Subsidiaries of such Persons described in clause (b) of the definition of
"Subsidiary") or for the transfer of assets (including cash or cash equivalents)
between or among Restricted Subsidiaries (excluding Subsidiaries of such Persons
described in clause (b) of the definition of "Subsidiary") or (ii) the
disposition of assets that contribute, in the aggregate, less than (A) fifteen
percent (15%) of Annualized Operating Cash Flow of the Borrowers and the
Restricted Subsidiaries as of the calendar quarter end immediately preceding
such disposition, and (B) twenty-five percent (25%) of the total Annualized
Operating Cash Flow of the Borrowers and the Restricted Subsidiaries for the
five (5) fiscal year period then ending; provided further, however, that, in
                                         -------- -------  -------
each case, no Default or Event of Default exists and none shall be caused to
occur as a result thereof.  Upon any sale or disposition of a Restricted
Subsidiary permitted hereunder, the Administrative Agent and the Lenders shall,
at Borrowers' expense, take such actions as the Borrowers reasonably request to
cause such Restricted Subsidiary to be released from its obligations under its
Subsidiary Guaranty.

                                     -77-
<PAGE>

          (b)     Liquidation or Merger.  The Borrowers shall not, and shall not
                  ---------------------
permit any of the Restricted Subsidiaries to, at any time, liquidate or dissolve
itself (or suffer any liquidation or dissolution) or otherwise wind up, or enter
into any merger, other than (i) a merger or consolidation among the Borrowers or
among any Borrower and one or more Restricted Subsidiaries, provided, however,
                                                            --------  -------
that any Borrower, as the case may be, is the surviving Person, or (ii) a merger
between or among two (2) or more Restricted Subsidiaries, or (iii) in connection
with an Acquisition permitted hereunder effected by a merger in which any
Borrower, as the case may be, or, in a merger in which none of the Borrowers is
a party, a Restricted Subsidiary is the surviving Person or the surviving Person
becomes a Restricted Subsidiary, or (iv) a merger or consolidation among the
Borrowers, or any Borrower, or any Restricted Subsidiary on the one hand, and
any Person, on the other hand, where the surviving Person (A) is a corporation,
partnership, or limited liability company organized and existing under the laws
of the United States of America, any State thereof or the District of Columbia,
and (B) on the effective date of such merger or consolidation expressly assume,
by supplemental agreement, executed and delivered to the Administrative Agent,
for itself and on behalf of the Lenders and the Issuing Bank, in form and
substance reasonably satisfactory to the Majority Lenders, all the Obligations
of the Borrowers, or any Borrower, or such Restricted Subsidiary, as the case
may be, under the Notes, the Agreement and the other Loan Documents; provided
                                                                     --------
further, however, that, in each case, no Default or Event of Default exists and
-------  -------
none shall be caused to occur as a result thereof.

     Section 7.5  Limitation on Guaranties.  The Borrowers shall not, and shall
                  ------------------------
not permit any of the Restricted Subsidiaries to, at any time Guaranty, assume,
be obligated with respect to, or permit to be outstanding any Guaranty of, any
obligation of any other Person other than (a) a guaranty by endorsement of
negotiable instruments for collection in the ordinary course of business, (b)
obligations under agreements of any Borrower or any of the Restricted
Subsidiaries entered into in connection with Acquisitions permitted under this
Agreement, leases of real property or the acquisition or furnishing of services,
supplies and equipment in the ordinary course of business of any Borrower or any
of the Restricted Subsidiaries, (c) Guaranties of Indebtedness incurred as
permitted pursuant to Section 7.1 hereof (other than Section 7.1(f) and (j)
hereof), or (d) as may be contained in any Loan Document including, without
limitation, any Subsidiary Guaranty.

     Section 7.6  Investments and Acquisitions.  The Borrowers shall not, and
                  ----------------------------
shall not permit any of the Restricted Subsidiaries to, directly or indirectly,
make any loan or advance, or otherwise acquire for consideration evidences of
Indebtedness, capital stock or other securities of any Person or other assets or
property (other than assets or property in the ordinary course of business), or
make any Acquisition or Investment; provided, however, that the Borrowers and
                                    --------  -------
the Restricted Subsidiaries may:

          (a)     directly or through a brokerage account or investment adviser
(i) purchase marketable, direct obligations of the United States of America, its
agencies and instrumentalities maturing within three hundred sixty-five (365)
days of the date of purchase, (ii) purchase commercial paper and other short-
term obligations and business savings accounts issued by corporations, each of
which shall have a combined net worth of at least $100,000,000.00 and each of
which conducts a substantial part of its business in the United States of
America,

                                     -78-
<PAGE>

maturing within two hundred seventy (270) days from the date of the original
issue thereof, and whose issuer is, at the time of purchase, rated "P-2" or
better by Moody's or "A-2" or better by Standard and Poor's; (iii) purchase
repurchase agreements, bankers' acceptances, and domestic and Eurodollar
certificates of deposit maturing within three hundred sixty-five (365) days of
the date of purchase which are issued by, or time deposits maintained with, (A)
a United States national or state bank (or any domestic branch of a foreign
bank) subject to supervision and examination by federal or state banking or
depository institution authorities and having capital, surplus and undivided
profits totaling more than $100,000,000.00 and rated "A" or better by Moody's or
Standard and Poor's, or (B) a Broker/Dealer, and (iv) invest in money market
funds having a rating from Moody's and Standard and Poor's in the highest
investment category granted thereby;

          (b) so long as no Default then exists or would be caused thereby,
establish Unrestricted Subsidiaries and make Investments in such Unrestricted
Subsidiaries (in addition to Investments permitted under Section 7.6(e), (f) and
(g) hereof) of up to, in the aggregate, at any time, the sum of (i)
$50,000,000.00, with proceeds of the Loans and (ii) equity proceeds received
after the Agreement Date and not used to make Acquisitions or Investments
permitted under this Section 7.6 (other than clause (a) hereof) or required to
be used to repay the Obligations;

          (c) so long as no Default then exists or would be caused thereby, and
subject to compliance with Section 5.13 hereof, make Acquisitions; provided,
                                                                   --------
however, that (i) Acquisitions of tower management businesses and tower site
-------
management businesses shall not exceed in the aggregate at any time the sum of
(A) $75,000,000.00 and (B) equity proceeds received after the Agreement Date and
not used to make Acquisitions or Investments under this Section 7.6 (other than
clause (a) hereof) or required to be used to repay the Obligations, and (ii)
Acquisitions of Teleport Businesses (other than the Acquisition of ICG and U.S.
Electrodynamics, Inc.) after the Agreement Date shall not exceed in the
aggregate at any time the sum of (A) $75,000,000.00 and (B) equity proceeds
received after the Agreement Date and not used to make Acquisitions or
Investments permitted under this Section 7.6 (other than clause (a) hereof) or
required to be used to repay the Obligations;

          (d) so long as no Default then exists or would be caused thereby and
subject to compliance with Section 5.13 hereof, make Investments in Persons
primarily engaged in domestic and foreign communications tower and tower related
businesses an aggregate amount not to exceed at any time the sum of (i)
$50,000,000.00 and (ii) equity proceeds received after the Agreement Date and
not used to make Acquisitions or Investments under this Section 7.6 (other than
clause (a) hereof) or required to be used to repay the Obligations, provided
                                                                    --------
that the Parent, any Borrower or any of the Restricted Subsidiaries has executed
a binding acquisition, merger or management agreement with such Person;

          (e) make Investments consisting of the Sconnix Note;

          (f) so long as no Default then exists or would be caused thereby, make
loans to TV Azteca in an aggregate amount not to exceed at any time outstanding,
(i) from the Agreement Date through and including September 30, 2000,
$120,000,000.00, and (ii) at all

                                     -79-
<PAGE>

times thereafter, (A) if, after the Agreement Date but on or prior to September
30, 2000, the Parent receives net cash proceeds from the sale or issuance of its
Capital Stock in an aggregate amount of not less than $60,000,000.00,
$120,000,000.00, or (B) otherwise, $60,000,000.00;

              (g) so long as no Default then exists or would be caused thereby,
make loans to 116 Huntington in an aggregate amount not to exceed at any time
outstanding $55,000,000.00;

              (h) so long as no Default then exists or would be caused thereby,
(i) make loans and advances to employees of the Parent, any Borrower or any of
the Restricted Subsidiaries in the ordinary course of business and (ii) receive
notes from employees in an amount not to exceed $5,000,000.00 in the aggregate
outstanding at any time in connection with the exercise of stock options; and

              (i) make Investments in Galaxy Engineering Services, Inc., a
Delaware corporation, not to exceed $14,500,000.00.

Notwithstanding the limitations set forth elsewhere in this Section 7.6, the
Borrowers and the Restricted Subsidiaries may make Acquisitions and Investments
using Capital Stock of the Parent in lieu of cash (and the value of such Capital
Stock shall be excluded from the monetary limitations set forth above in this
Section 7.6).

     Section 7.7  Restricted Payments.  The Borrowers shall not, and shall not
                  -------------------
permit any of the Restricted Subsidiaries to, directly or indirectly declare or
make any Restricted Payment; provided, however, that so long as no Default or
                             --------  -------
Event of Default hereunder then exists or would be caused thereby, the Borrowers
may make, (a) subject to Section 2.7(b)(iv) hereof, cash distributions in an
aggregate amount for all Borrowers not to exceed fifty percent (50%) of Excess
Cash Flow for the immediately preceding calendar year, on or after April 15/th/
of each calendar year commencing on April 15, 2004; and (b)  distributions to
the Parent to make scheduled principal and interest payments on the Convertible
Notes; provided, however, that all funds in the Interest Reserve shall have been
       --------  -------
used to make all interest payments on the Convertible Notes due on or prior to
October 15, 2001.

     Section 7.8  Leverage Ratio.  (a) As of the end of any calendar quarter,
                  --------------
(b) at the time of any Advance hereunder (after giving effect to such Advance)
and (c) at the time of the issuance of any Letter of Credit (after giving effect
to such Letter of Credit), the Borrowers shall not permit the Leverage Ratio to
exceed the ratios set forth below during the periods indicated:

                                     -80-
<PAGE>

             Period                                  Ratio
             ------                                  -----

     Borrowing Base Termination Date
     through December 31, 2001                    7.75 to 1.00

     January 1, 2002 through
     March 31, 2002                               7.50 to 1.00

     April 1, 2002 through
     June 30, 2002                                7.00 to 1.00

     July 1, 2002 through
     September 30, 2002                           6.50 to 1.00

     October 1, 2002 through
     December 31, 2002                            6.25 to 1.00

     January 1, 2003 through
     June 30, 2003                                5.50 to 1.00

     July 1, 2003 through
     December 31, 2003                            4.50 to 1.00

     January 1, 2004 and thereafter               4.00 to 1.00

     Section 7.9  Interest Coverage Ratio. The Borrowers shall maintain, on a
                  -----------------------
consolidated basis, at all times during the applicable periods set forth below,
a ratio of (a) Annualized Operating Cash Flow for the most recently completed
fiscal quarter to (b) Interest Expense for the four quarters immediately
preceding the calculation date of not less than the ratio set forth below
opposite each such period:

                Period                                           Ratio
                ------                                           -----

     Agreement Date through March 31, 2001                   1.25 to 1.00

     April 1, 2001 through June 30, 2002                     1.50 to 1.00

     July 1, 2002 through September 30, 2002                 1.75 to 1.00

     October 1, 2002 through December 31, 2002               2.00 to 1.00

     January 1, 2003 through December 31, 2003               2.50 to 1.00

     January 1, 2004 and thereafter                          3.00 to 1.00

                                     -81-
<PAGE>

     Section 7.10  Annualized Operating Cash Flow to Pro Forma Debt Service.
                   --------------------------------------------------------
(a) As of the end of any calendar quarter, (b) at the time of any Advance
hereunder (after giving effect to such Advance) and (c) at the time of the
issuance of any Letter of Credit (after giving effect to such Letter of Credit),
the Borrowers, on a consolidated basis, shall not permit the ratio of (i)
Annualized Operating Cash Flow for such fiscal quarter or, if applicable, the
most recently completed fiscal quarter to (ii) Pro Forma Debt Service on such
date to be less than 1.10 to 1.00.

     Section 7.11  Fixed Charge Coverage Ratio.  Commencing December 31, 2003,
                   ---------------------------
(a) as of the end of any calendar quarter, (b) at the time of any Advance
hereunder (after giving effect to such Advance) and (c) at the time of the
issuance of any Letter of Credit (after giving effect to such Letter of Credit),
the Borrowers, on a consolidated basis, shall not permit the ratio of Annualized
Operating Cash Flow for such fiscal quarter or the most recently completed
fiscal quarter to Fixed Charges on such date to be less than or equal to 1.00 to
1.00.

     Section 7.12  Affiliate Transactions.  Except as specifically provided
                   ----------------------
herein (including, without limitation, Sections 7.4, 7.6 and 7.7 hereof), as may
be described on Schedule 5 attached hereto and except for tax sharing agreements
                -----------
among one or more of the Parent and its Subsidiaries which have been consented
to by the Administrative Agent (which consent shall not be unreasonably
withheld, delayed or conditioned), the Borrowers shall not, and shall not permit
any of the Restricted Subsidiaries to, at any time engage in any transaction
with an Affiliate, other than between or among any Borrower and any wholly-owned
Restricted Subsidiary, or make an assignment or other transfer of any of its
properties or assets to any Affiliate, on terms less advantageous to such
Borrower or such Restricted Subsidiary than would be the case if such
transaction had been effected with a non-Affiliate.

     Section 7.13  ERISA Liabilities.  The Borrowers shall not, and shall cause
                   -----------------
each of their ERISA Affiliates not to, (a) permit the assets of any of their
respective Plans to be less than the amount necessary to provide all accrued
benefits under such Plans, or (b) enter into any Multiemployer Plan.

     Section 7.14  Sales and Leasebacks.  The Borrowers will not and will not
                   --------------------
permit any Restricted Subsidiary to enter into, any arrangement, directly or
indirectly, with any third party whereby any Borrower or a Restricted Subsidiary
shall sell or transfer any property, real or personal, whether now owned or
hereafter acquired, and whereby any Borrower or such Restricted Subsidiary shall
then or thereafter rent or lease as lessee such property or any part thereof or
other property which any Borrower or such Restricted Subsidiary intends to use
for substantially the same purpose or purposes as the property sold or
transferred.

                              ARTICLE 8  Default

     Section 8.1   Events of Default.  Each of the following shall constitute an
                   -----------------
Event of Default, whatever the reason for such event and whether it shall be
voluntary or involuntary or be effected by operation of law or pursuant to any
judgment or order of any court or any order, rule or regulation of any
governmental or non-governmental body:

                                     -82-
<PAGE>

          (a) any representation or warranty made under this Agreement shall
prove incorrect or misleading in any material respect when made or deemed to be
made pursuant to Section 4.2 hereof;

          (b) the Borrowers shall default in the payment of (i) any interest
under any of the Notes or fees or other amounts payable to the Lenders and the
Administrative Agent under any of the Loan Documents, or any of them, when due,
and such Default shall not be cured by payment in full within three (3) Business
Days from the due date or (ii) any principal under any of the Notes when due;

          (c) the Borrowers shall default in the performance or observance of
any agreement or covenant contained in Sections 5.2(a), 5.10, 6.5, 7.1, 7.2,
7.4, 7.5, 7.7, 7.8, 7.9, 7.10 and 7.11 hereof;

          (d) the Borrowers shall default in the performance or observance of
any other agreement or covenant contained in this Agreement not specifically
referred to elsewhere in this Section 8.1, and such default shall not be cured
within a period of thirty (30) days (or with respect to Sections 5.3, 5.4, 5.5,
5.6, 5.7, 5.8, 5.9, 5.14, 5.15, 5.16, 6.4, 7.3, 7.12, 7.13 and 7.14 hereof, such
longer period not to exceed sixty (60) days if such default is curable within
such period and the Borrowers are proceeding in good faith with all diligent
efforts to cure such default) from the later of (i) occurrence of such Default
and (ii) the date on which such Default became Known to any of the Borrowers;

          (e) there shall occur any default in the performance or observance of
any agreement or covenant or breach of any representation or warranty contained
in any of the Loan Documents (other than this Agreement or as otherwise provided
in this Section 8.1) by the Borrowers, any of the Restricted Subsidiaries, or
any other obligor thereunder, which shall not be cured within a period of thirty
(30) days (or such longer period not to exceed sixty (60) days if such default
is curable within such period and the Borrowers or such Restricted Subsidiaries
or other obligor are proceeding in good faith with all diligent efforts to cure
such default) from the date on which such default became Known to any of the
Borrowers;

          (f) there shall be entered and remain unstayed a decree or order for
relief in respect of any Borrower, any of the Restricted Subsidiaries or the
Parent under Title 11 of the United States Code, as now constituted or hereafter
amended, or any other applicable Federal or state bankruptcy law or other
similar law, or appointing a receiver, liquidator, assignee, trustee, custodian,
sequestrator or similar official of any Borrower, any of the Restricted
Subsidiaries or the Parent, or of any substantial part of their respective
properties, or ordering the winding-up or liquidation of the affairs of any
Borrower, any of the Restricted Subsidiaries or the Parent; or an involuntary
petition shall be filed against any Borrower, any of the Restricted Subsidiaries
or the Parent and a temporary stay entered, and (i) such petition and stay shall
not be diligently contested, or (ii) any such petition and stay shall continue
undismissed for a period of ninety (90) consecutive days;

                                     -83-
<PAGE>

          (g) any Borrower, any of the Restricted Subsidiaries or the Parent
shall file a petition, answer or consent seeking relief under Title 11 of the
United States Code, as now constituted or hereafter amended, or any other
applicable Federal or state bankruptcy law or other similar law, or any
Borrower, any of the Restricted Subsidiaries or the Parent shall consent to the
institution of proceedings thereunder or to the filing of any such petition or
to the appointment or taking of possession of a receiver, liquidator, assignee,
trustee, custodian, sequestrator or other similar official of any Borrower, any
of the Restricted Subsidiaries or the Parent or of any substantial part of their
respective properties, or any Borrower, any of the Restricted Subsidiaries or
the Parent shall fail generally to pay their respective debts as they become due
or shall be adjudicated insolvent; any Borrower, as the case may be, shall
suspend or discontinue its business, except as permitted by Section 7.4 hereof;
any Borrower, any of the Restricted Subsidiaries or the Parent shall have
concealed, removed any of its property with the intent to hinder or defraud its
creditors or shall have made a fraudulent or preferential transfer under any
applicable fraudulent conveyance or bankruptcy law; or any Borrower, any of the
Restricted Subsidiaries or the Parent shall take any action in furtherance of
any such action;

          (h) a judgment not covered by insurance or indemnification, where the
indemnifying party has agreed to indemnify and is financially able to do so,
shall be entered by any court against any Borrower or any of the Restricted
Subsidiaries for the payment of money which exceeds singly, or in the aggregate
with other such judgments, $10,000,000.00, or a warrant of attachment or
execution or similar process shall be issued or levied against property of any
Borrower or any of the Restricted Subsidiaries which, together with all other
such property of any Borrower or any of the Restricted Subsidiaries subject to
other such process, exceeds in value $10,000,000.00 in the aggregate, and if,
within thirty (30) days after the entry, issue or levy thereof, such judgment,
warrant or process shall not have been paid or discharged or stayed pending
appeal or removed to bond, or if, after the expiration of any such stay, such
judgment, warrant or process, shall not have been paid or discharged or removed
to bond;

          (i) there shall be at any time any "accumulated funding deficiency,"
as defined in ERISA or in Section 412 of the Code, with respect to any Plan
maintained by any Borrower or any of its Restricted Subsidiaries or any ERISA
Affiliate, or to which any Borrower or any of its Restricted Subsidiaries or any
ERISA Affiliate has any liabilities, or any trust created thereunder; or a
trustee shall be appointed by a United States District Court to administer any
such Plan; or PBGC shall institute proceedings to terminate any such Plan; or
any Borrower or any of its Restricted Subsidiaries or any ERISA Affiliate shall
incur any liability to PBGC in connection with the termination of any such Plan;
or any Plan or trust created under any Plan of any Borrower or any of its
Restricted Subsidiaries or any ERISA Affiliate shall engage in a "prohibited
transaction" (as such term is defined in Section 406 of ERISA or Section 4975 of
the Code) which would subject any such Plan, any trust created thereunder, any
trustee or administrator thereof, or any party dealing with any such Plan or
trust to the tax or penalty on "prohibited transactions" imposed by Section 502
of ERISA or Section 4975 of the Code;

          (j) there shall occur (i) any acceleration of the maturity of any
Indebtedness of the Parent, any Borrower or any of the Restricted Subsidiaries
in an aggregate principal amount exceeding $10,000,000.00, or, as a result of a
failure to comply with the terms thereof,

                                     -84-
<PAGE>

such Indebtedness shall otherwise have become due and payable; (ii) any event or
condition the occurrence of which would permit such acceleration of such
Indebtedness, or which, as a result of a failure to comply with the terms
thereof, would make such Indebtedness otherwise due and payable, and which event
or condition has not been cured within any applicable cure period or waived in
writing prior to any declaration of an Event of Default or acceleration of the
Loans hereunder; or (iii) any material default under any Interest Hedge
Agreement which would permit the obligation of any Borrower to make payments to
the counterparty thereunder to be then due and payable;

          (k) the Borrowers and the Restricted Subsidiaries are for any reason
no longer able to operate or manage the related communications tower facilities
or portions thereof and retain the revenue received therefrom, and the overall
effect of which would be to reduce Annualized Operating Cash Flow (determined as
at the last day of the most recently ended fiscal year of the Borrowers) by ten
percent (10%) or more;

          (1) any material Loan Document, or any material provision thereof,
shall at any time and for any reason be declared by a court of competent
jurisdiction to be null and void, or a proceeding shall be commenced by the
Parent, any Borrower or any of the Restricted Subsidiaries or by any
governmental authority having jurisdiction over the Parent, any Borrower or any
of the Restricted Subsidiaries seeking to establish the invalidity or
unenforceability thereof (exclusive of questions of interpretation of any
provision thereof), or the Parent, any Borrower or any of the Restricted
Subsidiaries shall deny that it has any liability or obligation for the payment
of principal or interest purported to be created under any Loan Document;

          (m) any material Security Document shall, for any reason, fail or
cease (except by reason of lapse of time) to create a valid and perfected and
first-priority Lien on or Security Interest in any material portion of the
Collateral purported to be covered thereby;

          (n) there shall occur any Change of Control;

          (o) any Borrower or any of the Restricted Subsidiaries shall be
indicted under the Racketeer Influenced and Corrupt Organizations Act of 1970
(18 U.S.C. (S) 1961 et seq.);
                    -- ---

          (p) the Parent shall incur or permit to remain outstanding any
Indebtedness for Money Borrowed other than (i) the Convertible Notes, (ii)
Indebtedness for Money Borrowed in an aggregate amount not to exceed at any time
outstanding $500,000,000.00, provided that (A) such additional Indebtedness for
                             --------
Money Borrowed (1) is unsecured, (2) has no scheduled payments of principal
prior to the end of the sixth (6/th/) month following the Term Loan B Maturity
Date, (3) has no required cash payments of interest and (4) is otherwise on
terms and conditions reasonably satisfactory to the Majority Lenders and (B) the
proceeds of such additional Indebtedness are contributed as equity to the
Borrowers, (iii) any refinancing of the foregoing in an amount not exceeding the
outstanding principal amount of the Indebtedness being refinanced on the date of
such refinancing and otherwise having terms no less favorable in any material
respect to the Lenders than the Indebtedness being refinanced (iv) that certain
Guaranty Agreement dated December ____, 1999 made by the Parent in favor of TV
Azteca and

                                     -85-
<PAGE>

Television Azteca, S.A. de C.V., a sociedad anonima de capital variable
organized under the laws of Mexico, and (v) that certain Guaranty dated November
30, 1999 made by the Parent in favor of ICG Holdingsb; or

          (q) the Parent shall sell or issue any Capital Stock (other than net
proceeds in an amount not to exceed $2,000,000.00 in the aggregate after the
Agreement Date from the sale of securities in connection with any employee stock
option plan of the Parent or any of its Subsidiaries) or Indebtedness for cash,
the net proceeds of which are not contributed as equity to the Borrowers), in
each case, other than Capital Stock issued in connection with an Acquisition
permitted hereunder.

     Section 8.2  Remedies.
                  --------

          (a) If an Event of Default specified in Section 8.1 (other than an
Event of Default under Section 8.1(f) or (g) hereof) shall have occurred and
shall be continuing, the Administrative Agent, at the request of the Majority
Lenders but subject to Section 9.8 hereof, shall (i) (A) terminate the Revolving
Loan Commitments, Term Loan A Commitments or, if applicable, the Incremental
Facility Commitments, and/or (B) declare the principal of and interest on the
Loans and the Notes and all other amounts owed to the Lenders and the
Administrative Agent under this Agreement, the Notes and any other Loan
Documents to be forthwith due and payable without presentment, demand, protest
or other notice of any kind, all of which are hereby expressly waived, anything
in this Agreement, the Notes or any other Loan Document to the contrary
notwithstanding, and the Revolving Loan Commitments, the Term Loan A Commitments
and, if applicable, the Incremental Facility Commitments shall thereupon
forthwith terminate, and (ii) require the Borrowers to, and the Borrowers shall
thereupon, deposit in an interest bearing account with the Administrative Agent,
as cash collateral for the Obligations, an amount equal to the maximum amount
currently or at any time thereafter available to be drawn on all outstanding
Letters of Credit, and each of the Borrowers hereby pledges to the
Administrative Agent, the Lenders having a Revolving Loan Commitment and the
Issuing Bank and grants to them a security interest in, all such cash as
security for the Obligations.

          (b) Upon the occurrence and continuance of an Event of Default
specified in Section 8.1(f) or (g) hereof, all principal, interest and other
amounts due hereunder and under the Notes, and all other Obligations, shall
thereupon and concurrently therewith become due and payable and the Revolving
Loan Commitments, the Term Loan A Commitments and, if applicable, the
Incremental Facility Commitments shall forthwith terminate and the principal
amount of the Loans outstanding hereunder shall bear interest at the Default
Rate, and the Borrowers shall thereupon forthwith deposit in an interest bearing
account with the Administrative Agent, as cash collateral for the Obligations,
an amount equal to the maximum amount currently or at any time thereafter
available to be drawn on all outstanding Letters of Credit, all without any
action by the Administrative Agent, the Lenders, the Majority Lenders, the
Issuing Bank, or any of them, and without presentment, demand, protest or other
notice of any kind, all of which are expressly waived, anything in this
Agreement or in the other Loan Documents to the contrary notwithstanding.

                                     -86-
<PAGE>

          (c) Upon acceleration of the Notes, as provided in Section 8.2(a) or
(b) hereof, the Administrative Agent, the Issuing Bank and the Lenders shall
have all of the post-default rights granted to them, or any of them, as
applicable under the Loan Documents and under Applicable Law.

          (d) Upon acceleration of the Notes, as provided in Section 8.2(a) or
(b) hereof, the Administrative Agent shall have the right (but not the
obligation) upon the request of the Lenders to operate the communications tower
facilities of the Borrowers and the Restricted Subsidiaries and, pursuant to the
terms and subject to any limitations contained in the Security Documents and,
within guidelines established by the Majority Lenders, to make any and all
payments and expenditures necessary or desirable in connection therewith,
including, without limitation, payment of wages as required under the Fair Labor
Standards Act, as amended, and of any necessary withholding taxes to state or
federal authorities.  In the event the Majority Lenders fail to agree upon the
guidelines referred to in the preceding sentence within six (6) Business Days'
after the Administrative Agent has begun to operate the communications tower
facilities, the Administrative Agent may, after giving three (3) days' prior
written notice to the Lenders of its intention to do so, make such payments and
expenditures as it deems reasonable and advisable in its sole discretion to
maintain the normal day-to-day operation of such communications tower
facilities.  If no proceeding of the types described in Section 8.1(f) or (g)
hereof has been commenced, such payments and expenditures in excess of receipts
shall constitute Advances under the Revolving Loan Commitments, not in excess of
the amount of the Revolving Loan Commitments.  Advances made pursuant to this
Section 8.2(d) shall bear interest as provided in Section 2.3(d) hereof and
shall be payable by the Borrowers on demand.  The making of one or more Advances
under this Section 8.2(d) shall not create any obligation on the part of the
Lenders to make any additional Advances hereunder.  No exercise by the
Administrative Agent of the rights granted to it under this Section 8.2(d) shall
constitute a waiver of any other rights and remedies granted to the
Administrative Agent, the Issuing Bank and the Lenders, or any of them, under
this Agreement or at law.  Each Borrower hereby irrevocably appoints the
Administrative Agent, as agent for the Lenders and the Issuing Bank, the true
and lawful attorney of each of them, in its name and stead and on its behalf, to
execute, receipt for or otherwise act in connection with any and all contracts,
instruments or other documents in connection with the completion and operation
of the communications tower facilities in the exercise of the Administrative
Agent's, the Issuing Bank's and the Lenders' rights under this Section 8.2(d).
Such power of attorney is coupled with an interest and is irrevocable.

          (e) Upon acceleration of the Notes, as provided in Section 8.2(a) or
(b) hereof, the Administrative Agent, upon request of the Majority Lenders,
shall have the right to appoint a receiver for the properties and assets of the
Borrowers and the Restricted Subsidiaries, and each Borrower, for itself and on
behalf of the Restricted Subsidiaries, hereby consents to such rights and such
appointment and hereby waives any objection any Borrower or any Restricted
Subsidiary may have thereto or the right to have a bond or other security posted
by the Administrative Agent, for itself and on behalf of the Lenders and the
Issuing Bank, in connection therewith.

                                     -87-
<PAGE>

          (f) The rights and remedies of the Administrative Agent, the Issuing
Bank and the Lenders hereunder shall be cumulative, and not exclusive.

          (g) In the event that the Administrative Agent establishes a cash
collateral account as contemplated by this Section 8.2, the Administrative Agent
shall invest all funds in such account in such investments as the Administrative
Agent, in its sole and absolute discretion, deems appropriate.  Each of the
Borrowers hereby acknowledges and agrees that any interest earned on such funds
shall be retained by the Administrative Agent as additional collateral for the
Obligations.  Upon satisfaction in full of all Obligations, the Administrative
Agent shall pay any amounts then held in such account to the Borrowers.

     Section 8.3  Payments Subsequent to Declaration of Event of Default.
                  ------------------------------------------------------
Subsequent to the acceleration of the Loans under Section 8.2 hereof, payments
and prepayments under this Agreement made to the Administrative Agent, the
Issuing Bank and the Lenders or otherwise received by any of such Persons (from
realization on Collateral for the Obligations or otherwise) shall be paid over
to the Administrative Agent (if necessary) and distributed by the Administrative
Agent as follows: first, to the Administrative Agent's , Lenders' and Issuing
                  -----
Bank's reasonable costs and expenses, if any, incurred in connection with the
collection of such payment or prepayment, including, without limitation, any
reasonable costs incurred by it in connection with the sale or disposition of
any Collateral for the Obligations and all amounts under Section 11.2(b) hereof;
second, to the Administrative Agent and the Issuing Bank for any fees hereunder
------
or under any of the other Loan Documents then due and payable; third, to the
                                                               -----
Lenders pro rata on the basis of their respective unpaid principal amounts
(except as provided in Section 2.2(e) hereof), to the payment of any unpaid
interest which may have accrued on the Obligations and any fees hereunder or
under any of the other Loan Documents then due and payable; fourth, to the
                                                            ------
Lenders pro rata until all Loans have been paid in full (and, for purposes of
this clause, obligations under Interest Hedge Agreements with the Lenders (or
any of their Affiliates) or any of them shall be paid on a pro rata basis with
the Loans); fifth, to the Lenders pro rata on the basis of their respective
            -----
unpaid amounts, to the payment of any other unpaid Obligations; and sixth, to
                                                                    -----
the Borrowers or as otherwise required by law.

                      ARTICLE 9 The Administrative Agent.

     Section 9.1  Appointment and Authorization.  Each Lender hereby appoints
                  -----------------------------
and authorizes, and hereby agrees that it will require any transferee of any of
its interest in its portion of the Loans and in its Note to appoint and
authorize, the Administrative Agent to take such actions as its agent on its
behalf and to exercise such powers hereunder and under the other Loan Documents
as are delegated by the terms hereof and thereof, together with such powers as
are reasonably incidental thereto.  Neither the Administrative Agent, nor any of
its respective directors, officers, employees or agents, shall be liable for any
action taken or omitted to be taken by it or them hereunder or in connection
herewith, except for its or their own gross negligence or willful misconduct as
determined by a final, non-appealable judicial order of a court of competent
jurisdiction.

                                     -88-
<PAGE>

     Section 9.2  Interest Holders.  The Administrative Agent may treat each
                  ----------------
Lender, or the Person designated in the last notice filed with the
Administrative Agent, as the holder of all of the interests of such Lender in
its portion of the Loans and in its Note until written notice of transfer,
signed by such Lender (or the Person designated in the last notice filed with
the Administrative Agent) and by the Person designated in such written notice of
transfer, in form and substance satisfactory to the Administrative Agent, shall
have been filed with the Administrative Agent.

     Section 9.3  Consultation with Counsel.  The Administrative Agent may
                  -------------------------
consult with Powell, Goldstein, Frazer & Murphy LLP, Atlanta, Georgia, special
counsel to the Administrative Agent, or with other legal counsel selected by it
and shall not be liable for any action taken or suffered by it in good faith in
consultation with the Majority Lenders and in reasonable reliance on such
consultations.

     Section 9.4  Documents.  The Administrative Agent shall be under no duty to
                  ---------
examine, inquire into, or pass upon the validity, effectiveness or genuineness
of this Agreement, any Note, any other Loan Document, or any instrument,
document or communication furnished pursuant hereto or in connection herewith,
and the Administrative Agent shall be entitled to assume that they are valid,
effective and genuine, have been signed or sent by the proper parties and are
what they purport to be.

     Section 9.5  Administrative Agent and Affiliates.  With respect to the
                  -----------------------------------
Commitment and the Loans, the Administrative Agent shall have the same rights
and powers hereunder as any other Lender, and the Administrative Agent and
Affiliates of the Administrative Agent may accept deposits from, lend money to
and generally engage in any kind of business with any Borrower, any of its
Subsidiaries or other Affiliates of, or Persons doing business with, any
Borrower, any of its Subsidiaries or other Affiliates, as if they were not
affiliated with the Administrative Agent and without any obligation to account
therefor.

     Section 9.6  Responsibility of the Administrative Agent and Issuing Bank.
                  -----------------------------------------------------------
The duties and obligations of the Administrative Agent and the Issuing Bank
under this Agreement are only those expressly set forth in this Agreement.  The
Administrative Agent shall be entitled to assume that no Default or Event of
Default has occurred and is continuing unless it has actual knowledge, or has
been notified in writing by any Borrower, of such fact, or has been notified by
a Lender in writing that such Lender considers that a Default or an Event of
Default has occurred and is continuing, and such Lender shall specify in detail
the nature thereof in writing.  The Administrative Agent and the Issuing Bank
shall not be liable hereunder for any action taken or omitted to be taken except
for its own respective gross negligence or willful misconduct as determined by a
final, non-appealable judicial order of a court of competent jurisdiction.  The
Administrative Agent shall provide each Lender and the Issuing Bank with copies
of such documents received from the Borrowers as such Lender and the Issuing
Bank may reasonably request.

                                     -89-
<PAGE>

     Section 9.7  Action by the Administrative Agent and Issuing Bank.
                  ---------------------------------------------------

          (a) The Administrative Agent and the Issuing Bank shall be entitled to
use its discretion with respect to exercising or refraining from exercising any
rights which may be vested in it by, and with respect to taking or refraining
from taking any action or actions which it may be able to take under or in
respect of, this Agreement, unless the Administrative Agent and the Issuing Bank
or the Issuing Bank, as applicable shall have been instructed by the Majority
Lenders (or, where expressly required, all Lenders) to exercise or refrain from
exercising such rights or to take or refrain from taking such action; provided,
                                                                      --------
however, that the Administrative Agent shall not exercise any rights under
-------
Section 8.2(a) hereof without the request of the Majority Lenders (or, where
expressly required, all the Lenders), unless time is of the essence, in which
case, such action can be taken at the request of the Administrative Agent.  The
Administrative Agent shall incur no liability under or in respect of this
Agreement with respect to anything which it may do or refrain from doing in the
reasonable exercise of its judgment or which may seem to it to be necessary or
desirable in the circumstances, except for its gross negligence or willful
misconduct as determined by a final, non-appealable judicial order of a court
having jurisdiction over the subject matter.

          (b) The Administrative Agent and the Issuing Bank shall not be liable
to the Lenders or to any Lender or to any Borrower, any of their Subsidiaries,
the Parent or any other obligor under any Loan Document in acting or refraining
from acting under this Agreement or any other Loan Document in accordance with
the instructions of the Majority Lenders (or, where expressly required, all of
the Lenders), and any action taken or failure to act pursuant to such
instructions shall be binding on all of the Lenders, except for its gross
negligence or willful misconduct as determined by a final, non-appealable
judicial order of a court having jurisdiction over the subject matter.  The
Administrative Agent and the Issuing Bank shall not be obligated to take any
action which is contrary to law or which would in its reasonable opinion subject
it to liability.

     Section 9.8  Notice of Default or Event of Default.  In the event that the
                  -------------------------------------
Administrative Agent, any Lender or the Issuing Bank shall acquire actual
knowledge, or shall have been notified, of any Default or Event of Default, the
Administrative Agent, such Lender or the Issuing Bank shall promptly notify the
Lenders (provided, however, that the failure to give such notice shall not
         --------  -------
result in any liability on the part of such Lender, the Issuing Bank or the
Administrative Agent), and the Administrative Agent shall take such action and
assert such rights under this Agreement and the other Loan Documents as the
Majority Lenders shall request in writing, and the Administrative Agent shall
not be subject to any liability by reason of its acting pursuant to any such
request.  If the Majority Lenders shall fail to request the Administrative Agent
to take action or to assert rights under this Agreement or any other Loan
Documents in respect of any Default or Event of Default within ten (10) days
after their receipt of the notice of any Default or Event of Default from the
Administrative Agent, any Lender or the Issuing Bank, or shall request
inconsistent action with respect to such Default or Event of Default, the
Administrative Agent may, but shall not be required to, take such action and
assert such rights (other than rights under Article 8 hereof) as it deems in its
discretion to be advisable for the protection of the Lenders, except that, if
the Majority Lenders have instructed the

                                     -90-
<PAGE>

Administrative Agent not to take such action or assert such right, in no event
shall the Administrative Agent act contrary to such instructions, unless time is
of the essence, in which case, the Administrative Agent may act in accordance
with its reasonable discretion.

     Section 9.9  Responsibility Disclaimed.  The Administrative Agent shall not
                  -------------------------
be under any liability or responsibility whatsoever as Administrative Agent:

          (a) to any Borrower or any other Person as a consequence of any
failure or delay in performance by, or any breach by, any Lender or Lenders of
any of its or their obligations under this Agreement;

          (b) to any Lender or Lenders as a consequence of any failure or delay
in performance by, or any breach by, (i) the Borrowers of any of their
obligations under this Agreement or the Notes or any other Loan Document, or
(ii) any Restricted Subsidiary or any other obligor under any other Loan
Document;

          (c) to any Lender or Lenders, for any statements, representations or
warranties in this Agreement, or any other document contemplated by this
Agreement or any information provided pursuant to this Agreement, any other Loan
Document, or any other document contemplated by this Agreement, or for the
validity, effectiveness, enforceability or sufficiency of this Agreement, the
Notes, any other Loan Document, or any other document contemplated by this
Agreement; or

          (d) to any Person for any act or omission other than that arising from
gross negligence or willful misconduct of the Administrative Agent as determined
by a final, non-appealable judicial order of a court of competent jurisdiction.

     Section 9.10 Indemnification.  The Lenders agree to indemnify the
                  ---------------
Administrative Agent (to the extent not reimbursed by the Borrowers) pro rata
according to their respective Commitment Ratios, from and against any and all
liabilities, obligations, losses (other than the loss of principal, interest and
fees hereunder in the event of a bankruptcy or out-of-court 'work-out' of the
Loans), damages, penalties, actions, judgments, suits, or reasonable out-of-
pocket costs, expenses (including, without limitation, fees and disbursements of
experts, agents, consultants and counsel), or disbursements of any kind or
nature whatsoever which may be imposed on, incurred by or asserted against the
Administrative Agent in any way relating to or arising out of this Agreement,
any other Loan Document, or any other document contemplated by this Agreement or
any other Loan Document or any action taken or omitted by the Administrative
Agent under this Agreement, any other Loan Document, or any other document
contemplated by this Agreement, except that no Lender shall be liable to the
Administrative Agent for any portion of such liabilities, obligations, losses,
damages, penalties, actions, judgments, suits, or reasonable out-of-pocket
costs, expenses or disbursements resulting from the gross negligence or willful
misconduct of the Administrative Agent as determined by a final, non-appealable
judicial order of a court having jurisdiction over the subject matter.

     Section 9.11 Credit Decision.  Each Lender confirms that:
                  ---------------

                                     -91-
<PAGE>

          (a) in making its decision to enter into this Agreement and to make
its portion of the Loans it has independently taken whatever steps it considers
necessary to evaluate the financial condition and affairs of the Borrowers and
that it has made an independent credit judgment, and that it has not relied upon
the Administrative Agent or information provided by the Administrative Agent
(other than information provided to the Administrative Agent by the Borrowers
and forwarded by the Administrative Agent to the Lenders); and

          (b) so long as any portion of the Loans remains outstanding or such
Lender has an obligation to make its portion of Advances hereunder, it will
continue to make its own independent evaluation of the financial condition and
affairs of the Borrowers.

     Section 9.12  Successor Administrative Agent.  Subject to the appointment
                   ------------------------------
and acceptance of a successor Administrative Agent as provided below, the
Administrative Agent may resign at any time by giving written notice thereof to
the Lenders, the Issuing Bank and the Borrowers and may be removed at any time
for cause by the Majority Lenders.  Upon any such resignation or removal, the
Majority Lenders shall have the right to appoint a successor Administrative
Agent which appointment shall, prior to a Default, be subject to the consent of
the Borrowers, acting reasonably.  If (a) no successor Administrative Agent
shall have been so appointed by the Majority Lenders or (b) if appointed, no
successor Administrative Agent shall have accepted such appointment within
thirty (30) days after the retiring Administrative Agent gave notice of
resignation or the Majority Lenders removed the retiring Administrative Agent,
then the retiring Administrative Agent may, on behalf of the Lenders and the
Issuing Bank, appoint a successor Administrative Agent which shall be any Lender
or a commercial bank organized under the laws of the United States of America or
any political subdivision thereof which has combined capital and reserves in
excess of $250,000,000.00 and which shall be reasonably acceptable to the
Borrowers.  Upon the acceptance of any appointment as Administrative Agent
hereunder by a successor Administrative Agent, such successor Administrative
Agent shall thereupon succeed to and become vested with all the rights, powers,
privileges, duties and obligations of the retiring Administrative Agent and the
retiring Administrative Agent shall be discharged from its duties and
obligations hereunder and under the other Loan Documents.  After any retiring
Administrative Agent's resignation or removal hereunder as Administrative Agent
the provisions of this Article shall continue in effect for its benefit in
respect of any actions taken or omitted to be taken by it while it was acting as
the Administrative Agent.  In the event that the Administrative Agent or any of
its respective Affiliates ceases to be a Lender hereunder, such Person shall
resign its agency hereunder.

     Section 9.13  Delegation of Duties.  The Administrative Agent may execute
                   --------------------
any of its duties under the Loan Documents by or through agents or attorneys
selected by it using reasonable care, and shall be entitled to advice of counsel
concerning all matters pertaining to such duties.

                                     -92-
<PAGE>

                     ARTICLE 10  Changes in Circumstances
                 Affecting LIBOR Advances and Increased Costs

     Section 10.1  LIBOR Basis Determination Inadequate or Unfair.  If with
                   ----------------------------------------------
respect to any proposed LIBOR Advance for any Interest Period, the
Administrative Agent determines after consultation with the Lenders that
deposits in dollars (in the applicable amount) are not being offered to each of
the Lenders in the relevant market for such Interest Period or that adequate and
fair means do not exist for determining the LIBOR Basis, the Administrative
Agent shall forthwith give notice thereof to the Borrowers and the Lenders,
whereupon until the Administrative Agent notifies the Borrowers that the
circumstances giving rise to such situation no longer exist, the obligations of
any affected Lender to make its portion of such LIBOR Advances shall be
suspended.

     Section 10.2  Illegality.  If after the date hereof, the adoption of any
                   ----------
Applicable Law, or any change in any Applicable Law (whether adopted before or
after the Agreement Date), or any change in interpretation or administration
thereof by any governmental authority, central bank or comparable agency charged
with the interpretation or administration thereof, or compliance by any Lender
with any directive (whether or not having the force of law) of any such
authority, central bank or comparable agency, shall make it unlawful or
impossible for any Lender to make, maintain or fund its portion of LIBOR
Advances, such Lender shall so notify the Administrative Agent, and the
Administrative Agent shall forthwith give notice thereof to the other Lenders
and the Borrowers.  Before giving any notice to the Administrative Agent
pursuant to this Section 10.2, such Lender shall designate a different lending
office if such designation will avoid the need for giving such notice and will
not, in the sole reasonable judgment of such Lender, be otherwise materially
disadvantageous to such Lender.  Upon receipt of such notice, notwithstanding
anything contained in Article 2 hereof, the Borrowers shall repay in full the
then outstanding principal amount of such Lender's portion of each affected
LIBOR Advance, together with accrued interest thereon, on either (a) the last
day of the then current Interest Period applicable to such affected LIBOR
Advances if such Lender may lawfully continue to maintain and fund its portion
of such LIBOR Advance to such day or (b) immediately if such Lender may not
lawfully continue to fund and maintain its portion of such affected LIBOR
Advances to such day.  Concurrently with repaying such portion of each affected
LIBOR Advance, the Borrowers may borrow a Base Rate Advance from such Lender,
whether or not it would have been entitled to effect such borrowing, and such
Lender shall make such Advance, if so requested, in an amount such that the
outstanding principal amount of the affected Note held by such Lender shall
equal the outstanding principal amount of such Note immediately prior to such
repayment.

     Section 10.3  Increased Costs.
                   ---------------

          (a) If after the date hereof, the adoption of any Applicable Law, or
any change in any Applicable Law (whether adopted before or after the Agreement
Date), or any interpretation or change in interpretation or administration
thereof by any governmental authority, central bank or comparable agency charged
with the interpretation or administration

                                     -93-
<PAGE>

thereof or compliance by any Lender with any directive (whether or not having
the force of law) of any such authority, central bank or comparable agency:

               (1) shall subject any Lender to any tax, duty or other charge
     with respect to its obligation to make its portion of LIBOR Advances, or
     its portion of other Advances, or shall change the basis of taxation of
     payments to any Lender of the principal of or interest on its portion of
     LIBOR Advances or in respect of any other amounts due under this Agreement,
     or its obligation to make its portion of Advances (except for changes in
     the rate or method of calculation of tax on the revenues or net income of
     such Lender); or

               (2) shall impose, modify or deem applicable any reserve
     (including, without limitation, any imposed by the Board of Governors of
     the Federal Reserve System, but excluding any included in an applicable
     Eurodollar Reserve Percentage), special deposit, capital adequacy,
     assessment or other requirement or condition against assets of, deposits
     with or for the account of, or commitments or credit extended by, any
     Lender or shall impose on any Lender or the London interbank borrowing
     market any other condition affecting its obligation to make its portion of
     such LIBOR Advances or its portion of existing Advances;

and the result of any of the foregoing is to increase the cost to such Lender of
making or maintaining any of its portion of LIBOR Advances, or to reduce the
amount of any sum received or receivable by such Lender under this Agreement or
under its Note with respect thereto, then, within ten (10) days after demand by
such Lender, the Borrowers agree to pay to such Lender such additional amount or
amounts as will compensate such Lender on an after-tax basis for such increased
costs.  All payments made by the Borrowers under this Agreement shall, as set
forth above, be made free and clear of, and without deduction or withholding for
or on account of, any present or future income, stamp, or other taxes, levies,
imposts, duties, charges, fees, deductions or withholdings, now or hereafter
imposed, levied, collected, withheld or assessed by any governmental authority
excluding net income taxes and franchise taxes (imposed in lieu of net income
taxes) imposed on any Lender as a result of present or former connection between
such Person and the jurisdiction of the governmental authority imposing such tax
or any political subdivision or taxing authority thereof or therein (other than
any such connection arising solely from such Person having executed, delivered
or performed its obligations or received a payment under, or enforced, this
Agreement or any other Loan Document).  If any such non-excluded taxes, levies,
imposts, duties, charges, fees, deductions or withholdings (collectively, the
"Non-Excluded Taxes") are required to be withheld from any amounts payable to
 ------------------
any Lender hereunder, the amounts so payable to such Person shall be increased
to the extent necessary to yield to such Person (after payment of all Non-
Excluded Taxes) interest on any such other amounts payable hereunder at the
rates or in the amounts specified in this Agreement; provided, however, that the
                                                     --------  -------
Borrowers shall not be required to increase any such amounts payable to any
Lender that is not organized under the laws of the United States of America or a
state thereof if such Person fails to comply with the requirements of Section
2.13 hereof.  Whenever any Non-Excluded Taxes are payable by the Borrowers, as
promptly as possible thereafter the Borrowers shall send to the Administrative
Agent for its own account or for the account of such Lender, as

                                     -94-
<PAGE>

the case may be, a certified copy of an original official receipt received by
the Borrowers showing payment thereof. If the Borrowers fail to pay any Non-
Excluded Taxes when due to the appropriate taxing authority or fails to remit to
the Administrative Agent the required receipts or other documentary evidence,
the Borrowers shall indemnify the Administrative Agent and the Lenders for any
incremental taxes, interest or penalties that may become payable by the
Administrative Agent or any Lender as result of any such failure. The Borrowers
shall make any payments required pursuant to the immediately preceding sentence
within thirty (30) days after receipt of written demand therefor from the
Administrative Agent or any Lender, as the case may be. The agreements set forth
in this Section 10.3 shall survive the termination of this Agreement and the
payment of the Obligations. Each Lender will promptly notify the Borrowers and
the Administrative Agent of any event of which it has knowledge, occurring after
the date hereof, which will entitle such Lender to compensation pursuant to this
Section 10.3 and will designate a different lending office if such designation
will avoid the need for, or reduce the amount of, such compensation and will
not, in the sole reasonable judgment of such Lender made in good faith, be
otherwise disadvantageous to such Lender. Notwithstanding any provision herein
to the contrary, the Borrowers shall have no obligation to pay to any Lender any
amount which the Borrowers are liable to withhold due to the failure of such
Lender to file any statement of exemption required under the Code.

          (b) Any Lender claiming compensation under this Section 10.3 shall
provide the Borrowers with a written certificate setting forth the additional
amount or amounts to be paid to it hereunder and calculations therefor in
reasonable detail.  Such certificate shall be presumptively correct absent
manifest error.  In determining such amount, such Lender may use any reasonable
averaging and attribution methods.  If any Lender demands compensation under
this Section 10.3, the Borrowers may at any time, upon at least five (5)
Business Days' prior notice to such Lender, prepay in full such Lender's portion
of the then outstanding LIBOR Advances, together with accrued interest and fees
thereon to the date of prepayment, along with any reimbursement required under
Section 2.10 hereof and this Section 10.3.  Concurrently with prepaying such
portion of LIBOR Advances the Borrowers may, whether or not then entitled to
make such borrowing, borrow a Base Rate Advance, or a LIBOR Advance not so
affected, from such Lender, and such Lender shall, if so requested, make such
Advance in an amount such that the outstanding principal amount of the affected
Note or Notes held by such Lender shall equal the outstanding principal amount
of such Note or Notes immediately prior to such prepayment.

     Section 10.4  Effect On Other Advances.  If notice has been given pursuant
                   ------------------------
to Section 10.1, 10.2 or 10.3 hereof suspending the obligation of any Lender to
make its portion of any type of LIBOR Advance, or requiring such Lender's
portion of LIBOR Advances to be repaid or prepaid, then, unless and until such
Lender notifies the Borrowers that the circumstances giving rise to such
repayment no longer apply, all amounts which would otherwise be made by such
Lender as its portion of LIBOR Advances shall be instead as Base Rate Advances,
unless otherwise notified by either of the Borrowers.

                                     -95-
<PAGE>

                           ARTICLE 11  Miscellaneous

     Section 11.1  Notices.
                   -------

          (a)  Except as otherwise expressly provided herein, all notices and
other communications under this Agreement and the other Loan Documents (unless
otherwise specifically stated therein) shall be in writing and shall be deemed
to have been given three (3) Business Days after deposit in the mail, designated
as certified mail, return receipt requested, postage-prepaid, or one (1)
Business Day after being entrusted to a reputable commercial overnight delivery
service for next day delivery, or when sent on a Business Day prior to 5:00 p.m.
(New York, New York time) by telecopy addressed to the party to which such
notice is directed at its address determined as provided in this Section 11.1.
All notices and other communications under this Agreement shall be given to the
parties hereto at the following addresses:

               (i)  If to the Borrowers, to them at:

                    American Towers, Inc.
                    American Tower, L.P.
                    ATC Teleports, Inc.
                    116 Huntington Avenue
                    Boston, Massachusetts 02111
                    Attn: Joseph B. Winn, Chief Financial Officer
                    Telecopy: (617) 375-7575

               with a copy to:

                    Sullivan & Worcester LLP
                    One Post Office Square
                    Boston, Massachusetts 02110
                    Attn: Norman A. Bikales, Esq.
                    Telecopy No.: (617) 338-2880

               (ii) If to the Administrative Agent, to it at:

                    Toronto Dominion (Texas), Inc.
                    909 Fannin Street, Suite 1700
                    Houston, Texas 77010
                    Attention: Agency Department
                    Telecopy No.: (713) 951-9921

                                     -96-
<PAGE>

                with a copy to:

                     TD Securities (USA) Inc.
                     31 West 52nd Street
                     New York, NY 10019-6101
                     Attn: Managing Director, Communications Finance
                     Telecopy No.: (212) 827-7261

               and with a copy to:

                     Powell, Goldstein, Frazer & Murphy LLP
                     Sixteenth Floor
                     191 Peachtree Street, N.E.
                     Atlanta, Georgia 30303
                     Attn: Douglas S. Gosden, Esq.
                     Telecopy No.: (404) 572-6999

               (iii) If to the Lenders, to them at the addresses set forth
     beside their names as set forth in Schedule 7 attached hereto.
                                        ----------

The failure to provide copies shall not affect the validity of the notice given
to the primary recipient.

          (b)  Any party hereto may change the address to which notices shall be
directed under this Section 11.1 by giving ten (10) days' written notice of such
change to the other parties.

     Section 11.2  Expenses.  The Borrowers will promptly pay, or reimburse:
                   --------

          (a)  all reasonable out-of-pocket expenses of the Administrative Agent
in connection with the preparation, negotiation, execution and delivery of this
Agreement and the other Loan Documents, and the transactions contemplated
hereunder and thereunder and the making of the initial Advance hereunder
(whether or not such Advance is made), including, without limitation, the
reasonable fees and disbursements of Powell, Goldstein, Frazer & Murphy LLP,
Atlanta, Georgia, special counsel for the Administrative Agent; and

          (b)  all reasonable out-of-pocket costs and expenses of the
Administrative Agent, the Lenders and the Issuing Bank of enforcement under this
Agreement or the other Loan Documents and all reasonable out-of-pocket costs and
expenses of collection if an Event of Default occurs in the payment of the
Notes, which in each case shall include, without limitation, reasonable fees and
out-of-pocket expenses of counsel for the Administrative Agent, each of the
Lenders and the Issuing Bank.

     Section 11.3  Waivers.  The rights and remedies of the Administrative
                   -------
Agent, the Lenders and the Issuing Bank under this Agreement and the other Loan
Documents shall be

                                     -97-
<PAGE>

cumulative and not exclusive of any rights or remedies which they would
otherwise have. No failure or delay by the Administrative Agent, the Majority
Lenders, the Lenders and the Issuing Bank, or any of them, in exercising any
right, shall operate as a waiver of such right. The Administrative Agent, the
Lenders and the Issuing Bank expressly reserve the right to require strict
compliance with the terms of this Agreement in connection with any future
funding of a Request for Advance. In the event the Lenders decide to fund a
Request for Advance or the Issuing Bank to issue a Letter of Credit at a time
when the Borrowers are not in strict compliance with the terms of this
Agreement, such decision by the Lenders and the Issuing Bank, respectively,
shall not be deemed to constitute an undertaking by the Lenders to fund any
further Request for Advance or the Issuing Bank to issue any Letter of Credit or
preclude the Lenders, the Administrative Agent from exercising any rights
available under the Loan Documents or at law or equity. Any waiver or indulgence
granted by the Administrative Agent, the Lenders, the Majority Lenders and the
Issuing Bank, or any of them, shall not constitute a modification of this
Agreement or any other Loan Document, except to the extent expressly provided in
such waiver or indulgence, or constitute a course of dealing at variance with
the terms of this Agreement or any other Loan Document such as to require
further notice of their intent to require strict adherence to the terms of this
Agreement or any other Loan Document in the future.

     Section 11.4  Set-Off.  In addition to any rights now or hereafter granted
                   -------
under Applicable Law and not by way of limitation of any such rights, upon the
occurrence of an Event of Default and during the continuation thereof, the
Administrative Agent, each of the Lenders and the Issuing Bank are hereby
authorized by the Borrowers at any time or from time to time, without notice to
the Borrowers or to any other Person, any such notice being, to the extent
permitted by Applicable Law, hereby expressly waived, to set off and to
appropriate and to apply any and all deposits (general or special, time or
demand, including, without limitation, Indebtedness evidenced by certificates of
deposit, in each case whether matured or unmatured) and any other Indebtedness
at any time held or owing by any Lender, the Administrative Agent or the Issuing
Bank, to or for the credit or the account of the Borrowers or any Restricted
Subsidiary, against and on account of the obligations and liabilities of the
Borrowers to the Lenders, the Administrative Agent and the Issuing Bank,
including, without limitation, all Obligations and any other claims of any
nature or description arising out of or connected with this Agreement, the Notes
or any other Loan Document, irrespective of whether (a) any Lender, the
Administrative Agent or the Issuing Bank, as applicable shall have made any
demand hereunder or (b) any Lender, Administrative Agent or the Issuing Bank
shall have declared the principal of and interest on the Loans and other amounts
due hereunder to be due and payable as permitted by Section 8.2 hereof and
although such obligations and liabilities or any of them shall be contingent or
unmatured.  Upon direction by the Administrative Agent, with the consent of all
of the Lenders, each Lender or the Issuing Bank holding deposits of any Borrower
or any Restricted Subsidiary shall exercise its set-off rights as so directed;
and, within one (1) Business Day following any such setoff, the Administrative
Agent shall give notice thereof to the Borrowers.  Notwithstanding anything to
the contrary contained in this Section 11.4, no Lender nor the Issuing Bank
shall exercise any right of offset without the prior consent of the Majority
Lenders so long as the Obligations shall be secured by any real property or real
property interest, it being understood and agreed that the provisions of this
sentence are for the exclusive benefit of the Lenders and the Issuing Bank, may
be amended, modified or waived by the Majority Lenders

                                     -98-
<PAGE>

without notice to or consent of the Borrowers or any Subsidiary and shall not
constitute a waiver of any rights against the Borrowers or any Subsidiary or
against any Collateral.

     Section 11.5  Assignment and Participation.
                   ----------------------------

          (a)  No Borrower may assign or transfer any of its rights or
obligations hereunder, under the Notes or under any other Loan Document without
the prior written consent of each Lender and the Issuing Bank.

          (b)  Each Lender may at any time sell assignments or participations of
up to one hundred percent (100%) of its interest hereunder to (A) one (1) or
more wholly-owned Affiliates of such Lender or Approved Funds (provided,
                                                               --------
however, that if such Affiliate is not a financial institution, such Lender
-------
shall be obligated to repurchase such assignment if such Affiliate is unable to
honor its obligations hereunder), (B) any Federal Reserve Bank as collateral
security pursuant to Regulation A of the Board of Governors of the Federal
Reserve System and any Operating Circular issued by such Federal Reserve Bank
(provided, however, that no such assignment shall relieve such Lender from its
 --------  -------
obligations hereunder) or (C) any Lender.

          (c)  Each Lender may at any time sell assignments or participations to
one or more Persons pursuant to which each Lender may assign or participate its
interest under this Agreement and the other Loan Documents, including its
interest in any particular Advance or portion thereof; provided, however, that
                                                       --------  -------
(1) all assignments (other than assignments described in Section 11.5(b) hereof)
shall be in minimum principal amounts of the lesser of (X) $5,000,000.00 (unless
otherwise consented to by the Administrative Agent and, prior to the occurrence
and continuance of an Event of Default, the Borrower), and (Y) the amount
assigned of such Lender's Revolving Loan Commitment, Term Loan A Commitment and,
if applicable, Incremental Facility Commitment (in a single assignment only),
and (2) all assignments and participations (other than assignments and
participations described in Section 11.5(b) hereof) hereunder shall be subject
to the following additional terms and conditions:

               (i)   no assignment shall be sold without the prior consent of
     the Administrative Agent and, prior to the occurrence and continuation of a
     Default or Event of Default, the consent of the Borrowers, in each case,
     which consent shall not be unreasonably withheld, delayed or conditioned;

               (ii)  any Person purchasing a participation or an assignment of
     any portion of the Loans from any Lender shall be required to represent and
     warrant that its purchase shall not constitute a "prohibited transaction"
     (as defined in Section 4.1(m) hereof);

               (iii) the Borrowers, the Lenders, and the Administrative Agent
     agree that assignments permitted hereunder (including the assignment of any
     Advance or portion thereof) may be made with all voting rights, and shall
     be made pursuant to an Assignment and Assumption Agreement substantially in
     the form of Exhibit Z attached hereto, and an administrative fee of
                 ---------
     $3,500.00 shall be payable to the Administrative

                                     -99-
<PAGE>

     Agent either by the assigning Lender or the assignee thereof at the time of
     any assignment under this Section 11.5(c);

               (iv)   no participation agreement shall confer any rights under
     this Agreement or any other Loan Document to any purchaser thereof, or
     relieve any issuing Lender from any of its obligations under this
     Agreement, and all actions hereunder shall be conducted as if no such
     participation had been granted; provided, however, that any participation
                                     --------  -------
     agreement may confer on the participant the right to approve or disapprove
     items requiring unanimous Lender consent pursuant to Section 11.12 hereof;

               (v)    each Lender agrees to provide the Administrative Agent and
     the Borrowers with prompt written notice of any issuance of assignments of
     its interests hereunder;

               (vi)   no assignment, participation or other transfer of any
     rights hereunder or under the Notes shall be effected that would result in
     any interest requiring registration under the Securities Act of 1933, as
     amended, or qualification under any state securities law;

               (vii)  no such assignment may be made to any bank or other
     financial institution (x) with respect to which a receiver or conservator
     (including, without limitation, the Federal Deposit Insurance Corporation,
     the Resolution Trust Company or the Office of Thrift Supervision) has been
     appointed or (y) that is not "adequately capitalized" (as such term is
     defined in Section 131(b)(1)(B) of the Federal Deposit Insurance
     Corporation Improvement Act as in effect on the Agreement Date); and

               (viii) if applicable, each Lender shall, and shall cause each of
     its assignees to, provide to the Administrative Agent on or prior to the
     effective date of any assignment an appropriate Internal Revenue Service
     form as required by Applicable Law supporting such Lender's or assignee's
     position that no withholding by any Borrower or the Administrative Agent
     for United States income tax payable by such Lender or assignee in respect
     of amounts received by it hereunder is required.  For purposes of this
     Agreement, an appropriate Internal Revenue Service form shall mean Form
     1001 (Ownership Exemption or Reduced Rate Certificate of the United States
     Department of Treasury), or Form 4224 (Exemption from Withholding of Tax on
     Income Effectively Connected with the Conduct of a Trade or Business in the
     United States) or Form W-8, or any successor or related forms adopted by
     the relevant United States taxing authorities.

          (d)  Except as specifically set forth in Section 11.5(b) or (c)
hereof, nothing in this Agreement or the Notes, expressed or implied, is
intended to or shall confer on any Person other than the respective parties
hereto and thereto and their successors and assignees permitted hereunder and
thereunder any benefit or any legal or equitable right, remedy or other claim
under this Agreement or the Notes.

                                     -100-
<PAGE>

          (e) In the case of any participation, all amounts payable by the
Borrowers under the Loan Documents shall be calculated and made in the manner
and to the parties hereto as if no such participation had been sold.

          (f) The provisions of this Section 11.5 shall not apply to any
purchase of participations among the Lenders pursuant to Section 2.11 hereof.

          (g) The Administrative Agent, acting, for this purpose only, as agent
of the Borrowers shall maintain, at no extra charge to the Borrowers, a register
(the "Register") at the address to which notices to the Administrative Agent are
      --------
to be sent under Section 11.1 hereof on which Register the Administrative Agent
shall enter the name, address and taxpayer identification number (if provided)
of the registered owner of the Loans evidenced by a Registered Note or, upon the
request of the registered owner, for which a Registered Note has been requested.
A Registered Note and the Loans evidenced thereby may be assigned or otherwise
transferred in whole or in part only by registration of such assignment or
transfer of such Registered Note and the Loans evidenced thereby on the
Register.  Any assignment or transfer of all or part of such Loans and the
Registered Note evidencing the same shall be registered on the Register only
upon compliance with the other provisions of this Section 11.5 and surrender for
registration of assignment or transfer of the Registered Note evidencing such
Loans, duly endorsed by (or accompanied by a written instrument of assignment or
transfer duly executed by) the Registered Noteholder thereof, and thereupon one
or more new Registered Notes in the same aggregate principal amount shall be
issued to the designated assignee(s) or transferee(s) and, if less than the
aggregate principal amount of such Registered Notes is thereby transferred, the
assignor or transferor.  Prior to the due presentment for registration of
transfer of any Registered Note, the Borrowers and the Administrative Agent
shall treat the Person in whose name such Loans and the Registered Note
evidencing the same is registered as the owner thereof for the purpose of
receiving all payments thereon and for all other purposes, notwithstanding any
notice to the contrary.

          (h) The Register shall be available for inspection by the Borrowers
and any Lender at any reasonable time during the Administrative Agent's regular
business hours upon reasonable prior notice.

          (i) Notwithstanding any other provision in this Agreement, any Lender
that is a fund that invests in bank loans may, without the consent of the
Administrative Agent or the Borrowers, pledge all or any portion of its rights
under, and interest in, this Agreement and the Notes to any trustee or to any
other representative of holders of obligations owed or securities issued, by
such fund as security for such obligations or securities; provided, however,
                                                          --------  -------
that any transfer to any Person upon the enforcement of such pledge or security
interest may only be made subject to the assignment provisions of this Section
11.5.

          (j) Notwithstanding anything to the contrary contained herein, any
Lender (a "Granting Lender") may grant to a special purpose funding vehicle (an
           ---------------
"SPC") sponsored by such Granting Lender, identified as such in writing from
 ---
time to time by the Granting Lender to the Administrative Agent and the
Borrowers, the option to provide to the Borrowers all or any

                                     -101-
<PAGE>

part of any Advance that such Granting Lender would otherwise be obligated to
make to the Borrowers pursuant to this Agreement; provided that (i) nothing
                                                  -------- ----
herein shall constitute a commitment by any SPC to make any Advance, (ii) if an
SPC elects not to exercise such option or otherwise fails to provide all or any
part of such Advance, the Granting Lender shall be obligated to make such
Advance pursuant to the terms hereof. The Loans by an SPC hereunder shall be
Loans under and pursuant to the Revolving Loan Commitment, Term Loan A
Commitment, Term Loan B Commitment and/or, if applicable, Incremental Facility
Commitment of the Granting Lender to the same extent, and as if, such Loans were
made by such Granting Lender. Each party hereto hereby agrees that no SPC shall
be liable for any indemnity or similar payment obligation under this Agreement
(all liability for which shall remain with the Granting Lender). In furtherance
of the foregoing, each party hereto hereby agrees (which agreement shall survive
the termination of this Agreement) that, prior to the date that is one year and
one day after the payment in full of all outstanding commercial paper or other
senior indebtedness of any SPC, it, solely in its capacity as a party hereto and
to any other Loan Document, will not institute against, or join any other person
in instituting against, such SPC any bankruptcy, reorganization, arrangement,
insolvency or liquidation proceedings under the laws of the United States or any
State thereof. In addition, notwithstanding anything to the contrary contained
in this Section 11.5, any SPC may (i) with notice to, but without the prior
written consent of, the Borrowers and the Administrative Agent and without
paying any processing fee therefor, assign all or a portion of its interests in
any Advances to the Granting Lender or to any financial institutions (consented
to by the Borrowers and the Administrative Agent) providing liquidity and/or
credit support to or for the account of such SPC to support the funding or
maintenance of Advances and (ii) disclose on a confidential basis any non-public
information relating to its Advances to any rating agency, commercial paper
dealer or provider of any surety, guarantee or credit or liquidity enhancement
to such SPC. This Section 11.5(j) may not be amended without the written consent
of any SPC which has been designated in writing as provided in the first
sentence hereof and holds any outstanding Loans. The designation by a Granting
Lender of an SPC to fund Advances (i) shall be deemed to be a representation,
warranty, covenant and agreement by such Granting Lender to the Borrowers and
all other parties hereunder that (A) the funding and maintaining of such
Advances by such SPC shall not constitute a "prohibited transaction" (as defined
in Section 4.1(m) hereof), and (B) such designation, funding and maintenance
would not result in any interest requiring registration under the Securities Act
of 1933, as amended, or qualification under any state securities law, and shall
from time to time provide to the Borrowers the tax and other forms required
pursuant to Section 2.09(e) hereof with respect to such SPC as though such SPC
were a Lender hereunder. In no event shall the Borrowers or any Lender other
than the Granting Lender be obligated hereunder to pay any additional amounts
under any provision of this Agreement (pursuant to Article X hereof or
otherwise) by reason of a Granting Lender's designation of an SPC or the funding
or maintenance of Advances by such SPC, in excess of amounts which the Borrowers
would have been obligated to pay if such Granting Lender had not made such
designation and such Granting Lender were itself funding and maintaining such
Advances. The Administrative Agent shall register the interest of any SPC in an
advance from time to time on the Register maintained pursuant to Section
10.05(g) hereof.

                                     -102-
<PAGE>

     Section 11.6  Accounting Principles.  All references in this Agreement to
                   ---------------------
GAAP shall be to such principles as in effect from time to time.  All accounting
terms used herein without definition shall be used as defined under GAAP.  All
references to the financial statements of the Borrowers and to their Annualized
Operating Cash Flow, Operating Cash Flow, Total Debt, Fixed Charges, Pro Forma
Debt Service, Interest Expense, and other such terms shall be deemed to refer to
such items of the Borrowers and the Restricted Subsidiaries, on a fully
consolidated basis.  The Borrowers shall deliver to the Lenders at the same time
as the delivery of any quarterly or annual financial statements required
pursuant to Section 6.1 or 6.2 hereof, as applicable, (a) a description in
reasonable detail of any material variation between the application of GAAP
employed in the preparation of such statements and the application of GAAP
employed in the preparation of the next preceding quarterly or annual financial
statements, as applicable, and (b) reasonable estimates of the differences
between such statements arising as a consequence thereof.  If, within thirty
(30) days after the delivery of the quarterly or annual financial statements
referred to in the immediately preceding sentence, the Majority Lenders shall
object in writing to the Borrowers' determining compliance hereunder on such
basis, (1) calculations for the purposes of determining compliance hereunder
shall be made on a basis consistent with those used in the preparation of the
latest financial statements as to which such objection shall not have been made,
or (2) if requested by the Borrowers, the Majority Lenders will negotiate in
good faith to amend the covenants herein to give effect to the changes in GAAP
in a manner consistent with this Agreement (and so long as the Borrowers comply
in good faith with the provisions of this Section 11.6, no Default or Event of
Default shall occur hereunder solely as a result of such changes in GAAP).

     Section 11.7  Counterparts.  This Agreement may be executed in any number
                   ------------
of counterparts, each of which shall be deemed to be an original, but all such
separate counterparts shall together constitute but one and the same instrument.

     Section 11.8  Governing Law.  This Agreement and the Notes shall be
                   -------------
construed in accordance with and governed by the internal laws of the State of
New York applicable to agreements made and to be performed the State of New
York.  If any action or proceeding shall be brought by the Administrative Agent
or any Lender hereunder or under any other Loan Document in order to enforce any
right or remedy under this Agreement or under any Note or any other Loan
Document, each of the Borrowers hereby consents and will, and each of the
Borrowers will cause each Restricted Subsidiary to, submit to the jurisdiction
of any state or federal court of competent jurisdiction sitting within the area
comprising the Southern District of New York on the date of this Agreement.
Each of the Borrowers, for itself and on behalf of its Restricted Subsidiaries,
hereby agrees that, to the extent permitted by Applicable Law, service of the
summons and complaint and all other process which may be served in any such
suit, action or proceeding may be effected by mailing by registered mail a copy
of such process to the offices of the Borrowers at the address given in Section
11.1 hereof and that personal service of process shall not be required.  Nothing
herein shall be construed to prohibit service of process by any other method
permitted by law, or the bringing of any suit, action or proceeding in any other
jurisdiction.  The Borrowers agree that final judgment in such suit, action or
proceeding shall be conclusive and may be enforced in any other jurisdiction by
suit on the judgment or in any other manner provided by Applicable Law.

                                     -103-
<PAGE>

     Section 11.9   Severability.  Any provision of this Agreement which is
                    ------------
prohibited or unenforceable in any jurisdiction shall be ineffective to the
extent of such prohibition or unenforceability without invalidating the
remaining provisions hereof in that jurisdiction or affecting the validity or
enforceability of such provision in any other jurisdiction.

     Section 11.10  Interest.
                    --------

          (a) In no event shall the amount of interest due or payable hereunder
or under the Notes exceed the maximum rate of interest allowed by Applicable
Law, and in the event any such payment is inadvertently made by the Borrowers or
inadvertently received by the Administrative Agent or any Lender, then such
excess sum shall be credited as a payment of principal, unless, if no Event of
Default shall have occurred and be continuing, the Borrowers shall notify the
Administrative Agent or such Lender, in writing, that it elects to have such
excess sum returned forthwith. It is the express intent hereof that the
Borrowers not pay and the Administrative Agent and the Lenders not receive,
directly or indirectly in any manner whatsoever, interest in excess of that
which may legally be paid by the Borrowers under Applicable Law.

          (b) Notwithstanding the use by the Lenders of the Base Rate and the
LIBOR as reference rates for the determination of interest on the Loans, the
Lenders shall be under no obligation to obtain funds from any particular source
in order to charge interest to the Borrowers at interest rates related to such
reference rates.

     Section 11.11  Table of Contents and Headings.  The Table of Contents and
                    ------------------------------
the headings of the various subdivisions used in this Agreement are for
convenience only and shall not in any way modify or amend any of the terms or
provisions hereof, nor be used in connection with the interpretation of any
provision hereof.

     Section 11.12  Amendment and Waiver.  Neither this Agreement nor any Loan
                    --------------------
Document nor any term hereof or thereof may be amended orally, nor may any
provision hereof or thereof be waived orally but only by an instrument in
writing signed by or at the written direction of the Majority Lenders and, in
the case of an amendment, by the Borrowers, except that in the event of (a) any
increase in the amount of any Lender's portion of the Commitments or Commitment
Ratios or any reduction or postponement of the reductions to the Revolving Loan
Commitments set forth in Section 2.5(a) hereof, (b) any reduction (without a
corresponding payment) or postponement of the repayments of the principal amount
of the Loans provided in Section 2.7(b)(i) hereof, (c) any reduction or
postponement in interest or fees due hereunder of the payment thereof without a
corresponding payment of such interest or fee amount by the Borrowers, (d) any
release of any material portion of the Collateral for the Loans, except as
otherwise provided in Section 7.4 hereof, (e) any waiver of any Default due to
the failure by the Borrowers to pay any sum due to any of the Lenders hereunder,
(f) any release of any material Guarantor to a Guaranty of all or any portion of
the Obligations, except in connection with a merger, sale or other disposition
otherwise permitted hereunder (in which case, such release shall require no
further approval by the Lenders), (g) any amendment to the pro rata treatment of
the

                                     -104-
<PAGE>

Lenders set forth in Section 2.11 hereof, (h) any amendment of this Section
11.12, of the definition of Majority Lenders, or of any Section herein to the
extent that such Section requires action by all Lenders or the Issuing Bank, or
(i) subordinate the Loans in full to any of the Indebtedness, any amendment or
waiver or consent may be made only by an instrument in writing signed by each of
the Lenders or the Issuing Bank, respectively, and, in the case of an amendment,
by the Borrowers. Any amendment to any provision hereunder governing the rights,
obligations, or liabilities of the Administrative Agent in its capacity as such,
may be made only by an instrument in writing signed by such affected Person and
by each of the Lenders.

     Section 11.13  Entire Agreement.  Except as otherwise expressly provided
                    ----------------
herein, this Agreement, the other Loan Documents and the other documents
described or contemplated herein or therein will embody the entire agreement and
understanding among the parties hereto and thereto and supersede all prior
agreements and understandings relating to the subject matter hereof and thereof.

     Section 11.14  Other Relationships.  No relationship created hereunder or
                    -------------------
under any other Loan Document shall in any way affect the ability of the
Administrative Agent and each Lender to enter into or maintain business
relationships with any Borrower or any Affiliate thereof beyond the
relationships specifically contemplated by this Agreement and the other Loan
Documents.

     Section 11.15  Directly or Indirectly.  If any provision in this Agreement
                    ----------------------
refers to any action taken or to be taken by any Person, or which such Person is
prohibited from taking, such provision shall be applicable whether such action
is taken directly or indirectly by such Person, whether or not expressly
specified in such provision.

     Section 11.16  Reliance on and Survival of Various Provisions.  All
                    ----------------------------------------------
covenants, agreements, statements, representations and warranties made herein or
in any certificate delivered pursuant hereto shall (a) be deemed to have been
relied upon by the Administrative Agent, each of the Lenders and the Issuing
Bank notwithstanding any investigation heretofore or hereafter made by them and
(b) survive the execution and delivery of the Notes and shall continue in full
force and effect so long as any Note is outstanding and unpaid.  Any right to
indemnification hereunder, including, without limitation, rights pursuant to
Sections 2.10, 2.12, 5.11, 10.3 and 11.2 hereof, shall survive the termination
of this Agreement and the payment and performance of all Obligations.

     Section 11.17  Senior Debt.  The Obligations are secured by the Security
                    -----------
Documents and are intended by the parties hereto to be in parity with the
Interest Hedge Agreements and senior in right of payment to all other
Indebtedness of the Borrowers.

     Section 11.18  Obligations.  The obligations of the Administrative Agent,
                    -----------
each of the Lenders and the Issuing Bank hereunder are several, not joint.

     Section 11.19  Confidentiality.  The Administrative Agent, the Lenders and
                    ---------------
the Issuing Bank shall hold all non-public, proprietary or confidential
information (which has been identified

                                     -105-
<PAGE>

as such by the Borrowers) obtained pursuant to the requirements of this
Agreement in accordance with their customary procedures for handling
confidential information of this nature and in accordance with safe and sound
lending practices; provided, however, that the Administrative Agent, Lenders and
                   --------  -------
the Issuing Bank may make disclosure of any such information (a) to their
examiners, Affiliates, any Approved Fund, outside auditors, counsel,
consultants, appraisers, other professional advisors and any direct or indirect
contractual counterparty in swap agreements or such counterparty's professional
advisor in connection with this Agreement or as reasonably required by any
proposed syndicate member or any proposed transferee or participant in
connection with the contemplated transfer of any Note or participation therein,
in each case, so long as any such Person (other than any examiners) receiving
such information is advised of the provisions of this Section 11.19 and agrees
to be bound thereby, (b) as required or requested by any governmental authority
or representative thereof or 'in' connection with the enforcement hereof or of
any Loan Document or related document or (c) pursuant to legal process or with
respect to any litigation between or among any Borrower and any of the
Administrative Agent, the Lenders or the Issuing Bank. In no event shall the
Administrative Agent, any Lender or the Issuing Bank be obligated or required to
return any materials furnished to it by the Borrowers. The foregoing provisions
shall not apply to the Administrative Agent, a Lender or the Issuing Bank with
respect to information that (i) is or becomes generally available to the public
(other than through the Administrative Agent, such Lender or the Issuing Bank),
(ii) is already in the possession of the Administrative Agent, such Lender or
the Issuing Bank on a nonconfidential basis, or (iii) comes into the possession
of the Administrative Agent, such Lender or the Issuing Bank in a manner not
known to the Administrative Agent, such Lender or the Issuing Bank to involve a
breach of a duty of confidentiality owing to the Borrowers.

                       ARTICLE 12  Waiver of Jury Trial

     Section 12.1  Waiver of Jury Trial.  EACH OF THE BORROWERS, FOR ITSELF AND
                   --------------------
ON BEHALF OF THE RESTRICTED SUBSIDIARIES, AND THE ADMINISTRATIVE AGENT, THE
ISSUING BANK AND THE LENDERS, HEREBY AGREE, TO THE EXTENT PERMITTED BY LAW, TO
WAIVE AND HEREBY WAIVE THE RIGHT TO A TRIAL BY JURY IN ANY COURT AND IN ANY
ACTION OR PROCEEDING OF ANY TYPE IN WHICH THE BORROWERS, ANY RESTRICTED
SUBSIDIARIES, ANY OF THE LENDERS, THE ADMINISTRATIVE AGENT, THE ISSUING BANK, OR
ANY OF THEIR RESPECTIVE SUCCESSORS OR ASSIGNS IS A PARTY, AS TO ALL MATTERS AND
THINGS ARISING DIRECTLY OR INDIRECTLY OUT OF THIS AGREEMENT, ANY OF THE NOTES OR
THE OTHER LOAN DOCUMENTS AND THE RELATIONS AMONG THE PARTIES LISTED IN THIS
SECTION 12.1. EXCEPT AS PROHIBITED BY LAW, EACH PARTY TO THIS AGREEMENT WAIVES
ANY RIGHTS IT MAY HAVE TO CLAIM OR RECOVER IN ANY LITIGATION REFERRED TO IN THIS
SECTION, ANY SPECIAL, EXEMPLARY, PUNITIVE OR CONSEQUENTIAL DAMAGES OR ANY
DAMAGES OTHER THAN, OR IN ADDITION TO, ACTUAL DAMAGES.  EACH PARTY TO THIS
AGREEMENT (A) CERTIFIES THAT NEITHER ANY REPRESENTATIVE, AGENT OR ATTORNEY OF
THE ADMINISTRATIVE AGENT, THE ISSUING BANK OR ANY

                                     -106-
<PAGE>

LENDER HAS REPRESENTED, EXPRESSLY OR OTHERWISE, THAT THE ADMINISTRATIVE AGENT,
THE ISSUING BANK OR ANY LENDER WOULD NOT, IN THE EVENT OF LITIGATION, SEEK TO
ENFORCE THE FOREGOING WAIVERS AND (B) ACKNOWLEDGES THAT IT HAS BEEN INDUCED TO
ENTER INTO THIS AGREEMENT AND EACH OTHER LOAN DOCUMENT BY, AMONG OTHER THINGS,
THE MUTUAL WAIVERS AND CERTIFICATIONS IN THIS SECTION. THE PROVISIONS OF THIS
SECTION HAVE BEEN FULLY DISCLOSED BY AND TO THE PARTIES AND THE PROVISIONS SHALL
BE SUBJECT TO NO EXCEPTIONS. NO PARTY HAS IN ANY WAY AGREED WITH OR REPRESENTED
TO ANY OTHER PARTY THAT THE PROVISIONS OF THIS SECTION WILL NOT BE FULLY
ENFORCED IN ALL INSTANCES.

                 [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

                                     -107-
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement or
caused it to be executed by their duly authorized officers, all as of the day
and year first above written.

BORROWERS:                         AMERICAN TOWER, L.P.

                                   By ATC GP INC., its General Partner

                                   By:______________________________________

                                      Title:________________________________

                                   AMERICAN TOWERS, INC.

                                   By:______________________________________

                                      Title:________________________________

                                   ATC TELEPORTS, INC.

                                   By:______________________________________

                                      Title:________________________________

                                                                          Page 1
<PAGE>

ADMINISTRATIVE AGENT,
LENDERS AND ISSUING
BANK:                              TORONTO DOMINION (TEXAS), INC., as
                                   Administrative Agent, for itself, the
                                   Issuing Bank and the Lenders, as Issuing
                                   Bank and as a Lender

                                   By:___________________________________

                                      Title:_____________________________

                                                                          Page 2
<PAGE>

                                   THE CHASE MANHATTAN BANK, as a Lender

                                   By:__________________________________

                                      Title:____________________________

                                                                          Page 3
<PAGE>

                                        THE BANK OF NEW YORK, as a Lender

                                        By:_________________________________

                                           Title:___________________________

                                                                          Page 4
<PAGE>

                                   CREDIT SUISSE FIRST BOSTON, as Lender

                                   By:_____________________________________

                                      Title:_______________________________

                                   By:_____________________________________

                                      Title:_______________________________

                                                                          Page 5
<PAGE>

                                   THE BANK OF NOVA SCOTIA, as a Lender

                                   By:_____________________________________

                                      Title:_______________________________

                                                                          Page 6
<PAGE>

                                   CREDIT LYONNAIS NEW YORK BRANCH, as a
                                   Lender

                                   By:_________________________________________

                                      Title:___________________________________

                                                                          Page 7
<PAGE>

                                        BANKERS TRUST COMPANY, as a Lender

                                        By:____________________________________

                                           Title:______________________________

                                                                          Page 8
<PAGE>

                                   GENERAL ELECTRIC CAPITAL CORPORATION, as a
                                   Lender

                                   By:__________________________________________

                                      Title:____________________________________

                                                                          Page 9
<PAGE>

                                   KEY CORPORATE CAPITAL INC., as a Lender

                                   By:________________________________________

                                      Title:__________________________________

                                                                         Page 10
<PAGE>

                                   COOPERATIEVE CENTRALE RAIFFEISEN-
                                   BOERENLEENBANK B.A., "RABOBANK
                                   NEDERLAND", NEW YORK BRANCH

                                   By:____________________________________

                                      Title:______________________________

                                   By:____________________________________

                                      Title:______________________________

                                                                         Page 11
<PAGE>

                                   ROYAL BANK OF CANADA, as a Lender

                                   By:__________________________________

                                      Title:____________________________

                                                                         Page 12
<PAGE>

                                   UNION BANK OF CALIFORNIA, as a Lender

                                   By:______________________________________

                                      Title:________________________________

                                                                         Page 13
<PAGE>

                                   BANK OF AMERICA, N.A., as a Lender

                                   By:______________________________________

                                      Title:________________________________

                                                                         Page 14
<PAGE>

                                        BANK OF MONTREAL, as a Lender

                                        By:__________________________________

                                           Title:____________________________

                                                                         Page 15
<PAGE>

                                        CITICORP USA, INC., as a Lender

                                        By:___________________________________

                                           Title:_____________________________

                                                                         Page 16
<PAGE>

                                        FIRST UNION NATIONAL BANK, as a Lender

                                        By:____________________________________

                                           Title:______________________________

                                                                         Page 17
<PAGE>

                                   LEHMAN COMMERCIAL PAPER INC., as a Lender

                                   By:_________________________________________

                                      Title:___________________________________

                                   SYNDICATED LOAN FUNDING TRUST, as a Lender
                                   By: Lehman Commercial Paper Inc.,
                                   Not in its individual capacity but solely
                                   as Asset Manager

                                   By:_________________________________________

                                      Title:___________________________________

                                                                         Page 18
<PAGE>

                                   BEAR STEARNS CORPORATE LENDING INC., as a
                                   Lender

                                   By:_______________________________________

                                      Title:_________________________________

                                                                         Page 19
<PAGE>

                                        FLEET NATIONAL BANK, as a Lender

                                        By:_________________________________

                                           Title:___________________________

                                                                         Page 20
<PAGE>

                                        BANK UNITED, as a Lender

                                        By:_______________________________

                                           Title:_________________________

                                                                         Page 21
<PAGE>

                                   BAYERISCHE HYPO- UND VEREINSBANK AG,
                                   NEW YORK BRANCH, as a Lender

                                   By:______________________________________

                                      Title:________________________________

                                   By:______________________________________

                                      Title:________________________________

                                                                         Page 22
<PAGE>

                                   IBM CREDIT CORPORATION, as a Lender

                                   By:______________________________________

                                      Title:________________________________

                                                                         Page 23
<PAGE>

                              PNC BANK, NATIONAL ASSOCIATION, as a Lender

                              By:___________________________________________

                                 Title:_____________________________________

                                                                         Page 24
<PAGE>

                                   SUNTRUST BANK, as a Lender

                                   By:__________________________________

                                      Title:____________________________

                                                                         Page 25
<PAGE>

                                   CREDIT LOCAL DE FRANCE - NEW YORK AGENCY,
                                   as a Lender

                                   By:_______________________________________

                                      Title:_________________________________

                                   By:_______________________________________

                                      Title:_________________________________

                                                                         Page 26
<PAGE>

                                   DRESDNER BANK AG, NEW YORK AND GRAND
                                   CAYMAN BRANCHES, as a Lender

                                   By:______________________________________

                                      Title:________________________________

                                   By:______________________________________

                                      Title:________________________________

                                                                         Page 27
<PAGE>

                                        US TRUST, as a Lender

                                        By:_________________________________

                                           Title:___________________________

                                                                         Page 28
<PAGE>

                                   HOWARD BANK, N.A., as a Lender

                                   By:____________________________________

                                      Title:______________________________

                                                                         Page 29
<PAGE>

                                        ALLFIRST BANK, as a Lender

                                        By:_______________________________

                                           Title:_________________________

                                                                         Page 30
<PAGE>

                                   THE CIT GROUP/EQUIPMENT FINANCING, INC.,
                                   as a Lender

                                   By:________________________________________

                                      Title:__________________________________

                                                                         Page 31
<PAGE>

                                   FRANKLIN FLOATING RATE TRUST, as a Lender

                                   By:________________________________________

                                      Title:__________________________________

                                                                         Page 32
<PAGE>

                                   GALAXY CLO 1999-1, LTD., as a Lender
                                   By: SAI Investment Adviser, Inc.,
                                   its Collateral Agent

                                   By:_____________________________________

                                      Title:_______________________________

                                                                         Page 33
<PAGE>

                                   KEMPER FLOATING RATE FUND, as a Lender

                                   By:______________________________________

                                      Title:________________________________

                                                                         Page 34
<PAGE>

                                   KZH III LLC, as a Lender

                                   By:____________________________________

                                      Title:______________________________

                                   KZH CYPRESSTREE-1 LLC, as a Lender

                                   By:____________________________________

                                      Title:______________________________

                                   KZH SOLEIL-2 LLC, as a Lender

                                   By:____________________________________

                                      Title:______________________________

                                                                         Page 35
<PAGE>

                                   METROPOLITAN LIFE INSURANCE COMPANY,
                                   as a Lender

                                   By:_______________________________________

                                      Title:_________________________________

                                                                         Page 36
<PAGE>

                                   MONY LIFE INSURANCE COMPANY, as a Lender

                                   By:_________________________________________

                                      Title:___________________________________

                                                                         Page 37
<PAGE>

                              MORGAN STANLEY DEAN WITTER PRIME
                              INCOME TRUST, as a Lender

                              By:____________________________________

                                 Title:______________________________

                                                                         Page 38
<PAGE>

                                   OPPENHEIMER SENIOR FLOATING RATE FUND,
                                   as a Lender

                                   By:_______________________________________

                                      Title:_________________________________

                                                                         Page 39
<PAGE>

                                   PPM SPYGLASS FUNDING TRUST, as a Lender

                                   By:_______________________________________

                                      Title:_________________________________

                                                                         Page 40
<PAGE>

                                   WINGED FOOT FUNDING TRUST, as a Lender

                                   By:______________________________________

                                      Title:________________________________

                                                                         Page 42
<PAGE>

                                   MERRILL LYNCH SENIOR FLOATING RATE
                                   FUND, INC., as a Lender

                                   By:____________________________________

                                      Title:______________________________

                                   MERRILL LYNCH SENIOR FLOATING RATE FUND
                                   II, INC., as a Lender

                                   By:____________________________________

                                      Title:______________________________

                                   SENIOR HIGH INCOME PORTFOLIO, INC.,
                                   as a Lender

                                   By:____________________________________

                                      Title:______________________________

                                                                         Page 43
<PAGE>

                                   DEBT STRATEGIES FUND, INC., as a Lender

                                   By:_______________________________________

                                      Title:_________________________________

                                   DEBT STRATEGIES FUND II, INC., as a Lender

                                   By:_______________________________________

                                      Title:_________________________________

                                   DEBT STRATEGIES FUND III, INC., as a Lender

                                   By:_______________________________________

                                      Title:_________________________________

                                                                         Page 44
<PAGE>

                              CYPRESSTREE INVESTMENT FUND, LLC, as a Lender
                              By: CypressTree Investment Management Company,
                                  Inc., its Managing Member

                              By:______________________________________________

                                 Title:________________________________________

                              CYPRESSTREE SENIOR FLOATING RATE FUND, as a Lender
                              By: CypressTree Investment Management Company,
                                  Inc., as Portfolio Manager

                              By:______________________________________________

                                 Title:________________________________________

                              NORTH AMERICAN SENIOR FLOATING RATE FUND,
                              as a Lender
                              By: CypressTree Investment Management Company,
                                  Inc., as Portfolio Manager

                              By:______________________________________________

                                 Title:________________________________________

                                                                         Page 45
<PAGE>

                              BALANCED HIGH YIELD FUND II, LTD., as a Lender

                              By:_____________________________________________

                                 Title:_______________________________________

                                                                         Page 46
<PAGE>

                                   CANADIAN IMPERIAL BANK OF COMMERCE, as a
                                   Lender

                                   By:_________________________________________

                                      Title:___________________________________

                                                                         Page 47
<PAGE>

                                        STEIN ROE FLOATING RATE FUND LIMITED
                                        LIABILITY COMPANY, as a Lender

                                        By:___________________________________

                                           Title:_____________________________

                                                                         Page 48
<PAGE>

                                        KZH SHOSHONE LLC, as a Lender

                                        By:________________________________

                                           Title:__________________________

                                        KZH RIVERSIDE LLC, as a Lender

                                        By:________________________________

                                           Title:__________________________

                                                                         Page 49
<PAGE>

                                   VAN KAMPEN SENIOR INCOME TRUST, as a Lender
                                   By: Van Kampen Investment Advisory Corp.

                                   By:_________________________________________

                                      Title:___________________________________

                                                                         Page 50
<PAGE>

                                   KZH LANGDALE LLC, as a Lender

                                   By:__________________________________

                                      Title:____________________________

                                                                         Page 51
<PAGE>

                                        KZH ING-1 LLC, as a Lender

                                        By:_____________________________

                                           Title:_______________________

                                        KZH ING-2 LLC, as a Lender

                                        By:_____________________________

                                           Title:_______________________

                                        KZH ING-3 LLC, as a Lender

                                        By:_____________________________

                                           Title:_______________________

                                                                         Page 52
<PAGE>

                                   PILGRIM PRIME RATE TRUST, as a Lender
                                   By: Pilgrim Investments, Inc., as its
                                       investment manager

                                   By:______________________________________

                                      Title:________________________________

                                                                         Page 53

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