CREDIT AGREEMENT


         THIS  CREDIT  AGREEMENT  is  entered  into as of June  17,  1998 by and
between  Motorola Inc., a Delaware  corporation,  (hereinafter  "Motorola")  and
ARDIS Company, a New York general partnership (the "Borrower" or "you").

         You have asked Motorola to provide financing to you (the "Credit")  for
the purchase of certain equipment from Motorola.  Motorola is willing to provide
the Credit on the terms and  conditions  set forth in this Credit  Agreement and
the attached  Exhibits,  which are part of this Credit Agreement.  The terms and
conditions ("Terms and Conditions") attached to this Credit Agreement as Exhibit
"A" include definitions for many of the terms used below.

         1. Amount of Credit;  Note. The aggregate  maximum  principal amount of
            -----------------------
Credit that may be drawn under this Credit  Agreement shall be $10,000,000.  You
may obtain Advances under this Credit  Agreement until June 16, 2000, if, at the
time of requesting  an Advance,  you have  complied  with all  Requirements  for
Advances.  Amounts  repaid under this Credit  Agreement may not be  re-borrowed.
Motorola  shall have no  obligation,  express or implied,  to extend or to grant
additional  credit  after this Credit  Agreement  expires.  The Credit  shall be
evidenced by a promissory  note ("Note") in  substantially  the form attached as
Exhibit "B" duly executed on behalf of the Borrower.

         2. Drawdown  Procedure.  At the time you order equipment from Motorola,
            -------------------
you will  notify  Motorola in writing on the  purchase  order that you intend to
finance  the  purchase  with  Motorola  under this  Credit  Agreement,  and will
identify the location (by State and county) at which each item of equipment  may
be located during the term of this Agreement. By issuing that notice you will be
deemed to represent  and warrant that all prior  statements  of your account are
correct.  Upon  shipment  of each  such  item of  equipment,  provided  that all
Requirements for Advances have been satisfied,  if the Requirements for Advances
have been satisfied,  Motorola shall thereupon be deemed to have made an Advance
equal to 75% of the purchase price of such item of equipment, and Motorola shall
make a  notation  on its books and  records,  and on the  schedule  to the Note,
showing  such  Advance.  On each  Quarterly  Date during the term of this Credit
Agreement,  the aggregate amount of the Advances made since the date hereof,  or
if later,  since the date of the most recent  Quarterly Date, shall constitute a
Loan, which shall bear interest at the Applicable Rate and amortize as set forth
herein. You hereby irrevocably  authorize Motorola at any time to endorse on the
Note (or record on its books and  records)  the date and amount of any  Advances
made by Motorola to you,  the  outstanding  balance of all Advances and Loans at
any time and each payment and prepayment of any principal plus interest accruing
thereon.  Such  endorsement  or  record  shall be prima  facie  evidence  of the
principal  amount  owing on the Note in any  proceedings  to enforce the payment
thereof;   provided,  that  failure  to  record  an  Advance  or  any  erroneous
recordation shall not affect  Borrower's  obligations to repay all sums actually
borrowed  hereunder.  No Advance or deemed  Advance  shall be permitted  for any
payment of  principal  or interest  due under the Note.  You will  receive  from
Motorola,  on or about the Thursday immediately preceding the last Monday of the
month,  an  itemized  list of  equipment  provided to you during the most recent
monthly  period.  You will pay to Motorola,  within thirty days from the invoice
date,  the full amount of the purchase price for equipment and services shown on
such invoice,  less the amount of any Advances made for the purchase of any such
equipment as provided above.

         3.       Interest Rate.  You agree to pay interest to Motorola  on  the
                  --------------
principal  amount of the Credit  outstanding from time to time. If the Credit is
not in Default,  you will pay interest each quarter in arrears at the Applicable
Rate.  If, and as long as, the Credit is in Default,  the interest  rate will be
increased  another three percent (3%) per annum above the  Applicable  Rate (the
"Default  Rate") and will be payable upon  demand.  As detailed in the Terms and
Conditions,  under no circumstances will you be required to pay an interest rate
or an amount of interest greater than the maximum interest allowed by applicable
law.

         4.       Repayment Terms.  Motorola  will  send  you quarterly invoices
                  --------------- 
showing  principal  and interest due. You agree to pay each invoice on or before
its due date. The principal  portion of each Loan will be amortized over a three
year period  beginning with the Quarterly Date on which such Loan commences,  in
twelve consecutive equal quarterly installments.  You agree to pay a late charge
equal  to five  percent  (5%) of any  principal  amount  payable  by you for any
invoice  payment not received by Motorola  within ten days of the due date. Your
failure to pay an invoice  within  fifteen days of its due date  constitutes  an
Event of Default under this Credit Agreement.

         5.  Financial Information.  Motorola  has  agreed to provide the Credit
             --------------------- 
based on financial information you have prepared and supplied.  Between the date
of the financial information and the date of this Credit Agreement,  you confirm
that there has been no material,  adverse change in your financial  condition or
business operation. As described in the Terms and Conditions,  you agree to give
Motorola  updated   financial   information   during  the  time  the  Credit  is
outstanding.

         6.  Collateral.  As security for the timely payment and  performance of
             ----------
your  Obligations,  you hereby  grant to Motorola a  perfected,  first  priority
security  interest and lien in the  Collateral.  At the time of delivery of each
purchase order as described in Section 2 above,  you will deliver to Motorola an
executed Financing  Statement on form UCC-1 substantially in the form of Exhibit
"E" to this Agreement for filing in each  jurisdiction  identified as a location
where the equipment ordered may be located during the term of the Agreement. You
hereby authorize Motorola to attach to each such Financing  Statement a schedule
listing  the serial  numbers or other  identifying  information  describing  the
equipment  shipped  in  accordance  with the  purchase  order,  and to file such
Financing  Statements  in each  jurisdiction  in  which  it  deems  such  filing
necessary to perfect Motorola's  security interest in the Collateral.  You agree
to execute such other  documents and take all  reasonable  actions  requested by
Motorola,  at your expense, to perfect and maintain the perfection of Motorola's
security interest in the Collateral.

         The Credit will also be secured by the joint and several  Guarantees of
the Guarantors listed on Exhibit "C",  guaranteeing  repayment of the Credit (in
accordance with Guarantee Agreements in the form attached as Exhibit "C").

         7.  Waiver  of Jury  Trial.  YOU AND  MOTOROLA  AGREE  THAT ANY  CLAIM,
             ----------------------
COUNTERCLAIM,  SETOFF,  OR  DEFENSE  RELATING  IN ANY WAY TO (A) THIS  AGREEMENT
(INCLUDING ALL EXHIBITS AND ALL OTHER DOCUMENTS RELATING TO THIS AGREEMENT),  OR
(B) ANY ACTION, OMISSION, COURSE OF CONDUCT,  PRACTICE, OR TRANSACTION BY YOU OR
MOTOROLA  (INCLUDING  THE RESPECTIVE  OFFICERS,  DIRECTORS,  EMPLOYEES,  AGENTS,
ATTORNEYS, AND OTHER REPRESENTATIVES OF EACH) SHALL BE HEARD AND DETERMINED BY A
COURT  WITHOUT A JURY.  YOU AND MOTOROLA  HAVE  ENTERED  INTO THIS  AGREEMENT IN
RELIANCE UPON THIS PROVISION AS A MATERIAL TERM OF THE CREDIT.

         8.  Governing Law. Motorola's headquarters are in Schaumburg, Illinois;
             ------------- 
this Credit  Agreement  will,  if accepted and  executed by  Motorola,  become a
contract  in the  State of  Illinois  and be  governed  by the law of  Illinois,
without  regard to its conflicts of law rules.  Upon the occurrence of any Event
of Default,  however,  Motorola shall also have the right to enforce this Credit
Agreement and related  collateral  documents in accordance  with the laws of any
jurisdiction in which an Obligor or Collateral may then be located,  or in which
the law permits Motorola to bring suit.

         9. No Other Agreements;  Complete Review. You and Motorola  acknowledge
            -------------------------------------
and agree that this Credit Agreement and the other documents  executed  pursuant
to this Agreement collectively comprise the complete written agreement regarding
the Credit;  there are no other  understandings,  inducements,  representations,
negotiations,  or promises of any kind other than those  written  here and those
made a part of this Credit  Agreement.  You and Motorola also  acknowledge  that
they have  reviewed,  with  their  own  attorneys  if  desired,  all the  terms,
conditions, and provisions of this Credit Agreement and the attached Exhibits.

         10.      Limitation on Liability.  In  no event shall Motorola have any
                  -----------------------
liability  under or in  connection  with this  Credit  Agreement  or any exhibit
hereto for special, incidental,  indirect, or consequential damages of any sort,
including  (without  limitation) lost profits.  If you have previously  obtained
financing  from  Motorola or  otherwise  purchased  equipment  or services  from
Motorola:

                  (a) you hereby  release  Motorola and its officers, directors,
and employees  from and against any claim,  counterclaim,  defense,  setoff,  or
other  liability with respect to any  transaction,  course of dealing,  or other
matter that arose or occurred before you signed this Credit Agreement, and

                  (b) you acknowledge that any prior credit terms or agreements,
whether written or oral (but excluding any open account arrangements),  have now
been superseded and replaced by this Credit Agreement.

         11. Absolute  Obligation.  ANY  PRESENT OR FUTURE  LAW TO THE  CONTRARY
NOTWITHSTANDING,  YOUR  OBLIGATION  TO PAY MOTOROLA ALL AMOUNTS DUE HEREUNDER IS
ABSOLUTELY UNCONDITIONAL. YOU SHALL NOT BE ENTITLED TO ANY ABATEMENT, REDUCTION,
SETOFF, COUNTERCLAIM, DEFENSE, INTERRUPTION,  DEFERMENT, RECOUPMENT OR DEDUCTION
WITH  RESPECT TO ANY  PRINCIPAL  OR  INTEREST  PAYMENT OR ANY OTHER SUM  PAYABLE
HEREUNDER, NO MATTER HOW, WHEN OR AGAINST WHOM ASSERTED, ARISING OR CLAIMED, NOR
SHALL ANY OF YOUR OBLIGATIONS  HEREUNDER BE AFFECTED FOR ANY REASON  WHATSOEVER.
The  foregoing  shall not be deemed to amend or limit your right to make a claim
against  Motorola for any  obligation  or liability  that Motorola may otherwise
have to you under the Purchase Agreement.

         12. Confidentiality. Neither you nor Motorola will disclose this Credit
             --------------- 
Agreement  or its terms to a third  party  except (a) insofar as the third party
has a "need to know" (as in the case of a party's  accountants),  in which  case
the third party will be  instructed  to abide by this  Paragraph  10, (b) in the
event disclosure is necessary to enforce the Credit Agreement or is compelled by
subpoena,  requirement of law, or order of a court of competent jurisdiction, or
(c) by prior written consent of both parties.











         EXECUTED by the parties as of the date first set forth above:

Notice Address:                                      ARDIS COMPANY
ARDIS Company
10802 Parkridge Boulevard
Reston, VA 20901-5416                                By:/s/Walter V. Purnell Jr.
                                                        ------------------------
Attn: President and Treasurer                           Walter V. Purnell Jr.

Tel.: (703) 758 6000                                 Its:  President
Fax : (703) 758-6111

With a copy to:
ARDIS Company
300 Knightsbridge Parkway
Suite 500
Lincolnshire, IL 60069
Attn: Vice President and Executive Counsel

Tel.: (847) 913-4226
Fax: (847) 913-4755


Notice Address:                                   MOTOROLA INC.
Motorola Credit Corporation
1303 East Algonquin Road
Schaumburg, Illinois  60196
Tel: (847) 725-4502                               By:/s/Michael Faill
                                                     --------------------
Fax: (847) 725-5097
                                                  Its:Sr. Manager
                                                      Worldwide Customer Finance
With a copy to:

Motorola Paging Products Group
5401 N. Beach Street
Mail Stop S22313
Fort Worth, TX  76137
Attn: Customer Finance
Tel: (817) 245-2705
Fax: (817) 245-2236














                                    EXHIBITS



         A        Terms and Conditions

         B        Form of Promissory Note

         C        List of Guarantors and Form of Guarantee Agreement

         D        List of Subsidiaries of the Borrower

         E        Form of Financing Statement

         F        List of Assumed Names of the Borrower





                                    EXHIBIT A


                              TERMS AND CONDITIONS


         The following  terms and  conditions  are referred to as the "Terms and
Conditions"  in, and have been made a part of, the Credit  Agreement dated as of
June 17,  1998  between  MOTOROLA  INC.  ("Motorola")  and  ARDIS  COMPANY  (the
"Borrower" or "you").

                                 1. Definitions

         Certain terms of the Credit  Agreement  and these Terms and  Conditions
carry particular meanings when used with initial capital letters, as follows:

         "Advance" means an extension of Credit made under the Credit  Agreement
upon satisfaction of the conditions set forth in the Credit Agreement, including
these Terms and Conditions.

         "Advance  Date" means the date on which an Advance is made or deemed to
be made under the Credit Agreement.

         "Agreement" and "Credit Agreement" mean the Credit Agreement  described
above, these Terms and Conditions, and the other Exhibits attached to the Credit
Agreement.

         "Applicable Rate" means:  (i) from the date  of  an  Advance  until the
immediately  following  Quarterly  Date,  a  rate  of interest equal to thirteen
percent (13%) and (ii) from  the  Quarterly Date which constitutes the Borrowing
Date with respect to a Loan until the date of repayment in full of such Loan,  a
rate  of  interest  equal  to  LIBOR  plus  7.0%.  The  Applicable  Rate will be
calculated on the basis of a 365 or 366 day year, based upon the  actual  number
of days elapsed.

         "Applicable Term" means thirty six months from the applicable Borrowing
Date for repayment of principal.

         "Borrowing  Date"  means  each  Quarterly  Date  on  which  one or more
Advances shall become a Loan under the Credit Agreement.

         "Business Day" means a day other than Saturday, Sunday or any other day
on which  commercial  banks in  Illinois  are  authorized  or required by law to
close.

         "Code" means the Internal Revenue Code of 1986, as amended from time to
time.

         "Collateral" means all of your right, title, and interest in and to any
equipment  purchased  by you  from  Motorola  with  proceeds  from  any  Advance
hereunder,  wherever located, whether now owned or hereafter acquired, including
all substitutions,  accessions,  replacements, or renewals, and all proceeds and
products with respect to any such property (including,  without limitation,  any
insurance proceeds).

         "Default"  means the  occurrence  of any of the  events  or  conditions
specified  in Section 6,  whether or not such event has matured into an Event of
Default through the giving of notice, the lapse of time, or both.

         "Escrowed Funds" means funds held in escrow with respect to amounts due
under the UPS Agreement as set forth in the letter  agreement dated December 31,
1998 between American Mobile Satellite Corporation and Motorola.

         "Event of Default" is defined in Section 6.

         "FCC" means the Federal Communications Commission.

         "Filing  Jurisdiction"  means,  as  to  any  item  of  Collateral,  any
jurisdiction  in  which  Borrower  has  notified  Motorola  that  such  item  of
Collateral may be located, as required under Section 2 of the Agreement, and has
delivered Financing  Statements to Motorola,  as required under Section 6 of the
Agreement, and (after the date which is thirty (30) days following delivery of a
notice to Motorola under Section 4.8.4 hereof), such additional jurisdictions as
are identified in such notice with respect to such item of Collateral.

         "GAAP" means Generally Accepted Accounting  Principles in effect in the
United States of America from time to time.

         "Governmental  Authority" means any nation or government,  any state or
other  political  subdivision  thereof,  and any  entity  exercising  executive,
legislative,  judicial,  regulatory or administrative functions of or pertaining
to government.

         "Guarantor"  means  each of the joint  and  several  guarantors  of the
Borrower's obligations as identified on Exhibit "C" to the Credit Agreement.

         "Indebtedness"  means at a particular  time, your (i)  indebtedness for
financed  money or for the deferred  purchase price of property or services with
respect to which such Person is liable,  contingently or otherwise,  as obligor,
guarantor or otherwise,  or in respect of which you otherwise  assure a creditor
against  loss,  and (ii)  obligations  under leases which have been or should be
recorded,  in  accordance  with  GAAP,  as  capital  leases in  respect of which
obligations you are liable,  contingently or otherwise, as obligor, guarantor or
otherwise,  or with respect to which  obligations you assure a creditor  against
loss.

         "Lease Obligations" means as of the date of any determination  thereof,
your rental  commitments  under leases,  excluding only obligations under leases
which are classified as Indebtedness on your balance sheet.

         "LIBOR"  means  the  three  month  London  Interbank  Offered  Rate (as
published in the Wall Street Journal) on Business Day immediately  preceding the
Quarterly  Date which is the first date of the period during which interest on a
Loan is being calculated.

         "Lien"  means  any  mortgage,  deed of  trust,  pledge,  hypothecation,
assignment,   encumbrance,   lien  (statutory  or  other),   security  interest,
preferential  payment  arrangement  or other  security  agreement or arrangement
(including,  without  limitation,  any conditional sale or other title retention
agreement,  any financing  lease having the same  economic  effect as any of the
foregoing,  and  the  filing  of  any  financing  statement  under  the  Uniform
Commercial Code or comparable law of any jurisdiction).

         "Loan" means the aggregate  principal  amount of Advances made during a
period ending on a Quarterly  Date and beginning on either the Effective Date of
this Agreement or the immediately preceding Quarterly Date.

         "Obligations"  means  all of  each  Obligor's  obligations  (a) for the
payment of money to Motorola, and (b) for the performance of any covenant, term,
provision, or requirement of the Agreement.

         "Obligors"  means  you and  each  of the  Guarantors  obligated  either
personally or through a pledge of property, for repayment of the Credit.

         "Person"  means  an  individual,   partnership,   corporation,  limited
liability company,  business trust, joint stock company,  trust,  unincorporated
association,  joint venture,  Governmental Authority or other entity of whatever
nature.

         "Purchase Agreement" means the Master Purchase Agreement dated December
19, 1997 between Motorola Inc. and ARDIS Company.

         "Requirement  of  Law"  means  as  to  any  Person,   the  articles  of
incorporation,  by-laws or other  organizational or governing  documents of such
Person,  and any law, or  determination  of any  arbitrator  or a court or other
Governmental  Authority,  in each case applicable to or binding upon such Person
or any of its  properties  or to which  such  Person or any of its  property  is
subject.

         "Responsible  Officer"  means  the  chief  executive  officer  or chief
financial  officer  of any  corporation,  or any  other  individual  who is duly
authorized  by the Person  represented  to perform  the duties  required  by the
Agreement.

         "UCC"  means  the  Uniform   Commercial   Code  as  in  effect  in  the
jurisdiction specified in the "governing law" provision of the Credit Agreement.


         Any accounting  terms not fully defined in the Agreement shall have the
meanings given to them under GAAP.


                            2. Principal and Interest

         2.1      Statements.  Motorola will invoice you quarterly for scheduled
                  ----------
principal and interest payments under the Credit.  You will make each payment on
its due date.  If Motorola's statement  of the  balance  or  amount due does not
agree with your records, you will notify Motorola in writing of the amount shown
by  your  records  within  ten  (10) Business Days of your receipt of Motorola's
statement.   Absent such notification,  or manifest error,  Motorola's statement
shall be presumed to be correct.   Nosuch  notification  shall suspend or affect
your duty to make timely payment.

         2.2      Optional Prepayments. You may, at your option, on any Business
                  --------------------
Day,  prepay  the  Credit,  in whole or in part,  upon at least  seven (7) days'
written notice to Motorola  specifying  the date and amount of prepayment.  Such
notice  shall be  irrevocable  and the payment  amount  specified in such notice
shall be due and  payable  together  with  accrued  interest to such date on the
principal  amount being  prepaid.  The principal  amount prepaid for any Advance
which has not become  part of a Loan shall be  $10,000 or an  integral  multiple
thereof or the total remaining amount outstanding.  In the case of prepayment of
any Loan, the principal  amount prepaid shall be the total  remaining  principal
amount of such Loan.

         2.3      Effect of Prepayment.   Any prepayment shall be applied to the
                  --------------------
installments of principal in inverse order of maturity. Any prepayment shall not
relieve  you from  the  obligation  of  paying  the  current  or any  succeeding
installment  until the  Credit is repaid  in full.  Amounts  prepaid  may not be
reborrowed.

         2.4      Maximum Interest Rate and Amount. Under no circumstances shall
                  --------------------------------
you or any  Obligor be  required  to pay  Motorola a rate or amount of  interest
(together  with all  fees and  charges  which  are  treated  as  interest  under
applicable law) that exceeds that permitted by applicable law. If any overcharge
occurs,  (a) it is  inadvertent,  (b) you will  immediately  notify  Motorola in
writing of such  overcharge,  and (c) the overcharge  will be returned to you or
credited to principal, as Motorola may elect.

                        3. Representations and Warranties

         In order to induce  Motorola to enter into the Agreement and to provide
you with the Credit, you hereby represent and warrant to Motorola the following,
except as  otherwise  disclosed  to  Motorola in writing  concurrently  with the
execution of the Agreement:

         3.1 Status.  You are duly incorporated or formed,  and validly existing
             ------  
under the laws of the state of  incorporation  or formation.  You have the power
and authority and the legal right to own and operate your property, to lease the
property  you operate,  and to conduct the  business in which you are  currently
engaged  and in which you  propose to  engage,  (b) are in  compliance  with all
Requirements  of Law except to the extent that the  failure to comply  therewith
could not, in the  aggregate,  have a material  adverse effect on your business,
operations,  assets (taken in the aggregate) or financial  condition,  and could
not materially  adversely affect your ability to perform your obligations  under
the Agreement,  and (c) have qualified to do business in all jurisdictions where
your  ownership,  lease or operation of property or the conduct of your business
requires such qualification or recording,  except to the extent that the failure
to so qualify could not, in the  aggregate,  have a material  adverse  effect on
your  business,  operations,  assets  (taken  in  the  aggregate)  or  financial
condition,  and could not  materially  adversely  affect your ability to perform
your obligations under any of the Agreements.

         3.2 Power and Authority.  You have the power, authority and legal right
             -------------------
to execute,  deliver and perform the Agreement and to borrow hereunder, and have
taken all necessary  action to authorize the Credit on the terms and  conditions
of this Agreement,  and to authorize the execution,  delivery and performance of
the  Agreement  and  the  related  documents   described   therein.   Where  any
Governmental Authority, including without limitation any PUC, requires consents,
filings or authorizations  prior to the Credit, you shall have obtained all such
consents,  filings  or  authorizations.  Other  than such  consents,  filings or
authorizations,  no consent or  authorization or filing with, or other act by or
with respect to any Governmental  Authority,  is required in connection with the
Credit  hereunder  or with the  execution,  delivery,  performance,  validity or
enforceability  of the  Agreement.  The  Agreement  has been duly  executed  and
delivered  and  constitutes  your  legal,  valid and binding  obligation,  which
obligation shall be enforceable  against you in accordance with the terms of the
Agreement,  except as  enforceability  may be limited by applicable  bankruptcy,
insolvency, reorganization, moratorium or similar laws affecting the enforcement
of creditors' rights generally and general equitable principles.

         3.3 No  Violations.  The  execution,  delivery and  performance  of the
             -------------- 
Agreement and the use of the proceeds of the Credit (i) will not violate,  be in
conflict  with,  result  in a breach  of or  constitute  a  default  under,  any
Requirement of Law or any of your contractual obligations,  except to the extent
such violations,  in the aggregate,  could not have a material adverse effect on
(a) your  business,  operations,  assets  (taken in the  aggregate) or financial
condition,  or (b) your ability to perform your obligations under the Agreement,
and (ii) will not result in, or require,  the creation or imposition of any Lien
on any of your  properties  or revenues  pursuant to any  Requirement  of Law or
contractual  obligation,  other  than  pursuant  to the  Agreement.  You  are in
compliance with the Employee  Retirement  Income Security Act of 1974 as amended
from time to time (ERISA),  and neither the execution nor the performance of the
Agreement by you will result in any violation of ERISA. Any benefit plan that is
subject to ERISA has been properly  accounted for in your  Financial  Statements
attached to the Credit Agreement.

         3.4 No Pending Actions. No litigation,  investigation or proceedings of
             ------------------
or before any  arbitrator  or  Governmental  Authority  is pending,  or, to your
knowledge  is  threatened,  against you or,  against any of your  properties  or
revenues  (a)  with  respect  to  the  Agreement  or  any  of  the  transactions
contemplated  thereby,  or (b)  which is  reasonably  expected  to be  adversely
determined,  and which, if adversely determined,  could,  individually or in the
aggregate, have a material adverse effect on your business,  operations,  assets
(taken in the aggregate) or financial condition.

         3.5      No Defaults.  You are not in default  under or with respect to
                  -----------
any  contractual  obligation  where such default could be materially  adverse to
your  business,  operations,  assets  (taken  in  the  aggregate)  or  financial
condition,  or which could  materially  and  adversely  affect  your  ability to
perform your obligations under the Agreement. No Default or Event of Default has
occurred and is continuing.

         3.6      Good Title.   Any of your leases are in full force and effect,
                  ----------
and you  enjoy  peaceful  and  undisturbed  possession  thereunder;  you  have a
recorded  title in fee  simple to all your  owned  real  property,  and good and
marketable title to all your other personal property.

         3.7      Taxes. You have filed or caused to be filed  all material  tax
                  -----
returns which are required by law to be filed,  and have paid all taxes shown to
be due and payable on said returns or on any assessment made by any Governmental
Authority  (other than those the amount or validity of which is currently  being
contested  in good faith by  appropriate  proceedings  and with respect to which
reserves in conformity  with GAAP have been provided on your books);  and no tax
Liens have been filed and, to your knowledge,  no claims are being asserted with
respect to any such taxes,  fees or other charges other than inchoate  Liens for
taxes not yet due.

         3.8      No Extending of Credit.   Neither  you  nor  any  guarantor is
                  ----------------------
engaged or will generally engage in the business of purchasing or selling Margin
Stock (as defined in Regulation G, T, U or X of the Board of Governors or of the
Federal Reserve System)  extending  credit for the purpose of purchasing  Margin
Stock.

         3.9      No Subsidiaries.   Except  as disclosed  on Exhibit "D" to the
                  ---------------
Credit  Agreement,  you have no  subsidiaries  and do not  control,  directly or
indirectly, any other business entity.

         3.10     Patents, Trademarks, etc.   You  own  or have the right to use
                  ------------------------
all of the patents, trademarks, permits, service marks, trade names, copyrights,
licenses and  franchises or rights with respect to the  foregoing  (collectively
"patents"),   necessary   for  the  conduct  of  your   business  as   presently
contemplated, without any known conflict with the rights of others.

         3.11     Information, Reports, etc.  All information, reports and other
                  -------------------------
papers and data  furnished  to  Motorola by you on or at any time after the date
hereof  are or will be,  at the time the  same are so  furnished,  complete  and
correct in all material respects;  and all projections  concerning your business
furnished by you, as  supplemented,  will be prepared or presented in good faith
by you and have a reasonable basis. No fact is known to you which materially and
adversely  affects or in the future may (so far as you can  reasonably  foresee)
materially  and adversely  affect the business,  operations,  assets (taken as a
whole) or your financial condition which has not been set forth in the Financial
Statements or in such information, reports, papers and data.

         3.12 Security Documents.  The provisions of the Agreement are effective
              ------------------ 
to create in favor of Motorola a legal, valid and enforceable  security interest
in all your  right,  title and  interest in the  Collateral  in which a security
interest may be created under Article 9 of the Uniform Commercial Code; and when
(i)  financing  statements  have been filed in the offices in the  jurisdictions
listed in Exhibit "E" to the  Agreement,  and (ii) except for any further filing
or taking of possession  which may be required under Section 9-306 of the UCC in
order to perfect a security  interest  in  proceeds  of the  Collateral  and any
taking of possession  which may be required  under the UCC in order to perfect a
security  interest in  instruments,  the Agreement will create and grant a fully
perfected  first Lien on, and  security  interest in the  Collateral  (including
proceeds) in which a security  interest may be perfected  under Article 9 of the
UCC.

         3.13 Governmental Regulation.  You hold sufficient FCC licenses for the
              -----------------------
conduct  of your  business  in each area in which  you  currently  conduct  your
business.


         3.14 Assumed Names.  You are not doing business under any fictitious or
              -------------
 assumed names, except as disclosed in Exhibit "F" to the Agreement.

         3.15 Principal Place of Business.   Your  chief  executive  office  and
              ---------------------------
principal place of business are located at the notice address shown next to your
signature block on the Credit Agreement.  Your books and records with respect to
the Collateral are kept at this address.

         3.16 Environmental and Safety Matters.   You  are  in compliance in all
              --------------------------------
material respects with all federal, state, local and other statutes, ordinances,
orders,  judgments,   rulings  and  regulations  relating  to  the  environment,
environmental  regulation  or  control,  employee  health  and  safety,  or  the
generation,  use,  storage,  disposal or  transportation  of toxic or  hazardous
materials, substances or wastes (collectively, "Environmental Laws").

                            4. Affirmative Covenants

         You hereby agree that,  so long as the Credit  remains in effect or any
amounts remain  outstanding and unpaid or any other amount is owing to Motorola,
you shall do the following.

         4.1      Financial Reporting.
                  -------------------

                  4.1.1. As soon available, but not later than 90 days after the
end of each fiscal  year,  commencing  with the fiscal year ending  December 31,
1998, you shall provide Motorola with a copy of the audited consolidated balance
sheets of the  Borrower  and the  Guarantors  as at the end of such year and the
related audited consolidated statements of income, stockholders' equity and cash
flows for such fiscal year,  setting forth in each case in comparative  form the
figures for the previous year, and accompanied by the opinion of Arthur Andersen
LLP or another nationally  recognized  independent public accounting firm, which
report shall state that such consolidated  financial  statements present fairly,
in all material respects, the financial position, results of operations and cash
flows for the  periods  indicated  in  conformity  with GAAP  applied on a basis
consistent with prior year.

                  4.1.2 As soon as  available,  but not later than 45 days after
the end of each of the first three fiscal quarters of each year, commencing with
the fiscal quarter ending on June 30, 1998, a copy of the unaudited consolidated
balance  sheets of the Borrower and the Guarantors as of the end of such quarter
and the related consolidated statements of income, stockholders' equity and cash
flows for the period  commencing  on the first day and ending on the last day of
such quarter,  and  certified by an  appropriate  Responsible  Officer as fairly
presenting,  in all material  respects,  in accordance with GAAP (except for the
absence of  footnote  disclosure),  the  financial  position  and the results of
operations of the Borrower and the Guarantors.

                  4.1.3. As soon available, but not later than 90 days after the
end of each fiscal  year,  commencing  with the fiscal year ending  December 31,
1998, you shall provide  Motorola with a copy of the unaudited  balance sheet of
the Borrower as at the end of such year and the related unaudited  statements of
income, owners equity and cash flows for such fiscal year, setting forth in each
case in comparative  form the figures for the previous year, and certified by an
appropriate Responsible Officer as fairly presenting,  in all material respects,
in accordance with GAAP, the financial position and the results of operations of
the Borrower..

                  4.1.4 As soon as  available,  but not later than 45 days after
the end of each of the first three fiscal quarters of each year, commencing with
the fiscal  quarter  ending on June 30,  1998, a copy of the  unaudited  balance
sheet of the Borrower as of the end of such  quarter and the related  statements
of income,  owners equity and cash flows for the period  commencing on the first
day and ending on the last day of such quarter,  and certified by an appropriate
Responsible  Officer  as  fairly  presenting,   in  all  material  respects,  in
accordance  with GAAP  (except  for the  absence of  footnote  disclosure),  the
financial position and the results of operations of the Borrower.

         4.2      Certificates: Other Information.
                  -------------------------------

                  4.2.1  Concurrently with the delivery of the items referred to
in Sections 4.1.1,  and 4.1.2 above,  you will deliver to Motorola a certificate
of the  independent  certified  public  accountants or of a Responsible  Officer
certifying  such  financial  statements or other items,  as the case may be, and
stating  that no Default or Event of Default  has  occurred  and is  continuing,
except as specified in such certificate.

Within  five (5) days  after the same are sent or  filed,  you will  deliver  to
Motorola (a) copies of all reports sent to the  stockholders  of American Mobile
Satellite  Corporation  covering such matters as are typically covered in annual
or quarterly  reports,  and (b) copies of each report on Form 8-K filed with the
Securities and Exchange Commission.

                  4.2.3 You shall  further  deliver  promptly to  Motorola  such
additional  financial and other  information as Motorola may reasonably  request
from time to time.

         4.3 Discharge Obligations. You will pay, discharge or otherwise satisfy
             ---------------------
in the  ordinary  course of  business  (a) all  Indebtedness,  and (b) all other
obligations to the extent such obligations exceed, in the aggregate, $1,000,000,
except,  in any such case,  to the extent that (i) the amount or validity of any
such Indebtedness or other obligation is currently being contested in good faith
by appropriate  proceedings,  (ii) appropriate  reserves in conformity with GAAP
have been  provided  on your  books,  and (iii) such matter does not involve any
risk of loss, forfeiture, or Lien on your assets.

         4.4  Continuation  of  Business;  Compliance.  You will (a) continue to
              ---------------------------------------
engage  in  business  of the same  general  type as now  conducted  by you,  (b)
preserve  and  maintain  in full force and effect  your  existence  as a general
partnership and your good standing under the laws of your State of organization,
(c)  preserve  and  maintain  in full force and effect  all  rights,  privileges
qualifications,  permits,  licenses and franchises necessary or desirable in the
normal  conduct  of your  business,  (d) use  your  reasonable  efforts,  in the
ordinary  course and consistent  with past  practice,  to preserve your business
organization and preserve the goodwill and business of the customers,  suppliers
and others having business  relations with you, and (e) preserve or renew all of
your registered trademarks,  trade names and service marks, the non-preservation
of which  could have a material  adverse  effect on your  business,  operations,
financial  condition,  or your  ability to perform  your  obligations  under the
Agreement.

         4.5    Maintenance of Collateral.  You will keep the Collateral in good
                -------------------------
 working order and condition, reasonable wear and tear excepted.

         4.6   Insurance.   You will  maintain  property insurance in amounts at
               ---------
least equal to the value of the Collateral with financially  sound and reputable
insurance companies. The policies shall be in writing and shall name Motorola as
loss payee, but only to the extent of the balance  outstanding from time to time
under the Agreement.  You will furnish to Motorola, prior to the initial funding
under the Agreement and thereafter upon written request,  full information as to
the insurance  carried.  In the event of loss  involving any of the  Collateral,
insurance  proceeds will be used to repair (if you and Motorola agree in writing
that  repairing  the damage is  feasible)  the damaged  Collateral.  If Motorola
determines in good faith that the Collateral cannot be timely repaired, then all
such insurance  proceeds shall be paid directly to Motorola,  for application to
the amounts outstanding hereunder,  unless Motorola agrees to accept replacement
Collateral.

         4.7  Records; Access.  You will keep proper books of record and account
              ---------------
in which  full,  true,  and  correct  entries  in  conformity  with GAAP and all
Requirements  of Law shall be made to reflect truly the  financial  position and
the  results  of your  operations.  Upon  reasonable  notice,  you  will  permit
representatives  of Motorola to visit and inspect the Collateral and any of your
properties  and examine and make  extracts  from and copies of any of your books
and records at any  reasonable  time  during  normal  business  hours and as may
reasonably  be desired by Motorola,  and to discuss your  business,  operations,
properties and financial and other condition.

         4.8  Notices.  You  will, within the time periods set forth below, give
              -------
written notice to Motorola of the occurrence of any of the following:

                  4.8.1 within five (5) Business Days of the occurrence thereof,
any Default or Event of Default;

                  4.8.2 within five (5) Business Days of the occurrence thereof,
any (i) material  default or any material event of default under any contractual
obligation of yours which is material in relation to your business,  operations,
assets  (taken in the  aggregate)  or  financial  condition  or (ii) any  claim,
litigation,  investigation, or proceeding which arises at any time involving you
which is  reasonably  anticipated  to be  adversely  determined  and  which,  if
adversely  determined,  would have a material  adverse  affect on your business,
operations, assets (taken in the aggregate) or financial condition;

                  4.8.3 within five (5) Business Days of the occurrence thereof,
any material adverse change in your business,  operations,  assets (taken in the
aggregate) or financial condition;

                  4.8.4 not less  than  thirty  days  prior  to  the  occurrence
thereof,  the  movement of any portion of the  Collateral,  which  notice  shall
identify  the  jurisdiction  (as to State and  county)  into  which each item of
Collateral (identified by serial number) shall be moved;

                  4.8.5  not less than  thirty  days  prior  to  the  occurrence
thereof,  the relocation of your principal  place of business or chief executive
offices to any location; and

                  4.8.6  not less  than  thirty  days  prior  to  the occurrence
thereof,  the  change of your name or  corporate  structure,  or your use of any
fictitious name or assumed name.


Each notice pursuant to Sections 4.8.1, 4.8.2, and 4.8.3 shall be accompanied by
a statement of a Responsible  Officer  setting  forth details of the  occurrence
referred  to therein and  stating  what action you propose to take with  respect
thereto.  Prior to the occurrence of any event  specified in to Sections  4.8.4,
4.8.5,  or 4.8.6 you shall also  execute and deliver to Motorola  any  documents
requested  by Motorola to maintain  the  continuous  perfection  and priority of
Motorola's Liens and security interests.


                              5. Negative Covenants

         You hereby agree that, so long as the Credit  remains  outstanding  and
unpaid or any other amount is owing by you to Motorola, you will comply with the
following unless Motorola has consented in writing to your failure to so comply:


         5.1      Liens.  You will not create, incur, assume or suffer to exist,
                  -----
any Lien upon any of your property, assets, income or profits, whether now owned
or hereafter acquired except:


                  5.1.2 existing  Liens,  as  have  been disclosed in writing to
Motorola prior to the date hereof;

                  5.1.2 Liens for taxes not yet due or which are being contested
in good faith and by  appropriate  proceedings  if (a)  adequate  reserves  with
respect  thereto are  maintained on your books in accordance  with GAAP (b) such
matter does not involve a risk of forfeiture;

                  5.1.3 carriers',  warehousemen's,  mechanics',  materialmen's,
repairmen's,  or other like Liens  arising in the  ordinary  course of  business
which are not  overdue  for a period of more than  thirty (30) days or which (a)
are being contested in good faith and by appropriate proceedings,  (b) have been
appropriately  reserved against,  and (c) carry no risk of forfeiture or loss of
legal rights;

                  5.1.4  pledges  or  deposits  in  connection   with  workmen's
compensation,  unemployment insurance, and other social security legislation, in
the ordinary course of your business;

                  5.1.5  deposits  to  secure  the  performance  of  bids, trade
contracts  (other than for  Indebtedness),  leases (other than capital  leases),
statutory  obligations,  surety and appeal  bonds,  performance  bonds and other
obligations of a like nature incurred in the ordinary course of business;

                  5.1.6 easements, rights-of-way, restrictions and other similar
encumbrances  incurred  in  the  ordinary  course  of  business  which,  in  the
aggregate,  are  not  substantial  in  amount,  and  which  do not  in any  case
materially  detract from the value of the property  subject thereto or interfere
with the ordinary conduct of your business;

                  5.1.7  Liens in favor of Motorola under the Agreement;

                  5.1.8 Liens on real or personal  property  given to secure the
purchase  price  thereof,  for  property  acquired  in the  ordinary  course  of
business; and

                  5.1.9 other Liens  which do  not attach to the Collateral, not
exceeding $15,000,000 in the aggregate at any time.

         5.2  Change  of  Status.   You  will  not  enter  into  any  merger  or
              ------------------
consolidation  or  amalgamation,  will not  liquidate,  wind up or dissolve  (or
suffer any  liquidation  or  dissolution),  and shall not convey,  sell,  lease,
assign,  transfer  or  otherwise  dispose of any of your  property,  business or
assets  (including,  without  limitation,  receivables and leasehold  interests)
whether now owned or hereafter acquired (except the sale or other disposition of
assets for good  consideration  in the ordinary  course of business) if any such
transaction   might  materially   adversely  affect  your  business,   financial
condition, or your ability to perform your obligations under the Agreement.

         5.3   Organization  and  Governing  Documents.   You  will  not  amend,
               ---------------------------------------
supplement or otherwise  modify or waive  compliance  with any provision of your
articles of  incorporation  or by-laws if you are a corporation,  or partnership
agreement,  if a partnership,  if such  amendment,  supplement,  modification or
waiver would have a material adverse effect on your business,  operation, assets
(taken in the aggregate) or financial  condition,  or would otherwise materially
and  adversely  affect  your  ability  to  perform  your  obligations  under the
Agreement.

         5.4      FCC License.  Except  for  the performance of agreements which
                  -----------
predate the  Agreement,  you will not  transfer or attempt to transfer  your FCC
licenses to operate any system to any Person other than in the  ordinary  course
of business.

         5.5      Transactions with Affiliates.   You  will  not  use any of the
                  ----------------------------
proceeds hereunder, or engage in the purchase of goods and services, directly or
indirectly, with any Affiliate on any basis other than arms'-length.

         5.6      Subsidiaries.   You  will  not  form,  create,  or acquire any
                  ------------
 subsidiaries except those identified on Exhibit "D" to the Agreement.

         5.7      Collateral.  You  will  not at any time place or locate any of
                  ----------
the Collateral,  or cause or permit any of the Collateral to be located,  at any
place other than a Filing Jurisdiction.





                         6. Events of Default; Remedies

         6.1      Events of Default.  Any  of  the  following  events  shall  be
                  -----------------
considered  an Event of  Default,  upon the  occurrence  of which  Motorola  may
exercise  all  remedies  available  at law  together  with all other  rights and
remedies provided under the terms of this Section VI:

                  6.1.1  You  shall fail  to pay any principal or interest under
the Note  within  five (5) days of the due date,  or shall fail to pay any other
amount  payable under the Agreement  within ten (10) days after  Motorola  gives
notice to you of such failure.

                  6.1.2  A  representation  or  warranty  made  by  you  in  the
Agreement,  or which is contained in any  certificate,  document or financial or
other statements furnished at any time under or in connection  therewith,  shall
prove to have been incorrect in any material  respect on or as of the date made;
provided  that if such default is capable of being cured,  you shall have thirty
days after notice of such default to remedy the default.

                  6.1.3 You shall default in the  performance  of any obligation
pursuant to Section 4.8 or Section 5.7 hereof.

                  6.1.4 You shall default in the  observance or  performance  of
any other  covenant or  obligation  contained  in this  Agreement or any exhibit
hereto,  and such default shall continue  unremedied for a period of thirty days
after Motorola giving notice to you of such default.

                  6.1.5  You shall (a) default  in  any payment of the principal
of or the interest on any item of Indebtedness  covered by subsection (i) of the
definition of  "Indebtedness"  beyond the grace period,  if any, provided in the
instrument  or  agreement  under which such  Indebtedness  was  created;  or (b)
default in the  observance or  performance  of any other  agreement or condition
relating to any such  Indebtedness  or contained in any  instrument or agreement
evidencing, securing or relating thereto.

                  6.1.6  The occurrence of any of the following:

                           (i)   you  shall  commence  any  case, proceeding  or
other action under any existing or future law of any  jurisdiction,  domestic or
foreign,  relating  to  bankruptcy,  insolvency,  reorganization  or  relief  of
debtors,   (a)  seeking  to  have  an  order  for  relief  entered,  or  seeking
reorganization,  arrangement, adjustment, winding-up, liquidation,  dissolution,
composition  or other relief with  respect to you or your debts,  or (b) seeking
appointment of a receiver,  trustee,  custodian or othe similar official for you
or for all or any substantial  part of your assets;  or you shall make a general
assignment for the benefit of your creditors;

                           (ii)  there  shall be commenced against you any case,
proceeding or other action of a nature referred to in clause (i) above which (a)
results  in the  entry of an  order  for  relief  or any  such  adjudication  or
appointment and (b) remains  undismissed,  undischarged or unbonded for a period
of thirty days;

                           (iii) there shall be commenced  against you any case,
proceeding  or  other  action  seeking  issuance  of a  warrant  of  attachment,
execution,  distraint or similar process against all or any substantial  part of
your  assets,  which  results in the entry of an order for any such relief which
shall not have been vacated,  discharged,  or stayed or bonded  pending  appeal,
within thirty days from the entry thereof;

                           (iv)  you shall take any action in furtherance of, or
indicating your consent to, approval of, or acquiescence in, any of the acts set
forth in clause (i), (ii), or (iii) above;

                           (v)   you  shall generally not pay your debts as they
become due or shall be unable to pay such debts,  or shall admit in writing your
inability to pay such debts; or

                           (vi) the  occurrence of any of the  foregoing  events
with respect to any Guarantor of your obligations to Motorola.

                  6.1.7  One  or  more  judgments  or  decrees  shall be entered
against you involving in the aggregate a liability (not paid or fully covered by
insurance) of $50,000.00  or more,  and all such  judgments or decrees shall not
have been vacated,  discharged, or stayed or bonded pending appeal within thirty
days from the entry thereof.

                  6.1.8 Any license  materially  necessary  for your  continuing
operation  of  your  business  or  any  other  material   authorization  of  any
Governmental  Authority  with respect to the conduct by you of your business and
operations,  or with respect to the Agreement,  (i) shall not be obtained as and
when  required to permit you to conduct your  business as then being  conducted,
and which has a  material  adverse  effect on your  financial  condition  or and
adverse effect on your ability perform your obligations under the Agreement;  or
(ii) shall  cease to be in full force and effect.  A license  shall be deemed to
cease to be in full force and effect (a) when an order  revoking or  terminating
said  license  shall be issued  and such  order is no longer  subject to further
administrative and judicial review, or (b) when any Government  Authority having
jurisdiction  over any such license  shall,  prior to the  termination  thereof,
decide  not to renew  such  license  and such  decision  shall not be subject to
further administrative or judicial review.

                  6.1.9  There  shall  occur  a  default   under  any  Guarantee
Agreement executed in connection with the Credit Agreement.

                  6.1.10  You  shall  fail  to  pay any undisputed amount due to
Motorola on open account within thirty (30) days from an invoice  therefor,  and
such failure shall continue for ten (10) days after notice thereof by Motorola.

         6.2  Remedies.
              --------
 
                  6.2.1  Acceleration.   Upon  the  occurrence  and  during  the
                         ------------
continuance  of any Event of  Default,  in  addition  to all rights of a secured
creditor  under  Article 9 of the UCC,  (a) if such event is an Event of Default
specified in clause (i) or (ii) of Section 6.1.5 above, all amounts owing by you
under this  Agreement and under any other account  relationship  between you and
Motorola shall immediately become due and payable,  and (b) if such event is any
other Event of Default,  then Motorola may, by notice to you declare all amounts
owing by you under this  Agreement or under any such other account  relationship
to be due and  payable,  whereupon  the same  shall  immediately  become due and
payable.

                  6.2.2  Possession  of  Collateral.  You agree,  if an Event of
                         --------------------------
Default  shall be existing and upon  Motorola's  request,  to assemble,  at your
expense, all equipment and other property  constituting a part of the Collateral
at a convenient place acceptable to Motorola and to pay all costs of Motorola of
collection  of  all  amounts  due,  and  enforcement  of all  rights  hereunder,
including  reasonable  attorney's fees and legal  expenses,  and expenses of any
repairs to any realty on other  property to which any of such  equipment  may be
affixed.  Upon an Event of Default Motorola may, to the fullest extent permitted
by applicable law, without notice,  advertisement,  hearing or process of law of
any kind, enter upon any premises where any of the equipment  constituting  part
of the  Collateral  may be  located  and  take  possession  of and  remove  such
equipment.

                  6.2.3 Sale of Collateral.  Without  limiting the generality of
                        ------------------ 
the  foregoing,  Motorola  shall have all the rights and  remedies  of a secured
party under the UCC or other  applicable  law and  Motorola may sell and deliver
any or all  Collateral  held by or for it at public or private  sale,  for cash,
upon  credit,  for future  delivery or  otherwise,  at such prices and upon such
terms as Motorola deems  advisable,  in its sole discretion  and/or collect,  or
enforce the  collection of, the  Collateral.  Motorola may buy any or all of the
Collateral at any such sale.

                  6.2.4  Standard of Care.   Motorola  shall exercise reasonable
                         ----------------
care at all times in the custody and  preservation  of any of the  Collateral in
its possession, and shall be deemed to have exercised such reasonable care if it
takes such action for the purpose you reasonably request in writing.

                  6.2.5  Advances  to  Protect Collateral.   Motorola  may  (but
                         --------------------------------
shall not be obligated to) make  advances to preserve,  protect or obtain any of
the Collateral, including advances to pay taxes, insurance and the like, and all
such advances shall become a part of the Obligations owing to Motorola hereunder
and shall be repayable to Motorola with  interest  thereon from the date of such
advance until paid at the Default Rate set forth in this Agreement.

                  6.2.6  Notices, etc. Waived.   Except as expressly provided in
                         --------------------
this  Section VI, you  expressly  waive,  to the  fullest  extent  permitted  by
applicable law, presentment,  demand,  protest, any and all notices of any kind,
advertisement,  hearing or process of law in  connection  with the  exercise  by
Motorola of any of its rights and remedies  upon the  occurrence  of an Event of
Default. If any notification of intended disposition of any of the Collateral is
required by law, such  notification,  if mailed,  shall be deemed reasonably and
properly  given if mailed at least five days  before such  disposition,  postage
prepaid,  addressed to Company  either at the address  shown  below,  or at your
address appearing on the records of Motorola.

                  6.2.7  Setoff.  If any amount  owing by you to Motorola  shall
                         ------
have become due and payable (by acceleration or otherwise),  Motorola shall have
the right, in addition to all other rights and remedies available to it, without
notice to you, to setoff  against such  amounts any debt owing from  Motorola to
you and any other  funds held by  Motorola  in any manner for your  account,  it
being  understood  that the  Escrowed  Funds will in no event be  available  for
setoff  under this  provision.  Such right shall exist  whether or not  Motorola
shall have given notice or made any demand  hereunder,  whether or not such debt
owing to you is  matured  or  unmatured,  and  regardless  of the  existence  or
adequacy  of any  collateral,  guaranty or any other  security,  right or remedy
available  to  Motorola.  You  hereby  consent  to  and  confirm  the  foregoing
arrangements and confirm Motorola's rights of setoff.

                  6.2.8 Application of Proceeds.   Any  proceeds  of  any of the
                        -----------------------
Collateral  shall be applied by Motorola  toward the repayment of the Credit and
any of your other  obligations  to Motorola in the  following  priority:  first,
towards expenses  incurred in connection with the exercise of rights or remedies
with  respect  to any of the  Collateral  (including  reasonable  fees and legal
expenses);  second,  to accrued  interest;  and third,  to the  installments  of
principal in inverse order of maturity thereof

                  6.2.9 No Further Advances.  During the continuance of an Event
                        -------------------
of Default, Motorola shall have no obligation to make Advances to you.

         6.3 General  Authority.  Subject to any  requirements  for governmental
             ------------------ 
approval,  upon the  occurrence  and  during  the  continuance  of any  Event of
Default,  the rights,  powers and  privileges  provided in this  Section and all
other  remedies  available to Motorola  under this Agreement or by statute or by
rule of law may be  exercised  by Motorola at any time from time to time whether
or not the Credit  shall be due and payable,  and whether or not Motorola  shall
have instituted any foreclosure or other action for enforcement. For the purpose
of carrying out the provisions and exercising the rights,  powers and privileges
granted  by this  Section  6, you  hereby  irrevocably  constitute  and  appoint
Motorola  your true and lawful  attorney-in-fact  to  execute,  acknowledge  and
deliver any  instruments  and do and perform any acts such as are referred to in
this Section 6 in your name on your behalf in accordance with this Agreement and
any statute or rule of law.  This power of attorney is a power  coupled  with an
interest and cannot be revoked.

         6.4 Expenses.  In addition to all other sums due to Motorola,  you will
             --------
pay Motorola, on demand, all reasonable costs and expenses (including reasonable
attorneys' fees and  disbursements  and court costs) incurred by Motorola at any
time  in  connection  with  (i)  the  enforcement  or  collection  of any of the
Obligations, (ii) attempts to obtain possession of, liquidate, or collect on any
of the Collateral,  (iii) the enforcement,  protection or preservation of any of
Motorola's  rights or remedies  under this  Agreement,  or (iv) the  completion,
construction,  installation, operation, management or maintenance of any of your
systems by Motorola, its designee, or a receiver or trustee, whether pursuant to
this Section 6 or otherwise,  or (v) the prosecution of any action or proceeding
brought  against you or any of the Guarantors  concerning any matter arising out
of or  connected  with  this  Agreement  or any  Collateral,  including  without
limitation any actions  arising in, arising under or related to a case under the
Bankruptcy  Reform Act of 1978, as amended,  or any successor statute or similar
state law. All such amounts shall be payable on demand and shall accrue interest
at the Default Rate from the time of demand until paid in full. All such amounts
shall be part of the  obligations  due under the Agreement  and payment  thereof
shall be secured by all the Collateral.

                             7. Security Provisions

Your Obligations in connection with the Credit and this Agreement are secured by
the Collateral.  These Obligations  include,  but are not limited to, principal,
interest,  premium,  charges,  attorneys'  fees,  assessments,  costs and future
Advances,  whether  direct or  indirect,  contingent  or  absolute,  matured  or
unmatured.  You hereby grant to Motorola a continuing  security  interest in and
lien on the Collateral.

                  7.1      Priority of Security Interest.  The security interest
                           -----------------------------
and lien granted by Borrower to Motorola  pursuant to the Agreement is and shall
be a perfected,  first priority continuing and indefeasible security interest in
the Collateral subject only to any Liens authorized by Motorola in writing.

                          8. Requirements for Advances

         In order to draw down an Advance under the Credit  Agreement,  you must
have satisfied each of the following conditions precedent:

         8.1  No  Default  or  Event  of  Default  shall  have  occurred  and be
continuing.

         8.2  You   will  have   supplied   Motorola   with   such  articles  of
incorporation, partnership agreements, by-laws, certificates of good standing or
qualification to do business,  opinions of counsel,  environmental certificates,
FCC licenses or compliance  information,  resolution,  incumbency  certificates,
insurance  documents,  and other "due  diligence"  information  as Motorola  may
reasonably request.

         8.3  All financing statements, deliveries (including without limitation
share  certificates),  and other  actions  reasonably  necessary  to assure  the
enforceability  of this  Agreement and the  perfection  of  Motorola's  security
interests in the Collateral and in the Equity Interests shall have been taken.

         8.4  All proceedings,  documents, and other legal matters pertaining to
this  Agreement  and the  transactions  contemplated  herein shall be reasonably
satisfactory in form and substance to Motorola and to Motorola's counsel.

         8.5  The  requested  Advance, when  added  to  the  existing  principal
balance  outstanding,  must not exceed the maximum amount of Credit set forth in
the Credit Agreement. Amounts repaid may not be re-borrowed.

                                 9. Other Terms

         9.1      Amendments.  No amendment,  supplement or modification of this
                  ----------
Agreement shall be binding on any party hereto unless made in writing and signed
by a duly authorized representative of such party.

         9.2  Notices.  All  notices,  requests  and  demands  to  or  upon  the
              -------
respective  parties  hereto to be  effective  shall be in  writing  and,  unless
otherwise expressly provided herein,  shall be deemed to have been duly given or
made (i) when delivered by hand or (ii) the following  Business Day when sent by
overnight delivery service,  by courier,  or (iii) the same day when transmitted
by facsimile and a confirmation  of transmission  printed by sender's  facsimile
machine.  A copy of any notice given by facsimile also shall be mailed,  postage
prepaid,  to the addressee.  Notices to the  respective  parties hereto shall be
addressed to the parties at their addresses shown on the Credit Agreement.

         9.3      Waiver.
                  ------

                  9.3.1  Waiver by Consent.  Motorola may execute and deliver to
                         -----------------
you  from  time to  time,  a  written  instrument  waiving,  on such  terms  and
conditions as Motorola may specify in such  instrument,  any of the requirements
of the Agreement or any Default or Event of Default and its consequences. In the
case of any waiver, you and Motorola shall be restored to their former positions
and rights  hereunder and any Default or Event of Default waived shall be deemed
to be  cured  and  not  continuing;  but no  such  waiver  shall  extend  to any
subsequent or other Default or Event of Default, or impairment thereof.

                  9.3.2 No Implied Waiver: Rights are Cumulative. The failure to
                        ----------------------------------------
exercise or the delay in exercising, on the part of Motorola, any right, remedy,
power or privilege  under the Agreement,  shall not operate as a waiver thereof;
the single or partial  exercise of any right,  remedy,  power or privilege under
the Agreement  shall not preclude any other or further  exercise  thereof or the
exercise of any other right, remedy, power or privilege.  The rights,  remedies,
powers and  privileges  herein  provided are cumulative and not exclusive of any
rights, remedies, powers and privileges provided by law.

         9.4 Survival.  All  agreements,  covenants, representations, warranties
             --------
and  indemnities  made under the Agreement and in any document,  certificate  or
statement delivered pursuant thereto or in connection herewith shall survive the
execution and delivery of this Agreement and the Note and the making of Advances
regardless of any investigation made by Motorola.

         9.5  Indemnity.  You hereby  indemnify  Motorola  against  any  losses,
              ---------
claims,  penalties,   expenses,   actions,  suits,   obligations,   liabilities,
documentary stamp or transfer taxes (if applicable) and liens (and all costs and
expenses,   including   reasonable   attorney's   fees  incurred  in  connection
therewith),  which Motorola has sustained or incurred or may sustain or incur in
connection with any of the Collateral,  or the enforcement of the Agreement,  or
as a consequence  of any default by you in the  performance or observance of any
covenant or condition contained in this Agreement, including without limitation,
the breach of any representation or warranty, any failure by you to pay when due
(by acceleration or otherwise) any principal,  interest, fee or any other amount
due hereunder, and any failure to comply with all applicable Requirements of Law
(collectively, "Claims"), except for any Claims determined by a court in a final
order  to have  been  caused  by  Motorola's  gross  negligence  or  intentional
misconduct.  Your  obligations  under  this  Section  9.5  shall  be part of the
obligations  secured  hereby and shall be secured by the  Collateral.  You agree
that upon written  notice by Motorola of the assertion of any Claims,  you will,
at  Motorola's  option,  either  assume full  responsibility  for, or  reimburse
Motorola for the reasonable costs and expenses of, the defense  thereof,  except
for any Claims caused by Motorola's gross negligence or intentional  misconduct.
The provisions of this Section 9.5 shall survive the term of this Agreement.

         9.6      Assignment.  This Agreement shall be binding upon and inure to
                  ----------
the benefit of you,  Motorola,  and their  respective  permitted  successors and
assigns.  This  Agreement is not  assumable by any  successor or  transferee  of
yours;  you may not assign or transfer any of your rights under this  Agreement,
or delegate  any of your duties  under this  Agreement,  without  prior  written
consent of Motorola.  Motorola may assign this Agreement,  without notice to you
or your consent;  provided that so long as no Event of Default exists,  Motorola
shall not assign this Agreement to any entity that competes with you.

9.7   Counterpart   Documents.   This   Agreement   may  be   executed   by  one
- ---------------------  or more of the parties to this Agreement in any number of
separate  counterparts  and all of said  counterparts  taken  together  shall be
deemed to constitute one and the same instrument.

         9.8      FCC/PUC Approvals.   The  exercise  of any rights hereunder by
                  -----------------
Motorola which may require  FCC/PUC  approval shall be subject to obtaining such
approval.  Pending obtaining any such FCC/PUC approval, you will not do anything
with respect to such rights which is contrary to the interests of Motorola.

         9.9      Severability.  If any  provision of this Agreement is found to
                  ------------
be unenforceable for any reason whatsoever,  such provision shall be deemed null
and void to the extent of such  unenforceability  but shall be deemed  separable
from and shall not invalidate any other provision of this Agreement.

         9.10     Captions. Captions to the various paragraphs of this Agreement
                  --------
are  provided  for  convenience  only  and  shall  not be used to  construe  the
provisions of this Agreement.

         9.11     Review of Information.  You  acknowledge  and  agree  that any
                  ---------------------
review or analysis by Motorola of financial information,  operating information,
marketing  data or other  information  provided  to  Motorola  by you or on your
behalf at any time is and shall be conducted  solely for Motorola's  benefit and
internal  use and  that  Motorola  is under  no duty or  obligation  to make the
results of such review or analysis  available to you.  You are not relying,  and
will not rely, on Motorola for financial or business advice.

         9.12     No Joint Venture; No Benefit to Non-Parties.  Nothing  in this
                  -------------------------------------------
Agreement shall be deemed to constitute any kind of  partnership,  joint venture
or fiduciary relationship between or among Motorola and any Obligor(s); further,
the  Agreement  is not intended to benefit any Person that is not a party to the
Agreement.






                                   EXHIBIT B




Amount: $10,000,000                                          Date: June 17, 1998


                                 PROMISSORY NOTE


         FOR VALUE RECEIVED,  the  undersigned  (the "Borrower" or "you") hereby
promises  to  pay  to  the  order  of  Motorola  Inc.  ("Motorola")  a  Delaware
corporation,  at its principal offices at 1303 East Algonquin Road,  Schaumburg,
Illinois  60196,  the lesser of (i) the  principal  sum of Ten  Million  Dollars
($10,000,000), or (ii) the aggregate unpaid principal amount of Advances made by
Motorola to the Borrower  under the Credit  Agreement  (the "Credit  Agreement")
dated as of June 17, 1998  between the  Borrower  and  Motorola,  together  with
interest  on  the  entire  principal  balance  from  time  to  time  outstanding
hereunder.

         Interest  shall  accrue  as of the  date  of this  Note  and  shall  be
calculated on the amount of each Advance outstanding from time to time at a rate
per annum  equivalent to the Applicable  Interest Rate (as defined in the Credit
Agreement).  Interest shall be payable quarterly in arrears.  The first interest
payment shall be due on the first day of the calendar  quarter  first  following
the date hereof on which any amounts are outstanding hereunder,  and on the date
of prepayment in full of any balance due hereunder. Interest shall be calculated
on a 365/366 day year basis for actual days elapsed.  Upon the  occurrence of an
Event of  Default,  the  interest  rate shall be  increased  by a further  three
percent (3%) per annum above the rate  otherwise  applicable  or (if lesser) the
maximum  rate  permitted  by law.  In no event  shall the holder of this Note be
entitled to claim any sum or rate of  interest in excess of the maximum  allowed
by law. Any payment in excess of such  maximum sum or amount of interest  shall,
at the option of Motorola,  be applied to reduce outstanding  principal or shall
be refunded to Borrower.

         Motorola  shall  record  on  its  books  or  records  all  payments and
prepayments of principal and interest,  the principal  balance from time to time
outstanding  and the respective  dates and maturity  dates  thereof.  The record
thereof,  whether shown on such books or records,  shall be prima facie evidence
as to all amounts owing under this Note; provided,  however, that the failure of
Motorola to record any of the foregoing or any error in such notation  shall not
limit or otherwise affect the obligation the Borrower to repay the entire Credit
under the Credit Agreement together with accrued interest thereon.

         Principal  shall be  payable  in  accordance  with the  terms of Credit
Agreement.

         This Note is the Promissory Note referred to in, and issued under,  the
Credit  Agreement,  and Motorola is entitled to all of the benefits provided for
therein; reference is hereby made to the Credit Agreement for a statement of all
such benefits. Capitalized terms not defined in this






Note shall have the meanings assigned to such terms  in the Credit Agreement and
the exhibits attached thereto.  Without limiting that reference,  Motorola shall
be entitled  to recover its  attorney's  fees and costs in  connection  with any
actions or proceedings  taken to collect this Note after any Event of Default as
detailed in the Credit Agreement.

         This Note shall be  subject to, governed and construed according to the
laws of the State of Illinois,  without regard to its provisions on the conflict
of laws. Whether or not executed in another jurisdiction, this Note shall become
effective upon delivery to Motorola at its headquarters in Illinois.

         The  maker  hereby  waives  notice, protest, presentment, and notice of
dishonor  to  the  full  extent   permitted  by  law.  This  Note  evidences  an
indebtedness incurred in connection with a commercial  transaction rather than a
consumer or household debt.

         YOU AND MOTOROLA AGREE THAT ANY CLAIM, COUNTERCLAIM, SETOFF, OR DEFENSE
RELATING IN ANY WAY TO THIS NOTE, OR TO THE MATTERS AND TRANSACTIONS GIVING RISE
TO THE ADVANCES  AND  INDEBTEDNESS  EVIDENCED  BY THIS NOTE,  SHALL BE HEARD AND
DETERMINED BY A COURT WITHOUT A JURY.




                                      ARDIS COMPANY


                                      By:
                                         ---------------------------------------
                                         Walter V. Purnell

                                      Title: 
                                            ------------------------------------




















                                    EXHIBIT C

               LIST OF GUARANTORS AND FORM OF GUARANTEE AGREEMENT

                                   Guarantors

                      American Mobile Satellite Corporation
                            AMSC Acquisition Company
                           AMSC Subsidiary Corporation






                                     FORM OF
                               GUARANTEE AGREEMENT


         This Agreement ("Guarantee Agreement") is effective as of June 17, 1998
and is given by  ____________("Guarantor" or "you") to Motorola Inc., a Delaware
corporation ("Motorola").


                                    Recitals

         A.       Guarantor is a __________ of ARDIS Company, a New York general
partnership (hereinafter referred to as the "Borrower");

         B.       Pursuant  to  a Credit Agreement of even date between Motorola
and the  Borrower  (the  "Credit  Agreement"),  Motorola  has  agreed to provide
financing  to enable the  Borrower  to  purchase  equipment  and  services  from
Motorola;

         C.       The   Borrower   has   executed,   in  favor  of  Motorola,  a
promissory   note   (the   "Note")   in  an   aggregate   principal   amount  of
U.S.$10,000,000, plus accrued interest;

         D.       Guarantor  will  receive direct and indirect benefits from the
financing provided by Motorola to Borrower; and

         E        Motorola's  willingness  to provide the financing contemplated
by the Credit Agreement is conditioned upon and subject to your guarantee of the
Borrower's obligations thereunder and under the Note.


                                    Agreement

         In order to induce Motorola to extend credit to the Borrower, Guarantor
does hereby covenant and agree as follows:

         1. (a) Guarantor hereby  absolutely,  unconditionally  and irrevocably,
jointly with any other guarantors,  and severally,  as a primary obligor and not
merely as a surety, guarantees the full and prompt payment of all obligations of
the  Borrower  under the Note and the  Credit  Agreement,  including  the entire
outstanding  principal balance of the Note, together with accrued interest,  and
with late charges and any other  charges,  attorneys'  fees,  costs and expenses
provided for under the Credit Agreement (the "Guaranteed Obligations").  Without
limiting the generality of the  foregoing,  Guarantor's  obligations  shall also
extend to all  amounts  which  would be owed by the  Borrower  under the  Credit
Agreement and the Note, or which would become payable under such  documents,  in
each case but for the fact that they are unenforceable,  or not allowable due to
the existence of a bankruptcy,  reorganization,  or similar proceeding involving
the Borrower.

                  (b) Guarantor's  obligations hereunder shall not be subject to
any reduction,  limitation,  impairment or termination for any reason, including
but not  limited  to, any claim of waiver,  release,  surrender,  alteration  or
compromise,  and shall not be  subject to any  defense or setoff,  counterclaim,
recoupment or termination whatsoever by reason of any of the following:  (i) the
invalidity or  unenforceability  of the Note or the Credit Agreement or any part
thereof;  (ii) any  extension,  modification  or renewal of, or indulgence  with
respect to, or  substitutions  for, the sum  evidenced by the Note or the Credit
Agreement or any part  thereof or any  agreement  relating  thereto at any time;
(iii) any failure or omission to enforce any right,  power or remedy against the
Borrower or any guarantor with respect to the Credit Agreement,  the Note or any
part  thereof;  (iv) any waiver of any right,  power or remedy or of any default
with respect to the Credit Agreement,  the Note or any part thereof or any other
agreement relating thereto; or (v) any compromise,  settlement,  waiver or other
modification,  or any release or surrender,  whether or not knowingly given with
the consent of Motorola, with or without consideration, of the Credit Agreement,
the Note, any other guarantees with respect to the Credit Agreement, the Note or
any part thereof or any other obligation of any person or entity with respect to
the Credit Agreement, the Note or any part thereof.  Guarantor will not exercise
any  rights  that  it may  have  by  way of  subrogation  under  this  Guarantee
Agreement,  or  otherwise,  until all amounts owed to Motorola  under the Credit
Agreement have been indefeasibly paid in full. Guarantor  acknowledges that time
is of the essence of this Guarantee Agreement.

                  (c)   This Guarantee Agreement shall be a continuing guarantee
and shall  remain valid and in full force and effect as to all  indebtedness  of
the  Borrower now or  hereafter  arising  pursuant to and under the terms of the
Credit Agreement and the Note.

         2.  As  long  as any  of  the  Guaranteed  Obligations  remain  unpaid,
Guarantor  agrees that this Guarantee  Agreement shall be an absolute,  present,
continuing,  unlimited,  unconditional and irrevocable  guaranty of payment (and
not of  collection).  Suit may be brought and  maintained  against  Guarantor by
Motorola to enforce  any  liability,  obligation  or duty  guaranteed  hereunder
without  joinder of any other person or entity  (including,  but not limited to,
the Borrower).  The liability of Guarantor under this Guarantee  Agreement shall
not be deemed to be waived,  released,  discharged,  impaired or affected by any
foreclosure,  indulgence,  or variation of terms of the Credit  Agreement or the
Note or any part  thereof,  whether  or not it might  vary the risk of  guaranty
under  this  Guarantee  Agreement,   including,   without  limitation,  (i)  any
alteration, amendment,  acceleration,  extension, modification, waiver or change
concerning  the amount of time or manner of payment or performance of any of the
Guaranteed Obligations;  (ii) any discharge or release of any of the obligations
securing the payment or performance  thereof,  whether or not in accordance with
the respective provisions thereof; (iii) bankruptcy, insolvency, reorganization,
liquidation or similar proceedings  concerning the Borrower,  Guarantor,  or any
other guarantor of all or any part of the Borrower's debts to Motorola; (iv) the
addition  or omission  or delay in the  enforcement  of any right or remedy with
respect to any of the  Guaranteed  Obligations or with respect to this Guarantee
Agreement;  or (v) the  receipt,  exchange,  surrender or  acquiescence  in, any
default with respect to any of the Guaranteed Obligations.

         3. Guarantor represents and warrants to Motorola as follows:

                  (a) Guarantor is a [relationship] of the Borrower;

                  (b) The  execution,  delivery and  performance by Guarantor of
this  Guarantee  Agreement  will  not  violate  any  agreements   governing  the
Guarantor, any provision of law or any order of any court or governmental agency
binding upon Guarantor or any of its property,  or the terms of any  instrument,
document or agreement  to which  Guarantor is a party,  either  individually  or
jointly,  with  any  other  person,  firm,  entity  or  corporation  or by which
Guarantor or any of the property of Guarantor is bound,  or be in conflict with,
result in a breach of, or constitute  (with giving of notice,  the lapse of time
or both) a default under any such instrument,  document or agreement,  or result
in the creation or  imposition of any lien upon any of the property or assets of
Guarantor;

                  (c) This Guarantee Agreement constitutes the valid and legally
binding  obligation of  Guarantor,  enforceable  in  accordance  with its terms,
except as  enforceability  thereof  may be  limited  by  applicable  bankruptcy,
insolvency, reorganization, moratorium or similar laws affecting the enforcement
of creditors' rights generally and general equitable principles; and

                  (d) Guarantor  has  made  an  independent  determination  with
respect to the Borrower's  capacity to repay the Note and the Borrower's  future
business  prospects;  Guarantor  has not  relied on any  financial  information,
representation, or other communication from Motorola regarding such matters.

                  (e) Guarantor  represents that except as disclosed on Schedule
A  to  this  Guarantee  Agreement,   Guarantor  has  no  outstanding   guarantee
obligation,  or any other direct or indirect contingent obligation in respect of
indebtedness  of the  Borrower or any other Person which is secured by a lien on
or pledge of any assets or rights of Guarantor  (any such  obligation  excluding
those disclosed on Schedule A a "Secured  Guarantee");  Guarantor covenants that
if  at  any  time  while  any  Guaranteed   Obligations  remain  outstanding  or
unsatisfied, Guarantor shall enter into any Secured Guarantee for the benefit of
any  creditor,  Guarantor  shall  cause its  obligations  under  this  Guarantee
Agreement  to be secured on a pari passu basis with its  obligations  under such
Secured Guarantee.

         4. (a)  Guarantor  will pay,  discharge  or  otherwise  satisfy  in the
ordinary course of business (a) all  Indebtedness,  (b) all other obligations to
the extent such  obligations  exceed,  in the aggregate,  $1,000,000 and (c) all
obligations and amounts owing to the operator of the PSTN,  except,  in any such
case, to the extent that (i) the amount or validity of any such  Indebtedness or
other  obligation  is currently  being  contested  in good faith by  appropriate
proceedings,  (ii)  appropriate  reserves  in  conformity  with  GAAP  have been
provided on your books, and (iii) such matter does not involve any risk of loss,
forfeiture, or Lien on your assets.

         (b)  Guarantor  will (a)  continue  to engage in  business  of the same
general type as now conducted by it, (b) preserve and maintain in full force and
effect its corporate  existence and good standing under the laws of its State of
incorporation,  (c)  preserve  and maintain in full force and effect all rights,
privileges  qualifications,   permits,  licenses  and  franchises  necessary  or
desirable in the normal conduct of its business, (d) use its reasonable efforts,
in the ordinary course and consistent  with past practice,  to its your business
organization and preserve the goodwill and business of the customers,  suppliers
and others having business  relations with it , and (e) preserve or renew all of
its registered  trademarks,  trade names and service marks, the non-preservation
of which  could  have a material  adverse  effect on its  business,  operations,
financial condition, or its ability to its your obligations hereunder.

         (c)  Guarantor  will  keep  proper books of record and account in which
full,  true, and correct entries in conformity with GAAP and all Requirements of
Law shall be made to reflect  truly the  financial  position and the results its
operations.  Upon reasonable  notice,  Guarantor will permit  representatives of
Motorola  to visit  and  inspect  any of its  properties  and  examine  and make
extracts from and copies of any of its books and records at any reasonable  time
during  normal  business  hours and as often as may  reasonably  be  desired  by
Motorola,  and to  discuss  Guarantor's  business,  operations,  properties  and
financial and other condition.

         (d)  So  long as the Credit remains outstanding and unpaid or any other
amount  is owing  by  Borrower  to  Motorola,  Guarantor  will  comply  with the
following unless Motorola has consented in writing to your failure to so comply:

                  (i). Guarantor will not enter into any merger or consolidation
or  amalgamation,  will  not  liquidate,  wind up or  dissolve  (or  suffer  any
liquidation or dissolution), and shall not convey, sell, lease, assign, transfer
or  otherwise  dispose of any of its  property,  business or assets  (including,
without  limitation,  receivables and leasehold  interests) whether now owned or
hereafter  acquired  (except  the sale or other  disposition  of assets for good
consideration in the ordinary course of business) if any such transaction  might
materially  adversely the  Guarantor's  business,  financial  condition,  or its
ability to perform its obligations hereunder.

                  (ii) Guarantor  will not amend, supplement or otherwise modify
or waive  compliance  with any  provision  of its articles of  incorporation  or
by-laws  if such  amendment,  supplement,  modification  or waiver  would have a
material  adverse  effect  on its  business,  operation,  assets  (taken  in the
aggregate) or financial  condition,  or would otherwise materially and adversely
affect its ability to perform its obligations hereunder.

                  (iii) Guarantor will  not  transfer or attempt to transfer its
FCC  licenses  to  operate  any paging  system to any  Person  other than in the
ordinary course of business.

                  (iv)  Guarantor  will not engage in the  purchase of goods and
services, directly or indirectly, on any basis other than arms'-length.

                  (v)  Guarantor   will  not  form,   create,   or  acquire  any
subsidiaries except those identified on Schedule 2 hereto.

         5.       This  Guarantee  Agreement  is,  and  shall be deemed to be, a
contract  entered into,  under and pursuant to the substantive laws of the State
of Illinois, without regard to the conflict of laws rules thereof.

         6.       Guarantor  agrees  that if Motorola shall employ legal counsel
in order to  successfully  present,  enforce or defend any or all of  Motorola's
rights or remedies  hereunder,  then in any such event,  Guarantor shall pay all
reasonable  attorneys'  fees and  reasonable  costs  and  expenses  incurred  by
Motorola in connection therewith.

         7.        All  notices,  requests,  demands  and  other  communications
hereunder  shall be in  writing  and shall be deemed to have been given (a) when
hand  delivered  (or if  delivery  is  refused,  at the time of  refusal) to the
address  set forth  below,  (b) when  received  or refused as  evidenced  by the
delivery  receipt if sent by Certified  Mail,  Return  Receipt  Requested,  with
proper  postage  prepaid,  addressed  as set forth below,  (c) when  received or
refused as evidenced by the delivery receipt if sent by reputable  international
courier,  with delivery  charges  prepaid,  addressed as set forth below, or (d)
when received as evidenced by the transmission report of the telecopy machine of
the transmitting party  acknowledging a good transmission if sent by telecopy to
the number set forth below:

If to MOTOROLA INC. at:                         With a copy to:
                                                Motorola Paging Products Group
1303 East Algonquin Road                        5401 North Beach Street
Schaumburg, Illinois  60196                     Fort Worth, Texas 76137
                                                Attn: __________
                                                Telephone: (817) ________
                                                Telecopy:  (817) 245-2236


If to the Guarantor, at:                        With a copy to:
- -----------------------------                   -------------------------------

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

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

Telephone: ___________________                  Telephone: ___________________
Telecopy:  ___________________                  Telecopy:  ___________________



         8. No  modification  or  waiver  of any  provision  of  this  Guarantee
Agreement shall be effective  unless the same shall be in a writing signed by an
officer of  Motorola  and each  other  party  whose  rights or  obligations  are
affected thereby.  No failure or any delay on the part of Motorola in exercising
any right, power or privilege  hereunder shall operate as a waiver thereof;  nor
shall a single or partial exercise of any right,  power or privilege  constitute
an election of remedy or otherwise preclude any other or future exercise thereof
or the exercise of any other right, power or privilege granted by this Guarantee
Agreement or by law. The rights,  powers and privileges  provided for herein are
cumulative  of each other and of those  provided for by law and none of them are
exclusive of any of the others or those provided for by law.

         9. Subject  to  the  restrictions  on assignment contained herein, this
Guarantee  Agreement  shall be  binding  upon and  inure to the  benefit  of the
parties hereto and their respective  successors and permitted assigns.  Motorola
shall  have  full  right to assign  its  rights  and  delegate  its  obligations
hereunder or any interest  herein in full, or in part,  in  connection  with any
assignment  (including  but not  limited to the sale of  participations)  of its
rights under the Credit  Agreement.  Guarantor shall have no right to assign any
of its rights or delegate any of its  obligations  hereunder to any other person
or entity without the prior written consent of an officer of Motorola.

         10. Motorola shall endeavor to give Guarantor notice of default or non-
performance  by the  Borrower in  connection  with any breach of the Note or the
Credit  Agreement,  but no delay or failure by  Motorola to give any such notice
shall in any way  detract  from,  limit or  release  the  Guarantor  from any of
Guarantor's  obligations  under this Guarantee  Agreement.  The Guarantor hereby
waives  presentment,  protest,  notice of protest and notice of either dishonor,
default or  nonperformance  in connection  with any of  Guarantor's  obligations
under this Guarantee  Agreement to the fullest extent it may lawfully do so, and
any and all  demands  and other  notice of every kind that may be required to be
given by law.

         11. Upon  any  determination  that  any  provision  hereof  is invalid,
illegal or  unenforceable  in any respect,  this  Guarantee  Agreement  shall be
deemed  to be  modified  accordingly  so as to be valid and  enforceable  to the
maximum  extent  allowed by law and the remaining  terms and  provisions of this
Guarantee  Agreement  shall not be affected  thereby and shall  continue in full
force and effect.

         12.  This  Guarantee  Agreement  shall  be  effective  upon the date of
execution hereof and the obligations of the Guarantor shall continue, subject to
the next  sentence,  until the  receipt  by  Motorola  of payment in full of all
amounts due Motorola under the Credit  Agreement.  The  obligations of Guarantor
under this  Guarantee  Agreement  shall  continue  to be  effective  or shall be
reinstated,  as applicable, if at any time any payment received by Motorola with
respect to any of the Guaranteed  Obligations,  or this Guarantee Agreement,  is
rescinded or must be returned to the Borrower upon the insolvency, bankruptcy or
reorganization of the Borrower, and in each such case the rights of Motorola and
Guarantor's  obligations  under  this  Guarantee  Agreement  shall be treated as
though such payments were never made.

         13.Guarantor hereby acknowledges that this Guarantee Agreement is given
in order to enhance the ability of the  Borrower to perform its  obligations  to
Motorola under the Credit Agreement.

         14.Nothing  in  this Guarantee Agreement or any of the other agreements
related to the  financing  of the  Borrower's  paging  system shall be deemed to
constitute  any kind of  partnership,  joint venture or other common  enterprise
between  Guarantor  and Motorola or any kind of fiduciary  relationship  between
Motorola and Guarantor.

         15.Motorola shall have no liability to Guarantor under or in connection
with the financing of the Borrower's paging system for any special,  incidental,
indirect,  consequential or punitive damages of any kind or nature, even if such
damages may be reasonably foreseeable.

         16.Guarantor  hereby subordinates, to all rights of Motorola as against
the Borrower, all rights to payment, claims, and other interests of Guarantor in
or against Borrower.

         17. ANY SUIT,  ACTION OR  PROCEEDING  AGAINST ANY PARTY WITH RESPECT TO
THIS AGREEMENT,  OR ANY OTHER OBLIGATION OR ANY JUDGMENT ENTERED BY ANY COURT IN
RESPECT OF ANY THEREOF MAY BE BROUGHT IN THE  APPROPRIATE  COURT OF THE STATE OF
ILLINOIS,  U.S.A.,  OR IN THE  APPROPRIATE  U.S.  DISTRICT COURT IN THE STATE OF
ILLINOIS, U.S.A., AND EACH PARTY HERETO HEREBY IRREVOCABLY SUBMITS GENERALLY AND
UNCONDITIONALLY  TO THE  NONEXCLUSIVE  JURISDICTION  OF EACH SUCH  COURT FOR THE
PURPOSE OF ANY SUCH SUIT,  ACTION OR  PROCEEDING.  EACH PARTY HERETO AGREES THAT
SERVICE  OF ALL  WRITS,  PROCESS  AND  SUMMONSES  IN ANY SUCH  SUIT,  ACTION  OR
PROCEEDING BROUGHT IN THE STATE OF ILLINOIS, U.S.A., MAY BE MADE UPON EACH PARTY
AT ITS RESPECTIVE ADDRESS ABOVE. EACH PARTY HERETO HEREBY  IRREVOCABLY  CONSENTS
TO THE  SERVICE OF PROCESS IN ANY  ACTION OR  PROCEEDING  IN SAID  COURTS BY THE
MAILING THEREOF BY REGISTERED OR CERTIFIED MAIL, POSTAGE PREPAID,  TO IT AT SUCH
ADDRESS.  EACH PARTY HERETO HEREBY IRREVOCABLY WAIVES ANY OBJECTION WHICH IT MAY
NOW OR  HEREAFTER  HAVE TO THE  LAYING  OF  VENUE OF ANY SUCH  SUIT,  ACTION  OR
PROCEEDING  BROUGHT IN ANY SUCH COURT AND HEREBY FURTHER  IRREVOCABLY WAIVES ANY
CLAIM THAT ANY SUCH  SUIT,  ACTION OR  PROCEEDING  BROUGHT IN ANY SUCH COURT HAS
BEEN BROUGHT IN AN INCONVENIENT FORUM.

         18. GUARANTOR  AND  MOTOROLA  EACH  HEREBY  KNOWINGLY,  VOLUNTARILY AND
INTENTIONALLY  WAIVE THE RIGHT EITHER MIGHT HAVE TO A JURY TRIAL WITH RESPECT TO
ANY  LITIGATION OR ACTION BASED  HEREON,  ARISING OUT OF, UNDER OR IN CONNECTION
WITH THIS GUARANTEE  AGREEMENT OR THE NOTE, OR ANY COURSE OF CONDUCT,  COURSE OF
DEALING, STATEMENTS (WHETHER VERBAL OR WRITTEN), OR ACTIONS OF ANY PARTY TO THIS
GUARANTEE AGREEMENT OR THE NOTE.



                                     [GUARANTOR]


                                     By:____________________________________
                                     Its:___________________________________








                             SCHEDULE 1 TO GUARANTEE
                                       OF
                                   [GUARANTOR]

                     Secured Guarantees as of June 17, 1998









                             SCHEDULE 2 TO GUARANTEE
                                       OF
                                   [GUARANTOR]

                                  Subsidiaries














                                    EXHIBIT D

                      LIST OF SUBSIDIARIES OF THE BORROWER

                                      None.









                                    EXHIBIT E

                           FORM OF FINANCING STATEMENT











                                    EXHIBIT F

                      LIST OF ASSUMED NAMES OF THE BORROWER

                                      None