EXHIBIT 10.4C

                            ASSET PURCHASE AGREEMENT

                                 By and Between

                          AMERICAN TOWER SYSTEMS, INC.

                                       and

               DIABLO COMMUNICATIONS OF SOUTHERN CALIFORNIA, INC.

                                   Dated as of

                                  July 8, 1997











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<TABLE>
<CAPTION>
                                TABLE OF CONTENTS

<S>               <C>                                                                                            <C>
ARTICLE 1         DEFINED TERMS...................................................................................1

ARTICLE 2         SALE AND PURCHASE OF ASSETS.....................................................................2
                  2.1      Agreement to Sell and Buy..............................................................2
                  2.2      Assumption of Liabilities and Obligations. ............................................2
                  2.3      Closing; Purchase Price................................................................5
                  2.4      Accounts Receivable....................................................................6
                  2.5      Like-Kind Exchanges....................................................................7

ARTICLE 3         REPRESENTATIONS AND WARRANTIES OF DIABLO........................................................7
                  3.1      Organization and Business; Power and Authority; Effect of Transaction..................7
                  3.2      Financial and Other Information.  .....................................................8
                  3.3      Changes in Condition...................................................................9
                  3.4      Materiality............................................................................9
                  3.5      Title to Properties; Leases............................................................9
                  3.6      Compliance with Private Authorizations................................................10
                  3.7      Compliance with Governmental Authorizations and Applicable Law........................11
                  3.8      Intangible Assets.....................................................................12
                  3.9      Related Transactions..................................................................12
                  3.10     Insurance.............................................................................12
                  3.11     Tax Matters.  ........................................................................12
                  3.12     Employee Retirement Income Security Act of 1974.......................................13
                  3.13     Absence of Sensitive Payments.........................................................15
                  3.14     Inapplicability of Specified Statutes.................................................15
                  3.15     Employment Arrangements...............................................................15
                  3.16     Material Agreements...................................................................15
                  3.17     Ordinary Course of Business...........................................................16
                  3.18     Material and Adverse Restrictions.....................................................16
                  3.19     Broker or Finder......................................................................17
                  3.20     Solvency..............................................................................17
                  3.21     Environmental Matters.................................................................17

ARTICLE 4         REPRESENTATIONS AND WARRANTIES OF ATS..........................................................17
                  4.1      Organization and Business; Power and Authority; Effect of Transaction.................17
                  4.2      Broker or Finder......................................................................18
                  4.3      Solvency..............................................................................18
                  4.4      No Legal Action.......................................................................18

ARTICLE 5         COVENANTS......................................................................................18
                  5.1      Access to Information; Confidentiality................................................18
                  5.2      Agreement to Cooperate.  .............................................................19
                  5.3      Public Announcements..................................................................20
                  5.4      Notification of Certain Matters.......................................................20
                  5.5      No Solicitation.......................................................................21
                  5.6      Conduct of Business by Diablo Pending the Closing.....................................21
                  5.7      Preliminary Title Reports.............................................................22
                  5.8      Environmental Site Assessments........................................................23
                  5.9      Post-Closing Covenants and Agreements of the Parties..................................23


                                       

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ARTICLE 6         CLOSING CONDITIONS.............................................................................24
                  6.1      Conditions to Obligations of Each Party to effect the Transactions....................24
                  6.2      Conditions to Obligations of ATS......................................................24
                  6.3      Conditions to Obligations of Diablo...................................................27

ARTICLE 7         TERMINATION, AMENDMENT AND WAIVER..............................................................28
                  7.1      Termination...........................................................................28
                  7.2      Effect of Termination.................................................................28

ARTICLE 8         INDEMNIFICATION................................................................................29
                  8.1      Survival..............................................................................29
                  8.2      Indemnification.......................................................................29
                  8.3      Limitation of Liability...............................................................30
                  8.4      Notice of Claims......................................................................31
                  8.5      Defense of Third Party Claims.........................................................32
                  8.6      Exclusive Remedy......................................................................32

ARTICLE 9         GENERAL PROVISIONS.............................................................................32
                  9.1      Amendment.............................................................................32
                  9.2      Waiver................................................................................32
                  9.3      Fees, Expenses and Other Payments.....................................................33
                  9.4      Notices...............................................................................33
                  9.5      Specific Performance; Other Rights and Remedies.......................................34
                  9.6      Severability..........................................................................34
                  9.7      Counterparts..........................................................................35
                  9.8      Section Headings......................................................................35
                  9.9      Governing Law; Venue..................................................................35
                  9.10     Further Acts..........................................................................35
                  9.11     Entire Agreement......................................................................35
                  9.12     Assignment............................................................................35
                  9.13     Parties in Interest...................................................................35
                  9.14     Mutual Drafting.......................................................................35
                  9.15     Arbitration...........................................................................36
                  9.16     Disclosure Schedule...................................................................36
</TABLE>

APPENDIX A:                Definitions

SCHEDULES:

         Diablo Disclosure Schedule

EXHIBITS:

         EXHIBIT A         Form of Noncompetition Agreement (Section 6.2(j))
         EXHIBIT B         Form of Indemnity Escrow Agreement (Section 6.2(k))



                                      -ii-

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                            ASSET PURCHASE AGREEMENT

         This Asset Purchase Agreement (this "Agreement") is dated as of July 8,
1997 by and  between  American  Tower  Systems,  Inc.,  a  Delaware  corporation
("ATS"), and Diablo  Communications of Southern  California,  Inc., a California
corporation ("Diablo").

         WHEREAS,  Diablo owns and leases and operates  communication towers and
is engaged in the  business of managing  communication  sites for third  parties
(the "Diablo Business");

         WHEREAS,  ATS desires to purchase and Diablo  desire to sell the Diablo
Assets and the  Diablo  Business  on the terms and  conditions  hereinafter  set
forth;

         WHEREAS,  simultaneously  with  the  execution  and  delivery  of  this
Agreement,  ATS and Diablo have  entered into an escrow  agreement  (the "Escrow
Agreement") with Bank of San Francisco (the "Escrow  Agent"),  pursuant to which
ATS has made a deposit of $200,000 (the "Escrow Deposit");

         WHEREAS,  ATS is party  to an  asset  purchase  agreement  with  Diablo
Communications,  Inc., a California corporation ("DCI"), dated as of the date of
this Agreement (the "Other Agreement"), relating to the purchase and sale of the
communication towers and the business of managing  communication sites for third
parties of DCI; and

         WHEREAS,  ATS and Diablo have heretofore  executed and delivered a Note
Purchase Agreement, dated as of March 20, 1997 (the "Note Agreement"),  pursuant
to which Diablo has issued an unsecured note in the aggregate  principal  amount
of up to Seven Hundred Fifty Thousand Dollars ($750,000) (the "Interim Financing
Note");

         NOW,  THEREFORE,  in  consideration  of  the  above  premises  and  the
covenants and agreements contained herein, the parties,  intending to be legally
bound, do hereby covenant and agree as follows:


                                    ARTICLE 1

                                  DEFINED TERMS

         As used  herein,  unless  the  context  otherwise  requires,  the terms
defined in  Appendix A shall have the  respective  meanings  set forth  therein.
Terms defined in the singular  shall have a comparable  meaning when used in the
plural,  and vice  versa,  and the  reference  to any gender  shall be deemed to
include all genders.  Unless otherwise  defined or the context otherwise clearly
requires,  terms for which  meanings are provided in this  Agreement  shall have
such meanings when used in the Diablo  Disclosure  Schedule and each  Collateral
Document  executed  or required  to be  executed  pursuant  hereto or thereto or
otherwise  delivered,  from time to time,  pursuant hereto or thereto.  The term
"either party" shall, unless the context otherwise requires, refer to Diablo and
ATS.



                                                      


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                                    ARTICLE 2

                           SALE AND PURCHASE OF ASSETS

         2.1 Agreement to Sell and Buy.  Subject to the terms and conditions set
forth in this  Agreement,  Diablo  hereby agrees to sell,  assign,  transfer and
deliver to ATS at the Closing,  and ATS agrees to purchase at the  Closing,  the
Diablo Assets and the Diablo Business, free and clear of any Liens of any nature
whatsoever except for Permitted Liens. For purposes of this Agreement,  the term
"Diablo Assets" shall mean all of the Assets of Diablo,  other than the Excluded
Assets.  For purposes of this Agreement,  the term "Excluded  Assets" shall mean
the following Assets:

                  (a) all cash;

                  (b) all cash equivalents;

                  (c) all Accounts Receivable;

                  (d) all books and records  (including without  limitation,  if
         retained by Diablo,  any  financial  records  necessary or desirable to
         enable the condition specified in Section 6.2(g) to be satisfied) which
         Diablo is required by Applicable Law to retain, subject to the right of
         ATS to have access and to copy for a period of three (3) years from the
         Closing  Date;  the records  described  herein  shall  further  include
         without limitation all corporate seals,  certificates of incorporation,
         minute books,  stock books,  Tax Returns or other records  having to do
         with the corporate organization of Diablo;

                  (e) any pension,  profit-sharing  or employee  benefit  plans,
         including any assets in any related trusts;

                  (f) the miscellaneous assets of Diablo and the personal assets
         of the officers,  directors,  shareholders and employees of Diablo, all
         as  more  specifically  described  in  Section  2.1(f)  of  the  Diablo
         Disclosure Schedule;

                  (g) any of the real property specifically described in Section
         2.1(g)  of the  Diablo  Disclosure  Schedule  which is  covered  by any
         agreement  executed and delivered pursuant to the provisions of Section
         6.2(p); and

                  (h)  any  and all  products,  profits  and  proceeds  of,  and
         including  without  limitation  any Claims with  respect to, any of the
         foregoing.

         2.2      Assumption of Liabilities and Obligations.

         (a) At the Closing,  ATS shall assume and agree to pay,  discharge  and
perform the following obligations and liabilities of Diablo  (collectively,  the
"Diablo  Assumed  Obligations"):  (i) all of the  obligations and liabilities of
Diablo  under the Diablo  Assumable  Agreements,  and (ii) all  obligations  and
liabilities  of Diablo with respect to the ownership and operation of the Diablo
Assets and the conduct of the Diablo  Business,  on and after the Closing  Date;
provided,  however, that notwithstanding the foregoing, ATS shall not assume and
agree to pay, and shall not, except as provided in Section 2.2(c),  be obligated
with respect to, the Diablo Nonassumed Obligations.

         (b) Except as otherwise  specifically set forth in this Agreement or in
the Diablo Disclosure  Schedule to the contrary,  ATS shall not assume or become
obligated to perform any debt, liability or

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obligation of Diablo relating to any of the following matters (collectively, the
"Diablo Nonassumed Obligations"):

                  (i) the  ownership or  operation  of the Diablo  Assets or the
         conduct of the Diablo  Business  prior to the Closing  Date,  including
         without  limitation  Taxes,  unfunded  pension  costs,  any  Employment
         Arrangement of Diablo (including  without  limitation any obligation to
         any Diablo  Employee for  severance  benefits or, except as provided in
         Section 2.2(c),  vacation time or sick leave), and any of the following
         to the extent same arise from Events  occurring prior to or existing on
         the Closing Date:  products  liability,  Legal Actions or other Claims,
         and obligations and liabilities relating to Environmental Law;

                  (ii) any obligations or liabilities under the Diablo Assumable
         Agreements relating to the period prior to the Closing;

                  (iii)  any insurance policies of Diablo;

                  (iv) those  required to be disclosed in the Diablo  Disclosure
         Schedule  which are not so disclosed or which,  if  disclosed,  Section
         2.2(b)(iv)  of the  Diablo  Disclosure  Schedule  indicates  that  such
         obligation or liability will not be assumed;

                  (v) any liability or obligation  from or relating to breach of
         any warranty or any misrepresentation by Diablo under this Agreement or
         any Collateral Document;

                  (vi) any liability or obligation from or relating to breach or
         violation  of, or  failure to  perform,  any of  Diablo's  obligations,
         covenants,  agreements or  undertakings  set forth in this Agreement or
         any Collateral Document, including without limitation Article 5 of this
         Agreement;

                  (vii) any  obligation  or  liability  relating to any Excluded
         Asset;

                  (viii) any obligation or liability with respect to capitalized
         lease obligations or Indebtedness for Money Borrowed;

                  (ix) any Taxes, fees, expenses or other amounts required to be
         paid by Diablo  pursuant to the  provisions  of this  Agreement  or any
         Collateral Document; and

                  (x) any  Contract  with any  Affiliate  of Diablo,  other than
         those set forth in Section 2(b)(x) of the Diablo Disclosure Schedule.

All  Diablo  Nonassumed  Obligations  shall  remain and be the  obligations  and
liabilities solely of Diablo.

         (c)  Anything in this  Section or  elsewhere  in this  Agreement to the
contrary  notwithstanding,  the term "Diablo  Nonassumed  Obligations" shall not
include,  and the term "Diablo Assumed  Obligations" shall include,  (i) the ATS
Assumed Vacation  Liability and the ATS Accrued Sick Time Liability and (ii) any
liability  arising out of the  transfer or  assignment  to ATS of, or the use or
enjoyment of the benefits by ATS under, any Contract, Governmental Authorization
or Private  Authorization  the transfer or  assignment  of which  (according  to
Section  2.2(c) of the Diablo  Disclosure  Schedule or according to the terms of
such Government  Authorization or Private Authorization) requires or may require
the  consent  of  any  Authority  or  other  third  party   (collectively,   the
"Nonassignable  Contracts"),  if ATS  has,  on or  prior  to the  Closing  Date,
notified  Diablo in writing (an  "Acceptance  Notice")  that ATS consents to the
transfer or assignment  of such  Nonassignable  Contract  despite the failure or
inability of ATS and Diablo to obtain the approval or consent

                                       -3-


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of an Authority or other Person whose  approval or consent is required  pursuant
to the terms of such  Nonassignable  Contract,  or receives the benefits of such
Nonassignable Contract, in either of which events, if the approval or consent of
an  Authority  or other  Person  applicable  to transfer  of such  Nonassignable
Contract  is required to be  obtained  as a  condition  to ATS'  obligations  at
Closing  pursuant to the  provisions of Section  6.1(a),  6.2(d) or 6.2(m),  ATS
shall be deemed to have waived such condition with respect to such Nonassignable
Contract.  With respect to any  Nonassignable  Contract for which the applicable
consent  of  any  Authority  or  other  Person  is  not  obtained  prior  to the
Termination Date and for which ATS does not timely deliver an Acceptance  Notice
as  described  in the  preceding  sentence,  Diablo and ATS shall  enter into an
agreement  reasonably  acceptable  to each party  which  agreement  shall to the
maximum extent  feasible  provide ATS with the rights,  benefits and obligations
under such Nonassignable  Contracts.  The term "ATS Assumed Vacation  Liability"
shall mean the liability for Diablo  employees with respect to accrued  vacation
(or  payment  in lieu  thereof),  whether  accrued  before or after the  Closing
subject to the following limitations and/or qualifications: (i) accrued vacation
for all Diablo  Employees  who are  retained by Diablo after the Closing will be
the sole responsibility of Diablo; (ii) accrued vacation for any Diablo Employee
who elects to resign prior to close,  for reasons other than the sale to ATS, or
whom Diablo chooses to terminate with or without cause,  other than by reason of
the sale to ATS,  will be the  sole  responsibility  of  Diablo;  (iii)  accrued
vacation for Diablo  Employees  who  terminate at Closing and who are either not
rehired  by  ATS or who  choose  not to be  employed  by ATS  will  be the  sole
responsibility  of  ATS;  (iv)  accrued  vacation,  to the  time of  close,  for
employees who are  terminated  by Diablo but rehired by ATS who terminate  their
employment  with ATS but who ATS  wishes to remain as an  employee,  will be the
responsibility of Diablo;  any accrued vacation after Closing for such employees
will be the  responsibility  of ATS;  and (v) accrued  vacation for any employee
terminated by Diablo, rehired by ATS and subsequently terminated by ATS, as well
as accrued  vacation for any employee who is terminated by Diablo prior to close
at the request of ATS,  will be the sole  responsibility  of ATS.  The term "ATS
Accrued Sick Time  Liability"  shall mean the liability  with respect to accrued
sick time (as provided in the applicable  Diablo  Benefit  Arrangement or Plan),
accrued on or before the Closing of Diablo Employees who become employees of ATS
after the  Closing.  Although  ATS has not had an  opportunity  to complete  its
evaluation of the Diablo  employees,  except for the employees being retained by
Diablo,  it is the current intention of ATS to hire initially all of the current
Diablo  employees at positions and  compensation  generally  comparable to those
currently in effect,  subject,  however, to the right of ATS, upon completion of
its  evaluation  and  to  its   determination  of  the  overall  needs  of  ATS,
particularly in light of its general  staffing  patterns and of other pending or
prospective  acquisitions  of comparable  businesses in the state of California,
not to offer such employment to certain of the Diablo  employees or to alter the
terms of such employment,  including the positions and compensation. In no event
shall the  expression  of ATS'  current  intention be deemed to be a covenant or
agreement  of ATS to so employ any  particular  current  Diablo  employee and no
rights to employment by any particular  current Diablo employee shall be created
hereby.

         (d)  Notwithstanding  anything  contained  in  this  Agreement  to  the
contrary,  except  as set  forth in  Section  2.2(d)  of the  Diablo  Disclosure
Schedule,  all items of income and expense  (including  without  limitation with
respect to rent,  utility  charges,  Pro Ratable  Taxes and wages and  salaries)
arising from the  ownership or operation of the Diablo  Assets or the conduct of
the Diablo  Business  shall be prorated as of 12:01 a.m.,  Pacific  time, on the
Closing Date,  with Diablo  entitled to and responsible for any such items on or
prior to the Closing Date and ATS entitled to and responsible for any such items
relating  to any  subsequent  period.  For these  purposes,  Pro  Ratable  Taxes
attributable  to a period  that begins  before and ends after the  Closing  Date
shall be treated on a "closing of the books" basis as two partial  periods,  one
ending at the close of the Closing Date and the other beginning on the day after
the Closing Date, except that Pro Ratable Taxes (such as property Taxes) imposed
on a periodic  basis shall be allocated on a daily basis.  If either party shall
have  received  any such  revenues or paid any such  expenses or charges  which,
pursuant to the terms hereof, the other party is entitled to or responsible for,
it shall furnish the other party with a detailed  statement of any such items as
soon as  practicable  after  receipt or payment  thereof.  The parties shall use
their best efforts to

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agree upon such items and other  adjustments  prior to the Closing  Date and, in
any  event,  except as set forth in  Section  2.2(c)  of the  Diablo  Disclosure
Schedule,  within sixty (60) days  thereafter.  If the parties are unable within
such  period to agree  upon such  items and other  adjustments,  Diablo  and ATS
shall,  within the following ten (10) days, jointly designate a nationally known
independent public accounting firm to be retained to review such items and other
adjustments.  The fees and other expenses of retaining such  independent  public
accounting firm shall be borne equally by Diablo and ATS. Such firm shall report
its conclusions as to such items and other adjustments  pursuant to this Section
and such report shall be  conclusive  on all parties to this  Agreement  and not
subject to  dispute or review.  Upon such  agreement  or  determination  by such
independent  accounting firm,  Diablo or ATS, as the case may be, shall promptly
reimburse the other party for any income  received or expenses paid by the other
party and not  previously  reimbursed or any other  adjustment  required by this
Section.  Notwithstanding the foregoing or any other provision of this Agreement
to the contrary,  ATS shall be solely  responsible for the payment of, and shall
defend,  indemnify  and  hold  harmless  Diablo,  its  officers,  directors  and
shareholders  from,  any and all  supplemental  or  additional  real property or
personal  property taxes assessed on or in connection  with the Diablo Assets or
any part  thereof,  which  arise  from  the  transactions  contemplated  by this
Agreement,  with  respect to  California  or other sales  and/or use taxes,  and
documentary  or  governmental  transfer or stamp taxes arising from the purchase
and sale of the Diablo Assets and the Diablo Business contemplated hereby.

         Nothing contained in this Section 2.2(d) is intended or shall be deemed
to amend or modify the indemnification provisions of Article 8 nor to reallocate
responsibility for the matters set forth therein.

         2.3  Closing;  Purchase  Price.  The closing of the  Transactions  (the
"Closing")  shall take place at Cooper,  White & Cooper,  1333 North  California
Boulevard,  Suite 450, Walnut Creek, CA 94596, at 10:00 a.m.,  local time, on or
before  September 30, 1997, (the "Closing  Date").  At the Closing,  each of the
parties  shall  deliver  such  bills  of  sale,   assignments,   assumptions  of
liabilities,  opinions and other  instruments  and documents as are described in
this  Agreement or as may be otherwise  reasonably  requested by the parties and
their  respective  counsel.  The  purchase  price for the Diablo  Assets and the
Diablo  Business (the "Purchase  Price") shall be an amount equal to $4,500,000,
plus an amount equal to the sum of the Interim  Adjustment and Prepaid  Expenses
and deposits  and minus an amount equal to the sum of (i) the Diablo  Nonassumed
Obligations,  if any,  which ATS  agrees to assume at the  request of Diablo and
(ii) Prepaid Revenues.  The term "Interim Adjustment" shall mean an amount equal
to the aggregate  amount actually  incurred by Diablo from and after November 1,
1996  and  prior  to  the  Closing  Date  with  respect  to  the  completion  of
construction projects and site development  projections (a) described in Section
2.3 of the Diablo  Disclosure  Schedule or (b)  acquired  after the date of this
Agreement in accordance with the provisions of this Agreement, including without
limitation  Section 5.6, and capital  improvements  to, but not personnel costs,
maintenance or other expenses items of,  existing  communication  sites,  in all
cases,  which ATS shall have  approved in writing  prior to their  incurrence or
commitment  by Diablo.  Section  2.3(a) of the Diablo  Disclosure  Schedule sets
forth a description of the items  constituting a part of the Interim  Adjustment
for the period  ended as of a date not more than five (5) days prior to the date
of this  Agreement.  The  Purchase  Price shall be payable by (a)  delivery  and
cancellation  of the  Interim  Financing  Note and the  Additional  Compensation
Certificates (as defined in the Note Agreement)  (valued for such purposes at an
amount equal to the unpaid principal amount of the Interim Financing Notes, plus
accrued and unpaid interest to the Closing Date), (b) ATS instructing the Escrow
Agent to deliver the Escrow Deposit (together with interest and other increments
thereto) to Diablo, (c) crediting against the Purchase Price amounts paid by ATS
pursuant to the  amendment  included as part of the Letter of Intent,  and,  the
balance,  (d) wire transfer of immediately  available funds (i) to the Indemnity
Escrow  Agent  (or as it  may  designate)  pursuant  to  the  provisions  of the
Indemnity Escrow Agreement in the amount of $100,000 (together with interest and
earnings  thereon,  the  "Indemnity  Escrow Fund") and (ii) to Diablo or, to the
extent provided in Section 2.5, the "qualified intermediary" designated pursuant
to the  provisions of Section 2.5, for the balance of the Purchase Price to such
account (or accounts)

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as Diablo shall  designate in written  instructions  to ATS  delivered not later
than two (2) business days prior to the Closing.

         Although the parties  believe  that the value of the tangible  personal
property   (other   than   goodwill,   Governmental   Authorizations,    Private
Authorizations  and  Contracts)   constituting  a  part  of  the  Diablo  Assets
approximate  their depreciated book value, ATS shall have the right, at its sole
discretion,  to engage BIA  Consulting,  Inc. to promptly after the execution of
this Agreement  conduct and use its reasonable best efforts to complete,  within
forty-five (45) days, an appraisal of the Diablo Assets which shall be the basis
for an allocation schedule (the "Tax Allocation Schedule") pursuant to which the
Purchase Price shall be allocated among the Diablo Assets.  Such appraisal shall
be conducted in a manner which does not interfere with or  inconvenience  in any
material  matter any of the  landlords  or tenants at any of Diablo's  sites and
shall not, in any event,  affect the Purchase Price. The cost of such appraisal,
if  undertaken,  shall be borne by ATS.  Each of Diablo and ATS shall report the
purchase  and sale of the Diablo  Assets and the Diablo  Business  and the other
Transactions in accordance with the Tax Allocation  Schedule for purposes of all
federal,  state and local Tax Returns and shall not take,  and shall cause their
respective Affiliates, representatives,  successors and assigns not to take, any
position on any federal, state or local Tax Return or report,  inconsistent with
such  reporting  position.  Each of Diablo and ATS shall promptly give the other
notice of any  disallowance  of or  challenge  to such  reporting  by any Taxing
Authority.  Notwithstanding the provisions of this Section,  the parties to this
Agreement  will  rely  solely  on their  own  advisors  in  determining  the tax
consequences of the  transactions  contemplated by this Agreement and each party
is not relying,  and will not rely, on any  representations or assurances of any
other  party  regarding  such  consequences  other  than  the   representations,
warranties,  covenants and  agreements set forth in writing in this Agreement or
furnished pursuant to the provisions hereof.

         2.4 Accounts Receivable.  At the closing,  Diablo shall appoint ATS its
agent for the purpose of  collecting  all  Accounts  Receivable  relating to the
Diablo Business.  Diablo shall deliver to ATS on or as soon as practicable after
the Closing Date a complete and detailed  statement showing the name, amount and
age of each Accounts  Receivable of the Diablo Business.  Subject to and limited
by the following,  revenues relating to the Accounts  Receivable relating to the
Diablo Business will be for the account of Diablo.  ATS shall use its reasonable
business  efforts to collect the Accounts  Receivable with respect to the Diablo
Business  for a period of one hundred  eighty  (180) days after the Closing Date
(the  "Collection  Period").  Any payment  received by ATS during the Collection
Period from any customer  with an account which is an Accounts  Receivable  with
respect to the Diablo  Business  shall  first be  applied  in  reduction  of the
Accounts  Receivable,  unless the  customer  contests in writing the validity of
such application.  During the Collection Period, ATS shall furnish Diablo with a
list of, and pay over to  Diablo,  the  amounts  collected  with  respect to the
Accounts  Receivable  with respect to the Diablo Business on a monthly basis and
forward to Diablo, promptly upon receipt or delivery, as the case may be, copies
of all correspondence relating to Accounts Receivable.  ATS shall provide Diablo
with a final  accounting on or before the fifteenth (15th) day following the end
of the  Collection  Period.  Upon the request of either  party at and after such
time,  the  parties  shall  meet to  mutually  and in  good  faith  analyze  any
uncollected  Accounts  Receivable to determine if the same, in their  reasonable
business  judgment,  are deemed to be  collectable  and if ATS desires to retain
such Accounts Receivable. As to each such Accounts Receivable, the parties shall
negotiate a good faith value of such Accounts Receivable, which ATS shall pay to
Diablo  if  ATS,  in its  sole  discretion,  chooses  to  retain  such  Accounts
Receivable.  Diablo  shall  retain  the  right to  collect  any of its  Accounts
Receivable  as to which the parties are unable to reach  agreement  as to a good
faith value, and ATS agrees to turn over to Diablo any payments received against
any  such  Accounts   Receivable.   ATS  shall  not  be  obligated  to  use  any
extraordinary  efforts to collect any of the Accounts  Receivable assigned to it
for  collection  hereunder  or to refer  any of such  Accounts  Receivable  to a
collection agency or to any attorney for collection,  and ATS shall not make any
such  referral  or  compromise,  nor  settle  or adjust  the  amount of any such
Accounts Receivable, except with the approval of Diablo. ATS shall not incur any
liability to Diablo for any uncollected account unless ATS shall have

                                       -6-


<PAGE>



engaged in willful  misconduct  or gross  negligence in the  performance  of its
obligations set forth in this Section.  During and after the Collection  Period,
without  specific  agreement  with ATS to the contrary,  neither  Diablo nor its
agents  shall  make any  direct  solicitation  of the  Accounts  Receivable  for
collection purposes, except for Accounts Receivable retained by Diablo after the
Collection  Period.  The  provisions  of this  Section  shall not apply to those
certain  Accounts  Receivable set forth in Section 2.4 of the Diablo  Disclosure
Schedule or to any other Accounts  Receivable which Diablo, in its sole business
judgment,  determines will require extraordinary collection efforts or referrals
to a collection agency or attorney for collection  (collectively,  the "Retained
Accounts  Receivable"),  provided the Retained Accounts Receivable are set forth
in a written notice  delivered to ATS by Diablo on or prior to the Closing Date.
Diablo shall retain the sole and exclusive  right to collect,  whether during or
after the Collection Period, all Retained Accounts Receivable,  as Diablo in its
sole discretion may determine.

         2.5  Like-Kind  Exchanges.  Diablo  shall have the  right,  but not the
obligation, to effect the transfer and conveyance of the Diablo Assets, in whole
or in part,  as part of one or more  exchanges  under  Section 1031 of the Code,
including  the delay in  Closing  of  escrow  for those  Assets  subject  to the
exchange.  If Diablo so elects,  it shall provide  notice to ATS of its election
(the "Like-Kind  Notice"),  setting forth in reasonable  detail which portion or
portions of the Diablo  Assets are to be so treated.  In such event,  Diablo (i)
may at any time at or prior to Closing  assign its rights,  in whole or in part,
under  this  Agreement  with  respect  to such  Diablo  Assets  to a  "qualified
intermediary" as defined in Treas. Reg. ss.1.1031(k)-1(g)(4),  subject to all of
the rights and  obligations  hereunder of ATS, and (ii) shall  promptly  provide
written notice of such  assignment to ATS. No such  assignment  shall,  however,
relieve Diablo of its  obligations  under this  Agreement.  If Diablo shall have
given a Like-Kind  Notice,  ATS shall (i) promptly  provide  Diablo with written
acknowledgment  of such notice,  (ii) at the Closing,  convey the Purchase Price
for the Diablo Assets (or such portion of them as shall have been  designated in
writing by Diablo) to the "qualified  intermediary" rather than to Diablo (which
conveyance  shall,  to such extent,  discharge the  obligation of ATS to deliver
such  Purchase  Price (or portion  thereof),  and (iii) at the request of Diablo
extend the closing of escrow for all or a portion of those assets subject to the
Like-Kind Notice for a period not to exceed one year. Should the closing for any
Like-Kind Notice  properties be so extended,  Diablo and ATS shall enter into an
agreement  reasonably  acceptable to each party which  agreement  shall,  to the
maximum extent feasible,  provide ATS with the rights, benefits, and obligations
for any Like-Kind Notice property for which the closing is so extended.  Without
limiting the  generality of the  foregoing,  Diablo and ATS shall promptly after
receipt  by ATS of the  Like-Kind  Notice,  negotiate  in good faith in order to
determine the portion of the Purchase  Price  attributable  to the Diablo Assets
which are to be the  subject of  like-kind  exchange  and, in the event they are
unable to so agree on such amount,  it shall be  determined  by  arbitration  in
accordance  with the provisions of Section 9.15 and not materially  inconsistent
with the appraisal undertaken pursuant to Section 2.3. If such determination has
not been made on or prior to the Closing,  ATS shall  transfer to the "qualified
intermediary" the amount proposed by Diablo in the Like-Kind Notice,  subject to
an agreement by the "qualified  intermediary" to remit to Diablo the excess,  if
any, of the amount so transferred  over the amount as finally  determined by the
arbitrator.



                                    ARTICLE 3

                    REPRESENTATIONS AND WARRANTIES OF DIABLO

         Diablo hereby  represents,  warrants and covenants to, and agrees with,
ATS as follows:


                                       -7-


<PAGE>



         3.1  Organization  and  Business;   Power  and  Authority;   Effect  of
Transaction.

         (a) Diablo is a corporation  duly  organized,  validly  existing and in
good  standing  under  the laws of its  jurisdiction  of  organization,  has all
requisite  power and authority  (corporate and other) to own or hold under lease
its properties and to conduct its business as now conducted.

         (b) Diablo has all requisite  corporate  power and corporate  authority
and has in full force and effect all  Governmental  Authorizations  (which,  for
purposes of this Section  3.1(b),  relate only to the sale of the Diablo  Assets
and  Diablo  Business   generally  and  not  to   "site-specific"   Governmental
Authorizations   or  those  required  by  local   Applicable  Law)  and  Private
Authorizations,  except  for  those set forth in  Section  3.1(b) of the  Diablo
Disclosure  Schedule or those the failure of which to obtain do not and will not
have,  individually  or in the  aggregate,  any material  adverse effect on ATS,
necessary  to enable it to execute and deliver,  and to perform its  obligations
under,  this Agreement and each Collateral  Document  executed or required to be
executed by it pursuant hereto or thereto or to consummate the Transactions; and
the execution,  delivery and  performance of this Agreement and each  Collateral
Document  executed or  required to be executed by it pursuant  hereto or thereto
have been duly authorized by all requisite corporate or other action on the part
of Diablo.  This  Agreement  has been duly  executed and delivered by Diablo and
constitutes, and each Collateral Document executed or required to be executed by
it pursuant  hereto or thereto or to consummate the  Transactions  when executed
and delivered by Diablo will constitute, legal, valid and binding obligations of
Diablo,  enforceable in accordance with their respective  terms,  except as such
enforceability may be limited by bankruptcy,  moratorium, insolvency and similar
laws  affecting the rights and remedies of creditors and  obligations of debtors
generally and by general principles of equity.

         (c)  Except as set forth in  Section  3.1(c) of the  Diablo  Disclosure
Schedule,  and except for matters which would have no material adverse effect on
ATS,  neither the  execution  and  delivery by Diablo of this  Agreement  or any
Collateral Document executed or required to be executed by it pursuant hereto or
thereto, nor the consummation by Diablo of the Transactions, nor compliance with
the terms, conditions and provisions hereof or thereof by Diablo:

                  (i) will conflict with, or result in a breach or violation of,
         or constitute a default  under,  any Organic  Document of Diablo or any
         Applicable Law (which, for purposes of this Section 3.1(c)(i),  relates
         only to the sale of the Diablo Assets and the Diablo Business generally
         and not to  local  Applicable  Law)  on the  part  of  Diablo,  or will
         conflict  with,  or result in a breach or violation of, or constitute a
         default  under,  or  permit  the  acceleration  of  any  obligation  or
         liability in, or but for any requirement of giving of notice or passage
         of time or both  would  constitute  such a  conflict  with,  breach  or
         violation of, or default under, or permit any such acceleration in, any
         Contractual  Obligation of Diablo, other than those constituting Diablo
         Nonassumed Obligations; or

                  (ii) will  require  Diablo to make or obtain any  Governmental
         Authorization, Governmental Filing (which, for purposes of this Section
         3.1(c)(ii)),  relate  only to the sale of the Diablo  Assets and Diablo
         Business   generally   and   not   to   "site-specific"    Governmental
         Authorizations  or those required by local  Applicable  Law) or Private
         Authorization  including  without  limitation under the FCA, except for
         filings under the Hart-Scott-Rodino Act.

         (d)  Diablo  does not  have any  Subsidiaries  except  as set  forth in
Section 3.1(d) of the Diablo Disclosure Schedule.

         3.2 Financial and Other Information. Diablo has heretofore furnished to
ATS copies of the financial  statements of the Diablo Business listed in Section
3.2 of the Diablo Disclosure Schedule (the "Diablo Financial  Statements").  The
Diablo Financial Statements, including in each case the notes thereto,

                                       -8-


<PAGE>



have been  prepared  in  accordance  with CAAP  applied  on a  consistent  basis
throughout the periods covered thereby,  except as otherwise noted therein or as
set forth in Section 3.2 of the Diablo Disclosure  Schedule,  are true, accurate
and complete in all material respects,  do not contain any untrue statement of a
material  fact or omit to state a material  fact  required  by CAAP to be stated
therein or  necessary  in order to make the  statements  contained  therein  not
misleading,  and  fairly  present  the  financial  position  and the  results of
operations and cash flow of the Diablo Business, on the bases therein stated, as
of the respective dates thereof,  and for the respective periods covered thereby
subject, in the case of unaudited financial statements, to normal year-end audit
adjustments and accruals.

         3.3 Changes in Condition.  Since the date of the most recent  financial
statements constituting a part of the Diablo Financial Statements, except to the
extent specifically  described in Section 3.3 of the Diablo Disclosure Schedule,
there has been no material adverse change in Diablo.  There is no Event known to
Diablo  which  materially  adversely  affects,  or (so  far as  Diablo  can  now
reasonably foresee) is likely to materially adversely affect,  Diablo, except to
the  extent  specifically  described  in Section  3.3 of the  Diablo  Disclosure
Schedule.

         3.4  Materiality.  Other than those set forth in the Diablo  Disclosure
Schedule,  the representations and warranties set forth in this Article would in
the  aggregate be true and correct even without the  materiality  exceptions  or
qualifications  contained  therein.  Other  than  those set forth in the  Diablo
Disclosure Schedule,  in the aggregate all such exceptions and qualifications to
the  representations and warranties are not and could not reasonably be expected
to be materially adverse to Diablo.

         3.5      Title to Properties; Leases.

         (a) Section 3.5(a) of the Diablo  Disclosure  Schedule contains a true,
accurate and complete description of all real property owned or leased by Diablo
that is part of the Diablo Assets.  Except as set forth in Section 3.5(a) of the
Diablo  Disclosure  Schedule,  Diablo  has  good  indefeasible,  marketable  and
insurable  title to all real  property  (other than  leasehold  and managed real
property)  and good  indefeasible  and  merchantable  title to all other  assets
(other than real property), tangible and intangible,  constituting a part of the
Diablo  Assets,  in each case free and clear of all Liens,  except (i) Permitted
Liens, (ii) Liens set forth on Section 3.5(a) of the Diablo Disclosure  Schedule
and (iii) Approved Title Conditions.  Except for financing statements evidencing
Liens referred to in the preceding sentence (a true,  accurate and complete list
and description of which is set forth in Section 3.5(a) of the Diablo Disclosure
Schedule),  no financing  statements  under the Uniform  Commercial  Code and no
other  filing  which names Diablo as debtor or which covers or purports to cover
any of the  Diablo  Assets  is on file in any state or other  jurisdiction,  and
Diablo has not signed or agreed to sign any such  financing  statement or filing
or any  agreement  authorizing  any secured  party  thereunder  to file any such
financing  statement or filing.  Except as  disclosed  in Section  3.5(a) of the
Diablo Disclosure Schedule, to Diablo's knowledge,  all improvements on the real
property  owned or leased by Diablo are in compliance  with  applicable  zoning,
wetlands and land use laws,  ordinances and  regulations  and  applicable  title
covenants,  conditions,  restrictions and reservations in all respects necessary
to conduct the  operations as presently  conducted,  except for any instances of
non-compliance  which  do not and  will  not in the  aggregate  have a  material
adverse  effect  on the  owner  or  lessee,  as the case  may be,  of such  real
property.  Except  as  disclosed  in  Section  3.5(a) of the  Diablo  Disclosure
Statement, all such improvements,  to Diablo's knowledge, comply in all material
aspects  with all  Applicable  Laws,  Governmental  Authorizations  and  Private
Authorizations.  Except as disclosed in Section 3.5(a) of the Diablo  Disclosure
Statement,  to  Diablo's  knowledge,  all of  the  transmitting  towers,  ground
radials, guy anchors, transmitting buildings and related improvements located on
the real  property  owned or leased by Diablo are located  entirely on such real
property.  Diablo has no knowledge of any pending,  threatened  or  contemplated
action to take by eminent  domain or  otherwise  to condemn any part of any real
property owned or leased by Diablo. Except as set forth in Section 3.5(a) of the
Diablo Disclosure Schedule, such real property (other than land),

                                       -9-


<PAGE>



fixtures, fixed assets and other material items of personal property,  including
equipment,  have, in Diablo's reasonable business judgment, been maintained in a
manner  consistent  with  generally  accepted  standards  of  sound  engineering
practice and currently permit the Diablo Business to be operated in all material
respects in accordance  with the terms and  conditions of all  Applicable  Laws,
Governmental Authorizations and Private Authorizations.

         (b) Section 3.5(b) of the Diablo  Disclosure  Schedule contains a true,
accurate and complete  description  of all Leases under which any real  property
used in the Diablo Business is leased. Except as otherwise set forth in Schedule
3.5(b) of the Diablo Disclosure Schedule, each Lease or other occupancy or other
agreement under which Diablo holds real or personal property constituting a part
of the Diablo Assets has been duly authorized,  executed and delivered by Diablo
or its predecessors in interest, as the case may be, and, to Diablo's knowledge,
each of the other parties thereto,  and is a legal, valid and binding obligation
of Diablo,  and,  to  Diablo's  knowledge,  each of the other  parties  thereto,
enforceable in accordance with its terms,  except as such  enforceability may be
limited by  bankruptcy,  moratorium,  insolvency  and similar laws affecting the
rights and remedies of creditors  and  obligations  of debtors  generally and by
general  principles  of equity.  Diablo has a valid  leasehold  interest  in and
enjoys peaceful and undisturbed possession under all Leases pursuant to which it
holds any such real property or tangible personal  property.  All of such Leases
are valid and  subsisting  and in full force and effect;  neither Diablo nor, to
Diablo's  knowledge,  any other party  thereto,  is in  material  default in the
performance,  observance or fulfillment of any obligation, covenant or condition
contained in any such Lease. None of the fixed assets or equipment  comprising a
part of the Diablo  Assets is subject to contracts of sale,  and none is held by
Diablo as lessee or as  conditional  sales vendee under any Lease or conditional
sales contract and none is subject to any title retention  agreement,  except as
set forth in Section 3.5(b) of the Diablo Disclosure Schedule.

         (c) Section 3.5(c) of the Diablo  Disclosure  Schedule contains a true,
accurate  and complete  description  of all  material  items of Diablo  Personal
Property.  Diablo owns and has good and merchantable  title to all of the Diablo
Personal  Property  relating  to  the  Diablo  Business  (the  "Diablo  Personal
Property"),  in each  case,  free and clear of all Liens,  except (i)  Permitted
Liens and (ii)  Liens  set forth on  Section  3.5(c)  of the  Diablo  Disclosure
Schedule  (which Liens shall be released prior to Closing).  Except as set forth
in Section 3.5(c) of the Diablo Disclosure Schedule,  all of the Diablo Personal
Property is in a state of good repair and  maintenance  and is in good operating
condition,  normal  wear and tear  excepted,  has  been  maintained  in a manner
consistent with generally  accepted  standards of good engineering  practice and
currently  permits the Diablo  Business to be  operated in  accordance  with the
terms and conditions of all  Applicable  Laws.  Except for financing  statements
listed in  Section  3.5(c)  of the  Diablo  Disclosure  Schedule,  no  financing
statements  under the Uniform  Commercial  Code and no other  filing which names
Diablo as debtor or which  covers or purports to cover any of the Diablo  Assets
is on file in any state or other  jurisdiction,  and  Diablo  has not  signed or
agreed  to  sign  any  such  financing  statement  or  filing  or any  agreement
authorizing any secured party thereunder to file any such financing statement or
filing.

         3.6 Compliance with Private  Authorizations.  Section 3.6 of the Diablo
Disclosure   Schedule  sets  forth  a  true,  accurate  and  complete  list  and
description of each Private  Authorization which individually is material to the
Diablo Assets or the Diablo Business. To Diablo's knowledge, and as set forth in
Section 3.6 of the Diablo Disclosure  Schedule,  Diablo has obtained all Private
Authorizations  which are necessary for the ownership or operation of the Diablo
Assets  or the  conduct  of the  Diablo  Business  which,  if not  obtained  and
maintained, could, individually or in the aggregate, materially adversely affect
Diablo.  All of such Private  Authorizations  are valid and in good standing and
are in full force and  effect.  Diablo is not in breach or  violation  of, or in
default in the  performance,  observance  or  fulfillment  of, any such  Private
Authorization,  and no Event exists or has occurred,  which constitutes,  or but
for any  requirement  of  giving  of notice  or  passage  of time or both  would
constitute,  such a  breach,  violation  or  default,  under  any  such  Private
Authorization,  except for such  defaults,  breaches or violations as do not and
will not have in the aggregate

                                      -10-


<PAGE>



any material  adverse  effect on Diablo.  No such Private  Authorization  is the
subject of any pending or, to Diablo's knowledge,  threatened attack, revocation
or termination.

         3.7 Compliance with Governmental Authorizations and Applicable Law.

         (a) To  Diablo's  knowledge,  Section  3.7(a) of the Diablo  Disclosure
Schedule contains a true, complete and accurate description of each Governmental
Authorization  required under  Applicable Laws (i) to own and operate the Diablo
Business,  as currently conducted or proposed to be conducted on or prior to the
Closing  Date,  all of  which  are in full  force  and  effect  or (ii)  that is
necessary to permit Diablo to execute and deliver this  Agreement and to perform
its obligations hereunder. To Diablo's knowledge,  except as otherwise set forth
in Section  3.7(a) of the Diablo  Disclosure  Schedule,  Diablo has obtained all
Governmental  Authorizations  which are necessary for the ownership or operation
of the Diablo Assets or the conduct of the Diablo  Business as now conducted and
which, if not obtained and maintained,  would, individually or in the aggregate,
have  any  material   adverse  effect  on  Diablo.   None  of  the  Governmental
Authorizations  listed in Section  3.7(a) of the Diablo  Disclosure  Schedule is
subject to any  restriction  or  condition  which  would  limit in any  material
respect the  ownership or  operations of the Diablo Assets or the conduct of the
Diablo Business as currently  conducted,  except for restrictions and conditions
generally   applicable  to  Governmental   Authorizations   of  such  type.  The
Governmental  Authorizations  listed in Section 3.7(a) of the Diablo  Disclosure
Schedule  are valid and in good  standing,  are in full force and effect and are
not  impaired  in any  material  respect by any act or omission of Diablo or its
officers, directors,  employees or agents, and the ownership or operation of the
Diablo  Assets or the conduct of the Diablo  Business are in  accordance  in all
material respects with the Governmental  Authorizations.  To Diablo's knowledge,
all material reports,  forms and statements  required to be filed by Diablo with
all  Authorities  with  respect to the Diablo  Business  have been filed and are
true,  complete  and  accurate in all material  respects.  No such  Governmental
Authorization  is  the  subject  of  any  pending  or,  to  Diablo's  knowledge,
threatened  challenge or proceeding to revoke or terminate any such Governmental
Authorization.  Diablo  has no  reason  to  believe  that any such  Governmental
Authorization  would  not be  renewed  in the  name of  Diablo  by the  granting
Authority in the ordinary course.


         (b) Except as otherwise specifically described in Section 3.7(b) of the
Diablo Disclosure  Schedule,  neither Diablo nor any director or officer thereof
(in  connection  with ownership or operation of the Diablo Assets or the conduct
of the  Diablo  Business)  is in or is  charged  by any  Authority  with or,  to
Diablo's  knowledge,  at any time since  January 1, 1993 has been in or has been
charged by any Authority with, or, to Diablo's knowledge, is threatened or under
investigation  by any  Authority  with respect to,  breach or  violation  of, or
default in the  performance,  observance  or  fulfillment  of, any  Governmental
Authorization  or any  Applicable Law relating to the ownership and operation of
the Diablo  Assets or the conduct of the Diablo  Business.  In  particular,  but
without  limiting the  generality of the foregoing,  there are no  applications,
complaints or Legal Actions pending or, to Diablo's knowledge, threatened before
or by any  Authority  (x)  relating to the  ownership or operation of the Diablo
Assets or the  conduct  of the Diablo  Business  which,  individually  or in the
aggregate,  are reasonably  likely to result in the revocation or termination of
any  Governmental  Authorization  or the imposition of any restriction of such a
nature as would  adversely  affect the  ownership  or  operations  of the Diablo
Business;  (y) involving  charges of illegal  discrimination by Diablo under any
federal or state employment Laws, or (z) involving  Environmental Laws or zoning
laws, except as otherwise specifically described in Section 3.7(b) of the Diablo
Disclosure Schedule.

         (c) Except as otherwise specifically described in Section 3.7(c) of the
Diablo Disclosure Schedule, no Event exists or has occurred,  which, to Diablo's
knowledge,  constitutes,  or but for any  requirement  of  giving  of  notice or
passage of time or both would constitute,  such a breach,  violation or default,
under (i) any Governmental  Authorization or any Applicable Law, except for such
breaches, violations or defaults as do not and will not have, individually or in
the aggregate, any material adverse effect

                                      -11-


<PAGE>



on Diablo or (ii) any material requirement of any insurance carrier,  applicable
to the ownership or operations of the Diablo Assets or the conduct of the Diablo
Business.

         (d) With respect to matters, if any, of a nature referred to in Section
3.7(a), 3.7(b) or 3.7(c) of the Diablo Disclosure Schedule,  except as otherwise
specifically  described in Section 3.7(d) of the Diablo Disclosure Schedule, all
such information and matters set forth in Sections 3.7(a),  3.7(b) and 3.7(c) of
the Diablo Disclosure  Schedule,  if adversely  determined against Diablo,  will
not,  individually or in the aggregate,  have a materially  adversely  effect on
Diablo.

         3.8 Intangible  Assets.  Section 3.8 of the Diablo Disclosure  Schedule
sets forth a true,  accurate and complete  description of all Intangible  Assets
(other than Governmental  Authorizations and Private Authorizations) relating to
the  ownership  and  operation of the Diablo Assets or the conduct of the Diablo
Business  held or used by Diablo,  including  without  limitation  the nature of
Diablo's  interest  in each and the  extent  to which  the same  have  been duly
registered in the offices as indicated  therein.  Except as set forth in Section
3.8 of the Diablo  Disclosure  Schedule,  to Diablo's  knowledge,  no Intangible
Assets (except  Governmental  Authorizations,  Private  Authorizations,  and the
Intangible  Assets so set forth) are required for the  ownership or operation of
the Diablo  Assets or the  conduct of the Diablo  Business as  currently  owned,
operated  and  conducted or proposed to be owned,  operated and  conducted on or
prior to the Closing Date.  To Diablo's  knowledge,  Diablo does not  wrongfully
infringe  upon or  unlawfully  use any  Intangible  Assets  owned or  claimed by
another,  and Diablo has not  received  any notice of any claim or  infringement
relating to any such Intangible Asset.

         3.9  Related  Transactions.  Diablo  is not a party or  subject  to any
Contractual  Obligation  relating to the  ownership  or  operation of the Diablo
Assets or the  conduct  of the  Diablo  Business  between  Diablo and any of its
officers, directors, shareholders, employees or, to the knowledge of Diablo, any
Affiliate  of  any  thereof,   including  without   limitation  any  Contractual
Obligation  providing  for the  furnishing  of services to or by,  providing for
rental of property,  real,  personal or mixed,  to or from, or providing for the
lending or borrowing of money to or from or otherwise  requiring  payments to or
from,  any  such  Person,  other  than (i)  Employment  Arrangements  listed  or
described in Section 3.15 of the Diablo  Disclosure  Schedule,  (ii) Contractual
Obligations  between  Diablo and any of its directors,  shareholders,  officers,
employees or  Affiliates  of Diablo or any of the  foregoing,  which  constitute
Excluded Assets or Diablo Nonassumed  Obligations,  or (iii) as specifically set
forth in Section 3.9 of the Diablo Disclosure Schedule.

         3.10 Insurance. Diablo maintains, with respect to the Diablo Assets and
the Diablo  Business,  policies  of fire and  extended  coverage  and  casualty,
liability  and other forms of  insurance  in such amounts and against such risks
and losses as are set forth in Section 3.10 of the Diablo Disclosure Schedule.

         3.11     Tax Matters.

         (a)  Except as set forth in Section  3.11(a)  of the Diablo  Disclosure
Schedule,  Diablo  has in  accordance  with all  Applicable  Laws  filed all Tax
Returns which are required to be filed,  except with respect to failures to file
which in the aggregate  would not have a material  adverse effect on Diablo and,
to Diablo's knowledge,  has paid, or made adequate provision for the payment of,
all Taxes which have or may become due and payable  pursuant to said Tax Returns
and all other governmental  charges and assessments  received to date other than
those Taxes being contested in good faith for which adequate  provision has been
made  on the  most  recent  balance  sheet  forming  part  of  Diablo  Financial
Statements. The Tax Returns of Diablo have, to Diablo's knowledge, been prepared
in all material  respects in accordance  with all Applicable  Laws and generally
accepted principles applicable to taxation consistently applied. All Taxes which
Diablo is required by law to withhold and collect have,  to Diablo's  knowledge,
been duly withheld and  collected,  and have been paid over, in a timely manner,
to the proper Authorities to the extent due and payable. Diablo has not

                                      -12-


<PAGE>



executed any waiver to extend,  or otherwise  taken or failed to take any action
that would have the effect of extending,  the applicable  statute of limitations
in respect of any Tax  liabilities  of Diablo for the fiscal  years prior to and
including  the most recent  fiscal  year.  Adequate  provision  has, to Diablo's
knowledge,  been made on the most recent  balance  sheet  forming part of Diablo
Financial  Statements  for all Taxes  accrued  through the date of such  balance
sheet of any kind, including interest and penalties in respect thereof,  whether
disputed or not, and whether  past,  current or deferred,  accrued or unaccrued,
fixed,  contingent,  absolute or other, and there are, to Diablo's knowledge, no
past  transactions  or  matters  which  could  result in  additional  Taxes of a
material nature to Diablo for which an adequate reserve has not been provided on
such balance sheet. Diablo is not a "consenting  corporation" within the meaning
of  Section  341(f)  of the Code.  Diablo  has at all times  been  taxable  as a
Subchapter  S  corporation  under the Code,  and has never  been a member of any
consolidated  group for Tax  purposes,  except as otherwise set forth in Section
3.11(a) of the Diablo Disclosure Schedule.

         (b) The  information  shown on the federal income Tax Returns of Diablo
for each of the most recent five tax years  (true and  complete  copies of which
have, to the extent  requested by ATS,  been  furnished by Diablo to ATS) is, to
Diablo's  knowledge,  true,  accurate and complete in all material  respects and
fairly and accurately  reflects the information  purported to be shown.  Federal
and state  income Tax  Returns of Diablo  have not been  examined  by the IRS or
applicable  state  Authority,  and Diablo has not been  notified of any proposed
examination,  except  as shown  in  Section  3.11(b)  of the  Diablo  Disclosure
Schedule.

         (c) Diablo is not a party to any tax sharing  agreement or arrangement,
other than those contained in certain of its leases.

         3.12     Employee Retirement Income Security Act of 1974.

         (a) Diablo  (which for purposes of this Section shall include any ERISA
Affiliate) is not making any  contribution to or sponsoring,  and has not at any
time since its organization  made any contribution to or sponsored,  any Plan or
Benefit  Arrangement,  except  as set forth in  Section  3.12(a)  of the  Diablo
Disclosure Schedule.  As to all Plans and Benefit Arrangements listed in Section
3.12(a) of the Diablo Disclosure Schedule:

                  (i) all such Plans and  Benefit  Arrangements  comply and have
         been  administered in form and in operation with all Applicable Laws in
         all material respects,  and Diablo has not received any notice from any
         Authority questioning or challenging such compliance;

                  (ii) all such Plans  maintained  or  previously  maintained by
         Diablo that are or were intended to comply with Sections 401 and 501 of
         the  Code  comply  and  complied  in form  and in  operation  with  all
         applicable  requirements  of such  sections,  and no event has occurred
         which  will or could  give  rise to  disqualification  of any such Plan
         under such sections or to a tax under Section 511 of the Code;

                  (iii)  none of the  assets  of any such Plan are  invested  in
         employer securities or employer real property;

                  (iv)  there  have  been  no  "prohibited   transactions"   (as
         described  in Section  406 of ERISA or  Section  4975 of the Code) with
         respect to any such Plan and Diablo  has not  otherwise  engaged in any
         prohibited transaction;

                  (v) there have been no acts or  omissions by Diablo which have
         given rise to or may give rise to any material fines, penalties,  taxes
         or related  charges under Sections  502(c),  502(i) or 4071 or ERISA or
         Chapter 43 of the Code for which Diablo may be liable;

                                      -13-


<PAGE>




                  (vi)  there are no  Claims  (other  than  routine  claims  for
         benefits  or  actions  seeking  qualified  domestic  relations  orders)
         pending or threatened involving such Plans or the assets of such Plans,
         and, to Diablo's knowledge, no facts exist which could give rise to any
         such Claims (other than routine claims for benefits or actions  seeking
         qualified domestic relations orders);

                  (vii) no such Plan is  subject  to Title IV of  ERISA,  or, if
         subject,  there have been no "report  able  events"  (as  described  in
         Section 4043 of ERISA),  and no steps have been taken to terminate  any
         such Plan;

                  (viii) all group health Plans of Diablo have been  operated in
         compliance  in  all  material  respects  with  the  group  health  plan
         continuation coverage requirements of COBRA;

                  (ix) actuarially  adequate  accruals for all obligations under
         the Plans are  reflected in the most recent  balance sheet forming part
         of the Diablo Financial  Statements and such obligations  include a pro
         rata amount of the  contributions  which would otherwise have been made
         in accordance  with past practices for the Plan years which include the
         Closing Date;

                  (x)  neither  Diablo  nor  any  of its  respective  directors,
         officers,  employees or any other fiduciary has committed any breach of
         fiduciary responsibility imposed by ERISA or any similar Applicable Law
         that would subject Diablo or any of its respective directors,  officers
         or  employees  to  material   liability  under  ERISA  or  any  similar
         Applicable Law;

                  (xi) no such Plan which is subject to Part 3 of  Subtitle B of
         Title I of ERISA or Section 412 of the Code had an accumulated  funding
         deficiency  (as  defined in Section 302 of ERISA and Section 412 of the
         Code),  whether or not  waived,  as of the last day of the most  recent
         fiscal  year of such Plan to which  Part 3 of  Subtitle B of Title I of
         ERISA  or  Section  412 of the  Code  applied,  nor  would  have had an
         accumulated funding deficiency on such date if such year were the first
         year of such Plan to which Part 3 of  Subtitle B of Title I of ERISA or
         Section 412 of the Code applied;

                  (xii)  no  material  liability  to the  PBGC  has  been  or is
         expected by Diablo to be  incurred by Diablo with  respect to any Plan,
         and there has been no event or condition which presents a material risk
         of termination of any Plan by the PBGC;

                  (xiii) except as set forth in Section 3.12(xiii) of the Diablo
         Disclosure  Schedule,  Diablo  is not and never has been a party to any
         Multiemployer Plan or made contributions to any such Plan;

                  (xiv)  except  as set  forth in  Section  3.12(a)(xiv)  of the
         Diablo Disclosure Schedule (which entry, if applicable,  shall indicate
         the present  value of  accumulated  plan  liabilities  calculated  in a
         manner  consistent  with FAS 106 and  actual  annual  expense  for such
         benefits  for each of the  last  two (2)  years)  and  pursuant  to the
         provisions  of COBRA,  Diablo does not maintain any Plan that  provides
         benefits  described in Section 3(1) of ERISA,  except as the provisions
         of COBRA may apply, to any former employees or retirees of Diablo; and

                  (xv) Diablo has made  available  to ATS a copy of the two most
         recently filed Federal Form 5500 series and  accountant's  opinion,  if
         applicable,  for each Plan (and the two most recent actuarial valuation
         reports for each Plan,  if any,  that is subject to Title IV of ERISA),
         and all  information  provided by Diablo to any  actuary in  connection
         with the preparation of any such actuarial  valuation  report was true,
         accurate and complete in all material respects.


                                      -14-


<PAGE>



         (b) The execution, delivery and performance by Diablo of this Agreement
and the Collateral Documents executed or required to be executed pursuant hereto
and thereto will not involve any  prohibited  transaction  within the meaning of
ERISA or Section 4975 of the Code.

         3.13 Absence of  Sensitive  Payments.  Neither  Diablo nor, to Diablo's
knowledge,  any  of  its  officers,   directors,   employees,  agents  or  other
representatives,  has with respect to the Diablo  Assets or the Diablo  Business
(a) made any  contributions,  payments or gifts to or for the private use of any
governmental official, employee or agent where either the payment or the purpose
of such  contribution,  payment or gift is illegal  under the laws of the United
States or the  jurisdiction  in which made or (b)  established or maintained any
unrecorded fund or asset for any purpose or made any false or artificial entries
on its books.

         3.14  Inapplicability of Specified  Statutes.  Diablo is not a "holding
company", or a "subsidiary company" or an "affiliate" of a "holding company", as
such terms are defined in the Public  Utility  Holding  Company Act of 1935,  as
amended,  or an "investment  company" or a company  "controlled" by or acting on
behalf of an "investment  company",  as defined in the Investment Company Act of
1940, as amended, or a "carrier" or a person which is in control of a "carrier",
as defined in section 11301 of Title 49, U.S.C.

         3.15  Employment  Arrangements.  Section 3.15 of the Diablo  Disclosure
Schedule  contains a true,  accurate and complete  list of all Diablo  employees
involved in the  ownership or  operation of the Diablo  Assets or the conduct of
the Diablo Business (the "Diablo Employees"), together with each such employee's
title or the capacity in which he or she is employed and the basis for each such
employee's  compensation.  Diablo has no obligation or liability,  contingent or
other,  under any Employment  Arrangement with any Diablo  Employee,  other than
those listed or described  in Section  3.15 of the Diablo  Disclosure  Schedule.
Except as described in Section 3.15 of the Diablo Disclosure Schedule,  (i) none
of the Diablo  Employees is now,  or, to Diablo's  knowledge,  since  January 1,
1993,  has been,  represented  by any labor union or other  employee  collective
bargaining  organization,  and Diablo is not, and has never been, a party to any
labor or other collective bargaining agreement with respect to any of the Diablo
Employees, (ii) there are no pending grievances,  disputes or controversies with
any union or any other employee or collective  bargaining  organization  of such
employees,  or threats of strikes,  work  stoppages  or slowdowns or any pending
demands for collective bargaining by any such union or other organization, (iii)
neither Diablo nor any of such employees is now, or, to Diablo's knowledge,  has
since January 1, 1993 been, subject to or involved in or, to Diablo's knowledge,
threatened   with,   any  union   elections,   petitions   therefore   or  other
organizational or recruiting activities, in each case with respect to the Diablo
Employees and (iv) none of the Diablo  Employees has notified  Diablo in writing
that he or she does not intend to  continue  employment  with  Diablo  until the
Closing or with ATS following the Closing.  Diablo has performed in all material
respects  all  obligations   required  to  be  performed  under  all  Employment
Arrangements  and is not in  material  breach  or  violation  of or in  material
default or arrears under any of the terms, provisions or conditions thereof.

         3.16  Material  Agreements.  Listed  on  Section  3.16  of  the  Diablo
Disclosure  Schedule are all Material  Agreements  relating to the  ownership or
operation  of the Diablo  Assets or the  conduct of the  business  of the Diablo
Business  or to which  Diablo is a party or to which it is bound or which any of
the Diablo Assets is subject. True, accurate and complete copies of each of such
Material  Agreements have been provided by Diablo to ATS to the extent requested
by ATS (or true, accurate and complete  descriptions thereof have been set forth
in Section  3.16 of the Diablo  Disclosure  Schedule,  with  respect to Material
Agreements that are oral).  All of such Material  Agreements are valid,  binding
and legally enforceable  obligations of Diablo and, to Diablo's  knowledge,  all
other  parties  thereto,  except  as  such  enforceability  may  be  limited  by
bankruptcy,  moratorium,  insolvency  and similar laws  affecting the rights and
remedies  of  creditors  and  obligations  of debtors  generally  and by general
principles of equity.  Diablo has duly  complied with all of the material  terms
and conditions of each such Material Agreement and has not done or performed, or
failed to do or perform (and there is no pending or, to the knowledge of Diablo,
Claim threatened in writing

                                      -15-


<PAGE>



that Diablo has not so complied, done and performed or failed to do and perform)
any act which would invalidate or provide grounds for the other party thereto to
terminate  (with or  without  notice,  passage  of time or both)  such  Material
Agreement  or impair the rights or benefits,  or increase  the costs,  of Diablo
under any of such Material Agreements in any material respect.

         3.17  Ordinary  Course  of  Business.  From the end of its most  recent
fiscal  quarter to the date  hereof,  except (i) as may be  described on Section
3.17 of the Diablo Disclosure Schedule,  or (ii) as may be required or expressly
contemplated by the terms of this Agreement or the Letter of Intent,  Diablo has
operated the Diablo Business in all material  respects in the normal,  usual and
customary manner in the ordinary and regular course of business, consistent with
prior  practice,  and,  except in each case in the ordinary  course of business,
consistent with prior practice,

                  (a) has not  incurred  any  obligation  or  liability  (fixed,
         contingent or other) individually having a value in excess of $20,000;

                  (b) has not sold or  otherwise  disposed of or  contracted  to
         sell or otherwise  dispose of any of its  properties or assets having a
         value in excess of $20,000;

                  (c) has not entered into any  individual  commitment  having a
         value in excess of $20,000;

                  (d) has not canceled any debts or claims;

                  (e) has not created or permitted to be created any Lien on any
         of its property;

                  (f) has not made or  committed  to make any  additions  to its
         property or any purchases of equipment,  except in the ordinary  course
         of business consistent with past practice or for normal maintenance and
         replacements;

                  (g) has not  increased the  compensation  payable or to become
         payable  to any of the  Diablo  Employees  other  than in the  ordinary
         course of business or otherwise materially altered, modified or changed
         the terms of their employment;

                  (h) has not suffered any material damage,  destruction or loss
         (whether or not covered by insurance) or any  acquisition  or taking of
         property by any Authority;

                  (i) has not waived any rights of material  value  without fair
         and adequate consideration;

                  (j) has not experienced any work stoppage;

                  (k) has not entered  into,  amended or  terminated  any Lease,
         Governmental Authorization,  Private Authorization,  Material Agreement
         or Employment Arrangement, or any transaction, agreement or arrangement
         with any Affiliate of Diablo, except for Diablo Nonassumed Obligations;
         and

                  (l) has not entered  into any other  transaction  or series of
         related transactions which individually or in the aggregate is material
         to the Diablo Assets or the Diablo Business.

         3.18 Material and Adverse Restrictions.  To Diablo's knowledge,  Diablo
is not a party to or subject  to, nor are any of the Diablo  Assets  subject to,
any  Applicable  Law,  Governmental   Authorization,   Contractual   Obligation,
Employment Arrangement, Material Agreement or Private Authorization, or any

                                      -16-


<PAGE>



other  obligation or restriction of any kind or character,  which now has or, as
far  as  Diablo  can  now  reasonably  foresee,  at  any  time  in  the  future,
individually or in the aggregate, is likely to have, any material adverse effect
on  Diablo,  except  as set  forth  in  Section  3.18 of the  Diablo  Disclosure
Schedule.

         3.19  Broker or Finder.  No Person  assisted  in or  brought  about the
negotiation  of this  Agreement or the  Transactions  in the capacity of broker,
agent or finder or in any similar capacity on behalf of Diablo.

         3.20  Solvency.  As of the  execution  and delivery of this  Agreement,
Diablo is, and immediately  prior to and after giving effect to the consummation
of the Transactions will be, solvent.

         3.21 Environmental Matters.  Except as set forth in Section 3.21 of the
Diablo Disclosure Schedule, with respect to the Diablo Assets, Diablo:

                  (a) has not been notified that it is potentially liable under,
         has not received any request for  information  or other  correspondence
         concerning its potential liability with respect to any site or facility
         under, and, to Diablo's  knowledge,  is not a "potentially  responsible
         party" under, the Comprehensive  Environmental  Response,  Compensation
         and  Liability  Act of 1980,  as  amended,  the  Resource  Conservation
         Recovery Act, as amended, or any similar state law;

                  (b) has not  entered  into or  received  any  consent  decree,
         compliance  order  or  administrative  order  issued  pursuant  to  any
         Environmental Law;

                  (c) is  not a  party  in  interest  or in  default  under  any
         judgment,  order, writ,  injunction or decree of any final order issued
         pursuant to any Environmental Law;

                  (d) is, to the  knowledge  of  Diablo,  in  compliance  in all
         material  respects  with  all  Environmental  Laws,  has,  to  Diablo's
         knowledge,   obtained  all   Environmental   Permits   required   under
         Environmental  Laws,  and  is  not  the  subject  of  or,  to  Diablo's
         knowledge,  threatened  with any Legal  Action  involving  a demand for
         damages or other potential liability including any Lien with respect to
         material violations or material breaches of any Environmental Law; and

                  (e) has no knowledge of any past or present  Event  related to
         the Diablo  Business or the Diablo Assets which Event,  individually or
         in the aggregate,  will interfere  with or prevent  continued  material
         compliance with all  Environmental  Laws, or which,  individually or in
         the  aggregate,  will  form the  basis of any  material  Claim  for the
         release or threatened  release into the  environment,  of any Hazardous
         Material.


                                    ARTICLE 4

                      REPRESENTATIONS AND WARRANTIES OF ATS

         ATS represents,  warrants and covenants to, and agrees with,  Diablo as
follows:

         4.1  Organization  and  Business;   Power  and  Authority;   Effect  of
Transaction.

         (a) ATS is a corporation  duly organized,  validly existing and in good
standing  under  the  laws  of its  jurisdiction  of  incorporation  and has all
requisite  power and authority  (corporate and other) to own or hold under lease
its properties and to conduct its business as now conducted.


                                      -17-


<PAGE>



         (b) ATS has all  requisite  corporate  power  and  corporate  authority
necessary  to enable it to execute and deliver,  and to perform its  obligations
under,  this Agreement and each Collateral  Document  executed or required to be
executed by it pursuant hereto or thereto or to consummate the Transactions; and
the execution,  delivery and  performance of this Agreement and each  Collateral
Document  executed or  required to be executed by it pursuant  hereto or thereto
have been duly authorized by all requisite corporate or other action on the part
of  ATS.  This  Agreement  has  been  duly  executed  and  delivered  by ATS and
constitutes, and each Collateral Document executed or required to be executed by
it pursuant  hereto or thereto or to consummate the  Transactions  when executed
and delivered by ATS will constitute,  legal,  valid and binding  obligations of
ATS,  enforceable  in accordance  with their  respective  terms,  except as such
enforceability may be limited by bankruptcy,  moratorium, insolvency and similar
laws  affecting  the rights and remedies of  creditors  and the  obligations  of
debtors generally and by general principles of equity.

         (c) Except for matters which would not have any material adverse effect
on ATS,  neither the  execution  and  delivery by ATS of this  Agreement  or any
Collateral Document executed or required to be executed by it pursuant hereto or
thereto,  nor the consummation by ATS of the  Transactions,  nor compliance with
the terms, conditions and provisions hereof or thereof by ATS:

                  (i) will conflict with, or result in a breach or violation of,
         or  constitute  a default  under,  any  Organic  Document of ATS or any
         Applicable  Law on the part of ATS, or will conflict with, or result in
         a breach or violation of, or constitute a default under,  or permit the
         acceleration  of  any  obligation  or  liability  in,  or but  for  any
         requirement  of  giving  of notice  or  passage  of time or both  would
         constitute  such a conflict  with,  breach or violation  of, or default
         under, or permit any such  acceleration in, any Contractual  Obligation
         of ATS; or

                  (ii)  will  require  ATS to make or  obtain  any  Governmental
         Authorization,  Governmental Filing or Private Authorization  including
         without  limitation  under  the  FCA,  except  for  filings  under  the
         Hart-Scott-Rodino Act.

         4.2  Broker or  Finder.  No Person  assisted  in or  brought  about the
negotiation  of this  Agreement or the  Transactions  in the capacity of broker,
agent or finder or in any similar capacity on behalf of ATS.

         4.3 Solvency.  As of the execution and delivery of this Agreement,  ATS
is, and immediately  prior to and after giving effect to the consummation of the
Transactions will be, solvent.

         4.4 No Legal  Action.  There are no Legal  Actions  pending  or, to the
knowledge  of ATS,  threatened  against ATS or any of its  Affiliated  Entities,
officers  or  directors,  that  question  or may  affect  the  validity  of this
Agreement  or the  right  of ATS to  consummate  the  transactions  contemplated
hereunder.


                                    ARTICLE 5

                                    COVENANTS

         5.1      Access to Information; Confidentiality.

         (a) Diablo shall afford to ATS and its accountants,  counsel,  lenders,
financial advisors and other representatives (the "Representatives") full access
during normal business hours  throughout the period prior to the Closing Date to
all of Diablo's properties, books, contracts, commitments and records (including
without  limitation  Tax Returns)  relating to the Diablo  Assets and the Diablo
Business and, during such period, shall furnish promptly upon request (i) a list
(and copies to the extent requested by ATS) of each

                                      -18-


<PAGE>



report,  schedule and other document filed or received by Diablo pursuant to the
requirements  of any  Applicable  Law or  filed  by it  with  any  Authority  in
connection with the  Transactions or which may have a material adverse effect on
the  Diablo  Assets  or  the  Diablo  Business  or the  businesses,  operations,
properties,  prospects, personnel, condition (financial or other), or results of
operations  thereof,  (ii)  to the  extent  not  provided  for  pursuant  to the
preceding clause, all financial records,  ledgers, work papers and other sources
of financial  information  possessed and controlled by Diablo or its accountants
reasonably  deemed by ATS or its  Representatives  necessary  or useful  for the
purpose of performing an audit of the Diablo Assets and the Diablo  Business and
certifying financial statements and financial information,  and (iii) such other
information in the possession or control of Diablo or its accountants concerning
any of the foregoing as ATS shall reasonably request;  provided,  however,  that
Diablo  shall not be required to permit any such access to the extent same would
unreasonably interfere with Diablo's normal business operations.  All non-public
information relating to the Diablo Assets or the Diablo Business furnished prior
to the execution,  or pursuant to the provisions,  of this Agreement,  including
without  limitation  this  Section,  will be kept  confidential  and shall  not,
without the prior written  consent of Diablo,  be disclosed by ATS in any manner
whatsoever,  in whole or in part, and shall not be used for any purposes,  other
than in connection  with the  Transactions.  In no event shall ATS or any of its
Representatives  use such information to the detriment of Diablo.  ATS agrees to
reveal such  information only to those of its  Representatives  or other Persons
who  need  to  know  such   information   for  the  purpose  of  evaluating  the
Transactions,  who are informed of the  confidential  nature of such information
and who shall  undertake to act in accordance  with the terms and  conditions of
this Agreement.  From and after the Closing, Diablo shall not, without the prior
written  consent of ATS,  disclose any  information  remaining in its possession
with  respect  to  the  Diablo  Assets  or the  Diablo  Business,  and  no  such
information  shall be used for any purposes,  other than in connection  with the
Transactions or to the extent required by Applicable Law.

         (b) Subject to the terms and  conditions  of Section  5.1(a),  ATS may,
subject to prior  consultation with Diablo,  disclose such information as may be
necessary in connection with seeking all Governmental and Private Authorizations
or that is required by Applicable  Law to be  disclosed.  In the event that this
Agreement  is  terminated  for any  reason,  ATS shall  promptly  redeliver  all
non-public  written  material  provided  pursuant  to this  Section or any other
provision of this Agreement or otherwise in connection with the Transactions and
shall not retain any copies, extracts or other reproductions in whole or in part
of such written  material,  other than one copy thereof which shall be delivered
to independent  counsel for ATS (which  independent  counsel shall be subject to
the provisions of Section 5.1(a)), and ATS shall so certify to such effect.

         (c)  Anything in this  Section or  elsewhere  in this  Agreement to the
contrary  notwithstanding,  either  party may disclose  information  received or
retained by it in accordance  with the  provisions  of this  Agreement if it can
demonstrate  (i) such  information  is  generally  available  to or known by the
public from a source other than the party seeking to disclose  such  information
or (ii) was obtained by the party  seeking to disclose such  information  from a
source other than the other party,  provided that such source was not bound by a
duty of confidentiality to the other party or another party with respect to such
information.

         5.2      Agreement to Cooperate.

         (a) Each of the parties  hereto shall use reasonable  business  efforts
(x) to take,  or cause to be taken,  all actions and to do, or cause to be done,
all things necessary, proper or advisable under Applicable Law to consummate the
Transactions,  and (y) to refrain from taking,  or cause to be taken, any action
and to refrain from doing or causing to be done, any thing which could impede or
impair the consummation of the Transactions,  including,  in all cases,  without
limitation  using its reasonable  business  efforts (i) to prepare and file with
the applicable  Authorities  as promptly as  practicable  after the execution of
this Agreement all requisite applications and amendments thereto,  together with
related information,  data and exhibits, necessary to request issuance of orders
approving the Transactions by all such applicable Authorities, each of which

                                      -19-


<PAGE>



must be obtained or become final to the extent provided in Section 6.1(a),  (ii)
to  obtain  all  necessary  or  appropriate  waivers,  consents  and  approvals,
including  without  limitation  those  referred  to in Section  6.2(d),  without
payment of any material  amount of  compensation,  (iii) to effect all necessary
registrations,  filings and submissions  (including  without  limitation filings
under the  Hart-Scott-Rodino  Act and all filings  necessary  for ATS to own and
operate the Diablo  Assets and conduct  the Diablo  Business),  (iv) to lift any
injunction or other legal bar to the Transactions (and, in such case, to proceed
with the  Transactions  as  expeditiously  as  possible),  and (v) to obtain the
satisfaction  of the  conditions  specified  in  Article  6,  including  without
limitation the truth and correctness as of the Closing Date as if made on and as
of the Closing Date of the  representations and warranties of such party and the
performance  and  satisfaction  as of the  Closing  Date of all  agreements  and
conditions to be performed or satisfied by such party.

         (b) The parties shall  cooperate  with one another in the  preparation,
execution and filing of all Tax Returns, questionnaires,  applications, or other
documents  regarding any real property transfer or gains,  sales, use, transfer,
value  added,   stock  transfer  and  stamp  Taxes,  any  transfer,   recording,
registration  and other fees,  and any similar  Taxes  which  become  payable in
connection with the  Transactions  that are required or permitted to be filed on
or before the Closing Date.

         (c) Diablo  shall,  at ATS' expense,  cooperate and use its  reasonable
business  efforts to (i) prepare its financial  statements  for the period ended
December  31, 1996 and  thereafter  in  accordance  with GAAP and (ii) cause its
independent  accountants to reasonably  cooperate with ATS, and at ATS' expense,
in order to  enable  ATS to have its  independent  accountants  prepare  audited
financial  statements  for the Diablo  Business  described  in  Section  6.2(g).
Without  limiting the generality of the foregoing,  Diablo agrees that after the
Closing Date it will (x) if required by the  Securities Act or the Exchange Act,
consent to the use of such  audited  financial  statements  in any  registration
statement  or other  document  filed by ATS or any  Affiliate  of ATS  under the
Securities  Act or the  Exchange  Act and (y) if  reasonably  requested  by ATS'
independent accountants,  execute and deliver, and cause its officers to execute
and  deliver,  such  "representation"  letters as are  customarily  delivered in
connection with audits under comparable circumstances.

         5.3  Public  Announcements.  Until  the  Closing,  or in the  event  of
termination  of this  Agreement,  Diablo  and ATS shall  consult  with the other
before issuing any press release or otherwise making any public  statements with
respect to this Agreement or the Transactions and shall not issue any such press
release  or make any such  public  statement  without  the prior  consent of the
other.  Notwithstanding  the foregoing,  each party acknowledges and agrees that
Diablo and ATS may, without the other's prior consent, issue such press releases
or make such public  statements as may be required by  Applicable  Law, in which
case, to the extent practicable,  the party proposing to make such press release
or public statement will consult with the other regarding the nature, extent and
form of such press  release or public  statement.  In  addition,  subject to the
terms  and  conditions  hereof,  ATS may  disclose  the  subject  matter of this
Agreement to Persons with whom Diablo has a business or contractual relationship
in  connection  with  ATS' due  diligence  investigation  of  Diablo;  provided,
however,  that prior to (i) ATS sending any  written  communication  to any such
Person,  ATS shall  secure the written  approval of the form and content of such
communication,  such  approval  not  to be  unreasonably  withheld,  delayed  or
conditioned,  and (ii)  any  verbal  or in  person  communication  with any such
Person, ATS shall provide Diablo with the opportunity to participate with ATS in
any such conversation or meeting.

         5.4 Notification of Certain Matters. Diablo and ATS shall, prior to the
Closing, give prompt notice to the other, of the occurrence or non-occurrence of
any Event the occurrence or non-occurrence of which would be likely to cause (i)
any  representation  or warranty  made by it contained  in this  Agreement to be
untrue  or  inaccurate  in any  material  respect  such  that one or more of the
conditions of Closing might not be satisfied, or (ii) any covenant, condition or
agreement  made by it contained  in this  Agreement  not to be complied  with or
satisfied,  or (iii) any change to be made in the Diablo Disclosure  Schedule in
any respect

                                      -20-


<PAGE>



such that one or more of the  conditions of Closing might not be satisfied,  and
any failure  made by it to comply with or satisfy,  or be able to comply with or
satisfy,  any covenant,  condition or agreement to be complied with or satisfied
by it  hereunder  in any  respect  such  that one or more of the  conditions  of
Closing  might not be  satisfied;  provided,  however,  that the delivery of any
notice pursuant to this Section shall not limit or otherwise affect the remedies
available hereunder to the party receiving such notice.

         5.5 No  Solicitation.  So long as this  Agreement  remains  in  effect,
Diablo  shall not,  nor shall it  knowingly  permit  any of its  Representatives
(including,  without limitation, any investment banker, broker, finder, attorney
or accountant retained by it) to, initiate,  solicit or facilitate,  directly or
indirectly,  any  inquiries  or the making of any  proposal  with respect to any
Alternative  Transaction,  engage in any discussions or negotiations concerning,
or provide to any other Person any  information  or data  relating to, it or any
Subsidiary for the purposes of, or otherwise cooperate in any way with or assist
or  participate  in, or  facilitate  any inquiries or the making of any proposal
which constitutes,  or may reasonably be expected to lead to, a proposal to seek
or effect any  Alternative  Transaction,  or agree to or endorse any Alternative
Transaction.  "Alternative Transaction" means a transaction or series of related
transactions  (other  than the  Transactions)  resulting  in (i) any  merger  or
consolidation,  regardless of whether Diablo is the surviving  Entity unless the
surviving Entity remains obligated under this Agreement to the same extent as it
was, or (ii) any sale or other disposition of all or any substantial part of the
Diablo Assets or the Diablo Business. The provisions of this Section shall apply
to  each of  Diablo's  Subsidiaries.  If  Diablo  or any of its  Representatives
receives  any inquiry  with  respect to an  Alternative  Transaction  while this
Agreement is in effect,  Diablo shall inform the inquiring  party that it is not
entitled to enter into  discussions or  negotiations  relating to an Alternative
Transaction.

         5.6  Conduct of  Business  by Diablo  Pending  the  Closing.  Except as
otherwise contemplated by this Agreement, after the date hereof and prior to the
Closing  Date  or  earlier  termination  of this  Agreement,  unless  ATS  shall
otherwise  agree in writing,  Diablo shall, to the extent relating to the Diablo
Business or the Diablo Assets:

                  (a) conduct its  business in the  ordinary and usual course of
         business  and  consistent   with  past  practice,   including   without
         limitation the performance of such maintenance, repairs or replacements
         with respect to communication  towers,  fixtures and Personal  Property
         comprising the Diablo Assets as is consistent with past practice;

                  (b) use all reasonable business efforts to preserve intact its
         business organizations and goodwill, keep available the services of its
         present  key   employees,   and  preserve  the  goodwill  and  business
         relationships  with customers and others having business  relationships
         with it;

                  (c) to the extent permitted under  Applicable Law, confer,  as
         and when reasonably requested, on a regular and frequent basis with one
         or more  representatives of ATS to report material  operational matters
         and the general status of ongoing operations;

                  (d) maintain with financially  responsible insurance companies
         insurance  on its assets and its  business in such  amounts and against
         such risks and losses as are consistent with past practice;

                  (e) use reasonable  business efforts to (i) operate the Diablo
         Business in conformity in all material  respects with all  Governmental
         and Private  Authorizations,  Leases and Material Agreements on a basis
         consistent  with past  practice  and  Applicable  Law and the rules and
         regulations of any Authority with  jurisdiction  over the Diablo Assets
         or the Diablo Business,  and (ii) maintain in full force and effect all
         such  Governmental  and  Private  Authorizations,  Leases and  Material
         Agreements relating to the Diablo Business;

                                      -21-


<PAGE>




                  (f)  except  as set  forth in  Section  5.6(f)  of the  Diablo
         Disclosure Schedule,  not (i) dispose of any of the Diablo Assets owned
         by Diablo or used in the operation of the Diablo  Business  (other than
         for the  disposition  in the ordinary  course of business of immaterial
         assets  that are of no  further  use to the  Diablo  Business)  or (ii)
         modify or change in any material  respect,  or enter into, any Material
         Agreement relating to the Diablo Business; and

                  (g) not voluntarily take any action which if taken between the
         end of its most  recent  fiscal  quarter  and prior to the date of this
         Agreement  would  have been  required  to be noted as an  exception  on
         Section 3.17 of the Diablo Disclosure Schedule.

With respect to any  transaction or act proposed to be entered into or performed
by Diablo which,  pursuant to this Section 5.6,  requires the prior  approval of
ATS,  ATS shall be deemed to have  approved  the same unless  written  notice of
disapproval is received by Diablo within five (5) business days after receipt by
ATS of a written request for approval made by Diablo.

         5.7  Preliminary  Title Reports.  As promptly as practicable  after the
execution of this Agreement, Diablo shall, at its sole cost and expense, deliver
or cause to be delivered to ATS a standard  preliminary title report dated on or
after the date of this Agreement  issued by such title company as Diablo and ATS
shall  mutually  reasonably  agree (the "Title  Company")  with respect to those
Diablo Assets comprised of the parcels of real property described in Section 5.7
of the Diablo Disclosure  Schedule (the "Insured Real Property").  Such reports,
as same may be amended or supplemented  from time to time to reflect  additional
title  matters,  are referred to herein as the "Title  Reports".  The rights and
obligations of the parties shall thereafter be as follows:

                  (a) On or before fifteen (15) business days after ATS' receipt
         of the last of the  Title  Reports,  ATS shall  give to Diablo  written
         notice ("ATS' Title  Notice") of ATS'  disapproval of any matters shown
         in the Title  Reports.  ATS' failure to give ATS' Title  Notice  within
         such  fifteen (15)  business  days shall be deemed to  constitute  ATS'
         approval of all matters disclosed by the Title Reports;

                  (b) If ATS  disapproves  any title  matters  pursuant  to ATS'
         Title Notice,  Diablo shall deliver  written  notice  ("Diablo's  Title
         Notice") to ATS within ten (10) business days after Diablo's receipt of
         ATS' Title Notice,  stating  whether  Diablo  agrees to eliminate  such
         disapproved title matters from title to the Insured Real Property prior
         to the Closing or, if such  elimination  is not  feasible  prior to the
         Closing,  to effect such  elimination  thereafter  and to indemnify and
         hold  harmless  ATS with  respect to such  remedy.  If Diablo  fails to
         timely deliver  Diablo's Title Notice,  or if Diablo delivers  Diablo's
         Title  Notice but states  therein that Diablo is unwilling or unable to
         eliminate  such  disapproved  title  matters,   ATS  and  Diablo  shall
         negotiate  in good faith in an attempt to  resolve  such  matters  (the
         "Disapproved  Title  Sites"  and,  collectively  with the  "Disapproved
         Environmental  Sites", the "Disapproved Sites") from the Diablo Assets,
         a reduction of the Purchase  Price or an  indemnification  (and escrow)
         from  Diablo  (not  subject  to the  limitations  as to time or  amount
         specified  in Article 8). If within  twenty (20)  business  days of the
         commencement  of such  negotiations  (or such longer  period as ATS and
         Diablo  shall  agree),  the parties  have been  unable to resolve  such
         matters,  either party can  terminate  this  Agreement  pursuant to the
         provisions  of Section  7.1(f) within ten (10) business days of the end
         of such negotiation period; and

                  (c) If,  at any time  following  ATS'  approval  of the  Title
         Reports,  Diablo or the Title  Company  notifies ATS of any  additional
         matter affecting title to the Insured Real Property, the

                                      -22-


<PAGE>



         parties shall have substantially the same rights and obligations as are
         set forth in paragraphs (a) and (b) above.

         5.8 Environmental  Site  Assessments.  As promptly as practicable after
the execution of this Agreement, ATS may at its own cost and expense obtain, and
deliver to Diablo  full and  complete  copies  of,  Phase I  environmental  site
assessment reports (the "Environmental  Reports") on any or all of those certain
parcels  of real  property  described  on Section  5.8 of the Diablo  Disclosure
Schedule.   Site  assessments   shall  be  conducted  by  such  consultants  and
professionals  as  ATS  and  Diablo  shall  mutually  agree  (collectively,  the
"Environmental Company"),  shall be arranged at times mutually convenient to the
parties,  and shall be conducted in a manner  which does not  interfere  with or
inconvenience  in any material  manner any of the landlords or tenants at any of
Diablo's sites. Each of Diablo and ATS shall be entitled to have representatives
present at the time such site  assessments are conducted,  and to have copies of
all correspondence with the Environmental Company:

                  (a) On or before fifteen (15) business days after ATS' receipt
         of the last of the  Environmental  Reports,  ATS  shall  give to Diablo
         written notice ("ATS' Environmental Notice") of ATS' disapproval of any
         matters shown in the Environmental  Reports.  ATS' failure to give ATS'
         Environmental  Notice  within such fifteen (15)  business days shall be
         deemed to  constitute  ATS'  approval of all matters  disclosed  by the
         Environmental Reports;

                  (b) If ATS disapproves any  environmental  matters pursuant to
         ATS'  Environmental   Notice,   Diablo  shall  deliver  written  notice
         ("Diablo's  Environmental Notice") to ATS within ten (10) business days
         after Diablo's receipt of ATS'  Environmental  Notice,  stating whether
         Diablo  agrees to eliminate and remedy such matter prior to the Closing
         or, if such elimination or remedy is not feasible prior to the Closing,
         to effect such  elimination and remedy  thereafter and to indemnify and
         hold  harmless  ATS with  respect to such  remedy.  If Diablo  fails to
         timely deliver  Diablo's  Environmental  Notice,  or if Diablo delivers
         Diablo's  Environmental  Notice  but  states  therein  that  Diablo  is
         unwilling or unable to eliminate and remedy such environmental matters,
         ATS and Diablo  shall  negotiate in good faith in an attempt to resolve
         such matters (the  "Disapproved  Environmental  Sites") from the Diablo
         Assets,  a reduction of the Purchase Price or an  indemnification  (and
         escrow)  from  Diablo  (not  subject to the  limitations  as to time or
         amount  specified in Article 8). If within twenty (20) business days of
         the commencement of such negotiations (or such longer period as ATS and
         Diablo  shall  agree),  the parties  have been  unable to resolve  such
         matters,  either party can  terminate  this  Agreement  pursuant to the
         provisions  of Section  7.1(f) within ten (10) business days of the end
         of such negotiation period; and

                  (c)  If,  at  any  time   following   ATS'   approval  of  the
         Environmental Reports, ATS or the Environmental Company notifies Diablo
         of  any  additional   environmental  matter,  the  parties  shall  have
         substantially  the same  rights  and  obligations  as are set  forth in
         paragraphs (a) and (b) above.

         5.9  Post-Closing  Covenants and  Agreements  of the Parties.  From and
after the consummation of the Transactions, ATS and Diablo covenant and agree as
follows:

                  (a) Diablo shall have the right,  if it shall have so notified
         ATS not later  than five (5)  business  days prior to the  Closing,  to
         retain (or to cause any of its  Affiliates  to retain) the  services of
         each  of  the  individuals  named  in  Section  5.9(a)  of  the  Diablo
         Disclosure Schedule;

                  (b) ATS shall  afford to Diablo,  and Diablo  shall  afford to
         ATS, access to their  respective  employees who were (or in the case of
         Diablo who remain)  employees  of Diablo on the Closing Date to the end
         that such employees are available to provide  assistance,  consultation
         and historical

                                      -23-


<PAGE>



         background to the requesting party; provided, however, that neither ATS
         nor Diablo shall have any such obligation  after the expiration of five
         (5) years from the Closing  Date or to the extent that it would  exceed
         an average of four (4) hours per week over such period; and

                  (c) ATS shall  afford to Diablo,  and Diablo  shall  afford to
         ATS,  access to all books and records  delivered  to ATS or retained by
         Diablo,  as the case may be,  relating to periods  prior to the Closing
         Date,  in order to enable Diablo or ATS, as the case may be, to prepare
         all  necessary  Tax  Returns,  deal with Legal  Actions or other Claims
         (including without limitation those of the Internal Revenue Service) or
         personnel  matters  or for  any  other  reasonable  purposes,  subject,
         however,  in all events,  to the provisions of Section 5.1 with respect
         to   confidentiality.   Anything  in  this   Section  to  the  contrary
         notwithstanding,  Diablo and ATS shall  cooperate fully in the event of
         an Internal  Revenue  Service  audit or  investigation  related to this
         Agreement,  including without limitation providing each other with full
         and complete access to each other's records and employees to the extent
         necessary to respond to any such audit or investigation.


                                    ARTICLE 6

                               CLOSING CONDITIONS

         6.1 Conditions to Obligations of Each Party to effect the Transactions.
The  respective  obligations  of each  party to effect the  Transactions  shall,
except as hereinafter  provided in this Section,  be subject to the satisfaction
at or prior to the Closing Date of the following conditions, any or all of which
may be waived, in whole or in part, to the extent permitted by Applicable Law:

                  (a) All authorizations, consents, waivers, orders or approvals
         required  to  be  obtained  from  all  Authorities,  and  all  filings,
         submissions, registrations, notices or declarations required to be made
         by ATS and Diablo with any Authority,  prior to the consummation of the
         Transactions,  shall have been obtained  from,  and made with, all such
         Authorities, except for such authorizations, consents, waivers, orders,
         approvals, filings,  registrations,  notices or declarations as are set
         forth in  Section  6.1(a)  of the  Diablo  Disclosure  Schedule  or the
         failure  to  obtain  or make  would  not,  in the  reasonable  business
         judgment of ATS,  have a material  adverse  effect on the Diablo Assets
         and the Diablo Business;

                  (b) The transactions contemplated by the Other Agreement shall
         have been consummated prior to or simultaneously  with the consummation
         of the Transactions; and

                  (c) The parties shall have entered into an escrow agreement in
         form, scope and substance  reasonably  satisfactory to the parties with
         the Title  Company or any other  Person  reasonably  acceptable  to the
         parties,  pursuant  to  which,  among  other  things,  ATS  shall  have
         deposited the portion of the Purchase Price not being  delivered to the
         Indemnity Escrow Agent or to a "qualified intermediary" pursuant to the
         provisions  of Section 2.3, and Diablo  shall have  delivered  deeds in
         customary  form with respect to all of the real property to be conveyed
         to ATS as part of the  Diablo  Assets  and the  parties,  to the extent
         required by Section 9.3, shall have  deposited an amount  sufficient to
         pay all  recording  fees,  transfer  taxes and other fees and  expenses
         which must be paid as a condition of consummation  of the  transactions
         contemplated by this Agreement.

         6.2  Conditions to  Obligations of ATS. The obligation of ATS to effect
the  Transactions  shall  be  subject  to  the  satisfaction  of  the  following
conditions,  any or all of which  may be  waived,  in  whole or in part,  to the
extent permitted by Applicable Law:

                                      -24-


<PAGE>




                  (a) All agreements, certificates, opinions and other documents
         required to be delivered  pursuant to the  provisions of this Agreement
         shall be reasonably  satisfactory  in form,  scope and substance to ATS
         and its  counsel,  and ATS and its  counsel  shall  have  received  all
         information and copies of all documents, including records of corporate
         proceedings, which they may reasonably request in connection therewith,
         such documents  where  appropriate to be certified by proper  corporate
         officers;

                  (b) Diablo shall have furnished ATS and, at ATS' request,  any
         bank or other  financial  institution  providing  credit to ATS, with a
         favorable  opinion,  dated the Closing Date of Cooper,  White & Cooper,
         counsel for Diablo,  with  respect to the matters set forth in Sections
         3.1(a),  (b) and (c),  3.7(b) and 3.14, and such other matters  arising
         after the date of this Agreement and incident to the  Transactions,  as
         ATS or its counsel or its counsel may  reasonably  request or which may
         be reasonably  requested by any such bank or financial  institution  or
         their respective counsel;

                  (c) The  representations and warranties of Diablo contained in
         this  Agreement  or  otherwise  made in  writing by it or on its behalf
         pursuant  hereto shall be true and correct in all material  respects at
         and as of the  Closing  Date with the same  force and  effect as though
         made on and as of such date  except  those  which speak as of a certain
         date  which  shall  continue  to be true and  correct  in all  material
         respects  as of  such  date  on the  Closing  Date  (including  without
         limitation  giving effect to any later obtained  knowledge of Diablo or
         ATS, except as otherwise specifically provided herein); each and all of
         the  covenants  and  agreements  and  conditions  to  be  performed  or
         satisfied  by Diablo  hereunder  at or prior to the Closing  Date shall
         have been duly  performed or satisfied  in all material  respects;  and
         Diablo  shall  have  furnished  ATS with  such  certificates  and other
         documents  evidencing  the truth of such  representations,  warranties,
         covenants and  agreements  and the  performance  of such  agreements or
         conditions as ATS or its counsel shall have reasonably requested;

                  (d) Except to the extent,  if any,  specifically  set forth in
         Section 6.2(d) of the Diablo Disclosure  Schedule,  all authorizations,
         consents,  waivers,  orders or approvals  required by the provisions of
         this Agreement to be obtained from all Persons (other than Authorities)
         prior  to the  consummation  of  the  Transactions,  including  without
         limitation  those required by the provisions of this Agreement in order
         to vest fully in ATS all right, title and interest in and to all of the
         Diablo Assets and the Diablo Business (including without limitation all
         Private Authorizations,  Leases and Material Agreements of Diablo), and
         the full  enjoyment  thereof  shall  have been  obtained,  without  the
         imposition,  individually  or in the  aggregate,  of any  condition  or
         requirement which could materially adversely affect ATS;

                  (e) Between the date of this  Agreement  and the Closing Date,
         there shall not have  occurred and be continuing  any material  adverse
         change  in  Diablo  from  that  reflected  in the  most  recent  Diablo
         Financial  Statements;   as  of  the  Closing  Date,  the  Governmental
         Authorizations with respect to the ownership or operation of the Diablo
         Assets  or the  conduct  of the  Diablo  Business  shall  not have been
         materially  and  adversely  affected  by any act, or failure to act, of
         Diablo;

                  (f) Diablo  shall have  delivered or caused to be delivered to
         ATS all of the Collateral Documents and other agreements, documents and
         instruments  required to be  delivered  by Diablo to ATS at or prior to
         the Closing pursuant to the terms of this Agreement;

                  (g) ATS shall have received from its  independent  accountants
         (i) an unqualified report (as to the scope of the audit,  access to the
         books and records and the cooperation of management) on

                                      -25-


<PAGE>



         the financial statements  (consisting of balance sheets for each of the
         fiscal  years  ended  December  31,  1995 and 1996  and  statements  of
         operations  and cash  flow for each of the  three  years in the  period
         ended December 31, 1996 or such shorter period since its  organization)
         of the Diablo  Business,  which  financial  statements  shall have been
         prepared  in  conformity   with  GAAP  and  Regulation  S-X  under  the
         Securities Act, or (ii) such other documentation as shall be reasonably
         satisfactory to ATS indicating that such an unqualified report could be
         issued if requested by ATS;

                  (h) As of the Closing  Date,  except as otherwise set forth in
         Section 3.7(a) of the Diablo Disclosure Schedule, no Legal Action shall
         be pending before or threatened in writing by any Authority  seeking to
         enjoin, restrain,  prohibit or make illegal or to impose any materially
         adverse   conditions  in  connection  with,  the  consummation  of  the
         Transactions,  or which might, in the reasonable  business  judgment of
         ATS, based upon the advice of counsel,  have a material  adverse effect
         on the Diablo Assets and the Diablo  Business,  it being understood and
         agreed that a written  request by any  Authority for  information  with
         respect  to the  Transactions,  which  information  could  be  used  in
         connection  with such Legal Action,  shall not be deemed to be a threat
         of any such Legal Action;

                  (i) All Environmental Reports obtained by the parties prior to
         the Closing Date pursuant to the provisions of Section 5.8 hereof shall
         be  approved  or deemed  approved  by ATS in the  manner  described  in
         Section 5.8;

                  (j) Richard D. Spight  ("Spight"),  the chairman and principal
         shareholder  of Diablo,  shall have  executed  and  delivered to ATS an
         agreement  substantially  in the form of Exhibit A attached  hereto and
         made a part hereof (the "Spight Noncompetition Agreement");

                  (k) Diablo and Spight shall have executed and delivered to ATS
         and the escrow agent named therein (the  "Indemnity  Escrow  Agent") an
         escrow agreement (the "Indemnity  Escrow  Agreement")  substantially in
         the form of Exhibit B attached hereto and made a part hereof;

                  (l) ATS shall have  received  standard  CLTA  title  insurance
         policies  insuring  ATS' fee  interests in all Insured  Real  Property,
         subject only to Approved Title Conditions;

                  (m)  Diablo  shall  have  delivered  to ATS all  use  permits,
         consents or other  Governmental  Authorizations  of and all Leases from
         the United  States  Forest  Service set forth in Section  6.2(m) of the
         Diablo Disclosure Schedule; and

                  (n)  Diablo  shall  have  executed  and  delivered  to  ATS an
         agreement,  in form, scope and substance reasonably satisfactory to ATS
         (the "Nonassignable Contracts Agreement"), pursuant to which (i) Diablo
         will hold (but will have no obligation to perform services  thereunder)
         for the account of ATS, and remit promptly to ATS all amounts  received
         pursuant to the provisions of, all of the Nonassignable Contracts as to
         which the required approval or consent to the assignment or transfer of
         which was not obtained and as to which ATS has  delivered an Acceptance
         Notice, and (ii) ATS will agree to (A) perform all services required to
         be performed under such Nonassignable  Contracts,  (B) reimburse Diablo
         for  all  costs  and  expenses  reasonably  incurred  pursuant  to  the
         Nonassignable  Contracts  Agreement and (C) indemnify and hold harmless
         Diablo with respect to all actions  taken by ATS  pursuant  thereto and
         all actions,  if any, taken by Diablo pursuant thereto other than those
         relating to the bad faith,  negligence or willful  misconduct of Diablo
         or its officers, directors, stockholders or employees.


                                      -26-


<PAGE>



         6.3 Conditions to  Obligations  of Diablo.  The obligation of Diablo to
effect the  Transactions  shall be subject to the  satisfaction of the following
conditions,  any or all of which  may be  waived,  in  whole or in part,  to the
extent permitted by Applicable Law:

                  (a) All agreements, certificates, opinions and other documents
         required to be delivered  pursuant to the  provisions of this Agreement
         shall be reasonably satisfactory in form, scope and substance to Diablo
         and its  counsel,  and Diablo and its counsel  shall have  received all
         information and copies of all documents, including records of corporate
         proceedings, which they may reasonably request in connection therewith,
         such documents  where  appropriate to be certified by proper  corporate
         officers;

                  (b) ATS shall have furnished Diablo and, at Diablo's  request,
         any bank of other  financial  institution  providing  credit to Diablo,
         with favorable opinions, dated the Closing Date of Sullivan & Worcester
         LLP,  counsel for ATS, with respect to the matters set forth in Section
         4.1 and with respect to such other  matters  arising  after the date of
         this  Agreement  and  incident  to the  Transactions,  as Diablo or its
         counsel may reasonably request or which may be reasonably  requested by
         any such bank or financial institution or their respective counsel;

                  (c) The  representations  and  warranties  of ATS contained in
         this  Agreement  or  otherwise  made in  writing by it or on its behalf
         pursuant  hereto shall be true and correct in all material  respects at
         and as of the  Closing  Date with the same  force and  effect as though
         made on and as of such date  except  those  which speak as of a certain
         date  which  shall  continue  to be true and  correct  in all  material
         respects  as of  such  date  on the  Closing  Date  (including  without
         limitation  giving effect to any later obtained  knowledge of Diablo or
         ATS, except as otherwise specifically provided herein); each and all of
         the  covenants  and  agreements  and  conditions  to  be  performed  or
         satisfied  by ATS  hereunder at or prior to the Closing Date shall have
         been duly  performed or satisfied  in all  material  respects;  and ATS
         shall have furnished Diablo with such  certificates and other documents
         evidencing the truth of such representations, warranties, covenants and
         agreements  and the  performance  of such  agreements  or conditions as
         Diablo or its counsel shall have reasonably requested;

                  (d) ATS  shall  have  delivered  or cause to be  delivered  to
         Diablo all of the Collateral Documents and other agreements,  documents
         and  instruments  required to be delivered by ATS to Diablo at or prior
         to the Closing pursuant to the terms of this Agreement;

                  (e) As of the Closing  Date,  no Legal Action shall be pending
         before or  threatened  in writing by any  Authority  seeking to enjoin,
         restrain,  prohibit or make illegal or to impose any materially adverse
         conditions in connection with, the consummation of the Transactions, it
         being understood and agreed that a written request by any Authority for
         information with respect to the  Transactions,  which information could
         be used in connection with such Legal Action, shall not be deemed to be
         a threat of any such Legal Action;

                  (f) ATS shall have  executed and  delivered to Diablo,  Spight
         and the Indemnity  Escrow Agent a counterpart  of the Indemnity  Escrow
         Agreement;

                  (g) ATS shall  have  executed  and  delivered  to  Diablo  the
         Nonassignable Contracts Agreement; and

                  (h) ATS shall  have  executed  and  delivered  to  Diablo  the
         Exclusivity Agreement.



                                      -27-


<PAGE>



                                    ARTICLE 7

                        TERMINATION, AMENDMENT AND WAIVER

         7.1 Termination.  This Agreement may be terminated at any time prior to
the Closing Date:

                  (a) by mutual consent of Diablo and ATS;

                  (b) by  either  ATS or  Diablo  if any  permanent  injunction,
         decree or judgment by any Authority  preventing the consummation of the
         Transactions shall have become final and nonappealable; or

                  (c) by  Diablo in the  event  (i)  Diablo  is not in  material
         breach of this Agreement and none of its  representations or warranties
         shall have become and  continue to be untrue in any  material  respect,
         and (ii) ATS is in  material  breach  of this  Agreement  or any of its
         representations  or  warranties  shall have  become and  continue to be
         untrue in any material respect, and such a breach or untruth exists and
         is not capable of being cured by and will prevent or delay consummation
         of the Transactions by or beyond the Termination Date; or

                  (d) by ATS in the event (i) ATS is not in  material  breach of
         this Agreement and none of its representations or warranties shall have
         become and  continue  to be untrue in any  material  respect,  and (ii)
         Diablo  is  in  material  breach  of  this  Agreement  or  any  of  its
         representations  or  warranties  shall have  become and  continue to be
         untrue in any material respect, and such a breach or untruth exists and
         is not capable of being cured by and will prevent or delay consummation
         of the Transactions by or beyond the Termination Date; or

                  (e) by ATS in the  event of a  failure  of the  condition  set
         forth in Section 6.2(i) or 6.2(l); or

                  (f) by ATS or Diablo  pursuant  to the  provisions  of Section
         5.7(b) or 5.8(b).

         The term "Termination Date" shall mean September 30, 1997 or such other
date as the parties may, from time to time, mutually agree.

         The right of ATS or Diablo to terminate this Agreement pursuant to this
Section shall remain  operative  and in full force and effect  regardless of any
investigation  made by or on behalf of either party, any Person  controlling any
such party or any of their respective  Representatives whether prior to or after
the execution of this Agreement.

         7.2      Effect of Termination.

         (a)   Except  as   provided   in   Sections   5.1  (with   respect   to
confidentiality),  5.3,  9.3 and  9.15  and this  Section,  in the  event of the
termination  of this  Agreement  pursuant  to Section  7.1,  or in the event the
Transactions shall not have been consummated prior to the end of business on the
Termination  Date, this Agreement shall forthwith become void, there shall be no
liability on the part of either party, or any of their respective  shareholders,
officers or  directors,  to the other and all rights and  obligations  of either
party shall cease;  provided,  however,  that such termination shall not relieve
either party from  liability for any  misrepresentation  or breach of any of its
warranties, covenants or agreements set forth in this Agreement.


                                      -28-


<PAGE>



         (b) In the event this Agreement is terminated by Diablo pursuant to the
provisions  of Section  7.1(c),  then Diablo  shall be  entitled  to  liquidated
damages of (i) an amount equal to the Escrow Deposit, together with interest and
other  earnings  thereon,  and (ii)  delivery  and  cancellation  of the Interim
Financing  Notes,  including all accrued and unpaid  interest  thereon,  and any
Additional Compensation Certificates;  the parties agree that such amounts shall
collectively  constitute full payment for any and all damages suffered by Diablo
by reason of ATS' failure to consummate the  Transactions.  ATS and Diablo agree
in advance that actual  damages  would be  difficult to ascertain  and that such
liquidated  damages  is a fair and  equitable  amount to  reimburse  Diablo  for
damages  sustained due to ATS' failure to consummate  the  Transactions  for the
above-stated  reasons. In the event this Agreement is terminated by ATS pursuant
to the provisions of Section 7.1(d), then ATS shall be entitled to the amount of
the Escrow Deposit,  together with interest and other earnings thereon,  without
prejudice  to  ATS'  right  to  pursue  damages  or  other  remedies  hereunder.
Notwithstanding the foregoing,  each party shall have the right to seek specific
performance pursuant to the provisions of Section 9.5.

         (c)  In  the  event  this  Agreement  is  terminated  pursuant  to  the
provisions  of Section  7.1(a),  7.1(b),  7.1(e),  7.1(f) or  7.1(g),  except as
provided in Section 7.2(a), neither of the parties shall have any further rights
or remedies,  except that ATS shall be entitled to the Escrow Deposit,  together
with interest and earnings thereon.

         (d)  Anything in this  Article or  elsewhere  in this  Agreement to the
contrary notwithstanding,  in no event shall Diablo be required to refund to ATS
the nonrefundable  deposits made by ATS subsequent to March 31, 1997 pursuant to
the Amendment to Letter of Intent dated March 19, 1997.


                                    ARTICLE 8

                                 INDEMNIFICATION

         8.1 Survival. The representations, warranties, covenants and agreements
of the parties contained in or made pursuant to this Agreement or any Collateral
Document (except as otherwise provided in any Collateral Document) shall survive
the Closing and shall remain operative and in full force and effect for a period
of (a) two (2) years after the  Closing  Date or (b) in the case of matters of a
nature  referred to in Section  3.21,  three (3) years  after the Closing  Date,
regardless of any  investigation  or statement as to the results thereof made by
or on behalf of any party  hereto.  The term  "Indemnity  Period" shall mean the
applicable period with respect to which a representation,  warranty, covenant or
agreement  survives  the  Closing  as  provided  in this  Section.  No claim for
indemnification,  other than with  respect to fraud,  may be asserted  after the
expiration  of the Indemnity  Period.  ATS shall  promptly  advise Diablo in the
event it shall discover any fraud or alleged fraud, it being understood that, in
the event that ATS discovers such fraud or alleged fraud prior to the expiration
of the  Indemnity  Period and fails to so notify  Diablo  thereof,  it shall not
thereafter be entitled to assert any Claim with respect thereto. Notwithstanding
anything  herein to the contrary,  any  representation,  warranty,  covenant and
agreement  which  arises and is the  subject  of a Claim  which is  asserted  in
writing prior to the expiration of the applicable Indemnity Period shall survive
with respect to such Claim or any dispute with respect  thereto  until the final
resolution  thereof or the  expiration of the  applicable  statute of limitation
unless arbitration or litigation has been pursued.

         8.2      Indemnification.

         (a)  During  the  Indemnity  Period,   each  of  Diablo  and  ATS  (the
"indemnifying  party")  agrees that on and after the Closing it shall  indemnify
and hold harmless the other (the  "indemnified  party") from and against any and
all damages,  claims,  losses,  expenses,  costs,  obligations and  liabilities,
including without

                                      -29-


<PAGE>



limitation liabilities for all reasonable attorneys',  accountants' and experts'
fees  and  expenses  including  those  incurred  to  enforce  the  terms of this
Agreement or any Collateral  Document  executed by it  (collectively,  "Loss and
Expense"),  suffered, directly or indirectly, by the indemnified party by reason
of, or arising out of:

                  (i) any  breach  of  representation  or  warranty  made by the
         indemnifying  party  pursuant  to  this  Agreement  or  any  Collateral
         Document  executed  by it or any failure by the  indemnifying  party to
         perform or fulfill any of its  respective  covenants or agreements  set
         forth in this Agreement or any Collateral Document executed by it; or

                  (ii) any  Legal  Action  or other  Claim  by any  third  party
         relating  to the  indemnifying  party  or,  in the  case  of  ATS,  the
         ownership  or  operations  of the Diablo  Assets or the  conduct of the
         business  of the Diablo  Business  to the extent  such Legal  Action or
         other Claim has also resulted in a breach of representation or warranty
         by the indemnifying  party pursuant to this Agreement or any Collateral
         Document executed by it; or

                  (iii) in the case of Diablo  as the  indemnifying  party,  the
         failure  of  Diablo  to  comply  with  Bulk  Sales  law of the State of
         California.

         (b) Diablo  agrees that on or after the Closing it shall  indemnify and
hold  harmless  ATS from and  against  any and all  Loss and  Expense  suffered,
directly  or  indirectly,  by ATS by reason  of, or  arising  out of, (i) Diablo
Nonassumed  Obligations or (ii) the ownership and operation of the Diablo Assets
and the Diablo Business prior to the Closing Date.

         (c) ATS agrees that on or after the Closing it shall indemnify and hold
harmless Diablo from and against any and all Loss and Expense suffered, directly
of indirectly, by Diablo by reason of, or arising out of, (i) (A) Diablo Assumed
Obligations  or (B) the  ownership  and  operation of the Diablo  Assets and the
Diablo Business from and after the Closing Date, except for Events arising prior
to or existing on the Closing Date,  unless they are part of the Diablo  Assumed
Obligations,  and  (ii) any  Hart-Scott-Rodino  Act or  other  federal  or state
antitrust  Law  filings  or any  Legal  Action or other  Claim of any  Authority
relating to the  Transactions  based upon any of the foregoing,  except,  in all
cases,  to the extent such filing,  Legal Action or other Claim relates to or is
based upon information furnished or omitted by Diablo.

         8.3      Limitation of Liability.

         (a)  Notwithstanding  the provisions of Section 8.2, after the Closing,
except as otherwise provided in Section 8.6, each indemnified  party's rights to
indemnification  shall  be  subject  to  the  following  limitations:   (i)  the
indemnified  party  shall be entitled to recover its Loss and Expense in respect
of any Claim  only in the event  that the  aggregate  Loss and  Expense  for all
Claims  (together  with Claims (as defined  therein)  under the Other  Agreement
("Other Agreement Claims")) exceeds, in the aggregate,  $100,000, in which event
the  indemnified  party  shall be  entitled to recover all such Loss and Expense
(including  without  limitation such  $100,000),  and (ii) in no event shall the
aggregate amount required to be paid by each indemnifying  party pursuant to the
provisions of this Article (and the comparable provision of the Other Agreement)
exceed  $1,000,000,  except for any Loss or Expense  arising out of matters of a
nature referred to in Sections 3.1 and 4.1 (and the comparable  provision of the
Other  Agreement)  as to which the dollar  limitations  set forth in this clause
(ii) shall not apply.

         (b)  Anything  in this  Agreement,  including  without  limitation  the
provisions of Sections 8.2 or 8.3(a), to the contrary notwithstanding, except as
provided in Sections 8.3(c) and 8.6, (i) the exclusive recourse of ATS after the
Closing with respect to the  liability of Diablo  pursuant to Section 8.2 or any
other  provision of this Agreement or Applicable  Law which  requires  Diablo to
defend, indemnify or hold harmless

                                      -30-


<PAGE>



ATS from or against  any Claim,  Loss or Expense  shall be the Escrow  Indemnity
Funds; and (ii) ATS' remedies for any such liability of Diablo, or for any Claim
arising under this Agreement,  shall be limited to its right to recover from the
Escrow Indemnity Funds in accordance with the provisions of the Escrow Indemnity
Agreement,  and neither ATS nor any of its  officers,  directors,  shareholders,
agents or Affiliated Entities shall have any right of recovery against Diablo or
any of its officers, directors,  shareholders,  agents or Affiliated Entities or
against the assets of any of them for any such liability.

         (c) In the event  there  shall be no  Claims  pending  pursuant  to the
provisions of this Agreement (and/or Other Agreement Claims) with respect to the
Escrow  Indemnity  Funds,  if any,  existing at the  expiration of two (2) years
after  the  Closing,   the  Escrow  Indemnity  Funds  then  remaining  shall  be
distributed  to  Diablo  and DCI (in  such  proportion  as they  shall  agree in
writing).  In the event one or more such Claims (and/or Other Agreement  Claims)
with  respect  to the  Escrow  Indemnity  Funds,  if any,  shall  exist upon the
expiration of the Indemnity  Period,  funds in an amount equal to the sum of (i)
the aggregate amount of such Claims (and/or Other Agreement Claims) and (ii) the
amount  reasonably  necessary  to  cover  the  fees,  expense  and  other  costs
(including  reasonable  counsel  fees and  expenses)  which will be  required to
resolve such Claims (and/or Other Agreement Claims) shall be retained as part of
the Escrow Indemnity Funds and the balance thereof, if any, shall be distributed
to Diablo and DCI (in such proportion as they shall agree in writing).  Upon the
resolution of all such Claims (and/or Other Agreement Claims) and the payment of
all such  fees,  expenses  and  costs out of the  Escrow  Indemnity  Funds,  the
remainder of the Escrow  Indemnity Funds, if any, shall be distributed to Diablo
and DCI (in such proportion as they shall agree in writing).

         (d) If, following the  distribution to Diablo,  DCI or any other Person
of any remaining Escrow Indemnity Funds, ATS becomes entitled to indemnification
for Loss and Expense  suffered by ATS arising from breach of the  warranties and
misrepresentations  set  forth in  Section  3.21,  or  breach  by  Diablo of any
covenants or agreement by Diablo under this Agreement or any Collateral Document
to which it is a party,  then ATS may pursue such Claim directly against Diablo,
its  successors  and assigns and Spight (but only to the extent he received  any
such  funds);  provided,  however,  that the maximum  amount of liability in the
aggregate of Diablo (and such successors and assigns and Spight) for any and all
such Claims shall be the amount of Escrow  Indemnity Funds that were distributed
to Diablo,  DCI or any other Person (other than a claimant  whose Claim was paid
out of the Indemnity  Escrow Fund) claiming by, through or in the name of Diablo
(including  without  limitation  Spight (but only to the extent he received  any
such funds) or Diablo's or his  successors,  assigns,  trustees,  beneficiaries,
heirs or executors) upon the expiration of the Indemnity Period or thereafter.

         (e) In the case any event shall occur  which  would  otherwise  entitle
either  party  to  assert a claim  for  indemnification  hereunder,  no Loss and
Expense  shall be deemed to have been  sustained  by such party to the extent of
any proceeds  received by such party from any  insurance  policies  with respect
thereto.  No  indemnifying  party shall be liable  under this Article for a loss
resulting from any event relating to a misrepresentation  or breach of warranty,
covenant  or  agreement  if  the  indemnifying  party  can  establish  that  the
indemnified  party had actual  knowledge  on or before the Closing  Date of such
event and did not,  on or before the  Closing  Date,  reserve  its  rights  with
respect thereto.

         8.4 Notice of Claims.  If an  indemnified  party  believes  that it has
suffered or incurred  any Loss and  Expense,  it shall  notify the  indemnifying
party promptly in writing,  and in any event within the  applicable  time period
specified in Section 8.1, describing such Loss and Expense,  all with reasonable
particularity  and containing a reference to the provisions of this Agreement in
respect of which such Loss and Expense shall have occurred.  If any Legal Action
is  instituted  by a third  party  with  respect to which an  indemnified  party
intends  to claim any  liability  or  expense  as Loss and  Expense  under  this
Article,  such indemnified party shall promptly notify the indemnifying party of
such Legal Action, but the failure to so notify the indemnifying

                                      -31-


<PAGE>



party shall not relieve such  indemnifying  party of its obligations  under this
Article,   except  to  the  extent  such  failure  to  notify   prejudices  such
indemnifying party's ability to defend against such Claim.

         8.5 Defense of Third Party Claims.  The  indemnifying  party shall have
the right to  conduct  and  control,  through  counsel  of their  own  choosing,
reasonably  acceptable to the indemnified party, any third party Legal Action or
other Claim, but the indemnified party may, at its election,  participate in the
defense  thereof at its sole cost and expense;  provided,  however,  that if the
indemnifying  party shall fail to defend any such Legal  Action or other  Claim,
then the indemnified party may defend, through counsel of its own choosing, such
Legal Action or other Claim, and (so long as it gives the indemnifying  party at
least fifteen (15) days' written notice of the terms of the proposed  settlement
thereof  and  permits  the  indemnifying  party to then  undertake  the  defense
thereof)  settle  such Legal  Action or other Claim and to recover the amount of
such settlement or of any judgment and the reasonable costs and expenses of such
defense.  The  indemnifying  party shall not compromise or settle any such Legal
Action or other  Claim  without  the prior  written  consent of the  indemnified
party;  provided,  however,  that if the  indemnified  party fails or refuses to
consent in writing to any compromise of settlement  proposed by the indemnifying
party and  agreed to in writing by the  claimant  in such Legal  Action or other
Claim (the "Settlement Proposal") within ten (10) business days after receipt of
written  notice of all of the material  terms and  conditions of the  Settlement
Proposal,  and such  terms and  conditions  (a)  include a full  release  of the
indemnified  party from the Legal  Action or other Claim which is the subject of
the Settlement Proposal, and (b) if the indemnified party is ATS, do not include
any term or condition  which would restrict in any material manner the continued
ownership  or  operations  of the  Diablo  Assets or the  conduct  of the Diablo
Business in substantially the manner then being theretofore owned,  operated and
conducted by ATS, then,  unless the indemnifying  party forthwith  withdraws the
Settlement Proposal,  the indemnified party (i) shall have the right but not the
obligation to undertake the conduct of the defense of such Legal Action or other
Claim,  and (ii) whether or not it shall so undertake  the defense of such Legal
Action or other Claim, shall bear, and shall indemnify and hold the indemnifying
party  harmless  from,  all Loss and Expense  arising  from such Legal Action or
other Claim (to the extent not theretofore (x) accrued with respect to the costs
and expenses of the defense of such Legal Action or other Claim or (y) paid with
respect to such Legal Action or other  Claim) in excess of the amount  contained
in the  Settlement  Proposal,  it  being  understood,  in such  event,  that the
indemnifying  party  shall  bear all Loss and  Expense,  including  subsequently
incurred Loss and Expense  (including  without  limitation those attributable to
legal fees and expenses) up to the amount contained in the Settlement  Proposal,
even if the ultimate  disposition of such Legal Action or other Claim results in
payments  to the  claimant  of  less  than  those  contained  in the  Settlement
Proposal.

         8.6  Exclusive  Remedy.  Except  for fraud or  willful  or  intentional
misrepresentation  or breach of warranty,  covenant or agreement or as otherwise
provided in Section 9.5, the  indemnification  provided in this Article shall be
the sole and exclusive post-Closing remedy available to either party against the
other party for any Claim under this Agreement.


                                    ARTICLE 9

                               GENERAL PROVISIONS


         9.1  Amendment.  This Agreement may be amended from time to time by the
parties  hereto at any time but only by an instrument  in writing  signed by the
parties hereto.

         9.2 Waiver.  Except to the extent not permitted by Applicable  Law, ATS
or Diablo may, at any time,  extend the time for the  performance  of any of the
obligations or other acts of the other, subject,

                                      -32-


<PAGE>



however,  to the  provisions  with respect to the  Termination  Date,  waive any
inaccuracies in the representations and warranties of the other contained herein
or in any document  delivered pursuant hereto, and waive compliance by the other
with any of the agreements,  covenants or conditions  contained herein. Any such
extension or waiver shall be valid only if set forth in an instrument in writing
signed by the party or parties to be bound thereby.

         9.3 Fees, Expenses and Other Payments. All costs and expenses, incurred
in connection with any transfer taxes, recording or documentary taxes, stamps or
other  comparable  charges  levied  by any  Authority  in  connection  with this
Agreement and the consummation of the Transactions, title insurance for Diablo's
fee-owned  Real  Property  shall  be  borne  equally  by  Diablo  and  ATS.  All
Hart-Scott-Rodino  filing fees for both this  Agreement and the Other  Agreement
shall be borne equally by Diablo and ATS up to the amount of $20,000 for each of
Diablo  and ATS,  with the  balance  to be borne by ATS.  All  other  costs  and
expenses  incurred in connection with this Agreement and the consummation of the
Transactions,  including  without  limitation fees and disbursements of counsel,
financial  advisors and  accountants  incurred by the parties  hereto,  shall be
borne  solely  and  entirely  by the party  which has  incurred  such  costs and
expenses.

         9.4  Notices.  All  notices  and  other  communications  which  by  any
provision of this Agreement are required or permitted to be given shall be given
in  writing  and shall be (a)  mailed by  first-class  or  express  mail,  or by
recognized  courier  service,  postage  prepaid,  (b) sent by  telex,  telegram,
telecopy  or other form of rapid  transmission,  confirmed  by mailing (by first
class or express  mail,  or by  recognized  courier  service,  postage  prepaid)
written  confirmation at substantially the same time as such rapid transmission,
or (c)  personally  delivered  to the  receiving  party  (which if other than an
individual  shall be an  officer  or other  responsible  party of the  receiving
party). All such notices and communications  shall be mailed,  sent or delivered
as follows:

         (a)      If to ATS:

                  116 Huntington Avenue
                  Boston, Massachusetts 02116
                  Attention:   Joseph L. Winn, Chief Financial Officer
                  Telecopier No.:  (617) 375-7575

                  with a copy to:

                  Sullivan & Worcester LLP
                  One Post Office Square
                  Boston, Massachusetts 02109
                  Attention:  Norman A. Bikales, Esq.
                  Telecopier No.:  (617) 338-2880


                                      -33-


<PAGE>



         (b)      If to Diablo:

                  1220 Brickyard Cove Road, Suite 200
                  Point Richmond, California 94801
                  Attention: Richard D. Spight, Chairman
                  Telecopier No.: (510) 236-3799

                  with a copy to:

                  Cooper, White & Cooper
                  1333 North California Boulevard, Suite 450
                  Walnut Creek, California 94596
                  Attention: Keith Howard, Esq.
                  Telecopier No.: (510) 256-9428

or to such other person(s),  telex or facsimile  number(s) or address(es) as the
party to receive any such communication or notice may have designated by written
notice to the other party.

         9.5 Specific Performance;  Other Rights and Remedies.  Anything in this
Agreement to the contrary notwithstanding, each party recognizes and agrees that
in the event the other party  should  refuse to perform  any of its  obligations
under this  Agreement  or any  Collateral  Document,  the remedy at law would be
inadequate  and  agrees  that for breach of such  provisions,  each party not in
material breach of this Agreement or any Collateral  Document shall, in addition
to such  other  remedies  as may be  available  to it at law or in  equity or as
provided  in Article 7, be  entitled  to  injunctive  relief and to enforce  its
rights  by an  action  for  specific  performance  to the  extent  permitted  by
Applicable  Law.  Each party hereby waives any  requirement  for security or the
posting  of any  bond or other  surety  in  connection  with  any  temporary  or
permanent  award of injunctive,  mandatory or other  equitable  relief.  Nothing
herein  contained shall be construed as prohibiting each party from pursuing any
other remedies available to it pursuant to the provisions of, and subject to the
limitations  contained in, this Agreement for such breach or threatened  breach.
Notwithstanding  the  foregoing  or  any  provision  of  this  Agreement  to the
contrary,  after  the  Closing  Date  ATS  shall  not be  entitled  to  specific
performance  or any other  remedy to the extent that the cost to Diablo  arising
from the  enforcement or exercise of such remedy would exceed the amount then on
deposit in the Escrow  Indemnity Funds, in accordance with the provisions of the
Escrow Indemnity  Agreement,  for all costs and expenses  incurred in connection
with its performance of or compliance with the remedy exercised or enforced.

         9.6  Severability.  If any term or provision of this Agreement shall be
held or deemed  to be, or shall in fact be,  invalid,  inoperative,  illegal  or
unenforceable  as  applied  to  any  particular  case  in  any  jurisdiction  or
jurisdictions,  or in  all  jurisdictions  or  in  all  cases,  because  of  the
conflicting of any provision with any  constitution or statute or rule of public
policy or for any other reason,  such circumstance  shall not have the effect of
rendering the provision or provisions in question invalid, inoperative,  illegal
or unenforceable in any other  jurisdiction or in any other case or circumstance
or of rendering any other  provision or  provisions  herein  contained  invalid,
inoperative,  illegal or  unenforceable to the extent that such other provisions
are not themselves actually in conflict with such constitution,  statute or rule
of public policy, but this Agreement shall be reformed and construed in any such
jurisdiction or case as if such invalid,  inoperative,  illegal or unenforceable
provision had never been contained herein and such provision reformed so that it
would be valid,  operative and  enforceable to the maximum  extent  permitted in
such jurisdiction or in such case.  Notwithstanding the foregoing,  in the event
of any such  determination  the  effect  of which is to  affect  materially  and
adversely either party, the parties shall negotiate in good faith to modify this
Agreement  so as to effect  the  original  intent of the  parties  as closely as
possible to the fullest extent permitted

                                      -34-


<PAGE>



by Applicable Law in an acceptable  manner to the end that the  Transactions are
fulfilled and consummated to the maximum extent possible.

         9.7   Counterparts.   This   Agreement   may  be  executed  in  several
counterparts,  each of  which  shall be  deemed  an  original,  but all of which
together shall constitute one and the same  instrument,  binding upon all of the
parties. In pleading or proving any provision of this Agreement, it shall not be
necessary to produce more than one of such counterparts.

         9.8 Section Headings.  The headings contained in this Agreement are for
reference  purposes  only  and  shall  not in any  way  affect  the  meaning  or
interpretation of this Agreement.

         9.9 Governing Law; Venue.  The validity,  interpretation,  construction
and  performance  of this  Agreement  shall be  governed  by, and  construed  in
accordance  with,  the  applicable  laws of the United States of America and the
laws of the State of California  applicable  to contracts  made and performed in
such State and, in any event, without giving effect to any choice or conflict of
laws provision or rule that would cause the application of domestic  substantive
laws of any other  jurisdiction.  Anything  in this  Agreement  to the  contrary
notwithstanding,  including  without  limitation the provisions of Article 8, in
the event of any dispute  between the parties  which  results in a Legal Action,
the prevailing party shall be entitled to receive from the non-prevailing  party
reimbursement for reasonable legal fees and expenses incurred by such prevailing
party in such Legal Action. In the event of any Legal Action between the parties
arising out of this  Agreement,  the  parties  agree to submit the matter to the
appropriate  municipal,  state or federal court sitting in San Francisco County,
California, and the parties agree to submit to the jurisdiction of such courts.

         9.10 Further Acts. Each party agrees that at any time, and from time to
time, before and after the consummation of the transactions contemplated by this
Agreement,  it  will do all  such  things  and  execute  and  deliver  all  such
Collateral  Documents  and other  assurances,  as any other party or its counsel
reasonably  deems  necessary  or  desirable  in order to carry out the terms and
conditions of this  Agreement  and the  transactions  contemplated  hereby or to
facilitate  the enjoyment of any of the rights  created  hereby or to be created
hereunder.

         9.11  Entire  Agreement.  This  Agreement  (together  with  the  Diablo
Disclosure  Schedule and the other Collateral  Documents delivered in connection
herewith),  constitutes  the entire  agreement of the parties and supersedes all
prior agreements and undertakings,  both written and oral,  between the parties,
with respect to the subject matter hereof,  including  without  limitation  that
certain  letter of intent,  dated  December  19, 1996,  between the parties,  as
amended by the letter dated March 19, 1997 (the "Letter of Intent").

         9.12 Assignment. This Agreement shall not be assignable by either party
and any such  assignment  shall be null and void,  except that it shall inure to
the benefit of and by binding  upon any  successor  to any party by operation of
law,  including by way of merger,  consolidation or sale of all or substantially
all of its assets,  and ATS may assign its rights and remedies  hereunder to any
bank or other financial institution which has loaned funds or otherwise extended
credit to it.

         9.13  Parties in  Interest.  This  Agreement  shall be binding upon and
inure  solely to the  benefit of each  party,  and  nothing  in this  Agreement,
express or implied,  including without limitation Section 2.2(c), is intended to
or shall  confer  upon any  Person  any  right,  benefit or remedy of any nature
whatsoever under or by reason of this Agreement, except as otherwise provided in
Section 9.12.

         9.14 Mutual Drafting. This Agreement is the result of the joint efforts
of Diablo and ATS,  and each  provision  hereof  has been  subject to the mutual
consultation, negotiation and agreement of the parties

                                      -35-


<PAGE>



and there shall be no construction against either party based on any presumption
of that party's involvement in the drafting thereof.

         9.15  Arbitration.  If there is any dispute between the parties to this
Agreement  which remains  unresolved for thirty (30) days or more,  either party
may,  upon  written  notice  to  the  other,  submit  such  dispute  to  binding
arbitration in San Francisco, California in accordance with the commercial rules
of the American Arbitration  Association (the "AAA") before a panel of three (3)
arbitrators  knowledgeable in the tower communications  industry, one arbitrator
chosen by ATS, one by Diablo,  and the third as mutually  agreed upon by the two
arbitrators so appointed or, in the absence of such agreement,  by the President
of the San  Francisco  Chapter of the AAA, and the decision of such panel shall,
in the absence of fraud, be conclusively binding on the parties.

         9.16  Disclosure  Schedule.  Diablo  has  delivered  to  ATS  prior  to
execution and delivery of this Agreement the Diablo Disclosure  Schedule and all
related  documents  required to be delivered by Diablo  pursuant to Article 3 of
this  Agreement.  Without  limiting the generality of the foregoing,  the Diablo
Disclosure  Schedule sets forth: (i) which  authorizations,  consents,  waivers,
orders or approvals  are a condition of Closing  pursuant to the  provisions  of
Section  6.1(a);  (ii)  which  Private   Authorizations,   Leases  and  Material
Agreements and other Contractual Obligations are a condition to Closing pursuant
to the provisions of Section 6.2(d); and (iii) which permits,  consents or other
Governmental  Authorizations of the United States Forest Service are a condition
to Closing  pursuant to the provisions of Section  6.2(m).  ATS has received and
hereby  accepts the Diablo  Disclosure  Schedule  and agrees to  consummate  the
transactions contemplated by this Agreement,  subject to the satisfaction of the
conditions  set  forth  in  Sections  6.1  and 6.2 and  subject  to the  matters
disclosed in the Diablo Disclosure Schedule.



                                      -36-


<PAGE>



         IN WITNESS  WHEREOF,  ATS and Diablo have caused this  Agreement  to be
executed  as of the  date  first  written  above by  their  respective  officers
thereunto duly authorized.

                              American Tower Systems, Inc.


                              By:_____________________________________
                                   Name: James S. Eisenstein
                                   Title:   Chief Operating Officer

                              Diablo Communications of Southern California, Inc.


                              By:______________________________________
                                   Name:
                                   Title:

         The  undersigned,  Richard D.  Spight,  the  principal  shareholder  of
Diablo,  hereby acknowledges and agrees to be bound by the provisions of Article
8, including without limitation Section 8.3(d).


                                              ----------------------------------
                                                       Richard D. Spight














                                      -37-


<PAGE>



                                                                      APPENDIX A

                                   DEFINITIONS

         As used in this Agreement,  unless the context otherwise requires,  the
following  terms  (or any  variant  in the  form  thereof)  have  the  following
respective  meanings.  Terms  defined in the  singular  shall have a  comparable
meaning when used in the plural, and vice versa, and the reference to any gender
shall be deemed to include all genders.  Unless otherwise defined or the context
otherwise clearly  requires,  terms for which meanings are provided herein shall
have  such  meanings  when  used in the  Diablo  Disclosure  Schedule,  and each
Collateral  Document  executed or required  to be  executed  pursuant  hereto or
thereto or otherwise  delivered,  from time to time, pursuant hereto or thereto.
References  to "hereof",  "herein" or similar terms are intended to refer to the
Agreement  as a whole and not a  particular  Section,  and  references  to "this
Section"  are  intended  to refer to the  entire  Section  and not a  particular
subsection thereof.  The term "either party" shall, unless the context otherwise
requires, refer to Diablo and ATS.

         Acceptance Notice shall have the meaning given to it in Section 2.2(c).

         Accounts Receivable shall mean (a) any and all rights to the payment of
money or other forms of  consideration  of any kind at any time now or hereafter
owing or to be owing to Diablo attributable to the ownership or operation of the
Diablo Business  (whether  classified  under the Uniform  Commercial Code of any
state as accounts,  contract  rights,  chattel  paper,  general  intangibles  or
otherwise),  including without limitation accounts receivable, letters of credit
and the right to receive payment thereunder,  chattel paper, insurance proceeds,
contract rights, notes, drafts,  instruments,  documents,  acceptances,  and all
other debts, obligations and liabilities in whatever form now or hereafter owing
from any other Person, all guarantees, security and Liens for the payment of any
thereof,  and all of Diablo's rights to goods, now owned or hereafter  acquired,
sold (delivered,  undelivered,  in transit or returned) which may be represented
thereby; and (b) all proceeds of any of the foregoing.

         adverse,  adversely, when used alone or in conjunction with other terms
(including  without  limitation  "affect," "change" and "effect") shall mean any
Event which is reasonably likely, in the reasonable business judgment of ATS, to
be expected to (a)  adversely  affect the  validity  or  enforceability  of this
Agreement  or  the  likelihood  of  consummation  of  the  Transactions,  or (b)
adversely affect the business, operations,  management, properties or prospects,
or the  condition,  financial  or other,  or results of  operation of the Diablo
Business,  or (c) impair Diablo's  ability to fulfill its obligations  under the
terms of this  Agreement,  or (d)  adversely  affect  the  aggregate  rights and
remedies  of ATS  under  this  Agreement.  Notwithstanding  the  foregoing,  and
anything  in this  Agreement  to the  contrary  notwithstanding,  any  Event (i)
generally affecting the economy or the tower communications  business or (ii) of
a nature described in the "Definition" section of the Diablo Disclosure Schedule
shall not be deemed to constitute an adverse  change,  have an adverse effect or
to adversely affect or effect.

         Additional  Title Matter shall have the meaning  given to it in Section
5.7.

         Affiliate,  Affiliated shall mean, with respect to any Person,  (a) any
other Person at the time  directly or indirectly  controlling,  controlled by or
under direct or indirect  common control with such Person,  (b) any other Person
of which such Person at the time owns, or has the right to acquire,  directly or
indirectly,  twenty  percent  (20%) or more of any class of the capital stock or
beneficial  interest,  (c) any other Person  which at the time owns,  or has the
right to acquire,  directly or  indirectly,  twenty percent (20%) or more of any
class of the  capital  stock or  beneficial  interest  of such  Person,  (d) any
executive  officer  or  director  of  such  Person,  (e)  with  respect  to  any
partnership,  joint venture or similar Entity, any general partner thereof,  and
(f) when

                                       A-1


<PAGE>



used  with  respect  to  an  individual,   shall  include  any  member  of  such
individual's immediate family or a family trust.

         Agreement shall mean this Agreement as originally in effect, including,
unless the context otherwise specifically requires,  this Appendix A, the Diablo
Disclosure  Schedule  and all exhibits  hereto,  and as any of the same may from
time to time be supplemented, amended, modified or restated in the manner herein
or therein provided.

         Applicable Law shall mean any Law of any Authority, whether domestic or
foreign,  including  without  limitation  the  FCA  and all  federal  and  state
securities and  Environmental  Laws, to which a Person is subject or by which it
or any of its business or operations is subject or any of its property or assets
is bound.

         Approved Title  Conditions shall mean any one or more of the following:
(a) Liens for real property taxes and assessments not then  delinquent;  (b) the
Lien of  supplemental  Taxes assessed  pursuant to Chapter 3.5  commencing  with
Section 75 of the California  Revenue and Taxation Code, to the extent that such
supplemental  Taxes are  attributable to the  transactions  contemplated by this
Agreement; (c) matters of title approved by ATS or deemed approved in accordance
with the  provisions of Section 5.7; and (d) matters of title created  following
the date of this Agreement by or with the written consent of ATS.

         Assets shall mean the business and the tangible and  intangible  assets
used in connection  with the conduct of the business or operations of the Diablo
Business,  which  business  and  assets  are  being  exchanged,  transferred  or
otherwise conveyed hereunder, including without including without limitation the
following:


                  (a) the Personal Property;

                  (b) the Real Property;

                  (c) the Governmental Authorizations;

                  (d) the Private Authorizations;

                  (e)  the   Contracts   (other   than  the  Diablo   Nonassumed
         Obligations);

                  (f) the corporate name of Diablo and all variations thereof;

                  (g)  all   Intellectual   Property   and   other   proprietary
         information,  which relate to the Diablo  Business,  including  without
         limitation,  technical  information  and data,  machinery and equipment
         warranties, maps, computer discs and tapes, plans, diagrams, blueprints
         and schematics,  including filings with all Authorities which relate to
         the Diablo Business;

                  (h) all claims,  choses in action and rights under  warranties
         relating to the Diablo Business or any of the Diablo Assets;

                  (i)  all  books  and  records  relating  to the  ownership  or
         operation of the Diablo  Assets or the conduct of the Diablo  Business,
         including  executed  copies of Leases,  Material  Agreements  and other
         written  Contracts,  and all records  required by Applicable  Law to be
         kept,  subject to the right of the  conveying  party to have such books
         and records  made  available  to it for such time as may be  reasonably
         required in connection with audits, defense or prosecution of lawsuits,
         or other legitimate  business  purposes.  The records  described herein
         shall not include corporate seals, certificates of

                                       A-2


<PAGE>



         incorporation,  minute books, stock books, tax returns or other records
         having to do with the corporate organization of Diablo; and

                  (j)  any  and all  products,  profits  and  proceeds  of,  and
         including  without  limitation  any Claims with  respect to, any of the
         foregoing;

provided, however, that notwithstanding the foregoing, the term Assets shall not
include any of the Excluded Assets.

         ATS shall have the meaning given to it in the Preamble.

         ATS Accrued Sick Time  Liability  shall have the meaning given to it in
Section 2.2(c).

         ATS Assumed  Vacation  Liability  shall have the meaning given to it in
Section 2.2(c).

         ATS' Environmental Notice shall have the meaning given to it in Section
5.8.

         ATS' Title Notice shall have the meaning given to it in Section 5.7.

         Authority shall mean any governmental or quasi-governmental  authority,
whether  administrative,  executive,  judicial,  legislative  or  other,  or any
combination   thereof,   including  without   limitation  any  federal,   state,
territorial,   county,   municipal  or  other   government  or  governmental  or
quasi-governmental agency, arbitrator,  authority,  board, body, branch, bureau,
central bank or comparable  agency or Entity,  commission,  corporation,  court,
department,  instrumentality,  master, mediator, panel, referee, system or other
political unit or  subdivision or other Entity of any of the foregoing,  whether
domestic or foreign., including without limitation the FCC.

         Benefit Arrangement shall mean any material benefit arrangement that is
not a Plan,  including  (a)  any  employment  or  consulting  agreement  (b) any
arrangement providing for insurance coverage or workers' compensation  benefits,
(c) any  incentive  bonus or deferred  bonus  arrangement,  (d) any  arrangement
providing termination  allowance,  severance or similar benefits, (e) any equity
compensation plan, (f) any deferred  compensation plan, and (g) any compensation
policy and  practice,  but only to the  extent  that it covers or relates to any
officer, employee or other Person involved in the ownership and operation of the
Assets or the conduct of the business of the Diablo Business.

         CAAP shall mean the  accounting  principles  used by the Company in the
preparation  of the Financial  Statements  and described in general terms in the
Disclosure  Schedule,  such principles applied on a consistent basis,  except as
otherwise heretofore disclosed in the Disclosure Schedule.  The requirement that
such principles be consistently applied means that the accounting  principles in
a current  period are  comparable  in all material  respect to those  applied in
preceding period.  All accounting and financial terms used in this Agreement and
the  compliance  with each covenant  contained in this Agreement that relates to
financial  matters  shall  be  determined  in  accordance  with  the  accounting
principles referred to in this paragraph (except as otherwise specifically noted
in certain of the definitions where the term GAAP is used).

         Claims shall mean any and all debts, liabilities,  obligations, losses,
damages,  deficiencies,  assessments  and  penalties,  together  with all  Legal
Actions, pending or threatened, claims and judgments of whatever kind and nature
relating  thereto,  and all fees, costs,  expenses and disbursements  (including
without  limitation  reasonable  attorneys'  and  other  legal  fees,  costs and
expenses) relating to any of the foregoing.

         Closing shall have the meaning given to it in Section 2.3.

                                       A-3


<PAGE>



         Closing Date shall have the meaning given to it in Section 2.3.

         COBRA shall mean the Consolidated Omnibus Budget  Reconciliation Act of
1985,  as  amended,  as set  forth  in  Section  4980B of the Code and Part 6 of
Subtitle B of Title I of ERISA.

         Code shall mean the Internal  Revenue  Code of 1986,  and the rules and
regulations  thereunder,  all as from time to time in effect,  or any  successor
law,  rules or  regulations,  and any  reference to any  statutory or regulatory
provision  shall be deemed  to be a  reference  to any  successor  statutory  or
regulatory provision.

         Collateral  Document  shall mean the Escrow  Agreement,  the  Indemnity
Escrow Agreement, the Nonassignable Contracts Agreement, special warranty deeds,
bills of sale, assignments of intangibles, assumption agreements with respect to
the Diablo Assumed  Obligations,  other instruments of conveyance and assignment
sufficient to vest in ATS title to all of the other Diablo Assets and the Diablo
Business, and any other agreement,  certificate,  contract,  instrument, notice,
opinion or other document delivered pursuant to the provisions of this Agreement
or any Collateral Document.

         Collection Period shall have the meaning given to it in Section 2.4.

         Construction  Adjustment  shall have the meaning given to it in Section
2.3.

         Contract, Contractual Obligation shall mean any agreement, arrangement,
commitment,  contract, covenant,  indemnity,  undertaking or other obligation or
liability  which involves the ownership or operation of the Diablo Assets or the
conduct of the Diablo Business.

         Control (including the terms  "controlled,"  "controlled by" and "under
common control with") means the possession, directly or indirectly or as trustee
or executor,  of the power to direct or cause the direction of the management or
policies of a Person,  or the disposition of such Person's assets or properties,
whether through the ownership of stock, equity or other ownership,  by contract,
arrangement or understanding,  or as trustee or executor,  by contract or credit
arrangement or otherwise.

         DCI shall have the meaning given to it in the fourth Whereas paragraph.

         Diablo shall have the meaning given to it in the Preamble.

         Diablo Assumable  Agreements shall mean all obligations and liabilities
of Diablo under all Leases,  Material Agreements,  Governmental  Authorizations,
Private  Authorizations  and other  Contractual  Obligations  not required to be
listed on Section  3.16 of the Diablo  Disclosure  Schedule  entered into in the
ordinary course of business and relating to the ownership or operation of any of
the Diablo Assets or the
conduct of the Diablo Business.

         Diablo Assets shall have the meaning given to it in Section 2.1.

         Diablo  Assumed  Liabilities  shall  have  the  meaning  given to it in
Section 2.2(b).

         Diablo  Business shall have the meaning given them in the first Whereas
paragraph.

         Diablo Disclosure  Schedule shall mean the Diablo  Disclosure  Schedule
dated as of the date of this Agreement delivered by Diablo to ATS.

         Diablo  Employees  shall  have  the  meaning  given  it in the  Section
3.15(a).

                                       A-4


<PAGE>



         Diablo  Financial  Statements  shall  have the  meaning  given to it in
Section 3.2(b).

         Diablo  Nonassumed  Obligations  shall have the meaning  given to it in
Section 2.2(b).

         Diablo Personal  Property shall have the meaning given to it in Section
3.5(c).

         Diablo's  Environmental  Notice  shall have the meaning  given to it in
Section 5.8.

         Diablo's  knowledge means the actual knowledge of any Diablo officer or
senior  manager,  as such knowledge  exists on the date of this Agreement and no
later date, after reasonable review of appropriate Diablo records.

         Diablo's  Title  Notice  shall have the meaning  given to it in Section
5.7.

         Employment   Arrangement  shall  mean,  with  respect  to  Diablo,  any
employment,  consulting,  retainer,  severance or similar  contract,  agreement,
plan,  arrangement or policy (exclusive of any which is terminable within thirty
(30) days  without  liability,  penalty  or payment of any kind by Diablo or any
Affiliate), or providing for severance, termination payments, insurance coverage
(including any  self-insured  arrangements),  workers  compensation,  disability
benefits,   life,  health,   medical,   dental  or   hospitalization   benefits,
supplemental unemployment benefits,  vacation or sick leave benefits, pension or
retirement benefits or for deferred compensation, profit-sharing, bonuses, stock
options,  stock  purchase or  appreciation  rights or other  forms of  incentive
compensation  or  post-retirement  insurance,  compensation  or  post-retirement
insurance, compensation or benefits, or any collective bargaining or other labor
agreement,  whether or not any of the foregoing is subject to the  provisions of
ERISA, but only to the extent that it covers or relates to any officer, employee
or other Person  involved in the  ownership or operation of the Diablo Assets or
the conduct of the Diablo Business.

         Encumber  shall  mean  to  suffer,  accept,  agree  to  or  permit  the
imposition of a Lien.

         Entity shall mean any corporation,  firm, unincorporated  organization,
association,  partnership,  limited  liability  company,  trust  (inter vivos or
testamentary),  estate of a deceased, insane or incompetent individual, business
trust,  joint stock  company,  joint  venture or other  organization,  entity or
business,  whether acting in an individual,  fiduciary or other capacity, or any
Authority.

         Environmental  Company  shall have the  meaning  given to it in Section
5.8.

         Environmental Law shall mean any Law relating to or otherwise  imposing
liability or  standards of conduct  concerning  pollution or  protection  of the
environment,   including   without   limitation   Laws  relating  to  emissions,
discharges,  releases or  threatened  releases of  Hazardous  Materials or other
chemicals or  industrial  pollutants,  substances,  materials or wastes into the
environment (including,  without limitation,  ambient air, surface water, ground
water,  mining or reclamation or mined land, land surface or subsurface  strata)
or otherwise relating to the manufacture,  processing, generation, distribution,
use, treatment, storage, disposal, cleanup, transport or handling of pollutants,
contaminants,  chemicals or industrial, toxic or hazardous substances, materials
or wastes. Environmental Laws shall include without limitation the Comprehensive
Environmental  Response,  Compensation and Liability Act (42 U.S.C. Section 6901
et seq.), the Hazardous Material  Transportation Act (49 U.S.C.  Section 1801 et
seq.),  the Resource  Conservation  and Recovery Act (42 U.S.C.  Section 6901 et
seq.), the Federal Water Pollution Control Act (33 U.S.C. Section 1251 et seq.),
the Clean Air Act (42 U.S.C. Section 7401 et seq.), the Toxic Substances Control
Act (15 U.S.C. Section 2601 et seq.), the Occupational Safety and Health Act (29
U.S.C.  Section 651 et seq.), the Federal Insecticide  Fungicide and Rodenticide
Act (7 U.S.C. Section 136 et seq.), and the Surface Mining

                                       A-5


<PAGE>



Control and  Reclamation Act of 1977 (30 U.S.C.  Section 1201 et seq.),  and any
analogous federal,  state, local or foreign, Laws, and the rules and regulations
promulgated  thereunder all as from time to time in effect, and any reference to
any statutory or regulatory  provision  shall be deemed to be a reference to any
successor statutory or regulatory provision.

         Environmental Permit shall mean any Governmental Authorization required
by or pursuant to any Environmental Law.

         Environmental  Reports  shall have the  meaning  given to it in Section
5.8.

         ERISA shall mean the Employee  Retirement  Income Security Act of 1974,
and the rules and regulations thereunder, all as from time to time in effect, or
any successor law, rules or  regulations,  and any reference to any statutory or
regulatory  provision  shall  be  deemed  to be a  reference  to  any  successor
statutory or regulatory provision.

         ERISA  Affiliate  shall  mean any  Person  that is  treated as a single
employer  with Diablo  under  Sections  414(b),  (c),  (m) or (o) of the Code or
Section 4001(b)(1) of ERISA.

         Escrow  Agent shall have the meaning  given to it in the third  Whereas
paragraph.

         Escrow  Agreement  shall  have the  meaning  given  to it in the  third
Whereas paragraph.

         Escrow  Deposit shall have the meaning given to it in the third Whereas
paragraph.

         Event  shall  mean the  existence  or  occurrence  of any act,  action,
activity,  circumstance,  condition,  event,  fact,  failure  to act,  omission,
incident or practice, or any set or combination of any of the foregoing.

         Exchange Act shall mean the  Securities  Exchange Act of 1934,  and the
rules and  regulations  thereunder,  all as from time to time in effect,  or any
successor  law,  rules or  regulations,  and any  reference to any  statutory or
regulatory  provision  shall  be  deemed  to be a  reference  to  any  successor
statutory or regulatory provision.

         Excluded Assets shall have the meaning given to it in Section 2.1.

         Exclusivity  Agreement  shall have the  meaning  given to it in Section
6.2(r).

         FCA  shall  mean the  Communication  Act of  1934,  and the  rules  and
regulations  thereunder,  all as from time to time in effect,  or any  successor
law,  rules or  regulations,  and any  reference to any  statutory or regulatory
provision  shall be deemed  to be a  reference  to any  successor  statutory  or
regulatory provision.

         FCC shall mean the Federal Communications  Commission and shall include
any successor Authority.

         Final  Order  shall  mean,  with  respect to any  Authority,  including
without  limitation  the FCC, one with respect to which no appeal,  no stay,  no
petition or application for rehearing, reconsideration,  review or stay, whether
on motion of the applicable Authority or other Person or otherwise, and no other
Legal Action contesting such consent or approval, is in effect or pending and as
to  which  the  time or  deadline  for  filing  any  such  appeal,  petition  or
application  or other Legal  Action has expired or, if filed,  has been  denied,
dismissed or  withdrawn,  and the time or deadline for  instituting  any further
Legal Action has expired.


                                       A-6


<PAGE>



         GAAP shall mean means,  except to the extent that a deviation therefrom
is expressly required by this Agreement, such principles applied on a consistent
basis,  (i) as set forth in Opinions of the Accounting  Principles  Board of the
American  Institute  of  Certified  Public   Accountants   ("AICPA")  and/or  in
statements of the Financial  Accounting  Standards  Board that are applicable in
the  circumstances as of the date in question,  (ii) when not inconsistent  with
such  opinions  and  statements,  as set forth in other AICPA  publications  and
guidelines  and/or  (iii)  that  otherwise  arise by custom  for the  particular
industry, all as the same shall exist on the date of this Agreement.

         Governmental  Authorizations  shall  mean all  approvals,  concessions,
consents,   franchises,   licenses,  permits,  plans,  registrations  and  other
authorizations  of all  Authorities,  including  without  limitation  the United
States Forest  Service and the Federal  Aviation  Administration,  in connection
with the  ownership  or  operation  of the Diablo  Assets or the  conduct of the
Diablo Business.

         Governmental  Filings shall mean all filings,  including  franchise and
similar Tax  filings,  and the payment of all fees,  assessments,  interest  and
penalties associated with such filings, with all Authorities.

         Hart-Scott-Rodino Act shall mean the Hart-Scott-Rodino  Improvement Act
of 1976, as from time to time in effect, or any successor law, and any reference
to any  statutory  provision  shall be deemed to be a reference to any successor
statutory provision.

         Hazardous  Materials  shall mean and include any  substance,  material,
waste, constituent, compound, chemical, natural or man-made element or force (in
whatever state of matter):  (a) the presence of which requires  investigation or
remediation under any Environmental  Law, or (b) that is defined as a "hazardous
waste" or  "hazardous  substance"  under any  Environmental  Law; or (c) that is
toxic, explosive,  corrosive,  etiologic,  flammable,  infectious,  radioactive,
carcinogenic,   mutagenic  or  otherwise  hazardous  and  is  regulated  by  any
applicable Authority or subject to any Environmental Law; or (d) the presence of
which on the real property owned or leased by such Person causes or threatens to
cause a nuisance upon any such real property or to adjacent  properties or poses
or threatens to pose a hazard to the health or safety of persons on or about any
such real property;  or (e) the presence of which on adjacent  properties  could
constitute a trespass by such Person; or (f) that contains gasoline, diesel fuel
or other  petroleum  hydrocarbons,  or any  by-products  or  fractions  thereof,
natural gas,  polychlorinated  biphenyls ("PCBs") and PCB-containing  equipment,
radon or other radioactive elements,  ionizing radiation,  electromagnetic field
radiation  and other  non-ionizing  radiation,  sonic  forces and other  natural
forces,  lead,  asbestos  or  asbestos-containing  materials  ("ACM"),  or  urea
formaldehyde foam insulation.

         Indebtedness  shall mean,  with  respect to any Person,  (a) all items,
except  items of  capital  stock or of  surplus  or of  general  contingency  or
deferred tax reserves or any minority  interest in any Subsidiary of such Person
to the extent such interest is treated as a liability with indeterminate term on
the  consolidated  balance sheet of such Person,  which in accordance  with GAAP
would be included in  determining  total  liabilities  as shown on the liability
side of a balance sheet of such Person, (b) all obligations  secured by any Lien
to which any property or asset owned or held by such Person is subject,  whether
or not the obligation  secured  thereby shall have been assumed,  and (c) to the
extent not  otherwise  included,  all  Contractual  Obligations  of such  Person
constituting  capitalized leases and all obligations of such Person with respect
to Leases constituting part of a sale and leaseback arrangement.

         Indebtedness  for Money  Borrowed  shall mean,  with respect to Diablo,
money borrowed and Indebtedness represented by notes payable and drafts accepted
representing   extensions  of  credit,  all  obligations   evidenced  by  bonds,
debentures,  notes or other similar instruments, the maximum amount currently or
at any time thereafter  available to be drawn under all  outstanding  letters of
credit  issued  for the  account of such  Person,  all  Indebtedness  upon which
interest charges are customarily paid by such Person,

                                       A-7


<PAGE>



and all Indebtedness (including capitalized lease obligations) issued or assumed
as full or partial  payment for  property or  services,  whether or not any such
notes,  drafts,  obligations or Indebtedness  represent  Indebtedness  for money
borrowed,  but shall not include (a) trade payables, (b) expenses accrued in the
ordinary course of business, (c) customer advance payments and customer deposits
received in the ordinary course of business, or (d) conditional sales agreements
not prohibited by the terms of this Agreement.

         Indemnity  Escrow  Agent shall have the meaning  given to it in Section
6.2(k).

         Indemnity  Escrow  Agreement  shall  have  the  meaning  given to it in
Section 6.2(k).

         Indemnity  Escrow  Fund shall have the  meaning  given to it in Section
2.3.

         Insured  Real  Property  shall have the meaning  given to it in Section
5.7.

         Intangible  Assets shall mean all assets and property  lacking physical
properties the evidence of ownership of which must  customarily be maintained by
independent  registration,  documentation,  certification,  recordation or other
means,  and  shall  include,   without  limitation,   concessions,   copyrights,
franchises,  license, patents, permits, service marks, trademarks,  trade names,
and applications with respect to any of the foregoing, technology and know-how.

         Intellectual  Property  shall mean any and all  research,  information,
inventions,  designs,  procedures,  developments,   discoveries,   improvements,
patents and applications therefor, trademarks and applications therefor, service
marks, trade names, copyrights and applications therefor,  logos, trade secrets,
drawing, plans, systems,  methods,  specifications,  computer software programs,
tapes, discs and related data processing  software (including without limitation
object and source  codes)  owned by such Person or in which it has an  ownership
interest  and all other  manufacturing,  engineering,  technical,  research  and
development data and know-how made, conceived, developed and/or acquired by such
Person,  which  relate  to the  manufacture,  production  or  processing  of any
products  developed  or sold by such  Person or which are within the scope of or
usable in connection  with such Person's  business as it may, from time to time,
hereafter be conducted or proposed to be conducted.

         Interim Adjustment shall have the meaning given to it in Section 2.3.

         Interim  Financing Note shall have the meaning given to it in the fifth
Whereas paragraph.

         Law shall mean any (a) administrative,  judicial,  legislative or other
action,  code,  consent  decree,  constitution,  decree,  directive,  enactment,
finding, guideline, law, injunction, interpretation, judgment, order, ordinance,
policy statement,  proclamation,  promulgation,  regulation,  requirement, rule,
rule of law, rule of public policy,  settlement  agreement,  statute, or writ of
any  Authority,  domestic  or  foreign;  (b) the common  law,  or other legal or
quasi-legal  precedent;  or (c)  arbitrator's,  mediator's  or referee's  award,
decision,  finding or recommendation;  including, in each such case or instance,
any interpretation,  directive,  guideline or request, whether or not having the
force of law including, in all cases, without limitation any particular section,
part or provision thereof.

         Lease  shall mean any lease of  property,  whether  real,  personal  or
mixed, and all amendments thereto.

         Legal  Action  shall  mean,  with  respect to any  Person,  any and all
litigation   or   legal   or   other   actions,   arbitrations,   counterclaims,
investigations, proceedings, requests for material information by or pursuant to
the  order of any  Authority  or  suits,  at law or in  arbitration,  equity  or
admiralty, whether or not purported to

                                       A-8


<PAGE>



be  brought  on  behalf of such  Person,  affecting  such  Person or any of such
Person's business, property or assets.

         Letter of Intent shall have the meaning given to it in Section 9.11.

         Lien shall mean any of the  following:  mortgage;  lien  (statutory  or
other);  or other security  agreement,  arrangement or interest;  hypothecation,
pledge  or  other  deposit  arrangement;  assignment;  charge;  levy;  executory
seizure;   attachment;   garnishment;   encumbrance   (including  any  easement,
exception,  reservation or limitation,  right of way, and the like); conditional
sale,  title  retention  or other  similar  agreement,  arrangement,  device  or
restriction;   preemptive  or  similar  right;  any  financing  lease  involving
substantially  the same economic  effect as any of the foregoing;  the filing of
any financing  statement under the Uniform  Commercial Code or comparable law of
any  jurisdiction;  restriction on sale,  transfer,  assignment,  disposition or
other alienation; or any option, equity, claim or right of or obligation to, any
other Person, of whatever kind and character.

         Like-Kind Notice shall have the meaning given to it in Section 2.5.

         Loss and Expense shall have the meaning given to it in Section 8.2.

         material, materially or materiality for the purposes of this Agreement,
shall, unless specifically stated to the contrary,  be determined without regard
to the fact that various  provisions of this Agreement set forth specific dollar
amounts.

         Material  Agreement shall mean, with respect to Diablo, any Contractual
Obligation  which (a) was not entered into in the  ordinary  course of business,
(b) was entered into in the ordinary  course of business  which (i) involved the
purchase,  sale or lease  of  goods  or  materials,  or  purchase  of  services,
aggregating more than $20,000,  (ii) extends for more than three (3) months,  or
(iii) is not  terminable on thirty (30) days or less notice  without  penalty or
other payment,  (c) involves a capitalized  lease obligation or Indebtedness for
Money  Borrowed,  (d) is or  otherwise  constitutes  a written  agency,  broker,
dealer,  license,  distributorship,  sales  representative  or  similar  written
agreement,  (e) is with the United States Forest Service or any other Authority,
or (f) involves the management by Diablo of any communication tower of any other
Person.

         Multiemployer  Plan shall mean a Plan which is a  "multiemployer  plan"
within the meaning of Section 4001(a)3 of ERISA.

         Nonassignable  Contracts  shall have the meaning given to it in Section
2.2(c).

         Nonassignable Contracts Agreement shall have the meaning given to it in
Section 6.2(n).

         Note Agreement  shall have the meaning given to it in the fifth Whereas
paragraph.

         Organic  Document  shall  mean,  with  respect  to a Person  which is a
corporation,  its charter,  its by-laws and all shareholder  agreements,  voting
trusts and similar arrangements applicable to any of its capital stock and, with
respect to a Person which is a  partnership,  its agreement and  certificate  of
partnership,  any  agreements  among  partners,  and any  management and similar
agreements  between the partnership  and any general  partners (or any Affiliate
thereof).

         Other  Agreement  shall  have the  meaning  given  to it in the  fourth
Whereas paragraph.

         Other  Agreement  Claims shall have the meaning  given to it in Section
8.3(a).

                                       A-9


<PAGE>



         PBGC shall mean the Pension Benefit Guaranty Corporation and any Entity
succeeding to any or all of its functions under ERISA.

         Permitted  Liens  shall  mean (a) Liens  current  taxes not yet due and
payable, (b) such imperfections of title, easements,  encumbrances and mortgages
or  other  Liens,  if  any,  as  are  not,  individually  or in  the  aggregate,
substantial in character,  amount or extent and do not  materially  detract from
the value, or materially interfere with the present use, of the property subject
thereto or affected thereby,  or otherwise  materially impair the conduct of the
Diablo Business,  and (c) such other Liens as are permitted by the provisions of
this Agreement to be in place on the Closing Date.

         Person shall mean any natural individual or any Entity.

         Personal  Property shall mean all of the machinery,  equipment,  tools,
vehicles, furniture, leasehold improvements, office equipment, plant, inventory,
spare parts and other  tangible  personal  property which are owned or leased by
Diablo and used or useful as of the date hereof in the  conduct of the  business
or operations of the Diablo Business,  plus such additions thereto and deletions
therefrom arising in the ordinary course of business between the date hereof and
the Closing Date.

         Plan shall mean,  with respect to any Person and at a particular  time,
any employee benefit plan which is covered by ERISA and in respect of which such
Person or an ERISA  Affiliate is (or, if such plan were terminated at such time,
would under  Section 4069 of ERISA be deemed to be) an  "employer" as defined in
Section  3(5) of ERISA,  but only to the extent that it covers or relates to any
officer, employee or other Person involved in the ownership and operation of the
Assets or the conduct of the business of the Diablo Business.

         Prepaid Expense shall mean any item which in accordance with GAAP would
be treated as an expense and which has been paid by Diablo  prior to the Closing
and relates to a period subsequent to the Closing.

         Prepaid Revenue shall mean any item which in accordance with GAAP would
be treated as revenue and which has been received by Diablo prior to the Closing
and relates to a period subsequent to the Closing.

         Private Authorizations shall mean all approvals, concessions, consents,
franchises,  licenses,  permits,  and other authorizations of all Persons (other
than   Authorities)   including   without   limitation  those  with  respect  to
Intellectual Property.

         Pro Ratable Taxes shall mean real estate and other property  Taxes,  ad
valorem Taxes,  gross  receipts  Taxes and similar Taxes,  but shall not include
federal, state or local income Taxes, franchise Taxes or other Taxes measured by
or based upon income or gain on sale or other disposition of property or assets.

         Purchase Price shall have the meaning given to it in Section 2.3.

         Retained  Accounts  Receivable  shall have the  meaning  given to it in
Section 2.4.

         Real Property shall mean all of the fee estates and buildings and other
fixtures and improvements  thereon,  leasehold  interest,  easements,  licenses,
rights to access,  right-of-  way, and other real  property  interest  which are
owned or used by Diablo as of the date hereof,  in the  operations of the Diablo
Business,  plus such additions  thereto and deletions  therefrom  arising in the
ordinary course of business between the date hereof and the Closing Date.


                                      A-10


<PAGE>



         Regulations  shall mean the federal income tax regulations  promulgated
under  the Code,  as such  Regulations  may be  amended  from time to time.  All
references  herein to specific  sections of the Regulations shall be deemed also
to refer to any  corresponding  provisions  of succeeding  Regulations,  and all
references  to  temporary  Regulations  shall  be  deemed  also to  refer to any
corresponding provisions of final Regulations.

         Representatives shall have the meaning given to it in Section 5.1(a).

         SEC shall mean the United States Securities and Exchange Commission, or
any successor Authority.

         Securities Act shall mean the Securities Act of 1933, and the rules and
regulations of the SEC  thereunder,  all as from time to time in effect,  or any
successor  law,  rules or  regulations,  and any  reference to any  statutory or
regulatory  provision  shall  be  deemed  to be a  reference  to  any  successor
statutory or regulatory provision.

         Spight shall have the meaning given to it in Section 6.2(j).

         Spight  Noncompetition  Agreement shall have the meaning given to it in
Section 6.2(j).

         Subsidiary shall mean, with respect to a Person,  any Entity a majority
of the capital stock  ordinarily  entitled to vote for the election of directors
of which,  or if no such voting stock is  outstanding,  a majority of the equity
interests of which, is owned directly or indirectly, legally or beneficially, by
such Person or any other Person controlled by such Person.

         Tax (and "Taxable",  which shall mean subject to Tax), shall mean, with
respect to any Person,  (a) all taxes (domestic or foreign),  including  without
limitation any income (net, gross or other including  recapture of any tax items
such as  investment  tax  credits),  alternative  or add-on  minimum tax,  gross
income,  gross receipts,  gains,  sales, use, leasing,  lease, user, ad valorem,
transfer, recording, franchise, profits, property (real or personal, tangible or
intangible),  fuel,  license,  withholding on amounts paid to or by such Person,
payroll,  employment,  unemployment,  social security, excise, severance, stamp,
occupation, premium, environmental or windfall profit tax, custom, duty or other
tax, or other like  assessment or charge of any kind  whatsoever,  together with
any  interest,  levies,  assessments,  charges,  penalties,  addition  to tax or
additional  amount  imposed  by any Taxing  Authority,  (b) any joint or several
liability of such Person with any other Person for the payment of any amounts of
the type  described in (a) and (c) any  liability of such Person for the payment
of any  amounts  of the type  described  in (a) as a result  of any  express  or
implied obligation to indemnify any other Person.

         Tax  Allocation  Schedule shall have the meaning given to it in Section
2.3.

         Tax  Claim  shall  mean any Claim  which  relates  to Taxes,  including
without limitation the representations and warranties set forth in Section 3.11.

         Tax Return or Returns shall mean all returns, consolidated or otherwise
(including without limitation  information  returns),  required to be filed with
any Authority with respect to Taxes.

         Taxing   Authority  shall  mean  any  Authority   responsible  for  the
imposition of any Tax.

         Title Company shall have the meaning given to it in Section 5.7.

         Title Reports shall have the meaning given to it in Section 5.7.


                                      A-11


<PAGE>


         Termination Date shall have the meaning given to it in Section 7.1.

         Transactions shall mean the transactions contemplated to be consummated
on or prior to the Closing Date,  including without  limitation the purchase and
sale of the Diablo Assets and the Diablo  Business and the  execution,  delivery
and performance of the Collateral Documents.

         U.S.  Navy Claim means all  obligations,  liabilities  and other Claims
with respect to the T.V. Hill Site and the U.S. Navy,  including those of Watson
Communications  Systems,  Inc., a former  partner of Diablo  and/or  Spight with
respect  thereto and of Diablo to the U.S.  Navy with respect to its guaranty of
the obligations and liabilities of Watson Communications Systems, Inc.




                                      A-12