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                       HIGHWAYMASTER COMMUNICATIONS, INC.

                              AMENDED AND RESTATED
                             STOCKHOLDERS' AGREEMENT

                                   DATED AS OF

                               SEPTEMBER 27, 1996



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                                TABLE OF CONTENTS

                  AMENDED AND RESTATED STOCKHOLDERS' AGREEMENT


                                                                            Page


     Section 1.     Definitions. . . . . . . . . . . . . . . . . . . . . . . . 2

     Section 2.     The Recapitalization; Amendment of Certificate of
                    Incorporation  . . . . . . . . . . . . . . . . . . . . . . 6

     Section 3.     Transfer of Securities . . . . . . . . . . . . . . . . . . 7

     Section 4.     Registration Rights. . . . . . . . . . . . . . . . . . .  10

     Section 5.     Governance . . . . . . . . . . . . . . . . . . . . . . .  28

     Section 6.     Miscellaneous. . . . . . . . . . . . . . . . . . . . . .  35








                                      ii



                              AMENDED AND RESTATED 
                             STOCKHOLDERS' AGREEMENT

          This AMENDED AND RESTATED STOCKHOLDERS' AGREEMENT ("AGREEMENT"), dated
as of September 27, 1996, amends and restates in its entirety that Stockholders'
Agreement, dated as of February 4, 1994 (the "Original Agreement"), by and among
HIGHWAYMASTER COMMUNICATIONS, INC., a Delaware corporation (previously named HM
HOLDING CORPORATION) (the "COMPANY"), and the other Persons (as hereinafter
defined) identified in Appendix A hereto, as the Original Agreement has been
amended by the amendments and addenda set forth in Appendix B hereto, adds an
additional party hereto, Southwestern Bell Wireless Holdings, Inc., a Delaware
corporation ("SBW") and provides that the Persons identified in Appendix C
hereto shall no longer be parties hereto.


                                    RECITALS:

          A.   Simultaneously with the execution hereof, SBW is acquiring
certain shares of Series D Preferred Stock (as hereinafter defined) of the
Company pursuant to the Purchase Agreement dated as of the date hereof, by and
between the Company and SBW (the "PURCHASE AGREEMENT") and agreeing to provide
certain services to the Company pursuant to a separate technical services
agreement.

          B.   Certain of the parties hereto have effected, or agreed to effect,
the Recapitalization reflected in Sections 2(a), (b) and (c) hereof.

          C.   Pursuant to Section 7(h) of the Original Agreement with respect
to the terms hereof generally and Section 4(k) of the Original Agreement with
respect to the registration rights provisions, holders of a sufficient number of
Shares (as hereinafter defined) have executed this Agreement thereby amending
and restating the Original Agreement, as amended to date, in its entirety as set
forth herein, for the purpose of regulating certain aspects of the Stockholders'
relationships with regard to each other and the Company.

          D.   Immediately after the execution hereof, the Stockholders (as
hereinafter defined) will consist of (i) Carlyle HighwayMaster Investors, L.P.,
Carlyle HighwayMaster Investors II, L.P., H.M. Rana Investments Limited, TC
Group, L.L.C., Mark D. Ein, Chase Manhattan Investment Holdings, Inc. and
Archery Partners (the "CARLYLE ENTITIES"), (ii) Clipper/Merban, L.P.,
Clipper/Merchant Partners, L.P. and Clipper 


                                       1



Capital Associates, L.P. (the "CLIPPER ENTITIES"), (iii) Erin Mills 
International Investment Corporation, The Erin Mills Investment Corporation 
and The Erin Mills Development Corporation (the "ERIN MILLS COMPANIES"), (iv) 
William C. Kennedy, Jr., Donald M. Kennedy, William C. Saunders, Robert S. 
Folsom and Robert T. Hayes and (v) SBW.

          E.   Simultaneously with the execution hereof, the Company is issuing
to SBW a warrant certificate for warrants (the "Warrants") for 5,000,000 shares
of Common Stock (as hereinafter defined) in consideration for SBW entering into
the transactions contemplated by the Purchase Agreement and the other
Transaction Documents (as hereinafter defined).

                         AGREEMENT:

          NOW THEREFORE, in consideration of the mutual covenants herein
contained and for other good and valuable consideration, the Company and
Stockholders agree as follows:

          Section 1.     DEFINITIONS.  As used herein, the following terms shall
have the following meanings:

          "AFFILIATE" of any specified person or entity means any person or
entity directly or indirectly controlling or controlled by or under direct or
indirect common control with such person or entity.

          "ANTI-TAKEOVER PROVISION" shall have the meaning set forth in Section
5(g) hereto.

          "BENEFICIALLY OWN"  (and correlative terms) means, with respect to any
shares of Common Stock or other securities, to be entitled, directly or
indirectly through one or more intermediaries, to all material incidents of
ownership with respect to such securities, including, but not limited to, (i)
the right to vote such securities (in the case of voting securities), (ii)
subject to any transfer restrictions, the right to dispose of such securities
and to receive any proceeds realized from the disposition thereof and (iii) the
right to receive any dividends and other distributions with respect to such
securities.

          "BY-WORD STOCKHOLDER" means each of William C. Kennedy, Jr., Donald M.
Kennedy, William C. Saunders, Robert T. Hayes and Robert S. Folsom.

          "CARLYLE ENTITIES" shall have the meaning set forth in the Recitals
hereto.


                                       2



          "CARLYLE STOCKHOLDER" means each of the Carlyle Entities and any
Permitted Assign (as hereinafter defined) who acquires shares of Common Stock
directly or indirectly from a Carlyle Stockholder and who executes a
supplemental agreement as contemplated in Section 6(b) hereof, in his, her or
its capacity as a holder of Common Stock.

          "CLASS B COMMON STOCK" means the new class of Company Common Stock,
par value $0.01 per share, to be authorized as contemplated in Section 2(e)
hereof, the terms of which are set forth on Exhibit B to the Purchase Agreement.

          "CLIPPER ENTITIES" shall have the meaning set forth in the Recitals
hereto.

          "CLIPPER STOCKHOLDER" means each of the Clipper Entities.

          "COMMISSION" means the Securities and Exchange Commission.

          "COMMON STOCK" means the Common Stock, par value $.01 per share, of
the Company and any other capital stock of the Company into which such Common
Stock is reclassified or reconstituted.

          "COMPANY COMMON STOCK" means the Common Stock and the Class B Common
Stock.

          "DEMAND REGISTRATION" shall have the meaning set forth in Section 4(b)
hereof.

          "DIRECTOR" means a member of the Board of Directors of the Company.

          "ERIN MILLS COMPANIES" shall have the meaning set forth in the
Recitals hereto.

          "ERIN MILLS STOCKHOLDER" means each of the Erin Mills Companies and
any Permitted Assign who acquires shares of Common Stock directly or indirectly
from an Erin Mills Company and who executes a supplemental agreement as
contemplated in Section 6(b) hereof and, solely for purposes of Section 4
hereof, Robert S. Folsom and Robert T. Hayes, in each case in his, her or its
capacity as a holder of Common Stock.

          "EXCLUDED OPTIONS" means options, warrants, rights or obligations to
acquire Common Stock issued by any Person other than the Company.


                                       3



          "EXCLUDED RELATED PARTY" means, with respect to any Stockholder, a
Related Party of such Stockholder which either (i) is a natural person or (ii)
is not an Affiliate of such Stockholder.

          "EXEMPT TRANSFER" shall mean the meaning set forth in Section 3(d)
hereof.

          "EXISTING LINE OF BUSINESS" shall have the meaning set forth in
Section 5(g) hereof.

          "INCENTIVE STOCK OPTION PLAN" means the HM Holding Corporation 1994
Incentive Stock Option Plan, as adopted by the Company's Board of Directors and
as amended from time to time, providing for the grant to certain management
employees of the Company and its Subsidiaries of options to purchase shares of
Common Stock.

          "MAJORITY IN INTEREST" means, with respect to any specified group of
Stockholders, Stockholders included in such group which hold more than fifty
percent (50%) of the aggregate shares of Common Stock held collectively by such
group of Stockholders on a Fully Diluted Basis (as hereinafter defined).

          "ON A FULLY DILUTED BASIS" with respect to the Company's Common Stock
means on a basis that takes into account the number of shares of Common Stock
which are issued and outstanding plus the number of shares of Common Stock
issuable upon conversion of any outstanding Series D Preferred Stock and, once
authorized and issued, Class B Common Stock or pursuant to outstanding options,
warrants, rights or obligations  to purchase or subscribe for shares of Common
Stock or securities of the Company which are exchangeable or exercisable into
shares of Common Stock as of the applicable date of determination, other than
the Warrants, Excluded Options and employee stock options.

          "PERMITTED ASSIGN" shall have the meaning set forth in Section 6(b)
hereof.

          "PERSON" means any individual, partnership, corporation, association,
joint stock company, trust, joint venture, unincorporated organization or
governmental entity or department, agency or political subdivision thereof.

          "PIGGYBACK REGISTRATION" shall have the meaning set forth in
Section 4(a) hereof.


                                       4



          "PUBLIC TRANSFEREE" means any subsequent holder of Common Stock who
acquires Shares from a Stockholder pursuant to an effective registration
statement under the Securities Act (as hereinafter defined) or pursuant to
Rule 144 promulgated thereunder.

          "RECAPITALIZATION AGREEMENT" means the Recapitalization Agreement,
dated as of the date hereof, among the Company, certain Erin Mills Stockholders,
Carlyle Stockholders and Clipper Stockholders, a copy of which is attached as
Exhibit A hereto.

          "RECAPITALIZATION SHARES" shall have the meaning set forth in
Section 4(c) hereof.

          "REGULATORY RELIEF" means that SBC Communications, Inc. or its
Affiliates, in their sole judgment, have obtained all necessary federal and
state regulatory approvals to provide landline, interLATA long-distance service
pursuant to the Communications Act of 1934, as amended by The Telecommunications
Act of 1996.

          "RELATED PARTY"  with respect to any Stockholder means:  (A) an
Affiliate of such Stockholder; (B) a trust, corporation, partnership or other
entity, the beneficiaries, stockholders, partners, or owners, or persons holding
a controlling interest of which consist of such Stockholder and/or its
Affiliates; (C) with respect to any Stockholder who is an individual, such
Stockholder's spouse, siblings, children or parents; (D) with respect to any
Stockholder which is a partnership, such Stockholders' partners as of the date
hereof; and (E) with respect to any Stockholder which is a corporation, such
Stockholder's stockholders as of the date hereof.

          "SBW STOCKHOLDER" means SBW and any Affiliate of SBW who acquires
Shares from SBW and who executes a supplemental agreement as contemplated in
Section 6(b) hereof.

          "SECURITIES ACT" means the Securities Act of 1933, as amended from
time to time, and the rules and regulations of the Securities and Exchange
Commission promulgated thereunder.

          "SERIES D PREFERRED STOCK" means the Series D Participating
Convertible Preferred Stock, par value $.01 per share, of the Company, the
Certificate of Designation for which is set forth in Exhibit A to the Purchase
Agreement.

          "SHARES" means (i) any shares of the capital stock of the Company and
(ii) any securities convertible into, and any rights, options or warrants
exchangeable or


                                       5



exercisable for, any of the shares of the capital stock of the Company, in
either case, at any time outstanding.

          "STOCKHOLDERS" means the By-Word Stockholders, the Carlyle
Stockholders, the Clipper Stockholders, the Erin Mills Stockholders and the SBW
Stockholders.

          "SUBSIDIARY" of any specified person or entity means a corporation or
other entity of which a majority of the voting power of the equity securities or
other equity interests is owned, directly or indirectly, by such specified
person or entity or any Subsidiary of such specified person or entity.

          "TRANSACTION DOCUMENTS" shall have the meaning set forth in the
Purchase Agreement.

          "TRANSFER" shall have the meaning set forth in Section 3(a) hereof.
          "WARRANTS" shall have the meaning set forth in the Recitals hereto.

          Section 2.     THE RECAPITALIZATION; AMENDMENT OF CERTIFICATE OF
                         INCORPORATION.

          (a)  ERIN MILLS COMPANIES.

          (1)  $10 MILLION INVESTMENT.  Simultaneously with the execution
     hereof, Erin Mills International Investment Corporation and one of its
     affiliates are  investing $10.0 million in cash in the Company in
     exchange for 800,000 shares of Common Stock, as provided in the
     Recapitalization Agreement.

          (2)  SERIES B PREFERRED STOCK.  Simultaneously with the execution
     hereof, the Series B Preferred Stock owned by The Erin Mills
     Development Corporation and certain of its affiliates and by Robert S.
     Folsom and Robert T. Hayes is being exchanged for 864,000 shares of
     Common Stock, as provided in the Recapitalization Agreement.

          (b)  CARLYLE AND CLIPPER ENTITIES.  Simultaneously with the execution
hereof, the promissory notes in the aggregate principal amount of approximately
$12.7 million held by certain Carlyle Stockholders and the Clipper Stockholders
together with accrued and unpaid interest in the amount of approximately
$63,000, which were issued by the Company pursuant to the Note Exchange and
Amendments Agreement, dated 


                                       6



as of May 26, 1995, are being converted into shares of Common Stock at a 
price of $12.50 per share, as provided in the Recapitalization Agreement.

          (c)  TERMINATION OF SUBSCRIPTION AGREEMENT.  Simultaneously with the
execution hereof, the Company, certain Carlyle Stockholders and the Clipper
Stockholders are terminating certain provisions of the Subscription Agreement,
dated as of February 4, 1994, as provided in the Recapitalization Agreement.

          (d)  BYLAWS.  Simultaneously with the execution hereof, the Company
has amended the Bylaws as set forth as Exhibit B hereto.

          (e)  AMENDMENT OF CERTIFICATE OF INCORPORATION.  The Stockholders
listed on Appendix D have granted written consents and irrevocable proxies to
SBW covering the shares of Common Stock owned by them with respect to the
amendment of the Certificate of Incorporation as set forth on Exhibit B to the
Purchase Agreement and the issuance of the Common Stock pursuant to the exercise
of the Warrants, and SBW has delivered to the Company written consents covering
such shares, and immediately following the issuance of the Series D Preferred
Stock, will deliver to the Company a written consent covering such shares, each
approving such amendment.  On the twentieth day following the mailing of an
information statement to the Company's stockholders in compliance with
Regulation 14C promulgated under the Securities Exchange Act of 1934, the
Company will cause the Certificate of Amendment to be filed with the Secretary
of State of the State of Delaware.

          Section 3.     TRANSFER OF SECURITIES

          (a)  GENERAL PROHIBITION ON TRANSFER.  None of the Stockholders
     shall sell, assign, transfer, pledge, encumber or in any way dispose
     of ("TRANSFER") any Shares unless (i) such Stockholder shall have
     delivered to the Company an opinion of counsel to such Stockholder, in
     form and substance reasonably satisfactory to the Company, to the
     effect that such Transfer is exempt from the registration requirements
     of the Securities Act or (ii) the registration requirements of the
     Securities Act have been complied with in connection with such
     Transfer, provided, however, that the Company shall be entitled in its
     sole discretion to waive the requirement that an opinion of counsel be
     delivered pursuant to this Section 3(a) if it determines that a
     Transfer is in accordance with applicable law.

          (b)  TRANSFER BY FIRST REFUSAL STOCKHOLDERS.  None of the Carlyle
     Stockholders, the Erin Mills Stockholders (other than Robert S. Folsom
     and 


                                       7



     Robert T. Hayes), William C. Kennedy, Jr. or William C. Saunders
     (collectively the "First Refusal Stockholders") shall Transfer any
     Shares unless (i) such First Refusal Stockholder has complied with the
     provisions of this Section 3(c) to the extent applicable to such
     Transfer and (ii) the transferee (if other than a Public Transferee or
     an Excluded Related Party) has agreed to become a party to, and be
     bound by the terms of, Section 3 of this Agreement pursuant to a
     supplemental agreement hereto in form and substance reasonably
     satisfactory to the Company and SBW, executed by such transferee
     (provided, however, that the requirement set forth in this clause (ii)
     shall not apply to any transferee (other than a Permitted Assign or a
     transferee pursuant to Section 3(d) who is not an Excluded Related
     Party) acquiring Shares from a Seller (as hereinafter defined) after
     the earlier of (A) the date of Regulatory Relief and (B) September 27,
     1997 pursuant to a sale effected by such Seller in compliance with the
     provisions of subsection (c) below).  Notwithstanding the foregoing,
     no First Refusal Stockholder shall be required to execute a
     supplemental agreement.

          (c)  RIGHT OF FIRST REFUSAL.

               (i)  If any First Refusal Stockholder (a "SELLER") receives
     a bona fide offer, which the Seller desires to accept ("Offer") to
     purchase any or all of the Shares (the "TRANSFER STOCK") then owned by
     such Seller from any person (an "Offeror"), such Seller shall notify
     SBW in writing of the terms of such Offer, which notice shall identify
     the Offeror, the price offered, and all the other material terms and
     conditions of such Offer.  In addition, if a Seller wishes to sell to
     the public pursuant to a registration statement under the Securities
     Act or pursuant to Rule 144 promulgated thereunder (a "Public Sale"),
     the Seller shall notify SBW in writing of the proposed terms of the
     Public Sale, which Public Sale shall also constitute an Offer for the
     purposes hereof.  The Seller shall provide a written notice (the
     "NOTICE") of an Offer to SBW promptly, but in no event later than five
     (5) business days following the determination by the Seller that it
     desires to accept an Offer which does not relate to a Public Sale. 
     The Notice shall contain an irrevocable offer to sell the Transfer
     Stock to SBW at a price equal to the price and upon substantially the
     same terms as the terms contained in such Offer; provided, however,
     that (A) if such Offer shall relate to a proposed Public Sale, the
     Notice shall offer to sell the Transfer Stock at a price determined by
     the Seller (which in the case of a registered public offering shall
     not be higher than the price the Seller in good faith 


                                       8



     believes can be obtained in such offering), minus, in the case of a 
     registered public offering pursuant to a firm commitment underwriting, 
     customary underwriting commissions, and (B) if the terms of the Offer 
     entitle the Offeror to purchase the Transfer Stock for securities of 
     such Offeror (the "OFFERED SECURITIES") or other property, SBW shall be 
     entitled to purchase the Transfer Stock for an amount of cash equal to 
     the fair market value of the Offered Securities or such other property.  
     SBW shall have the irrevocable right and option (the "RIGHT OF FIRST 
     REFUSAL"), to accept such irrevocable offer as to all Shares as to which 
     the Offer is made (except in the event of a Public Sale pursuant to Rule 
     144, in which event SBW may accept as to any number of Shares) by 
     providing the Seller with an irrevocable written notice of acceptance 
     within fifteen (15) business days, or, in the case of a Public Sale 
     pursuant to Rule 144, five (5) business days, after the date the Notice 
     is received (the "NOTICE PERIOD").  The closing of the purchases of the 
     Transfer Stock by SBW shall take place at the principal office of SBW no 
     later than the fifth (5th) business day after the acceptance by SBW.  At 
     such closing, SBW shall deliver a certified check or checks or wire 
     transfer in the appropriate amount to the Seller against delivery of 
     certificates representing the Transfer Stock so purchased, duly endorsed 
     in blank by the person or persons in whose name a stock certificate is 
     registered or accompanied by a duly executed assignment separate from 
     the certificate with the signatures thereon guaranteed by a commercial 
     bank or trust company. If SBW does not elect to purchase the Transfer 
     Stock during the Notice Period or if SBW fails or refuses for any reason 
     (including, but not limited to, the existence of any requirement that 
     SBW obtain any required regulatory approval) to complete the closing of 
     the purchase of any Transfer Stock upon the day specified above, the 
     Seller shall have ninety (90) days from the end of the Notice Period 
     (the "SALES PERIOD") in which to Transfer all of the Transfer Stock 
     pursuant to the Offer to the Offeror or in a Public Sale, it being 
     understood that (A) in a registered public offering the sales price may 
     be greater than or less than the Offer price and (B) in any other 
     transaction the sales price and other terms of the Transfer may be more 
     favorable to the Seller than those set forth in the Notice.  In 
     addition, Seller may not knowingly make a Public Sale to any purchaser 
     which Seller knows to own in excess of 5% of the Common Stock, provided 
     that this restriction shall not create any duty of inquiry on the part 
     of the Seller.  Promptly after any sale pursuant to this Section 3(c), 
     the Seller shall notify SBW of the consummation thereof and shall 
     furnish such evidence of the completion (including time of completion) 
     of such sale 


                                       9



     and of the terms thereof as SBW may reasonably request.  If, at the 
     termination of the Sales Period, the Seller has not completed the sale 
     of the Transfer Stock to the Offeror or in a Public Sale, all of the 
     restrictions on Transfer contained in this Section 3(c) shall again be 
     in effect with respect to all such Seller's Transfer Stock.

          (d)  EXEMPT TRANSFER.  The following transactions shall
     constitute "EXEMPT TRANSFERS" for the purpose of Section 3 and shall
     be exempt from the requirements of subsection (c), but not subsections
     (a) and (b):  (i) a Transfer of Shares by a First Refusal Stockholder
     to SBW, (ii) a Transfer by a Stockholder of Shares by will or
     intestate succession to such Stockholder's executors, administrators,
     testamentary trustees, legatees or beneficiaries, (iii) a Transfer of
     Shares by a Stockholder to any Related Party of such Stockholder and
     (iv) a Transfer of Shares (A) by any Carlyle Stockholder to any other
     Carlyle Stockholder or to any Clipper Stockholder, (B) by any Erin
     Mills Stockholder to any other Erin Mills Stockholder or (C) by
     William C. Kennedy, Jr. or William C. Saunders to any By-Word
     Stockholder, or (vi) a Transfer of Shares that has been approved in
     writing by SBW as an Exempt Transfer.

          (e)  RESTRICTIONS ON SBW.   No SBW Stockholder shall Transfer any
     Series D Preferred Stock or Class B Common Stock except to an
     Affiliate of SBW.

          Section 4.     REGISTRATION RIGHTS.

          (a)  PIGGYBACK REGISTRATION RIGHTS.

          (1)  RIGHT TO PIGGYBACK. Subject to the last sentence of this
     subsection (1), whenever the Company proposes to register any shares
     of Common Stock (or securities convertible into or exchangeable for,
     or options, warrants or other rights to acquire, Common Stock) with
     the Securities and Exchange Commission (the "COMMISSION") under the
     Securities Act (other than (A) registrations on Form S-4 or Form S-8
     and (B) the registration of the Recapitalization Shares (as
     hereinafter defined) pursuant to subsection (c) below) and the
     registration form to be used may be used for the registration of the
     Registrable Securities (as defined in subsection (k) below) (a
     "PIGGYBACK REGISTRATION"), the Company will give written notice to all
     Stockholders, at least thirty-five (35) days prior to the 


                                      10




     anticipated filing date, of its intention to effect such a registration, 
     which notice will specify the proposed offering price, the kind and 
     number of securities proposed to be registered, the distribution 
     arrangements and such other information that at the time would be 
     appropriate to include in such notice, and will, subject to subsection 
     (a)(2) below, include in such Piggyback Registration all Registrable 
     Securities with respect to which the Company has received written 
     requests for inclusion therein within fifteen (15) business days after 
     the effectiveness of the Company's notice.  Except as may otherwise be 
     provided in this Agreement, Registrable Securities with respect to which 
     such request for registration has been timely received will be 
     registered by the Company and offered to the public in a Piggyback 
     Registration pursuant to this Section 4 on terms and conditions at least 
     as favorable as those applicable to the registration of shares of Common 
     Stock (or securities convertible into or exchangeable or exercisable for 
     Common Stock) to be sold by the Company and by any other person selling 
     under such Piggyback Registration.

          (2)  PRIORITY ON PIGGYBACK REGISTRATIONS. If the managing
     underwriter or underwriters, if any, advise the holders of Registrable
     Securities in writing that in its or their reasonable opinion or, in
     the case of a Piggyback Registration not being underwritten, the
     Company shall reasonably determine (and notify the holders of
     Registrable Securities of such determination), after consultation with
     an investment banker of nationally recognized standing, that the
     number or kind of securities proposed to be sold in such registration
     (including Registrable Securities to be included pursuant to
     subsection (a)(1) above) will materially adversely affect the success
     of such offering (including, without limitation, a material impact on
     the selling price), the Company will include in such registration the
     number of securities, if any, which, in the opinion of such
     underwriter or underwriters, or the Company, as the case may be, can
     be sold, without having a material adverse effect on the success of
     such offering, as follows: (i) first, the shares the Company proposes
     to sell, (ii) second, the Registrable Securities requested to be
     included in such registration by SBW, the Carlyle Stockholders, the
     Clipper Stockholders and the Erin Mills Stockholders, pro rata among
     such requesting Stockholders on the basis of their respective holdings
     of Common Stock on a Fully Diluted Basis, and (iii) third, the
     Registrable Securities requested to be included in such registration
     by the By-Word Stockholders, pro rata among such requesting


                                      11



     Stockholders on the basis of their respective holdings of Common Stock
     on a Fully Diluted Basis.

          (3)  SELECTION OF UNDERWRITERS.  If any Piggyback Registration is
     an underwritten offering, the Company (by action of the Board of
     Directors) will select a managing underwriter or underwriters to
     administer the offering, which managing underwriter or underwriters
     will be of nationally recognized standing and reasonably acceptable to
     the holders of a majority of the Registrable Securities included
     therein.

          (b)  DEMAND REGISTRATION RIGHTS.

          (1)  RIGHT TO DEMAND REGISTRATION.  Each of (A) the Carlyle
     Stockholders and the Clipper Stockholders as a group; (B) the Erin
     Mills Stockholders as a group and (C) SBW (each referred to herein as
     a "DEMANDING GROUP") shall have the right on the number of occasions
     set forth in subsection (b)(2) to make a written request of the
     Company for registration with the Commission, under and in accordance
     with the provisions of the Securities Act, of all or part of their
     Registrable Securities (a "DEMAND REGISTRATION"); PROVIDED, that (x)
     the Company shall not effect a Demand Registration unless such Demand
     Registration has been requested by persons holding at least a majority
     of the Registrable Securities held by the Demanding Group on the date
     of such written request and unless the number of Shares to be sold in
     such Demand Registration by the Demanding Group is at least 1,000,000
     shares of Common Stock, (y) if the Board of Directors determines in
     the exercise of its reasonable judgment that, due to a pending or
     contemplated acquisition or disposition, to effect such Demand
     Registration at such time would have a material adverse effect on the
     Company, the Company may defer such Demand Registration for a single
     period not to exceed one hundred eighty (180) days (but if the Company
     elects to defer any Demand Registration pursuant to the terms of this
     sentence, no Demand Registration shall be deemed to have occurred for
     purposes of this Agreement) and (z) the Company shall be obligated to
     effect only the number of Demand Registrations set forth in subsection
     4(b)(2) below.  Within ten (10) days after receipt of the request for
     a Demand Registration, the Company will send written notice (the
     "NOTICE") of such registration request and its intention to comply
     therewith to all Stockholders who are holders of Registrable
     Securities and, subject to subsection (3) below, the Company will
     include in such registration all 


                                      12



     Registrable Securities of such Stockholders with respect to which the 
     Company has received written requests for inclusion therein within 
     twenty (20) business days after the effectiveness of the Notice.  All 
     requests made pursuant to this subsection (b)(1) will specify the 
     aggregate number of Registrable Securities requested to be registered 
     and will also specify the intended methods of disposition thereof.

          (2)  NUMBER OF DEMAND REGISTRATIONS.  Each Demanding Group shall
     be entitled to two (2) Demand Registrations, and the expenses of each
     (including the fees and expenses of a total of one counsel for the
     Demanding Group in accordance with subsection (f)(2) below) shall be
     borne by the Company.  A Demand Registration shall not be counted as a
     Demand Registration hereunder until such Demand Registration has been
     declared effective by the Commission and maintained continuously
     effective for a period of at least three months or such shorter period
     when all Registrable Securities included therein have been sold in
     accordance with such Demand Registration.

          If the Company elects to issue and sell and ultimately sells any
     equity securities pursuant to any Registration Statement filed in
     connection with a Demand Registration, then such Registration shall be
     deemed not to be a Demand Registration for purposes of determining the
     number of Demand Registrations granted by this Agreement.

          (3)  PRIORITY ON DEMAND REGISTRATIONS.  If in any Demand
     Registration the managing underwriter or underwriters thereof (or in
     the case of a Demand Registration not being underwritten, the holders
     of a majority of the Registrable Securities held by the Demanding
     Group after consultation with an investment banker of nationally
     recognized standing), advise the Company in writing that in its or
     their reasonable opinion the number of securities proposed to be sold
     in such Demand Registration exceeds the number that can be sold in
     such offering without having a material adverse effect on the success
     of the offering (including, without limitation, an impact on the
     selling price), the Company will include in such registration only the
     number of securities that, in the reasonable opinion of such
     underwriter or underwriters (or such holders of Registrable Securities
     held by the Demanding Group, as the case may be) can be sold without
     having a material adverse effect on the success of the offering, as
     follows: (i) first, the Registrable Securities requested to be
     included in such Demand 


                                      13



     Registration by the Demanding Group, pro rata, among such Stockholders 
     on the basis of their respective holdings of Common Stock on a Fully 
     Diluted Basis, (ii) second, the Registrable Securities requested to be 
     included in such Demand Registration by the Erin Mills Stockholders and 
     SBW (if the Demanding Group is the Carlyle Stockholders and the Clipper 
     Stockholders), or the Carlyle Stockholders and the Clipper Stockholders, 
     as a group, and SBW (if the Demanding Group is the Erin Mills 
     Stockholders), or the Carlyle Stockholders and the Clipper Stockholders, 
     as a group, and the Erin Mills Stockholders (if the Demanding Group is 
     SBW), in all such cases pro rata among such Stockholders on the basis of 
     their respective holdings of Common Stock on a Fully Diluted Basis, 
     (iii) third, shares to be issued and sold by the Company and requested 
     to be included in such Demand Registration, and (iv) fourth, the 
     Registrable Securities requested to be included in such Demand 
     Registration by the By-Word Stockholders, pro rata among such requesting 
     Stockholders on the basis of their respective holdings of Common Stock 
     on a Fully Diluted Basis.

          (4)  SELECTION OF UNDERWRITERS.  If a Demand Registration is an
     underwritten offering, the holders of a majority of the Registrable
     Securities to be included in such Demand Registration held by members
     of the Demanding Group that initiated such Demand Registration will
     select a managing underwriter or underwriters of recognized national
     standing to administer the offering, which managing underwriter or
     underwriters shall be reasonably acceptable to the Company.

          (c)  REGISTRATION OF RECAPITALIZATION SHARES.  Within a reasonable
period prior to each Registration Date (as hereinafter defined), the Company
shall prepare and file with the Commission a registration statement on an
appropriate form in order to register the Recapitalization Shares under the
Securities Act for sale in one or more privately negotiated transactions or in
open market transactions effected on any stock exchange on which the Common
Stock is then listed, or if not so listed, on any automated quotation system to
which the Common Stock is then admitted to trading; provided, however, that if
the Board of Directors determines in the exercise of its reasonable judgment
that, due to a pending or contemplated acquisition or disposition, to effect
such registration at such time would have a material adverse effect on the
Company, the Company may defer such registration for a single period not to
exceed ninety (90) days.  The Company shall use its reasonable best efforts to
have each such registration statement declared effective by the Commission as
promptly as reasonably practicable after the filing thereof with the Commission;
provided, however, that (i) no sales of Recapitalization Shares shall be


                                      14



effected pursuant to any such registration statement prior to March 31, 1997 and
(ii) sales of an aggregate of no more than one-half of the total number of
Recapitalization Shares shall be effected pursuant to any such registration
statement prior to September 27, 1997, such dates being referred to as the
"Registration Dates".  In addition, the Company shall use its reasonable best
efforts to keep such registration statement effective for a period of at least
three months after the applicable Registration Date.  As used herein, the term
"Recapitalization Shares" shall mean the shares of Common Stock issued pursuant
to the Recapitalization Agreement to Erin Mills International Investment
Corporation as described in Section 2(a)(1) hereof and to certain Carlyle
Stockholders and Clipper Stockholders as described in Section 2(b) hereof.

          (d)  REGISTRATION PROCEDURES.  With respect to any Piggyback
Registration or Demand Registration and (except as expressly provided in
subsection (c) above) the registration to be effected pursuant to subsection (c)
above (generically, a "REGISTRATION"), the Company will, subject to subsections
4(a)(2) and 4(b)(3), as expeditiously as practicable:

          (1)  prepare and file with the Commission, within 60 days after
     mailing the applicable Notice, a registration statement or
     registration statements (the "REGISTRATION STATEMENT") relating to the
     applicable Registration on any appropriate form under the Securities
     Act, which form shall be available for the sale of the Registrable
     Securities in accordance with the intended method or methods of
     distribution thereof; PROVIDED that the Company will include in any
     Registration Statement on a form other than Form S-1 all information
     that the holders of the Registrable Securities so to be registered
     shall reasonably request and shall include all financial statements
     required by the Commission to be filed therewith, cooperate and assist
     in any filings required to be made with the National Association of
     Securities Dealers, Inc. ("NASD") or any securities exchange on which
     the Common Stock may then be listed, and use its reasonable best
     efforts to cause such Registration Statement to become effective
     promptly; PROVIDED, FURTHER, that before filing a Registration
     Statement or prospectus related thereto (a "PROSPECTUS") or any
     amendments or supplements thereto, the Company will furnish to the
     holders of the Registrable Securities covered by such Registration
     Statement and the underwriters, if any, copies of all such documents
     proposed to be filed, which documents will be subject to the
     reasonable review of such holders and underwriters and their
     respective counsel, and the Company will not file any Registration
     Statement or amendment thereto or any Prospectus or any supplement
     thereto to which 


                                      15



     the holders of a majority of the Registrable Securities covered by such 
     Registration Statement, the Demanding Group, if a Demand Registration, 
     or the underwriters, if any, shall reasonably object;

          (2)  prepare and file with the Commission such amendments and
     post-effective amendments to the Registration Statement as may be
     necessary to keep each Registration Statement effective for the
     applicable period, or such shorter period which will terminate when
     all Registrable Securities covered by such Registration Statement have
     been sold; cause each Prospectus to be supplemented by any required
     Prospectus supplement, and as so supplemented to be filed pursuant to
     Rule 424 under the Securities Act; and comply with the provisions of
     the Securities Act with respect to the disposition of all securities
     covered by such Registration Statement during the applicable period in
     accordance with the intended method or methods of distribution by the
     sellers thereof set forth in such Registration Statement or supplement
     to the Prospectus, PROVIDED, that the Company shall not be deemed to
     have used its reasonable best efforts to keep a Registration Statement
     effective during the applicable period if it voluntarily takes any
     action that would result in selling holders of the Registrable
     Securities covered thereby not being able to sell such Registrable
     Securities during that period unless such action is required under
     applicable law, and PROVIDED, FURTHER that the foregoing shall not
     apply to actions taken by the Company in good faith and for valid
     business reasons, including without limitation the acquisition or
     divestiture of assets, so long as the Company promptly thereafter
     complies with the requirements of subsection (11) of this subsection
     (d), if applicable;

          (3)  notify the selling holders of Registrable Securities and the
     managing underwriters, if any, promptly, and (if requested by any such
     person or entity) confirm such advice in writing, (A) when the
     Prospectus or any Prospectus supplement or post-effective amendment
     has been filed, and, with respect to the Registration Statement or any
     post-effective amendment, when the same has become effective, (B) of
     any request by the Commission for amendments or supplements to the
     Registration Statement or the Prospectus or for additional
     information, (C) of the issuance by the Commission of any stop order
     suspending the effectiveness of the Registration Statement or the
     initiation of any proceedings for that purpose, (D) if at any time the
     representations and warranties of the Company contemplated by
     subsection (14) below cease to be true and correct, (E) of 


                                      16



     the receipt by the Company of any notification with respect to the 
     suspension of the qualification of the Registrable Securities for sale 
     in any jurisdiction or the initiation or threatening of any proceeding 
     for such purpose, (F) of any other correspondence from the Commission 
     with respect to the Registration and (G) of the happening of any event 
     which makes any statement made in the Registration Statement, the 
     Prospectus or any document incorporated therein by reference untrue in 
     any material respect or which requires the making of any changes in the 
     Registration Statement, the Prospectus or any document incorporated 
     therein by reference in order to make the statements therein not 
     materially misleading;

          (4)  make every reasonable effort to obtain the withdrawal of any
     order suspending the effectiveness of the Registration Statement at
     the earliest possible moment;

          (5)  if requested by the managing underwriter or underwriters or
     a holder of Registrable Securities being sold in connection with an
     underwritten offering, promptly incorporate in a Prospectus supplement
     or post-effective amendment such information as the managing
     underwriters and either the holders of a majority of the Registrable
     Securities being sold or the Demanding Group, if a Demand
     Registration, agree should be included therein relating to the plan of
     distribution with respect to such Registrable Securities, including,
     without limitation, information with respect to the number of
     Registrable Securities being sold to such underwriters the purchase
     price being paid therefor by such underwriters and with respect to any
     other terms of the underwritten (or best efforts underwritten)
     offering of the Registrable Securities to be sold in such offering;
     and make all required filings of such Prospectus supplement or post-
     effective amendment promptly following notification of the matters to
     be incorporated in such Prospectus supplement or post-effective
     amendment;

          (6)  furnish to each selling holder of Registrable securities and
     each managing underwriter, without charge, at least one signed copy of
     the Registration Statement and any amendment thereto, including
     financial statements and schedules, all documents incorporated therein
     by reference and all exhibits (including those incorporated by
     reference);



                                      17



          (7)  deliver to each selling holder of Registrable Securities and
     the underwriters, if any, without charge, as many copies of the
     Prospectus (including each preliminary prospectus) and any amendment
     or supplement thereto as such selling holder of Registrable Securities
     and underwriters may reasonably request; the Company consents to the
     use in accordance with applicable law of each Prospectus or any
     amendment or supplement thereto by each of the selling holders of
     Registrable Securities and the underwriters, if any, in connection
     with the offering and sale of the Registrable Securities covered by
     such Prospectus or any amendment or supplement thereto;

          (8)  prior to any public offering of Registrable Securities,
     register or qualify or cooperate with the selling holders of
     Registrable Securities, the underwriters, if any, and their respective
     counsel in connection with the registration or qualification of such
     Registrable Securities for offer and sale under the securities or
     "blue sky" laws of such jurisdictions as any seller or underwriter
     reasonably requests in writing, considering the amount of Registrable
     Securities proposed to be sold in each such jurisdiction, and do any
     and all other acts or things necessary or reasonably advisable to
     enable the disposition in such jurisdictions of the Registrable
     Securities covered by the Registration Statement; PROVIDED that the
     Company will not be required to qualify generally to do business in
     any jurisdiction where it is not then so qualified or to take any
     action that would subject it to general service of process in any such
     jurisdiction where it is not then so subject;

          (9)  cooperate in all reasonable respects with the selling
     holders of Registrable Securities and the managing underwriters, if
     any, to facilitate the timely preparation and delivery of certificates
     representing Registrable Securities to be sold and not bearing any
     restrictive legends and to be in such denominations and registered in
     such names as the managing underwriters may request at least two
     business days prior to any sale of Registrable Securities to the
     underwriters;

          (10) use its reasonable best efforts to cause the Registrable
     Securities covered by the applicable Registration Statement to be
     registered with or approved by such other governmental agencies or
     authorities as may be necessary to enable the seller or sellers
     thereof or the underwriters, if any, to consummate the disposition of
     such Registrable Securities;



                                     18




          (11) upon the occurrence of any event contemplated by subsection
     (3)(F) above, prepare a supplement or post effective amendment to the
     Registration Statement or the related Prospectus or any document
     incorporated therein by reference or file any other required document
     so that, as thereafter delivered to the purchasers of the Registrable
     Securities, the Prospectus will not contain an untrue statement of a
     material fact or omit to state any material fact necessary to make the
     statements therein not misleading;

          (12) cause all Registrable Securities covered by any Registration
     Statement to be listed on each securities exchange on which similar
     securities issued by the Company are then listed, or cause such
     Registrable Securities to be authorized for trading on the Nasdaq
     National Market if any similar securities issued by the Company are
     then so authorized, if requested by the holders of a majority of such
     Registrable Securities, the Demanding Group, if a Demand Registration,
     or the managing underwriters, if any;

          (13) provide a CUSIP number for all Registrable Securities, not
     later than the effective date of the applicable Registration
     Statement;

          (14) enter into such agreements (including an underwriting
     agreement) and take all such other actions in connection therewith in
     order to expedite or facilitate the disposition of such Registrable
     Securities and in such connection, whether or not an underwriting
     agreement is entered into and whether or not the Registration is an
     underwritten Registration (A) make such representations and warranties
     to the holders of such Registrable Securities and the underwriters, if
     any, in form, substance and scope as are customarily made by issuers
     to underwriters in primary underwritten offerings; (B) obtain opinions
     of counsel to the Company and updates thereof (which counsel and
     opinions (in form, scope and substance) shall be reasonably
     satisfactory to the managing underwriters, if any, and the holders of
     a majority of the Registrable Securities being sold) addressed to each
     selling holder and the underwriters, if any, covering the matters
     customarily covered in opinions requested in underwritten offerings
     and such other matters as may be reasonably requested by such holders
     and underwriters; (C) obtain "cold comfort" letters and updates
     thereof from the Company's independent certified public accountants
     addressed to the selling holders of Registrable Securities and the
     underwriters, if any, such 



                                     19




     letters to be in customary form and covering matters of the type 
     customarily covered in "cold comfort" letters by underwriters in connection
     with primary underwritten offerings; (D) if an underwriting agreement is
     entered into, the same shall set forth in full the indemnification 
     provisions and procedures set forth in subsection (f) below with respect 
     to all parties to be indemnified pursuant to said subsection; and (E) the
     Company shall deliver such documents and certificates as may be requested 
     by the holders of a majority of the Registrable Securities being sold and 
     the managing underwriters, if any, to evidence compliance with subsection
     3(G) of this subsection (d) and with any customary conditions contained in
     the underwriting agreement or other agreement entered into by the Company.
     The above shall be done at each closing under such underwriting or similar
     agreement or as and to the extent required thereunder;

          (15) make available (at reasonable times and places) for
     inspection by a representative of the holders of a majority of the
     Registrable Securities, any underwriter participating in any
     disposition pursuant to such Registration, and any attorney or
     accountant retained by the sellers or underwriter, all financial and
     other records, pertinent corporate documents and properties of the
     Company, and cause the Company's officers, directors and employees to
     supply all information reasonably requested by any such
     representative, underwriter, attorney or accountant in connection with
     such Registration Statement; PROVIDED, that any records, information
     or documents that are designated by the company in writing as
     confidential shall be kept confidential by such Persons unless
     disclosure of such records, information or documents is required by
     court or administrative order or any regulatory body having
     jurisdiction;

          (16) otherwise use its reasonable best efforts to comply with all
     applicable rules and regulations of the Commission, and make generally
     available to its security holders, earnings statements satisfying the
     provisions of Section 11(a) of the Securities Act, no later than
     forty-five (45) days after the end of any twelve (12)-month period (or
     ninety (90) days, if such period is a fiscal year) (A) commencing at
     the end of any fiscal quarter in which Registrable Securities are sold
     to underwriters in a firm or best efforts underwritten offering, or
     (B) if not sold to underwriters in such an offering, beginning with
     the first month of the Company's first fiscal quarter commencing after
     the effective date of the Registration Statement, which statements
     shall cover said twelve (12)-month periods; and



                                     20




          (17) promptly prior to the filing of any document that is to be
     incorporated by reference into any Registration Statement or
     Prospectus (after initial filing of the Registration Statement),
     provide copies of such document to counsel to the selling holders of
     Registrable Securities and to the managing underwriters, if any, make
     the Company's representatives available for discussion of such
     document and make such changes in such document prior to the filing
     thereof as counsel for such selling holders or underwriters may
     reasonably request.

          The Company may require each seller of Registrable Securities as
     to which any Registration is being effected to furnish to the Company
     such information regarding the proposed distribution of such
     securities as the Company may from time to time reasonably request in
     writing.

          Each holder of Registrable Securities agrees by acquisition of
     such Registrable Securities that, upon receipt of any notice from the
     Company of the happening of any event of the kind described in
     subsection (3)(G) of this subsection (d), such holder will forthwith
     discontinue disposition of Registrable Securities pursuant to the
     Registration Statement until such holder's receipt of copies of the
     supplemented or amended Prospectus as contemplated by subsection (11)
     of this subsection (d), or until it is advised in writing (the
     "ADVICE") by the Company that the use of the Prospectus may be
     resumed, and has received copies of any additional or supplemental
     filings that are incorporated by reference in the Prospectus, and, if
     so directed by the Company, such holder will deliver to the Company
     (at the Company's expense) all copies, other than permanent file
     copies then in such holder's possession, of the Prospectus covering
     such Registrable Securities current at the time of receipt of such
     notice.  In the event the Company shall give any such notice, the time
     periods referred to in subsection (2) of this subsection (d) shall be
     extended by the number of days during the period from and including
     the date of the giving of such notice to and including the date when
     each seller of Registrable Securities covered by such Registration
     Statement shall have received the copies of the supplemented or
     amended prospectus contemplated by subsection (11) of this subsection
     (d) or the Advice.



                                     21




          (e)  RESTRICTIONS ON PUBLIC SALE.

          (1)  PUBLIC SALE BY HOLDERS OF REGISTRABLE SECURITIES.  To the
     extent not inconsistent with applicable law, each Stockholder, if
     requested by the managing underwriter or underwriters for any Demand
     Registration or Piggyback Registration, agrees not to effect any
     public sale or distribution of Common Stock (or securities convertible
     into or exchangeable or exercisable for Common Stock), including a
     sale pursuant to Rule 144 (or any similar provision then in force)
     under the Securities Act, during the 15 business days prior to, and
     during the ninety (90)-day period (or such shorter period as may be
     agreed to by such holders) beginning on, the effective date of the
     applicable Registration Statement (except as part of such
     Registration).

          (2)  PUBLIC SALE BY THE COMPANY AND OTHERS.  If requested by the
     managing underwriter or underwriters for any underwritten Demand
     Registration or Piggyback Registration, (i) the Company will not
     effect any public sale or distribution of Common Stock (or securities
     convertible into or exchangeable or exercisable for Common Stock)
     during the fifteen (15) business days prior to, and during the ninety
     (90)-day period beginning on the effective date of such Registration
     and (ii) the Company will cause each holder of Common Stock (or
     securities convertible into or exchangeable or exercisable for Common
     Stock) purchased from the Company at any time after the date of this
     Agreement (other than in a registered public offering) to agree not to
     effect any public sale or distribution of any such securities during
     such period described in clause (i) above (except as part of such
     Registration, if otherwise permitted).

          (3)  OTHER REGISTRATIONS.  If the Company has previously filed a
     Registration Statement with respect to Registrable Securities, and if
     such previous Registration has not been withdrawn or abandoned, the
     Company will not file or cause to be effected any other registration
     of any of its Common Stock (or securities convertible into or
     exchangeable or exercisable for Common Stock) under the Securities Act
     (except on Form S-8 or any similar successor form), whether on its own
     behalf or at the request of any holder or holders of Common Stock (or
     securities convertible into or exchangeable or exercisable for Common
     Stock), until a period of at least three (3) months has elapsed from
     the effective date of such previous Registration; provided, that if
     the holders of fifty percent (50%) or 



                                     22




     more of the aggregate number of Registrable Securities included in such
     previous Registration shall agree in writing, such period may be shortened
     to a period specified by such holders.

          (f)  REGISTRATION EXPENSES.

          (1)  All expenses incident to the Company's performance of or
     compliance with this Agreement will be borne by the Company,
     including, without limitation, all registration and filing fees, the
     fees and expenses of the counsel and accountants for the Company
     (including the expenses of any "cold comfort" letters and special
     audits required by or incident to the performance of such persons),
     all other costs and expenses of the Company incident to the
     preparation, printing and filing under the Securities Act of the
     Registration Statement (and all amendments and supplements thereto)
     and furnishing copies thereof and of the Prospectus included therein,
     the costs and expenses incurred by the Company in connection with the
     qualification of the Registrable Securities under the state securities
     or "blue sky" laws of various jurisdictions, the costs and expenses
     associated with filings required to be made with the NASD (including,
     if applicable, the fees and expenses of any "qualified independent
     underwriter" and its counsel as may be required by the rules and
     regulations of the NASD), the costs and expenses of listing the
     Registrable Securities for trading on a securities exchange or
     authorizing them for trading on NASDAQ and all other costs and
     expenses incurred by the Company in connection with any Registration
     hereunder; PROVIDED, that, except as otherwise provided in subsection
     (2) below, each Stockholder shall bear the costs and expenses of any
     underwriters' commissions, brokerage fees or transfer taxes relating
     to the Registrable Securities sold by such Stockholders and the fees
     and expenses of any counsel, accountants or other representative
     retained by Stockholder.

          (2)  Notwithstanding the foregoing and except as provided below,
     in connection with each Registration hereunder, the Company will
     reimburse the Stockholders who are holders of Registrable Securities
     being registered in any Registration hereunder for (i) the reasonable
     fees and disbursements of not more than one counsel, which counsel
     shall be chosen (x) by the holders of a majority of the Registrable
     Securities to be included therein that are held by the Demanding
     Group, in the case of a Demand Registration and (y) otherwise, by the
     holders of a majority of all 



                                     23




     Registrable Securities to be included therein, and (ii) the reasonable 
     out-of-pocket expenses (including travel costs) of the holders of 
     Registrable Securities in connection with such Registration.

          (g)  INDEMNIFICATION.

          (1)  INDEMNIFICATION BY THE COMPANY.  The Company agrees to
     indemnify, to the full extent permitted by law, each Stockholder, its
     officers, directors, partners and agents and each person who controls
     such Stockholder (within the meaning of the Securities Act and the
     Securities Exchange Act of 1934, as amended (the "EXCHANGE ACT")),
     against all losses, claims, damages, liabilities and expenses caused
     by any untrue or alleged untrue statement of a material fact contained
     in any Registration Statement, Prospectus or preliminary Prospectus or
     any omission or alleged omission to state therein a material fact
     necessary to make the statements therein (in the case of a Prospectus
     or any preliminary Prospectus, in light of the circumstances under
     which they were made) not misleading, except insofar as the same are
     caused by or contained in any information with respect to such
     Stockholder furnished in writing to the Company by such Stockholder in
     its capacity as a selling Stockholder expressly for use therein.  The
     Company will also indemnify underwriters, selling brokers, dealer
     managers and similar securities industry professionals participating
     in the distribution, their officers and directors and each person who
     controls such persons (within the meaning of the Securities Act) to
     the same extent as provided above with respect to the indemnification
     of the holders of Registrable Securities; PROVIDED, HOWEVER, if
     pursuant to an underwritten public offering of Registrable Securities,
     the Company and any underwriters enter into an underwriting or
     purchase agreement relating to such offering that contains provisions
     relating to indemnification and contribution between the Company and
     such underwriters, such provisions shall be deemed to govern
     indemnification and contribution as between the Company and such
     underwriters.

          (2)  INDEMNIFICATION BY HOLDERS OF REGISTRABLE SECURITIES.  In
     connection with any Registration in which a Stockholder is
     participating, each such Stockholder will furnish to the Company in
     writing such information with respect to such Stockholder as the
     Company reasonably requests for use in connection with any
     Registration Statement or Prospectus and agrees to indemnify, to the
     full extent permitted by law, the 



                                     24




     Company, the directors and officers of the Company signing the Registration
     Statement and each person who controls the Company (within the meaning of
     the Securities Act and the Exchange Act) against any losses, claims, 
     damages, liabilities and expenses resulting from any untrue statement of a
     material fact or any omission to state a material fact required to be 
     stated therein or necessary to make the statements in the Registration 
     Statement or Prospectus or preliminary Prospectus (in the case of the 
     Prospectus or any preliminary Prospectus, in light of the circumstances 
     under which they were made) not misleading, to the extent, but only to the
     extent, that such untrue statement or omission is contained in any 
     information with respect to such Stockholder so furnished in writing by 
     such Stockholder in its capacity as a selling Stockholder specifically for
     inclusion therein.  In no event shall the liability of any selling
     holder of Registrable Securities hereunder be greater in amount than
     the dollar amount of the net proceeds received by such holder upon the
     sale of the Registrable Securities giving rise to such indemnification
     obligation.  The Company shall be entitled to receive indemnities from
     underwriters, selling brokers, dealer managers and similar securities
     industry professionals participating in the distribution, to the same
     extent as provided above with respect to information with respect to
     such persons or entities so furnished in writing by such persons or
     entities or their representatives specifically for inclusion in any
     Prospectus or Registration Statement.

          (3)  CONDUCT OF INDEMNIFICATION PROCEEDINGS.  Any person or
     entity entitled to indemnification hereunder will (i) give prompt
     written notice to the indemnifying party after the receipt by the
     indemnified party of a written notice of the commencement of any
     action, suit, proceeding or investigation or threat thereof made in
     writing for which such indemnified party will claim indemnification or
     contribution pursuant to this Agreement; PROVIDED, HOWEVER, that the
     failure of any indemnified party to give notice as provided herein
     shall not relieve the indemnifying party of its obligations under the
     preceding subparagraphs (1) and (2), except to the extent that the
     indemnifying party is actually prejudiced by such failure to give
     notice and (ii) unless in such indemnified party's reasonable judgment
     a conflict of interest may exist between such indemnified and
     indemnifying parties with respect to such claim, permit such
     indemnifying party to assume the defense of such claim with counsel
     reasonably satisfactory to the indemnified party.  Whether or not such
     defense is assumed by the indemnifying party, the indemnifying party
     will not be subject to any liability for any settlement 



                                     25




     made without its consent (but such consent will not be unreasonably 
     withheld).  No indemnifying party will consent to the entry of any 
     judgment or enter into any settlement that does not include as an 
     unconditional term thereof the giving by the claimant or plaintiff to 
     such indemnified party of a release from all liability in respect of such
     claim or litigation.  An indemnifying party who is not entitled to, or 
     elects not to, assume the defense of a claim will not be obligated to pay 
     the fees and expenses of more than one counsel in any one jurisdiction for
     all parties indemnified by such indemnifying party with respect to
     such claim, unless in the reasonable judgment of any indemnified party
     a conflict of interest may exist between such indemnified party and
     any other of such indemnified parties with respect to such claim, in
     which event the indemnifying party shall be obligated to pay the fees
     and expenses of such additional counsel or counsels.

          (4)  CONTRIBUTION.  If for any reason the indemnification
     provided for in the preceding subparagraphs (1) and (2) is unavailable
     to an indemnified party as contemplated by the preceding clauses (1)
     and (2), then the indemnifying party in lieu of indemnification shall
     contribute to the amount paid or payable by the indemnified party as a
     result of such loss, claim, damage, liability or expense in such
     proportion as is appropriate to reflect not only the relative benefits
     received by the indemnified party and the indemnifying party, but also
     the relative fault of the indemnified party and the indemnifying
     party, as well as any other relevant equitable considerations,
     provided that no Stockholder shall be required to contribute in an
     amount greater than the difference between the net proceeds received
     by such Stockholder with respect to the sale of any Shares and all
     amounts already contributed by such Stockholder with respect to such
     claims, including amounts paid for any legal or other fees or expenses
     incurred by such Stockholder.

          (h)  RULE 144.  The Company agrees that at all times after it has
filed a registration statement pursuant to the requirements of the Securities
Act relating to any class of equity securities of the Company, it will file in a
timely manner all reports required to be filed by it pursuant to the Securities
Act and the Exchange Act and will take such further action as any holder of
Registrable Securities may reasonably request in order that such holder may
effect sales of Common Stock pursuant to Rule 144.  At any reasonable time and
upon request of any Stockholder, the Company will furnish such Stockholder and
others with such information as may be necessary to enable the Stockholder to
effect sales 



                                     26




of Common Stock pursuant to Rule 144 under the Securities Act and will 
deliver to such Stockholder a written statement as to whether it has complied 
with such requirements.  Notwithstanding the foregoing, the Company may 
deregister any class of its equity securities under Section 12 of the 
Exchange Act or suspend its duty to file reports with respect to any class of 
its securities pursuant to Section 15(d) of the Exchange Act if it is then 
permitted to do so pursuant to the Exchange Act and the rules and regulations 
thereunder.

          (i)  PARTICIPATION IN UNDERWRITTEN REGISTRATIONS.  No Stockholder may
participate in any underwritten Registration hereunder unless such Stockholder
(i) agrees to sell its Registrable Securities on the basis provided in any
underwriting arrangements approved by the persons entitled hereunder to select
the underwriter pursuant to subsections 4(a)(3) and (4)(b)(4) above, and (ii)
accurately completes in a timely manner and executes all questionnaires, powers
of attorney, underwriting agreements and other documents customarily required
under the terms of such underwriting arrangements.

          (j)  OTHER REGISTRATION RIGHTS.  The Company will not grant to any
person (including the Stockholders) any demand or piggyback registration rights
with respect to the Common Stock of the Company (or securities convertible into
or exchangeable or exercisable for Common Stock) other than piggyback
registration rights that are not inconsistent with the terms of this Section 4.
To the extent that the Company grants to any person registration rights with
respect to any securities of the Company having provisions more favorable to the
holders thereof than the provisions contained in this Agreement, the Company
will confer comparable rights to the holders of Registrable Securities under
this Agreement.  Except as provided herein, the Company will not grant any
registration rights that would permit any person or entity the right to
piggyback on any Demand Registration.

          (k)  DEFINITION OF REGISTRABLE SECURITIES.  "REGISTRABLE SECURITIES"
means the shares of Common Stock now owned or hereafter acquired by any
Stockholder, but with respect to any share, only until such time as such share
(i) has been effectively registered under the Securities Act and disposed of in
accordance with the Registration Statement covering it or (ii) has been sold to
the public pursuant to Rule 144 (or any similar provision then in force) under
the Securities Act and the Legend referred to in Section 6(a) has been removed
from the certificate representing such share (at which time such share shall
cease to be a Registrable Security).

          (l)  AMENDMENTS AND WAIVERS.  The provisions of this Section 4,
including the provisions of this sentence, may not be amended, modified or
supplemented, 



                                     27




and waivers of or consents to departures from the provisions hereof may not be
given unless approved by the Company in writing and the Company has obtained 
the written consent of Stockholders holding at least eighty-five percent 
(85%) of the then outstanding Registrable Securities (including for such 
purposes all securities convertible into or exchangeable for Registrable 
Securities, other than the Warrants).  Notwithstanding the foregoing, any 
amendment, waiver or consent that materially and adversely affects any of the 
By-Word Stockholders as a group, the Erin Mills Stockholders as a group, the 
Carlyle Stockholders as a group, the Clipper Stockholders as a group or SBW 
differently from the other Stockholders, shall require the prior written 
approval of the holders of at least a Majority in Interest of Stockholders 
who are then members of the group or the entity so affected.

          Section 5.     GOVERNANCE.

          (a)  Within fifteen days after the execution hereof, the total number
of members of the Board of Directors will be reduced to six, which number shall
be adjusted from time to time in order to give effect to the provisions of
subsection (b) below.  The Company and the Stockholders hereby agree to take, at
any time and from time to time, all action necessary (including, without
limitation, voting the shares of Company Common Stock owned or controlled by
such Stockholder, calling special meetings of stockholders, executing and
delivering written consents and requiring designees to resign) to establish the
number of total number of directors as provided herein.

          (b)  At all times from and after fifteen days after the execution
hereof (except for the addition of a second Independent Director, which shall
occur no later than the date of the next annual meeting of the stockholders of
the Company), the Board of Directors of the Company (the "BOARD") shall be
composed of Directors to be designated in the manner set forth below.  The
Company and each Stockholder hereby agree to take, at any time and from time to
time, all action necessary (including, without limitation, voting the shares of
the Company Common Stock owned or controlled by such Stockholder, calling
special meetings of stockholders and executing, delivering written consents and
requiring designees to resign) to elect Directors as provided herein.  Prior to
the receipt of Regulatory Relief, the Board shall be composed of seven (7)
members, of which two (2) Directors shall be persons designated by a Majority in
Interest of the Erin Mills Stockholders, two (2) Directors shall be persons
designated by a Majority in Interest of the By-Word Stockholders (one of which
shall be the chief executive officer of the Company), one (1) Director shall be
a person designated by a Majority in Interest of the Carlyle Stockholders and
two (2) additional Directors (or, if determined by the Nominating Committee as
hereinafter provided, three (3) additional Directors) shall be persons who are



                                     28




not employed by the Company or affiliated with any party to this Agreement
("Independent Directors").  SBW shall be entitled to designate one non-director
delegate who shall be entitled to receive notice of, in accordance with the
provisions of Section 11.6 of the Bylaws with respect to Class B Directors, and
to attend all meetings of the Board and to receive all materials received by
Directors, but who shall not be a member of the Board of Directors, shall have
no fiduciary duties to the Company, to the Board or stockholders of the Company
and shall not be entitled to vote at meetings of the Board.  Upon the conversion
of the Series D Preferred Stock into Class B Common Stock, the number of
Directors shall be increased by one who shall be a person designated by SBW and
the right to a non-director delegate shall terminate.  If SBW and its Affiliates
Beneficially Own 20% or more of the Common Stock (including Common Stock
issuable upon conversion of Series D Preferred Stock or Class B Common Stock or
other convertible securities or upon the exercise of any outstanding options,
warrants, rights or obligations, other than shares issuable upon exercise of the
Warrants and Excluded Options) on a Fully Diluted Basis, the number of Directors
shall further be increased by one and the additional Director shall also be a
designee of SBW.  For so long as SBW or its Affiliates hold Class B Common
Stock, one or both of SBW's designees will be elected by SBW as the holder of
the Class B Common Stock and will be Class B Directors, with the rights set
forth in the terms of such Class B Common Stock and the Bylaws, and which
directors will have the corporate authority to sign a stockholder consent of SBW
on behalf of each of the SBW Stockholders.

          All Independent Directors shall be nominated by a committee consisting
of one Director designated by the Erin Mills Stockholders, one Director
designated by the By-Word Stockholders, one Director designated by the Carlyle
Stockholders and, following receipt of Regulatory Relief, one Director
designated by SBW (the "Nominating Committee").  The Nominating Committee also
shall determine whether to increase the number of Independent Directors to 
three (3).

          Notwithstanding the foregoing, no Stockholder or group of Stockholders
shall be entitled to designate any Director or have such designee serve on the
Nominating Committee if the percentage of Common Stock (including Common Stock
issuable upon conversion of outstanding securities or upon the exercise of any
outstanding options, warrants, rights or obligations other than the Warrants and
Excluded Options) Beneficially Owned by such Stockholder or group of
Stockholders falls below 5% (or, with respect to the Erin Mills Stockholders and
By-Word Stockholders, 20% for the right to designate two Directors and 5% for
the right to designate one Director) on a Fully Diluted Basis.  If By-Word has
only one designee, it shall be the chief executive officer of the Company if the
chief executive officer is a By-Word Stockholder.  Upon the failure of any
Stockholder or 



                                     29




group of Stockholders to maintain the required percentage, the Stockholder or 
group of Stockholders shall require its designee to resign and the size of 
the Board may, in the determination of the Nominating Committee, either be 
reduced to eliminate such the resulting vacancy on the Board or remain the 
same (in which case, the resulting vacancy on the Board will be filled by a 
Director nominated by the Nominating Committee), provided that the 
Stockholders agree that if the chief executive officer is not a By-Word 
designee, in accordance with the provisions hereof, the chief executive 
officer shall be nominated by the Nominating Committee.

          (c)  Pursuant to Article VII of the Incentive Stock Option Plan, the
Board shall appoint a three-person Compensation Committee to administer the
Incentive Stock Option Plan.  Following receipt of Regulatory Relief, a Director
designated by SBW shall serve on the Compensation Committee.  The Compensation
Committee shall be comprised of only non-management Directors serving on the
Board.  Each Stockholder hereby agrees to take, at any time and from time to
time, all action necessary (including, without limitation, voting the shares of
the Common Stock owned or controlled by such Stockholder, calling special
meetings of stockholders and executing and delivering written consents) to cause
the Board to appoint to the Compensation Committee the number of persons meeting
the requirements of this subsection.

          (d)  The Stockholders agree that no Director may be removed except at
the request of the holders of a majority of the shares of Common Stock entitled
to appoint such Director in accordance with Section 5(b), and each Stockholder
hereby agrees to take all action necessary (including, without limitation,
voting the shares of Common Stock owned or controlled by such Stockholder,
calling special meetings of stockholders and executing and delivering written
consents) for the purpose of accomplishing the purposes of this Agreement.  If a
vacancy on the Board occurs by reason of the death, removal, resignation,
retirement or election not to serve of a designee, the remaining Directors and
the Company shall cause the vacancy thereby created to be filled by a new
designee as soon as possible (the "REPLACEMENT DIRECTOR"), who is designated in
the same manner and by the same persons specified in Section 5(b) as the
Director being replaced had been, and the Company and each Stockholder hereby
agrees to take, at any time and from time to time, all actions necessary to
accomplish the same; PROVIDED, HOWEVER, that if any group fails to designate a
representative in accordance with Section 5(b) above for a period of thirty (30)
consecutive days, then such vacancy shall be filled by the Nominating Committee
until such time as the Replacement Director is designated in accordance with
Section 5(b), at which time the term of the Director not elected in accordance
with Section 5(b) shall expire.



                                     30




          (e)  In addition to any compensation to which the members of the Board
may be entitled, the Company shall reimburse each Director for the reasonable
out-of-pocket expenses incurred by such Director (including, without limitation,
reasonable fees and expenses of counsel, accountants, or representatives, if
any) involved with such Director's services as a member of the Company.  In
addition, the Company shall obtain and maintain at all times during which this
Agreement remains in effect, at the cost and expense of the Company, director
liability insurance policies covering each member of the Board.  Such director
liability insurance policies shall be provided by a reputable nationally
recognized insurance carrier and shall provide coverage in such amounts and on
such terms as may be reasonably acceptable to each member of the Board.  Should
SBW so request, the Company will enter into contractual indemnification
arrangements with the Director reasonably satisfactory to SBW.

          (f)  In addition to any vote or consent of the Board of Directors or
its stockholders required by law or the Certificate of Incorporation, including
the terms of Series D Preferred Stock and the Class B Common Stock, the
affirmative vote of a majority of the entire Board of Directors (not merely a
quorum) shall be necessary for authorizing, effecting or validating the
following actions:

          (i)  the approval of any annual budget or business plan for the
     Company or any Subsidiary of the Company or the deviation by the
     Company or any such Subsidiary from any annual budget for the Company
     or such Subsidiary approved by the Board of Directors by more than
     five percent (5%);

          (ii) any capital expenditure or expenditures by the Company or
     any Subsidiary of the Company which, individually or in the aggregate,
     exceeds $1,000,000;

          (iii) the hiring or termination by the Company or any
     Subsidiary of the Company of any officer or senior management employee
     of the Company or such Subsidiary;

          (iv) directly or indirectly redeem, purchase or make any payments
     with respect to any stock appreciation rights, phantom stock plans or
     similar rights or plans;

          (v)  (A) sell, lease, transfer or otherwise convey, or permit any
     Subsidiary to sell, lease, transfer or otherwise convey, any assets



                                     31




     representing five percent (5%) or more of the consolidated assets of
     the Company and its Subsidiaries, (B) consolidate or merge with, or
     permit any Subsidiary to consolidate or merge with, any Person, (C)
     reclassify or otherwise change, or permit any Subsidiary to reclassify
     or otherwise change, any capital stock of the Company or any
     Subsidiary or (D) dissolve, liquidate or wind-up the Company or permit
     any Subsidiary to dissolve, liquidate or wind up such Subsidiary.

          (vi) except as expressly contemplated by the Purchase Agreement
     or the any of the Transaction Documents, authorize, issue or enter
     into any agreement providing for the issuance, or permit any
     Subsidiary to authorize, issue or enter into any agreement providing
     for the issuance (contingent or otherwise) in excess of an aggregate
     of $5,000,000 (A) any notes or debt securities containing equity
     features (including, without limitation, any note or debt securities
     convertible into or exchangeable for capital stock or other equity
     securities, issued in connection with the issuance of capital stock or
     other equity securities, or containing profit participation features)
     or (B) any capital stock or other equity securities, or any securities
     convertible into or exchangeable for any capital stock or other equity
     securities, other than issuances pursuant to the Incentive Stock
     Option Plan;

          (vii)  acquire, or permit any Subsidiary to acquire, in one
     transaction or a series of related transactions, any capital stock,
     other equity interests or assets of any Person for aggregate
     consideration in excess of $5,000,000;

          (viii)  enter into, or permit any Subsidiary to enter into, any
     agreement, contract, lease or commitment on the part of the Company or
     such Subsidiary involving the payment or provision of consideration by
     or to the Company or such Subsidiary, the fair market value of which
     exceeds $1,000,000;

          (ix)  make any capital expenditure, or permit any Subsidiary to
     make any capital expenditure, in excess of $1,000,000;

          (x)  except as expressly contemplated by the Purchase Agreement,
     amend the Certificate of Incorporation, or the Company's bylaws or
     file any resolution of the board of directors with the Secretary of
     State of the State 



                                     32




     of Delaware containing any provisions which would adversely affect or 
     otherwise impair the rights of the holders of the Common Stock;

          (xi)  enter into, or permit any Subsidiary to enter into, any
     agreement, transaction, commitment or arrangement with any of its or
     any Subsidiary's officers, directors, employees, stockholders or
     Affiliates or with any individual related by blood, marriage or
     adoption to any such individual or with any entity in which such
     Person or individual own, in the aggregate, a more than 10% beneficial
     interest, except for (A) customary employment arrangements and benefit
     programs on arms' length terms and (B) agreements, transactions,
     commitments or arrangements on arms' length terms and approved by a
     majority of the Company's disinterested directors; or

          (xii)  enter into, or permit any Subsidiary to enter into, any
     agreement to do or effect any of the foregoing.

     (g)  Following the receipt of Regulatory Relief, if SBW does not hold any
Series D Preferred Stock or Class B Common Stock but does own at least
1.6 million shares of Common Stock (including Common Stock issuable upon
conversion of outstanding securities or upon the exercise of any outstanding
options, warrants, rights or obligations, other than the Warrants and Excluded
Options) on a Fully Diluted Basis, the approval of SBW shall be required for the
following actions:

          (i)  the approval of any annual budget or business plan for the
     Company or any Subsidiary of the Company or the deviation by the
     Company or any such Subsidiary from any annual budget for the Company
     or such Subsidiary approved by the Board of Directors by more than
     five percent (5%);

          (ii) issuance by the Company of any equity securities, including
     securities convertible into equity securities (other than (A) the
     grant of employee stock options (subject to the proviso set forth in
     (D) below), (B) the issuance of equity securities in accordance with
     the terms of the Purchase Agreement or any of the other Transaction
     Documents), (C) the issuance of equity securities upon the exercise or
     conversion of securities or employee stock options that are
     outstanding as of the date hereof or (D) the issuance of equity
     securities after giving effect to the consummation of the transactions
     contemplated hereby or employee stock options granted 



                                     33




     hereafter, PROVIDED, HOWEVER, that there shall not be outstanding at 
     any time employee stock options for more than 1.5 million shares of 
     Common Stock plus the options granted to William C. Kennedy, Jr. and
     William C. Saunders that are outstanding at September 27, 1996) or
     incurrence of any indebtedness for borrowed money or evidenced by
     bonds, notes or debentures, provided that the Company can incur up to
     $5 million in indebtedness in any year without the consent of SBW;

          (iii) the hiring or termination by the Company of its chief
     executive officer, chief operating officer or chief financial officer;

          (iv) the Company's entering into any lines of business which is
     not its Existing Line of Business (as hereinafter defined) or any
     joint ventures, partnerships or similar arrangements; 

          (v)  the Company's exiting its Existing Line of Business (as
     hereinafter defined) or disposing of assets (other than
     telecommunications equipment and other assets sold in the ordinary
     course of business) in any year with a value in excess of $500,000 or
     which are otherwise material to the Company's operations;

          (vi) the adoption, implementation or acceptance (including the
     failure to opt out) of any Anti-Takeover Provision not in effect as of
     the date hereof that would be applicable to, and, in the reasonable
     determination of SBW, adversely affect, SBW and its Affiliates; or

          (vii) the taking of any corporate action that would reduce
     the number of Shares held by SBW and its Affiliates to fewer than 1.6
     million shares of Common Stock such that SBW no longer has the right
     to approve any of the actions specified in this subsection (g).

          As used in this subsection (g), the terms set forth below shall have
the following respective meanings;

          "Anti-takeover Provision" means (i) any provision of the certificate
of incorporation or bylaws of the Company or any contract, agreement or plan to
which the Company is a party or by which it is bound or any statutory provision
enacted after the date hereof which is applicable to the Company which the
Company may opt out of if the effect of such provision would be to materially
delay, hinder or prevent a change in control of the 



                                     34




Company or (ii) a stockholder rights plan or "poison pill," including the 
provisions of any preferred stock or common stock purchase rights issued 
pursuant thereto; provided, however, that such term shall not include any 
customary change of control provisions contained in employment agreements 
between the Company and any of its directors, officers or other employees or 
in any plans or agreements relating to stock options or other awards of 
equity securities made by the Company to any such persons.

          "Existing Line of Business" means a non-facilities based, enhanced
service provider that offers fleet management and/or status or information about
vehicles and/or location capabilities through mobile communications service.

          (h)  The Board shall hold, during the term of this Agreement,
regularly scheduled, in-person meetings no less frequently than six times per
year.

          (i)  At all times during which this Agreement remains in effect, each
Stockholder hereby agrees to take all action necessary (including, without
limitation, voting the shares of the Company's Common Stock owned or controlled
by such Stockholder, calling special meetings of stockholders and executing and
delivering written consents) to ensure that the By-Laws of the Company provide
that the information listed on Schedule A hereto shall be provided to each
member of the Board of Directors, at the time and in the manner required by the
provisions of Schedule A.

          (j)  The Company and each Stockholder agrees not to, and to cause its
designees on the Board not to, without the prior approval of SBW, alter, amend,
repeal or replace the Bylaws set forth on Exhibit B hereto or to enact any
Bylaws inconsistent therewith.

          (k)  For the purpose of this Section 5, Chase Manhattan Investment
Holdings, Inc., Archery Partners and their respective assigns shall not be
considered Carlyle Stockholders.

          Section 6.     MISCELLANEOUS.

          (a)  LEGEND.  The certificates representing the capital stock of the
Company held by each of the Stockholders shall bear the following legend
(provided that with respect to SBW and any certificates issued after the date
hereof such legend shall refer to this Agreement):



                                     35




          "THE SECURITIES EVIDENCED BY THIS CERTIFICATE HAVE NOT BEEN 
REGISTERED UNDER THE SECURITIES ACT OF 1933 OR THE SECURITIES LAWS OF ANY 
STATE AND MAY NOT BE SOLD OR TRANSFERRED UNLESS THERE IS AN EFFECTIVE 
REGISTRATION STATEMENT COVERING SUCH SECURITIES OR SUCH SALE OR TRANSFER IS 
EXEMPT FROM THE REGISTRATION AND PROSPECTUS DELIVERY REQUIREMENTS OF SUCH ACT 
AND ANY SIMILAR REQUIREMENTS OF ANY APPLICABLE STATE SECURITIES LAW.  THE 
SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO CERTAIN 
RESTRICTIONS SET FORTH IN A STOCKHOLDERS AGREEMENT DATED AS OF FEBRUARY 4, 
1994, A COPY OF WHICH IS AVAILABLE UPON REQUEST FROM THE SECRETARY OF THE 
COMPANY."

          If any capital stock of the Company becomes eligible for sale 
pursuant to Rule 144(k) promulgated under the Securities Act, the Company 
shall, subject to applicable law and upon the request of any holder of such 
capital stock, remove the legend set forth in this Section 6(a) from the 
certificates evidencing the shares of such capital stock held by such holder. 
In addition, (i) in connection with any Transfer of shares of any capital 
stock of the Company pursuant to any public offering registered under the 
Securities Act or pursuant to Rule 144 (or any similar rule or rules then in 
effect promulgated under the Securities Act) if such rule is available or 
(ii) if the holder of any shares of capital stock of the Company delivers to 
the Company an opinion of counsel reasonably acceptable to the Company that 
no subsequent Transfer of such shares shall require registration under the 
Securities Act, the Company shall promptly upon such Transfer deliver new 
certificates for such shares which do not bear the legend set forth in this 
Section 6(a).

          (b)  SUCCESSORS, ASSIGNS AND TRANSFEREES.  This Agreement shall be
binding upon and inure to the benefit of the parties hereto, their respective
legal representatives, heirs, legatees, successors and permitted assigns.  The
only permitted assigns (each, a "Permitted Assign") are as follows:  (i) each of
the Clipper Stockholders shall be entitled to assign any of its rights under
this Agreement to any other Clipper Stockholder; (ii) each of the Carlyle
Stockholders shall be entitled to assign any of its rights under this Agreement
to any other Carlyle Stockholder or any Related Party of a Carlyle Stockholder
(other than an Excluded Related Party); (iii) each of the By-Word Stockholders
shall be entitled to assign any of its rights under this Agreement to any other
By-Word Stockholder; (iv) each of the Erin Mills Stockholders shall be entitled
to assign any of its rights under this Agreement to any other Erin Mills
Stockholder or any Related Party of an Erin Mills Stockholder (other than an
Excluded Related Party) and (v) SBW shall be entitled to assign any of its
rights under this Agreement to any of its Affiliates.  No party hereto shall be
entitled to assign any of its rights under this Agreement to any Person which 

                                    36 


is otherwise a Permitted Assign hereunder unless, concurrently with such 
assignment, such party is Transferring all or a portion of the Shares owned 
by it to such Person in compliance with the terms and provisions set forth 
herein and such Person executes a supplemental agreement hereto in form and 
substance reasonably satisfactory to the Company pursuant to which such 
Person agrees to become a party to, and be bound by, this Agreement.

          (c)  SPECIFIC PERFORMANCE, ETC.  The Company and each Stockholder, in
addition to being entitled to exercise all rights provided herein, in the
Company's Certificate of Incorporation or granted by law, including recovery of
damages, will be entitled to specific performance of its rights under this
Agreement.  The Company and each Stockholder agrees that monetary damages would
not be adequate compensation for any loss incurred by reason of a breach by it
of the provisions of this Agreement and hereby agrees to waive the defense in
any action for specific performance that a remedy at law would be adequate.

          (d)  GOVERNING LAW.  This Agreement shall be governed by and construed
in accordance with the internal law of the State of Delaware without giving
effect to the conflict of laws provisions thereof.

          (e)  INTERPRETATION.  The headings of the sections contained in this
Agreement are solely for the purpose of reference, are not part of the agreement
of the parties and shall not affect the meaning or interpretation of this
Agreement.

          (f)  NOTICES.  Any notice or other communication required or permitted
hereunder shall be in writing and shall be delivered personally, sent by
facsimile transmission or sent by certified, registered or express mail, postage
prepaid.  SBW agrees to give the Company written notice when Regulatory Relief
has been obtained.  Any such notice shall be deemed given when so delivered
personally, sent by facsimile transmission or, if mailed, three (3) business
days after the date of deposit in the United States mail, by certified mail
return receipt requested, as follows:

          (i)  If to the Company to:

               HighwayMaster Communications, Inc.
               16479 Dallas Parkway, Suite 710 
               Dallas, Texas 75248
               Attention: William Kennedy
               Telecopier: (972) 930-7263


                                    37 


               with a copy (which shall not constitute notice) to:

               Baker & Botts, L.L.P.
               2001 Ross Avenue
               Dallas, Texas  75201
               Attention:  Geoffrey L. Newton
               Telecopier: (214) 953-6503

          (ii) If to any of the Carlyle Entitles, to

               c/o The Carlyle Group, L.P. 
               1001 Pennsylvania Avenue, N.W. 
               Suite 220 South
               Washington, D.C. 20004-2505
               Attention: Mark D. Ein
               Telecopier: (202) 347-1818

               with a copy (which shall not constitute notice) to:

               Latham & Watkins
               1001 Pennsylvania Avenue, N.W.
               Suite 1300
               Washington, D.C. 20004-2505
               Attention: Bruce E. Rosenblum, Esq.
               Telecopier:  (202) 637-2201

















                                    38 


         (iii) If to any of the Clipper Entities, to

               The Clipper Group, L.P.
               12 East 49th Street
               New York, N.Y. 10017
               Attention: Daniel V. Cahillane
               Telecopier: (212) 318-1360

               with a copy (which shall not constitute notice) to:

               Weil, Gotshal & Manges, LLP
               767 Fifth Avenue
               New York, N.Y. 10153
               Attention: Howard Chatzinoff
               Telecopier: (212) 310-8007

          (iv) If to any of the Erin Mills Companies, to

               Erin Mills International
               Trident House, Suite 204(a)
               Broad Street
               Bridgetown, Barbados
               West Indies
               Attention: Stephen Greaves
               Telecopier:  (809) 436-2120

               with a copy (which shall not constitute notice) to:

               7501 Keele Street, Suite 500 
               Concord, Ontario L4K 1Y2
                    Canada
               Attention: Gerry C. Quinn
               Telecopier: (416) 736-8373








                                    39 


          (v)  If to any of the By-Word Stockholders, to:

               HighwayMaster Communications, Inc. 
               16479 Dallas Parkway 
               Suite 710
               Dallas, Texas 75248
               Attention: William Kennedy
               Telecopier: (972) 930-7263

          (vi) If to Chase Manhattan Investment Holdings, Inc. or Archery
Partners:

               The Chase Manhattan Bank
               One Chase Plaza
               New York, NY 10081
               Attention: William K. Luby
               Telecopier: (212) 552-2958

               with a copy (which shall not constitute notice) to:

               Kirkland & Ellis
               200 East Randolph Drive
               Chicago, IL 60601
               Attention: Emile Karafiol
               Telecopier: (312) 861-2200














                                    40 


         (vii) If to Southwestern Bell Wireless Holdings, Inc.

               Southwestern Bell Wireless Holdings, Inc.
               17330 Preston Road
               Suite 100A
               Dallas, Texas 75252
               Attention: President
               Telecopier:  (972) 733-2012

               and to:

               SBC Communications, Inc.
               175 E. Houston
               San Antonio, Texas 78205
               Attention: General Attorney, Mergers & Acquisitions
               Telecopier: (210) 351-3488

               with a copy (which shall not constitute notice) to:

               Sullivan & Cromwell
               125 Broad Street
               New York, New York  10004
               Attention: Janet T. Geldzahler
               Telecopier: (212) 558-3588


Any party may change its address for notice by written notice to the other
parties in accordance with this provision.

          (g)  TERMINATION.   This Agreement will terminate and the Original
Agreement, as in effect on the date prior to the date hereof, will be deemed to
be in effect if the Purchase Agreement is terminated pursuant to Section 2(c)
thereof.  Sections 3(b) and (c) hereof shall terminate at that time that SBW and
its Affiliates cease to own at least 1.6 million shares of Common Stock
(including Common Stock issuable upon conversion of outstanding securities or
upon the exercise of any outstanding options, warrants, rights or obligations,
other than the Warrants and Excluded Options).



                                    41 


          (h)  INSPECTION AND COMPLIANCE WITH LAW.  Copies of this Agreement
will be available for inspection or copying by any Stockholder at the offices of
the Company through the Secretary of the Company.

          (i)  AMENDMENTS AND WAIVERS.  The provisions of this Agreement,
including the provisions of this paragraph (h), may not be amended, modified or
supplemented, and waivers of or consents to departures from the provisions
hereof may not be given, except by a written instrument executed by (i) the
Company, (ii) a Majority in Interest of the By-Word Stockholders, (iii) a
Majority in Interest of the Carlyle Stockholders and the Clipper Stockholders
acting as a group, (iv) a Majority in Interest of the Erin Mills Stockholders
and (v) SBW; PROVIDED, HOWEVER, that amendments of or modification to Section 4
will be subject to the requirements of Section 4(k).  No action taken pursuant
to this Agreement, including, without limitation, any investigation by or on
behalf of any party, shall be deemed to constitute a waiver by the party taking
such action.  The waiver by any party hereto of a breach of any provision of
this Agreement shall not operate or be construed as waiver of any preceding or
succeeding breach and no failure by any party to exercise any right or privilege
hereunder shall be deemed a waiver of such party's rights or privileges
hereunder or shall be deemed a waiver of such party's rights to exercise the
same at any subsequent time or times hereunder.

          (j)  TRANSFER VOID.  Any Transfer of any security of the Company in
violation of this Agreement shall be null and void and the Company covenants and
agrees that it will not register or otherwise recognize a Transfer (whether for
the purposes of shareholder voting or in connection with the distribution of
dividends or other corporate assets) of any securities which it has reason to
believe was effected in violation of this Agreement.

          (k)  COUNTERPARTS.  This Agreement may be executed in one or more
counterparts, by the original parties hereto and any successor in interest, each
of which shall be deemed to be an original and all of which together shall be
deemed to constitute one and the same agreement.

          (l)  ATTORNEYS' FEES.  In any action or proceeding brought to enforce
any provision of this Agreement, or where any provision hereof is validly
asserted as a defense, the successful party shall be entitled to recover
reasonable attorneys' fees in addition to any other available remedy.

          (m)  SEVERABILITY.  In the event that any one or more of the
provisions contained herein, or the application thereof in any circumstances, is
held invalid, illegal or 

                                    42 


unenforceable in any respect for any reason, the validity, legality and 
enforceability of any such provision in every other respect and of the 
remaining provisions contained herein shall not be in any way impaired 
thereby.




































                                    43 


     IN WITNESS WHEREOF, the parties have executed this Agreement as of the 
date first above written.

                           HIGHWAYMASTER COMMUNICATIONS, INC.,



                           By: /s/  WILLIAM C. SAUNDERS               
                               ------------------------------------------------
                           Name: William C. Saunders                  
                                 ----------------------------------------------
                           Title: President                           
                                  ---------------------------------------------


                           SOUTHWESTERN BELL WIRELESS HOLDINGS, INC.  


                           By: /s/  STAN SIGMAN                       
                               ------------------------------------------------
                           Name: Stan Sigman                          
                                 ----------------------------------------------
                           Title: President & Chief Executive Officer 
                                  ---------------------------------------------


                           CARLYLE-HIGHWAYMASTER INVESTORS, L.P.
                           By:  TC Group, L.L.C., its General Partner 


                           By: /s/  MARK D. EIN                       
                               ------------------------------------------------
                           Name: Mark D. Ein                          
                                 ----------------------------------------------
                           Title: Vice-President of Managing Member of TC Group
                                  ---------------------------------------------


                           CARLYLE-HIGHWAYMASTER INVESTORS II, L.P.   
                           By:  TC Group, L.L.C., its General Partner 


                           By: /s/  MARK D. EIN                       
                               ------------------------------------------------
                           Name: Mark D. Ein                          
                                 ----------------------------------------------
                           Title: Vice-President of Managing Member of TC Group
                                  ---------------------------------------------




                                    44


                                   H.M. RANA INVESTMENTS LIMITED


                                   By: /s/ Fahad A. Almubarak                   
                                      ----------------------------------------- 

                                      By:                                       
                                         -------------------------------------- 
                                           Name: Fahad A. Almubarak             
                                                ------------------------------- 
                                           Title: President                     
                                                 ------------------------------ 


                                   TC GROUP, L.L.C.


                                   By: /s/  MARK D. EIN                         
                                      ----------------------------------------- 
                                       Name: Mark D. Ein 
                                            ----------------------------------- 
                                       Title: Vice-President of Managing Member 
                                             ---------------------------------- 


                                   /s/  MARK D. EIN                             
                                   -------------------------------------------- 
                                   Mark D. Ein



                                   CHASE MANHATTAN INVESTMENT HOLDINGS, INC.


                                   By: /s/  JEFFREY C. WALKER                   
                                      ----------------------------------------- 
                                   Name: Jeffrey C. Walker                      
                                        --------------------------------------- 
                                   Title: Chief Executive Officer               
                                         -------------------------------------- 


                                   ARCHERY PARTNERS

                                   By: /s/  JEFFREY C. WALKER, Managing Partner 
                                      ----------------------------------------- 
                                      its General Partner


                                      By:                                       
                                         -------------------------------------- 
                                         Name: Jeffrey C. Walker                
                                              --------------------------------- 
                                         Title: Managing Partner                
                                               -------------------------------- 



                                     45

                                   CLIPPER CAPITAL ASSOCIATES, L.P.
                                   By:  Clipper Capital Associates, Inc.
                                        its General Partner


                                        By: /s/  DANIEL V. CAHILLANE            
                                           ------------------------------------ 
                                           Name: Daniel V. Cahillane            
                                                ------------------------------- 
                                           Title: Treasurer & Secretary         
                                                 ------------------------------ 


                                   CLIPPER/MERCHANT PARTNERS, L.P.
                                   By:  Clipper Capital Associates, L.P.,
                                        its General Partner
                                        By:  Clipper Capital Associates, Inc.
                                             its General Partner


                                             By: /s/  DANIEL V. CAHILLANE       
                                                ------------------------------- 
                                             Name: Daniel V. Cahillane          
                                                  ----------------------------- 
                                             Title: Treasurer & Secretary       
                                                   ---------------------------- 


                                   CLIPPER/MERBAN, L.P.
                                   By:  Clipper Capital Associates, L.P.
                                        its General Partner
                                        By:  Clipper Capital Associates, Inc.
                                             its General Partner


                                             By: /s/  DANIEL V. CAHILLANE       
                                                ------------------------------- 
                                             Name: Daniel V. Cahillane          
                                                  ----------------------------- 
                                             Title: Treasurer & Secretary       
                                                   ---------------------------- 

                                   ERIN MILLS INTERNATIONAL INVESTMENT
                                     CORPORATION


                                   By: /s/  STEPHEN L. GREAVES                  
                                      ----------------------------------------- 
                                       Name: Stephen L. Greaves                 
                                            ----------------------------------- 

                                      46 



                                       Title: General Manager                   
                                             ---------------------------------- 


                                   THE ERIN MILLS DEVELOPMENT CORPORATION


                                   By: /s/  G. C. QUINN                         
                                      ----------------------------------------- 
                                       Name: G. C. Quinn                        
                                            ----------------------------------- 
                                       Title: Executive Vice-President          
                                             ---------------------------------- 


                                   THE ERIN MILLS INVESTMENT CORPORATION


                                   By: /s/  G. C. QUINN                         
                                      ----------------------------------------- 
                                       Name: G. C. Quinn                        
                                            ----------------------------------- 
                                       Title: President                         
                                             ---------------------------------- 




                                   /s/  WILLIAM C. KENNEDY, JR.                 
                                   -------------------------------------------- 
                                   William C. Kennedy, Jr.


                                   -------------------------------------------- 
                                   Donald M. Kennedy


                                   /s/  WILLIAM C. SAUNDERS                     
                                   -------------------------------------------- 
                                   William C. Saunders


                                   /s/  ROBERT T. HAYES by Douglas Dunlap       
                                          attorney-in-fact                      
                                   -------------------------------------------- 
                                   Robert T. Hayes


                                   /s/  ROBERT S. FOLSOM by Haddon O. Winckler  
                                          attorney-in-fact                      
                                   -------------------------------------------- 
                                   Robert S. Folsom                             

                                      47


     The undersigned are executing this Agreement solely for the purpose of 
evidencing their approval of the amendment and restatement of the Original 
Agreement (as amended from time to time) in its entirety as set forth herein, 
it being understood that the undersigned shall not be deemed Stockholders for 
purposes of this Agreement and shall not have any rights or obligations 
hereunder.

                                   /s/  MARGARET D. FOLSOM                      
                                   -------------------------------------------- 
                                   Margaret D. Folsom


                                   /s/  R. STEPHEN FOLSOM                       
                                   -------------------------------------------- 
                                   Steven R. Folsom


                                   -------------------------------------------- 
                                   Joann Hayes


                                   /s/  CYNTHIA ANN HAYES                       
                                   -------------------------------------------- 
                                   Cynthia Ann Hayes


                                   /s/  ALICIA ELLEN HAYES                      
                                   -------------------------------------------- 
                                   Alicia Ellen Hayes












                                      48


                                                                      APPENDIX A

                                ORIGINAL PARTIES

Carlyle-HighwayMaster Investors, L.P.
Carlyle-HighwayMaster Investors II, L.P.
Chase Manhattan Investment Holdings, Inc.
Clipper/Merban, L.P.
Clipper/Merchant Partners, L.P.
Clipper Capital Associates, L.P.
Erin Mills International Investment Corporation
FU Enterprises Ltd.
By-Word Technologies, Inc.
Robert S. Folsom
Robert T. Hayes

















                                     A-1 

                                                                      APPENDIX B








                             AMENDMENTS AND ADDENDA

     1.   Addendum No. 1 to Subscription Agreement and Stockholders
Agreement by and among HM Holding Corporation, Carlyle-HighwayMaster Investors,
L.P., Carlyle-HighwayMaster Investors II, L.P., H.M. Rana Investments Limited,
TC Group, L.L.C., Chase Manhattan Investment Holdings, Inc., Clipper/Merban,
L.P., Clipper Merchant Partners, L.P., Clipper Capital Associates, L.P., Erin
Mills International Investment Corporation, FU Enterprises Ltd., By-Word
Technologies, Inc., Robert S. Folsom and Robert T. Hayes.

     2.   Consent of Security Holders of HM Holding Corporation and Second
Amendment to Stockholders' Agreement, dated November, 1994, among HM Holding
Corporation, By-Word Technologies, Inc., the former shareholders of By-Word
Technologies, Inc. listed on EXHIBIT A, Clipper/Merban, L.P., Clipper Merchant
Partners, L.P., Clipper Capital Associates, L.P., Carlyle-HighwayMaster
Investors, L.P., Carlyle-HighwayMaster Investors II, L.P., TC Group, L.L.C.,
H.M. Rana Investments Limited, Chase Manhattan Investment Holdings, Inc., Erin
Mills International Investment Corporation, Robert S. Folsom and Robert T.
Hayes.

     3.   Joinder Agreement to Stockholders Agreement executed as of January 3,
1995 by Mark D. Ein.

     4.  Third Amendment to Stockholders Agreement, dated as of April 28, 1995,
among HighwayMaster Communications, Inc., Archery Partners, Chase Manhattan
Investment Holdings, Inc., Carlyle-HighwayMaster Investors, L.P., Carlyle-
HighwayMaster Investors II, L.P., H.M. Rana Investments Limited, TC Group,
L.L.C., Clipper/Merban, L.P., Clipper Merchant Partners, L.P., Clipper Capital
Associates, L.P.,  Erin Mills International Investment Corporation, Robert S.
Folsom, Margaret D. Folsom, R. Stephen Folsom, Robert T. Hayes, Cynthia Ann
Hayes, Alicia Ellen Hayes, Joann Hayes, William C. Saunders, William C. Kennedy,
Jr. and Donald M. Kennedy.

     5.  Note Exchange and Amendments Agreement, dated as of May 26, 1995,
among HighwayMaster Communications, Inc., Archery Partners, Chase Manhattan
Investment Holdings, Inc., Carlyle-HighwayMaster Investors, L.P., Carlyle-
HighwayMaster Investors II, L.P., H.M. Rana Investments Limited, TC Group,
L.L.C., Clipper/Merban, L.P., Clipper Merchant Partners, L.P., Clipper Capital
Associates, L.P.,  

                                     B-1 


Erin Mills International Investment Corporation, Robert S. Folsom, Margaret 
D. Folsom, R. Stephen Folsom, Robert T. Hayes, Cynthia Ann Hayes, Alicia 
Ellen Hayes, Joann Hayes, William C. Saunders, William C. Kennedy, Jr., 
Donald M. Kennedy, Mark D. Ein and The Erin Mills Investment Corporation.
































                                     B-2 

                                                                      APPENDIX C

                                 FORMER PARTIES

Margaret D. Folsom
R. Stephen Folsom
Joann Hayes
Cynthia Ann Hayes
Alicia Ellen Hayes





























                                     C-1 


                                                                      APPENDIX D


CERTAIN STOCKHOLDERS                                            NUMBER OF SHARES


 Erin Mills International Investment Corporation                      8,141,706 
 William C. Kennedy, Jr.                                              2,029,318 
 Carlyle-HighwayMaster Investors, L.P.                                1,805,727 
 William C. Saunders                                                    892,015 
 Clipper/Merban, L.P.                                                   530,930 
 Clipper/Merchant Partners, L.P.                                        524,209 
 H.M. Rana Investments Limited                                          423,802 
 T.C. Group, L.L.C.                                                     291,315 
 Robert S. Folsom                                                       280,000 
 Carlyle-HighwayMaster Investors II, L.P.                               170,071 
























                                     D-1