EXHIBIT 2.10

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                              UPLINK SECURITY, INC.

                             SHAREHOLDERS' AGREEMENT

                                      among

                              UPLINK SECURITY, INC.

                                 NUMEREX CORP.

                                      and

                      THE SHAREHOLDERS LISTED ON EXHIBIT A

                                 July 16, 1997


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                                TABLE OF CONTENTS

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SECTION 1: GENERAL RESTRICTIONS.......................................................1
         1.1      Restriction on Transfers............................................1
         1.2      Permitted Transferees...............................................2
         1.3      Representation......................................................2
         1.4      Non-Compliance......................................................2
         1.5      Corporate Action....................................................2
         1.6      No Implied Employment...............................................2
         1.7      Execution and Delivery .............................................3
         1.8      No Conflicts .......................................................3

SECTION 2: TRIGGERING EVENTS..........................................................3
         2.1      Definition..........................................................3
         2.2      Notice of Occurrence................................................4

SECTION 3: OPTIONAL AND MANDATORY PURCHASE............................................4
         3.1      Option to Numerex...................................................4
         3.2      Option to the Company...............................................4
         3.3      Option to Remaining Shareholders....................................5
         3.4      Intentionally Omitted...............................................5
         3.5      Purchase of All Shares..............................................5
         3.6      Closing on Optional Purchase........................................5
         3.7      Right to Transfer...................................................6
         3.8      Right to Participate in Sales.......................................6
         3.9      Requirement to Participate in Sales.................................6
         3.10     Effect of Sale to Third Party by Numerex ...........................6

SECTION 4: FIRST REFUSAL ON SALE OF THE COMPANY.......................................7
         4.1      Right of First Refusal..............................................7
         4.2      Closing on First Refusal Exercise...................................7
         4.3      Sale of the Company.................................................7
         4.4      Second Call ........................................................7

SECTION 5: OPTION FOR SHAREHOLDERS' SHARES............................................8
         5.1      Option for Shareholders' Shares.....................................8
         5.2      Closing of Option Exercise..........................................9
         5.3      Negotiation Period..................................................9
         5.4      Forced Sale Option .................................................9

SECTION 6: PURCHASE AND OPTION PRICE.................................................10
         6.1      Third Party Offers.................................................10
         6.2      Other Triggering Events............................................10

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         6.3      Appraisal For Fair Market Value....................................10
SECTION 7: PAYMENT TERMS............................................................ 11

SECTION 8: OTHER PROVISIONS..........................................................12
         8.1      Representations and Warranties.....................................12
         8.2      Special Matters....................................................12
         8.3      Sale or Transfer of Shares by Initial Shareholders............ ....13
         8.4      Board of Directors.................................................13
         8.5      Future Capital Raising.............................................13
         8.6      Failure to Transfer Shares.........................................13
         8.7      Endorsement Upon Share Certificate.................................13
         8.8      Further Assurances.................................................14
         8.9      Joinder of Spouse..................................................14
         8.10     Inconsistent Agreements............................................14
         8.11     Notices............................................................14
         8.12     Settlement of Disputes.............................................15
         8.13     Amendment .........................................................15
         8.14     Waiver.............................................................15
         8.15     Termination of Prior Agreements....................................15
         8.16     Entire Understanding...............................................15
         8.17     Parties In Interest................................................16
         8.18     Severability.......................................................16
         8.19     Counterparts.......................................................16
         8.20     No Third Party Beneficiaries.......................................16
         8.21     Section Heading....................................................16
         8.22     References.........................................................16
         8.23     Controlling Law....................................................16
         8.24     Jurisdiction and Process ..........................................16
         8.25     Certain Definitions ...............................................16
         8.26     Expenses ..........................................................17

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                             SHAREHOLDERS' AGREEMENT

         PARTIES: UPLINK SECURITY, INC.,
                  a Georgia Corporation (the "Company")
                  1395 South Marietta Parkway
                  Building 200, Suite 228
                  Marietta, GA   30067

                  NUMEREX CORP.,
                  a Pennsylvania corporation ("Numerex")
                  2360 Maryland Road
                  Willow Grove, PA 19090

                  Certain shareholders listed on Exhibit A attached hereto and
                  designated thereon as "Initial Shareholders".

       DATE:      July 16, 1997

BACKGROUND: The Company is engaged in the business of developing, designing and
marketing the wireless transport of alarm signals (the "Business"). On the date
hereof, the Company, Numerex and the Initial Shareholders entered into a Stock
Purchase Agreement (the "Purchase Agreement"), pursuant to which Numerex
purchased shares of Common Stock of the Company ("Shares") directly from the
Company. Upon the date hereof, Numerex shall be the legal and beneficial owner
of 31,405 Shares. Subject to certain terms and conditions in the Purchase
Agreement and herein, Numerex may in the future acquire all or a part of the
remaining issued and outstanding Shares.

         The Company, Numerex and the Initial Shareholders desire to enter into
an agreement which (i) grants certain rights to, and imposes certain
restrictions and obligations on them in respect of the Shares of the Company
which are now or hereafter owned or held by them or any Person (as hereinafter
defined) to whom they Transfer (as hereinafter defined) such shares in
accordance with this Agreement and (ii) provides for the management and conduct
of the business of the Company, all on the terms and conditions stated in this
Agreement. Numerex, the Initial Shareholders and the Persons to whom they
Transfer Shares in accordance with this Agreement are sometimes referred to
individually as a "Shareholder" and collectively as "Shareholders".

         INTENDING TO BE LEGALLY BOUND HEREBY, and in consideration of the
mutual agreements stated below, the parties agree as follows:

SECTION 1: GENERAL RESTRICTIONS

                  1.1 Restriction on Transfers. Each Shareholder severally
agrees with each other Shareholder and with the Company that such Shareholder
shall not Transfer or attempt to Transfer, or solicit any offer for the purchase
of, any Shares now owned by such Shareholder or which such


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Shareholder may at any time hereafter own, acquire or be entitled to, except in
strict accordance with the provisions of this Agreement.

                  1.2 Permitted Transferees. Notwithstanding Section 1.1 hereof,
(a) parties to that certain Agreement dated as of March 17, 1997 by and between
John K. Collings, III, Peter John Quinn, David Geoffrey Tattersall and Uplink
Security, Inc. shall have the right to make Transfers as specifically provided
therein, provided that as a condition to receiving such shares, such transferee
agrees in writing to be bound by the terms and conditions of this Agreement, (b)
a Shareholder shall have the right to Transfer inter vivos or by will or the
laws of descent and distribution of all or a portion of his Shares outright to a
spouse or children or to a trust for the benefit of a spouse or children, if
such transferee agrees in writing to be bound by the terms and conditions of
this Agreement as if he were the transferor and an Initial Shareholder, (c) an
Initial Shareholder shall have the right to Transfer all of the Shares of the
Company owned by such Initial Shareholder to any affiliate of such Initial
Shareholder, provided that as a condition to receiving such Shares, such
affiliate agrees in writing to be bound by the terms and conditions of this
Agreement as if it were the Initial Shareholder, and (d) Numerex shall have the
right to Transfer all or a portion of the Shares of the Company owned by it to
any affiliate of Numerex or to a company which it owns, provided that as a
condition to receiving such shares, such affiliate or company agrees in writing
to be bound by the terms and conditions of this Agreement as if it were Numerex
(transferees under (a), (b), (c) and (d) being collectively called the
"Permitted Transferees"). For purposes of this Agreement, "affiliate" shall be
defined as any entity which controls or is under common control with Numerex or
the Initial Shareholders, as applicable, or which Numerex or the Initial
Shareholders, as applicable, holds at least an eighty percent (80%) controlling
interest, directly or through wholly-owned subsidiaries.

                  1.3 Representation. Each Shareholder represents and warrants
to the other Shareholders that his will and other estate planning documents and
techniques do not and shall not provide for any Transfer of Shares in violation
of Section 1.1 or any other provision of this Agreement.

                  1.4 Non-Compliance. In the event any Shareholder shall
Transfer or attempt to Transfer any Shares otherwise than in strict accordance
with the provisions of this Agreement, such action shall be void and of no
effect, and no dividends or distributions of any kind whatsoever shall be paid
by the Company in respect of such Shares (all such dividends and distributions
being deemed waived by such Shareholder), and the voting rights of such Shares
shall be suspended during the period commencing with such Shareholder's initial
failure to comply with the provisions of this Agreement and ending when (i) the
Shareholder complies with the provisions of this Agreement, or (ii) the Company,
based on the unanimous approval of its board of directors, agrees in writing to
terminate such suspension and to permit such Transfer.

                  1.5 Corporate Action. The Company shall not register the
transfer of Shares to any transferee of any Shareholder, issue any certificate
in lieu of such Shares, or issue any new Shares, unless each and every condition
hereof affecting such Shares or certificates has been satisfied.

                  1.6 No Implied Employment. Each Shareholder acknowledges and
agrees that neither the issuance of Shares to such Shareholder nor anything
contained in this Agreement gives 

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such Shareholder, if an employee of the Company, any right to be retained in the
employ of the Company, or affect the Company's right at any time to discharge or
discipline such Shareholder or to terminate his employment.

                  1.7 Execution and Delivery. The Shareholders' Agreement has
been duly executed and delivered by Numerex and constitutes a legal, valid and
binding agreement by Numerex, enforceable against Numerex and the Initial
Shareholders in accordance with its terms.

                  1.8 No Conflicts. The execution, delivery and performance of
the Shareholders' Agreement and the consummation of the transactions
contemplated hereby will not conflict with or result in a material breach or
violation of any term or provision, or (with or without notice or passage of
time, or both) constitute a default under, any indenture, mortgage, deed of
trust, trust (constructive or other), loan agreement or other agreement or
instrument to which Numerex is a party or by which Numerex is bound, or violates
any Legal Requirement applicable to or binding upon Numerex.

SECTION 2: TRIGGERING EVENTS

         2.1 Definition. The following events are "Triggering Events" with
respect to (a) the Shareholder to whom the event relates and (b) the Permitted
Transferees of the Shareholder to whom the event relates (such Shareholder and
all Permitted Transferees of such Shareholder pursuant to Section 2 are
sometimes collectively referred to as an "Affected Shareholder"):

                  (i) The receipt by a Shareholder (sometimes referred to as a
"Selling Shareholder") of a bona fide written offer, which it desires to accept,
acceptable to such Shareholder, to acquire all or some portion of such
Shareholder's Shares ("Offer").

                  (ii) The death of an individual Shareholder (sometimes
referred to as a "Deceased Shareholder") and the transfer of such Shareholder's
Shares by will or the laws of descent and distribution to a Person other than a
Permitted Transferee.

                  (iii) The commencement of bankruptcy, reorganization or
similar proceedings by a Shareholder, the commencement of bankruptcy or similar
proceedings against a Shareholder that are not terminated within 120 days after
commencement, the appointment of a bankruptcy or other judicial representative
for a Shareholder, such Shareholder's Shares or any material part of his or her
properties, provided that any such appointment that was involuntary is not
terminated within 120 days, the attachment of, execution against, levy upon or
other seizure of the Shares of a Shareholder (other than an attachment solely
for jurisdictional purposes) unless and only as long as the Company's counsel
determines that the same is being contested in good faith, an assignment by a
Shareholder for the benefit of creditors, whether or not such assignment
includes Shares, an admission by a Shareholder in writing of his or her
inability to pay such Shareholder's debts as they become due, or the attempted
rejection of this Agreement by a bankruptcy or other judicial representative who
succeeds to the Shares of a Shareholder.

                  (iv) The Transfer or attempted Transfer by a Shareholder or
any party acting on behalf of a Shareholder of any of his or her Shares in
violation of any provision of this Agreement, or any material breach by a
Shareholder of any provision of this Agreement.

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         2.2 Notice of Occurrence. Within 15 days after the occurrence of any
Triggering Event, the Affected Shareholder (or his or her personal
representative) shall give notice of the occurrence ("Notice of Occurrence") to
the Company and the other Shareholders. Failure to give Notice of Occurrence
shall neither prevent nor relieve any of the parties from exercising their
rights or satisfying their obligations under this Agreement, and any other party
to this Agreement may at any time give Notice of Occurrence on behalf of the
Affected Shareholder (or his or her legal or personal representative). If the
Affected Shareholder is a Selling Shareholder, the Notice of Occurrence shall
include a copy of the Offer, stating the name of the offeror ("Offeror") and the
price ("Offer Price") and other terms ("Offer Terms") of the Offer.

SECTION 3: OPTIONAL AND MANDATORY PURCHASE

         Upon the occurrence of any Triggering Events, the Affected
Shareholder's Shares shall be sold in accordance with this Section 3. For
purposes of this Section 3, "Remaining Shareholders" shall mean all Shareholders
except Numerex and the Affected Shareholders; and (ii) "Non-Affected
Shareholders" shall mean all Shareholders except for the Affected Shareholder.

         3.1 Option to Numerex. So long as Numerex owns Shares, prior to the
expiration of the First Call Period, as defined in Section 2.5 of the Purchase
Agreement, and in the event Numerex exercises the First Call, after the
expiration of the First Call Period, Numerex shall have the first option to
purchase all or any of the Shares owned by the Affected Shareholder on the date
the Triggering Event occurred, for the Purchase Price (as defined in Section 6)
and on the Payment Terms (as defined in Section 7), by giving notice, within
thirty (30) days after the date of the Notice of Occurrence, to the Affected
Shareholder (or his personal representative) and to the Remaining Shareholders
of the exercise of its option. The exercise of the option by Numerex shall be
effective only if the notices given by Numerex, the Company, if applicable, and
the Remaining Shareholders, if applicable, who exercised their options indicate
that Numerex, the Company and the Remaining Shareholders together intend to
purchase all of the Shares of the Affected Shareholder that are subject to the
Offer.

         3.2 Option to the Company. The Company shall have the option to
purchase all or any Shares of the Affected Shareholder that was not purchased by
Numerex in accordance with Section 3.1 ("Remaining Stock"), for the Purchase
Price and on the Payment Terms, by giving written notice, within forty-five (45)
days after the date of Notice of Occurrence, to the Affected Shareholder (or his
personal representative) and Numerex of the exercise of its option. The notice
shall state whether the Company intends to purchase all or only a part of the
Remaining Stock. The Company may only purchase, pursuant to this Section 3.2,
that number of shares of the Remaining Stock to the extent the Company has
sufficient capital surplus on retained earnings to permit it to lawfully
purchase and pay for any such shares. The exercise of the option by the Company
shall be effective only if the notices given by the Company and the Remaining
Shareholders, if applicable, who exercised their options indicate that the
Company and the Remaining Shareholders together intend to purchase all of the
Remaining Stock.

         3.3 Option to Remaining Shareholders. The Remaining Shareholders shall
have the option to purchase all or any of the Remaining Stock or by the Company
in accordance with Section 3.2, for the Purchase Price and on the Payment Terms,
by giving notice, within sixty (60) days after 


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the date of Notice of Occurrence, to the Affected Shareholder (or his personal
representative), Numerex and the Company of the exercise of this option. The
notice shall state whether such Remaining Shareholder intends to purchase all or
only a part of the Affected Shareholder's Shares that such holder is entitled to
purchase under this Section 3.3 and the number of the Affected Shareholder's
Shares to be purchased by him, if less than all. The exercise of the options by
the Remaining Shareholders shall be effective only if the notices given by the
Remaining Shareholders who exercised their options indicate that such the
Remaining Shareholders together intend to purchase all of the Remaining Stock.
Unless otherwise agreed upon in writing by all of the Remaining Shareholders,
each of the Remaining Shareholders shall have the option to purchase that
proportion, rounded to the nearest whole number to eliminate fractional shares,
of the Remaining Stock which the number of Shares held by him bears to the
number of Shares held by all Remaining Shareholders who exercised their options.
If any Remaining Shareholder does not exercise his option to purchase his full
proportionate share of the Remaining Stock, the other Remaining Shareholders may
purchase that proportion, rounded to the nearest whole number to eliminate
fractional shares, of the Shares not so purchased which the number of Shares
held by him bears to the number of Shares held by all Remaining Shareholders who
exercised their options, by giving written notice of the exercise of his option
to the Affected Shareholder, the other Remaining Shareholders, the Company and
Numerex within fifteen (15) days after the notice, pursuant to this Section 3.3,
is given.

         3.4 Intentionally Omitted.

         3.5 Purchase of All Shares. Unless otherwise agreed to by the Affected
Shareholder, all and not less than all of the Affected Shareholder's Shares must
be purchased pursuant to Sections 3.1, 3.2 or 3.3 hereof, as the case may be, in
order that there shall be a purchase of such Affected Shareholder's Shares
within the intent, scope and terms of this Agreement, except with regard to the
Triggering Events described in Sections 2.1(iii) and 2.1(iv) where all of the
Affected Shareholder's Shares are not purchased pursuant to Sections 3.1, 3.2 or
3.3.

         3.6 Closing on Optional Purchase. If Numerex, the Company and/or the
Remaining Shareholders shall have exercised their options to purchase the
Affected Shareholder's Shares pursuant to Sections 3.1, 3.2 or 3.3 hereof, the
closing of the purchase and sale contemplated by this Section 3.6 shall be held
at 10:00 a.m., on the earlier of the 90th day following the date Notice of
Occurrence is given or the 30th day after the exercise of the option that
results in options to purchase all (but not less than all) of the Affected
Shareholder's Shares being exercised, at the then principal office of the
Company, or at such other time and place as the parties shall mutually agree. At
the closing, the Affected Shareholder (or his personal representative) shall
deliver to the purchasers certificates for the Affected Shareholder's Shares,
duly endorsed for transfer, and the purchasers shall pay the Purchase Price to
the Selling Shareholder in accordance with the Payment Terms.

         3.7 Right to Transfer. If the Triggering Event is the event described
in Section 2.1(i) and all of the Affected Shareholder's Shares are not purchased
pursuant to Sections 3.1, 3.2, and 3.3 hereof, as the case may be, the Affected
Shareholder may, for a period of ninety (90) days following the final date for
acceptance under Section 3.1, 3.2 or 3.3 thereof, as the case may be, sell all
such Shares related to such Offer to the Offeror; provided, however, in the case
of an Offer, that no such Shares shall be sold to the Offeror upon any terms or
conditions more favorable to Offeror than the 


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Offer Terms as such Offer Terms were described in the Notice of Occurrence; and
provided further that such Offeror shall agree in writing to be bound by the
terms and conditions of this Agreement as if the Offeror were the Shareholder
who sold such Shares. If the Affected Shareholder wishes to sell such Shares on
terms and conditions more favorable to the Offeror than the Offer Terms or has
not sold such Shares on the Offer Terms within such ninety (90) day period, the
Affected Shareholder shall be obligated to make new offers and re-offers to
Numerex, the Company and the Remaining Shareholders in accordance with this
Section 3 before the Affected Shareholder shall be permitted to Transfer such
Affected Shareholder's Shares, or any part thereof, to any Person.

         3.8 Right to Participate in Sales. In the event Affected Shareholder(s)
shall be permitted to sell its Shares to an Offeror pursuant to Section 3.7
hereof and such Affected Shareholder(s) own at least 51% of the outstanding
Shares of the Company, the Affected Shareholder(s) shall give the Non-Affected
Shareholders written notice at least twenty (20) days prior to the consummation
of any and all such sales. Except as modified hereunder, each Non-Affected
Shareholder shall have the right, as a condition of such sale by the Affected
Shareholder(s), to sell to the Offeror, on the same terms and conditions as the
Affected Shareholder(s), that proportion, rounded to the nearest whole number to
eliminate fractional shares, of the Shares proposed to be sold by the Affected
Shareholder(s) which the number of Shares owned by such Non-Affected Shareholder
bears to the number of Shares owned by all Shareholders (including the Affected
Shareholder(s)), and the number of Shares that the Affected Shareholder(s) may
sell pursuant to such Offer shall be correspondingly reduced. Each Non-Affected
Shareholder desiring to participate in any such sale shall notify the Affected
Shareholder(s) of such intention within ten (10) days after notice is given in
accordance with the first sentence of this Section 3.8.

         3.9 Requirement to Participate in Sales. If (i) the Triggering Event
that occurs is described in Section 2.1(i) and the Offeror requires, as a
condition of the sale, that the Offeror acquire all of the Shares of the
Non-Affected Shareholders, and (ii) on the date of such Triggering Event,
Numerex owns 75% or more of the outstanding Shares and (iii) Numerex is
permitted to sell its Shares pursuant to Section 3.7, then the Non-Affected
Shareholders shall sell all of their Shares to the Offeror for not less than the
same price terms and other terms and conditions as those offered to Numerex.

         3.10 Effect of Sale to Third Party by Numerex. In the event that
Numerex sells all of its Shares to a third party prior to the third annual
anniversary of the date hereof, then the rights of Numerex terminate under this
Agreement, including, without limitation, the rights granted pursuant to
Sections 3.1, 3.9, 4.1, 4.3, 4.4, 5.1, 8.2, 8.4 and 8.5, and the obligations of
the parties as between Numerex and the Initial Shareholders under this Agreement
and the Purchase Agreement shall be null and void; provided however, (i) that
the representations, warranties, covenants and indemnifications contained in the
Purchase Agreement shall survive as provided therein and (ii) the Loan and
Security Agreement of even date herewith ("Loan Agreement") shall continue in
full force and effect pursuant to its terms.


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SECTION 4: FIRST REFUSAL ON SALE OF THE COMPANY.

         4.1 Right of First Refusal. If it is determined to conduct a Sale of
the Company (as defined below) pursuant to an Offer, which the Company desires
to accept, Numerex shall have the right ("Right of First Refusal") to purchase
the shares and/or assets, as stated in the Offer, for the purchase price and on
the payment terms consistent with the Offer, or at Fair Market Value determined
as of the Notice of Offer in the event that Fair Market Value would be a higher
purchase price than that of the Offer. Within fifteen (15) days of receipt of an
Offer by the Company or any Shareholder, the recipient shall send written notice
of the Offer to each Shareholder and Numerex ("Notice of Offer"). Numerex may
exercise its Right of First Refusal by giving notice to the Company within
thirty (30) days of receiving the Notice of Offer.

         4.2 Closing on First Refusal Exercise. If Numerex, shall have exercised
its Right of First Refusal pursuant to Section 4.1 hereof, the closing of the
purchase and sale contemplated by this Section 4.2 shall be held at 10:00 a.m.,
on the earlier of the 60th day following the date Notice of Offer is given or
the 30th day after the exercise of the Right of First Refusal, at the then
principal office of the Company, or at such other time and place as the parties
shall mutually agree. At the closing, the Company or the Selling Shareholders
shall deliver to Numerex evidence of the transfer of assets or stock, as the
case may be, certificates for the Affected Shareholder's Shares, duly endorsed
for transfer, and Numerex shall pay the purchase price to the selling
shareholders in accordance with the payment terms.

         4.3 Sale of the Company. "Sale of the Company" shall mean (i) sale of
all or substantially all of the assets of the Company, (ii) the merger or
consolidation with any other person or entity or (iii) a transaction or series
of transactions in which any person or entity or group of persons or entities
acquires, either directly or indirectly, securities representing more than 50%
of combined voting power of the Company's outstanding securities.

         4.4 Second Call.

                  (a) Second Call. If the First Call pursuant to Section 2.5 of
the Purchase Agreement is exercised, then for a period of ninety (90) days
commencing on the exercise of the First Call ("Second Call Period"), Numerex
shall have the right to purchase ("Second Call") that number of Shares ("Second
Call Shares") from the Initial Shareholders, on a pro rata basis, determined by
multiplying the total number of outstanding Shares as of the date the Second
Call Notice (as defined below) is given and after giving effect to the exercise
of the First Call, if any, by the Second Call Percentage (as defined below). The
"Second Call Percentage" shall be (i) the percentage ownership of Shares of the
Company by Numerex as of the date of the Second Call Notice after giving effect
to the exercise of the First Call, if any, subtracted from (ii) 51%. If,
immediately prior to the Second Call Period, Numerex owns 51% or more of the
outstanding shares of the Company, then the provisions of this Section 4.4(a)
shall be null and void, and of no further force or effect. Numerex may exercise
this Second Call by giving the Initial Shareholders written notice ("Second Call
Notice") at any time during the Second Call Period.

                  (b) Number of Shares; Purchase Price; Closing. Upon the giving
of the Second Call Notice, the parties shall promptly determine the number of
Second Call Shares. The purchase 

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price ("Second Call Purchase Price") shall be the lesser of (a) Four Million
Dollars ($4,000,000) or (b) 85% of the Fair Market Value (defined below);
provided however, for purposes of determining Fair Market Value under Section
6.3, (i) Numerex shall be deemed the "Affected Shareholder" and the Initial
Shareholders shall be deemed "Non-Affected Shareholders" and (ii) determination
of Fair Market Value shall be made as of the last day of the most recently
completed quarter preceding the exercise of the Second Call. The closing of the
Second Call shall be held at 10:00 a.m. within thirty (30) days after the Second
Call Notice is given, or as otherwise agreed by the parties. Upon the closing,
(i) the Company, the Initial Shareholders and the Management Shareholders (as
defined in the Purchase Agreement) shall make representations and warranties to
Numerex that are comparable to the representations and warranties contained in
Section 8.1 hereof; provided however, that such representations and warranties
shall be deemed to have been given as of the Second Call Notice or if such
representations and warranties relate to financial matters, such
representations, warranties shall be deemed to have been given as of the last
day of the most recently completed fiscal quarter. At the Closing, the Initial
Shareholders shall deliver certificates to Numerex, endorsed to Numerex, for the
Second Call Shares, transferring good and marketable title to such Second Call
Shares, free and clear of all Liens, and Numerex shall pay the Second Call
Purchase Price to the Initial Shareholders.

SECTION 5: OPTION FOR SHAREHOLDERS' SHARES

         5.1 Option for Initial Shareholders' Shares. If the First Call pursuant
to Section 2.5 of the Purchase Agreement is exercised by Numerex, then at any
time and from time to time during the thirty (30) days ("Option Period")
following each of the fourth, fifth and sixth annual anniversaries of the date
hereof ("Fourth Anniversary", "Fifth Anniversary" and "Sixth Anniversary",
respectively), Numerex shall have the right to purchase from the Initial
Shareholders ("Option for Initial Shareholders' Shares"), the number of Shares
as follows:

                  (a) during the Option Period following the Fourth Anniversary,
up to one-third of the Shares owned by each of the Initial Shareholders as of
the Fourth Anniversary;

                  (b) during the Option Period following the Fifth Anniversary,
any remaining number of Shares which were subject to option under paragraph (a)
above, but were not purchased, and after giving effect to such purchase, if any,
up to one-half of the Shares owned by the Initial Shareholders as of the date of
the Fifth Anniversary, and

                  (c) during the Option Period following the Sixth Anniversary,
up to all remaining Shares owned by the Shareholders.

         Numerex may exercise this Option for Initial Shareholders' Shares by
giving written notice ("Option Notice") to the Initial Shareholders at any time
during any Option Period. With respect to any exercise of the Option for Initial
Shareholders' Shares, each Initial Shareholder shall be required to sell that
proportion, rounded to the nearest whole number to eliminate fractional shares,
of the Shares owned by each such Initial Shareholder by the number of Shares
owned by all Initial Shareholders at the time the Option Notice is given from
time to time pursuant to this Section 5.1.


                                        8


<PAGE>



         5.2 Closing of Option Exercise. Upon the giving of any Option Notice,
the parties shall promptly determine the number of Shares subject to the
exercise of the Option for Initial Shareholders' Shares. The purchase price
("Option Purchase Price") shall be Fair Market Value, as calculated in
accordance with Section 6.3; provided however, for purposes of determining Fair
Market Value under this Section 5.2, (i) Numerex shall be deemed the "Affected
Shareholder" and the Initial Shareholders shall be deemed "Non-Affected
Shareholders" and (ii) determination of Fair Market Value shall be made as of
(i) June 30, 2001 with respect to an exercise under Section 5.1(a), (ii) June
30, 2002 with respect to an exercise under Section 5.1(b) and (iii) June 30,
2003 with respect to an exercise under Section 5.1(c). The closing of the
purchase and sale contemplated by Section 5.1 shall be held at 10:00 a.m., on a
date within thirty (30) days after the Option Notice is given, provided that in
the event the Option Purchase Price has not been determined within thirty (30)
days after the Option Notice is given, then the closing shall be held as soon as
reasonably practicable after determination of the Option Purchase Price, as
applicable. At the closing, any Initial Shareholder selling his Shares shall
deliver to Numerex certificates for the Shares owned by such Initial
Shareholder, duly endorsed for transfer, and Numerex shall pay the Option
Purchase Price.

         5.3 Negotiation Period. For the period of sixty (60) days following the
Sixth Anniversary ("Negotiation Period"), Numerex on the one hand or the Initial
Shareholders on the other hand may approach the other party with an offer to
purchase such other party's Shares or sell such party's Shares on terms as the
parties shall mutually agree. In the event Numerex or the Initial Shareholders
offer to purchase or sell Shares during the Negotiation Period, either party
may, upon their sole discretion, elect to withdraw from such negotiations at any
time.

         5.4 Forced Sale Option. In the event that (i) Shares remain owned by
the Initial Shareholders upon expiration of the Negotiation Period and (ii) an
initial public offering of the Company's Common Stock has not been consummated
by the Sixth Anniversary, then each of Numerex and the Initial Shareholders
shall have the option at any time during the sixty (60) day period commencing on
the day after the expiration of the Negotiation Period for the Sixth Anniversary
to cause a Forced Sale (as defined below) of the Company. A Forced Sale shall
occur when either Numerex or a majority in interest of the Initial Shareholders
consent in writing to such Forced Sale and deliver such consent to the Company
("Forced Sale Notice"). A "Forced Sale" shall mean an obligation of the Company
to use its best efforts, including, but not limited to the engagement of a
broker, to sell all of the Shares to a third-party purchaser. The Forced Sale
shall be made at the Fair Market Value, as such term is defined in Section 6.3;
provided however, that for purposes of determining Fair Market Value under this
Section 5.3, (i) if Numerex on the one hand or the Shareholders on the other
hand shall deliver a Forced Sale Notice, such party or parties shall be deemed
"Affected Shareholder(s)" and the other party or parties shall be deemed
"Non-Affected Shareholder(s)" and (ii) the determination of Fair Market Value
shall be made as of the time of the Forced Sale. Once written consents are
obtained by the Company to cause a Forced Sale as provided hereunder, all of the
Shareholders hereto agree to sell their Shares in the manner and on the terms
and conditions described herein.

                                        9


<PAGE>



SECTION 6: PURCHASE AND OPTION PRICE

         6.1 Third Party Offers. In the event that a Triggering Event described
in Section 2.1(i) takes place, the Purchase Price, for purposes of Section 3,
shall be the Offer Price in writing to the Affected Shareholder by such third
party.

         6.2 Other Triggering Events. In the event that a Triggering Event takes
place other than that described in Section 2.1(i), the Purchase Price shall be
Fair Market Value, as determined in Section 6.3 hereof.

         6.3 Appraisal For Fair Market Value.

                  (a) Fair Market Value. "Fair Market Value" shall mean the fair
market value of the Company as a going concern, assuming that the Company is 
sold pursuant to a sale of capital stock.

                           (i) Fair Market Value shall be determined by the 
agreement of the Non-Affected Shareholders and the Affected Shareholder(s),
through a majority vote the Shares of each of the Affected Shareholders and the
Non-Affected Shareholder(s), in each case acting as an independent class, within
ten (10) days of the date on which any party notifies all Shareholders that this
Agreement then requires that "Fair Market Value" be determined, specifically
referring to the paragraph and subparagraphs of this Agreement that require such
determination.

                           (ii) If the Affected Shareholders and the 
Non-Affected Shareholders(s) shall not so agree on the amount of the Fair Market
Value within such ten-day period, then within ten (10) days after such initial
ten-day period, each of the Non-Affected Shareholders and the Affected
Shareholder(s), acting in each case as an independent class, by a majority vote
of the Shares each of the Affected Shareholders and the Non-Affected
Shareholder(s), will appoint a Qualified Appraisal Firm (as hereinafter defined)
to make the determination, within thirty (30) days of such appointment, of the
proposed fair market value of the Company as a going concern and the average of
the determinations by such appraisal firms of the proposed fair market value of
the Company as a going concern (the "Proposed Value") will be the Fair Market
Value; provided, however, that if the difference between such Proposed Values is
more than 15% of the amount of the lower Proposed Value, then the two appraisal
firms will appoint a third appraisal firm to determine, within thirty (30) days
of its appointment, a Proposed Value and the Fair Market Value shall be equal to
the average of all three Proposed Values; provided, further, that if the
Proposed Value of the appraisal firms appointed by either the Non-Affected
Shareholders or the Affected Shareholder(s) shall vary by more than 15% from the
Proposed Value determined by the third appraisal firm, such varying Proposed
Value shall not be included in such average in determining Fair Market Value. If
only two appraisal firms are appointed, each of the Non-Affected Shareholder and
the Affected Shareholder(s), in each case, as an independent class, shall pay
the cost of their respectively appointed appraisal firm and if a third appraisal
firm is appointed, each of the Non-Affected Shareholders (pro rata based on
their respective ownership of Shares owned by Non-Affected Stockholders), in
each case, as an independent class, shall pay one-half the cost of the third
appraisal firm. In connection with any determination of Fair Market Value, (A) a
majority vote of the Shares of the Non-Affected Shareholders (or in the case of
a Forced Sale, either Numerex or a majority of the Initial Shareholders) shall
have the right to request an audit of the financial statements for the


                                       10


<PAGE>



Company's applicable "stub" period (the "Stub Audit"), at the Company's expense,
if such determination of Fair Market Value shall be made more than ninety (90)
days after the end of the Company's fiscal year, and (B) any revenues or costs
associated with business transactions between the Company and the Affected
Shareholder(s) or any affiliates of the Affected Shareholder(s) shall be
restated by the appraisal firm(s), to the extent necessary, to reflect the
revenues or costs which would have recognized had such transactions been on an
arm's length basis (the "Revenue Restatement"). Notwithstanding anything
contained herein to the contrary, any required periods for the determination of
Fair Market Value shall be extended to the extent necessary to permit the
completion of any Stub Audit requested to be made under the terms of this
Agreement and any Stub Audit and/or Revenue Restatement shall be considered by
the parties and the relevant appraisal firm(s) in determining Fair Market Value.
If Fair Market Value is required, under the terms of this Agreement, to be
stated on a per Share basis, the calculation thereof shall be based on the total
number of shares of Common Stock outstanding, assuming exercise of all the
outstanding options and receipt of the aggregate maximum number of shares of
Common Stock issued, delivered or exchanged therefore or thereunder.

                  (b) Qualified Appraisal Firm. "Qualified Appraisal Firm" means
any firm engaged in business valuation services, but excluding any firm which
received more than $15,000 in fees during the preceding 24 calendar months from
any party hereto.

                  (c) Inspection. The appraisal firms engaged for the purpose of
providing an appraisal under Section 6.3(a) hereof ("Appraisers") shall have the
right, during normal business hours, to (i) inspect and make copies of all
documents and other information relating to the Company or its business,
including internal accountants' work papers, (ii) inspect all properties and
assets used by the Company in its business, and (iii) consult with the officers,
employees, accountants, counsel and advisors of the Company, for the purpose of
rendering their appraisals, provided such Appraisers shall have entered into a
confidentiality agreement with the Company pursuant to which the Appraisers
agree to maintain the confidentiality of all confidential and proprietary
information obtained by the appraisers in performing their appraisals.

                  (d) Disclosure. Whenever the Fair Market Value must be
determined under this Agreement, the Company and the Shareholder or Shareholders
selling his or their Shares shall disclose in writing to the purchaser or
purchasers of those Shares and the appraisers referred to in Section 6.3 all
facts of which it, he or they have knowledge and which may affect the
determination of Fair Market Value.

SECTION 7: PAYMENT TERMS

         As used in this Agreement, "Payment Terms" means, except as otherwise
agreed to by the selling and purchasing Shareholders, the Purchase Price that
shall be paid on the Closing Date via certified check or wire transfer of funds,
or in Numerex Common Stock, as the parties hereto may mutually agree.

                                                    
                                       11


<PAGE>



SECTION 8: OTHER PROVISIONS

         8.1 Representations and Warranties. Each of the Initial Shareholders
hereby severally represents and warrants to, and covenants and agrees with,
Numerex that:

                  (a) Ownership of Shares. Such Initial Shareholder owns of
record and beneficially the number of Shares set forth opposite the name of such
Initial Shareholder on Exhibit A hereto, and as of the respective Closing Dates
such Initial Shareholder will have, good and marketable title to such Shares,
free and clear of all Liens.

                  (b) Execution and Delivery. All consents, approvals,
authorizations and order necessary for the execution, delivery and performance
by such Initial Shareholder of this Agreement have been duly and lawfully
obtained, and such Initial Shareholder has, and at the Closings will have, full
right, power, authority and capacity to execute, deliver and perform this
Agreement. This Agreement has been duly executed and delivered by such Initial
Shareholder and constitutes a legal, valid and binding agreement of such Initial
Shareholder enforceable against such Initial Shareholder in accordance with its
terms, except to the extent that enforceability may be limited by bankruptcy,
insolvency and other similar or equitable principles affecting the enforcement
or creditors' rights generally.

                  (c) No Conflicts. The execution, delivery and performance of
this Agreement and the consummation of the transactions contemplated hereby will
not conflict with or result in a breach or violation of any term or provisions
of, or (with or without notice or passage of time, or both) constitute a default
under, any indenture, mortgage, deed of trust, trust (constructive and other),
loan agreement or other agreement or instrument to which such Initial
Shareholder is a party or by which Initial Shareholder or such Initial
Shareholder's Shares are bound, or violate any Legal Requirement applicable to
or binding upon such Initial Shareholder.

                  (d) No Brokers. No broker, finder or similar agent has been
employed by or on behalf of such Initial Shareholder in connection with this
Agreement or the transactions contemplated hereby, and such Initial Shareholder
has not entered into any agreement or understanding of any kind with any person
or entity for the payment of any brokerage commission, finder's fee or any
similar compensation in connection with this Agreement or the transactions
contemplated hereby, which such commission, fee or any similar compensation
associated therewith shall be paid by the Initial Shareholders.

         8.2 Special Matters. For so long as Numerex on the one hand, or the
Initial Shareholders on the other hand, or their successors, hold in the
aggregate not less than 15% of the Shares outstanding ("Minority Shareholder"),
such party or parties shall not take any action which is intended to have a
material adverse effect on the Shares, without first obtaining the affirmative
vote of (i) a majority of the Shares held by the Initial Shareholders, if the
Initial Shareholders constitute a Minority Shareholder or (ii) Numerex, if
Numerex is a Minority Shareholder. Without limiting the generality of the
foregoing, any of the following actions shall require such affirmative vote:

                  (a) amend the Company's Bylaws or Articles of Incorporation;


                                       12


<PAGE>



                  (b) change the nature or scope of the business of the Company
with regard to wireless transport of alarm signals; or

                  (c) liquidate or dissolve the Company, except where such
liquidation or dissolution is incident to a sale of the Company, or as otherwise
permitted under this Agreement.

         8.3 Sale or Transfer of Shares by Initial Shareholders. Upon the
occurrence of any event hereunder involving a sale or transfer of shares from a
Shareholder, at the closing of such sale or transfer, such Shareholder shall
make representations and warranties to the purchaser that are comparable to the
representations and warranties contained in Section 8.1 hereof. Further, at such
closing, the selling party shall transfer good and marketable title to such
Shares, free and clear of all Liens.

         8.4 Board of Directors. The Shareholders agree to vote all Shares now
owned or hereafter acquired or controlled by them, and otherwise use their best
efforts as Shareholders of the Company, (i) to set the number of directors of
the Company at five, and (ii) to elect as directors those persons that are
nominated by Numerex on the one hand, and the Initial Shareholders on the other
hand, in a proportion equal to, or as near as equal as possible, to the number
of Shares held by (x) Numerex and (y) all of the other Shareholders, each of (x)
and (y) being compared to the total number of Shares outstanding, at the time of
such election; provided however, (a) that the number of directors designated by
Numerex shall be no less than one and (b) at all times after the Initial
Shareholders own less than 40% but greater than 15% of the Shares, they shall be
entitled to two directors who shall be nominated by a majority of the Initial
Shareholders and reasonably approved by Numerex. All calculations hereunder
shall be (i) based solely upon the Shares which are outstanding and (ii) rounded
to the nearest whole director seat, in the event that a fractional computation
results.

         8.5 Future Capital Raising. In the event that the Company requires
financing in addition to the financing ("Additional Financing") contemplated by
the Purchase Agreement, Numerex shall have the right, but not the obligation, to
provide such Additional Financing on terms, negotiated by Numerex and the
Company in good faith, which are no less favorable to the Company than the
Company could obtain from alternative financing sources.

         8.6 Failure to Transfer Shares. If any Shareholder whose Shares are
subject to purchase hereunder does not assign and transfer such Shares to a
purchaser as required hereunder, such Shares shall be deemed assigned and
transferred to the purchaser. The Company, upon receipt of written notice, shall
mark its records to indicate that the certificates have been canceled and shall,
if necessary, issue new certificates to the purchaser. Each Shareholder hereby
gives the Secretary of the Company an irrevocable power of attorney to make
assignments and transfers on the Company's books on behalf of such Shareholder
in accordance with the foregoing.

         8.7 Endorsement Upon Share Certificate. Each Shareholder acknowledges
that all certificates for Shares shall bear the following legend in addition to
any other legend that may be required by law or agreement:

                  "The shares represented by this certificate may not be
                  transferred, hypothecated, pledged or otherwise disposed of,
                  except in compliance 

                                       13


<PAGE>



                  with the Agreement, dated July ___, 1997 between the Company
                  and its Shareholders, copies of which are on file in the
                  office of the Secretary of the Company."

         8.8 Further Assurances. Each Shareholder agrees that he shall promptly
execute and deliver all such further agreements, certificates, instruments and
documents, and perform such further actions, as the Company or any other
Shareholder may reasonably request in order to fully carry out the purposes and
intent of this Agreement.

         8.9 Joinder of Spouse. Each Shareholder who is a natural person shall
cause such Shareholder's spouse to execute and deliver the Joinder of Spouse
attached hereto as Exhibit B, approving this Agreement and waiving any and all
rights such spouse may have relating to this Agreement or such Shareholder's
Shares.

         8.10 Inconsistent Agreements. No Shareholder shall enter into any
agreement or arrangement that conflicts with, or is inconsistent with, any of
the terms or conditions of this Agreement.

         8.11 Notices. All notices and other communications under or in
connection with this Agreement shall be in writing and shall be deemed given (a)
if delivered personally (including by overnight express or messenger), upon
delivery, (b) if delivered by registered or certified mail (return receipt
requested), upon the earlier of actual delivery or three days after being
mailed, or (c) if given by telecopy, upon confirmation of transmission by
telecopy, in each case to the parties at the following addresses:

                  (a)      If to Numerex, addressed to:

                           Numerex Corp.
                           2360 Maryland Road
                           Willow Grove, PA 19090
                           Attention: John J. Reis
                           Telecopy: (610) 892-0725

                           With a copy to:

                           Blank Rome Comisky & McCauley
                           1200 Four Penn Center Plaza
                           Philadelphia, PA  19103
                           Attention: Barry H. Genkin, Esquire
                           Telecopy: (215) 569-5555


                                       14


<PAGE>



                  (b)      If to the Company, address to:

                           Uplink Security, Inc.
                           1395 South Marietta Parkway
                           Building 200, Suite 228
                           Marietta, GA 30067
                           Attention: John K. Collings, III
                           Telecopy: (770) 429-5533

                           With a copy to:
                           Wagner, Johnston & Rosenthal, P.C.
                           3343 Peachtree Road, N.E.
                           Atlanta Financial Center
                           Suite 800, East Tower
                           Atlanta, GA 30326-1044
                           Attention: Craig A. Wagner, Esquire
                           Telecopy: (404) 261-6779

                  (c)      If to any Initial Shareholder, to the address set
                           forth below such Initial Shareholder's name on
                           Exhibit A, attached hereto.

         8.12 Settlement of Disputes. Other than for claims in equity, any
claims, controversies, demands, disputes, or differences between or among the
parties hereto or any persons bound hereby shall be submitted to and settled by
arbitration in the City of Philadelphia, Pennsylvania, before a single
arbitrator chose by mutual agreement of the disputing parties who shall be
knowledgeable in the field of business law and such arbitration shall be before
and in accordance with the rules then obtaining of the American Arbitration
Association. The parties agree to bear joint and equal responsibility for all
fees, abide by any decision rendered as final and binding and waive the right to
submit the dispute to a jury trial. Judgment upon any award may be entered in
any court of competent jurisdiction. Notwithstanding any of the foregoing,
nothing herein contained shall preclude a party hereto from resort to judicial
process if such party, in its or his sole discretion, chooses to seek any form
of equitable or injunctive relief.

         8.13 Amendment. This Agreement may be amended, modified or supplemented
by the parties hereto, provided that any such amendment, modification or
supplement shall be in writing and signed by the parties hereto and in a form
consistent with Exhibit C attached hereto.

         8.14 Waiver. No waiver with respect to this Agreement shall be
enforceable unless in writing and signed by the party against whom enforcement
is sought. Except as otherwise expressly provided herein, no failure to
exercise, delay in exercising, or single or partial exercise of any right, power
or remedy by any party, and no course of dealing between or among any of the
parties, shall constitute a waiver of, or shall preclude any other or further
exercise of, any right, power or remedy.

         8.15 Termination of Prior Agreements. The parties hereby terminate,
effective immediately, any and all existing buy-sell, shareholders' or similar
agreements to which any or all of them are parties to the extent any such
agreement governs any Shares.


                                       15


<PAGE>


         8.16 Entire Understanding. This Agreement states the entire
understanding among the parties with respect to the subject matter hereof, and
supersedes all prior oral and written communications and agreements, and all
contemporaneous oral communications and agreements, with respect to the subject
matter hereof.

         8.17 Parties In Interest. This Agreement shall bind, benefit and be
enforceable by and against each party hereto and its successors, assigns, heirs
and legal and personal representatives. No party shall in any manner assign any
of its or his rights or obligations under this Agreement, except as permitted by
this Agreement, without the express prior written consent of the other parties.

         8.18 Severability. If any provision of this Agreement is construed to
be invalid, illegal or unenforceable, then the remaining provisions hereof shall
not be affected thereby and shall be enforceable without regard thereto.

         8.19 Counterparts. This Agreement may be executed in any number of
counterparts, each of which when so executed and delivered shall constitute an
original hereof, and it shall not be necessary in making proof of this Agreement
to produce or account for more than one original counterpart hereof.

         8.20 No Third Party Beneficiaries. No provision of this Agreement is
intended to or shall be construed to grant or confer any right to enforce this
Agreement, or any remedy for breach of this Agreement, to or upon any Person
other than the parties hereto.

         8.21 Section Headings. Section and subsection headings in this
Agreement are for convenience of reference only, do not constitute a part of
this Agreement, and shall not affect its interpretation.

         8.22 References. All words used in this Agreement shall be construed to
be of such number and gender as the context requires or permits. Unless a
particular context clearly provides otherwise, the words "hereof" and
"hereunder" and similar references refer to this Agreement in its entirety and
not to any specific Section or subsection hereof. For the purpose of this
Agreement, "including means" including without limitation.

         8.23 Controlling Law. This Agreement is made under, and shall be
construed and enforced in accordance with, the laws of the Commonwealth of
Pennsylvania applicable to agreements made and to be performed solely therein,
without giving effect to principles of conflicts of law.

         8.24 Jurisdiction and Process. Each of the parties (a) irrevocably
consents to the exclusive jurisdiction of the Courts of Common Pleas of
Philadelphia County, Pennsylvania, or the United States District Court for the
Eastern District of Pennsylvania, in any and all actions between or among any of
the parties, whether arising hereunder or otherwise, and (b) irrevocably
consents to service of process by first class certified mail, return receipt
requested, postage prepaid, to the address as which such party is to receive
notice in accordance with Section 7.7.


                                       16


<PAGE>



         8.25 Certain Definitions.

              (a) "Person" means any individual, sole proprietorship, joint
venture, partnership, corporation, association, cooperative, trust, estate,
government body, administrative agency, regulatory authority, or other entity of
any nature.

              (b) "Transfer" means any sale, exchange, gift, bequest, pledge,
hypothecation, encumbrance, descent or distribution pursuant to any intestacy
laws or other operation of law, or any other direct or indirect disposition of
Shares which would change the legal or beneficial ownership thereof, including,
without limitation, any transaction that creates any form of joint or common
ownership in Shares between a Shareholder and one or more Persons (whether or
not that other Person is the spouse of such Shareholder).

              (c) The terms "Closing Date," "Legal Requirement" and
"Permits" shall have the meanings given to those terms in the Stock Purchase
Agreement.

         8.26 Expenses. All costs and expenses (including, without limitation,
all legal fees and expenses and fees and expenses of any brokers, finders or
similar agents) incurred in connection with this Agreement and the transactions
contemplated hereby shall be paid by the party incurring the same.


                          *            *            *



                                       17


<PAGE>



         IN WITNESS WHEREOF, the parties have executed this Agreement or have
caused this Agreement to be executed on their behalf by their duly authorized
officers as of the date first stated above.

NUMEREX CORP.                           UPLINK SECURITY, INC.

By: /s/ John J. Reis                    By: /s/ John K. Collings, III
    -----------------------------           ------------------------------------
        John J. Reis, President                 John K. Collings, III, President

SHAREHOLDERS:

ABN AMRO INVESTMENTS
(IRELAND) LIMITED

By: /s/ Authorized Officer              /s/ David G. Tattersall
    -----------------------------       ----------------------------------------
    Name:                               DAVID G. TATTERSALL
    Title:

AIB CUSTODIAL NOMINEES LIMITED

By: /s/ Authorized Officer              /s/ Peter J. Quinn
    -----------------------------       ----------------------------------------
    Name:                               PETER J. QUINN
    Title:

COMOLINK TECHNOLOGY LTD.

By: /s/ Authorized Officer
    -----------------------------       ----------------------------------------
    Name:                               PAMELA van de POLL
    Title:

                                        /s/ Malcolm Lewis
                                        ----------------------------------------
                                        MALCOLM LEWIS


                                       18


<PAGE>





SHAREHOLDERS (CONT'D):

                                        /s/ Ian R. Jackson
                                        ----------------------------------------
                                        IAN R. JACKSON

                                        /s/ George S. Watson
                                        ----------------------------------------
                                        GEORGE S. WATSON

                                        /s/ John K. Collings, III
                                        ----------------------------------------
                                        JOHN K. COLLINGS, III

                                        /s/ Roy G. Thurston
                                        ----------------------------------------
                                        ROY G. THURSTON

                                        /s/ Victor L. Slider
                                        ----------------------------------------
                                        VICTOR L. SLIDER

                                        /s/ Thomas Murray
                                        ----------------------------------------
                                        THOMAS MURRAY

                                        /s/ Robert A. Hay
                                        ----------------------------------------
                                        ROBERT A. HAY


                                       19


<PAGE>



<TABLE>
<CAPTION>

                                    EXHIBIT A

                             MANAGEMENT SHAREHOLDERS

Shareholder                   Shares of Common Stock                 Address
-----------                   ----------------------                 -------

<S>                                   <C>                            <C>          
David G. Tattersall                   29,942                         9 Baily Green
                                                                     Howth
                                                                     Co. Dublin, Ireland

Peter J. Quinn                         9,491                         2 Stradbrook Grove
                                                                     Blackrock
                                                                     Co. Dublin, Ireland

John K. Collings, III                 14,686                         5347 St. Martin's Court
                                                                     Mableton, GA 30064
</TABLE>



                                       20


<PAGE>