Master Lease - Racal-Datacom Inc. and Concentric Research Corp.


                                 MASTER LEASE

                            AGREEMENT NUMBER CON 01C

     This Agreement ('Agreement') is entered into this 4th day of August, 1994
by and between Racal-Datacom, Inc., a Delaware corporation, (hereinafter
referred to as 'Lessor'), having its principal place of business located at 1601
North Harrison Parkway, Sunrise, Florida 33323-2899 and Concentric Research
Corporation, a Florida corporation (hereinafter referred to as 'Lessee') having
its principal place of business at 400 Forty-First Street, Bay City, MI 48708.


                                WITNESSETH THAT

     WHEREAS, Lessor is the manufacturer of data communication products which
are composed of hardware (hereinafter referred to as 'Equipment') and software
which is defined as a set of processor instructions that can be ported into a
processor and executed to provide a defined functionality (hereinafter referred
to as 'Software'); and

     WHEREAS, Lessee is desirous of leasing such Equipment or Software from
Lessor for use with Lessee's communications network; and

     WHEREAS, both parties are desirous of establishing the terms and conditions
which shall govern all orders issued pursuant to this Agreement.

     NOW THEREFORE, in consideration of the covenants, premises and mutual
agreements contained herein, the parties do hereby agree as follows:

                                    PURPOSE
                                    -------

     The purpose of this Agreement is to set forth the terms and conditions
pursuant to which Lessee may submit orders (as defined in Article III) to
Lessor, All Orders must be accepted by Lessor at its headquarters, Sunrise,
Florida.

 
II.  Term of Agreement
     -----------------

     This Agreement shall commence upon the date first written above and shall
continue for a term of twelve (12) months.  The Agreement shall govern all
Orders placed hereunder provided such orders are received by Lessor within
twelve (12) months and the Equipment and Software ordered is installed within
fourteen (14) months, both of said periods beginning upon the date of
commencement of this Agreement.  Thereafter, this Agreement shall automatically
renew itself in twelve (12) month increments unless either party notifies the
other of its decision to terminate this Agreement by providing the other party
sixty (60) days written notice prior to the expiration of the period then in
effect.

     Notwithstanding that this Agreement may terminate prior to the expiration
of an individual Orders term, it is expressly agreed that any Order issued
pursuant to this Agreement shall continue to be in full force and effect until
the expiration of such Orders stated minimum term, and shall continue to be
governed by the terms of this Agreement.

III. Ordering Procedure
     ------------------

     Lessee shall issue Orders to Lessor on Lessors order form or Lessee's order
form.  At a minimum, such Orders shall include the following information:

     a.  Description of Equipment to be leased and Software to be licensed.
     b.  Quantity of each item of Equipment or Software.
     c.  Monthly lease rate, license fee and lease term for each item.
     d.  Unit installation price for each item (if applicable).
     e.  Unit purchase price for each item.
     f.  Requested delivery date.
     g.  Shipping location and Lessee prime contact at shipping location.
     h.  Billing address and billing contact.
     i.  Required Lessor services such as standard handling, installation,
maintenance, training and engineering costs (if applicable), and their
respective charges.

     Lessor will acknowledge acceptance or rejection of orders within fifteen
(15) days after receipt of the order at Lessor's principal place of business,
Sunrise, Florida.  Once accepted, the order is noncancelable.  If Lessor
proposes a delivery schedule different from the schedule requested by Lessee,
Lessee must notify Lessor of its rejection of such alternate delivery schedule
within fifteen (15) days after mailing of such notification by Lessor, or the
Lessor acknowledged shipping date shall be deemed to be accepted by Lessee.

IV.  Commencement and Term of Order
     ------------------------------

     An Order for an individual unit of Equipment or Software shall be binding
from the date it is accepted by Lessor.  Commencement of term and monthly rental
as to each unit of Equipment and Software shall commence fifteen (15) days after
the deployment of CRC's Wide Area Network, the

                                      -2-

 
Lessee, an AT&T , whichever first occurs (the 'Commencement Date').  Monthly
rental for a diagnostic controller applicable, shall commence thirty (30) days
following the Deployment Date by Lessor.  The lease term shall continue for the
number of full months set forth on the Order, commencing on the first day of the
month following the Commencement Date.

     Network deployment shall mean that Lessors Equipment which is deployed at
the available sites set forth on the deployment schedule agreed to by the
parties and attached hereto as Exhibit 4 is operational.  Operational shall mean
that the Lessor supplied Equipment is functioning in accordance with the
parameters set forth in Exhibit 3 notwithstanding the operational capability or
lack thereof of any other equipment or services provided by any other party
relating thereto or in connection therewith.

     Lessee agrees to complete a Certificate of Acceptance for each unit of
Equipment and Software shipped under this Agreement.  Such Certificate of
Acceptance shall be forwarded to Lessor within seven days of the Commencement
Date set forth above and shall indicate that: (i) Lessee has fully inspected the
Equipment and Software; (ii) Lessee has acknowledged that the Equipment and
Software is in good condition and repair; and, (iii) Lessee agrees that the
Equipment and Software meets their respective Lessor published specifications.
Failure of Lessee to provide a Certificate of Acceptance shall not affect any
Lessee obligations set forth in this Agreement, including but not limited
to payment.

     The Order may be renewed for an extended term in accordance with Lessor's
policies in effect at time of the Order's expiration.  Either party must notify
the other in writing at least sixty (60) days prior to expiration of the lease
term of its decision to either renew the Order or terminate any or all of the
Equipment and Software leased thereunder.  Without such notice, the Order shall
continue at the same rate and under the same conditions until such sixty (60)
day notice is given by either party.

     Notwithstanding that the lease contemplates the lease term set forth on the
face of the Order, it is agreed that if Lessee is a governmental entity and is
fiscally funded, continuance of the Order for said term is dependent upon the
annual legislative approval of funding.  Lessee agrees to utilize its best
efforts to assure funding for the continuance of the Order; however, if fiscal
funding is denied, the Lessee may terminate the lease by providing Lessor with
written notice as outlined in this provision.

V.   Return of Equipment and Software
     --------------------------------

     Upon termination by expiration or otherwise of each Order, Lessee shall, at
Lessee's expense, disconnect the Equipment or de-install the Software and allow
Lessor to enter Lessee's premises to pack and ship the Equipment and Software.
Such Equipment and Software returned to Lessor shall be in the same condition as
delivered by Lessor, reasonable wear and tear excepted and capable of meeting
all recertification requirements.  If Lessor is not allowed to remove the
Equipment and Software as noted within two (2) weeks after the effective date of
Lessee's notice of termination, such termination shall be void, and the lease
shall continue in full force and effect until new notice is given followed by
removal of Equipment and Software in accordance with this paragraph.

                                      -3-

 
VI.  Payment
     -------

     The Equipment and Software is to be leased for the term set forth on the
Order and is non-cancelable.  Lessee shall pay to Lessor, the monthly rate set
forth on the Order during each month of the term of such Order.  Lessors initial
                                                                 ---------------
payment due hereunder shall be paid on the fifteenth (15th) day following the
-----------------------------------------------------------------------------
Commencement Date.  The remainder of the rental payments for the lease term
---------------------------------------------------------------------------
shall be due and payable on the first day of each calendar month thereafter.
---------------------------------------------------------------------------  
The Equipment furnished hereunder may be new, remanufactured or contain used
components at Lessor's option.  If the Commencement Date of each unit of
Equipment leased hereunder is other than the first day of each month, the first
payment due hereunder shall be equal to one thirtieth of the monthly rate set
forth on the Order for each day from and including the Commencement Date through
and including the last day of the month prior to the beginning of the term and
the monthly rate for the full initial month. Lessor reserves the right to impose
a late payment charge of one and one-half percent (1-1/2%) per month, but not in
excess of the lawful maximum, on any past due balance in the event Lessee shall
fail to pay any charges within fifteen (15) days after same are due, and Lessee
agrees to pay same.  If such rate exceeds the amount authorized by law in the
jurisdiction in which the Equipment or Software is located, interest shall be
computed at the maximum legal rate at that location.  Payments shall be made to
the Lessor address stated on each invoice.  Charges for Lessor services (such as
standard handling, installation, engineering costs (if applicable) and training)
shall also be at the prevailing rates at time of order.  Any applicable taxes
will be invoiced.

VII. Assignment
     ----------

     Without Lessor's prior written consent, Lessee shall not (a) assign,
transfer, pledge, hypothecate, or otherwise dispose of all or any part of
Lessee's right, title or interest in and to this Agreement, any Order, the
Equipment or Software, or (b) sublet or lend the Equipment or Software or permit
it to be used by anyone other than Lessee or Lessee's employees.  Lessor may
sell or assign or grant a security interest or participation in all or any part
of Lessor's right, title or interest in and to this Agreement, any Order and the
Equipment or Software without notice to Lessee, and Lessor's assignee or secured
party may then re-assign such interest without notice to Lessee.  Lessee agrees
that any such assignment or re-assignment shall not change Lessee's or Lessors
                                                                    ----------
duties or obligations under this Agreement or any Order and Lessee hereby
consents to any such assignment or re-assignment.  Each such assignee and/or
secured party shall have all the rights but none of the obligations of Lessor
under such Order unless Lessee is otherwise notified by Lessor.  Lessee shall
recognize such assignments and/or security agreements and agrees that upon
notice of such assignment it shall pay directly to assignee (unless otherwise
directed by assignee) without abatement, deduction or setoff all amounts which
become due hereunder and further agrees that it will not assert against assignee
any defense, counterclaim or setoff for any reason whatsoever in any action for
lease payments or possession brought by assignee.  Upon such assignment and
except as may otherwise be provided therein, all references in this Agreement to
Lessor shall include Assignee.

                                      -4-

 
VIII. Net Lease
      ---------

     Lessee and Lessor acknowledge and agree that each Order constitutes a net
lease with all costs, expenses and liability associated with the Equipment or
Software or its Order to be borne by Lessee unless expressly agreed to the
contrary in writing by Lessor.  Subject to Lessee's right to terminate
hereunder, in the event an assignment of this lease by the Lessor, the Lessee's
obligations to pay all monthly rates and any and all amounts payable by Lessee
under any Order shall be to the assignee, absolute and unconditional and shall
not be subject to any abatement, reduction, set-off, defense, counterclaim,
interruption, deferment or recoupment for any reason whatsoever and that such
payments shall by and continue to be payable in all events.

IX.  Representations and Warranties of Lessee
     ----------------------------------------

     Lessee hereby represents, warrants and covenants that, with respect to this
Agreement and each Order executed hereunder

     a.  The execution, delivery and performance thereof by the Lessee have been
duly authorized by all necessary corporate action.

     b.  The individual executing such was duly authorized to do so.

     c.  This Agreement and each Order constitute legal, valid and binding
agreements of the Lessee enforceable in accordance with their respective terms.

     d.  The Equipment and Software is personal property and when subjected to
use by the Lessee will not be or become fixtures under applicable law.

     e.  Lessee shall furnish, upon request by Lessor, audited financial
statements for the most recent period.

X.   Title and Location
     ------------------

     Nothing contained in any Order shall give or convey to Lessee any right,
title or interest in or to the Equipment or Software, except as a Lessee as set
forth therein and Lessee represents and agrees that Lessee shall hold the
Equipment and Software subject and subordinate to the rights of Lessor, and
Lessee shall furnish Lessor with such documentation as Lessor shall reasonably
require with respect thereto.

     Lessor is hereby authorized by Lessee, at Lessee's expense, to cause this
Agreement, any Order, or any statement or other instrument in respect of any
Order as may be required or permitted by law showing the interest of Lessor, in
the Equipment or Software to be filed and Lessee appoints Lessor as its
attorney-in-fact to execute and file on behalf of Lessee, at Lessee's expense,
any UCC financing statements and amendments Lessor deems advisable to secure the
interests of Lessor. Without limiting the foregoing, Lessee shall execute one or
more financing statements, in form and

                                      -5-

 
substance satisfactory to Lessor, covering all Equipment or Software leased
to Lessee pursuant to this Agreement.  The parties have agreed that a
photographic copy or other reproduction of this Agreement, either together with
or in lieu of an appropriate form under the UCC, is sufficient as a financing
statement for purposes of filing and perfection under the UCC.  Any filing of
such financing statements or any public recordation of this Agreement is
intended by the parties solely to protect the interest to Lessor and Lessee, and
no such filing or recordation shall in any manner imply or be construed as
implying that the relationship of Lessor to Lessee with respect to this
Agreement or to the Equipment or Software is anything other than that of a
personal property Lessor to a personal property Lessee.

     Lessee shall request Lessors consent, in writing, at least fifteen (15)
days before Lessee intends to move any of the Equipment or Software from its
original 'ship to' location.  Lessors response to such request shall be in
writing and shall not be unreasonably withheld.  Lessee agrees to provide Lessor
with fifteen (15) days written notice of its intention to change its name or
corporate identity or structure, by merger, consolidation, reorganization or
otherwise.  In the event Lessee fails to comply with this paragraph or the
preceding paragraph, Lessee agrees to indemnify Lessor for any losses or damages
Lessor incurs thereby.

     Lessee shall, at its expense, protect and defend Lessors title against all
persons claiming against or through Lessee and shall at all times keep the
Equipment or Software free and clear from any legal process, liens or
encumbrances whatsoever (except any placed thereon by Lessor or person or entity
                                                             -------------------
claiming through Lessor) and shall give Lessor immediate written notice thereof
-----------------------                                                        
and shall indemnify and hold Lessor harmless from and against any loss caused
thereby.

XI.  Lessor's Ownership Rights
     -------------------------

     The Equipment and Software shall at all times remain the property of
Lessor.  Lessee covenants and agrees that, upon the request of Lessor, it shall
cause the Equipment and Software to remain labeled as a Lessor unit of Equipment
or Software.  Lessee shall replace any such stenciling, tag or plate which may
be removed or destroyed or become illegible.  Lessee shall keep all Equipment
and Software free from any marking or labeling which might be interpreted as a
claim of ownership thereof by Lessee or might be interpreted as a claim or
anyone so claiming through Lessor.

XII. Binding Nature
     --------------

     Each Order shall be binding upon and shall inure to the benefit of Lessor,
Lessee and their respective successors, legal representatives and assigns.

XIII. Installation
      ------------

     Lessor is to install Equipment or Software, Lessee shall, in addition to
                                                               --------------
being liable for Lessors installation rates in effect at time of order, have the
----------------------------------------------------------------------          
site prepared prior to the beginning of the installation period at Lessee's
                                                                -----------
expense.  Installation will be scheduled Monday through Friday (excluding Lessor
-------                                                                         
holidays), 8:00 a.m. to 6:00 p.m., local time.  'After Hours' installation is
available

                                      -6-

 
and if requested by Lessee, Lessor will respond with a quotation for such
installation. Lessee shall provide timely computer programming support, if
required, during installation at no charge to Lessor. Preparation shall be in
accordance with Lessors installation site preparation specifications.  Lessor
shall install the Diagnostic Controller (if applicable).

XIV. Warranty and Remedy
     -------------------

     Lessor warrants all Equipment obtained hereunder to be free from defects in
material and workmanship in normal service and under normal conditions for one
(1) year from date of the initial invoice, and further, that the Equipment
obtained under the initial order hereunder is fit for the purposes described in
the Data Network Description attached hereto as Exhibit 3 and conforms to the
standard specifications at the time of the Order.  THE FOREGOING WARRANTY IS IN
LIEU OF ALL OTHER WARRANTIES EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING
WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.  THIS WARRANTY
IS VOID AS TO EQUIPMENT AND SOFTWARE LOCATED OUTSIDE OF THE UNITED STATES OF
AMERICA.

     Should a unit of Equipment, which is not subject to an effective Lessor
                                 -------------------------------------------
maintenance agreement fail in normal service and under normal conditions through
---------------------                                                           
no fault of the Lessee during the warranty period, Lessee shall return the
failed unit at Lessor's expense to Lessor's point of origin facility.  Lessor
shall either repair the unit at the factory or furnish a used, refurbished
replacement unit for the Lessee.  No charges will be made for repair or
replacement.  Lessee shall connect and adjust the unit in accordance with
accompanying instructions.  Each repaired or replacement unit of equipment is
warranted (as set forth above) for sixty (60) days from the date of shipment of
such repaired unit, or the remaining portion of the original Equipment's
warranty, whichever is longer. Lessee agrees to pay Lessor's then standard time
and material charges for repairs made outside of those covered by the Warranty.
For any nonconformance of the Software (if applicable) to its specification
which affects performance and is reported to Lessor by Lessee, in writing,
during the initial ninety (90) days following deployment, Lessor shall provide
an analysis of the problem and workable solution.  For Software nonconformances
                                                   ----------------------------
which are recorded in writing to Lessor by Lessee subsequent to the
-------------------------------------------------------------------
aforementioned ninety (90) day Software warranty period, Lessee agrees to pay
-------------------------------------------------------                      
Lessors then current Software charges for analysis and efforts to obtain
workable solutions provided outside of those covered by the Warranty.  Lessee
agrees that it will in no event, alter, modify, repair, disassemble, or adjust
the Equipment or Software obtained hereby, except in accordance with Lessor
instructions. Lessor's obligations hereunder are contingent upon proper storage,
installation, use and maintenance and are limited to:  (1) repair, or at its
option, replacement (as described herein above) of any parts or Equipment when
the parties agree that the Equipment does not conform to the Warranty; (2)
analyzing and providing a workable solution to Software problems when Lessor
determines that the nonconformance significantly affects performance in
accordance with standard specifications and the specifications required pursuant
to Exhibit A; (3) termination of the lease and if the remedy provided for herein
has failed of its essential purpose, recovery of such damages as provided for
herein by the Lessee.  Maintenance of Software, as used herein, is the
implementation by Lessee of Software revisions provided by Lessor.  Revisions
consist of improvements of specified programs.  THE FOREGOING CONSTITUTES
LESSEE'S SOLE

                                      -7-

 
AND EXCLUSIVE REMEDY AND IS IN LIEU OF ANY AND ALL OTHER REMEDIES WHICH MAY BE
AVAILABLE TO LESSEE.

XV.  Care, Use and Maintenance
     -------------------------

     Lessee shall, at its sole expense, at all times during the term of each
Order, maintain the Equipment and Software in good operating order, repair,
condition and appearance and protect the Equipment and Software from
deterioration, other than normal wear and tear.  Lessee shall not use the
equipment or Software for any purpose other than that for which it was designed.
Lessee shall, at its sole expense, enter into and maintain in force, for the
term of each Order, a maintenance agreement.

XVI. Software License
     ----------------

     a.  Lessor hereby grants to Lessee a revocable, nonexclusive license
to uses copy of the Software in object code form, and only on a singly
designated processing unit for Lessee's own internal use, except that Lessee may
execute the Software on another processing unit on a temporary basis during a
malfunction which prevents execution of the Software on the existing processing
unit. Lessee agrees not to copy Software in whole or in part without the written
consent of Lessor except Lessee may maintain an archival copy of the Software
for back-up purposes.  Lessee agrees to reproduce any copyright and/or
confidentiality notices on any copy of the Software or any portion thereof made
by Lessee.  Additional copies of Software required by Lessee for its use must be
licensed from Lessor.

     b.  Lessee agrees to maintain complete and accurate records which identify
the type and location of the Software.  Within thirty (30) days after receiving
a request from Lessor, Lessee shall provide copies of the applicable records to
Lessor.

     c.  Lessor warrants the Software obtained hereunder shall conform to its
standard specifications and to the specifications required according to Exhibit
3 at the time that it is received by Lessee.

     d.  Title to the Software shall not pass to Lessee.  This license may not
be assigned, sublicensed, or otherwise transferred by Lessee, except that Lessee
may transfer the license to a transferee and such transferee will have the sole
benefit of the Software as transferred from Lessee provided that Lessee gives
Lessor prior written notice of such transfer and transferee agrees in writing to
be bound under this license to the same degree as Lessee.

     e.  The term of an individual units license shall be from the date of
Lessor's acceptance of an individual Order for Software until expiration of the
term set forth on the face of the individual Order or upon any default of Lessee
of any term, covenant or obligation under this Agreement.  This license may be
renewed for additional one (1) or multiple year terms provided both parties
agree to such renewal in writing at least sixty (60) days prior to the
expiration of the initial term or renewal term.  Such renewal shall be in
accordance with Lessor's standard pricing policies in effect at time of

                                      -8-

 
renewal.  Lessee agrees that upon termination or expiration of term of
individual Orders placed under license, Lessee will discontinue use of the
Software and shall certify in writing within three (3) days of termination of
this license that the Software and all copies thereof have been returned to
Lessor or destroyed.

     f.  If Lessee exercises the purchase conversion (set forth in Article
         -----------------------------------------------------------------
XXXVII below) the Software license granted to Lessee herein shall remain in
---------------------------------------------------------------------------
effect pursuant to the terms and conditions set forth herein.
------------------------------------------------------------ 

     g.  Lessee acknowledges that the Software supplied by Lessor constitutes
Lessors trade secrets and agrees to treat all Software as confidential and
proprietary.

     h.  Lessee shall not, without prior written permission of Lessor, transfer,
disclose or otherwise provide the programs to any person outside of Lessee's
organization.

     i.  Lessee shall not, without prior written permission of Lessor, modify,
reverse assemble or reverse compile any of the Software.

     j.  Lessee agrees that it shall thoroughly safeguard the confidentiality of
the Software supplied by Lessor, and in no event shall it be to a lesser extent
that Lessee safeguards its own proprietary information. Lessee agrees that
access to such Software will be given only to employees who require access in
the course of Lessee's business and such employees will be informed of the
confidential nature thereof and will be required to observe provisions of
confidence as set forth herein.

XVII. Software
      --------

     Lessor has no responsibility as to the unauthorized or improper, misuse or
     --------------------------------------------------------------------------
misapplication of the Software.  Lessee assumes full responsibility for data
------------------------------                                              
entry, data maintenance and the functional adequacy of the Software in meeting
Lessee's requirements except as provided herein, where the Software does not
conform to the specifications required by Exhibit 3.

XVIII. Taxes and Fees
       --------------

     Lessee covenants and agrees to pay when due or reimburse and indemnify and
hold Lessor harmless from and against all taxes, fees or other charges of any
nature whatsoever (together with any related interest or penalties not arising
from negligence on the part of Lessor) now or hereafter imposed or assessed
against Lessor, Lessee or the Equipment or Software by any Federal, state,
county or local governmental authority upon or with respect to the Equipment or
Software or upon the ordering, ownership, delivery, teasing, possession, use,
operation, return or other disposition thereof or upon the rents, receipts or
earnings arising therefrom or upon or with respect to any Order (excepting only
Federal, state and local taxes based on or measured by the net income of
Lessor).  If Lessee warrants that the Order shall be exempt from sales tax, it
is Lessee's responsibility to provide Lessor with valid sales tax exemption
certificates within thirty (30) days of date Order is placed.

                                      -9-

 
Notwithstanding the foregoing, unless otherwise specified in the Order, Lessor
shall be responsible for the filing of all personal property tax returns in
respect to the Equipment or Software and shall pay all taxes indicated thereon.
Lessee shall reimburse Lessor for all such taxes within thirty (30) days of
receipt of Lessor's invoice therefor.  The final invoice for personal property
taxes with respect to the lease term may be issued subsequent to the expiration
of the term due to the nature and timing of notification by the state or local
governmental authority.

XIX. Purchase Orders
     ---------------

     If a Purchase Order is required for payment, Lessee agrees to provide the
applicable Purchase Order Number(s) to Lessor.  If no Purchase Order is required
for payment, Lessee guarantees that payment will not be delayed.

XX.  Force Majeure
     -------------

     Neither party shall be considered in default in performance of such
obligations is prevented or delayed by acts of God or government, labor
disputes, failure or delay of transportation, or by vendors of subcontractors,
or any other similar cause or causes beyond the reasonable control of the other
party.  Time of performance of either parties obligations hereunder shall be
extended by the time period reasonably necessary to overcome the effects of such
force majeure occurrences.

XXI. Patent Indemnity
     ----------------

     Lessor will defend, at as own expense, any action brought against Lessor's
Lessee to the extent that it is based upon a claim that Lessor provided
Equipment or Software, infringes any patent, trade secret or copyright and
Lessor will pay costs and monetary damages finally awarded against Lessor's
Lessee in any such actions which are attributable to such claim.

     Such defense and liability is conditioned on and limited by:  (a) Lessor
being notified promptly in writing by Lessee of any such action; (b) Lessor
having sole control of the defense and all negotiations for settlement of such
action: Lessee providing all available information, assistance and authority to
enable Lessor to defend, negotiate and settle such action.

     Should such Equipment or Software become, or in Lessors opinion be likely
to become, the subject to a claim of infringement or the use thereof become
restricted by a final non-appealable Court awarded injunction, the Lessee shall
permit Lessor, at Lessor's option and expense, the right to either: (a) procure
for the Lessee the right to continue using such Equipment or Software; (b)
replace or modify such Equipment or Software so it is free from infringement or
injunction provided that the same function is performed by the replacement or
modified Equipment or Software.  In the event that Lessor does not provide the
remedial action described in (a) or (b), then Lessor may recover such Equipment
or Software from the Lessee in which case, the only rights and liabilities
between Lessor and Lessee are that:  (i) the lease shall be void as to the
Equipment or Software on the date of recovery; and (ii) Lessor has the right to
collect lease payments, if any, due from the Lessee for the Lessee's possession
of such Equipment or Software up through the date of Lessors recovery thereof

                                      -10-

 
or the date on which Lesee's use of such Equipment or Software is enjoined by a
court of competent jurisdiction whichever is earlier.

     Lessor shall have no liability to the Lessee under any provision of this
clause with respect to any claim or infringement which is based upon:

     a.  Equipment or Software based on specifications furnished by the Lessee,
or

     b.  the combination or utilization of Equipment or Software furnished
hereunder with Equipment or Software not provided by Lessor in accordance with
Exhibit 3, or

     c.  an unauthorized modification by the Lessee of Equipment or Software
         ---------------                                                    
furnished hereunder which affects the infringement.

     The foregoing expresses the entire liability of Lessor for patent or
copyright infringement by Lessor Equipment or Software to Lessee.

XXII. Default
      -------

     With the exception of a Default in the initial payment, which shall
constitute an immediate breach, failure of Lessee to make payments or to perform
any other condition of this Agreement or any Exhibit hereto, which shall
                            --------------------------------------------
continue for a period of fifteen (15) business days following written notice
----------------------------------------------------------------------------
thereof shall constitute breach of the affected Order(s) placed hereunder.  The
failure by Lessee, within sixty (60) days after the commencement of any
proceeding against Lessee seeking any reorganization, arrangement, composition,
readjustment, liquidation, dissolution, or similar relief under any present or
future statute, law, regulation, to obtain the dismissal of such proceeding or,
within sixty (60) days after the appointment, without the consent or
acquiescence of Lessee, of any trustee, receiver or liquidation of Lessee or of
all or any substantial part of the properties of Lessee to vacate such
appointment shall constitute a breach of all Orders placed hereunder.  In case
of breach, Lessor may cancel the defaulted Order(s) declare the entire amount of
the unpaid commitment and any other charges immediately due and payable and use
all available remedies to take possession and remove Equipment and Software with
all costs, including attorney's fees, to be borne by Lessee. Lessor's right to
recover possession of the Equipment and Software is in addition to all available
remedies at law or in equity.

XXIII. Severability
       ------------

     If any provision or provisions of this Agreement shall be held to be
invalid, illegal or unenforceable, the validity, legality and enforceability of
the remaining provisions shall not in any way be affected or impaired thereby,
provided such provision still expresses the intent of the parties. If the intent
of the parties cannot be preserved, the Agreement shall either be renegotiated
or rendered null and void.

                                      -11-

 
XXIV. Limitation of Liability
      -----------------------

     LESSOR SHALL NOT BE LIABLE FOR ANY INDIRECT, INCIDENTAL, SPECIAL OR
CONSEQUENTIAL DAMAGES, INCLUDING BUT NOT LIMITED TO LOSS OF PROFITS OR REVENUE,
LOSS OR USE OF THE EQUIPMENT OR SOFTWARE OR ANY ASSOCIATED EQUIPMENT OF SOFTWARE
OR COST OF SUBSTITUTED FACILITIES, EQUIPMENT, SOFTWARE OR SERVICES WHICH ARISE
OUT OF PERFORMANCE OR FAILURE TO PERFORM ANY OBLIGATION CONTAINED WITHIN THIS
AGREEMENT, OR OUT OF NEGLIGENCE IN THE COURSE OF SUCH PERFORMANCE, WHETHER THE
CLAIM FOR DAMAGES IS BASED IN CONTRACT, TORT (INCLUDING NEGLIGENCE), STRICT
LIABILITY OR OTHERWISE.

     Except for claims for personal injury or for damage to real or tangible
personal property to the extent caused by Lessors fault or negligence, Lessors
maximum liability to Lessee for any claim for damages relating to Lessors
performance or nonperformance under this Agreement shall be limited to the
lesser of the amount of payments for Equipment and Software received by Lessor
at the time the cause of action accrued or $500,000.

XXV. Governing Law; Forum
     --------------------

     This Agreement shall be governed and construed in accordance with the laws
of the State of Florida.  The parties hereby consent and submit to the exclusive
jurisdiction of the appropriate state or federal court serving Broward County,
Florida, as to any dispute or controversy arising either directly or indirectly,
under or in connection with this Agreement.

XXVI. Waiver
      ------

     No waiver by either party of any default shall operate as a waiver of any
other default or of the same default on a future occasion.  No delay, course of
dealing or omission on the part of either party in exercising any right or
remedy shall operate as a waiver thereof, and no single or partial exercise by
either party of any right or remedy shall preclude any other or further exercise
thereof or the exercise of any other right or remedy.

XXVII. Insurance
       ---------

     Lessee shall, at its own expense, and at all times during the term of an
individual Order keep the Equipment and Software insured against all risks of
loss or damage from every cause whatsoever for not less than the then current
purchase price of the Equipment or Software, provided that the amount of such
insurance shall be sufficient so that neither Lessor nor Lessee shall be
considered a co-insurer.  Lessee shall also carry public liability insurance
covering both personal injury and property damage caused by the Equipment or
Software.  All such policies of insurance shall name Lessor as loss payee or
additional insured as the case may be.  Lessee shall deliver to Lessor a copy of
such Certificates of Insurance.  Each insurer shall agree by endorsement upon
each policy issued by it or by independent instrument furnished with such policy
to Lessor, that it shall give Lessor no less

                                      -12-

 
than thirty (30) days written notice before any such policy shall be materially
altered or canceled Lessee hereby appoints Lessor as Lessee's attorney-in-fact
to make claim for, receive payment of, and execute and endorse all documents,
checks or drafts for loss or damage under any such policies of insurance

XXVIII. Risk of Loss
        ------------

     Lessee shall bear the entire risk of loss, theft, damage or destruction of
the Equipment and Software from any cause whatsoever (except Lessors negligence)
from the time shipment is received by Lessee until return shipment is received
in Sunrise, Florida by Lessor.

XXIX. Government Obligations
      ----------------------

     Lessee warrants that it is, and will remain, in compliance with all export
requirements, including, but not limited to, the requirements of the Export
Administration Act and regulations, the Arms Export Control Act and regulations,
and any orders and licenses issued thereunder.  Such requirements include, but
are not limited to, obtaining all proper authorizations or licenses from the
Department of Commerce or the Department of State for the export or re-export of
any item, product, article, commodity or technical data.  Lessee additionally
warrants that it has not been, and is not currently, debarred or suspended from
or otherwise prohibited or impaired from exporting, re-exporting, receiving,
purchasing, procuring, or otherwise obtaining any item, product, article,
commodity, or technical data regulated by any agency of the government of the
United States. Lessee agrees to indemnify Lessor and hold Lessor harmless from
any costs, penalties, or other losses caused by, or related to, any violation of
the warranties contained in this contract.

XXX. Intention of Parties
     --------------------

     It is the intention of Lessor and the Lessee that any lease Orders placed
under this Agreement will be characterized as 'true leases' and not 'financing
leases' or 'leases intended for security'.

XXXI. Custom Systems
      --------------

     Supplements to this Agreement, which include any specially-configured
systems are non-cancelable.  Once acknowledged, any changes in supplements which
include specially-configured systems will result in a minimum reconfiguration
charge by Lessor to Lessee of at least Five Hundred Dollars ($500).

XXXII. Compliance with Laws
       --------------------

     Lessee shall comply with all applicable laws, ordinances, rules and
regulations and Lessee shall obtain any and all permits, licenses,
authorizations and/or certificates that may be required in any jurisdiction or
by any regulatory or administrative agency in connection with the use and/or
operation of the Equipment or Software.

                                      -13-

 
XXXIII. Quiet Enjoyment
        ---------------

     Lessor hereby agrees and covenants, so long as no default has occurred and
is continuing, that Lessee shall have, hold and quietly enjoy, subject to this
Agreement, the Equipment and every unit and part thereof during the term of this
Agreement.

XXXIV. Certificate of Deposit
       ----------------------

     As a condition precedent to Lessors obligations, including but not limited
to the acceptance of an Order hereunder, and as partial security for Lessee's
payment obligations hereunder, Lessee agrees to provide Lessor with a
Certificate of Deposit which shall be held in an escrow account pursuant to an
escrow agreement between the parties hereto.  Certain of the agreed upon
material terms of the proposed escrow agreement are set forth on Exhibit One,
attached hereto.

XXXV. Warrants in Stock
      -----------------

     As a further condition precedent to shipment of any product hereunder
Lessee and Lessor shall enter into an agreement pursuant to which Lessor shall
receive Warrants in Lessee's company stock.  Certain of the agreed upon material
terms of such agreement are set forth on Exhibit Two, attached hereto.

XXXVI. Leased Equipment Upgrade
       ------------------------

     Throughout the lease term of items of Equipment leased under this
Agreement, Lessee shall have the right to terminate the lease of individual
units of Equipment leased hereunder for the sole purpose of replacing such
Equipment with other Lessor Equipment.  Such terminations can be made only if
ALL of the following conditions are met:

     A.  The units of Equipment being terminated must have been on lease for at
least fifty percent (50%) of their original lease term; and,

     B.  The units of Equipment being terminated must have an original lease
term of twenty-four (24) months or longer; and,

     C.  Lessee shall provide at least sixty (60) days prior written notice to
Lessor to exercise this option; and,

     D.  The replacement Equipment must be leased for the same initial term as
the Equipment which is being replaced; and,

     E.  Replacement Equipment must be of equal or greater functionality and of
equivalent or greater Capital Value; and,

                                      -14-

 
     F.  The total monthly lease and maintenance payments for the replacement
Equipment must be at least seventy percent (70%) of the total monthly lease and
                           ----------------------------                        
maintenance payments for the Equipment being terminated; and,

     G.  For all Equipment being terminated, all Amounts due and payable under
the lease, including monthly lease payments to the date of termination, and any
taxes, charges and fees which arise on or before the date of termination must be
paid in full; and,

     H.  If maintenance was taken on Equipment being terminated, maintenance
must be taken on replacement Equipment; and,

     I.  De-installation and installation by Lessor will be at standard Hourly
Labor rates, unless specified otherwise by contract; and,

     J.  The order must indicate it is an upgrade and must include all serial
numbers of Equipment to be terminated.

XXXVII.  Purchase Conversion
         -------------------

     Lessee shall at all times during the term of a lease order issued pursuant
to this Agreement have an option to purchase the Equipment leased hereunder by
paying Lessor the purchase conversion price.  The purchase conversion price
shall be an amount equal to the unit purchase price set forth on the face of the
Lessor's Order Form or Lessee's Order form, reduced by fifty percent (50%) of
all lease payments paid applicable to the unit which is being converted to
purchase. However, in no event shall the purchase conversion price be less than
twenty percent (20%) of the unit purchase price set forth on the face of the
Lessors Order Form or Lessee's Order Form or the remaining lease obligation.
Exercise of this option shall in no way relieve Lessee for lease payments due up
to the date of conversion, but not yet paid, on the unit which is being
converted to purchase.

     In addition, Lessee shall have an option, upon expiration of the initial
     ------------------------------------------------------------------------
lease term, to Purchase the Equipment leased hereunder by paying Lessor the
---------------------------------------------------------------------------
purchase conversion price.  The Purchase conversion price shall be twenty
-------------------------------------------------------------------------
percent (20%) of the unit purchase price set forth on the face of the Lessors
-----------------------------------------------------------------------------
Order Form or Lessee's Order form.  Exercise of this option shall in no way
---------------------------------------------------------------------------
relieve Lessee for lease payments due up to the date of conversion, but not yet
-------------------------------------------------------------------------------
paid on the unit which is being converted to purchase.
----------------------------------------------------- 

XXXVIII. Board of Directors
         ------------------

     As a condition precedent to Lessor's obligation to accept an order and/or
ship equipment or software hereunder, the parties have agreed that they shall
have executed a side letter pursuant to which Lessor shall have the option of a
seat on the Lessee's board of directors.

                                      -15-

 
XXXIX. Further Assurances
       ------------------

     As a condition to Lessor's performance hereunder or any Order placed
pursuant hereto, Lessee agrees that it shall furnish such financial reporting
documents to Lessor on a quarterly basis, such financial reports shall include
but not limited to audited financial statements and certificates of acceptance.

XL.  Notices
     -------

     Any notices or communications given or required under this Agreement shall
     --------------------------------------------------------------------------
be sufficiently given if delivered personally in writing, or sent by telex or
-----------------------------------------------------------------------------
facsimile, federal express, registered or certified mail, postage prepaid, to
-----------------------------------------------------------------------------
the other party at the following address:
---------------------------------------- 

     TO:  Racal-Datacom, Inc.
          P.O. Box 407044
          Ft. Lauderdale, Florida 33340
          Attn:  Sr. Vice President and General Counsel


     TO:  Concentric Research Corporation
          400 Forty-First Street
          Bay City, Michigan 48708
          Attn:  President

     With a copy to:
          Susan Cook, Esq.
          Lambert, Leser, Cook, Schmidt & Giunta, P.C.
          309 Davidson Building, P.O. Box 835
          Bay City, Michigan 48707

     Such notice or other communications shall be deemed received (a) on the
     -----------------------------------------------------------------------
date delivered, if delivered personally; or (b) upon receipt, if sent by telex
------------------------------------------------------------------------------
or facsimile federal express or (c) three (3) business days after being sent, if
--------------------------------------------------------------------------------
sent registered or certified mail.
--------------------------------- 

XLI.  Maintenance Agreement
      ---------------------

     As a condition precedent to Lessor's and Lessee's obligation to accept an
order and/or ship product hereunder, the parties shall have executed and
delivered a maintenance agreement which provides for the first year of its term,
free maintenance between them respecting equipment and software purchased
hereunder.

                                      -16-

 
XLII.  Entire Agreement
       ----------------

     The terms and conditions contained in this Agreement and the referenced
                                                                  ----------
Exhibits which are hereby incorporated herein shall be applicable to all Orders
---------------------------------------------                                  
placed on Lessor by Lessee during the effectiveness of this Agreement whether
referenced or not on such Orders.  Additional or different terms contained in
Lessee's purchase orders shall not be applicable to such Orders unless expressly
agreed to in writing by Lessors authorized representative.  This Agreement,
including all Orders accepted hereunder, expresses the entire understanding and
agreement of the parties with reference to the subject matter hereof, and is a
complete and exclusive statement of the terms of this Agreement, and no
representations or agreements modifying or supplementing the terms of this
Agreement shall be valid unless in writing, signed by persons authorized to sign
agreements on behalf of both parties.


     IN WITNESS WHEREOF, this Agreement was entered into as of the day and year
first written above.


ACCEPTED:  CONCENTRIC RESEARCH CORP.     ACCEPTED:  RACAL-DATACOM. INC.
           -------------------------                --------------------------

LESSEE:  /s/ Mark Collins-Rector         LESSOR  /s/ Scott A. Thomas
         ---------------------------             -----------------------------

BY:  Mark Collins-Rector                 BY:  Scott A. Thomas
     -------------------------------          --------------------------------

TITLE:  CEO                              TITLE:  District Sales Manager
        ----------------------------             -----------------------------

DATE:  8/4/94                            DATE:  8/4/94
       -----------------------------            ------------------------------

                                      -17-

 
                                  EXHIBIT ONE

                    CERTIFICATE OF DEPOSIT/LETTER OF CREDIT


     A Certificate of Deposit shall be:  (i) provided by a mutually agreed upon
third party at least ten (10) days order to the initial shipment hereunder, (ii)
               -----------------------------------------------------------      
in an amount of $500,000 or 12.5% of the initial Order placed hereunder,
whichever is less (iii) placed in escrow pursuant to an escrow agreement to be
negotiated between the parties.  Lessee may replace the security at any time
with a Certificate of Deposit or Letter of Credit issued by Lessee in a form
                                                                   ---------
acceptable to Lessor.  The Certificate of Deposit may be released or replaced by
--------------------                              ------------------------------
Lessee when all of the following conditions am obtained by Lessee and
---------------------------------------------------------------------
satisfactorily demonstrated to Lessor:
------------------------------------- 

     a.  Lessee's net worth exceeds $3,155,000; and
         ------------------------------------------

     b.  current ratio exceeding 2:1' and
         --------------------------------

     c.  no defaults or violations of loan covenants exist on outstanding debts
         ----------------------------------------------------------------------
of Lessee; and
--------------

     d.   Lessor has been paid on all balances owed to Lessor.
          --------------------------------------------------- 

                                      -18-

 
                                  EXHIBIT TWO

                               WARRANTS IN STOCK


     Warrants issued to Lessor for the initial order hereunder shall equal ten
                                                                     -----    
percent (10%) of the Equipment Gross Lease Value.  The option price of the
                                                   -----------------------
Warrants issued shall be $1.00 per share. Lessor agrees to exercise said
------------------------                                                
warrants at any time, or from time to time as it may in its sole discretion
---------------------------------------------------------------------------
decide, within forty-eight (48) months from date of issue; after said forty-
-------------------------------                                       -----
eight (48) months, said warrants shall expire.
----------                                    

     The parties agree to enter into a mutually agreeable Warrants Agreement
         -------------------------------------------------------------------
prior to shipment of any Equipment hereunder.
-------------------------------------------- 

                                      -19-

 
                                   EXHIBIT 3

                            DATA NETWORK DESCRIPTION

     The communication system engineered by R-D is designed to provide Customer
consumers with asynchronous dial-in connectivity to Customer supported
applications and access gateways.

     The communication system as designed, provides consumer access to Customer
remote data services through the interconnection of telco circuits provisioned
by or through either a Wide Area Network provider (e.g. AT&T and/ or Racal,
whichever provides such service) or a local exchange carrier (i.e., Ameritech)
hereinafter referred to as the WAN provider.

     The WAN provider will aggregate the inbound calls and provide a total of 24
calls per T-1 connection.  The R-D ASET-1 product has been designed to support
incoming calls from asynchronous dial-up users at speeds ranging from 300 to
14,400 bps on an aggregate T-1 circuit supplied by the WAN provider.  While the
ASET-1 product was designed primarily to support aggregate incoming point of
sale transactions, outbound calls can also be initiated through the terminal
server connected to the ASET-1 chassis at the current supported speeds.

     The Customer consumer (herein dial-in user) will initiate a call through
their modem to the R-D ASET-1 product (or functionally equivalent) which will
establish a call path to an interconnected terminal server.  The Terminal Server
will establish a session via IR.  The IP traffic will be muted through the AT&T
Interspan (Frame Relay Network) by a router to Customers data center.

     The WAN providers network infrastructure will transport the user traffic to
the R-D T1 CSU and central site routers (located in the Customer data center)
where it will route the IP traffic onto the Customer local area network (LAN)
for communication to the Customer host(s).

     The R-D Equipment will provide outbound IP connectivity from the Customer
host(s) to the other data centers (hosts such as SBSs information providers,
corporate data centers, etc.) connected to the WAN providers network using R-D
provided Equipment.

                                      -20-

 
                                  Performance

     The level of service provided by the WAN providers network (i.e., Frame
Relay network) will vary and is contingent upon such things to include (but not
limited to) actual system use/load, level of usage, and the bandwidth or
committed information rate (CIR) purchased by Customer. Network response times
may by adversely affected if insufficient bandwidth is purchased or network
usage exceeds application operational thresholds.

     R-D, working in concert and in cooperation with the WAN Provider and
Customer, will jointly determine the cause of problems which adversely affect
the network, utilization levels must be monitored on a regular basis by Customer
staff and the WAN Provider.  R-D will monitor the network performance throughout
the course of the installation process and will suggest and advise Customer as
to the need for remedial action necessary to maintain peak performance.

     The level of service (performance) as perceived by the network users will
depend upon many factors, some of those factors are listed below:

     1.   The bit rate of the network user's dial-up connection will directly
affect the data transfer rate.  A faster connection will naturally allow a
greater amount of data to be transported in a shorter period of time.  R-D will
make every effort to ensure that its' Equipment is able to connect to the
network users at the fastest rate possible based upon equipment readily
available to network users in the commercial marketplace and that such equipment
will meet generally agree upon standards of speed/operation (such as CCITT
specifications).

     2.   The use of error correcting modems such as MNP, V.42 bis, V-fast
protocols and speed will improve the level of service provided to the network
user by detecting telephone line induced errors and retransmitting the network
users' data.  Error correction functionality may introduce some delay when
errors are detected which result in the retransmission of data.  R-D's Equipment
will conform to generally accepted levels of service as demonstrated by
competitive modems accomplishing the same task.

     3.   High network utilization of a particular network access point or point
of presence POP) may affect the level of service perceived by the network users.
The speed of the link in to the WAN provider's network must offer sufficient
capacity to provide consistent and adequate response times.

     4.   Network users connecting via SLIP or PPP may put a greater load on the
network and R-D Equipment.

                                      -21-

 
                                   EXHIBIT 4 
[*]



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

[*]Certain information in this exhibit has been omitted and filed separately
with the Securities and Exchange Commission. A total of 19 pages containing
such information has been omitted from this exhibit. Confidential treatment
has been requested with respect to the omitted portions.

                                      -22-

 
The Racal Corporation
Law Department
1801 N. Harrison Parkway
Sunrise, Florida 33323-2899
Telephone
Telecopier
                                           Please reply to:
                                           PO Box 407044
                                           Ft. Lauderdale, FL 33340-7044
                                           Direct Dial:

March 30, 1995


Mr. Don Schutt, Chief Operating Officer
Concentric Research Corporation
400 Forty First Street
Bay City, MI 48708

Dear Don:

I am writing to confirm the agreements that we reached at our meeting today
respecting certain matters involving the business relationships between Racal-
Datacom, Inc. ('RDI') and Concentric Research Corporation ('CRC') as set forth
below.

1.  With respect to the Master Lease Agreement No. CON01C, dated August 4, 1994,
    between RDI and CRC (the 'Agreement'), we agreed that (a) the Commencement
    Date as defined in section iv. of the Agreement shall be March 31, 1995. The
    Equipment (as that term is defined in the Agreement) has been Deployed at
    the sites set forth in Exhibit A which is attached to this letter.

2.  With respect to initial monthly billing and payments, we have agreed as
    follows:

     (a) The monthly billing as of this date based upon Equipment which has been
         ordered pursuant to an RDI sales order in not less than [*] per month
         and may equal [*] per month for the term stated on each order. RDI
         believes that the monthly billing amount equals [*]. RDI shall provide
         CRC with documentation to support its contention of the current monthly
         billing amount.

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

     [*]Certain information on this page has been omitted and filed separately
with the Securities and Exchange Commission.  Confidential treatment has been
requested with respect to the omitted portions.

 
     (b) Payments for the items set forth in 2(a) for the months of April, May
         and June, 1995 shall be deferred until and shall commence on July 15,
         1995. The payments due for April, May and June, 1995 shall be amortized
         over the six month period commencing July 15, 1995 through December 15,
         1995 (the 'Deferred Payment period'). The resulting monthly payment
         will be:

             [*]

     The total does not include any other RDI charges for additional equipment
     or services ordered after this date or charges provided for in any of the
     agreements existing between CRC and RDI on the date hereof.

3.   Certain outstanding nor invoices to CRC are set forth below. They will be
     paid as follows:

     (a) RDI invoice number 796676 for professional services in the amount of 
         [*]. This invoice shall be paid prior to April 15, 1995.

     (b) RDI Invoice number 796677 in the amount of [*]. RDI shall provide CRC
         with the documentation in its possession and cooperate with CRC in
         efforts to secure the credit from AT&T to CRC which was previously
         negotiated among CRC, RDI and AT&T for the invoiced amount. CRC shall
         pay RD: the invoiced amount immediately upon CRC's receipt of the
         credit in this amount from AT&T.

     (c) RDI Invoice number INV5435 in the amount of [*] for actual freight
         charges for Equipment shipped pursuant to the Agreement. RD: shall
         provide CRC with such backup material for the freight charges incurred
         as reasonably requested by CRC. This invoice shall be paid prior to
         April 15, 1995.

     We have agreed that the invoices set forth in items 3(a) and 3(c) shall
     accrue interest at a rate of 10% commencing on March 31, 1995 and
     continuing until the invoices have been paid, provided, however, if CRC has
     paid the aforementioned invoices on or prior to April 15, 1995, RDI shall
     waive the accrued interest.

4.   The Sun Bank loan will be repaid by CRC in accordance with the terms set
     forth in the Reimbursement Agreement between nor and CRC dated as of
     February 15, 1995 or prior to April 15, 1995, whichever occurs earlier.

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

     [*]Certain information on this page has been omitted and filed separately
with the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.

 
5.   CRC and RDI are parties to a Remote Network Operations Agreement number
     CON03C between CRC and RDI, dated October 14, 1994 (the 'Net Ops
     Agreement') which provides for monthly payments from CRC to RDI in the
     amount of [*] for a period of forty-eight (48) months (extended
     value [*]), CRC has expressed a desire to secure services in lieu of
     those provided for in the Net Ops Agreement. RDI has proposed a Network
     services Transition Program. CRC and RDI agree to negotiate in good faith
     to attempt to reach an agreement respecting the provision of a Network
     Services program by RDI which would supersede the Net Ops Agreement.

6.   RDI shall prepare and present to CRC and Critical Technologies Inc.
     ('Critical') proposed leases for space in connection with the eight RDI
     locations which are currently P.O.P. sites for the deployed Equipment. RDI,
     CRC and Critical shall negotiate in good faith towards a lease for the
     P.O.P. site.

7.   Prior to assuming its seat on CRC'S Board of Directors, RDI will exercise
     its warrants on 100,000 shares of CRC'S common stock at one dollar per
     share. We have further agreed that the exercise price can, at RDI's option,
     be payable by the forgiveness of debt, in the form of the issuance of a
     credit to CRC.

Other than item 2, respecting the deferral of CRC's payment obligations for the
months of April, May and June, 1995, nothing contained in this letter is
intended to or shall amend, alter, cancel, or extinguish any rights or
obligations of CRC or RDI under any existing agreements between us.

If the foregoing is acceptable to CRC, please signify by signing in the space
provided below.


Joseph E. Carpenter, Jr.
General Counsel and
Senior Vice President, Administration


Accepted on behalf of Concentric Research Corporation this 30th day of 
March, 1995.
Concentric Research Corporation

By: Don Schutt
as its Chief Operating Officer

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

     [*]Certain information on this page has been omitted and filed separately
with the Securities and Exchange Commission.  Confidential treatment has been
requested with respect to the omitted portions.

 
                                                                     Exhibit A

[*]

---------------------
     [*]Certain information in this exhibit has been omitted and filed
separately with the Securities and Exchange Commission.  A total of 4 pages
containing such information has been omitted from this exhibit.  Confidential
treatment has been requested with respect to the omitted portions.