<PAGE>
 
                                 March 6, 1998

Ronald H. Bissinger

     Re:  Your Employment With ULTRADATA Corporation
          ------------------------------------------

Dear Ron,

     This letter will set forth the binding agreement of employment (the
"Agreement"), effective as of March 16, 1998 (the "Effective Date"), between you
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ULTRADATA Corporation, a Delaware corporation ("ULTRADATA").
                                                ---------   

     1.  EMPLOYMENT AND DUTIES.  During the Employment Term, as defined in
         ---------------------                                            
Section 3 below, you will serve as Vice President, Chief Financial Officer.  You
will have such duties and authority as are customary for, and commensurate with
such position, and such other reasonable duties and authority as the Board of
Directors of ULTRADATA (the "Board") or the President of ULTRADATA prescribes
                             -----                                           
from time to time.

     2.  COMPENSATION.
         ------------ 

          (a) SALARY.  For your services hereunder, ULTRADATA will pay as salary
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to you the amount of $11,250.00 per month during each of the calendar years of
the Employment Term, as defined in Section 3 below, prorated for any year in
which this Agreement is in effect for only a portion of the calendar year.  Such
salary will be paid in conformity with ULTRADATA's normal payroll period.  Your
salary will be reviewed by the Board from time to time at its discretion, and
you will receive such salary increases, if any, as the Board in its sole
discretion determines.

          (b) BONUS.  In addition to the salary set forth in Section 2(a)
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hereof, you will be eligible starting in fiscal 1998, for an annual bonus
pursuant to a formula, and determined in accordance with criteria, in each case
to be established by the Board of Directors and/or its Compensation Committee,
which formula and criteria will be communicated to you in writing reasonably in
advance of the commencement of the performance period to which such bonus will
relate.

          (c) OTHER BENEFITS.  You will be entitled to participate in and
              --------------                                             
receive benefits under ULTRADATA's standard ULTRADATA benefits plans as in
effect from time to time, 
<PAGE>
 
Bissinger, Ronald
March 6, 1998


including medical insurance, sick leave, and vacation time, subject to and on a
basis consistent with the terms, conditions and overall administration of such
plans and ULTRADATA policies.

          (d) EXPENSES.  During the term of your employment hereunder, you will
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be entitled to receive prompt reimbursement from the ULTRADATA for all
reasonable business-related expenses incurred by you, in accordance with
ULTRADATA's policies and procedures as in effect from time to time, provided
that you will properly account for such business expenses in accordance with
ULTRADATA's policy.

          (e) DEDUCTIONS AND WITHHOLDING.  All amounts payable or which become
              --------------------------                                      
payable under any provision of this Agreement will be subject to any deductions
authorized in writing by you and any deductions and withholdings required by
law.

     3.  TERM OF EMPLOYMENT.
         ------------------ 

          (a) TERM.  This Agreement will continue in full force and effect from
              ----                                                             
and including the Effective Date through and including March 16, 1999, unless
sooner terminated or extended as hereinafter provided (the "Employment Term").
                                                            ---------------   

          (b) EXTENSION OF TERM.  The term hereof may be extended by a written
              -----------------                                               
amendment to this Agreement signed by both you and ULTRADATA. Notwithstanding
the foregoing, if a Corporate Transaction (as defined below) occurs during the
Employment Term, the Employment Term will be automatically extended and the
terms and conditions of Section 3 and 4 will remain in effect.

          (c) EARLY TERMINATION.  Your employment with ULTRADATA under this
              -----------------                                            
Agreement may be terminated by ULTRADATA at any time during the Employment Term
by the President or the Board, for any reason and with or without cause, upon
delivery of written notice by ULTRADATA.  ULTRADATA is not required to give you
any advance notice of termination which, in the sole discretion of ULTRADATA,
may be effective immediately upon delivery of written notice to you.  You may
terminate this Agreement at any time by giving ULTRADATA written notice of your
resignation at least 30 days in advance; provided, however, that the Board may
determine upon receipt of such notice that the effective date of such
resignation will be immediate or some time prior to the expiration of the notice
period stated in your written notice to ULTRADATA.

          (d) TERMINATION FOR CAUSE.  Prior to the expiration of the Employment
              ---------------------                                            
Term, your employment may be terminated for Cause by the Board, immediately upon
delivery of termination notice thereof to you.  For these purposes, termination
for "Cause" will include, without limitation, termination because of your (a)
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failure or a refusal to comply in any material respect with the reasonable
policies, standards or regulations of the Company; (b) failure or a 

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<PAGE>
 
Bissinger, Ronald
March 6, 1998


refusal in any material respect, faithfully or diligently, to perform your
duties determined by the Company in accordance with this Agreement or the
customary duties of Employee's employment (whether due to ill health, disability
or otherwise); (c) unprofessional, unethical or fraudulent conduct or conduct
that materially discredits the Company or is materially detrimental to the
reputation, character or standing of the Company; (d) dishonest conduct or a
deliberate attempt to do an injury to the Company; (e) material breach of a term
of this Agreement or the Employee Invention Assignment and Confidentiality
Agreement, including, without limitation, Employee's theft of the Company's
proprietary information; or (f) an unlawful or criminal act which would reflect
badly on the Company in the Company's reasonable judgment.

          (e) TERMINATION DUE TO DEATH OR DISABILITY.  Your employment hereunder
              --------------------------------------                            
will terminate immediately upon your death.  In the event that by reason of
injury, illness or other physical or mental impairment you are (i) completely
unable to perform your services hereunder for more than two consecutive months,
or (ii) unable in the good faith judgment of the Board to perform your services
hereunder for 50% or more of the normal working day throughout six consecutive
months, then ULTRADATA may terminate your employment hereunder at the end of
such two-month or six-month period, as applicable, by delivery to you of written
notice of such termination.

     4.  PAYMENTS AND BENEFITS AFTER TERMINATION OF EMPLOYMENT.
         ----------------------------------------------------- 

     (a) TERMINATION FOR CAUSE, DEATH OR DISABILITY, CERTAIN OTHER INVOLUNTARY
         ---------------------------------------------------------------------
TERMINATION OR VOLUNTARY TERMINATION. Upon termination of your employment by
------------------------------------                                        
ULTRADATA under Section 3(c) hereof, but subject in such case to the provisions
of Section 4(b) hereof, or under Section 3(d) hereof, Section 3(e) hereof, or
upon your voluntary termination of employment pursuant to Section 3(c) hereof,
all salary and benefits hereunder will cease immediately.

     (b) INVOLUNTARY TERMINATION - OTHER THAN FOR CAUSE. Upon termination of
         ----------------------------------------------                     
your employment by ULTRADATA, you will be paid severance pay by ULTRADATA for a
period of six (6) months from and after the date of such termination.  Employee
will not be eligible for such severance until completion of three (3) months
service with Company.

     (c) INVOLUNTARY TERMINATION AFTER CORPORATE TRANSACTION.
         --------------------------------------------------- 

         (i) Definitions. For purposes of this Section 4(b):
             -----------                                    

             (A) A "Corporate Transaction" is defined as (i) a merger or
                    ---------------------                       
acquisition in which the Company is not the surviving entity (except for a
merger of the Company into a wholly-owned subsidiary, and except for a
transaction the purpose of which is to 

                                       3
<PAGE>
 
Bissinger, Ronald
March 6, 1998


change the State in which the Company is incorporated), (ii) the sale, transfer
or other disposition of all or substantially all of the assets of the Company or
(iii) any other corporate reorganization or business combination, and in which
the beneficial ownership of 50% or more of the Company's outstanding voting
stock is transferred.

             (B) The "Post-Transaction Period" is defined as the twelve-month
                      -----------------------                   
period commencing on the date of the closing or effectiveness of a Corporate
Transaction, and ending on the same numerical date in such twelfth month as the
date upon which such closing or effectiveness of the Corporate Transaction
occurred in the original month.

             (C) A "Constructive Termination Event" will be deemed to have
                    ------------------------------
occurred at ULTRADATA's close of business on the fourteenth (14th) day after,
and including, the first day, that any of the following actions is taken by
ULTRADATA and such action is not reversed in full by ULTRADATA within such
fourteen-day period unless prior to the expiration of such fourteen-day period
you have otherwise agreed to the specific relevant event in writing: (1) your
aggregate benefits are materially reduced (as such reduction and materiality are
determined by customary practice within the software industry within the State
of California) below those in effect immediately prior to the effective date of
such Constructive Termination Event, and such reduction is not applied as part
of an overall reduction in benefits in which you are treated proportionally
given your position, length of service, income and other customary relevant
factors, and/or (2) your duties and/or authority are materially decreased or
increased from those in effect immediately prior to such Constructive
Termination Event, in a way that is adverse to you, as determined by customary
practice within the software industry within the State of California and/or (3)
you are required to perform your employment obligations (other than routine
travel consistent with that prior to the effective date of such Constructive
Termination Event) at a location more than twenty-five (25) miles away from your
principal place of work for ULTRADATA as such place of work was in effect
immediately prior to the effective date of such Constructive Termination Event.

         (ii) Severance Pay For Involuntary Termination Without Cause. If at any
              -------------------------------------------------------  
time following the closing of a Corporate Transaction (A) your employment is
terminated by ULTRADATA without Cause, pursuant to Section 3(c) hereof, (but not
if your employment is terminated for Cause (under Section 3(d) hereof) or by
reason of your death or disability (under Section 3(e) hereof), nor if you
voluntarily terminate your employment under Section 3(c) hereof except if such
voluntary termination is as a result of a Constructive Termination Event), or
(B) a Constructive Termination Event occurs and you voluntarily terminate your
employment thereafter before such Constructive Termination Event is reversed by
ULTRADATA as set forth in Section 4(b)(i)(D) hereof, then from and after the
date of such termination, you will be paid severance pay by ULTRADATA: (A) if
the termination occurs during the Post-Transaction Period, for a period of
twelve (12) months from and after the date of such termination (prorated for the
first and last month of such twelve-month period if your employment is
terminated other than at the end of a calendar month) of an amount equal to the
total amount of your annualized salary as in effect immediately prior to such
termination or Constructive Termination Event, to be paid in twelve equal
installments each paid on the date you otherwise would have been paid your
salary had your employment continued; and (B) if the termination occurs
following the Post Transaction Period such termination (prorated 

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<PAGE>
 
Bissinger, Ronald
March 6, 1998


for the first and last month of such sixth-month period if your employment is
terminated other than at the end of a calendar month) of an amount equal to the
total amount of your annualized salary as in effect immediately prior to such
termination or Constructive Termination Event, to be paid in six equal
installments each paid on the date you otherwise would have been paid your
salary had your employment continued.

         (c) BONUS, BENEFITS; COOPERATION.  In the event of any termination of
             ----------------------------                  
your employment, for whatever reason, you also will be paid, when otherwise due,
any bonus to which you otherwise would be entitled, and to such continuation of
your benefits listed in Section 2(c) hereof as may be provided by ULTRADATA
policy or required by law. After any such termination of your employment, except
to the extent you are not able to do so by reason of your death or disability,
you will cooperate with ULTRADATA in providing for the orderly transition of
your duties and responsibilities to other individuals, as is reasonably
requested by ULTRADATA.

         (d) OTHER MATTERS.  In the event of any termination other than
             -------------
voluntary termination or termination for cause; employee will be entitled to
retain his company provided cellular phone and notebook computer as then
currently provided by Company. Additionally, placement services will be provided
as the Company customarily provides to other Executives leaving the Company.

     5.  PROPRIETARY RIGHTS.  You hereby acknowledge and confirm that you have
         ------------------                                                   
executed the Company's standard Employee Invention Assignment and
Confidentiality Agreement with the Company, which agreement is in full force and
effect.  The provisions of such agreement will survive any termination or
expiration of this Agreement.

     6.  MISCELLANEOUS.  This Agreement contains the entire understanding and
         -------------                                                       
sole and entire agreement between the parties with respect to the subject matter
hereof, and supersedes any and all prior agreements, negotiations and
discussions between the parties hereto with respect to the subject matter
covered hereby and may only be modified by an agreement in writing signed by
ULTRADATA and you, and which states the intent of the parties to amend this
Agreement.  If any provision of this Agreement is held to be invalid or
otherwise unenforceable, in whole or in part, the remainder of such provision
and the remainder of this Agreement will not be affected thereby and will be
enforced to the fullest extent permitted by law.  Neither this Agreement nor the
rights or obligations hereunder will be assignable by you.  ULTRADATA 

                                       5
<PAGE>
 
Bissinger, Ronald
March 6, 1998


may assign this Agreement to any successor of ULTRADATA, and upon such
assignment any such successor will be deemed substituted for ULTRADATA upon the
terms and subject to the conditions hereof. This Agreement will be binding upon
the successors and assigns of the parties hereof and upon your heirs, executors
and administrators. This Agreement has been negotiated and executed in, and will
be governed by and construed with the laws of, the State of California. Any
notice, request, demand or other communication required or permitted hereunder
will be deemed to be properly given when personally served in writing, or when
deposited in the United States mail, postage pre-paid, addressed to ULTRADATA at
the address shown at the beginning of this letter, or to you at the address
shown below, or by facsimile upon confirmation of receipt. Each party hereto may
change its address by written notice in accordance with this Section 6.


                                 Sincerely,

 

                                 ------------------------------------------
                                 Robert J. Majteles
                                 President and Chief Executive Officer




ACCEPTED AND AGREED:
--------------------


-------------------------------- 
Ronald H. Bissinger
Date signed:_____________, 1998
Address:   
           

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