EXHIBIT 10.21

                                  AMENDMENT TO
                             KEY EMPLOYEE AGREEMENT
                                       AND
                       CONFIDENTIAL INFORMATION AGREEMENT


         THIS  AGREEMENT,  dated and  effective as of February  28, 1997,  among
Victor J. Melfa, Jr.  ("Employee") and Nexar  Technologies,  Inc. (f/k/a Dynasys
Systems Corporation), a Delaware corporation (the "Company"), amends (i) the Key
Employee  Agreement  entered  into on or about  April  1,  1995  (the  "Original
Employment   Agreement")   between  the  Company  and   Employee  and  (ii)  the
Confidential  Information  Agreement entered into on or about April 1, 1995 (the
"Original Confidentiality Agreement") between the Company and Employee.

         The parties hereto agree as follows:

         1. The text of Section  1.1 of the  Original  Employment  Agreement  is
amended to read in its entirety as follows:

         "You shall serve as Senior Vice  President  of Sales of the Company (or
         in such other executive capacity as shall be designated by the Chairman
         of the Board of  Directors  or the  President  of the  Company) and you
         shall perform the duties customarily associated with such capacity from
         time to time and at such place or places as the  Chairman  of the Board
         of  Directors  or the  President  of the  Company  shall  designate  as
         appropriate and necessary in connection with such employment."

         2. The text of Section 1 of Exhibit A (entitled "Term") to the Original
Employment Agreement is amended to read in its entirety as follows:

         "The term of the  Agreement  to which  this  Exhibit A is  annexed  and
         incorporated  shall be for three (3) years,  commencing  March 1, 1997,
         unless  terminated  prior thereto in accordance with Section 2.2 or 2.3
         of the Agreement."

         3. The text of subparagraphs (a) and (c) (subparagraph (b) remaining in
full force and  effect) of Section 2 of Exhibit A (entitled  "Compensation")  to
the Original Employment  Agreement are each amended to read in their entirety as
follows:

         "(a) Base  Salary.  Your Base  Salary is One  Hundred  Twenty  Thousand
         Dollars  ($120,000)  per annum as of April 1, 1997,  and thereafter for
         the term of the Agreement,  to be paid in accordance with the Company's
         payroll  policies  and  to  be  subject  to  increases   thereafter  as
         determined in good faith by the Board of Directors (or a duly appointed
         Compensation Committee thereof)."

         "(c)  Severance  Package  Pursuant to Section  2.2(d) of the Agreement:
         twelve (12) months Base Salary."






         4. The text of the second paragraph of Section 5 of Exhibit A (entitled
"Expenses")  of the  Original  Employment  Agreement  is  amended to read in its
entirety as follows:

         "The Company will  provide you with a monthly  automobile  allowance of
         $600."

         5. The following new Section 7 of Exhibit A (entitled "Vesting of Stock
Options Upon IPO") is added to the Original Employment Agreement:

         "7. Vesting of Stock Options Upon IPO. All stock options held by you as
         of  February  28,  1997,   will  vest  50%  upon   consummation  of  an
         underwritten  registered  initial  public  offering  (an  "IPO") of the
         common  stock of the  Company and in full one year after the closing of
         such IPO and immediately prior to a change of control."

         6.  Section 3.2 of the  Original  Confidentiality  Agreement  is hereby
amended to read in its entirety as follows:

         "For  purposes  of  this   Agreement,   "Inventions"   shall  mean  all
         discoveries, processes, designs, methods, works, technologies, devices,
         or improvements in any of the foregoing or other ideas,  whether or not
         patentable or copyrightable,  or reduced to practice,  made, conceived,
         authored or  developed  by me (whether  solely or jointly  with others)
         during the period of my employment with the Company, or within one year
         thereafter,  which  relate in any manner to the actual or  demonstrably
         anticipated  business,  products,  or research and  development  of the
         Company,  or result from or are suggested by any task assigned to me or
         any work performed by me or on behalf of the Company."

         7.  Section 3.3 of the  Original  Confidentiality  Agreement  is hereby
amended to read in its entirety as follows:

         "Any discovery,  process, design, method, technique,  work, technology,
         device, or improvement in any of the foregoing or other ideas,  whether
         or not  patentable  or  copyrightable  and  whether  or not  reduced to
         practice,  made or  conceived  by me  (whether  solely or jointly  with
         others)  which I develop  entirely  on my own time not using any of the
         Company equipment,  supplies,  facilities,  or trade secret information
         ("Personal  Invention") is excluded from this  Agreement  provided such
         Personal  Invention  (i) does not relate to the actual or  demonstrably
         anticipated  business,  products,  or research and  development  of the
         Company,  and (ii) does not result,  directly or  indirectly,  from any
         work performed by me or on behalf of the Company."


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         8. The respective  addresses for notices under the Original  Employment
Agreement and the Original Confidentiality Agreement shall be as follows:

                  If to Nexar:             Nexar Technologies, Inc.
                                           182 Turnpike Road
                                           Westborough, MA  01581
                                           Attention:  Albert J. Agbay, Chairman

                  If to Employee:          Victor J. Melfa, Jr.
                                           c/o Nexar Technologies, Inc.
                                           182 Turnpike Road
                                           Westborough, MA 01581

         9.  Except to the extent  modified  hereby,  all terms of the  Original
Employment  Agreement  and  the  Original  Confidentiality  Agreement  shall  be
unaffected hereby and shall continue in full force and effect.


                                    * * * * *

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         EXECUTED as of the date first above written.





                               By:      Victor J. Melfa, Jr.


                               NEXAR TECHNOLOGIES, INC.



                               By:      Albert J. Agbay, Chairman,
                                        Chief Executive Officer and President




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