<PAGE>
                                   Exhibit 3.1


                            CERTIFICATE OF AMENDMENT
                                       TO
                          CERTIFICATE OF INCORPORATION
                                       OF
                           COMTREX SYSTEMS CORPORATION


TO:      THE SECRETARY OF STATE
         STATE OF DELAWARE


         Pursuant to the provisions of Section 242 of the Delaware General
Corporation Law, this Certificate of Amendment is being filed in order to amend
the Certificate of Incorporation of COMTREX SYSTEMS CORPORATION, a Delaware
corporation (the "Corporation"), as set forth below:

         1.       The name of the corporation is COMTREX SYSTEMS CORPORATION.
         2. Article Fourth of the Certificate of Incorporation is hereby amended
to read in its entirety as follows:

                  "FOURTH: The total number of shares of all classes of stock
         that the Corporation is hereby authorized to issue is ELEVEN MILLION
         (11,000,000) shares, consisting of ten million (10,000,000) shares of
         Common Stock, par value $.001 per share, and one million (1,000,000)
         shares of Preferred Stock, par value $1.00 per share. The designations,
         preferences, privileges and voting powers of the shares of each class
         and the restrictions and qualifications shall be the same in all
         respects as though shares of one class, except as follows:

                           (a) Shares of the Preferred Stock may be issued from
                  time-to-time in one or more series, each of such series to
                  have such powers, designations, preferences and relative
                  participating or optional or other special rights and such
                  qualifications, limitations or restrictions thereon, as
                  expressly provided herein, or to the extent provided by law,
                  or in a resolution or resolutions providing for the issuance
                  of such series, adopted by the board of directors, which is
                  hereby vested with such authority in respect thereof. Without
                  limiting the generality of the foregoing, the board of
                  directors is hereby expressly empowered to provide for the
                  issuance of shares of Preferred Stock at any time and from
                  time-to-time in one or more series, and to fix as to each such
                  shares, by resolutions providing for the issuance of such
                  series:

                                    (i) the number of shares to constitute such
                           series, and the designation thereof;

                                    (ii) the voting power of each share of such
                           series, if any, and without limitation, the vote or
                           fraction of vote to which each such share may be
                           entitled, the events upon the occurrences of which
                           such shares may be entitled to vote, and including
                           any and all restrictions or eliminations entirely of
                           the right of such shares to vote;

                                    (iii) the rate of dividend, if any, and the
                           extent of further participation in dividend
                           distribution, if any, and whether dividends shall be
                           cumulative or non-cumulative;


<PAGE>



                                    (iv) whether or not such series shall be
                           redeemable, and if so, the terms and conditions upon
                           which shares shall be redeemable;

                                    (v) the extent, if any, to which such series
                           shall have the benefit of any sinking fund provision
                           for the redemption or purchase of shares;

                                    (vi) the rights, if any, of such series, in
                           the event of dissolution of the Corporation, or upon
                           any distribution of the assets of the Corporation;

                                    (vii) whether or not the shares of such
                           series shall be convertible, and if so, the terms and
                           conditions of which shares of such series shall be
                           convertible; and

                                    (viii)such other powers, designations,
                           preferences and relative, participating, optional or
                           other special rights and qualifications, limitations
                           or restrictions thereon as to the extent permitted by
                           law.

                           (b) Except as otherwise provided by law, the board of
                  directors shall have full authority to issue at any time and
                  from time-to-time shares of Common Stock or shares of
                  Preferred Stock in any manner and amount and for such
                  consideration as it in its absolute discretion shall
                  determine."

         3. The amendment of the certificate of incorporation herein certified
has been duly adopted in accordance with the provisions of Section 242(b) of the
General Corporation Law of the State of Delaware.

         4. The amendment shall be effective upon the filing hereof.


         IN WITNESS WHEREOF, the undersigned has executed this Certificate of
Amendment as of the 25th day of October, 1999.



                                             COMTREX SYSTEMS CORPORATION



Attested:  /s/ Anthony S. Maladra            By: /s/ Jeffrey C. Rice
          --------------------------------      -----------------------------
          ANTHONY S. MALADRA, Secretary         JEFFREY C. RICE, President