Document:

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                                                                   EXHIBIT 10.12
                                November 5, 1998

Mr. Leonard N. Mackenzie
2711 N. Haskell, Suite 2050 LB20
Dallas, TX 75204

Re:     Termination of Consulting Agreement Dated April 15, 1997

Dear Len:

This letter is written to set forth the agreement which has been reached between
you and General Automation, Inc. (the "Company") concerning the termination of
the letter agreement between you and the Company dated April 15, 1997 (the
"Consulting Agreement"). Our agreement concerning termination of the Consulting
Agreement is as follows:

1. Termination of Consulting Agreement. The Consulting Agreement is hereby
terminated in its entirety, except as stated in the last sentence of this
Section 1. Accordingly, but without limiting the generality of the foregoing,
you shall no longer have any obligation to provide consulting services to the
Company under Section 2 of the Consulting Agreement, and the Company shall no
longer have any obligations to make payments to you or on your behalf under
Section 3 of the Consulting Agreement. The termination of the Consulting
Agreement shall not, however, affect in any manner your resignation as an
employee of the Company effective as of April 15, 1997 as contemplated by
Section 1 of the Consulting Agreement, or the termination of the Incentive Stock
Option dated August 29, 1994 previously held by you, as contemplated by Section
8 of the Consulting Agreement, or your obligations under Section 12 of the
Consulting Agreement.

2. Payments by the Company. In consideration of your execution of this letter
agreement, the Company will pay to you the amount of $75,000, without interest,
in two (2) equal payments. The first payment to be made upon signing of this
letter and the second payment to be made ninety (90) days from signing of this
letter. At your request, GA will pay an additional $134,000, without interest,
to Marian Lenore Mackenzie as additional consideration for your execution of
this letter agreement. The Company will pay this amount to Marian Lenore
Mackenzie as follows: $36,666.66 upon execution of this letter and seven (7)
monthly installments of $12,222.22 each commencing on December 1, 1998 and
continuing on the first day of each calendar month thereafter to and including
June 1, 1999, and one final installment of $11,777.80 on July 1, 1999.

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Mr. Leonard Mackenzie
November 5, 1998
Page 2

3. Release of Claims Under Consulting Agreement. You hereby release and
discharge the Company and its officers, directors, employees and agents (each a
"Company Releasee") from any and all claims, demands, causes of action,
obligations, contracts, agreements, obligations, debts and liabilities
whatsoever (collectively, "Claims"), which you now have or have ever had against
any Company Releasee under or arising out of the Consulting Agreement or any
breach or alleged breach of the Consulting Agreement. Without limiting the
generality of the foregoing, you hereby release and discharge any obligation on
the part of the Company to issue the Warrant contemplated by Section 7 of the
Consulting Agreement. In connection with the foregoing, you hereby represent and
warrant to the Company that there has been no assignment or other transfer,
voluntarily or by operation of law, to any other person or entity of any Claims
which are the subject of the release set forth in this Section 3. You further
hereby represent and warrant to the Company that your execution and delivery of
this letter agreement does not require the consent or approval of any other
person or entity.

4. Release by the Company of Claims Under Consulting Agreement. The Company
hereby releases and discharges you from any and all Claims which the Company now
has or has ever had against you under or arising out of the Consulting Agreement
or any breach or alleged breach of the Consulting Agreement, excluding only
Claims pertaining to breach of Section 12 of the Consulting Agreement. In
connection with the foregoing, the Company hereby represents and warrants to you
that there has been no assignment or other transfer, voluntarily or by operation
of law, to any person or entity of any Claims which are the subject of the
release set forth in this Section 4.

5. Taxes. You will be solely responsible for, and will pay when due, all income,
self-employment and other taxes attributable to all amounts paid to you or on
your behalf under this letter agreement.

6. Miscellaneous.

                (a) Entire Agreement. This letter agreement contains the entire
        understanding between the parties hereto, and supersedes any prior
        written or oral agreement between the parties concerning the subject
        matter contained herein. There are no representations, agreements,
        arrangements or understandings, oral or written, between the parties
        hereto, relating to the subject matter contained in this letter
        agreement, which are not fully expressed herein.

                (b) Amendment. This letter agreement shall not be modified or
        amended except by a writing signed by both of the parties hereto.

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Mr. Leonard Mackenzie
November 5, 1998
Page 3

                (c) Counterparts. This letter agreement may be executed in
        counterparts, each of which shall be deemed to be an original, but such
        counterparts, when taken together, shall constitute one and the same
        agreement.

                (d) Attorneys' Fees. If any action at law or equity is brought
        concerning any provision of this letter agreement or the rights and
        duties of any person in relation thereto, the prevailing party in such
        action shall be entitled to reasonable attorneys' fees and costs in such
        action in addition to any other relief to which it may be entitled.

                (e) Parties in Interest. Nothing in this letter agreement,
        express or implied, is intended to confer upon any person or entity,
        other than the parties to this letter agreement and their respective
        successors and assigns, any rights, remedies, obligations or liabilities
        under or by reason of such agreement.

        To acknowledge your agreement to the foregoing, please sign the
additional copy of this letter that is enclosed, and return it to me.

                                          Very truly yours,

                                          General Automation, Inc.

                                          By:
                                             ------------------------------
                                             Jane Christie, President & CEO

AGREED TO BY:

Leonard N. Mackenzie<PAGE>   1
                                                                   EXHIBIT 10.13
                                PROMISSORY NOTE

                                   May 4, 1998

1.      General Automation, Inc. currently owes NCR Corporation ("NCR"), a
        Maryland corporation, the principal of $1,723,921.92. For Value
        received, General Automation, Inc. promises to make payments to NCR as
        set out in this Promissory Note as follows:

2.      The payment of the above principal, together with interest at the rate
        of 18% per annum shall be paid in a combination of eighteen (18)
        consecutive monthly payments of $86,065.25 each and one (1) balloon
        payment of $490,329.86. The first payment shall be due on May 1, 1998
        with the remaining payments due on the first of each month thereafter.

3.      General Automation and NCR agree that the principal amount in Paragraph
        1, subject to future reconciliation, will be adjusted up or down to the
        agreed upon amount at that time, with an appropriate adjustment to the
        monthly payment in Paragraph 2, Amortization will still occur over 24
        months, with a balloon payment due in 18 months.

4.      PAYMENT SHALL BE SENT VIA WIRE TRANSFER USING THE FOLLOWING INFORMATION
        PRIOR TO THE 1ST OF THE MONTH:

            BANK NAME               WACHOVIA BANK OF NORTH CAROLINA
            BANK ADDRESS            10301 DAVID TAYLOR DRIVE
                                    CHARLOTTE, NC2  28262
            ABA                     053100494
            BNF ACCT.               NCR CORPORATION
            BNF ACCT. NO            8739069518
            REFERENCE               RFBLB65245

        If General Automation fails to pay any monthly installment required to
        be paid under this Promissory Note when the installment is due, all
        unpaid installments shall, at NCR's option, become immediately due and
        payable; and in addition to such right of acceleration, NCR shall be
        entitled to any and all remedies available under the law or equity,
        including collection charges of 1.5% per month and attorney fees.
        Subject to the late fees, General Automation shall have five (5) in
        which to cure any defaults under this note.

5.      General Automation hereby waives presentment, demand for payment or
        notice of dishonor of this note, notice of protest, and protest and all
        other notices or demands in connection with the delivery, acceptance,
        performance, default, endorsement or guaranty of this instrument.

6.      General Automation shall have the right to prepay all or part of the
        outstanding principal balance under this note without penalty and
        without credit for interest paid or previously due.

7.      No act or failure to act or verbal statement can waive or alter any term
        or condition of this Promissory Note. This Promissory note shall
        constitute the sole agreement in regard to the above-said principal sum
        and shall supersede all prior agreements and understandings, whether
        oral or written. This Promissory Note may not be altered, and/or any
        provision or right waived, except in a signed writing. Any provision
        voided by law shall be severable and not impair any remaining provision.

8.      This note cannot be assigned by General Automation with the written
        consent of NCR. Any attempt to assign or otherwise transfer the
        obligation of General Automation without consent shall make this notice
        due and immediately payable in full.

NCR Corporation                            General Automation, Inc.

----------------------------               -----------------------------
By Sandra A. Martinez                      By Richard Nance
Manager, Credit &                          CFO, General Automation
Third Party Collections, NCR               5/4/98
Date: 5/4/98

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