SECOND AMENDMENT TO CREDIT AUTHORIZATION
                                   AGREEMENT


         THIS SECOND AMENDMENT TO CREDIT AUTHORIZATION AGREEMENT, dated as of
August 11, 1997 (this "Amendment") by and between Interface Systems, Inc., a
Delaware Corporation, the ("Borrower") and NBD Bank, a Michigan banking
corporation (the "Bank").

                                   RECITALS

         A.      The Borrower and the Bank are parties to a Credit
                 Authorization Agreement dated as of February 19, 1997, as
                 amended by a First Amendment To Credit Authorization
                 Agreement dated as of April 21, 1997 (as amended the
                 "Agreement").

         B.      The Borrower has defaulted under the Agreement due to a
                 breach of the Net Worth covenant in section 9.3(i), for the
                 month ended June 30, 1997.

         C.      The Borrower has requested that the Bank waive such covenant
                 default, and the Bank is willing to do so strictly in
                 accordance with the terms hereof, and provided the Agreement
                 is amended as set forth herein, and the Borrower has agreed
                 to such amendment.

                                   AGREEMENT

           Based upon these recitals, the parties agree as follows:

         1.      Upon satisfaction of the conditions set forth in paragraph 4
                 hereof, the Agreement shall hereby be amended as of the
                 effective date hereof as follows:


                 A.      The definition of "Net Worth" in section 9.3(i)
                         shall be deleted in its entirety and the following
                         shall be inserted in place thereof:

                         Net Worth.       Permit its Net Worth to be less
than $11,500,000 at June 30, 1997 and increasing thereafter by 75% of
monthly net income, without reduction for any loss periods.

         2.      From and after the effective date of this Amendment,
references to the "Agreement" in the Credit Authorization Agreement, the
Note, the Security Documents, and all other documents executed pursuant to
the Credit Authorization Agreement shall be deemed references to the Credit
Authorization Agreement as amended hereby.

         3.      The Borrower represents to the Bank that:

                         (a)      (i) The execution, delivery and performance
                                  of this amendment by the Borrower and all
                                  agreements and documents delivered pursuant
                                  hereto by the Borrower have been duly
                                  authorized by all necessary action and do
                                  not and will not require any consent or
                                  approval of its shareholders, violate any
                                  provision of any law, rule, regulation,
                                  order, writ, judgment, injunction, decree,
                                  determination or award presently in effect
                                  having applicability to it or of its
                                  articles of incorporation or by-laws; (ii)
                                  no authorization, consent, approval,
                                  license, exemption of or filing a
                                  registration with any court or governmental
                                  department, commission, board, bureau,
                                  agency or instrumentality, domestic or
                                  foreign, is or will be necessary to the
                                  valid execution, delivery, or performance
                                  by the Borrower of this amendment and all
                                  agreements and documents delivered pursuant
                                  hereto and (iii) this Amendment and all
                                  agreements and documents delivered pursuant
                                  hereto by the Borrower are the legal, valid
                                  binding obligations of the Borrower
                                  enforceable against it in accordance with
                                  the terms thereof.

                         (b)      After giving effect to the amendment
                                  contained herein and effected pursuant
                                  hereto, the representations and warranties
                                  contained in Section 10.0 of the Agreement
                                  are true and correct on and as of the
                                  effective date hereof with the same force
                                  and effect as if made on and as of such
                                  effective date.

                         (c)      Other than the Existing Default, as defined
                                  in and to be waived pursuant to paragraph
                                  5, no Events of Acceleration (as defined in
                                  Section 11.0 of the Agreement) and no
                                  default shall have occurred and be
                                  continuing or will exist under the
                                  Agreement as of the effective date hereof.

                 4.      This Amendment shall not become effective until it
                         shall be duly executed by the Borrower and the
                         Bank.

                 5.      The Borrower acknowledges that an Event of
                         Acceleration has occurred because the Borrower has
                         breached a covenant contained in Section 9.3(i) of
                         the Agreement for the month of the Borrower ended
                         June 30, 1997 (the "Existing Default").  The
                         Borrower acknowledges that the Bank has the ability
                         to accelerate all indebtedness and exercise all of
                         its rights and remedies under the Agreement.  In
                         consideration of the execution of this Amendment
                         and subject to the satisfaction of the condition
                         required by Paragraph 4 hereof, the Bank agrees to
                         waive the Existing Default, provided that such
                         waiver shall waive only the Existing Default and
                         does not waive any other Events of Acceleration,
                         including without limitation any future Events of
                         Acceleration caused by any violation of Section
                         9.3(i).  This waiver shall not be deemed to be a
                         waiver, or a consent to any modification or
                         amendment, of any other term or condition of the
                         Agreement or any term or condition of any
                         agreement, instrument, or document referred to
                         therein or executed pursuant thereto, or to
                         prejudice any present or future right which the
                         Bank now has or may have hereunder.

                 6.      The terms used but not defined herein shall have
                         the respective meanings ascribed thereto in the
                         Agreement.  Except as expressly contemplated
                         hereby, the Agreement, and all related notes,
                         guaranties, certificates, instruments and other
                         documents, are hereby ratified and confirmed and
                         shall remain in full force and effect, and the
                         Borrower acknowledges that it has no defense,
                         offset, or counterclaim thereunder.

                 7.      This Amendment shall be governed by and in
                         accordance with the laws of the State of Michigan.

         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be duly executed and delivered as of the day and year first written above.

                                  INTERFACE SYSTEMS, INC.

                                  /S/
                                  ----------------------------
                              By:  David O. Shupp
                             Its:  Treasurer


                                   NBD BANK

                                  /S/
                                  ---------------------------
                              By: Michael Kelly
                            Its:  First Vice President