Document:

<PAGE>   1

                                                                     EXHIBIT 4.9

                           MODIFICATION AGREEMENT AND
                           AMENDMENT TO LOAN DOCUMENTS

     THIS MODIFICATION AGREEMENT AND AMENDMENT TO LOAN DOCUMENTS is being
entered into as of the 19th day of July, 2000 by and between COMPASS BANK, a
state banking corporation ("Bank") and OPTIMATION, INC., an Alabama corporation
("Borrower").

                                 P R E A M B L E

     On July 9, 1999, Bank and Borrower executed that certain Revolving Credit
and Security Agreement (the "Agreement"), Revolving Credit Commercial Note in
the principal amount of SIX HUNDRED FIFTY THOUSAND AND 00/100 DOLLARS
($650,000.00) (the "Note"), and other Loan Documents, providing for a line of
credit in the maximum aggregate amount of SIX HUNDRED FIFTY THOUSAND AND NO/100
DOLLARS ($650,000.00) (the "Revolving Line"). The Borrower has requested and the
Bank has agreed to, among other things, extend the due date to June 1, 2001, and
modify certain covenants.

     Accordingly, the Bank and Borrower have agreed that the Revolving Line
shall be modified and that the documents and instruments evidencing, securing,
relating to, guaranteeing, or executed or delivered in connection with the
Revolving Line (collectively the "Loan Documents") shall be amended as set forth
below.

                                A G R E E M E N T

     NOW, THEREFORE, in consideration of the premises, the mutual agreements of
the parties as set forth herein, and for other good and valuable consideration,
the receipt and sufficiency of which are hereby acknowledged, and to induce the
Bank to modify the Revolving Line, the parties, intending to be legally bound
hereby, agree as follows:

         1.       AMENDMENT OF LOAN AGREEMENT.  The Loan Agreement shall be and
the same hereby is amended as follows:

         (a)   Section 1.10 shall be deleted in its entirety and in place
               thereof shall be substituted:

                ""Loan Documents" shall mean and include the Note, this
         Agreement and any other agreement, document or instrument now or
         hereafter evidencing, securing, guaranteeing (including, without
         limitation, Continuing Limited Guaranties executed in connection
         herewith by Dennis and Sheila Sierk (up to $166, 250.00) and Charles
         and Kerry Garrett (limited to $8,750.00) (such individuals and entities
         are jointly and severally included

<PAGE>   2

         within the term "guarantor" as the same is used in this Agreement)) or
         relating to the Revolving Line or any other Liability, obligation or
         indebtedness of Borrower to Bank, as the same may be amended."

         (b)      Section 3.1 shall be deleted in its entirety and in place
                  thereof shall be substituted:

                  "From the date hereof until June 1, 2001, or such future date
                  to which the expiration date of the Revolving Line may be
                  extended, subject to the terms and conditions of this
                  Agreement and Borrower's and all guarantor's performance of
                  and compliance with each of the Loan Documents, and so long as
                  no event of default hereunder or under any of the other Loan
                  Documents shall have occurred or be continuing, Bank agrees to
                  extend to Borrower an open-end credit line on the basis of the
                  following advance formula (such advance formula being
                  hereinafter referred to as the "Borrowing Base"): eighty
                  percent (80%) of the value of Borrower's Eligible Accounts
                  Receivable, not to exceed $650,000.00 at any one time
                  outstanding, plus fifty percent (50%) of the value of
                  Borrower's Eligible Inventory, not to exceed $350,000.00 at
                  any one time, and provided that in no event shall the
                  aggregate sum of all advances made by Bank to Borrower at any
                  one time outstanding hereunder exceed the sum of $650,000.00.
                  Within such limits and subject to the terms of this Agreement,
                  Borrower may borrow, repay without penalty or premium, and
                  reborrow hereunder, from the date of this Agreement until the
                  Maturity Date. It is expressly understood and agreed that Bank
                  shall have no obligation to make an advance under the
                  Revolving Line if the amount of such advance together with the
                  amount outstanding under the Revolving Line exceeds or would
                  exceed the lesser of (i) $650,000.00 or (ii) the Borrowing
                  Base."

         (c)      Section 7.4 shall be deleted in its entirety and in place
                  thereof shall be substituted:

                  "Borrower shall maintain a minimum Tangible Net Worth of not
                  less than $750,000 between the date hereof and December 30,
                  2000, inclusive, and to increase to $800,000 at December 31,
                  2000."

         (d)      Section 14 is hereby amended by deleting the date "June 1,
                  2000" and substituting in place thereof "June 1, 2001".

     2. EFFECT ON LOAN DOCUMENTS. Each of the Loan Documents shall be deemed
amended as set forth herein to the extent necessary to carry out the intent of
this Agreement; provided, however, all terms, conditions, representations,
warranties and agreements contained in each of the Loan Documents not amended by
this Agreement shall remain in full force and effect and are hereby reaffirmed.

<PAGE>   3

     IN WITNESS WHEREOF, the parties have caused this Agreement to be fully
executed as of the date first set forth above.

<TABLE>

<S>                                                                   <C>

                                                                       BORROWER:

Attest:                                                                OPTIMATION, INC.

By:  /s/ Charles W. Garrett                                            By:  /s/ Dennis A. Sierk
     ------------------------------------                                  --------------------------------------
Its:  Secretary                                                                 Its: President

                                                                       BANK:
Witness:                                                               COMPASS BANK

/s/ Jennifer Powell                                                    By:  /S/ Jane M. Wasden
-----------------------------------------                                  --------------------------------------
                                                                       Its:   Assistant Relations Manager

</TABLE>

<PAGE>   4

STATE OF ALABAMA
COUNTY OF MADISON

     I, the undersigned, Notary Public in and for said County in said State,
hereby certify that DENNIS SIERK, whose name as President of OPTIMATION, INC.,
an Alabama corporation, is signed to the foregoing instrument and who is known
to me, acknowledged before me on this day that, being informed of the contents
of the instrument, he, as such officer and with full authority, executed the
same voluntarily for and as the act of said corporation.

     Given under my hand this the _____ day of July, 2000.

                                  ____________________________________
                                  Notary Public
[Notary Seal]                     My commission expires:_____________

STATE OF ALABAMA
COUNTY OF MADISON

     I, the undersigned, Notary Public in and for said County in said State,
hereby certify that ______________________________, whose name as
__________________________________ of COMPASS BANK, an Alabama banking
corporation, is signed to the foregoing instrument and who is known to me,
acknowledged before me on this day that, being informed of the contents of the
instrument, she, as such officer and with full authority, executed the same
voluntarily for and as the act of said corporation.

                  Given under my hand this the ______ day of July, 2000.

                                  _______________________________________
                                  Notary Public
[Notary Seal]                     My commission expires:________________<PAGE>   1

                                                                    EXHIBIT 10.1

                              EMPLOYMENT AGREEMENT
                               OF DENNIS A. SIERK

         THIS EMPLOYMENT AGREEMENT (this "Agreement"), is made this 30th day of
March, 2001, by and between Dennis A. Sierk ("Employee") and Nematron
Corporation, a Michigan corporation ("Nematron").

         WHEREAS, pursuant to that certain Stock Purchase Agreement (the
"Purchase Agreement") dated as of March 30, 2001 by and among Nematron,
Optimation, Inc., as Alabama corporation ("Optimation"), the Employee and the
other shareholders of Optimation, Nematron acquired (the "Acquisition") all of
the issued and outstanding stock of Optimation;

         WHEREAS, as a condition precedent to the consummation of the
Acquisition, Nematron has required that Employee to enter into this Agreement to
ensure the continued employment of Employee by Nematron;

         WHEREAS, the consummation of the transactions contemplated by the
Purchase Agreement is also a condition precedent to the effectiveness of this
Agreement;

         WHEREAS, Nematron is engaged in the business of developing, producing
and selling communications, logic and control products for industrial automation
(the "Business"); and

         WHEREAS, Nematron desires to employ Employee, and Employee desires to
be employed by Nematron upon the terms and conditions set forth in this
Agreement;

         NOW, THEREFORE, in consideration of the mutual covenants and
obligations contained herein, and intending to be legally bound, the parties,
subject to the terms and conditions set forth herein, agree as follows:

         1. Employment and Term. Nematron hereby employs Employee, and Employee
hereby accepts employment with Nematron as its Vice President, Product
Development (the "Position") for a period commencing on the date hereof and
continuing for a period of three (3) years, subject to earlier termination
pursuant to the provisions of Section 10 hereof (the "Term").

         2. Duties. During the Term, Employee shall serve Nematron faithfully
and to the best of his ability and shall devote his full attention, skill and
efforts to the performance of the duties required by or appropriate for his
Position, shall use his best skill and abilities to promote the interest of
Nematron, and shall work with other officers and employees of Nematron in a
competent and professional manner. Employee agrees to assume such duties and
responsibilities as are commensurate with his Position. Employee shall report
directly to the President of Nematron.

         3. Other Business Activities. During the Term, Employee will not,
without the prior approval of the Board of Directors, directly or indirectly
engage in any other business activities or pursuits which may interfere with the
performance of his responsibilities and obligations pursuant to this Agreement.

         4. Compensation.

         (a) Nematron shall pay Employee, and Employee hereby agrees to accept,
as compensation for all services rendered hereunder and for Employee's covenant
not to compete provided for in Section 9 hereof, an initial base salary of One
Hundred Twenty Thousand Dollars ($120,000), less applicable withholdings,
commencing upon closing of the Acquisition (the "Base Salary"), payable in a
manner and at such times as is consistent with the payroll practices of
Nematron. Beginning with January 1, 2002, the Base Salary will be multiplied by
a fraction, the numerator of which will be the Gross National Product Implicit
Price Deflator (Series 310) published by the Bureau of Economic Analysis of the
United States

<PAGE>   2

Department of Commerce (base year 1987-100) (the "GNP Deflator") for the last
quarter of the preceding year of the Term and the denominator of which will be
the GNP Deflator for the year ended December 31, 2001. If publication of the GNP
Deflator is discontinued, such computation will be based upon comparable
statistics designed to measure the value of the dollar over a broad range of the
economy, published by an agency of the United States government or by a
responsible financial periodical of recognized authority selected by Employee
and Nematron.

            (b) The Employee shall also be entitled to participate in such
incentive bonus or long-term incentive programs as may be established from time
to time by the Board of Directors of Nematron, upon terms established by such
board, and, to the extent and upon the terms determined by Nematron's Board of
Directors, in Nematron's Gainsharing Program. Nematron shall grant to Employee
options to purchase 100,000 shares of the common stock of Nematron (the
"Options") pursuant to Nematron's Long-Term Incentive Plan at a price per share
equal to the closing price of Nematron's common stock on the date of the
Acquisition, which options will vest at a rate of 33 1/3% per completed year
from the grant date. Notwithstanding the foregoing, the Options shall vest and
become immediately exercisable upon the occurrence of a Change of Control of
Nematron. A "Change of Control" shall be deemed to occur on the sale, transfer
or other disposition (including by merger, consolidation or other business
combination) of (i) fifty-one percent (51%) or more of the issued and
outstanding voting equity securities of Nematron, or (ii) all or substantially
all of the assets of Nematron and its subsidiaries determined on a consolidated
basis.

         5. Other Benefits. Employee shall be entitled to those employee
benefits which Nematron, as determined by the Board of Directors or the
compensation committee thereof, may from time to time generally makes available
to its senior executives ("Benefits"). The Benefits shall initially include,
without limitation, health insurance, life insurance, and such other benefits as
the board of directors may determine from time to time. Employee shall be
entitled to four weeks of vacation per year.

         6. Reimbursement of Expenses. Subject to such conditions as Nematron
may from time to time determine, Employee shall be reimbursed for ordinary and
reasonable documented expenses incurred by him in the performance of his duties
under this Agreement. The Company shall also reimburse Employee on a monthly
basis for reasonable expenses, including coach airfare, lodging and a per diem,
incurred by Employee for commuting between Huntsville, Alabama and Ann Arbor,
Michigan during the Term.

         7. Confidentiality. Employee recognizes and acknowledges that the
Proprietary Information (as hereinafter defined) is a valuable, special and
unique asset of the Business of Nematron and/or Optimation. As a result, both
during the Term and thereafter, Employee shall not, without the prior written
consent of Nematron, for any reason, either directly or indirectly divulge to
any third-party or use for his own benefit or for any purpose other than the
exclusive benefit of Nematron any confidential, proprietary, business or
technical information or trade secrets of Nematron or of any subsidiary or
affiliate of Nematron ("Proprietary Information") revealed, obtained or
developed in the course of his employment with Nematron or Optimation. Such
Proprietary Information shall include, but shall not be limited to, the
intangible personal property described in Section 8(b) hereof, any information
relating to methods of production, manufacture, service, research, computer
codes or instructions (including source and object code listings, program logic
algorithms, subroutines, modules or other subparts of computer programs and
related documentation, including program notation), computer processing systems
and techniques, concepts, layouts, flowcharts, specifications, know-how any
associated user or service manuals or other like textual materials (including
any other data and materials used in performing the Employee's duties), all
computer inputs and outputs (regardless of the media on which stored or
located), hardware and software configurations, designs, architecture,
interfaces, plans, sketches, blueprints, any other materials prepared by
Employee in the course of, relating to or arising out of his employment by
Nematron or Optimation or prepared by any other Nematron or Optimation employee
or contractor for Nematron or Optimation or its customers, costs, business
studies, business procedures, finances, marketing data, methods, plans and
efforts, the identities of customers, contractors and suppliers and prospective
customers, contractors and suppliers, the terms of contracts and agreements with
customers, contractors and suppliers, Nematron's relationship with actual and
prospective customers, contractors and suppliers and the needs and requirements
of, and Nematron's course of dealing with, any such actual or prospective
customers, contractors and suppliers, personnel information, customer and vendor
credit information and any other materials that have not been made available to
the general public; provided, that nothing herein contained shall restrict
Employee's ability to make such disclosures during the course of his employment
as may be necessary or appropriate to the effective and efficient discharge of
the duties required by or appropriate for his Position or as such disclosures
may be required by law; and further provided, that nothing herein

<PAGE>   3

contained shall restrict Employee from divulging or using for his own benefit or
for any other purpose any Proprietary Information that is readily available to
the general public so long as such information did not become available to the
general public as a direct or indirect result of Employee's breach of this
Section 7. Failure by Nematron or Optimation to mark any of the Proprietary
Information as confidential or proprietary shall not affect its status as
Proprietary Information under the terms of this Agreement.

         8. Inventions and Property.

            (a) All right, title and interest in and to Proprietary Information
shall be and remain the sole and exclusive property of Nematron. During the
Term, Employee shall not remove from Nematron's or Optimation's offices or
premises any documents, records, notebooks, files, correspondence, reports,
memoranda or similar materials of, or containing, Proprietary Information or
other materials or property of any kind belonging to Nematron or Optimation,
unless necessary or appropriate in accordance with the duties and
responsibilities required by or appropriate for his Position, and, in the event
that such materials or property are removed, all of the foregoing shall be
returned to their proper files or places of safekeeping as promptly as possible
after the removal shall serve its specific purpose. Employee shall not make,
retain, remove and/or distribute any copies of any of the foregoing for any
reason whatsoever, except as may be necessary in the discharge of his assigned
duties, and shall not divulge to any third person the nature of and/or contents
of any of the foregoing or of any other oral or written information to which he
may have access or with which for any reason he may become familiar, except as
disclosure shall be necessary in the performance of his duties. Upon the
termination of Employee's employment with Nematron, he shall leave with or
return to Nematron all originals and copies of the foregoing then in his
possession, whether prepared by Employee or by others.

            (b) (i) Employee agrees that all right, title and interest in and to
any innovations, designs, systems, analyses, ideas for marketing programs,
customer contacts, and all copyrights, patents, trademarks and trade names, or
similar intangible personal property which have been or are developed or created
in whole or in part by Employee (A) at any time and at any place during the
Employee's employment with Nematron or Optimation and which, in the case of any
or all of the foregoing, are related to and used in connection with the Business
of Nematron or Optimation, (B) as a result of tasks assigned to Employee by
Nematron or Optimation or (C) from the use of premises or personal property
(whether tangible or intangible) owned, leased or contracted for by Nematron or
Optimation (collectively, the "Intellectual Property"), shall be and remain
forever the sole and exclusive property of Nematron. The Employee shall promptly
disclose to Nematron all Intellectual Property and the Employee shall have no
claim for additional compensation for the Intellectual Property.

                (ii) The Employee acknowledges that all the Intellectual
Property that is copyrightable shall be considered a work made for hire under
United States Copyright Law. To the extent that any copyrightable Intellectual
Property may not be considered a work made for hire under the applicable
provisions of the United States Copyright Law, or to the extent that,
notwithstanding the foregoing provisions, the Employee may retain an interest in
any Intellectual Property that is not copyrightable, the Employee hereby
irrevocably assigns and transfers to Nematron any and all right, title, or
interest that the Employee may have in the Intellectual Property under
copyright, patent, trade secret and trademark law, in perpetuity or for the
longest period otherwise permitted by law, without the necessity of further
consideration. Nematron shall be entitled to obtain and hold in its own name all
copyrights, patents, trade secrets, and trademarks with respect thereto.

                (iii) Employee further agrees to reveal promptly all information
relating to the same to an appropriate officer of Nematron and to cooperate with
Nematron and execute such documents as may be necessary or appropriate (A) in
the event that Nematron desires to seek copyright, patent or trademark
protection, or other analogous protection, thereafter relating to the
Intellectual Property, and when such protection is obtained, to renew and
restore the same, and (B) to defend any opposition proceedings in respect of
obtaining and maintaining such copyright, patent or trademark protection, or
other analogous protection.

                (iv) In the event Nematron is unable after reasonable effort to
secure Employee's signature on any of the documents referenced in Section
8(b)(iii) hereof, whether because of Employee's physical or mental incapacity or
for any other reason whatsoever, Employee hereby irrevocably designates and
appoints Nematron and its duly authorized officers and agents as Employee's
agent and attorney-in-fact, to act for and in his behalf and stead to execute
and file any such documents and to do all

<PAGE>   4

other lawfully permitted acts to further the prosecution and issuance of any
such copyright, patent or trademark protection, or other analogous protection,
with the same legal force and effect as if executed by Employee.

         9.  Covenant Not to Compete. The Employee shall not, during the Term
and for a period of one (1) year thereafter (such period, the "Restricted
Period"), do any of the following directly or indirectly, within the continental
United States, without the prior written consent of Nematron:

             (a) engage or participate in any business activity competitive with
the Business of Nematron;

             (b) become interested in (as owner, stockholder, lender, partner,
co-venturer, director, officer, employee, agent, consultant or otherwise) any
person, firm, corporation, association or other entity engaged in any business
that is competitive with the Business of Nematron. Notwithstanding the
foregoing, Employee may hold not more than one percent (1%) of the outstanding
securities of any class of any publicly-traded securities of a company that is
engaged in activities referenced in Section 9(a) hereof;

             (c) solicit or call on, either directly or indirectly, in
connection with any business which is competitive with the Business of Nematron,
any (i) customer with whom Nematron or Optimation shall have dealt at any time
or (ii) any distributor, supplier or other contracting party with whom Nematron
or Optimation shall have dealt;

             (d) influence or attempt to influence any supplier, distributor,
customer or potential customer of Nematron or Optimation to terminate or modify
any written or oral agreement or course of dealing with Nematron or Optimation;
or

             (e) except in his capacity as an employee of Nematron, influence or
attempt to influence any person to either (i) terminate or modify his
employment, consulting, agency, distributorship or other arrangement with
Nematron or Optimation or (ii) employ or retain, or arrange to have any other
person or entity employ or retain, any person who has been employed or retained
by Nematron or Optimation as an employee, consultant, agent or distributor of
Nematron or Optimation at any time during the two year period immediately
preceding the termination of Employee's employment hereunder.

         10. Termination. Employee's employment hereunder may be terminated
during the Term upon the occurrence of any one of the events described in this
Section 10. Upon termination, Employee shall be entitled only to such
compensation and benefits as described in this Section 10.

             10.1. Termination by Death or Permanent Disability.

             (a) In the event of Employee's death or Permanent Disability (as
defined below) during the Term, Employee's employment hereunder shall be
terminated thereby and Nematron shall pay to Employee or Employee's executors,
legal representatives or administrators an amount equal to the vested or accrued
and unpaid portion of his Base Salary, Benefits and other forms of compensation
and benefits payable or provided in accordance with the terms of any then
existing compensation or benefit plan or arrangement ("Other Compensation").

             (b) Except as specifically set forth in this Section 10.1, Nematron
shall have no liability or obligation hereunder to Employee's executors, legal
representatives, administrators, heirs or assigns or any other person claiming
under or through him by reason of Employee's death or Permanent Disability,
except that Employee's executors, legal representatives or administrators will
be entitled to receive the payment prescribed under any death or disability
benefits plan in which he is a participant as an employee of Nematron and to
exercise any rights afforded under any compensation or benefit plan then in
effect. For the purposes of this Agreement, "Permanent Disability" shall have
the same meaning as such phrase is given under the long term disability plan
sponsored by Nematron or, in the absence of such policy, as determined by a
physician selected by Nematron and reasonably satisfactory to Employee or his
personal representative.

<PAGE>   5
             10.2. Termination for Cause.

                   (a) Nematron may terminate Employee's employment hereunder at
any time for "cause" upon written notice to Employee. For purposes of this
Agreement, "cause" shall mean, in each case as reasonably determined by a
majority of the Board of Directors: (i) any breach by Employee of any of his
material obligations under this Agreement (other than as a result of incapacity
due to physical or mental illness), in each case if such breach is not cured
within thirty (30) calendar days after written notice thereof to Employee by
Nematron, (ii) commission of a felony or a crime involving moral turpitude or
other commission of any act or omission of Employee involving dishonesty, fraud,
embezzlement, theft, substance abuse or sexual misconduct with respect to
Nematron or any of its affiliates or subsidiaries or any of their employees,
vendors, suppliers, distributors or customers, (iii) Employee's substantial
neglect of duties or failure to follow a lawful directive of the Board of
Directors within the scope of his employment after written notice from the Board
of Directors of such neglect or failure has not been cured within thirty (30)
days after the Employee receives such notice, (iv) the Employee's
misappropriation of funds or assets of Nematron or one of its affiliates or
subsidiaries for personal use, or (v) the Employee's gross negligence or willful
misconduct in the performance of his duties.

                   (b) In the event of a termination of Employee's employment
hereunder pursuant to Section 10.2(a), Employee shall be entitled to receive all
vested or accrued but unpaid (as of the effective date of such termination) Base
Salary, Benefits and Other Compensation. All Base Salary, Benefits and Other
Compensation shall cease at the time of such termination, subject to the terms
of any benefit or compensation plan then in force and applicable to Employee.
Except as specifically set forth in this Section 10.2, Nematron shall have no
liability or obligation hereunder by reason of Employee's termination pursuant
to this Section 10.2.

             10.3. Termination Without Cause.

                   In the event of termination by Nematron of Employee's
employment hereunder without Cause, Employee shall be entitled to receive all
accrued, but unpaid (as of the effective date of such termination) Base Salary,
Benefits and Other Compensation, plus an amount equal to One hundred percent
(100%) of the Employee's annual Base Salary (as of the date of termination) for
the remainder of the Term.

             10.4. Termination for Good Reason.

                   (a) Employee may terminate his employment for "Good Reason."
For purposes of this Agreement, "Good Reason" means any material breach of this
Agreement by Company in its payment obligations or its obligations to provide
benefits under this Agreement that is not remedied by Company within ten (10)
days' after receipt of written notice thereof from the Employee, and any other
material breach by Company of any of its other obligations under this Agreement
that is not remedied by Nematron within thirty (30) days after receipt of notice
from the Employee, which notice, in either event shall set forth in reasonable
detail the specific conduct of Company that constitutes Good Reason and the
specific provisions of this Agreement on which the Employee relies. Upon an
event constituting "Good Reason", termination of employment by the Employee for
Good Reason shall be effectuated upon the expiration of the aforesaid 10 or 30
day periods without further notice.

                   (b) In the event of termination of Employee's employment
hereunder for Good Reason, Employee shall be entitled to receive all accrued,
but unpaid (as of the effective date of such termination) Base Salary, Benefits
and Other Compensation, plus an amount equal to One hundred percent (100%) of
the Employee's annual Base Salary (as of the date of termination), for the
remainder of the Term.

             10.5. Termination by Employee without Good Reason.

                   (a) Employee may terminate his employment for any reason upon
ninety (90) days' written notice to Company.

                   (b) In the event of termination of Employee's employment
hereunder pursuant to Section 10.4(a), Employee shall be entitled to receive all
accrued but unpaid (as of the effective date of such termination) Base Salary,
Benefits and Other Compensation. All Base Salary, Benefits and Other
Compensation shall cease at the time of such termination, subject to the terms
of any benefit or compensation plan then in force and applicable to Employee.
<PAGE>   6

             10.6  Termination upon Exercise of Option.

                   In the event Employee and the other former shareholders of
Optimation exercise the Option (as defined in the Purchase Agreement) and
repurchase the stock of Optimation, Employee's employment hereunder shall be
terminated as of the date of the closing of such repurchase. Upon such
termination, Employee shall be entitled to receive all vested or accrued but
unpaid (as of the effective date of such termination) Base Salary, Benefits and
Other Compensation. All Base Salary, Benefits and Other Compensation shall cease
at the time of such termination, subject to the terms of any benefit or
compensation plan then in force and applicable to Employee. Except as
specifically set forth in this Section 10.6, Nematron shall have no liability or
obligation hereunder by reason of Employee's termination pursuant to this
Section 10.6.

         11. Indemnification. Nematron shall indemnify Employee and shall save
and hold Employee harmless from, against, for, and in respect of, any and all
damages, losses, obligations, deficiencies, costs and expenses, including,
without limitation, reasonable attorneys' fees and other costs and expenses,
incident to, or arising out of, any threatened, pending or completed suit,
action, claim or proceeding, whether civil, criminal, administrative or
investigative, suffered, incurred or required to be paid by Employee by reason
of being a director, officer, employee or agent of Nematron or by reason of
service, at the request of Nematron, as a director, officer, employee or agent
of another corporation, partnership, joint venture, trust or other enterprise
(whether or not Employee continues to be a director, officer, employee or agent
of Nematron or such corporation, partnership, joint venture, trust or other
enterprise at the time such action, suit or proceeding is brought or threatened)
if the Board of Directors reasonably determines that Employee's act or omission
was taken or made in good faith and in a manner reasonably believed to be in, or
not inconsistent with, the best interests of Nematron; provided, that such act
or omission did not constitute gross negligence, willful misconduct or fraud.
The foregoing right of indemnification shall be in addition to any rights to
which Employee may otherwise be entitled and shall inure to the benefit of
Employee's heirs, executors or administrators. If authorized under the
circumstances by the Board of Directors of Nematron, Nematron may pay the
expenses incurred by Employee (including without limitation reasonable
attorneys' fees) in defending any action, suit or proceeding upon receipt of an
undertaking by Employee to repay such payment if there shall be a final
adjudication or determination that it is not entitled to indemnification as
provided herein.

         12. Other Agreements. Employee represents and warrants to Nematron
that:

             (a) There are no restrictions, agreements or understandings
whatsoever to which Employee is a party which would prevent or make unlawful
Employee's execution of this Agreement or Employee's employment hereunder, or
which is or would be inconsistent or in conflict with this Agreement or
Employee's employment hereunder, or would prevent, limit or impair in any way
the performance by Employee of his obligations hereunder;

             (b) That Employee's execution of this Agreement and Employee's
employment hereunder shall not constitute a breach of any contract, agreement or
understanding, oral or written, to which Employee is a party or by which
Employee is bound;

             (c) That Employee is free to execute this Agreement and to enter
into the employ of Nematron pursuant to the provisions set forth herein; and

             (d) That Employee shall disclose the existence and terms of the
restrictive covenants set forth in this Agreement to any employer that the
Employee may work for during the term of this Agreement (which employment is not
hereby authorized) or after the termination of the Employee's employment at
Nematron.

         13. Survival of Provisions. The provisions of this Agreement set forth
in Sections 7, 8, 9, 11 and 22 hereof shall survive the termination of
Employee's employment hereunder.

         14. Successors and Assigns. This Agreement shall inure to the benefit
of and be binding upon Nematron and Employee and their respective successors,
executors, administrators, heirs and/or permitted assigns; provided, however,
that neither Employee nor Nematron may make any assignment of this Agreement or
any interest herein, by operation of law or otherwise, without the prior written
consent of the other party hereto, except that, without such consent, Nematron
may assign this Agreement to any

<PAGE>   7

successor to all or substantially all of its assets and business by means of
liquidation, dissolution, merger, consolidation, transfer of assets, or
otherwise, provided that such successor entity assumes in writing all of the
obligations of Nematron under this Agreement. Except as provided in this Section
14, this Agreement is not intended to, and shall not, confer any rights upon any
third parties.

         15. Notice. Any notice or communication required or permitted under
this Agreement shall be made in writing and sent by certified or registered
mail, return receipt requested, addressed as follows:

If to Employee:

                  Dennis A. Sierk
                  2613 Vista Drive
                  Huntsville, AL 35803

If to Nematron:

                  Nematron Corporation
                  5840 Interface Drive
                  Ann Arbor, MI  48103
                  Attn:  David P. Gienapp
                  Fax:   (734) 994-0352

or to such other address as either party may from time to time duly specify by
notice given to the other party in the manner specified above.

         16. Entire Agreement; Amendments. This Agreement, contains the entire
agreement and understanding of the parties hereto relating to the subject matter
hereof, and merge and supersede all prior and contemporaneous discussions,
agreements and understandings of every nature between the parties hereto
relating to the employment of Employee with Nematron. This Agreement may not be
changed or modified, except by an Agreement in writing signed by each of the
parties hereto.

         17. Waiver. The waiver of the breach of any term or provision of this
Agreement shall not operate as or be construed to be a waiver of any other or
subsequent breach of this Agreement.

         18. Governing Law. This Agreement shall be construed and enforced in
accordance with the laws of the State of Michigan.

         19. Waiver of Jury Trial. Each of the parties hereto hereby irrevocably
waives any and all right to trial by jury of any claim or cause of action in any
legal proceeding arising out of or related to this Agreement or the transactions
or events contemplated hereby or any course of conduct, course of dealing,
statements (whether verbal or written) or actions of any party hereto. The
parties hereto each agree that any and all such claims and causes of action
shall be tried by a court trial without a jury. Each of the parties hereto
further waives any right to seek to consolidate any such legal proceeding in
which a jury trial has been waived with any other legal proceeding in which a
jury trial cannot or has not been waived.

         20. Invalidity. In case any one or more of the provisions contained in
this Agreement shall, for any reason, be held to be invalid, illegal or
unenforceable in any respect, such invalidity, illegality or unenforceability
shall not affect the validity of any other provision of this Agreement, and such
provision(s) shall be deemed modified to the extent necessary to make it
enforceable.

         21. Section Headings. The section headings in this Agreement are for
convenience only, and form no part of this Agreement and shall not affect its
interpretation.

         22. Specific Enforcement: Extension of Period.

             (a) Employee acknowledges that the restrictions contained in
Sections 7, 8, and 9 hereof are reasonable and necessary to protect the
legitimate interests of Nematron and its affiliates and that Nematron would not
have entered into this Agreement in the absence of such restrictions. Employee
also acknowledges that any breach by him of Sections 7, 8, and 9 hereof will
cause continuing and irreparable injury to Nematron for which monetary damages
would not be an adequate remedy. The Employee shall

<PAGE>   8

not, in any action or proceeding to enforce any of the provisions of this
Agreement, assert the claim or defense that an adequate remedy at law exists. In
the event of such breach by Employee, Nematron shall have the right to enforce
the provisions of Sections 7, 8 or 9 of this Agreement by seeking injunctive or
other relief in any court, and this Agreement shall not in any way limit
remedies of law or in equity otherwise available to Nematron. If an action at
law or in equity is necessary to enforce or interpret the terms of this
Agreement, the prevailing party shall be entitled to recover, in addition to any
other relief, reasonable attorneys' fees, costs and disbursements. In the event
that the provisions of Sections 7, 8 or 9 hereof should ever be adjudicated to
exceed the time, geographic, or other limitations permitted by applicable law in
any applicable jurisdiction, then such provisions shall be deemed reformed in
such jurisdiction to the maximum time, geographic, or other limitations
permitted by applicable law.

             (b) In the event that Employee shall be in breach of any of the
restrictions contained in Section 9 hereof, then the Restricted Period shall be
extended for a period of time equal to the period of time that Employee is in
breach of such restriction.

         22. Counterparts. This Agreement may be executed in one or more
counterparts, each of which shall be deemed an original, and all of which
together shall be deemed to be one and the same instrument.

<PAGE>   9

         IN WITNESS WHEREOF, the parties have caused this Agreement to be
executed the day and year first written above.

                                      NEMATRON CORPORATION

                                      By:  /s/ David P. Gienapp
                                           -------------------------------------
                                      Name:  David Gienapp
                                      Title: Vice President - Finance and
                                             Administration

                                      EMPLOYEE

                                        /s/ Dennis A. Sierk
                                      ------------------------------------------
                                      Dennis A. Sierk

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