Document:

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                                                                     EXHIBIT 4.3

                     SECOND AMENDMENT, CONSENT AND WAIVER TO
                AMENDED AND RESTATED LOAN AND SECURITY AGREEMENT

         THIS SECOND AMENDMENT, CONSENT AND WAIVER (this "Second Amendment"),
dated as of April 12, 2001, to that certain Amended and Restated Loan and
Security Agreement dated as of June 30, 2000 (as amended by that certain First
Amendment dated as of March 1, 2001, the "Agreement"), is entered into by
NEMATRON CORPORATION, a Michigan corporation ("Borrower") and LASALLE BUSINESS
CREDIT, INC., a Delaware corporation ("Lender"). Capitalized terms used but not
otherwise defined herein shall have the meanings assigned thereto in the
Agreement.

                                    RECITALS

         A. Borrower and Lender are party to the Agreement, pursuant to which
Lender has agreed to make, and has made, certain loans, advances and credit
accommodations to Borrower pursuant to the terms and conditions set forth in the
Agreement.

         B. Pursuant to paragraph 14(m)(i) of the Agreement, Borrower and its
Subsidiaries, on a consolidated basis, were required at all times to maintain a
Tangible Net Worth plus Subordinated Indebtedness of not less than $1,250,000
during Fiscal Year ending December 31, 2000, and $2,500,000 during Fiscal Year
ending December 31, 2001.

         C. The Tangible Net Worth plus Subordinated Indebtedness of Borrower
and its Subsidiaries, on a consolidated basis, as of June 30, 2000 and each
subsequent calendar month end in the Fiscal Year ended December 31, 2000, and
January 31, 2001 and February 28, 2001, according to the financial covenant
calculations accompanying Borrower's Officer's Certificates, was less than the
applicable required minimum amount referenced in Recital B above, thus
constituting breaches and violations of paragraph 14(m)(i) of the Agreement.

         D. Pursuant to paragraph 14(m)(ii) of the Agreement, Borrower and its
Subsidiaries, on a consolidated basis, were required to maintain an Interest
Coverage Ratio as of the end of each fiscal quarter for that portion of the
Fiscal Year then ended, commencing with the fiscal quarter ending December 31,
2000, of not less than 1.50 to 1.00.

         E. The Interest Coverage Ratio of Borrower and its Subsidiaries, on a
consolidated basis, for the full Fiscal Year ended December 31, 2000 was 0.44 to
1.00, according to the financial covenant calculations accompanying an Officer's
Certificate of Borrower, thus constituting a breach and violation of paragraph
14(m)(ii) of the Agreement.

         F. Pursuant to paragraph 14(m)(iii) of the Agreement, Borrower and its
Subsidiaries, on a consolidated basis, were required to maintain a Debt Service
Coverage Ratio, as of the end of each fiscal quarter for that portion of the
Fiscal Year then ended, commencing with the fiscal quarter ending December 31,
2000, of not less than 0.75 to 1.00.

         G. The Debt Service Coverage Ratio of Borrower and its Subsidiaries, on
a consolidated basis, for the full Fiscal Year ended December 31, 2000 was
(1.48) to 1.00, according to the financial covenant calculations accompanying an
Officer's Certificate of Borrower, thus constituting a breach and violation of
paragraph 14(m)(iii) of the Agreement.

         H. Pursuant to paragraph 14(h) of the Agreement, Borrower is prohibited
from incurring any indebtedness (other than certain specified liabilities) or
guaranteeing the obligations of any Person without Lender's prior written
consent, and pursuant to paragraph 14(i) of the Agreement, Borrower may not
create any new Subsidiary (other than certain specified Subsidiaries) without
Lender's prior written consent.

         I. Borrower has acquired (the "Optimation Acquisition") 100% of the
issued and outstanding capital stock ("Optimation Stock") of Optimation, Inc.,
an Alabama corporation ("Optimation"), pursuant to the terms of that certain
Stock Purchase Agreement dated as of March 30, 2001, among Dennis A. Sierk,
Sheila D. Sierk, Charles Garrett, Kerry Garrett (all of the foregoing persons

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are "Sellers"), Optimation and the Borrower, in the form attached hereto as
Exhibit A (the "Stock Purchase Agreement").

         J. Each breach or violation described in Recitals C, E, G and I above,
and the lapse of thirty (30) days from the occurrence thereof, constitutes an
Event of Default under paragraph 16(b) of the Agreement (each is a "Subject
Default").

         K. Pursuant to paragraphs 2 and 4 of the Agreement, following the
occurrence and during continuation of an Event of Default, Lender may cease
making any further Revolving Loans and may cease causing the issuance of, and
co-signing for, any Letters of Credit, in addition to Lender's other remedies
under the Agreement.

         L. Borrower has requested that Lender waive the Subject Defaults, and
Lender is willing to do so subject to the terms and conditions set forth in this
Second Amendment.

         M. Borrower has requested that Lender consent to the Optimation
Acquisition, and Lender is willing to do so subject to the terms and conditions
set forth in this Second Amendment.

                                    AGREEMENT

         NOW, THEREFORE, in consideration of the premises and for other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, Borrower and Lender agree as follows:

1.       AMENDMENTS TO THE AGREEMENT.

         1.1 Definition of Permitted Liens. The definition of "Permitted Liens"
appearing in paragraph 1 of the Agreement is hereby amended by deleting the
phrase "and (xiv) liens securing appeal bonds" in its entirety and inserting the
phrase ", (xiv) liens securing appeal bonds, (xv) liens on assets of Optimation
in favor of Compass Bank securing indebtedness for borrowed money not exceeding
$675,000 in the aggregate, and (xvi) liens on assets of Optimation in favor of
Keith Schonrock securing indebtedness for borrowed money not exceeding $50,000
in the aggregate" in lieu thereof.

         1.2 Definition of Optimation. Paragraph 1 of the Agreement is hereby
amended by inserting a new definition of Optimation in appropriate alphabetical
sequence to read, in its entirety, as follows:

              "OPTIMATION" means Optimation, Inc., an Alabama corporation.

         1.3 Paragraph 12. Clauses (a) and (b) of Paragraph 12 of the Agreement
are hereby amended and restated to read, in their entirety, as follows:

             (a) This Agreement, as amending the Existing Agreement as of
         the Amendment Date, shall be in effect from the Closing Date until
         November 12, 2003 ("ORIGINAL TERM") and shall automatically renew
         itself from year to year thereafter (each such one year renewal being
         referred to herein as a "RENEWAL TERM") unless (i) the due date of the
         Liabilities is accelerated pursuant to paragraph 17 hereof; or (ii)
         both Borrower and A-OK elect, or LaSalle elects, to terminate both this
         Agreement and the A-OK Loan Agreement at the end of the Original Term
         or at the end of any Renewal Term by giving the other parties written
         notice of such election at least sixty (60) days prior to the end of
         the Original Term or the then current Renewal Term, in which case
         Borrower and A-OK shall pay all of the Liabilities in full on the last
         day of such term; or (iii) both Borrower and A-OK elect to terminate
         both this Agreement and the A-OK Loan Agreement at any other time
         during the Original Term or any Renewal Term upon not less than sixty
         (60) days' prior written notice to the other parties, in which case
         Borrower and A-OK shall pay all of the Liabilities in full on the date
         specified in such written notice. If one or more of the events
         specified in subparagraphs (i), (ii) or (iii) occurs, this Agreement
         shall terminate on the date thereafter on which the Liabilities are
         paid in full; provided, however, that the security interests and liens
         created under this Agreement, the A-OK Loan Agreement and the Other
         Agreements shall survive such termination until the date upon which
         payment and satisfaction in full of the Liabilities shall have
         occurred. At such time as Borrower and A-OK have repaid all of the
         Liabilities and this Agreement and the A-OK Loan Agreement have been
         terminated, (A) Borrower shall deliver, and shall cause A-OK to
         deliver, to LaSalle a release, in form

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         and substance reasonably satisfactory to LaSalle, of all obligations
         and liabilities of LaSalle and its officers, directors, employees,
         agents, parents, subsidiaries and affiliates to Borrower and A-OK, and
         if Borrower or A-OK is obtaining new financing from another lender,
         Borrower shall deliver, and shall cause A-OK to deliver, such lender's
         indemnification of LaSalle, in form and substance reasonably
         satisfactory to LaSalle, for checks which LaSalle has credited to
         Borrower's or A-OK's account, but which subsequently are dishonored for
         any reason and, (B) LaSalle shall deliver to Borrower and A-OK a
         release in form and substance reasonably satisfactory to Borrower and
         A-OK.

             (b) If this Agreement is terminated prior to the end of the
         Original Term, Borrower agrees to pay to LaSalle, as a prepayment fee,
         in addition to the payment of all other Liabilities owing by Borrower,
         an amount equal to: (i) two percent (2%) of the Total Credit Facility
         if this Agreement is terminated during the first year of the Original
         Term; (ii) one percent (1.0%) of the Total Credit Facility if this
         Agreement is terminated during the second year of the Original Term;
         (iii) one percent (1.0%) of the Total Credit Facility if this Agreement
         is terminated during the third year of the Original Term; and (iv)
         one-half of one percent (0.50%) of the Total Credit Facility if this
         Agreement is terminated on or after November 12, 2002; provided,
         however, that such prepayment fee shall not be payable if this
         Agreement is terminated (A) at the end of the Original Term pursuant to
         the terms set forth herein, or (B) at any other time by LaSalle if no
         Default or Event of Default shall have occurred and be continuing, or
         (C) by the Borrower following the issuance of any Capital Adequacy
         Demand, or (D) by the Borrower following the merger of LaSalle with and
         into, or the sale of substantially all of LaSalle's assets to, any
         Person which is not an Affiliate of LaSalle and where LaSalle is not
         the surviving entity, or (E) by the Borrower following any sale,
         assignment, transfer or other disposition by LaSalle of its rights
         under this Agreement and the Other Agreements (other than a
         participation interest herein or therein) to any Person other than an
         Affiliate of LaSalle; provided, further, that any such prepayment fee
         shall be waived if Borrower refinances all Liabilities with Standard
         Federal on or after December 31, 2001. In light of the extreme
         difficulty of accurately calculating actual damages arising out of any
         early termination, LaSalle and Borrower have agreed that the prepayment
         fee provided for above is a reasonable estimate of actual damages that
         would be incurred.

         1.4 Paragraph 14(h). Paragraph 14(h) of the Agreement is hereby amended
and restated to read, in its entirety, as follows:

                  (h) Borrower shall not (i) incur, create, assume or suffer to
         exist any indebtedness other than (A) the Liabilities, (B) unsecured
         indebtedness owing in the ordinary course of business to trade
         suppliers or utilities, (C) any other indebtedness described in
         Schedule 13(p) hereof, (D) purchase money indebtedness for fixed
         assets, (E) indebtedness described in paragraph 14(k)(v) hereof, and
         (F) unsecured indebtedness not exceeding $300,000 in the aggregate,
         owing to Dennis A. Sierk, Sheila D. Sierk, Charles Garrett and Kerry
         Garrett as a portion of the purchase price paid by the Borrower to such
         Persons in connection with Borrower's acquisition of 100% of the issued
         and outstanding capital stock of Optimation; or (ii) assume, guarantee
         or endorse, or otherwise become liable in connection with, the
         obligations of any Person, except (A) by endorsement of instruments for
         deposit or collection or similar transactions in the ordinary course of
         business, and (B) an unsecured guaranty in favor of Compass Bank of
         indebtedness of Optimation for borrowed money not exceeding $675,000 in
         the aggregate;

         1.5 Paragraph 14(i). Paragraph 14(i) of the Agreement is hereby amended
and restated to read, in its entirety, as follows:

                  (i) Borrower shall not engage in any merger or consolidation
         except where the Borrower is the surviving entity; no Subsidiary shall
         engage in any merger or consolidation except where the Borrower or a
         Subsidiary is the surviving entity; neither Borrower nor any Subsidiary
         shall sell, lease or otherwise dispose of all or substantially all of
         its assets; neither Borrower nor any Subsidiary shall create any new
         Subsidiary other than a new wholly-owned Canadian Subsidiary of
         Borrower ("CANADIAN SUB") and Borrower's acquisition of all of the
         issued and outstanding capital stock of A-OK and Optimation; no
         Subsidiary shall issue any shares of, or warrants or other rights to
         receive or purchase any shares of, any class of its stock; Borrower
         shall not permit any of its Subsidiaries (other than Nematron, Ltd., a
         company organized under the laws of England and Wales ("UK SUB"),
         Canadian Sub, A-OK and Optimation) to own or hold any property or to
         conduct any business; neither Borrower nor any Subsidiary shall engage
         in any businesses other than the

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         businesses currently engaged in by Borrower or such Subsidiary or
         businesses reasonably related thereto;

         1.6 Paragraph 14(k). Paragraph 14(k) of the Agreement is hereby amended
and restated to read, in its entirety, as follows:

             (k) neither Borrower nor any Subsidiary shall make any loans
         to, or investment in, any Person, whether in cash, securities or other
         property of any kind, other than: (i) Permitted Investments; (ii) loans
         to or investments in Subsidiaries made during the Original Term or any
         Renewal Term, other than (A) the "Purchase Price" for 100% of the
         outstanding capital stock of A-OK as paid by Borrower on or about June
         30, 2000 strictly pursuant to the terms set forth in Section 3.04 of
         that certain Stock Purchase Agreement dated as of June 30, 2000, among
         Ronald C. Causley, Trustee of the Ronald C. Causley Revocable Trust
         dated March 14, 1990, as amended, Ronald C. Causley, individually, and
         the Borrower, a true, correct and complete copy of which Stock Purchase
         Agreement has been provided by Borrower to LaSalle, (B) the "Purchase
         Price" for 100% of the outstanding capital stock of Optimation as paid
         by Borrower on or about March 30, 2001 strictly pursuant to the terms
         set forth in Section 3.04 of that certain Stock Purchase Agreement
         dated as of March 30, 2001, among Dennis A. Sierk, Sheila D. Sierk,
         Charles Garrett, Kerry Garrett and the Borrower, a true and correct
         copy of which Stock Purchase Agreement has been provided by Borrower to
         LaSalle, and (C) other loans and investments not exceeding $105,000 in
         the aggregate at any time outstanding; (iii) loans made to any
         Subsidiary prior to the Original Term and disclosed on Schedule 13(p);
         (iv) loans permitted under paragraph 14(o); (v) loans from any
         Subsidiary to the Borrower on such terms as may be reasonably
         acceptable to LaSalle; and (vi) loans to or investments in A-OK made
         during the Original Term or any Renewal Term, and not exceeding
         $1,500,000 in the aggregate at any one time outstanding;

         1.7 Paragraph 14(m). Paragraph 14(m) of the Agreement is hereby amended
and restated to read, in its entirety, as follows:

              (m) Borrower shall maintain and keep in full force and effect each
         of the financial covenants set forth below. The calculation and
         determination of each such financial covenant, and all accounting terms
         contained therein, shall be so calculated and construed in accordance
         with GAAP, applied on a basis consistent with the financial statements
         of Borrower delivered on or before the Closing Date;

                  (i) Consolidated Tangible Net Worth Plus Subordinated
              Indebtedness. Borrower and its Subsidiaries, on a consolidated
              basis, shall maintain a Tangible Net Worth plus Subordinated
              Indebtedness of not less than (A) Seven Hundred Fifty Thousand
              Dollars ($750,000) at all times through (but excluding) September
              30, 2001, (B) One Million Two Hundred Fifty Thousand Dollars
              ($1,250,000) at all times from and including September 30, 2001
              through (but excluding) December 31, 2001, (C) Two Million Five
              Hundred Thousand Dollars ($2,500,000) on December 31, 2001, (D) at
              all times (other than the last day of a Fiscal Year) during any
              Fiscal Year after December 31, 2001, ninety percent (90%) of the
              actual Tangible Net Worth plus Subordinated Indebtedness of
              Borrower and its Subsidiaries (on a consolidated basis) at the
              last day of the immediately preceding Fiscal Year (a "RESET
              DATE"), and (E) on each Reset Date occurring after December 31,
              2001, the sum of (1) the actual Tangible Net Worth plus
              Subordinated Indebtedness of Borrower and its Subsidiaries (on a
              consolidated basis) at the immediately preceding Reset Date plus
              (2) $1,250,000;

                  (ii) Consolidated Interest Coverage Ratio. Borrower and its
              Subsidiaries, on a consolidated basis, shall maintain an Interest
              Coverage Ratio as of the end of each fiscal quarter for that
              portion of the Fiscal Year then ended, commencing with the fiscal
              quarter ending December 31, 2001, of not less than 1.50 to 1.00;

                  (iii) Consolidated Debt Service Coverage Ratio. Borrower and
              its Subsidiaries, on a consolidated basis, shall maintain a Debt
              Service Coverage Ratio, as of the end of each fiscal quarter for
              that portion of the Fiscal Year then ended, commencing with the
              fiscal quarter ending December 31, 2001, of not less than (A) 1.00
              to 1.00 for the measurement period ending December 31, 2001, and
              (B) 1.25 to 1.00 for each measurement period ending after December
              31, 2001; and

<PAGE>   5

                  (iv) Capital Expenditures, Etc. Borrower and its Subsidiaries
              (other than A-OK and Optimation), on a consolidated basis, shall
              not make Capital Expenditures and payments under synthetic or
              off-balance sheet leases aggregating more than Three Hundred
              Thousand Dollars ($300,000) during the Fiscal Year ending December
              31, 2001, and Five Hundred Dollars ($500,000) during any Fiscal
              Year after December 31, 2001. Borrower and its Subsidiaries, on a
              consolidated basis, shall not incur costs totaling more than
              $1,500,000 relating to software development activities for the
              Fiscal Year ending December 31, 2001, whether expensed or
              capitalized, and not more than $2,000,000 in any Fiscal Year
              thereafter.

         1.8 Paragraph 14(p). Paragraph 14(p) of the Agreement is hereby amended
and restated to read, in its entirety, as follows:

              (p) Borrower shall not enter into or be a party to, or permit any
         Subsidiary to enter into or be a party to, any transaction with any
         Affiliate of Borrower except in the ordinary course of business for
         fair consideration and on terms no less favorable to Borrower or such
         Subsidiary as are available from unaffiliated third parties. Accounts
         due from Optimation to Borrower or A-OK must be paid within sixty (60)
         days from the date of the sale of relevant products or the completion
         of performance of the relevant services;

2.       WAIVER. Lender hereby waives the Subject Defaults, effective as of
December 31, 2000.

3.       CONSENT. Lender hereby consents to the Optimation Acquisition strictly
upon the terms and subject to the satisfaction of the conditions set forth in
the Stock Purchase Agreement.

4.       REPRESENTATIONS AND WARRANTIES. To induce Lender to enter into this
Second Amendment and to make the amendments, waivers and consent provided in
Sections 1, 2 and 3 above, Borrower represents and warrants to Lender that:

         4.1 Organization and Existence. Borrower is duly organized and validly
existing under the laws of the State of Michigan. Borrower has filed all annual
reports required to be filed on or before the date hereof with the Secretary of
State of Michigan. Borrower has not filed nor authorized the filing of, articles
of dissolution with the Secretary of State of Michigan.

         4.2 Authority, Authorization and Enforceability. Borrower has the
requisite power and authority to execute and deliver this Second Amendment and
to perform its obligations hereunder and under the Agreement as amended hereby.
Borrower has duly authorized the execution and deliver of this Second Amendment
and the performance of its obligations hereunder and under the Agreement as
amended hereby. This Second Amendment and the Agreement as amended hereby are
the legal, valid and binding obligations of Borrower and are enforceable against
Borrower in accordance with their respective terms.

         4.3 No Violation of Law or Contract. Borrower's execution and delivery
of this Second Amendment, and Borrower's performance of its obligations
hereunder and under the Agreement as amended hereby, does not and shall not
conflict with the provisions of any statutes, regulation, ordinance or rule of
law, or any agreement, contract or other document binding on Borrower.

         4.4 No Default, Event of Default or Material Adverse Effect. After
giving effect to the waivers set forth in Section 2 hereof, (a) no Default or
Event of Default has occurred or is continuing, and (b) no Material Adverse
Effect has occurred since the Closing Date.

         4.5 General Representations and Warranties Remade. Except as expressly
identified herein, all representations, warranties and covenants made as of the
Closing Date pursuant to the Agreement are hereby remade as of the date of this
Second Amendment.

5.       CONDITIONS TO EFFECTIVENESS. The effectiveness of this Second Amendment
is subject to the satisfaction of the following conditions precedent:

         5.1 Documentation. Borrower shall have delivered, or caused to be
delivered, to Lender all of the following documents, in form and substance
satisfactory to Lender:

<PAGE>   6

              (a) Second Amendment. An executed counterpart of this Second
Amendment.

              (b) Securities Pledge Agreement. An executed counterpart of the
Securities Pledge Agreement of even date herewith executed by Borrower and
Lender, pursuant to which Borrower shall pledge the Optimation Stock, along with
a duly executed stock power and the original stock certificates.

              (c) Guaranty. A guaranty duly executed by Optimation, pursuant to
which Optimation shall guarantee the prompt, punctual and faithful payment of
all Liabilities of Borrower to Lender.

              (d) Security Agreement. A security agreement duly executed by
Optimation, pursuant to which Optimation shall grant the Lender a security
interest and lien upon all of its personal property, subject only to Permitted
Liens.

              (e) Financing Statements. UCC financing statements for all
jurisdictions in which filing is necessary or desirable.

              (f) Resolutions. Resolutions of the respective boards of directors
of Borrower and Optimation, certified by such entities' respective secretaries
or assistant secretaries.

              (g) Incumbency Certificate. An incumbency certificate with respect
to the officers of Borrower and Optimation certified as of the date hereof by
such entities' secretaries or assistant secretaries.

              (h) Opinion. A legal opinion of Dykema Gossett PLLC, counsel to
Borrower and Optimation, addressed to Lender.

              (i) Consent Letter. A consent letter executed by Standard Federal
Bank.

              (j) Subordination Agreements. Lender shall have received such
subordination agreements as it may request from holders of Subordinated
Indebtedness.

              (k) Collateral Assignment. Lender shall have received a fully
executed collateral assignment of Borrower's rights under the Stock Purchase
Agreement.

              (l) Other Documents. All other documents, certificates and
agreements as Lender may reasonably request to accomplish the purposes of this
Second Amendment.

         5.2 Amendment Fee. Borrower shall have paid Lender an amendment fee
(which fee shall be deemed fully earned and nonrefundable upon the effectiveness
of this Second Amendment) in the amount of $15,000.

6.       GENERAL.

         6.1 Expenses. Borrower agrees to pay Lender, on the date hereof and
from time to time hereafter upon demand, all expenses, including reasonable
attorneys' and legal assistants' fees, incurred by Lender in connection with the
preparation, negotiation and execution of this Second Amendment and any document
required to be furnished herewith.

         6.2 Entire Agreement. This Second Amendment, the Agreement as
previously amended and as hereby, and all of the Other Agreements constitute the
entire agreement of the parties with respect to the subject matter hereof and
supersede all other understandings, oral or written, with respect to the subject
matter hereof.

         6.3 Effect of Amendment; No Waiver. Except as expressly amended
pursuant to Section 1 hereof, the Agreement and the Other Agreements shall
remain in full force and effect and are hereby ratified and confirmed in all
respects. EXCEPT AS EXPRESSLY WAIVED PURSUANT TO SECTION 2 HEREOF, THIS SECOND
AMENDMENT SHALL NOT OPERATE AS A WAIVER OF ANY RIGHT, POWER OR REMEDY OF LENDER
UNDER THE AGREEMENT OR ANY OF THE OTHER AGREEMENTS, AND LENDER RESERVES ALL
RIGHTS AND REMEDIES

<PAGE>   7

(INCLUDING, WITHOUT LIMITATION, RIGHTS AND REMEDIES ACCRUING OR EXISTING BY
REASON OF THE SUBJECT DEFAULTS).

         6.4 Miscellaneous Provisions. THIS SECOND AMENDMENT SHALL BE GOVERNED
BY, AND CONSTRUED IN ACCORDANCE WITH, THE INTERNAL LAW OF THE STATE OF
WISCONSIN. Section headings in this Second Amendment are included for the
convenience of reference only and shall not constitute a part of this Second
Amendment for any other purpose. Whenever possible, each provision of this
Second Amendment shall be interpreted in such a manner as to be effective and
valid under applicable law, but if any provision of this Second Amendment shall
be prohibited by or invalid under applicable law, such provision shall be
ineffective to the extent of such prohibition or invalidity, without
invalidating the remainder of such provision or the remaining provisions of this
Second Amendment. This Second Amendment may be executed in any number of
counterparts and by different parties hereto in separate counterparts, each of
which when so executed and delivered shall be deemed to be an original and all
of which taken together shall constitute one instrument. This Second Amendment
shall be binding upon, and inure to the benefit of, Borrower and Lender and
their respective successors and assigns.

                            [Execution Page Follows]

<PAGE>   8

         IN WITNESS WHEREOF, the parties hereto have caused this Second
Amendment to be executed and delivered by their respective officers thereunto
duly authorized as of the date first written above.

                               LENDER

                               LASALLE BUSINESS CREDIT, INC.

                               By:  /s/ Dale P. Grzenia
                                    ---------------------------------------
                                        Dale P. Grzenia, Vice President

                               BORROWER

                               NEMATRON CORPORATION

                               By:  /s/ David P. Gienapp
                                    ---------------------------------------
                                        David P. Gienapp
                                        Vice President-Finance and
                                        Administration, and Secretary<PAGE>   1

                                                                     EXHIBIT 4.4

                         SECOND AMENDMENT AND WAIVER TO
                           LOAN AND SECURITY AGREEMENT

         THIS SECOND AMENDMENT AND WAIVER (this "Second Amendment"), dated as of
April 12, 2001, to that certain Loan and Security Agreement dated as of June 30,
2000 (as amended by that certain First Amendment dated as of March 1, 2001, the
"Agreement"), is entered into by A-OK CONTROLS ENGINEERING, INC., a Michigan
corporation ("Borrower"), and LASALLE BUSINESS CREDIT, INC., a Delaware
corporation ("Lender"). Capitalized terms used but not otherwise defined herein
shall have the meanings assigned thereto in the Agreement.

                                    RECITALS

         A. Borrower and Lender are party to the Agreement, pursuant to which
Lender has agreed to make, and has made, certain loans, advances and credit
accommodations to Borrower pursuant to the terms and conditions set forth in the
Agreement.

         B. Nematron and Lender are party to the Nematron Loan Agreement,
pursuant to which Lender has agreed to make, and has made, certain loans,
advances and credit accommodations to Nematron pursuant to the terms and
conditions set forth in the Nematron Loan Agreement.

         C. Borrower is a wholly-owned Subsidiary of Nematron and has materially
benefited, and will materially benefit, from the loans, advances and credit
accommodations made, and to be made, to Nematron pursuant to the Nematron Loan
Agreement.

         D. Pursuant to paragraph 14(m)(i) of the Nematron Loan Agreement,
Nematron and its Subsidiaries (including, without limitation, Borrower), on a
consolidated basis, were required at all times to maintain a Tangible Net Worth
plus Subordinated Indebtedness of not less than $1,250,000 during Fiscal Year
ending December 31, 2000, and $2,500,000 during Fiscal Year ending December 31,
2001.

         E. The Tangible Net Worth plus Subordinated Indebtedness of Nematron
and its Subsidiaries, on a consolidated basis, as of June 30, 2000 and each
subsequent calendar month end in the Fiscal Year ended December 31, 2000, and
January 31, 2001 and February 28, 2001, according to the financial covenant
calculations accompanying Nematron's Officer's Certificates, was less than the
applicable required minimum amount referenced in Recital D above, thus
constituting breaches and violations of paragraph 14(m)(i) of the Nematron Loan
Agreement.

         F. Pursuant to paragraph 14(m)(ii) of the Nematron Loan Agreement,
Nematron and its Subsidiaries (including, without limitation, Borrower), on a
consolidated basis, were required to maintain an Interest Coverage Ratio as of
the end of each fiscal quarter for that portion of the Fiscal Year then ended,
commencing with the fiscal quarter ending December 31, 2000, of not less than
1.50 to 1.00.

         G. The Interest Coverage Ratio of Nematron and its Subsidiaries, on a
consolidated basis, for the full Fiscal Year ended December 31, 2000 was 0.44 to
1.00, according to the financial covenant calculations accompanying an Officer's
Certificate of Nematron, thus constituting a breach and violation of paragraph
14(m)(ii) of the Nematron Loan Agreement.

         H. Pursuant to paragraph 14(m)(iii) of the Nematron Loan Agreement,
Nematron and its Subsidiaries (including, without limitation, Borrower), on a
consolidated basis, were required to maintain a Debt Service Coverage Ratio, as
of the end of each fiscal quarter for that portion of the Fiscal Year then
ended, commencing with the fiscal quarter ending December 31, 2000, of not less
than 0.75 to 1.00.

         I. The Debt Service Coverage Ratio of Nematron and its Subsidiaries, on
a consolidated basis, for the full Fiscal Year ended December 31, 2000 was
(1.48) to 1.00, according to the financial covenant calculations accompanying an
Officer's Certificate of Nematron, thus constituting a breach and violation of
paragraph 14(m)(iii) of the Nematron Loan Agreement.

<PAGE>   2

         J. Pursuant to paragraph 14(h) of the Nematron Loan Agreement, Nematron
is prohibited from incurring any indebtedness (other than certain specified
liabilities) or guaranteeing the obligations of any Person without Lender's
prior written consent, and pursuant to paragraph 14(i) of the Nematron Loan
Agreement, Nematron may not create any new Subsidiary (other than certain
specified Subsidiaries) without Lender's prior written consent.

         K. Nematron has acquired (the "Optimation Acquisition") 100% of the
issued and outstanding capital stock ("Optimation Stock") of Optimation, Inc.,
an Alabama corporation ("Optimation"), pursuant to the terms of that certain
Stock Purchase Agreement dated as of March 30, 2001, among Dennis A. Sierk,
Sheila D. Sierk, Charles Garrett, Kerry Garrett (all of the foregoing persons
are "Sellers"), Optimation and Nematron, in the form attached hereto as Exhibit
A (the "Stock Purchase Agreement").

         L. Each breach or violation described in Recitals E, G and I above, and
the lapse of thirty (30) days from the occurrence thereof, constitutes an Event
of Default under paragraph 16(o) of the Agreement, and the breach or violation
described in Recital K above, and the lapse of thirty (30) days from the
occurrence thereof, constitutes an Event of Default under paragraph 16(b) of the
Agreement (each is a "Subject Default").

         M. Pursuant to paragraph 2 of the Agreement, following the occurrence
and during continuation of an Event of Default, Lender may cease making any
further Loans, in addition to Lender's other remedies under the Agreement.

         N. Borrower has requested that Lender waive the Subject Defaults, and
Lender is willing to do so subject to the terms and conditions set forth in this
Second Amendment.

                                    AGREEMENT

         NOW, THEREFORE, in consideration of the premises and for other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, Borrower and Lender agree as follows:

1.       AMENDMENTS TO THE AGREEMENT.

         1.1 Paragraph 12. Clauses (a) and (b) of Paragraph 12 of the Agreement
are hereby amended and restated to read, in their entirety, as follows:

             (a) This Agreement shall be in effect from the date hereof
         until November 12, 2003 ("ORIGINAL TERM") and shall automatically renew
         itself from year to year thereafter (each such one year renewal being
         referred to herein as a "RENEWAL TERM") unless (i) the due date of the
         Liabilities is accelerated pursuant to paragraph 17 hereof; (ii) both
         Borrower and Nematron elect, or LaSalle elects, to terminate both this
         Agreement and the Nematron Loan Agreement at the end of the Original
         Term or at the end of any Renewal Term by giving the other parties
         written notice of such election at least sixty (60) days prior to the
         end of the Original Term or the then current Renewal Term, in which
         case Borrower and Nematron shall pay all of the Liabilities in full on
         the last day of such term; or (iii) both Borrower and Nematron elect to
         terminate both this Agreement and the Nematron Loan Agreement at any
         other time during the Original Term or any Renewal Term upon not less
         than sixty (60) days' prior written notice to the other parties, in
         which case Borrower and Nematron shall pay all of the Liabilities in
         full on the date specified in such written notice. If one or more of
         the events specified in subparagraphs (i), (ii) or (iii) occurs, this
         Agreement shall terminate on the date thereafter on which the
         Liabilities are paid in full; provided, however, that the security
         interests and liens created under this Agreement, the Nematron Loan
         Agreement and the Other Agreements shall survive such termination until
         the date upon which payment and satisfaction in full of the Liabilities
         shall have occurred. At such time as Borrower and Nematron have repaid
         all of the Liabilities and both this Agreement and the Nematron Loan
         Agreement have been terminated, (A) Borrower shall deliver to LaSalle a
         release, in form and substance reasonably satisfactory to LaSalle, of
         all obligations and liabilities of LaSalle and its officers, directors,
         employees, agents, parents, subsidiaries and affiliates to Borrower,
         and if Borrower is obtaining new financing from another lender,
         Borrower shall deliver such lender's indemnification of LaSalle, in
         form and substance reasonably satisfactory to LaSalle, for checks which
         LaSalle has credited to Borrower's account, but which subsequently are
         dishonored for

<PAGE>   3

         any reason and, (B) LaSalle shall deliver to Borrower a release in form
         and substance reasonably satisfactory to Borrower.

             (b) If this Agreement is terminated prior to the end of the
         Original Term, Borrower agrees to pay to LaSalle, as a prepayment fee,
         in addition to the payment of all other Liabilities owing by Borrower,
         an amount equal to: (i) two percent (2%) of the Loan Commitment if this
         Agreement is terminated during the first year of the Original Term;
         (ii) one percent (1.0%) of the Loan Commitment if this Agreement is
         terminated during the second year of the Original Term; (iii) one
         percent (1.0%) of the Loan Commitment if this Agreement is terminated
         during the third year of the Original Term; and (iv) one-half of one
         percent (0.50%) of the Loan Commitment if this Agreement is terminated
         on or after November 12, 2002; provided, however, that such prepayment
         fee shall not be payable if this Agreement is terminated (A) at the end
         of the Original Term pursuant to the terms set forth herein, or (B) at
         any other time by LaSalle if no Default or Event of Default shall have
         occurred and be continuing, or (C) by the Borrower following the
         issuance of any Capital Adequacy Demand, or (D) by the Borrower
         following the merger of LaSalle with and into, or the sale of
         substantially all of LaSalle's assets to, any Person which is not an
         Affiliate of LaSalle and where LaSalle is not the surviving entity, or
         (E) by the Borrower following any sale, assignment, transfer or other
         disposition by LaSalle of its rights under this Agreement and the Other
         Agreements (other than a participation interest herein or therein) to
         any Person other than an Affiliate of LaSalle; provided, further, that
         any such prepayment fee shall be waived if Borrower refinances all
         Liabilities with Standard Federal on or after December 31, 2001. In
         light of the extreme difficulty of accurately calculating actual
         damages arising out of any early termination, LaSalle and Borrower have
         agreed that the prepayment fee provided for above is a reasonable
         estimate of actual damages that would be incurred.

         1.2 Paragraph 14(p). Paragraph 14(p) of the Agreement is hereby amended
and restated to read, in its entirety, as follows:

             (p) Borrower shall not enter into or be a party to, or permit
         any Subsidiary to enter into or be a party to, any transaction with any
         Affiliate of Borrower except in the ordinary course of business for
         fair consideration and on terms no less favorable to Borrower or such
         Subsidiary as are available from unaffiliated third parties. Accounts
         related to sales of products or services performed among the Borrower
         and any Subsidiaries or among any Subsidiaries shall be due and payable
         within thirty (30) days after the stated invoice date or date of
         delivery or performance, whichever is earlier;

2.       WAIVER. Lender hereby waives the Subject Defaults, effective as of
December 31, 2000.

3.       REPRESENTATIONS AND WARRANTIES. To induce Lender to enter into this
Second Amendment and to temporarily continue to make available Loans pursuant to
Section 2 above, Borrower represents and warrants to Lender that:

         3.1 Organization and Existence. Borrower is duly organized and validly
existing under the laws of the State of Michigan. Borrower has filed all annual
reports required to be filed on or before the date hereof with the Secretary of
State of Michigan. Borrower has not filed nor authorized the filing of, articles
of dissolution with the Secretary of State of Michigan.

         3.2 Authority, Authorization and Enforceability. Borrower has the
requisite power and authority to execute and deliver this Second Amendment and
to perform its obligations hereunder and under the Agreement as amended hereby.
Borrower has duly authorized the execution and deliver of this Second Amendment
and the performance of its obligations hereunder and under the Agreement as
amended hereby. This Second Amendment and the Agreement as amended hereby are
the legal, valid and binding obligations of Borrower and are enforceable against
Borrower in accordance with their respective terms.

         3.3 No Violation of Law or Contract. Borrower's execution and delivery
of this Second Amendment, and Borrower's performance of its obligations
hereunder and under the Agreement as amended hereby, does not and shall not
conflict with the provisions of any statutes, regulation, ordinance or rule of
law, or any agreement, contract or other document binding on Borrower.

         3.4 No Default, Event of Default or Material Adverse Effect. After
giving effect to the waiver set forth in Section 2 hereof, (a) no Default or
Event of Default has occurred or is continuing, and (b) no Material Adverse
Effect has occurred since the Closing Date.

<PAGE>   4

         3.5 General Representations and Warranties Remade. Except as expressly
identified herein, all representations, warranties and covenants made as of the
Closing Date pursuant to the Agreement are hereby remade as of the date of this
Second Amendment.

4.       GENERAL.

         4.1 Expenses. Borrower agrees to pay Lender, on the date hereof and
from time to time hereafter upon demand, all expenses, including reasonable
attorneys' and legal assistants' fees, incurred by Lender in connection with the
preparation, negotiation and execution of this Second Amendment and any document
required to be furnished herewith.

         4.2 Entire Agreement. This Second Amendment, the Agreement as amended
hereby, and all of the Other Agreements constitute the entire agreement of the
parties with respect to the subject matter hereof and supersede all other
understandings, oral or written, with respect to the subject matter hereof.

         4.3 Effect of Amendment; No Waiver. Except as expressly amended
pursuant to Section 1 hereof, the Agreement and the Other Agreements shall
remain in full force and effect and are hereby ratified and confirmed in all
respects. EXCEPT AS EXPRESSLY SET FORTH IN SECTION 2 HEREOF, THIS SECOND
AMENDMENT SHALL NOT OPERATE AS A WAIVER OF ANY RIGHT, POWER OR REMEDY OF LENDER
UNDER THE AGREEMENT OR ANY OF THE OTHER AGREEMENTS, AND LENDER RESERVES ALL
RIGHTS AND REMEDIES (INCLUDING, WITHOUT LIMITATION, RIGHTS AND REMEDIES ACCRUING
OR EXISTING BY REASON OF THE SUBJECT DEFAULTS).

         4.4 Miscellaneous Provisions. THIS SECOND AMENDMENT SHALL BE GOVERNED
BY, AND CONSTRUED IN ACCORDANCE WITH, THE INTERNAL LAW OF THE STATE OF
WISCONSIN. Section headings in this Second Amendment are included for the
convenience of reference only and shall not constitute a part of this Second
Amendment for any other purpose. Whenever possible, each provision of this
Second Amendment shall be interpreted in such a manner as to be effective and
valid under applicable law, but if any provision of this Second Amendment shall
be prohibited by or invalid under applicable law, such provision shall be
ineffective to the extent of such prohibition or invalidity, without
invalidating the remainder of such provision or the remaining provisions of this
Second Amendment. This Second Amendment may be executed in any number of
counterparts and by different parties hereto in separate counterparts, each of
which when so executed and delivered shall be deemed to be an original and all
of which taken together shall constitute one instrument. This Second Amendment
shall be binding upon, and inure to the benefit of, Borrower and Lender and
their respective successors and assigns.

                            [Execution Page Follows]

<PAGE>   5

         IN WITNESS WHEREOF, the parties hereto have caused this Second
Amendment to be executed and delivered by their respective officers thereunto
duly authorized as of the date first written above.

                                  LENDER

                                  LASALLE BUSINESS CREDIT, INC.

                                  By:  /s/ Dale P. Grzenia
                                       ---------------------------------------
                                           Dale P. Grzenia, Vice President

                                  BORROWER

                                  A-OK CONTROLS ENGINEERING, INC.

                                  By:  /s/ David P. Gienapp
                                       ---------------------------------------
                                           David P. Gienapp
                                           Vice President-Finance and
                                           Administration, and Secretary

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