<PAGE>   1
                                                                   Exhibit 10(4)

                                     SECOND
                              AMENDED AND RESTATED
                          MANAGEMENT SERVICES AGREEMENT
                                       CPS


This Agreement has been executed on May 15, 1998, by and between CPS CAPITAL
LTD., an Ohio limited liability company, whose principal offices are located at
of 1801 East Ninth Street, Suite 1510, Cleveland, Ohio 44114 ("CPS"), and SENTEX
SENSING TECHNOLOGY, INC., an New Jersey corporation, whose principal offices are
located at 553 Broad Avenue, Ridgefield, New Jersey 07657 ("Sentex").


                             PRELIMINARY STATEMENTS:

         A.       CPS possesses a diverse executive management background in
                  manufacturing, distribution and service industries.

         B.       CPS also has direct management experience in Finance,
                  Marketing, Sales, Business Systems, Strategic Planning, and
                  Human Resources and is willing to provide services to Sentex
                  based on this background.

         C.       CPS has made these services available to Sentex.

         D.       Sentex desires to have these services provided by CPS.

         E.       CPS has provided these services to Sentex during fiscal 1997
                  and is due the sum of $196,900 for which it has not yet been
                  paid.

         F.       The parties have agreed that effective December 1, 1998 CPS
                  would reduce its fee to $250,000 per year and that Sentex
                  would pay CPS the unpaid balance of $196,900 or a portion
                  thereof in common shares, without par value, of Sentex
                  ("Common Shares") to the extent permitted under the New Jersey
                  Shareholder Protection Act ("Act").

         G.       The parties have agreed to amend and restate their prior
                  agreement to account for the changes in Preliminary Statement
                  E and F.



<PAGE>   2


Therefore, in consideration of the mutual covenants set forth herein, the
parties hereto agree as follows:

         1. MANAGEMENT SERVICES. Subject to the terms and conditions of this
         Agreement, Sentex hereby retains CPS, as an independent contractor, to
         provide executive management services to Sentex and its subsidiaries
         (collectively the "Sentex Companies"). The nature and extent of the
         services to be provided may vary from time to time as agreed by the
         parties (the "Services"), but shall include:

                  (a)      those services normally provided by the executive
                           officers of a corporation of similar size and
                           diversity including, without limitation, those
                           services normally provided by the Chief Executive
                           Officer, the Chief Operating Officer and Corporate
                           Secretary;

                  (b)      management and oversight of the accounting and
                           financial functions of the Sentex Companies;

                  (c)      management of advertising and promotions for all
                           business segments;

                  (d)      strategic planning;

                  (e)      stockholders relations;

                  (f)      supervision of day to day business operations;

                  (g)      perform those items set forth in the Interim Letter
                           Agreement during the pendency of the Merger
                           Agreement; and

                  (h)      upon the consummation of the Merger, continue to
                           perform the items set forth in the Interim Letter
                           Agreement.

                  The Services will be performed by Robert S. Kendall acting in
                  his capacity as Chairman, President and Treasurer of Sentex
                  and James G. Few acting in his capacity as Vice President,
                  Secretary and Chief Operating Officer of Sentex (collectively,
                  the "Executive Officers") and other CPS employees as, from
                  time to time, may be required to provide the Services to be
                  rendered hereunder. The parties may add, remove or substitute
                  personnel from time to time as they may agree; provided,
                  however, that at all times the Executive Officers shall be
                  elected by the Board of Directors of Sentex and shall hold
                  office until their successors are qualified and chosen.
                  Notwithstanding any of the foregoing to the contrary, the
                  nature and extent of Services to be performed by CPS, through
                  the Executive Officers and other CPS employees, shall in all
                  respects be determined by the Board of Directors of Sentex.

         2. PERFORMANCE OF SERVICES. Notwithstanding that the nature and extent
         of the services will be determined in all respects by the Board of
         Directors of Sentex, the manner in which the Services are to be
         performed and the specific hours to be worked by CPS personnel shall be
         determined in all respects by CPS.

         3. COMPENSATION.

                  (a) Effective December 1, 1997, Sentex will pay a fee to CPS
                  (the "Compensation") at the annual rate of $250,000. The
                  Compensation shall be payable monthly, in advance, 

                                      -2-
<PAGE>   3

                  and due no later than the tenth day of each month.
                  Notwithstanding the foregoing sentence, in the event Sentex
                  shall be unable to pay the fee in accordance with the terms in
                  the prior sentence, Sentex shall pay the fee to CPS as soon as
                  the financial condition of Sentex will permit such fee to be
                  paid and in all events Sentex shall record such a fee as a
                  liability of Sentex. The Compensation includes an allocation
                  of CPS's overhead costs, including, without limitation, rent,
                  utilities, office, clerical, personnel and administrative
                  expenses. The Compensation is subject to change based upon
                  changes in Sentex's business activity; provided, however, any
                  such change will become effective only upon thirty days notice
                  to Sentex and require the written approval of a majority of
                  the members of the Board of Directors of Sentex who are
                  neither an officer nor controlling member of CPS. Upon
                  Termination of this Agreement (as defined in Section 5 hereof)
                  the Compensation shall cease; provided, however, CPS shall be
                  entitled to Compensation for periods or partial periods that
                  occurred prior to Termination and for which CPS has not yet
                  been paid.

                  (b) In exchange for $196,900 of the fiscal 1997 fee that has
                  not been paid, Sentex hereby issues to CPS 5,025,745 Common
                  Shares; provided, however, that in the event is shall have
                  been determined that the number of Common Shares issued to CPS
                  exceeds that number of Common Shares that are permitted to be
                  issued to CPS under Act, then CPS shall return such excess
                  Common Shares to the Company.

         4. EXPENSE REIMBURSEMENT. CPS shall be entitled to reimbursement from
         Sentex for all reasonable "out-of-pocket" expenses incurred in the
         performance of the Services hereunder in accordance with and subject to
         Sentex's regular policies in effect regarding reimbursement of expenses
         and the documentation required in connection therewith.

         5. TERM/TERMINATION. The term of this Agreement shall be for a period
         of one year, to commence on the date hereof, and shall renew,
         automatically, for successive terms of the same duration. This
         Agreement may be terminated, with or without cause, by either party
         upon thirty days written notice of termination to the other party
         ("Termination").

         6. INDEPENDENT CONTRACTOR. It is understood by the parties to this
         Agreement that CPS is an independent contractor to Sentex and nothing
         in this Agreement shall be construed to create an employer/employee
         relationship between any of the Sentex Companies and any of the
         personnel of CPS. The Compensation provided for hereunder includes all
         benefits due or owed to the Executive Officers by CPS, including,
         without limitation, vacation pay, health, life or disability insurance,
         workman's compensation (collective, "Additional Benefits") and the
         Sentex Companies shall incur no responsibility or liability for any
         such Additional Benefits.

         7. ASSIGNMENT. CPS's obligations under this Agreement may not be
         assigned or transferred to any other person, firm, or corporation
         without the prior written consent of Sentex.

         8. CONFIDENTIALITY. CPS acknowledges and agrees that the Sentex
         Companies maintain confidential and proprietary information and trade
         secrets, including, without limitation, discoveries, ideas, inventions,
         drawings, blueprints, manuals, customer and supplier lists and other
         material of a technical, business or fiscal nature (collectively
         "Confidential Information"). CPS agrees not to disclose any
         Confidential Information to third parties unless authorized to do so by
         Sentex in writing, except, however, that CPS may disclose or use such
         Confidential Information in the performance of the Services hereunder.
         The foregoing restriction shall not apply to any information that is in
         the public domain or becomes available to CPS, after the Termination of
         the Agreement, from sources other than Sentex. CPS acknowledges and
         agrees 


                                      -3-
<PAGE>   4

         that disclosures of Confidential Information would cause irreparable
         damage to Sentex and, in the event of breach of this provision, Sentex
         would be entitled to any and all remedies at law and equity including
         temporary and permanent injunctive relief.

         9. COVENANT NOT TO COMPETE. Except as otherwise mutually agreed to by
         the parties, during the Term of this Agreement and for one year
         thereafter, CPS shall not engage, directly nor indirectly, in any
         business that is competitive with the business that is being conducted
         by the Sentex Companies or solicit or attempt to solicit any business
         from any person, firm or entity that was or is a customer or is a
         prospective customer of the Sentex Companies. For the purposes of this
         paragraph, "prospective customer" shall mean a potential customer which
         one of the Sentex Companies has solicited or with whom one of the
         Sentex Companies has had active discussions concerning potential
         business at any time during the Term of this Agreement. CPS
         acknowledges, and agrees that, in the event of the breach of this
         paragraph, Sentex would be entitled to any and all remedies at law and
         equity including temporary and permanent injunctive relief.

         10. INDEMNIFICATION. CPS hereby agrees to indemnify and hold harmless
         Sentex, its successors and assigns, from and against any and all
         claims, investigations, losses, damages, liabilities, actions and
         causes of action including, without limitation, reasonable attorney
         fees and costs of investigation, arising out of any actual violation of
         the Act resulting from the payment by Sentex to CPS of management fees
         that constitutes, in whole or in part, a prohibited "business
         combination" (as defined in the Act).

         11. RETURN OF RECORDS. Upon termination of this Agreement, CPS shall
         deliver all records, notes, data, memorandums, models, and equipment of
         any nature that are in CPS's possession or under CPS's control and that
         are the property or relate to the business of any of the Sentex
         Companies.

         12. NOTICES. All notices required or permitted under this Agreement
         shall be in writing and shall be deemed delivered when delivered in
         person or deposited in the United States mail, postage prepaid,
         addressed as follows:

                  CONSULTANT                     COMPANY

                  CPS Capital Ltd.               Sentex Sensing Technology, Inc.
                  Robert S. Kendall              Robert Kendall
                  President                      President
                  1801 East Ninth Street         1801 East Ninth Street
                  Suite 1510                     Suite 1510
                  Cleveland, Ohio 44114          Cleveland, Ohio 44114

         Such address may be changed from time to time by either party by
         providing written notice to the other in the manner set forth above.

         13. ENTIRE AGREEMENT. This Agreement contains the entire agreement of
         the parties and there are no other promises or conditions in any other
         agreement whether oral or written. This Agreement supersedes any prior
         written or oral agreements between the parties.

         14. AMENDMENT. This Agreement may be modified or amended if the
         amendment is made in writing and is signed by both parties.

                                      -4-
<PAGE>   5

         15. SEVERABILITY. If any provision of this Agreement shall be held to
         be invalid or unenforceable for any reason, the remaining provisions
         shall continue to be valid and enforceable. If a court finds that any
         provision of this agreement is invalid or unenforceable, but that by
         limiting such provision it would become valid and enforceable, then
         such provision shall be deemed to be written, constructed, and enforced
         as so limited.

         16. WAIVER OF CONTRACTUAL RIGHT. The failure of either party to enforce
         any provision of this Agreement shall not be construed as a waiver or
         limitation of that party's right to subsequently enforce and compel
         strict compliance with every provision of this Agreement.

         17. APPLICABLE LAW. This Agreement shall be governed by the laws of the
         State of New Jersey without regard to principles of conflict of laws.

         CPS CAPITAL LTD.                       SENTEX SENSING TECHNOLOGY, INC.


         By: /s/Robert S. Kendall               By: /s/Robert S. Kendall
             Robert S. Kendall, President          Robert S. Kendall, President




                                      -5-