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                                                                 Exhibit 10.2(k)
February 4, 1997

Ms. Keryn Cerbone
120-28 Prospect Street
Ridgefield, CT 06877

Dear Keryn:

This letter supersedes the offer letter sent to you on January 27, 1997. We are
pleased to offer you the position of Controller with TN Technologies Inc.,
reporting to Michael Bogacki

We have considered the challenge and opportunity offered by working in a fast
paced environment and believe you will be more than able to meet the goals of TN
Technologies Inc. In accepting a position With the Company, you agree that the
employment relationship between the Company and you is an at-will relationship
and that the employment and compensation can be terminated, with or without
cause, and with or without notice, at any time, at the option of either the
Company or you.

The following confirms the specific agreements regarding your compensation if
you accept this position of Controller at TN Technologies Inc

     .    Your annual salary on your start date will be $120,000.

     .    When you start at TN Technologies Inc-, or when TN Technologies files
          an IPO, whichever comes later, and subject to approval by the Board of
          Directors of TN Technologies, you will receive stock options with a
          market value at the date of grant of $72,000- If you should terminate
          employment with TN Technologies Inc., voluntarily or involuntarily,
          prior to the actionable dates of any of the options, the amounts due
          to you will be forfeited.

     .    You will be eligible for 16 vacation days at the completion of your
          first year of employment- In addition you are eligible for 2 personal
          days and 2 floating holidays each year.

     .    You will be eligible for a merit bonus to the same extent all other
          TNTI employees are eligible. Such bonus is dependent upon your
          performance, the overall financial performance of the Company, is at
          the discretion of the Company's senior management, and in 1997 will be
          prorated based upon your tenure with the Company.

     .    After completion of one year's employment with the Company, if you
          should be involuntarily terminated solely due to a change in the
          Company's senior management, you will be eligible for the following
          severance:

                Termination in year 2 of employment - 3 months' severance.
                Termination in year 3 of employment - 2 months' severance.
                Termination in year 4 of employment - 1 month's severance.

TN Technologies Inc. has a thirty-five (35) hour work week, Monday through
Friday. The workday can be flexed between 7:00 a.m. and 7:00 p.m. The
responsibilities that are associated with the Controller position are such that
it may require the investment of additional time to successfully meet deadlines
and demands

Keryn, we are looking forward to your joining TN Technologies Inc. and playing a
key role in our continued success. Please acknowledge your acceptance by signing
the copy of your offer letter and confidentiality agreement and returning to me
in the enclosed envelope. If you have any questions or concerns, please give me
a call.

Best Regards

/s/ Marilyn L. Fidler

                                             Accepted By: /s/ Keryn M. Cerbone
                                             Date: February 4, 1997

         cc: Greg Blaine, Mike Bogacki, G.M. O'Connell