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                                                                  EXHIBIT 10(jj)


                            AMENDMENT NO. 4 TO FOURTH
                AMENDED AND RESTATED LOAN AND SECURITY AGREEMENT

         THIS AGREEMENT is made and entered into as of the 1st day of January,
1998 among NOVAMETRIX MEDICAL SYSTEMS INC., a Delaware corporation having its
principal office at 5 Technology Drive, Wallingford, Connecticut 06492
("Novametrix"); NTC TECHNOLOGY INC., a Delaware corporation having its principal
office in Wilmington, Delaware with a mailing address in care of 5 Technology
Drive, Wallingford, Connecticut 06492 ("NTC"), and FIRST UNION NATIONAL BANK, a
national banking association having an office at 205 Church Street, New Haven,
Connecticut 06510 (the "Lender"), as AMENDMENT NO. 4 TO THE FOURTH AMENDED AND
RESTATED LOAN AND SECURITY AGREEMENT dated as of June 16, 1994 by and among
Novametrix, NTC and Union Trust Company (the "Fourth Loan Agreement").

                                   WITNESSETH:

         WHEREAS, Novametrix, NTC and Union Trust Company executed the Fourth
Loan Agreement on June 16, 1994; and

         WHEREAS, subsequent thereto, Union Trust Company changed its name to
First Fidelity Bank; and

         WHEREAS, Novametrix, NTC and First Fidelity Bank executed Amendment No.
1 to the Fourth Amended and Restated Loan and Security Agreement on July 26,
1995; and

         WHEREAS, subsequent thereto, First Fidelity Bank changed its name to
First Union Bank of Connecticut; and

         WHEREAS, Novametrix, NTC and the Lender executed Amendment No. 2 to the
Fourth Amended and Restated Loan and Security Agreement as of October 25, 1996;
and

         WHEREAS, Novametrix, NTC and First Union Bank of Connecticut executed
Amendment No. 3 to this Fourth Amended and Restated Loan and Security Agreement
as of April 25, 1997; and


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         WHEREAS, subsequent thereto, First Union Bank of Connecticut was merged
into First Union National Bank; and

         WHEREAS, the parties now wish to amend and modify the Fourth Loan
Agreement and the Substituted Revolving Note (as defined therein) issued
thereunder: (i) to change the interest rate payable on the 1997 Substituted
Revolving Note, and (ii) to reduce the fees payable on account thereof:

         NOW, THEREFORE, the parties agree as follows:

         1. Amendments to the Definitions of Certain Terms: (i) The definitions
of each of the following terms, as set forth in the Fourth Loan Agreement, as
heretofore amended, are hereby amended and restated to read as follows:

         1.78 "RELATED DOCUMENTS" means the Allonge No 1 to 1997 Substituted
         Revolving Note and every other document executed by Borrower or NTC in
         connection with the Loans or otherwise in connection with the Fourth
         Loan Agreement as amended by Amendment No. 1 and as amended by
         Amendment No. 2, and as amended by Amendment No. 3, and as amended by
         Amendment 4.

         1.82 "REVOLVING CREDIT INTEREST RATE" has the meaning set forth in
         Section 3.7 of the Fourth Loan Agreement, as amended by Amendment No.
         4.

         1.93 "SUBSTITUTED REVOLVING NOTE" shall, unless the context otherwise
         requires, mean and refer to the 1997 Substituted Revolving Note as
         amended by the Allonge No. 1 to 1997 Substituted Revolving Note.

                  (ii) The term "1997 SUBSTITUTED REVOLVING NOTE" shall have the
meaning accorded to it in Section 3.6 of the Fourth Loan Agreement as amended by
Amendment No. 4.

                  (iii) All other capitalized terms used herein which are not
defined herein shall have the meaning accorded to them in the Fourth Loan
Agreement as heretofore amended.

         2. Amended Terms Pertaining to Revolving Credit: The following
subsections of Section 3 of the Fourth Loan Agreement, as heretofore amended
entitled "Revolving Credit", are hereby amended and restated to read as follows:

         3.6 REVOLVING CREDIT NOTE. The obligation of Borrower and NTC to repay
         the Revolving Credit and all Advances thereunder shall be evidenced by
         an amended and restated promissory note (the "1997 Substituted
         Revolving Note") substantially in the form of Exhibit 3.6 (1997)
         attached to Amendment No. 3 and dated as of April 25, 1997, as modified
         by the Allonge No. 1 to 1997 Substituted Revolving Note, substantially
         in the form of Exhibit 3.6-a (1998) attached to Amendment No. 4 to Loan
         Agreement and 


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         executed by the Borrower, NTC and the Lender concurrently with
         Amendment No. 4 to Loan Agreement.

         The 1997 Substituted Revolving Note shall for all purposes be treated
         as having been issued in substitution for, and not in repayment or as a
         refunding of, the 1996 Substituted Revolving Note executed by the
         Borrower and NTC in favor of Lender in the face principal amount of
         $3,500,000 dated October 25, 1996.

         3.7 INTEREST RATE. Interest shall accrue on the aggregate principal
         amount of all Advances outstanding under the Revolving Credit from time
         to time at the rate set forth in the 1997 Substituted Revolving Note as
         modified by Allonge No. 1 to 1997 Substituted Revolving Note (the
         "Revolving Credit Interest Rate"); provided that following an Event of
         Default the applicable interest rate shall be the Default Interest
         Rate. Interest shall be calculated on the basis of a 360 day year for
         the actual number of days elapsed. Each adjustment to the Revolving
         Credit Interest Rate shall result immediately, without notice or demand
         of any kind, in a new rate of interest effective with respect to the
         interest period on and after the date of such adjustment.

         3.12 FACILITY FEE. The amount by which the Maximum Principal Amount
         exceeds the average daily aggregate principal balance outstanding under
         the Revolving Credit is hereinafter referred to as the "Unused Amount."
         Borrower and NTC shall pay to Lender a fee in the amount of one-eighth
         of one percent (1/8%) per annum on the Unused Amount for each calendar
         year quarter (or partial quarter in the event that this Agreement
         commences on any day other than the first day of a calendar year
         quarter or terminates on any day other than the last day of a calendar
         year quarter), such fee to be payable in arrears on the first day of
         each calendar year quarter commencing on April 1, 1998. Such fee shall
         be deemed fully earned by Lender as of the last day of each calendar
         year quarter or partial quarter, as the case may be, with respect to
         which the payment of such fee accrues.

         3. Reaffirmation of Representations and Warranties: Novametrix and NTC
hereby restate and reaffirm, as of the date hereof, the representations and
warranties set forth in Section 7 of the Fourth Loan Agreement, except that the
representations and warranties set forth in Section 7.9 shall be deemed to apply
to the most current set of financial information provided to the Lender, and
except as otherwise set forth on Schedule I hereto.

         Novametrix and NTC each hereby represent and warrant to the Lender that
there exists no Event of Default or Incipient Default as of the date hereof.

         4. Waiver of Claims, Defenses, Etc.: As of the date hereof, Novametrix
and NTC represent that there exist no defenses, offsets, counterclaims,
reductions, set-offs or diminutions of any kind or nature whatsoever of or to
any of the obligations of the Borrower or NTC under the Fourth Loan 


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Agreement, as heretofore amended, or under any of the Related Documents, or
otherwise, or to any of the rights of Lender in and to any such obligations, or
to, under or by reason of the Fourth Loan Agreement, as heretofore amended, this
Amendment No. 4, or any other Related Document, or otherwise, and there exists
no claims, rights, or other assertions of liability against Lender or any
Affiliate, Subsidiary, officer, director, employee, agent or attorney of Lender
on account of any of the actions taken by Lender or any such Person to date
under or in connection with the Fourth Loan Agreement, as heretofore amended,
the Notes, the Related Documents, or in connection with the transactions
contemplated by the Fourth Loan Agreement, as heretofore amended, the Notes, the
Related Documents or otherwise.

         By execution of this Amendment No. 4, each of Novametrix and NTC hereby
waives all claims, actions and causes of action which have arisen or may arise
against Lender or any of its Affiliates, Subsidiaries, successors or assigns,
under or in connection with any of the transactions contemplated by the Fourth
Loan Agreement, as heretofore amended, or the Related Documents or any other
loan document or agreement between the Lender and Novametrix and/or NTC, or
otherwise, in respect of any matter, cause or thing arising or occurring prior
to the date hereof.

         5. Reaffirmation of Existing Agreements: The Fourth Loan Agreement, as
heretofore amended, and the Related Documents, except to the extent expressly
herein modified, are hereby ratified and affirmed and shall be and remain in
full force and effect.

         6. Counterparts: This Amendment No. 4 to the Fourth Loan Agreement may
be executed in counterparts, each of which shall be deemed an original, but all
of which taken together shall constitute one and the same instrument.


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         Dated as of the date and year first above written.

Signed, sealed and delivered
in the presence of:                    NOVAMETRIX MEDICAL SYSTEMS INC.

/s/_______________________

/s/_______________________             By/s/____________________________________
                                            Name:  William J. Lacourciere
                                            Title:


                                       NTC TECHNOLOGY INC.
/s/_______________________

/s/_______________________             By/s/____________________________________
                                            Name:  Thomas M. Haythe
                                            Title: President


                                       FIRST UNION NATIONAL BANK
/s/______________________

/s/______________________              By/s/____________________________________
                                            Name:  John H. Frost
                                            Title: Vice President


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