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                        [ATTACHMENT A TO PROXY STATEMENT]



                                  FORM OF PROXY

                               THERMO VOLTEK CORP.
   
      PROXY FOR SPECIAL MEETING OF STOCKHOLDERS TO BE HELD MARCH 25, 1999
    
          THIS PROXY IS SOLICITED ON BEHALF OF THE BOARD OF DIRECTORS
   
     The undersigned hereby appoints Colin I.W. Baxter, John W. Wood Jr. and
Kenneth J. Apicerno, or any one of them in the absence of the others, as
attorneys and proxies of the undersigned, with full power of substitution, for
and in the name of the undersigned, to represent the undersigned at the Special
Meeting of the stockholders of Thermo Voltek Corp., a Delaware corporation (the
"Company"), to be held on March 25, 1999, at 10:00 a.m., at the offices of
Thermo Electron Corporation, 81 Wyman Street, Waltham, Massachusetts 02454-9046,
and at any adjournment or adjournments thereof, and to vote all shares of common
stock of the Company standing in the name of the undersigned on February 11, 
1999, with all of the powers the undersigned would possess if personally present
at such meeting.
    
            (IMPORTANT--TO BE SIGNED AND DATED ON THE REVERSE SIDE.)


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                         SPECIAL MEETING OF STOCKHOLDERS
                               THERMO VOLTEK CORP.
                                 MARCH 25, 1999
    
     1. To consider and vote on a proposal to approve an Agreement and Plan of
Merger dated as of November 24, 1998 (the "Merger Agreement") pursuant to which
TV Acquisition Corporation, a newly-formed company and wholly owned subsidiary
of Thermedics Inc., will be merged (the "Merger") with and into the Company and
each stockholder of the Company (other than stockholders who are entitled to and
have perfected their dissenters' rights, shares held by the Company in treasury
and shares held by Thermedics Inc. and Thermo Electron Corporation) will become
entitled to receive $7.00 in cash, without interest, for each outstanding share
of common stock, $.05 par value, of the Company owned by such stockholder
immediately prior to the effective time of the Merger. A copy of the Merger
Agreement is attached as Appendix A to and is described in the accompanying
Proxy Statement.

            [  ]  For         [  ]  Against         [  ]  Abstain

     2. To consider and act in their discretion upon such other matters as may
properly come before the Special Meeting or any adjournment or adjournments
thereof.

            [  ]  For         [  ]  Against         [  ]  Abstain

     THE SHARES REPRESENTED BY THIS PROXY WILL BE VOTED "FOR" THE PROPOSALS SET
FORTH ABOVE IF NO INSTRUCTION TO THE CONTRARY IS INDICATED OR IF NO INSTRUCTION
IS GIVEN.

     Copies of the Notice of Special Meeting and of the Proxy Statement have
been received by the undersigned.


                                       PLEASE DATE, SIGN AND PROMPTLY
                                       RETURN THIS PROXY IN THE ENCLOSED
                                       ENVELOPE.

                                       Signature(s) ___________________________


                                       Date_____________________________________

                                       Note: This proxy should be dated, signed
                                       by the stockholder(s) exactly as his or
                                       her name appears hereon, and returned
                                       promptly in the enclosed envelope. 
                                       Persons signing in a fiduciary capacity
                                       should so indicate. If shares are held by
                                       joint tenants or as community property,
                                       both should sign.

      PLEASE DATE, SIGN AND MAIL YOUR PROXY CARD BACK AS SOON AS POSSIBLE!