SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                 -------------------



                                 SCHEDULE 14D-9



          SOLICITATION/RECOMMENDATION STATEMENT UNDER SECTION 14(d)(4)
                     OF THE SECURITIES EXCHANGE ACT OF 1934



                                 Thermedics Inc.
                                 ---------------
                            (Name of Subject Company)

                                 Thermedics Inc.
                                ---------------
                      (Name of Person(s) Filing Statement)


                          Common Stock, $.10 par value
                          ----------------------------
                         (Title of Class of Securities)


                                   883901 10 0
                                   -----------
                      (CUSIP Number of Class of Securities)

                             Seth H. Hoogasian, Esq.
                         c/o Thermo Electron Corporation
                                 81 Wyman Street
                        Waltham, Massachusetts 02454-9046
                                 (781) 622-1000
 (Name, Address, and Telephone Number of Person Authorized to Receive Notices
        and Communications on Behalf of the Person(s) Filing Statement)


[X] Check the box if the filing  relates  solely to  preliminary  communications
made before the commencement of a tender offer.








Investor Contact: 781-622-1111
Media Contact: 781-622-1252


                          Thermedics Exchange Ratio Set



WALTHAM,  Mass., March 8, 2000 - Thermedics Inc. (ASE-TMD)  announced today that
its parent company, Thermo Electron Corporation (NYSE-TMO),  has set an exchange
ratio of 0.45 shares of Thermo Electron common stock for each Thermedics  share,
and is  proceeding  with  its  previously  announced  plan to take  the  company
private.

      Thermo  Electron  expects to conduct  the  exchange  offer for any and all
outstanding  Thermedics shares held by minority  shareholders  during the second
quarter of 2000. Thermo Electron  currently owns  approximately  75.7 percent of
the  outstanding  shares  of  Thermedics  common  stock and will  condition  the
exchange offer on receiving  acceptances  from holders of enough shares so that,
when combined  with its current share  ownership,  Thermo  Electron's  ownership
reaches   at   least   90   percent.    If   Thermo   Electron   achieves   this
90-percent-ownership threshold, it will acquire all remaining outstanding shares
of Thermedics  common stock through a  "short-form"  merger.  In the  short-form
merger, minority shareholders who do not participate in the exchange offer would
also receive 0.45 shares of Thermo  Electron  common stock in exchange for their
Thermedics shares.

      Obligations under Thermedics'  2.88% convertible  subordinated  debentures
due June 1, 2003,  and its 0%  convertible  subordinated  debentures due June 1,
2003,  would be assumed by Thermo  Electron in the  short-form  merger,  and the
debentures would be convertible into Thermo Electron common stock.

      The  exchange  offer and proposed  subsequent  short-form  merger  require
Securities and Exchange Commission  clearance of necessary filings; a short-form
merger would not require Thermedics board or shareholder approval.

      If Thermo Electron  successfully  obtains ownership of at least 90 percent
of the outstanding  Thermedics shares, it expects to complete the spin-in by the
end of the second quarter of 2000.

      Thermedics Inc. develops, manufactures, and markets diverse product lines,
including  implantable  heart-assist  devices  and  other  biomedical  products,
security  instruments,  and equipment that assures the quality of a wide variety
of consumer  products and bulk materials.  Thermedics is a public  subsidiary of
Thermo Electron  Corporation.  More  information is available on the Internet at
http://www.thermo.com/subsid/tmd1.html.

Other Important Information:
      The  exchange  offer that is described  in this  announcement  has not yet
      commenced.   Once  the   exchange   offer   commences,   we  will  file  a
      solicitation/recommendation  statement  with the  Securities  and Exchange
      Commission  (SEC). You should read this document when it becomes available
      because it will contain  important  information  about the exchange offer.
      You  can  obtain  the  solicitation/recommendation   statement  and  other
      documents that will be filed with the SEC for free when they are available
      on the SEC's web site at http://www.sec.gov. Also, if you write us or call
      us, we will send you the  solicitation/recommendation  statement  for free
      when it is available.


                                     -more-


You can call us at (781) 622-1111 or write to us at:

      Investor Relations Department
      Thermedics Inc.
      81 Wyman Street, P.O. Box 9046
      Waltham, MA 02454-9046


The following constitutes a "Safe Harbor" statement under the Private Securities
Litigation  Reform Act of 1995:  This  press  release  contains  forward-looking
statements that involve a number of risks and  uncertainties.  Important factors
that could cause actual  results to differ  materially  from those  indicated by
such forward-looking statements are set forth under the heading "Forward-looking
Statements"  in Exhibit 13 to the  company's  annual report on Form 10-K for the
year ended January 2, 1999. These include risks and  uncertainties  relating to:
government  regulation and industry  standards,  competition  and  technological
change,  intellectual  property  rights,  reimbursement  by insurers for medical
procedures,  medical  community  acceptance of medical devices,  availability of
materials and components,  product liability,  international operations, and the
company's spinout and acquisition strategies.

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