SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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



                                 SCHEDULE TO - C

            TENDER OFFER STATEMENT UNDER SECTION 14(d)(1) OR 13(e)(1)
                     OF THE SECURITIES EXCHANGE ACT OF 1934


                                ONIX Systems Inc.
                       ---------------------------------
                       (Name of Subject Company (Issuer))

                    Thermo Instrument Systems Inc. (Offeror)
               Thermo Electron Corporation (Affiliate of Offeror)
               --------------------------------------------------
         (Names of Filing Persons (Identifying Status as Offeror, Issuer
                                or Other Person))

                          Common Stock, $.01 par value
                          ----------------------------
                         (Title of Class of Securities)

                                   67088G 10 8
                                   -----------
                      (CUSIP Number of Class of Securities)

                             Seth H. Hoogasian, Esq.
                                 General Counsel
                         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 Filing Persons)

                            CALCULATION OF FILING FEE

- --------------------------------------------------------------------------------
Transaction Valuation*                  Amount of Filing Fee
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
Filing relates solely to preliminary                                  None.
communications made before the
commencement of a tender offer.
- --------------------------------------------------------------------------------

* Set forth the amount on which the filing  fee is  calculated  and state how it
was determined.






[ ]  Check  the  box if any  part  of the  fee is  offset  as  provided  by Rule
0-11(a)(2)  and identify the filing with which the offsetting fee was previously
paid. Identify the previous filing by registration statement number, or the Form
or Schedule and the date of its filing.

Amount Previously Paid: _____________

Form or Registration No.: _____________

Filing Party: ________________________

Date Filed:  _________________________

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

Check the  appropriate  boxes below to designate any  transactions  to which the
statement relates:

[X] third-party tender offer subject to Rule 14d-1.

[   ]  issuer tender offer subject to Rule 13e-4.

[X] going-private transaction subject to Rule 13e-3.

[   ] amendment to Schedule 13D under Rule 13d-2.

Check the following box if the filing is a final amendment reporting the results
of the tender offer: [  ]




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




             Thermo Electron Announces Progress on Company Reorganization



WALTHAM,  Mass.,  March 6, 2000 - One month  following  its  announcement  of an
ambitious plan to simplify the company and focus solely on its core  measurement
and detection  instruments  business,  Thermo  Electron  Corporation  (NYSE-TMO)
announced  today that it has initiated the first steps required to take three of
its subsidiaries private.

      On  Friday,   the  company's  Thermo  Instrument  Systems  Inc.  (ASE-THI)
subsidiary filed with the Securities and Exchange Commission (SEC) the materials
necessary  to take its Thermo  Optek  Corporation  and  ThermoQuest  Corporation
businesses private through short-form mergers.  The SEC must complete its review
of these materials before the mergers can be finalized.  Thermo Electron expects
these mergers to be completed in the second quarter of 2000.

      In addition,  the company  announced  that its Thermedics  Inc.  (ASE-TMD)
subsidiary  has commenced its  previously  announced cash tender offer of $15.50
per  share  for  any and all  outstanding  shares  of its  Thermo  Sentron  Inc.
business.  The offer and withdrawal  rights will expire at midnight on Thursday,
March 30, 2000, unless the offer is extended.

      The goal of the tender offer is to bring Thermedics' and Thermo Electron's
combined  equity  ownership  in  Thermo  Sentron  to at  least  90  percent.  If
Thermedics and Thermo Electron achieve this  90-percent-ownership  level, Thermo
Sentron would then be spun into Thermedics through a "short-form"  merger at the
same cash price as the tender offer.  Thermedics expects to complete the spin-in
of Thermo  Sentron in the second  quarter of 2000.  The tender  offer for Thermo
Sentron and  proposed  subsequent  short-form  merger  require SEC  clearance of
necessary filings.  The short-form merger would not require Thermo Sentron board
or shareholder approval.

      Thermo  Electron is  pursuing  an  aggressive  timetable  to complete  its
reorganization  plan and expects to commence tender offers for Metrika  Systems,
ONIX Systems,  Thermo  BioAnalysis,  and Thermedics  Detection over the next two
weeks.

      Thermo  Electron  Corporation  is a leading  provider  of  analytical  and
monitoring instruments used in a broad range of applications, from life sciences
research to  telecommunications  to food and beverage  production.  In addition,
Thermo  Electron  serves  the  healthcare  market  through a family  of  medical
products,  and is a major  producer  of paper  recycling  systems  and  provides
water-clarification  and fiber-recovery  products and services.  As announced on
January 31, 2000,  the company has initiated a major  reorganization  that would
transform it into one publicly traded entity focused on its core measurement and
detection  instruments  business.  The  company's  medical  products  and  paper
recycling   businesses  will  be  spun  off  as  dividends  to  Thermo  Electron
shareholders.    More    information   is   available   on   the   Internet   at
http://www.thermo.com.



Other Important Information:
The tender offers described in this  announcement for the outstanding  shares of
Thermedics  Detection,  Metrika  Systems,  ONIX  Systems and Thermo  BioAnalysis
common stock have not yet commenced.  As soon as the tender offers commence,  we
will file tender offer  statements with the Securities and Exchange  Commission.
You should read the tender offer statements when they become  available  because
they will contain important  information about the tender offers. You can obtain
the  tender  offer  statements  and  other  documents  that are  filed  with the
Securities  and  Exchange  Commission  for free on the  Securities  and Exchange
Commission's web site at http://www.sec.gov. If you write us or call us, we will
send you these documents for free when they are available:

      o Tender Offer Statements (except for exhibits)
      o Offers to Purchase
      o Letters of Transmittal
      o Notices of Guaranteed Delivery

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

      Investor Relations Department
      Thermo Electron Corporation
      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: the company's  spinout and  acquisition  strategies,
competition, international operations, technological change, possible changes in
governmental regulations,  capital spending and government funding policies, and
dependence on intellectual property rights.


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