Exhibit 21 THERMO VOLTEK CORP. Subsidiaries of the Registrant At February 28, 1997, the Registrant owned the following companies: State or Jurisdiction Registrant's % Name of Incorporation of Ownership ------------------------------------------------------------------------ Comtest Europe B.V. The Netherlands 100% Comtest Instrumentation, B.V. The Netherlands 100% Comtest Italia S.R.L. Italy 100% Comtest Limited United Kingdom 100% TVL Securities Corporation Delaware 100% UVC Realty Corp. New York 100%