Exhibit 21 THERMO POWER CORPORATION SUBSIDIARIES As of November 19,1998, the Registrant owned the following subsidiaries: STATE OR JURISDICTION PERCENT OF NAME OF OWNERSHIP INCORPORATION NuTemp, Inc. Illinois 100 Peek plc Scotland 100 Peek Data Limited England 100 Peek Group Services Limited England 100 Dubilier Warminster Limited England 100 International Resistance Co Limited England 100 Minicircuits Limited England 100 Peek International Limited England 100 Peek Corporation Delaware 100 Peek Traffic Inc. Delaware 100 Peek Traffic Systems Inc. Florida 100 Saratec Measurement Inc. Florida 100 Signal Control Company Delaware 100 Signal Maintenance, Inc. Delaware 100 Peek Traffic USA Inc. Florida 100 Peek Traffic GmbH Germany 100 Peek International B.V. Netherlands 100 Peek Projects BV Netherlands 100 Peek Promet doo Croatia 100 Peek Traffic A.B. Sweden 100 Peek Trafikk AS Norway 100 Peek Parking Systems AB Sweden 100 Peek Trafik a-s Denmark 100 Peek Traffic B.V. Netherlands 100 Peek Projects B.V. Netherlands 100 Peek Limited Hong Kong 100 Peek Trafikk Sendirian Bermad Malaysia 100 Peek Traffic (Thailand) Limited Thailand 100 Sichuan Modern Control System Engineering Company Limited China 41* Peek Traffic OY Finland 100 Peek Investments, Limited England 100 Dubilier America, Inc. Delaware 100 Automatic Connector Inc. New York 100 Peek Systems Limited England 100 Sotwell Limited England 100 Peek Technology Limited England 100 Peek Traffic Limited England 100 GK Instruments Limited England 100 Sarasota Traffic Limited England 100 Streeteramet Limited England 100 Weighwrite Limited England 100 Radley Services Limited England 100 Atest Electronics Limited England 100 Bartsign Limited England 100 Greenpar Holdings Limited England 100 Helvetia Automatic Products Limited England 100 Peek Field Services Limited England 100 Peek Traffic Systems B.V. Netherlands 100 Radley (1) Limited England 100 Smartways Limited England 100 Tollstar Limited England 100 Takepine Limited United Kingdom 100 Tecogen Securities Corporation Massachusetts 100 ThermoLyte Corporation Delaware 78** Optronics, Inc. Oklahoma 100 * Joint Venture/Partnership ** As of 10/03/98