Exhibit 21 THERMO POWER CORPORATION Subsidiaries of the Registrant At November 19, 1997, Thermo Power Corporation owned the following companies: State or Registrant's Jurisdiction % of Name of Incorporation Ownership --------------------------------------- ---------------- ------------ NuTemp, Inc. Illinois 100% Peek plc Scotland 92 Peek Data Limited England and Wales 100 Peek Group Services Limited England and Wales 100 Dubilier Warminster Limited England and Wales 100 International Resistance Co Limited England and Wales 100 Minicircuits Limited England and Wales 100 Peek International Limited England and Wales 100 Peek Corporation Delaware 100 Brandt Instruments,Inc. Delaware 100 Peek Traffic USA, Inc. Florida 100 Peek Measurement, Inc. Texas 100 Peek Traffic, Inc. Delaware 100 Polysonics International, Inc. U.S. Virgin Islands 100 Saratec Measurement, Inc. Florida 100 Signal Control Company Delaware 100 Signal Maintenance, Inc. Delaware 100 Transyt Corporation Florida 100 Peek Traffic GmbH Germany 100 Peek International B.V. The Netherlands 100 Peek Traffic AB Sweden 100 Peek Trafik a-s Denmark 100 Peek Trafikk AS Norway 100 Peek Traffic OY Finland 100 Peek Traffic B.V. The Netherlands 100 Peek Fleetlogic B.V. The Netherlands 100 Peek Traffic Projects B.V. The Netherlands 100 Peek Limited Hong Kong 85 Peek Trafikk Sendirian Berhad Malaysia 100 Peek Traffic (Thailand) Limited Thailand 100 Sichuan Modern Control System Engineering Company Limited China 41* PAGE Exhibit 21 THERMO POWER CORPORATION Subsidiaries of the Registrant (continued) State or Registrant's Jurisdiction % of Name of Incorporation Ownership --------------------------------------- ---------------- ------------ Peek Investments Limited England and Wales 100 Dubilier America Inc. Delaware 100 ACI Holdings, Inc. New York 100 Peek Systems Limited England and Wales 100 Sotwell Limited England and Wales 100 Peek Technology Limited England and Wales 100 Peek Measurement Limited England and Wales 100 Peek Environmental Limited England and Wales 100 Sarasota Data Products Limited England and Wales 100 Sarasota Instrumentation Limited England and Wales 100 Peek Traffic Limited England and Wales 100 GK Instruments Limited England and Wales 100 Sarasota Traffic Limited England and Wales 100 Streeteramet Limited England and Wales 100 Weighwrite Limited England and Wales 100 Radley Services Limited England and Wales 100 Atest Electronics Limited England and Wales 100 Bartsign Limited England and Wales 100 Greenpar Holdings Limited England and Wales 100 Helvetia Automatic Products Limited England and Wales 100 Peek Field Services Limited England and Wales 100 Peek Traffic Systems B.V. The Netherlands 100 Radley (1) Limited England and Wales 100 Smartways Limited England and Wales 100 Tollstar Limited England and Wales 100 Takepine Limited United Kingdom 100 Tecogen Securities Corporation Massachusetts 100 ThermoLyte Corporation Delaware 78 * Participating interest