Contactor, Master, Type 2. Stores reference 10A/10994. This item was used as part of the IFF system (Identify Friend or Foe) to identify Allied aircraft to ground-based RDF (Radio Direction Finding) radar units. Also known as 'Pipsqueak' this metal cased spring-driven clockwork unit had an escapement movement beating twice per second. This operated an electrical contact ultimately generating a 'friendly' code which could be triangulated in ground radio stations to deduce the aircraft’s position. The given location was then passed on to the relevant Operations Room. Fitted to many aircraft including Spitfires, Hurricanes & Typhoons. The unit is in good order but somewhat soiled. It can be wound and ticks away strongly when started. The attached wiring loom is good but has no plug fitted. The unit is very snugly contained within a dovetail joined wooden case lined with vibration reducing sponge rubber. Good used. Stock code M27428.