How did early air-defence control and identification develop as radar arrived?
Short answerIFF developed through successive transponder systems, with Britain's Chain Home network creating an immediate need to identify friendly aircraft.
NotesIdentification friend or foe developed through successive transponder systems. The British Mark I active transponder is dated to 1939, with German equipment following in 1940. The American chronology is less certain: early work around 1940 preceded contact with the British system during the Tizard Mission and equipment introduced in 1942. Another generation of systems followed by 1948. A transponder combines a transmitter and responder: it receives an interrogation signal and automatically emits an identifying reply. Designers must also prevent those replies from making aircraft too easy to detect or undermining security. Britain's Chain Home network created an immediate need to distinguish friendly aircraft across a national radar system, which helped drive investment in IFF.