S-phone

S-phone, British device developed by SOE, which was used by resistance groups in occupied Europe to communicate with friendly aircraft, or by commandos raiding the French coast. It was also employed to guide supply aircraft to resistance dropping zones. The aircraft (or ship, or submarine) carried the master set, the other, which could be packed into a suitcase, was carried by the agent or commando. The S-phone's theoretical range when used as a radio-telephone was about 65 km. (40 mi.) by air and 24 km. (15 mi.) by sea, these distances being almost doubled when it was used as a navigational device. Transmissions to an aircraft could not be picked up by ground detectors more than 1,500 m. (5,000 ft.) from the point of transmission, and it was therefore relatively safe to use (see Figure ).

The Americans developed a similar, more advanced, much smaller device called ‘Joan-Eleanor’ which was used by agents belonging to the Office of Strategic Services who penetrated into Germany during the last months of the war. ‘Joan’ was carried by the agent, ‘Eleanor’ by the aircraft. Any conversation could be recorded aboard the aircraft on a spool of wire, an early form of tape recorder.See also radio communications.