"S-phone Type 13/mkiii Ws 13/3 1943"
The S-Phone, the Resistance's virtually undetectable telephone. In order to carry out parachute drops or "pick-ups" (dropping off or taking charge of clandestine Resistance agents), a direct link between the plane and the ground team is essential. Designed by the Special Operations Executive (British secret services), the device serves as a radio telephone, a guidance beacon and a drop point indicator. Bilateral communication is carried out as with an ordinary telephone. This allows agents to use the S-Phone (8.6 kilos) with a minimum of instructions. It is virtually undetectable by German radio direction-finding systems, and is also used to communicate with ships and submarines from the coast.