RTX mod. AN/URC-4 - (U.S.A. 1952) - Rescue portable radio set utilized by USAF pilots from Corea conflict; in case of throwing down the pilot ask for help, and an helicopter start to find it. The RTX operate in two fixed frequency: 121,5 and 243 MHz (also today those are the normal S.O.S. aircraft frequency). In the equipment are employed 7 subminiature valves (4) 6050, (2) 6147, (1) 2E32 and a 7 pin soket miniature 3Q4. Power supply by battery: 1,4 and 90 V. For the time it was a jewel of miniaturization. The battery pack visible in the photo is home made, and contain an tension elevator to make 90 V for valves anode.