Radio ВС-458-A

B17 ВС-458-A - Aircraft communications transmitter, part of SCR-274-N. 5.3…7.0 MHz, A1 / A3, 40 W output. Powered by DM-33 dynamotor installed on BC-456 modulator unit. WHD = 184 х 224 х 382 mm. Weight - 3.8 kg. 

The "Type K Command Radio" had been developed in 1936/37 as a modular communications system for Aircraft use (with separate receivers for separate wavebands, separate transmitters, control boxes and accessories),  and had been tested and improved for military use from 1939 on. In 1940, the U.S. Navy started  installing the equipment as RAT / RAV sets and the U.S. Army Air Corps introduced the equipment as SCR-274-N after May 1940.