Radio Control Box BC-938-A as used in SCR274 System

This is a WWII or post war era BC-938A Radio Control box as used in aircraft of the US military with the SCR274 communication system.  The box was installed in the aircraft cockpit and connected to the aircraft's centrally-installed radio transmitters.  It is very similar to the BC-602 box used with the SCR-522 Command Radio System.

When depressed, the buttons configured the communication system as desired by the operator (pilot or co-pilot). Buttons A,B,C,D applied to specific communication channels, which when depressed, select the channel desired to transmit and receive. The OFF button disconnected the channels. The purpose of buttons 1 and 2 are unknown.

The TONE-CW-VOICE switch selected the type of transmission desired. In the VOICE position, voice is transmitted when the push-to-talk button on the control wheel is pressed. In the CW position, a continuous wave, or un-modulated signal, will be transmitted. In the TONE position, a modulated tone signal is transmitted. When the switch is in the TONE or CW position, the microphones are inoperative and signalling by code is accomplished by a key (e.g., morse code key).  Range is most limited on VOICE and greatest on CW. 

The MIC jack is for the microphone, and the KEY jack is for a manually-operated key.  

Measures 3 inches by 3 inches by 4.25 inches. All switches function mechanically. Electrical function unknown.  It is in good condition given its age.