The C-4/ARN-7 is a control unit used to control the ARN-7 Radio Compass set. Each aircraft would have two, one for the pilot and one for the navigator. Control between the two units was achieved by using a relay junction box, type BK-22, and "CONTROL" buttons on each unit to toggle controls.
This unit was packed October 20th, 1944, but was never used. It is currently being used in our ARN-7 Radio Compass Set.