Control Unit C-4, of ARN-7 Automatic Radio Compass, for Parts or Repair
Here is a WWII-era Control Unit for the ARN-7 Automatic Radio Compass system used for direction finding and homing. The receiver function tunes from 100-1750 kHz across 4 bands, which were selected by rotating the center knob below the frequency band window. The center knob rotates a flexible shaft connected to a rotatable loop antenna.
The ARN-7 system (see diagram), were one of several generations of radio navigational systems installed in an aircraft such as the heavy bomber B-24 Liberator, B-17 Flying Fortress, B-29 Superfortress, and medium bombers and transport aircraft.
The unit is in reasonable cosmetic condition and all mechanical features appear to operate. The rear panel is absent, see photos. It is missing the small lamps for the frequency display and the tuning meter display, plus the spares, see photos. Measures ~8 inches square by 4 inches deep (including tallest knob).