Control Unit C-4, of ARN-7 Automatic Radio Compass, B-17, B-24, B-29

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 tuning knob is broken but a replacement knob can probably be found. Measures ~8 inches square by 4 inches deep (including tallest knob).