Control Unit, C-149/ARN-6 Radio Compass System B-36 Here is an example of

Here is an example of a Speedometer of the type used in the WWII-era US Army M-4 Sherman Medium Tank

but the stamped service date is illegible

in an audio frequency signal the average frequency of which is proportional to the altitude of the aircraft above the ground

and the course knob is a little stiff but turns 360 degrees

Control Unit, C-149/ARN-6 Radio Compass System B-36 Here is an example ofThis is a terrific example of a C 149 Control unit for the aircraft receiver R 101 of the Radio Compass AN ARN 6 system 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 AN ARN 6 system evolved over time, originally using a control box similar