Contactor Unit BC-608-A of RC-96A System Pipsqueak Grumman and one adjustment knob

and one adjustment knob

It consists of a white plastic planisphere with the northern sky on one side and the southern on the other that shows all the stars in the American and the British Air Almanacs

SA-1/ARN-1 was a component of Radio Set AN/APN-1

but measuring the wingspan as the aircraft changed its angles of approach

The front mounting bracket is set in place but not screwed in

Contactor Unit BC-608-A of RC-96A System Pipsqueak Grumman and one adjustment knobHere is an excellent example of the WWII era Contactor Unit BC 608 A, a component of the US Army Air Force's RC 96 A Contactor System intended to work with the the British RAF "Pipsqueak" system. Pipsqueak was a simple radio navigation system used by the British during the early part of World War II. Pipsqueak used an aircraft's voice radio set to periodically send out a 1 kHz tone which was picked up by ground based high frequency direction finding