Radio Set SCR-506 is a medium power,amplitude-modulated set made up of Radio Receiver BC-652, Radio Transmitter BC-653, and certain additional operating components. It is designed for installation in tanks, amphibian trucks, personnel carriers, and other vehicles to provide continuous wave (cw) and voice communication from one wehicle to another or between these vehicles and airplanes or base station. The pricipal feature of Radio Transmitter BC-653-A is the speed and ease with which changes of frequency can be made. Five channels can be preset of the transmitter. The operator can select any one of these preset channels by means of a switch on the front panel of the transmitter. Radio Receiver BC-652-A is designed for the reception of voice or cw signals and incorporates a crystal frequency calibrator as frequency standard.