This consists of a flat rectangular metal box provided with a socket which fits the plug at the bottom of the radio receiver and transmitter' BC-222 or BC-322, several binding posts, and Il battery cable. It is designed to provide means of connecting separate batteries to the set ill case there is no battery BA-32 available. and to facilitate the insertion of meters in the several circuits. The batteries aI'S connected by means of the cable, all leads of which are identified by stamped metal markers. TIle binding posts, four on either side, serve to provide ~ady connection of meters to indicate microphone current, relay current, plate current, and plate voltage.