 Another change was due to every part of the equipment having different power requirements . The tubes for the transmitter used 6 V to heat their filaments , but 4 V was needed for the receiver tubes and 2 V for the filament of the CRT . The CRT also needed 800 V for its electron gun , but the transmitter tubes 1000 V for their modulators ( drivers ) . At first , the team used motor @-@ generator sets placed in the Anson and Battle fuselages , or batteries connected in various ways as in the earliest sets in the <unk> . Bowen decided the solution was to build a power supply that would produce all of these DC voltages from a single 240 V 50 Hz supply using transformers and rectifiers . This would allow them to power the radar systems using mains power while the aircraft were on the ground . 
