filament current

The rheostat R controlled the filament current, and in these early sets was used as a volume control.

The latter is fed through the coil of a relay which starts the vibrator when filament current is drawn.

The overall tube current, conduction current, and filament current were all tested under varying input voltages.

The grid and filament control module can provide an isolated filament current of up to 15A at 6V and a grid bias voltage of 1200V.