DER MOV MARCONI VALVE, 1922

First Dull Emitter valve with a 2 volt heater of 1922. (DER Dull Emitter Receiver) This was a Derivative of the 'R' type with a thoriated tungsten filament of 0.63 Watts ( 1.8 volts 0.35 amps ) which reduced filament power by a factor of 4.
Developed 1st by the Marconi Osram Valve Company.

A0630