the first-digit filament/heater power rating confusingly gathers valves of widely-differing ratings. the 2g21 is a subminiature triode-hexode, with a maximum anode (plate) current of some 0.2 milliamps and a maximum voltage of 45 volts. the 2j42 magnetron, with a power output of some 7 kilowatts, is rated for anode current of 4.5 amps (pulse peak) at anode voltage of 5,500 volts.