Sensibly equivalent¶ to:
The NT92 is a large directly heated triode for use in radio transmitters. The valve shown is a Western Electric Type 4212E. The NT92 was used in class AB push-pull to provide audio modulation for medium-sized transmitters. The load impedance was quoted as 5 kΩ and would produce 50 Watts in single end configuration.
The red marking is characteristic of valves supplied by Western Electric (USA) and thus 212E. STC in the UK would have made the 4212E in the UK as 4 was their prefix.
The filament is a single thread that passes through the anode cavity five times in a series of inverted 'V's.
The wide glass tube envelope is 84 mm in diameter and, excluding the base pins, is 295 mm tall.
References: Datasheet & 1043.
Absolute Maximum Operating Conditions¶
Updated April 09, 2015. shape:wide.glass.tube construction:pinch type:triode age:1930.1940 base: pins:4 pin:1.a pin:2.g1 pin:3.f pin:4.f