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 red marking is characteristic of valves supplied by Western Electric (later STC).

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.

This exhibit was last updated on 06 February 2003