Sensibly equivalent¶ to:
The VR21 (later called the CV1021) is a battery triode as supplied to the Royal Air Force. The R indicates a receiving valve.
The directly heated filament is designed to be run from a 2 volt accumulator, and takes the form of a fine wire supported as a double inverted V. The filament is kept under tension when hot by two coiled springs seen at the top of the node assembly.
The filament tension springs are held above the top mica. The filament is a pair of inverted V's.
The balloon envelope is 42 mm in diameter and, excluding the B4 base pins, is 82 mm tall.
References: Datasheet & 1040. Type VR21 was first introduced in 1929.
Absolute Maximum Operating Conditions¶
Updated April 03, 2015. shape:balloon construction:pinch type:triode age:1920.1930 base:b4 heater:2.0v pins:4 pin:1.a pin:2.g1 pin:3.f pin:4.f