Sensibly equivalent¶ to:
The VR21 is a battery low frequency triode as supplied to the Royal Air Force. The R indicates a receiving valve. When the Common Valve system was introduced in 1941 the VR21 was renamed the CV1021
The reverse of the envelope.
The balloon envelope is 41 mm in diameter and, excluding the B4 base pins, is 83 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+