The CV1731 neon voltage stabiliser is on a B4 base and is a design progression from the Cossor S130 that dates from the mid 1930's. The valve was specified by the GPO and thus also known as the POSV2.
The striking voltage is 160 V and the burning current is from 6 to 75 mA. Within the current range the regulation is 5 volts.
The KB/K identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the K identifies the maker as ETEL, Electronic Tubes, High Wycombe.
The cathode cylinder with supports either side.
The cylinder is closed at the top.
The balloon envelope is 50 mm in diameter and, excluding the B4 base pins, is 100 mm tall.
