The VR105 is RAF designation code for the 0C3 cold cathode voltage stabiliser. The design has several names, the VR105/30 included.
The basic operation conditions are contained in the 105/30 of the alternate type code. This tube will stabilise the voltage across it to 105 Volts for output currents between 5 mA and 40 mA. To strike the tube the voltage must exceed 135 V.
As with all such stabilisers the voltage will vary slightly with the current drawn. For this stabiliser the figure is 4 Volts across the current range. For making a stabilised power supply the reference tube would be run at as close as possible to a constant current. For general use the circuit designer would try to minimise the variation on load on the stabiliser.
The 0C3 designation appears on the base cap as well as the glass.
The American VT-200 for vacuum tube 200, the Hytron name and Made in USA. The maker clearly expected the hyphen to be present in VR-105 whereas the UK valve receiving 105 is free of the dash.
The classic envelope is 38 mm in diameter and, excluding the IO base pins, is 88 mm tall.
References: Data-sheet & 1040. Type VR105 was first introduced in 1939. See also1939 adverts.
