As a cold cathode gas filled voltage regulator the VR150/30 exhibits a near constant voltage drop for currents within the range 5 mA to 40 mA. The regulation is 150 plus or minus 5.5 Volts.
Internally pins 3 and 7 are linked. This shorting link is designed to protect the connected equipment from overload, as when the stabiliser is removed the supplied circuit is disconnected.
The Brimar name (the consumer brand of STC) appears on the base cap as well as Made in England
The construction is of a central anode within a cylindrical cathode with mica discs top and bottom.
The classic envelope is 37 mm in diameter and, excluding the IO base pins, is 91 mm tall.
References: Data-sheet, 1040 & 3002. Type VR150/30 was first introduced in 1939. See also1939 adverts.
