The CV1833 is a cold cathode voltage stabiliser and the CV specification took the OB2 as the prototype. This exhibit also carries the commercial Type designation.
The B7G voltage stabilisers were the last to be developed before semiconductor Zener diodes took over as voltage references. The commercial 0B2 was also used by UK government departments including the BBC and to encourage several manufacturers to make the product a CV (common valve) specification was issued from 1941 onwards.
The regulation of this tube was 3.5 Volts for currents of between 5 and 30 mA. So the voltage across this tube in service would have been held at between 106 and 110 volts. The striking voltage was 133 volts.
The STC logo and Made in England. The SV- stands for stabiliser valve.
The 0B2 for zero heater volts can be read as OB2. Construction is as a central rod anode and cylindrical cathode. The image shows the anode connected to pin 5.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 56 mm tall.
References: Data-sheet & 1040. Type CV1833 was first introduced in 1957. See also1957 adverts.
