The CV2125 (commercially the BD78) is a directly heated half wave xenon filled rectifier. The maximum reverse voltage is 2,000 Volts and the maximum rectifier current is 500 mA.
like other gas filled rectifiers the voltage drop across the valve when conducting is very low - around 7 Volts. Heating current needs to be applied for at least 20 seconds before the anode is energised - A thermal delay valve would be used.
The CV data-sheet indicates a use in Radar systems.
The KB/S identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the D identifies the maker as AEI, Rugby. This large factory site was sited immediately north of the main line railway. It was one of the original BTH sites.
The outer mesh is part of the anode. The lower supports of the cage are fixed into the hard glass base.
The coil near the base looks to have been the getter holder.
The wide glass tube envelope is 39 mm in diameter and, excluding the B4 base pins, is 92 mm tall.
Reference: Data-sheet. Type CV2125 was first introduced in 1952. See also1952 adverts.
