The BTH 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 Type designation appears on both side of the envelope.
The screening cage hides the inner structure.
The wide glass tube envelope is 38 mm in diameter and, excluding the B4 base pins, is 95 mm tall.
Reference: Data-sheet. Type BD78 was first introduced in 1952. See also1952 adverts.
