The G240/2D is a cold cathode Thyratron. When conducting the voltage drop across the valve is 90 Volts. The discharge is initiated by a voltage on the trigger electrode.
The KB/F identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the F identifies the maker as STC, Paignton.
The reverse carries the service code of CV2174 and the KB/F maker code.
The concentric rings for the inner trigger and outer cathode. The rod anode is sheaved in glass for most of the length.
The envelope spoils this attempt to show the root of the anode rod.
The wide glass tube envelope is 29 mm in diameter, and excluding the IO base pins, is 74 mm tall.
Reference: Data-sheet. Type G240/2D was first introduced in 1949. See also1949 adverts.
