The NGT2 thyratron was based on the commercial GT1C and was later known as the CV1128. It was a development of the NGT1 and the NG indicates that this was made for the Royal Navy. The VGT128 was the RAF designation.
This thyratron is from the 1930s and was used in timebases for Radar and television. At a defined grid voltage the valve, will rapidly switch to full conduction. The valve is turned off by reducing the anode voltage. The thyratron is gas filled and can be considered as triggered gas discharges. The precision of construction gives the defined and reproducible operating characteristics. This valve not only has a high peak current but is designed for operation at up to 8,000 pulses per second.
The first computer, Colossus, used these the thyratron as a pulse generator. The operating speed of Colossus was 5,000 cycles per second.
The heater can be seen on the left and the insulated anode lead is on the right.
On the glass is the ellipse containing the commercial Type designation of GTIC.
The classic envelope is 44 mm in diameter and, excluding the B5 base pins, is 105 mm tall.
References: Data-sheet, 1040 & 1043. Type NGT2 was first introduced in 1937. See also1937 adverts.
