GT1C / CV1128 / NGT2 triode thyratron

This valve measures 114x45mm overall and has a 5-pin base.

This thyratron found many uses as a timebase for radars, and in particular many were used in the Colossus computer which was used a Bletchley Park to crack the codes of the German Lorenz cipher machines. See http://www.codesandciphers.org.uk/lorenz/index.htm, http://www.codesandciphers.org.uk/lectures/ieee.txt and http://www.codesandciphers.org.uk/virtualbp/vcolossus/colossus.htm for further information.

Below: CV1128

Above: GT1C; below: NGT2 (also marked GT1C)