VLS631 / CV342
Top quality miniature glass thermal delay tubes manufactured for the British military in England by renowned International Telephone and Telegraph (ITT). The heater takes a defined time to heat a bi-metallic strip and make contact; used to delay application of HT voltages until tube heaters are at correct temperatures. Tubes are marked in blue ITT VLS631 MADE IN ENGLAND and date stamped 7036 indicating 1970 production. Boxes are white military marked STC VLS631 VALVE ELECTRONIC MADE IN ENGLAND.