VT 98A air-cooled power triode, used in radar transmitters, 1939-45 VT 98A air-cooled power triode 1939-1945
G.E.C. type CAT30 Water Cooled Triode, with directly heated Thoriated Tungsten Filament G.E.C. type CAT30 Water Cooled Triode 1955-1970