The White valve like the Round valves were soft valves. That is they operated with a low pressure gas to obtain sensitivity. The physical size of these valves was dictated by the need to maintain a correct ratio of gas to electrode size for proper operation.
The band round the base reads: 'White valve developed by G W White, Cavendish Lab under J J Thompson 1917', however Tyne1047 dates the White valve to 1916. The White valve was used in the Mark III Amplifier which was designed by the UK Signals Experimental Establishment for field use and was first made in April 1917. The amplifier used two valves the second being a De Forest Audion. At the same time the French TM hard valve was proving to be a better choice for military communications. The gain was less but the characteristics were more stable and less skill was needed in their operation. Subsequently the British made over 100,000 R Type valves, directly equivalent to the TM.
The grid connection is via the base shell with the filament connected by the base studs. The anode connects to the top cap.
The filament is oxide coated platinum wire. The grid appears to be a perforated copper disc. The anode is a bright disc.
The electrods side view showing the inter-electrode spacing.
A close-up of the grid and filament.
A spot of green corrosion on the grid suggests copper as the metal.
The top cap anode connection and screw stud for the connecting wire.
The base cap with the later addition of a plastic label.
The balloon envelope is 60 mm in diameter, and including the base is 150 mm tall.
Reference: 1047. Type White was first introduced in 1916.