CF-185

This tube was developed by De forest for use by the US Navy after America was drawn into World War One late in 1917. The tube was fitted with the special Navy 3 pin base. The bayonet pin is used locking pin and as an additional contact (filament) and the base itself was made of turned black fibre. The grid is fine tungsten wire wound around a glass frame and the anodes are sheet tungsten. To enable the tube to be used in older equipment, a special brass shelled adaptor was available with a Candleabra (E12) base insulated from thhe main shell. Later tubes c. 1923 had a nickel plated UV base. The tube is the first to have used an oxidised filament and it was claimed to have a life of 5000 hours. According to Tyne's "Saga of the Vacuum Tube", page 124, this claim could not be corroborated.

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