Audion_BTH-E12

The E12 based Audion was made for the British Military and given the Admiralty Pattern no 5997. The tube was made for a few months in 1916 and had an unanchored single "M" shaped filament. This was wide to cover the anode area. It was a double ended tube with plate and grid leads coming from the top of the tube, in a recessed area. (this was identical to the de Forest Audion of the time and it is possible that these tubes were imported by BTH and rebranded with the BTH logo before the company had perfected their own tube manufacture). The BTH logo is on one side of the bulb and volts and the AP number are on the other side. Difficulty was encountered with the tube design. Tyne's "Saga of the Vacuum Tube" mentions the tube on page 215 but has a drawing of the tube showing that all wires came from the top end, with the filament wires externally coming around the bulb to the bottom, to the E12 base. It has not been confirmed but was quite likely that the tube was used in the British Military Mark III Short Wave Tuner, along side a "White" valve.

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