Transmitting triode introduced by M.O. Valve Company prior to 1922. The 'Marconi' brand did not come into use until 1925 and the relatively low serial number (797) suggests that this example was probably made around 1926. This type was still in the catalogue in 1936. 12.5 volt directly heated cathode (pure tungsten).

Physical Description

Spherical bulb with cylindrical ends and an exhaust tip on its side. Three flying leads come out of one end cylinder (filament and grid connections) and one flying lead comes out of the other one (the anode connection). All the leads are insulated by small glass beads. The bulb is heavily darkened from use.

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