1908 DEFOREST SINGLE WING SPHERICAL AUDION – DUAL FILAMENT

Description

DEFOREST SINGLE WING SPHERICAL AUDION – DUAL FILAMENT
This is the version of the spherical Audion in which there is 1 plate and 1 grid. This places this example into the 1908 time period. In 1909 they began making these tubes with 2 plates and 2 grids.
There are however, 2 filaments. The filaments in these tubes were so delicate that in order to extend the life of the tube, 2 filaments were provided. When the first filament gave out, the operator could shift the filament connection to a separate wire that protruded from the screw base. Both filaments are burnt out.
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