Electronic valve used for detecting radio waves, circa1920; probably an Audiotron manufactured by Cunningham, U. S. A. One of the first electronic valves imported into Australia from America in 1920.
In view of the fact that the label has fallen off this valve and that Audiotron valves were marketed by AWA as "Expanse" valves in Australia, the valve could well be an "Expanse" as it was acquired from AWA.

Physical Description

Paper identifying label appears to have fallen off.

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