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ID number:  BIRRC-P0374B
Institution:  Research and Cultural Collections
Named collection:  Historic Physics Collection
Artist / Maker:  Believed to be Cossor
Title / Object name:  Lodge diode valve
Object type:  Electronic component
Date made:  c. 1913
Materials:  Glass with metal electrodes on wooden stand
Measurements:  31 x 29 x 12 cm, on wooden base 31 x 17 cm

This valve consists of a large evacuated glass bulb. The top arm leads to a helical cathode filling the centre of the bulb, and the bottom arm supports this cathode without electrical connection. The horizontal arm is the anode. There is no external provision for heating the cathode, which must have been maintained hot by ion bombardment from the residual gas. The valve must have carried quite large currents for some time to produce the brown colouration of the glass by radiation damage.

Inscriptions / Translations:  B’ham. Univ. Physics E442

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