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Marconi Radio Valve Type DE3, by Marconi Company, London, c. 1923

Inventory Number: 16810

Date: c. 1923

Maker Details: Signed by Marconi-Osram Valves.

Inscription: "MAR____ _____ VALVES" printed on exterior surface of bulb. See Documents other inscriptions.

Size: 105 mm in overall length (including base pins)

Materials: Glass, steel, plastic?, brass?, assorted metals.

Other Given Number(s): Christie's 216.


Marconi-Osram Triode Radio Valve (or Tube) Type DE3, in unmatching plain cardboard carton. With steel-plated plastic? base, and four brass? base pins. The DE3 was a general-purpose dull emitter triode with a very delicate thoriated tungsten filament rated at 2.8V 0.06A. It was one of the first British valves intended for operation from dry batteries but the battery required was a 4.5V 'bell' battery. This was used with a series rheostat adjusted by the user to provide approximately the correct running voltage across the filament terminals. The device could be used as a LF or HF or as a detector. Construction is a vertical anode with the grid and single strand filament fitted co-axially. The grid is a fine wire helix supported on the side with a rod through the whole length of the anode. The interior surface of the bulb is silvered, probably from use. BBC Stamp ("APPROVED BY POSTMASTER GENERAL") was used from 1st November 1922 until September 1924, and is good indication of date of origin.

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