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Round Radio Valve Type CA, by Ediswan, London, c. 1915

Inventory Number: 35122

35122-1t 35122-2t

Date: c. 1915

Maker Details: Attributed to Ediswan.

Inscription: "SINGLE FIL. / MARCONI'S W. T. CO., LTD / PAT. APPN. NO. 28413-13 / 2V-PF" printed on exterior surface of bulb.

Size: 170 mm in overall length

Materials: Glass, oxide, platinum, asbestos, brass, ebonite.

Other Given Number(s): Christie's 206.


Round Triode Radio Valve Type CA (production model), with oxide-coated platinum filaments as indicated by the PF (Platinum Filament) printed on the exterior surface of the glas bulb. This receiver valve, a variant of Type N, was completely surrounded by a coarse mesh grid and cylindrical anode. The tubulation at the top of the valve contained a piece of asbestos that could be heated to release a small amount of gas into the valve to optimise its operation. With brass and ebonite base.

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