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This is a version of the Type R made by Ediswan. Most later Ediswan Rs for the domestic market were tubular and gettered, and were sold as Type AR. In order to fit the electrodes into a tubular glass envelope no wider than the base cap it was necessary to redesign the structure in a vertical format. This exhibit exemplifies only the first stage of the redesign process and probably comes from a batch intended to test the new filament tensioning system 'under field conditions' (ie by selling them to unsuspecting customers and waiting to see whether anyone screamed. The Type AR version sold well and survives in some quantity although rarely with filament intact.

Thanks to Nick Bray for supplyong the image of the valve and also the photographs of its box.

The balloon envelope is 55 mm in diameter, and excluding the B4 base pins, is 94 mm tall.

References: Private correspondence & ¹⁰⁰³ Type R Type was first introduced in 1916. See also 1916 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶