C_Osram

Is also named "Air Force C-Valve".

Since the Museum search system allows only criteria of two or more digits we name all single digit valves/tubes with an appended underline. Therefore you can search C_ to get all single digit "C"-tubes.

This is a "hard" tube made by Osram GEC for the Royal Air Force, first made in September 1918. Also later made by Ediswan. The Ediswan version had the "four pillar" glass stem. This tube was sometimes branded Royal Ediswan.
The British Military inter-service tube base IS-1 was developed early in 1918 by Captain Stanley R Mullard as part of his work at HMS Hero, a reaearch facility of the British Navy in Portsmouth, England. The base consisted of a moulded ebonite "cup", 31 mm diameter with a centre contact for one end of the tube filament. The other end was connected externally by a copper strip about 3 mm wide. The anode and grid connections were made with two brass plates 7 mm square and on either side of the base, near the rim. The anode plate was identified by a red dot.The design of the base was to reduce internal capacitance between the electrodes. The base was used on at least 12 other tube types.

C_Osram: Fin Stewart Fin Stewart		C_Osram: Banneitz, TB der drahtl. Teleph. 1927 Anonyme 15 Collectionneur

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