Catalogue
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Marconi Radio Valve Type DEV, by Marconi Company, England, c. 1923
Inventory Number: 83921
Date: c. 1923
Maker Details: Signed by Marconi's Wireless Telegraph Co. Ltd.
Inscription: "MARCONI'S W. T. CO. LTD. / MADE IN ENGLAND / COVERED BY VARIOUS PATENTS / D.E.V. / 1430 BBC [LOGO]" printed on exterior surface of bulb.
Size: 70 mm in overall length
Materials: Glass, steel, assorted metals.
Other Given Number(s): Christie's 210.
Notes:
Marconi Radio Valve Type DEV (Dull Emitter V), with grid and anode connections as side pips on envelope, and single strand tungsten filament running entire length with spring for tensioning. Construction was co-axial with helical wire grid surrounding filament and fitting within cylindrical anode. In thin glass envelope half painted red, with envelope caps at either ends. BBC logo ('TYPE APPROVED BY THE POSTMASTER GENERAL') was used from 1st November 1922 until September 1924, and is a good indication of the date of origin. Previously catalogued with assorted other valves.
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