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Round Radio Valve Type CA, by Ediswan, London, c. 1915
Inventory Number: 13117
Number of documents: 2
Document Type: Miscellaneous Note
Document Heading: Manufacturer Details - Ediswan
Text:
Ediswan, the trade name of the Edison and Swan United Electric Light Company Limited, made this valve for Marconi's Wireless Telegraph Co. Ltd. Joseph Swan, a Briton, and Thomas Edison, the famous American inventor jointly founded the company, as a result of the major court battle they fought over who was the original inventor of the electric light bulb. The company produced all the Marconi valves up to 1919, manufactured at them at their factory in Ponders End, North London.
Some Ediswan valves were marked 'Royal Ediswan' up to 1923.
Document Type: Miscellaneous Note
Document Heading: Historical Background
Text:
The Round Type 'CA' valve was one of a series of soft triode valves developed in 1914 by Captain H J Round of the Marconi Company. The excellent performance of these valves, which at the time far exceeded that of any other available triodes enabled the Marconi Company, in 1914, to develop their 'Short Distance Wireless Telephone Transmitter and Receiver' which achieved a range of more that 50 miles. In spite of the difficulties in manufacturing valves with consistent characteristics, production continued until well after the end of World War 1. Round valves were also used in early aircraft wireless telephony equipment.
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