John Ambrose Fleming3
(1849 - 1945) |
The Fleming
Oscillation Valve was the first practical application of the Edison
Effect (The emission of electrons by a heated element) used as a vacuum
tube rectifier and detector. It was invented by J.A. Fleming in 1904 and
was the major influence on the development of wireless telegraphy and
telephony. The Fleming Valve is considered by most wireless historians to
be the grandfather of the modern Triode vacuum tube.
See the diagram at right. The valve
consists of an incandescent electric lamp comprising a filament (F) of
carbon, tungsten, or other material which can be made incandescent by an
electric current. Around the filament, but not touching it, is a cylinder
of metal (C). The electrical connection to the cylinder is brought out
through the side of the glass enclosure.
The Valve
operates as a simple rectifier when a positive charge is applied to terminal
(T). Electrons emitted from the filament pass through the vacuum of the
valve and are collected by the metal cylinder. 2
This is the Fleming Oscillation valve that I have in
my collection. It dates from about 1910. |
Photographs of the Oscillation Valves first employed by
Dr. J.A. Fleming in October, 19041
|
Bibliography
1"The Thermionic Valve and it's developments
in Radiotelegraphy and Telephony" J.A. Fleming. 1919 The Wireless
Press, LTD.
2 "Harmsworth's Wireless Encyclopedia",
Volume 2. Harmsworth Encyclopedias, London
3 "Gernsback's Radio Encyclopedia" Sidney
Gernsback, New York |
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