Fleming Oscillation Valve

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



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