Stone Vintage Radio Museum - Antique Radios, Wireless, Crystal Sets, Tubes, and Valves

The Fleming Valve was the first commercial application of the Edison Effect (The flow of electrons through space by a heated element) used as a vacuum tube rectifier and detector. J.A. Fleming developed the tube in 1904. The Fleming Valve is by most accounts the grandfather of the modern vacuum tube. It functions as a rectifier when a positive charge is applied. Electrons emitted from the filament pass through the vacuum of the tube and are accumulated at the metal plate (or anode). It is hard to estimate how many of these Fleming valves are still in existence. One knowledgable authority suggested that there were about 60 in the US, about 30 in the U.K. and about 20 or so elsewhere. Pictured below are three different Fleming Valves. You see two different shapes of glass enclosures. The valve on the left has one plate and the other two have two plates. I assume that the single plate is an earlier version of the valve. The valve on the right has an intact carbon filament.

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