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Valves and Tubes
On Sun, 6 Aug 2006 21:11:01 -0400, "Al"
wrote: wrote in message ... Why do some people call Tubes,Valves? cuhulin Originally named Fleming's valve, after the inventor of the vacuum tube. Al Like most cool ****, there was no single inventor. ''Though the thermionic emission effect was observed as early as 1873, it is Thomas Edison's 1883 investigation of the "Edison Effect" that is the best known. He promptly patented it (U.S. Patent 307031), but as the particle nature of the electron was not known until 1897, he did not understand the process. [edit] Diodes and triodes John Ambrose Fleming had worked for Edison; in 1904, as scientific adviser to the Marconi company, he developed the "oscillation valve" or kenotron. Later known as the diode, it allowed electric current to flow in only one direction, enabling the rectification of alternating current. Its operation is described in greater detail in the previous section. In 1906 Lee De Forest placed a bent wire serving as a screen between the filament and plate electrode, later known as the "grid" electrode. As the voltage applied to the grid was varied from negative to positive, the amount of electrons flowing from the filament to the plate would vary accordingly. Thus the grid was said to electrostatically "control" the plate current. The resulting three-electrode device was therefore an excellent and very sensitive amplifier of voltages. DeForest called his invention the "Audion". In 1907, DeForest filed U.S. Patent 879532 for a three-electrode version of the Audion for use in radio communications. The device is now known as the triode. De Forest's device was not strictly a vacuum tube, but clearly depended for its action on ionisation of the relatively high levels of gas remaining after evacuation. The De Forest company in its Audion leaflets warned against operation which might cause the vacuum to become too hard. The first true vacuum triodes were the Pliotrons developed by Irving Langmuir at the General Electric research laboratory (Schenectady, New York) in 1915. These were closely followed by the French 'R' Type which was in widespread use by the allied military by 1916. These two types were the first true vacuum tubes.'' -wikipedia |
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