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History of Automation: The Triode Vacuum Tube the Evolution into Automation, Industrial, and Machine Control

In 1904, Sir John Ambrose Fleming invented the two-electrode vacuum-tube rectifier, which he called an “oscillation valve”. He received a U.S. patent on November 16, 1904. The device also had other names: Thermionic Valve, based on the principle of the thermionic electron emission from the hot cathode; the Vacuum Diode, based on the fact that the electrodes were suspended and operated in a partial vacuum, and the operation of the device only allowed current to flow in one direction (diode operation); the kenotron, from “kenosis” (emptying) & “electron”; a Thermionic Tube (American word for British “valve”); and the Fleming Valve or Fleming Oscillation Valve. At the time of discovery, it was not understood that the valve could be useful for rectification, and Fleming’s intent was simply to create an oscillator. Early radio reception was accomplished by the use of “crystal sets” or “cat whisker radios” and this valve pioneered the movement into more sensitive and effective instruments. Continue reading