From Mary Bellis,
Your Guide to Inventors.
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A vacuum tube also called a electron tubes is a sealed glass or metal-ceramic enclosure used in electronic circuitry to control the flow of electrons between the metal electrodes sealed inside the tubes. The air inside the tubes is removed by a vacuum. Vacuum tubes are used for: amplification of a weak current, rectification of an alternating current to direct current (AC to DC), generation of oscillating radio-frequency (RF) power for radio and radar, and more.

According to PV Scientific Instruments, "The earliest forms of such tubes appeared in the late 17th century. However, it was not until the 1850s that sufficient technology existed to produce sophisticated versions of such tubes. This technology included efficient vacuum pumps, advanced glassblowing techniques, and the Ruhmkorff induction coil."

Timeline

• In 1875, American, G.R. Carey invented the phototube.
• In 1878, Englishman Sir William Crookes invented the 'Crookes tube', an early prototype of cathode-ray tube.
• In 1895, German, Wilhelm Roengten invented an early prototype Xray tube.
• In 1897, German, Karl Ferdinand Braun invents the cathode ray tube oscilloscope.
• In 1904, John Ambrose Fleming invented the first practical electron tube called the 'Fleming Valve'. Leming invents the vacuum tube diode.
• In 1906, Lee de Forest invented the audion later called the triode, an improvement on the 'Fleming Valve' tube.
• In 1913, William D. Coolidge invented the 'Coolidge Tube', the first practical Xray tube.
• In 1920, RCA began the first commercial electron tube manufacturing.
• In 1921, American Albert Hull invented the magnetron electronic vacuum tube.
• In 1922, Philo T. Farnsworth develops the first tube scanning system for television.
• In 1923, Vladimir K Zworykin invented the iconoscope or the cathode-ray tube and the kinescope.
• In 1926, Hull and Williams co-invented the tetrode electronic vacuum tube.
• In 1938, Americans Russell and Sigurd Varian co-invented the klystron tube.