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vacuum tube

vacuum tube

A vacuum tube is a device that relies on the flow of an electric current through a vacuum. Vacuum tubes (thermionic valves) were widely used in electronic devices such as televisions, radios and computers until the invention of the transistor.
The basic idea of a vacuum tube is that a current passes through the filament, which then heats it up so that it gives off electrons. The electrons are negatively charged and are attracted to the small positive plate (or anode) within the tube. A unidirectional flow is thus established between the filament and the plate. Thomas Edison had observed this while investigating the reason for breakage of lamp filaments. He noted an uneven blackening (darkest near one terminal of the filament) of the bulbs in his incandescent lamps and noted that current flows from the lamp's filament and a plate within the vacuum.
The first generation of computers used several thousand bulky vacuum tubes, with several racks of vacuum tubes taking up the space of a large room. The vacuum tube used in the early computers was a three-terminal device, and it consisted of a cathode, a grid and a plate. The vacuum tube was used to represent one of two binary states: i.e. the binary value 'O' or 'l'.
The filament of a vacuum tube becomes unstable over time. In addition, if air leaks into the tube, then oxygen will react with the hot filament and damage it. The size and unreliability of vacuum tubes motivated research into more compact and reliable technologies. This led to the invention of the transistor in the late 1940s.
The first generation of digital computers all used vacuum tubes: e.g. the Atanasoff-Berry computer (ABC) developed at the University of Iowa in 1942: the Colossus developed at Bletchley Park in 1944; ENIAC developed in the United States in the mid-1940s; UNIVAC I developed in 1951; Whirlwind developed in 1951; and the IBM 701 developed in 1953.
(Introduction to the History of Computing: A Computing History Primer, By Gerard O'Regan)
vacuum tube Reviewed by encywiki on March 27, 2019 Rating: 5 vacuum tube A vacuum tube is a device that relies on the flow of an electric current through a vacuum. Vacuum t...

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