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Cathode ray tube

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Cathode ray tube or CRT is the display device used in most computer displays, video monitors[?] and televisions.

Cathode rays are a stream of high-speed electrons emitted from the heated cathode of a vacuum tube. In a video monitor, the electron beam is focused and diverted by electric fields to scan the surface at the opposite end of the vacuum tube which is lined with phosphorescent material. Color displays use phosphors of different colors, closely packed together in strips (in aperture grille designs) or clusters (in shadow mask CRTs). When the high-speed electrons hit the lining, light is emitted. The video signal is used to control the intensity and scanning position of the electron beam to form a video image on the TV screen.

CRTs have a pronounced triode characteristic, which results in significant gamma. In early televisions, screen gamma was an advantage because it acted to compress the screen contrast. The gamma characteristic exists today in all digital video systems. However, in some systems where a linear response is required, as in desktop publishing, gamma correction is applied.

It is likely that technologies such as plasma, liquid crystal displays, and other newer technologies will eventually make CRT based displays obsolete because the new designs are less bulky and consume less power. As of 2002, however, CRTs remain less expensive and still provide better color fidelity than alternative technologies.

NEVER, EVER PUT ANY MAGNET OF ANY SORT NEXT TO A CATHODE RAY TUBE. IT WILL WRECK THE DISPLAY IN A MANNER THAT IS HARD TO CORRECT.



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