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Degaussing monitors

Today the most common use of degaussing is in CRT-based computer monitors. For example, many monitors use a metal plate near the front of the tube to focus the electron beams from the back. This plate, the shadow mask, can pick up strong external fields and from that point produce discoloration on the display.

To combat this, CRTs add a copper coil wrapped around the front of the display, known as the degaussing coil. Tubes without an internal coil can be degaussed using an external hand held version. Internal degaussing coils in CRTs are generally much weaker than external degaussing coils, since a better degaussing coil takes up more space. A degauss causes a magnetic field inside the tube to oscillate rapidly, with decreasing amplitude. This leaves the shadow mask with a small and somewhat randomized field, removing the discoloration.



http://en.wikipedia.org/wiki/Degauss

http://www.forum.hr/archive/index.php/t-145988-p-2.html
http://www.elitesecurity.org/t26605-Monitori