DEGAUSSING COILS

A coil of wire energized with an AC current, is used to neutralize magnetism in ferrous metal objects. The widest use for them was color CRT display for television and computer use. Stray magnetic fields near or certain parts of the CRT could cause color impurity problems in the display. A degaussing coil is inserted inside the monitor (around the front portion of the CRT) to automatically demagnetize the tube when the monitor is first turned on. This is the source of boning sound that many monitor made when switched on. Higher end monitors hava a manual degauss function that could be activated at anytime by pressing a button.

In cases where a strong magnet is brought near a CRT, the built-in coil might not be powerful enough, so a service tech would need to degauss it using a more powerful hand-held coil to correct the picture distortion. Modern LCD and LED displays are insensitive to magnetic fields, so degaussing coils have gone away.