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[ The PC Guide | Systems and Components Reference Guide | Power | External Power | External Power Problems ]

Line Noise

Line noise consists of small variations in the voltage level delivered to the computer. A certain amount of line noise is normal (no power generation circuits are perfect) and for the most part, all but the absolutely cheesiest power supplies will deal with them without difficulty. However, in some areas the power quality is worse than others. Also, if the PC is sharing a circuit or is physically located near devices that cause electromagnetic interference (motors, heavy machinery, radio transmitters, etc.) then line noise can be a serious concern. Noise that the power supply cannot handle can cause it to malfunction and pass the problem on to your motherboard or other internal devices.

Representations of three cycles of an "ideal" AC signal,
and three cycles of a fairly noisy AC signal.

Some devices in your own home or office can actually generate noise and push it back onto the AC line to affect other devices through the power system. Better power protection devices will isolate devices that plug into them to prevent this cross-pollution.

Next: Surges


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