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[ The PC Guide | System Care Guide | System Care: Protecting Your PC | General System Care Factors | Environmental Care Factors ]

Electromagnetic Interference (EMI)

All electronic devices give off electromagnetic emissions. This is radiation that is a byproduct of electrical or magnetic activity. Unfortunately, the emissions from one device can interfere with other devices, causing potential problems. Interference can lead to data loss, picture quality degradation on monitors, and other problems with your PC, or problems with other devices such as television sets and radios. These are generally categorized as electromagnetic interference or EMI problems.

There are actually two different issues here: EMI emissions by the PC, and EMI emissions received by the PC. PCs generally do not cause very much interference with other devices; they are required by the Federal Communications Commission (FCC) to be certified as Class B devices. This certification is used to show that the PC conforms to standards that limit the amount of EMI that a PC can produce. The only catch to this is that you have to keep the cover on the PC. This is one reason why the cover is always made from metal. (Keeping the cover on is also an important part of ensuring proper ventilation).

PCs can be affected by electromagnetic interference from other devices, in two major ways. One is direct effects through proximity with other devices; another is electrical interference over the power lines. Most PCs generally do not have many problems with EMI, but those that do can cause incredible frustrating to their owners. There are several things that you can do to avoid or at least reduce EMI if you think it is affecting your PCs:

  • Physical Isolation: Devices that emit electromagnetic radiation should be kept a reasonable distance from your PC, peripherals and media. This includes television sets, radios, lights, kitchen appliances, and stereo speakers (the ones designed for use with PCs are generally shielded and are much less of an issue).
  • Use Dedicated Circuits: Many office buildings especially, have separate power circuits that are intended for use by PCs. Keeping your PC on a circuit that is separate from the circuit running your refrigerator and air conditioning unit means that there will be much less interference passing to the computer from the other devices (and this will also improve the quality of the power being sent to your machine in general).
  • Power Conditioning: The use of a line conditioner or uninterruptible power supply can filter out interference caused by other devices that share a line with your PC.

Next: Cooling and Ventilation Care Factors

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