 - ELF (extremely low frequency) refers to an electromagnetic fieldhaving a frequency much lower than the frequencies of signalstypically used in communications. The most common ELF field isradiated by utility power lines. In the United States, thisfrequency is 60 Hz. You are exposed to these fields whenever youare near electrical appliances of any kind.In recent years, ELF fields have become a subjectof concern in computing applications where cathode-ray tube (CRT) displaysare used. These displays, typically used in desktop computerworkstations and television sets, generate electromagnetic fields because ofthe strong, fluctuating currents in the electron-beam deflectingcoils. The frequencies of these fields are on the order of a fewkilohertz or less. Some studies suggest that ELF fields mighthave detrimental health effects on humans exposed to them forlong periods of time. The claims vary from increased risk ofcancer to premature births and miscarriages. However, as of thiswriting, conclusive proof has yet to be obtained that ELF fieldsare harmful at the levels encountered by computer users. The ELF fields surrounding a CRT display tend tobe stronger off the sides of the CRT than directly in front of itor behind it. The fields diminish rapidly in intensity withincreasing distance from the CRT. As a general rule, computerusers should sit at least 18 inches away from a CRT display.Side-by-side workstations should be at least five feet apart.These considerations are important for visual comfort and"breathing room" as much as for minimizing thepotential risk posed by ELF fields.
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Learn more about Network Administration |
| Networking FAQ: These FAQs for networking will help you learn networking basics. |
| Network user management: Use this guide to learn how to manage problem users on your network -- from un-savvy Internet novices to toxic bosses -- to keep your network secure. |
| Troubleshooting -- 'Network Know-How' Chapter 17: Troubleshooting, Chapter 17 of 'Network Know-How,' shows tools and methods that identify and solve network problems. Use this chapter as a tutorial to fixing computer connections. |
| Network management frameworks: FCAPS and ITIL: Network management is a complex topic. Thus far, two frameworks exist that can be of some use for understanding and taming network management: FCAPS and ITIL. |
| Networking podcasts: Listen to our networking podcasts and learn more about technologies you need to know to keep your network running smoothly. |
| The IT Guy: Networking comics: In our networking comic series, the IT guy and his office coworkers encounter day-to-day network challenges. |
| LAST UPDATED: |
20 Dec 2007
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