Hardware Reference
In-Depth Information
the cable and phone lines are above ground, making them especially susceptible to light-
ning strikes.
Several companies manufacture or sell simple surge protectors that plug in between your
modemandthenetworkorphonelines.Theseinexpensivedevicescanbepurchasedfrom
most electronics supply houses. Some of the standard power line surge protectors include
connectors for network and/or phone line protection as well.
Line Conditioners
In addition to high-voltage and current conditions, other problems can occur with incom-
ing power. The voltage might dip below the level needed to run the system, resulting in a
brownout.Formsofelectricalnoiseotherthansimplevoltagesurgesorspikesmighttravel
through the power line, such as radio-frequency interference or electrical noise caused by
motors or other inductive loads.
Remembertwothingswhenyouwiretogetherdigitaldevices(suchascomputersandtheir
peripherals):
• Any wire can act as an antenna and have voltage induced in it by nearby electromag-
netic fields, which can come from other wires, telephones, CRTs, motors, fluorescent
fixtures, static discharge, and, of course, radio transmitters.
• Digital circuitry responds with surprising efficiency to noise of even a volt or two,
making those induced voltages particularly troublesome. The electrical wiring in your
building can act as an antenna, picking up all kinds of noise and disturbances.
Alineconditionercanhandlemanyofthesetypesofproblems.Itfiltersthepower,bridges
brownouts, suppresses high-voltage and current conditions, and generally acts as a buf-
fer between the power line and the system. A line conditioner does the job of a surge
suppressor, and much more. It is more of an active device, functioning continuously,
rather than a passive device that activates only when a surge is present. A line condition-
er provides true power conditioning and can handle myriad problems. It contains trans-
formers, capacitors, and other circuitry that can temporarily bridge a brownout or low-
voltage situation. These units usually cost $100-$300, depending on the power-handling
capacity of the unit.
Backup Power
Thenextlevelofpowerprotectionincludesbackuppower-protectiondevices.Theseunits
can provide power in case of a complete blackout, thereby providing the time necessary
for an orderly system shutdown. Two types are available: the SPS and the uninterruptible
power supply (UPS). The UPS is a special device because it does much more than just
provide backup power; it is also the best kind of line conditioner you can buy.
