Hardware Reference
In-Depth Information
nearby lightning strikes and power equipment. Some surge protectors can be effective for
certain types of power problems, but they offer only limited protection.
Surge protectors use several devices, usually metal-oxide varistors (MOVs), that can
clamp and shunt away all voltages above a certain level. MOVs are designed to accept
voltages as high as 6,000V and divert any power above 200V to ground. MOVs can
handle normal surges, but powerful surges such as direct lightning strikes can blow right
through them. MOVs are not designed to handle a high level of power and self-destruct
whileshuntingalargesurge.Thesedevicesthereforeceasetofunctionaftereitherasingle
large surge or a series of smaller ones. The real problem is that you can't easily tell when
theynolongerarefunctional.TheonlywaytotestthemistosubjecttheMOVstoasurge,
which destroys them. Therefore, you never really know whether your so-called surge pro-
tector is protecting your system.
Some surge protectors have status lights that let you know when a surge large enough to
blowtheMOVshasoccurred.Asurgesuppressorwithoutthisstatusindicatorlightisuse-
less because you never know when it has stopped protecting.
Underwriters Laboratories has produced an excellent standard that governs surge sup-
pressors,calledUL1449.Anysurgesuppressorthatmeetsthisstandardisagoodoneand
definitely offers a line of protection beyond what the power supply in your PC already
offers. The only types of surge suppressors worth buying, therefore, should have two fea-
tures:
• Conformance to the UL 1449 standard
• A status light indicating when the MOVs are blown
Units that meet the UL 1449 specification say so on the packaging or directly on the unit.
If this standard is not mentioned, it does not conform. Therefore, you should avoid it.
Another good feature to have in a surge suppressor is a built-in circuit breaker that can
be manually reset rather than a fuse. The breaker protects your system if it or a peripheral
develops a short.
Network and Phone Line Surge Protectors
A far bigger problem than powerline surges are surges through network and/or phone
cabling. I've personally experienced surges resulting from nearby lightning strikes dam-
age multiple computers and other equipment via ethernet and telephone lines, while vir-
tually nothing was damaged through the power lines. In systems with separate network
cards the damage was often limited to just the card, while in systems with the network
interface built-in to the motherboard, the motherboard itself was damaged. In many areas,
