Hardware Reference
In-Depth Information
• A spike of up to 2,500V
To verify the levels of protection built into the existing power supply in a computer
system, an independent laboratory subjected several unprotected PC systems to various
spikes and surges of up to 6,000V—considered the maximum level of surge that can be
transmitted to a system through an electrical outlet. Any higher voltage would cause the
power to arc to the ground within the outlet. None of the systems sustained permanent
damage in these tests. The worst thing that happened was that some of the systems re-
booted or shut down when the surge was more than 2,000V. Each system restarted when
the power switch was toggled after a shutdown.
Theautomatic shutdownofacomputerduringpowerdisturbancesisabuilt-infunctionof
most high-quality power supplies. You can reset the power supply by flipping the power
switch from on to off and back on again. Some power supplies even have an auto-restart
function. This type of power supply acts the same as others in a massive surge or spike
situation: Itshutsdownthesystem.Thedifferenceisthatafternormalpowerresumes,the
power supply waits for a specified delay of 3-6 seconds and then resets itself and powers
the system back up. Because no manual switch resetting is required, this feature might be
desirable in systems functioning as network servers or in those found in other unattended
locations.
The first time I witnessed a large surge that caused an immediate shutdown of all my sys-
tems, I was extremely surprised. All the systems were silent, but the monitor and modem
lightswerestillon.Myfirstthoughtwasthateverythingwasblown,butasimpletoggleof
each system-unit power switch caused the power supplies to reset, and the units powered
up with no problem. Since that first time, this type of shutdown has happened to me sev-
eral times, always without further problems.
Thefollowing typesofpower-protection devices areexplained inthesections that follow:
Surge Suppressors (Protectors)
Thesimplestformofpowerprotectionisanyoneofthecommerciallyavailablesurgepro-
tectors—that is, devices inserted between the system and the power line. These devices,
which cost between $20 and $200, can absorb the high-voltage transients produced by
