Hardware Reference
In-Depth Information
tion, you learn about the four primary types of power-protection devices available and
when you should use them.
Before considering any further levels of power protection, you should know that a quality
powersupplyalreadyaffordsyouasubstantialamountofprotection.High-endpowersup-
plies from the vendors I recommend are designed to provide protection from higher-than-
normal voltages and currents, and they provide a limited amount of power-line noise fil-
tering.Someoftheinexpensive aftermarket powersupplies probablydonothavethissort
of protection. If you have an inexpensive computer, further protecting your system might
be wise.
Caution
All the power-protection features in this chapter and the protection features in the power
supply inside your computer require that the computer's AC power cable be connected to a
ground.
Many older homes do not have three-prong (grounded) outlets to accommodate grounded
devices.
Do not use a three-pronged adapter (that bypasses the three-prong requirement and enables
you to connect to a two-prong socket) to plug a surge suppressor, computer, or UPS into a
two-pronged outlet. They often don't provide a good ground and can inhibit the capabilities
of your power-protection devices.
Youalsoshouldtestyourpowersocketstoensuretheyaregrounded.Sometimesoutlets,des-
pite having three-prong sockets, are not connected to a ground wire; an inexpensive socket
tester (available at most hardware stores) can detect this condition.
Of course, the easiest form of protection is to turn off and unplug your computer equip-
ment (including your modem) when a thunderstorm is imminent. However, when this is
not possible, other alternatives are available.
Power supplies should stay within operating specifications and continue to run a system
even if any of these power line disturbances occur:
• Voltage drop to 80V for up to 2 seconds
• Voltage drop to 70V for up to .5 seconds
• Voltage surge of up to 143V for up to 1 second
Most high-quality power supplies (or the attached systems) will not be damaged by the
following occurrences:
• Full power outage
• Any voltage drop (brownout)
