Power Protection Devices; Surge Protectors; Line Conditioners; Uninterruptible Power Supply - Dell Precision 410 User Manual

— Power tools
— Teletype machines
— Adding machines
— Laser printers
— Facsimile machines
— Any other motorized equipment
Besides these appliances, the greatest threat to a system's
supply of power are surges or blackouts caused by elec-
trical storms. Whenever possible, turn off the computer
and any peripherals and unplug them from their power
sources during thunderstorms.
If a blackout occurs—even a temporary one—while the
system is turned on, turn off the system immediately and
disconnect it from its power source. Leaving the system
on may cause problems when the power is restored; all
other appliances left on in the area can create large volt-
age spikes that can damage the system.
P
ower Protection Devices
A number of devices are available that protect against
power problems, such as power surges, transients, and
power failures. The following subsections describe some
of these devices.

Surge Protectors

Surge protectors are available in a variety of types and
usually provide a level of protection commensurate with
the cost of the device. Surge protectors prevent voltage
spikes, such as those caused during an electrical storm,
from entering a system through the AC power source.
Surge protectors, however, do not offer protection against
brownouts, which occur when the voltage drops more
than 20 percent below the normal AC line voltage level.
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Line Conditioners

Line conditioners go beyond the overvoltage protection
of surge protectors. Line conditioners keep a computer's
AC power source voltage at a fairly constant level and,
therefore, can handle brownouts. Because of this added
protection, line conditioners cost more than surge protec-
tors—up to several hundred dollars. However, these
devices cannot protect against a complete loss of power.

Uninterruptible Power Supply

An uninterruptible power supply (UPS) offers the most
complete protection against variations in power because
it uses battery power to keep the system running when
AC power is lost. AC power, while available, charges the
battery; when AC power is lost, the battery can provide
power to the system for a limited amount of time—from
15 minutes to an hour or so—depending on the UPS
system.
UPS systems range in price from a few hundred dollars to
several thousand dollars, with the more expensive units
allowing you to run larger systems for a longer period of
time when AC power is lost. UPS systems that provide
only 5 minutes of battery power let you conduct an
orderly shutdown of the system, but are not intended to
provide continued operation. Surge protectors should be
used with all UPS systems, and the UPS system should
be Underwriters Laboratories (UL) safety-approved.