Dell Dimension L c Series, Справочное и ремонтное руководство

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Introduction 1-7
Surge protectors 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 keep a computer’s AC power source voltage at a fairly constant level
and, therefore, can handle brownouts. Because of this added protection, line condi-
tioners cost more than surge protectors—up to several hundred dollars. However,
these devices cannot protect against a complete loss of power.
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A power loss while your computer is writing to your hard-disk drive can result in loss
of data and file corruption. Worst case, your operating system could be corrupted.
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 provides power to the system for a limited amount of time—from
15 minutes to an hour or so—depending on the UPS system.
NOTE: Use a UPS to protect your computer only. Connect other devices, such as a
printer, to a separate power strip providing surge protection. The length of time that
the battery can supply power following an AC power loss decreases with additional
hardware.
UPS systems can cost a few hundred dollars to several thousand dollars, depending on
the operating time they provide when AC power is lost. UPS systems with 5 minutes
of battery power let you conduct an orderly shutdown of the system, but are not
intended to provide continued operation. A UPS system should be Underwriters Lab-
oratories (UL) safety-approved.