Cisco 4490 - Manual (Page 76)

Chapter 5 Maintaining the Cisco Global Site Selector 4490
Using Power Protection Devices
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Cisco Global Site Selector 4490 Hardware Installation Guide
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Line Conditioners
Line conditioners go beyond the overvoltage protection of surge protectors. Line
conditioners keep a system’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 protectors—up to several hundred dollars.
However, these devices cannot protect against a complete loss of power.
Uninterruptible Power Supplies
Uninterruptible power supply (UPS) systems offer the most complete protection
against variations in power because they use battery power to keep the system
running when AC power is lost. The battery is charged by the AC power while it
is available, so once 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.
Surge protectors should be used with all UPS systems, and the UPS system should
be Underwriters Laboratories (UL) safety-approved.