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Appendix C
Maintaining the Cisco Wide Area Application Engine
Using Power Protection Devices
Surge Protectors
Line Conditioners
Uninterruptible Power Supplies
OL-9137-02
A number of devices are available that protect against power problems such as
power surges, transients, and power failures. The following sections describe
some of these devices.
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 electrical outlet. 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.
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 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.
Cisco Wide Area Application Engine 512 and 612 Hardware Installation Guide
Using Power Protection Devices
C-7
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