Product Overview 1-21
Overview of the Cisco 12008
Rotary Power Switch
The rotary power switch on the DC-input power supply performs the same functions as
those described in the section entitled “Rotary Power Switch” on page 18 for the AC-input
power supply.
Circuit Breaker Alarm Terminal Block
The onboard power supply circuit breaker actuated by the rotary power switch on the DC-
input power supply incorporates an auxiliary switch that is mechanically linked to (but
electrically isolated from) the power supply circuit breaker.
When the power supply circuit breaker is tripped by an overcurrent condition in the power
supply, this auxiliary switch moves in unison, sending a signal to the circuit breaker alarm
terminal block on the power supply faceplate (see Figure1-7).
To remotely sense when the power supply circuit breaker has been tripped during an
overcurrent condition, you can attach an external alarm-monitoring facility to the alarm
terminal block. When the power supply circuit breaker is tripped, power is no longer
delivered to the backplane and the router ceases to operate. Hence, if you have attached an
external alarm monitoring facility to the alarm terminal block, site personnel can be
instantly alerted to this serious fault condition.
Typically, an external alarm-monitoring system incorporates a light pa nel (visible alarm) or
a klaxon (audible alarm) as the means for alerting site personnel to an alarm condition.
To reset the alarm contacts on the alarm terminal block, you must turn the rotary power
switch on the power supply OFF and then ON again, much as you would reset any circuit
breaker.
Note Any time you manually actuate the rotary power switch, such as when powering
down the router, the contacts on the alarm terminal block remain unaffected. Hence,
activation of the contacts on the alarm terminal block occurs only during a power supply
overcurrent condition. In other words, these contacts are used to provide an immediate,
overt indication of a power supply fault condition; they are not used to merely indicate that
a circuit breaker has been turned off manually.