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Catalyst 2955 Hardware Installation Guide
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Chapter 2 Overview
Front-Panel Description
The connector is a pluggable-screw terminal block connector that provides power
and return connections for both the primary and secondary power supplies. The
positive DC power connection for power supply A is labeled VA, and the return
for power supply A is the adjacent connection labeled RT. For power supply B (the
redundant power supply), the positive DC power connection is labeled VB, and
the return is the adjacent connection labeled RT.
The Catalyst 2955 switch can operate with a single power supply or with dual
power supplies. In dual-power mode, the switch draws power from the power
supply with higher voltage. If the primary power supply fails in dual-power mode,
the alternate power supply gives power to the switch.
Warning
When you connect or disconnect the power and relay connector with power
applied, an electrical arc can occur. This could cause an explosion in
hazardous area installations. Be sure that power is removed from the switch
and alarm circuit. Be sure that power cannot be accidentally turned on or verify
that the area is nonhazardous before proceeding.
Failure to securely tighten the power and relay connector captive screws can
result in an electrical arc if the connector is accidentally removed.
Statement
1058
The power and relay connector provides an interface for two independent,
normally open (NO) alarm relays. The relays can be triggered by alarms for
environmental, power supply, and port status conditions. The relays can be
configured to send a fault signal to an external alarm device, such as a bell or a
light indicator. You can use the CLI to associate any alarm condition with a single
alarm relay or with both relays.
To connect an external alarm device to the relay, you must connect two relay
contact wires to complete an electrical circuit. Because each external alarm device
requires two connections to a relay, the Catalyst 2955 switch supports a maximum
of two external alarm devices.
Note See the switch configuration guide for instructions on how to configure the alarm
relays.
For more information about the power and relay connector, see Appendix B,
“Connectors and Cables.”
