• Power supplies—In a redundant conguraon, the router contains either two AC or DC power
supplies that install into the front of the chassis. The slots are labeled PS 0 and PS 1 (le to right).
Each power supply provides power to all components in the router. When two power supplies are
present, they share power almost equally within a fully populated system. If one power supply in a
redundant conguraon fails or is removed, the remaining power supplies assume the enre
electrical load without interrupon. Two power supplies provide the maximum conguraon with full
power for as long as the router is operaonal.
•Roung Engine—If two Roung Engines are installed, one funcons as the primary and the other
funcons as the backup. If the primary Roung Engine fails, the backup can take over as the primary.
• Cooling system—The cooling system has redundant components, which are controlled by the host
subsystem. If one of the fans fails, the host subsystem increases the speed of the remaining fans to
provide sucient cooling for the router indenitely.
MX104 Alarm Contact Port Overview
The MX104 router has four external alarm contacts (also known as potenal free contacts) for
connecng the router to external alarm devices. The port labeled ALARM uses a 15-pin D-type
connector. The external alarm contact has 15 pins that accept a single core wire from external alarm
devices. A DE-15 alarm cable is required to connect the MX104 router to external alarm devices. Use
the gauge wire appropriate for the external device that you are connecng.
Whenever a system condion triggers an alarm, the alarm relay contacts are acvated, which in turn
acvates the external alarm devices. The alarm seng is open or closed.
You can connect and congure two output alarms and four input alarms. Two addional output alarms
are reserved and are used to indicate major and minor system alarms. Each output and input alarm has
two contacts for connecng the router to external alarm devices. Contact 1 of each alarm can be
congured as Normally Open [NO] or Normally Closed [NC] through the CLI. Contact 2 of each alarm
funcons as a reference [REF] or negave potenal terminal for Contact 1 of the corresponding alarm
and provides a current path for external alarm devices. Table 2 on page 9 describes the funcons of
the alarm contacts.
Table 2: Alarm Relay Contact Funcons
Contact Name Contact Name Funcon
Contact 1 Normally Open [NO] Current is not owing through Contact 1 and Contact 2 [REF] when
operang normally. When the current ows, the closed alarm is
generated.
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