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Cisco 860 Series, Cisco 880 Series, and Cisco 890 Series Integrated Services Routers Hardware Installation Guide
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Chapter 3 Connecting the Router
Connecting a Voice ISDN BRI Line
Note If you have specified the use of a private line automatic ringdown (PLAR) off-premises extension (OPX)
connection mode for an FXO voice port (with loop resistance less than 8000 Ohm), you must ensure that
the soft-offhook option is enabled on the port.
This option allows a stepped offhook resistance during seizure, which avoids overloading the circuit
during offhook in the event that ringing voltage is present on the circuit at the same time as the trunk
seizure. The stepped offhook resistance is initially set to 800 Ohms, then adjusts to 50 Ohms when
ringing voltage is not present.
To enable the soft-offhook command on the port, and to access the connection command with plar opx
syntax, see the Cisco Command Lookup Tool.
Connecting a Voice ISDN BRI Line
Use a straight-through RJ-45 cable to connect the voice BRI port to the ISDN network through a
telephone outlet or other device.
Caution To prevent damage to the router, be sure to connect the BRI cable to the BRI connector only and not to
any other RJ-45 connector.
To connect the voice BRI line, follow these steps:
Step 1 Connect one end of a straight-through RJ-45–to–RJ-45 cable to the Voice BRI port.
Note When the interface is configured as NT and is connecting to a TE device, use a crossover cable.
See Table A-16.