Checking For The Presence Of Dc - Avaya G450 Installing And Upgrading

Note:
Fiber MUXs may have loopback capabilities that the service provider can activate
Note:
from the CO end. These may loop the signal back to the CO or back to the DS1
MM710. If the MUX provides the equivalent of a line loopback on the "problem"
DS1 facility, activate it after a successful loopback jack test, and use it to isolate
problems to the wiring between the loopback jack and the MUX.
!
Important:
Be aware that there are installations that use repeater-augmented metallic lines
Important:
between the MUX and the "dumb" block. These lines require DC power for the
repeaters and this DC power is present at the "dumb" block interface to the CPE
equipment. A loopback jack is required in this configuration to properly isolate
and terminate the DC power.

Checking for the presence of DC

1. Make the following four measurements at the network interface jack:
From transmit tip (T, Pin 5) to receive tip (T1, Pin 2)
●
From transmit ring (R, Pin 4) to receive ring (R1, Pin 1)
●
From transmit tip (T, Pin 5) to transmit ring (R, Pin 4)
●
From receive tip (T1, Pin 2) to receive ring (R1, Pin 1)
●
All measurements should read 0 (zero) volts DC.
DS1/T1 CPE loopback jack
Issue 2 June 2008 277