Configurations using fiber multiplexers – Avaya 555-233-116 User Manual

Page 156

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DS1/T1 CPE loopback jack

555-233-116

156

Issue 4 October 2002

Configurations using fiber multiplexers

Use the loopback jack when customer premises DS1 wiring connects to an on-site
fiber multiplexer (MUX) and allows wiring to the network interface point on the
MUX to be remotely tested. For a G700 Media Gateway, this requires that the
MM710 CSU be set so it can be used on DS1 wiring to the MUX.

Fiber MUXs can take the place of Interface termination feeds as shown in

Figure 24

through

Figure 31

. Test these spans using the same procedures as

metallic spans. Note the following points:

1. Fiber MUXs may have loopback capabilities that can the service provider

can activate from the CO end. These may loop the signal back to the CO or
back to the DS1 board. 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.

2. Be aware that there are installations that use repeatered metallic lines

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
.

To check for the presence of DC, make the following 4 measurements at the
network interface jack:

1. From transmit tip (T, Pin 5) to receive tip (T1, Pin 2)

2. From transmit ring (R, Pin 4) to receive ring (R1, Pin 1)

3. From transmit tip (T, Pin 5) to transmit ring (R, Pin 4)

4. From receive tip (T1, Pin 2) to receive ring (R1, Pin 1)

All measurements should read 0 (zero) volts DC. For pin numbers and pin
designations, refer to Integrated Channel Service Unit (ICSU) Installation and
Operation
.

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