You can use the loopback jack when customer premises DS1 wiring connects to an onsite fiber multiplexer (MUX) and allows wiring to the network interface point on the MUX to be remotely tested. This requires that ICSUs be used on DS1 wiring to the MUX.
Fiber MUXs can take the place of interface termination feeds. These spans must be tested by using the same procedures as metallic spans.
Note:
Fiber MUXs might have loopback capabilities that can be activated by the service provider from the CO end. These might 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, this might be activated following a successful loopback jack test and used to isolate problems to the wiring between the loopback jack and the MUX.
Other:
Installations that use repeated metallic lines between the MUX and the “dumb” block require DC power for the repeaters. 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.
You can make the following four measurements at the network interface jack, to check for the presence of DC:
From Transmit Tip (T, Pin 5) to Receive Tip (T1, Pin 2)
From Transmit Ring (R, Pin 4) to Receive Ring (R1, Pin 4)
From Transmit Tip (T, Pin 5) to Transmit Ring (R, Pin 4)
From Receive Tip (T1, Pin 2) to Receive Ring (R1, Pin 4)
Every measurement should read 0 (zero) volts DC. For more information, see Avaya Aura® Communication Manager Overview and Specification.
