DEFINITY Enterprise Communications Server Release 7
Maintenance for R7r
555-230-126 Issue 4
June 1999
Additional Maintenance Procedures
6-22DS1 CPE Loopback Jack (T1 Only)
6
Configurations Using Fiber Multiplexers
Use the loopback jac k when customer premises DS1 wiring c onnects to an
on-site fiber multiplexer (MUX) and allo ws wiring to the network interface p oint on
the MUX to be remotely tested. This requires that ICSUs be used on DS1 wiring
to the MUX.
Fiber MUXes can take the place of Interfac e termination feeds as shown in
Figure 6-1 , Figure 6-2, Figure 6-3, and Figure 6-4. Test these spans using the
same procedures as metallic spans. Note the following p oints:
1. Fiber MUX es may have lo opback capabilities that can be act ivated by the
service provider from the CO end . These may loop the signal bac k to the
CO or back to the DS1 board. If the MU X provides the equivalent of a line
loopback on the “ problem” DS1 facility, this may be ac tivated following a
successful loopb ack jack test and used to isolate problems to the wiring
between the loopbac k 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 p ower for
the repeaters and this DC power is p resent at the “dumb” block interfac e
to the CPE equipment.

A loopback jac k is required in this config uration 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 4)
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 4)
All measurements should read 0 (zero) volts DC. For pin numb ers and pin
designations, refer to

Integrated Channel Service Unit (ICSU) Installation and

Operation

, 555-230-193.
Operating Charasteristics
If a TN464F or TN767E and a 120A2 were installed in a system running pre-G3V3
software and the software is later upg raded to G3V3 Release 3 or later, reseat the
DS1 circuit pack so that the ICSU ad ministration fields will appear o n the DS1
administration form.