Additional Maintenance Procedures
555-233-143
5-2 Issue 1 May 2002
DS1 CPE Loopback Jack (T1 Only)
Using the DS1 CPE loopback jack (apparatus code 700A, comcode 107988867),
a technician can test the DS1 span between the system and the network interface
point. The loopback jack is required when DC power appears at the interface to
the Integrated Channel Service Unit (ICSU). The loopback jack isolates the ICSU
from the DC power and properly loops the DC span power.
NOTE:
The loopback jack operates with any vintage of TN767E (or later) or TN464F
(or later) DS1 circuit packs and with G3V3 EDI Release 3 (or later) software.
The loopback jack operates with the 120A2 (or later) ICSU only; not the
31xx series of Channel Service Units (CSUs) or other external CSUs or
earlier ICSUs.
Loopback Jack Installation
Configurations Using a Smart Jack
The preferred location of the loopback jack is at the interface to the smart jack.
This provides maximum coverage of CPE wiring when remote tests are run using
the loopback jack. If the smart jack is not accessible, install the loopback jack at
the extended demarcation point.
1. If there is no extended demarcation point, install the loopback jack directly
at the network interface point as shown in Figure 5-1 on page 5-8.
2. If there is an extended demarcation point and the smart jack is not
accessible, install the loopback jack as shown in Figure 5-2 on page 5-9.
3. If there is an extended demarcation point, but the smart jack is accessible,
install the loopback jack as shown in Figure 5-3 on page 5-10.
Configurations without a Smart Jack
Install the loopback jack at the point where the cabling from the ICSU plugs into
the “dumb” block. If there is more than one “dumb” block, choose the one that is
closest to the interface termination feed or the fiber MUX. This provides
maximum coverage for loopback jack tests. See Figure 5-4 on page 5-11 and
Figure 5-5 on page 5-12.
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