Install DS1 CPE Loopback Jack (T1 Only)
Issue 4 May 2002
5-63555-233-123
Configurations Using a Smart Jack
The addition of the loopback jack and the presence of a Smart Jack divides the
DS1 span into 3 separate sections for fault isolation. These sections are shown in
Figure 5-11 on page 5-64 through Figure 5-13 on page 5-66 for the different span
configurations. They are:
Section 1: Between the 120A2 (or later) ICSU and the loopback jack.
Section 2: Between the loopback jack and the Smart Jack (network interface
point).
Section 3: From the Smart Jack to the CO. It is necessary to contact the DS1
provider to run this test.
A problem can exist in 1 or more of the 3 sections. The field technician is
responsible for finding and correcting problems in the first 2 sections. The DS1
service provider is responsible for finding and correcting problems in the third
section. Testing is divided into 3 steps.
■ Test customer premises wiring (section 1 in the following 3 figures) from the
ICSU to the loopback jack as described in “DS1 Span Test.”
■ Test the CO-to-network interface wiring (section 3 in Figure 5-11 on page
5-64) using the Smart Jack loopback (CO responsibility). Coordinate this
test with the DS1 provider.
■ Test the short length of customer premises wiring (section 2 in the following
3 figures) between the loopback jack and the Smart Jack. This can be done
using a loopback that “overlaps” section 2 of the cable. Any of the following
loopbacks can do this:
a. The local ICSUs line loopback, which is typically activated, tested,
and then deactivated by the DS1 service provider at the CO end.
b. The local DS1 interface’s payload loopback, activated and tested by
the DS1 service provider at the CO end.
c. The far-end ICSU’s line loopback. This test is activated at the
management terminal by entering test ds1-loop <location>
far-csu-loopback-test-begin. The test is terminated by entering
test ds1-loop <location> end-loopback/span-test. Bit error
counts are examined as described in “DS1 Span Test.” This test
method is the least preferable because it covers wiring that is not in
the local portion of the span. This test only isolates problems to
section 2 wiring if there are no problems in the wiring between the
far-end CO and the far-end ICSU. Coordinate this test with the DS1
service provider.
If any of the above tests (a, b, or c) fail, a problem is indicated in section 2
as long as the tests for section 1 and section 3 pass. Since section 2
includes the network interface point, it is necessary to work with the service
provider to isolate the fault to the loopback jack cable, the “dumb” block, or
the Smart Jack.
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