DS1 CPE Loopback Jack (T1 Only)
Issue 1 May 2002
5-7555-233-143
Configurations Using a Smart Jack
The addition of the loopback jack and the presence of a smart jack divides the
DS1 span into three separate sections for fault isolation. These sections are
shown in Figure 5-1 on page 5-8 through Figure 5-3 on page 5-10 for the different
span configurations. They are:
A problem can exist in one or more of the three sections. The field technician is
responsible for finding and correcting problems in the first two sections. The DS1
service provider is responsible for finding and correcting problems in the third
section. Testing is divided into three steps:
1. Test customer premises wiring (section 1 in the following three figures)
from the ICSU to the loopback jack as described in “DS1 Span Test.”
2. Test the CO-to-network interface wiring (section 3 in Figure 5-1 on page
5-8) using the smart jack loopback (CO responsibility). Coordinate this test
with the DS1 provider.
3. Test the short length of customer premises wiring (section 2 in the following
three 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 test a, b, or c fails, 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.
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 Central Office (CO). It is necessary to
contact the DS1 provider to run this test.
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