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Install DS1/T1 CPE loopback jack
Issue 10 June 2005 337
● The far-end ICSU’s line loopback. Activate this test at the management terminal by
entering test ds1-loop location far-csu-loopback-test-begin, where
location is the DS1 interface circuit pack corresponding to the loopback jack.
Terminate this test by entering test ds1-loop location end-loopback/
span-test, where location is the DS1 interface circuit pack corresponding to the
loopback jack.
Bit error counts are examined as described in the “DS1 Span Test” section. 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.
Failure of any of the above tests (a, b, or c) indicate a problem in Section 2. This could
mean bad loopback jack -to-”dumb” block cabling, but is more likely to indicate a problem
somewhere between the “dumb” block and the CO. This is the responsibility of the DS1
service provider.
If the DS1 Span Test confirms that there are no problems in Section 1, the technician
should proceed as follows to avoid unnecessary dispatch.
1. Identify and contact the DS1 service provider.
2. Inform the DS1 provider that loopback tests of the CPE wiring to the “dumb” block
(section 1) showed no problems.
3. If the far-end ICSU line loopback test failed, inform the DS1 provider.
4. Request that the DS1 provider perform a loopback test of their portion of the Section 2
wiring by sending someone out to loop Section 2 back to the CO at the “dumb” block.
If this test fails, the problem is in the service provider’s wiring.
If the test passes, the problem is in the cable between the loopback jack and the
“dumb” block. Replace the loopback jack.
Configurations using fiber multiplexers
Use the loopback jack when customer premises DS1 wiring connects to an on-site fiber
multiplexer (MUX) and allows wiring to the network interface point on the MUX to be remotely
tested.
Fiber MUXs can take the place of Interface termination feeds as shown in Figure 102
through
Figure 105
. Test these spans using the same procedures as metallic spans. Note the following
points:
1. Fiber MUXs may have loopback capabilities that can the service provider can activate from
the CO end. These may 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, activate it after
a successful loopback jack test, and use it to isolate problems to the wiring between the
loopback jack and the MUX.