Section 150-232-100
Revision 01
Page 55
TABLE 16. HLU-232 GNLB TEST PROCEDURES
Step
Action
1
Have the CO tester send the HRU-412 (3 in 7) in-band loop-up code for five seconds. Observe that the
HLU-232 List 1D displays the “NREM” message indicating an HRU-412 loopback is in effect (Figure 19).
2
Have the CO tester transmit a T1 test signal into the HLU-232 List 1D and verify that the returned
(looped) signal is error free.
3
If the above test fails, have the CO tester transmit the (3 in 5) in-band loop-down code. Verify that the
HLU-232 List 1D display returns to normal.
4
Have the CO tester send the HLU-232 List 1D (4 in 7) in-band loop-up code for five seconds. Observe
that the HLU-232 List 1D displays the “NLOC” message indicating an HLU-232 List 1D loopback is in
effect.
5
Repeat Step 2. If the test passes, the problem is in the cable pair or the HRU-412. If it fails, the
problem is in the CO equipment.
6
The NREM and NLOC loopbacks can also be initiated from the front panel of the HLU-232 List 1D with
the MODE and SEL buttons (Section C Paragraph 3.10).
7
The HLU-232 List 1D can be looped-up from the remote location (CREM) by issuing the (6 in 7) in-band
loop-up code at the HRU-412 DS1 input port.
8
The HRU-412 can be looped-up from the remote location (CLOC) by issuing the (5 in 7) in-band loop-up
code at the HRU-412 DS1 input port.
9
Doubler #1 can engage loopback from the remote location (CDU1) by issuing the (4 in 6) loopback in-
band loop-up code at the HRU-412 DS1 input port.
10
Doubler #1 can engage loopback from the local location (NDU1) by issuing the (2 in 6) loopback in-band
loop-up code at the HLU-232 List 1D DS1 input port.
11
Doubler #2 can engage loopback from the remote location (CDU2) by issuing the (5 in 6) loopback in-
band loop-up code at the HRU-412 DS1 input port.
12
Doubler #2 can engage loopback from the local location (NDU2) by issuing the (3 in 6) loopback in-band
loop-up code at the HLU-232 List 1D DS1 input port.
Note 1
When T1 loopback tests are performed on the HiGain system with metallic loopback connections at either end,
the DS1 code that occurs at the metallic loopback interface may be different from the DS1 code being received at
the opposite end when the DS1 user code is set to AUTO. For example, if the HRU-412 has a metallic loopback
and the HLU-232 List 1D receive pattern's code is changed from AMI to B8ZS and the all “0” pattern is sent into
the HLU-232 List 1D, the HRU-412 remains in its AMI mode and thus loops all “0”. This causes the HRU-412 to
indicate a LOS condition which then causes the HLU-232 List 1D to output the AIS pattern.
Note 2
The HiGain system may take longer than normal to respond to in-band commands when its framing mode is set
to UNFR and the in-band commands are sent in either an SF or ESF mode. The frame bits override the
command bits and cause errors in the command sequence. These errors cause the HiGain system to reject
some sequences. This can extend the detection interval.
