Issue 1, Section 150-231-134
Revision 01
Page 19
TABLE 6. TEST PROCEDURES FOR A2LB OPTION
Step
Action
1
Send into the HLU the inband ARMING and NIU (Network Interface Unit) LPBK code 11000
for at least 5 seconds, or at least 4 repetitions of the 16-bit ESF Data Link ARMING code 0001
0010 11111111.
2
Monitor the output of the HLU-231 for the return of the pattern. Return of pattern indicates that
either the HRU has looped-up (If the SMART-JACK LOOPBACK option is ENABLED) or that
an external NIU has looped up (If the SMART-JACK LOOPBACK option is DISABLED) and
that the HLU and HRU units have been ARMED. Verify that the HLU display intermittently
indicates ‘ARM and also “SMJK” if the HRU is in loopback. Also verify, if possible, that the
LOOPBACK LED of the HRU-412 is flashing, indicating that the HRU is armed or that it is on
solid, indicating that it is both armed and in loopback.
3
Once armed the HLU can be looped back (NLOC in Figure 4) by sending IOR (Intelligent
Office Repeater) LPBK activation code 1101 0011 1101 0011 for at least 5 seconds. The
tester observes the following activation response:
•
2 seconds of AIS (all ones), followed by:
•
5 seconds of returning data pattern, followed by:
•
231 logic errors (including the frame bits) occur in the returned pattern(10 errors if ILR-1
were sent), followed by:
•
normal looped data. (Note that this error pattern will repeat every 20 seconds as long as
the IOR loopback pattern is being sent. This same 20 second repeat scenario also applies
to ILR, Time-Out Override and Query commands.)
The HiGain Line Unit is now in Logic Loopback (NLOC of Figure 4). The display on the HLU-
231 periodically shows NLOC (network local loop) and ARM (the HLU is still armed) in
addition to the margin displays. The Loopback Time-out option, which is user settable to
NONE, 20, 60 or 120 minutes, determines the duration of this loopback unless it is overridden
by the TIME-OUT OVERRIDE command or a loop down command is sent. If the Time-out
Override code 1101 0101 1101 0110 is received, the “activation sequence” described above is
repeated and the automatic timed expiration of the loopback is inhibited. If this Time-out
Override is sent, then the only way to loop the HLU down is to issue the IR (Intelligent
Repeater) LPDN (loopdown) code 1001 0011 1001 0011 or to issue the NIU (Network
Interface Unit) LPDN and Disarm code 11100. The automatic time-out timer is restored during
subsequent loopback sessions.
4
Upon completion, the tester sends IOR LPDN code 1001 0011 1001 0011 to loop-down the
HiGain Line Unit. The unit remains ARMED however, as indicated by the ARM message on
the HLU-231 and the flashing of the HRU-412’s LOOPBACK LED.
Table continued on next page
