150-231-185-05, Revision 05
Troubleshooting
HLU-231 List 8E
September 13, 1999
49
To perform the A1LB, A2LB, and the A5LB test procedures:
1
Send the inband Arming and NI LPBK code 11000 to the HLU-231 for at least 5 seconds.
2
Monitor the output of the HLU-231 for the return of the pattern. Return of the pattern indicates one of the
following:
•
the HRU has looped up (if the SMJK Loopback option is Enabled).
•
an external NI has looped up (if the SMJK Loopback option is Disabled), and the HLU and HRU have
been armed.
3
Verify, if possible, that the HRU Loopback LED is either flashing yellow at 4-second intervals (indicating
that the system is armed), or is a steady green (indicating that it is both armed and in SMJK loopback). The
HLU Status LED also flashes yellow when the system is armed.
4
Once armed, the HLU-231 can be looped back by sending Intelligent Office Repeater (IOR) LPBK activation
code 1101-0011-1101-0011 (D3D3) for at least 5 seconds. You should observe the following activation
response pattern in the order presented:
a
2 seconds of AIS (identified by an all ones pattern)
b
2 seconds of returning data pattern
c
231 logic errors (including the frame bit) occurring in the returned pattern comprising:
–
10 errors, if ILR-1 (Doubler 1) was sent
–
200 errors, if ILR-20 (Doubler 2) was sent
–
30 errors, if ILR-3 (Doubler 3) was sent
–
40 errors, if ILR-4 (Doubler 4) was sent
–
20 errors, if ILR-2 (HRU) was sent
d
normal looped data.
This error pattern repeats every 20 seconds as long as the IOR loopback pattern is being sent. This also applies
to ILR, Time-out Override, and Query commands.
The HLU is now in logic loopback if the IOR NLOC loopback command was sent. The Time-out Override
command or a Loopdown command can override the selection made for the loopback time-out (see
the Loopback Time-out Option” on page 45
). If the Time-out Override code 1101-0101-1101-0110 (D5D6)
is received after activating a loopback, then the automatic timed expiration of the loopback is inhibited. If this
Time-out Override is sent, then the only way to loop the HLU-231 down is to do one of the following:
•
issue the IR LPDN (loopdown) code 1001-0011-1001-0011 (9393)
•
issue the NI LPDN and Disarm inband code 11100 or the ESF-DL code (FF24).
Some Intelligent Repeater (IR) test sets do not count frame errors as bit errors when the test
pattern is framed and the HLU-231 is set to the Auto framing mode. To improve compatibility
with those test sets, the HLU-231 generates 201 (NDU2 and CDU2) and 232 (NLOC and CREM)
ID bit errors. As a result, the HLU-231 may indicate one more or one less bit error, depending
on the test set type and the number of frame bits contained in the block of errored bits. To avoid
this uncertainty, PairGain recommends sending unframed IR commands.
The Time-out Override function is only valid for the current active loopback. The automatic
time-out timer is restored during subsequent loopback sessions.
