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Testing LTPH-UM-1031-03, Issue 3
54 September 12, 2003 H4TU-C-319 List 1
To perform the A5LB test procedures:
1 Send the inband Arming and NI LPBK code 11000 to the H4TU-C for at least 5 seconds.
2 Monitor the output of the H4TU-C for the return of the pattern. Return of the pattern indicates one of the
following:
• The H4TU-R has looped up (if the SMJK Loopback option is enabled).
• An external NID has looped up (if the SMJK Loopback option is disabled), and the H4TU-C and
H4TU-R have been armed.
3 Verify, if possible, that the H4TU-R Loopback LED is either flashing yellow at four times per second
(indicating that the system is armed), or is a steady yellow (indicating that it is both armed and in SMJK
loopback). The H4TU-C Status LED also flashes yellow when the system is armed.
4 Once armed, the H4TU-C 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:
• 2 seconds of AIS (all ones pattern)
• 2 seconds of returning data pattern
• 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
— 20 errors, if ILR-2 (H4TU-R) was sent
• 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 H4TU-C 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
“Setting the Loopback Time-Out Option (LBTO)” on page 48). 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 H4TU-C down is
to do one of the following:
• Issue the IR (Intelligent Repeater) LPDN (loopdown) code 1001-0011-1001-0011 (9393).
• Issue the NI LPDN and Disarm inband code 11100 or the ESF-DL code (FF24).
If the Arming code is not returned after 5 seconds, the system may be armed, but there is no
active loopback.
Some Intelligent Repeater (IR) test sets do not count frame errors as bit errors when the test
pattern is framed and the H4TU-C-319 is set to the Auto framing mode. To improve compatibility
with those test sets, the H4TU-C generates 231 (NLOC and CREM) ID bit errors. As a result, the
H4TU-C 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, ADC
recommends sending unframed IR commands.