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Function / Code
Response
Arm/ 11000 (also known as a 2-in-5 pattern)
The HTU-R will loop up toward the network. No AIS or errors will be sent as a result of this loopback. The H2TU-C and H2R will arm.
When sent from the customer, this code will arm all units.
Arm/ FF48 (1111 1111 0100 1000)
ESF facility datalink: ESF only; when sent from the network, all units will be armed and an H2TU-R network loopback will be activated.
This code has no functionality when sent from the customer.
Disarm/ 11100 (also known as a 3-in-5 pattern)
All units are removed from the armed state. If any of the units are in loopback when the 11100 pattern is received, they will loop down. The
LBK LEDs will turn off on all units.
Disarm/ FF24 (1111 1111 0010 0100)
ESF facility datalink; disarms and/or loops down all units.
H2TU-C Network Loop Up / D3D3 (1101 0011 1101 0011)
If the units have been armed and no units are in loopback*, the HTU-C will loop up toward the network, 2 seconds of AIS (all 1s) will be sent,
5 seconds of data will pass, and then 231 bit errors will be injected into the DSX-1 signal. As long as the pattern continues to be sent, 231
errors will be injected every 20 seconds. When the pattern is removed, the unit will remain in loopback. If the pattern is reinstated, the
injection of 231 bit errors will resume at 20-second intervals.
H2R Network Loop Up / C741 (1100 0111 0100 0001)
If an H2R is present, the units have been armed, the H2R will loop up toward the network, 2 seconds of AIS (all 1s) will be sent, 5 seconds of
data will pass, and then 10 bit errors will be injected into the DSX-1 signal. As long as the pattern continues to be sent, 10 errors will be
injected every 20 seconds. When the pattern is removed, the unit will remain in loopback. If the pattern is reinstated, the injection of 10 bit
errors will resume at 20-second intervals.
H2TU-R Address 20 for extended demarc / C754 (1100 0111 0101 0100)
When sent from the network, an H2TU-R network loopback is activated and a 200-bit error confirmation is sent. 2 seconds of AIS (all 1s) will be
sent, 5 seconds of data will pass, and then 200 bit errors will be injected into the DSX-1 signal. As long as the pattern continues to be sent, 200
errors will be injected every 20 seconds. The HDSL2 office unit will not block transmission of far end NIU loopback from the customer premise
(H2TU-R).
Loop Down / 9393 (1001 0011 1001 0011)
All units currently in loopback will loop down, but remain in the armed state.
Query Loopback / D5D5 (1101 0101 1101 0101)
If the units are armed and the H2TU-C, H2R, or H2TU-R are in network loopback, errors are injected into the DSX-1 signal upon detection of
the query loopback pattern. As long as the pattern continues to be sent, errors are injected again every 20 seconds. The number of errors
injected each time depends on which unit is in loopback. 231 errors are injected if the H2TU-C is in network loopback, 20 at a time if the
H2TU-R is in network loopback, 10 at a time if H2R #1 is in network loopback, and 200 at a time if H2R #2 is in network loopback.
Query Loop Parameters/ DBDB (1101 1011 1101 1011)
If the units are armed and the H2TU-C is in network loopback, errors are injected into the DSX-1 signal upon detection of the query loop parameters
pattern. As long as a pattern continues to be sent, errors are injected again every 20 seconds. The number of errors injected each time depends on the
current status of signal quality and pulse attenuation parameters on each loop. 111 errors are injected if all HDSL2 receiver points (H2TU-C, H2R
NET, H2R CST, and H2TU-R indicate pulse attenuation is 30 or lower and signal quality (margin) is 6 or higher. 11 errors at a time are injected if
any of the 12 receiver points indicate pulse attenuation is greater than 30 and/or signal quality (margin) is less than 6.
Loopback Time Out Override / D5D6 (1101 0101 1101 0110)
If the units are armed and this pattern is sent, the loopback time out will be disabled. The time out option will be updated on the PROVISIONING
menu of the HTU (viewable through the RS-232 port) to NONE. As long as the units remain armed, the time out will remain disabled. When the
units are disarmed, the loopback time out will return to the value it had before the D5D6 code was sent.
Span Power Disable / 6767 (0110 0111 0110 0111)
If the units are armed and this pattern is sent, the H2TU-C will deactivate its span power supply, turning off the H2TU-R and H2R (if present).
As long as the pattern continues to be sent, the span power supply will remain disabled. When the pattern is no longer being sent, the H2TU-
C will reactivate its span power supply, turning the remote unit(s) on. All units will retrain and return to the disarmed and unlooped state.
Note: All codes listed above must be sent for a minimum of 5 seconds in order for them to be detected and acted upon.
* If NIU is enabled, then the H2TU-R can be in network loopback when the H2TU-C or H2R loop up codes are sent.
1
Units must be armed with 11000b or FF48h before this code will work.
2
In order to behave like an NIU, the H2TU-R will not loop down from the network side with 9393h.
3
This code will be detected only if the units are armed AND there are NO loopbacks active.
A-2
Table A-1. In-Band Addressable Loopback Codes
1
1
2
1
1
1,3
1,3
61221045L2-5A
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