HDSL4 Maintenance Modes
HDSL4 for General Distribution Installation and Maintenance Practice
A-4
61223HDSL4L2-5C
Loopback Time Out
Override
1
D5D6 or
1101 0101 1101 0110
If the units are armed or a unit is currently in loop-
back when this pattern is sent from the network,
the loopback time out is disabled. As long as the
units remain armed, the time out remains dis-
abled. When the units are disarmed, the loopback
time out reverts to the previous loopback time out
setting.
If any element is in network loopback a bit error
confirmation will be sent.
H4TU-C
231 errors
H4R1
10 errors
H4R2
200 errors
H4R3
30 errors
H4TU-R
20 errors
Span Power Disable
1
6767 or
0110 0111 0110 0111
If the units are armed and 6767 is sent from the
network, the H4TU-C disables span power. If the
pattern is sent from the network, the span power is
disabled as long as 6767 pattern is detected. Once
the pattern is no longer received, the H4TU-C reac-
tivates span power. All units then retrain and
return to the disarmed and unlooped state.
First H4R
Loopback
1,2
C741
1100 0111 0100 0001
If one or more H4Rs are present, the H4R closest to
the H4TU-C loops up toward the network, 2 sec-
onds of AIS (all ones) are transmitted, the looped
data is sent for 5 seconds, and then a burst of 10
logic errors is injected. The burst of 10 logic errors
continues every 20 seconds as long as the C741
pattern is detected. When the pattern is removed,
the unit remains in loopback. If the pattern is rein-
stated, the injection of 10 logic errors continues
every 20 seconds.
Second H4R
Loopback
1,2
C754
1100 0111 0101 0100
If two H4Rs are present, the second H4R from the
H4TU-C loops up toward the network, 2 seconds of
AIS (all ones) are transmitted, the looped data is
sent for 5 seconds, and then a burst of 200 logic
errors is injected. The burst of 200 logic errors con-
tinues every 20 seconds as long as the C754 pat-
tern is detected. When the pattern is removed, the
unit remains in loopback. If the pattern is rein-
stated, the injection of 200 logic errors continues
every 20 seconds.
Table A-2. Loopback Control Codes (Continued)
Function
Code (Hex / Binary)
Response
