HDSL4 for General Distribution Installation and Maintenance Practice
HDSL4 Maintenance Modes
61223HDSL4L2-5C
A-5
Third H4R
Loopback
1,2
C743
1100 0111 0100 0011
If three H4Rs are present, the third 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 30 logic
errors is injected. The burst of 30 logic errors con-
tinues every 20 seconds as long as the C743 pat-
tern is detected. When the pattern is removed, the
unit remains in loopback. If the pattern is rein-
stated, the injection of 30 logic errors continues
every 20 seconds.
H4TU-R Address 20
for Extended
Demarc
1,2
C742
1100 0111 0100 0010
If armed, the H4TU-R loops up toward the network,
2 seconds of AIS (all ones) is transmitted, the
looped data is sent for 5 seconds, and then a burst
of 20 logic errors is injected. The burst of 20 logic
errors continues every 10 seconds as long as the
C742 pattern is detected. When the pattern is
removed, the unit remains in loopback. If the pat-
tern is reinstated, the injection of 20 logic errors
continues every 10 seconds.
1. All codes listed above must be sent for a minimum of 5 seconds to be detected and acted upon.
2. Units must be armed with 11000b or FF48h before this code will work.
3. Loopback and error injection will only occur if the in-band code is received by the unit that is to go into loop-
back. In other words, if another loopback blocks the in-band code from being transmitted to the unit that is to
go into loopback, loopback and error injection will not occur.
Table A-2. Loopback Control Codes (Continued)
Function
Code (Hex / Binary)
Response
