HDSL4 for General Distribution Installation and Maintenance Practice
HDSL4 Maintenance Modes
61223HDSL4L2-5C
A-3
Table A-2. Loopback Control Codes
Function
Code (Hex / Binary)
Response
ARM (in-band) - also
known as 2-in-5
pattern
11000 (binary)
If the pattern is sent from the network, the units
arm, and the H4TU-R loops up if Smartjack Loop-
back is enabled.
ARM (ESF Data
Link)
FF48 or
1111 1111 0100 1000
sent in the Facility Data
Link
If the pattern is sent from the network, the units
arm, and the H4TU-R loops up if Smartjack Loop-
back is enabled. When sent from the customer, the
units arm.
Disarm (in-band) -
also known as 3-in-
5 pattern
11100 (binary)
When sent from the network or customer, all units
are removed from the armed state, and loopbacks
are released.
Disarm (ESF Data
Link)
FF24 or
1111 1111 0010 0100
sent in the Facility Data
Link
When sent from the network or customer, all units
are removed from the armed state, and loopbacks
are released.
H4TU-C
Loopback
1,2
D3D3 or
1101 0011 1101 0011
If armed, the H4TU-C will loop up, 2 seconds of AIS
(all ones) are transmitted, the looped data is sent
for 5 seconds, and then a burst of 231 logic errors
is injected. The burst of 231 logic errors continues
every 20 seconds as long as the D3D3 pattern is
detected. When the pattern is removed, the unit
remains in loopback. If the pattern is reinstated,
the injection of 231 logic errors continues every 20
seconds.
Loop Down without
Disarm
9393 or
1001 0011 1001 0011
When sent from the network, all units currently in
loopback loop down. Armed units do not disarm.
To function like a smartjack, the H4TU-R does not
loop down from a network loopback in response to
the 9393 pattern if Smartjack Loopback is enabled.
Loopback Query
1
D5D5 or
1101 0101 1101 0101)
When the pattern is sent from the network, logic
errors are injected toward the network to indicate a
loopback is present toward the network. The num-
ber of errors injected is determined by the nearest
unit that is in loopback. As long as the pattern
continues to be sent, errors are injected again
every 20 seconds. The number of errors per trans-
ceiver is as follows:
H4TU-C
231 errors
H4R1
10 errors
H4R2
200 errors
H4R3
30 errors
H4TU-R
20 errors
