ADTRAN AHDSL2 - Manual (Page 13)

61221002L2-5B A-1
HDSL MAINTENANCE MODES
This appendix describes operation of the HDSL2
system with regard to detection of in-band and ESF
facility data link loopback codes.
Upon deactivation of a loopback, the HDSL2 system
will synchronize automatically.
Loopback Process Description
In general, the loopback process for the HDSL2
system elements is modeled on the corresponding
DS1 system process. Specifically, the H2TU-C
loopback is similar to an Intelligent Office Repeater
loopback and the H2TU-R loopbacks are similar to a
T1 NIU.
The unit can detect the loopback activation or
deactivation code sequence only if an error rate of
1E
-03 or greater is present.
Appendix A
HDSL2 Loopbacks
Loopback Control Codes
A summary of control sequences is given in Table
A-1.
NOTE
In all control code sequences presented, the
in-band codes are shown left-most bit transmitted
first, and the ESF data link codes with right-most
bit transmitted first.