A-1
Section 61246001L2-5, Issue 2
61246001L2-5B
HDSL MAINTENANCE MODES
This appendix describes operation of the HDSL
system with regard to detection of in-band and ESF
facility data link loopback codes. The operation of
the loopback commands in the ADTRAN HDSL
system is compliant with the recommendation to
ANSI recorded in T1E1.4/92. The HDSL network
loopback points described below are shown in
Figures A-1 and A-2.
HTU-C Loopback:
A regenerative loopback of the
DSX-1 signal toward the network.
HTU-R Loopback:
A regenerative loopback of the
DS1 signal toward the network. This loopback is in
Appendix A
HDSL Loopbacks
addition to a separate Smartjack loopback. Separate
activation sequences are provided for the HTU-R and
the Smartjack loopback initiation.
HRE Loopback:
A regenerative loopback of the
HDSL signal toward the network.
Upon deactivation of a loopback, the HDSL system
will synchronize automatically. Note that the
synchronization process of the HDSL system upon
deactivation of the HRE loopback could take up to 15
seconds, ensuring all system elements are
synchronized.
Figure A-2. HDSL Element State Diagram
LOOPUP / TIMEOUT
STATE
ARMED
STATE
LOOPUP / NO TIMEOUT
STATE
DISARMED
STATE
ACTIVATION
LOOPUP
TIMEOUT
ARMING
TIMEOUT
DEACTIVATION
DISARM
LOOPUP
TIMEOUT
DISABLE
Figure A-1. HDSL Loopback Points
HTU-C M
HTU-R
HRE
DSX-1
Interface
HDSL
Loops
HDSL
Loops
DS1
Interface
NIU
