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HDSL2 MAINTENANCE MODES
This appendix describes operation of the HDSL2
system with regard to detection of in-band and ESF
facility data link loopback codes. The operation of
the loopback commands in the ADTRAN HDSL2
system is compliant with the recommendation to
ANSI recorded in T1E1.4/92. The HDSL2 network
loopback points described below are shown in
Figures A-1 and A-2.
H2TU-C Loopback: A regenerative loopback of the
DSX-1 signal toward the network.
H2TU-C
DSX-1
Interface
DEACTIVATION
61222004L2-5A
Appendix A
HDSL2 Loopbacks
HDSL2
Loop
Figure A-1. HDSL2 Loopback Points
DISARMED
ARMED
ACTIVATION
LOOPUP / TIMEOUT
LOOPUP / NO TIMEOUT
Figure A-2. HDSL2 Element State Diagram
Section 61222004L2-5, Issue 1
H2TU-R Loopback: A regenerative loopback of the
DS1 signal toward the network. This loopback is in
addition to a separate Smartjack loopback. Separate
activation sequences are provided for the H2TU-R and
the Smartjack loopback initiation.
Upon deactivation of a loopback, the HDSL2 system
will synchronize automatically.
H2TU-R
STATE
ARMING
TIMEOUT
STATE
LOOPUP
TIMEOUT
STATE
LOOPUP
TIMEOUT
DISABLE
STATE
NIU
DS1
Interface
DISARM
A-1
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