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HDSL DDM+ Transceiver Unit for Central Office Installation and Maintenance Practice
HDSL SYSTEM TESTING
The ADTRAN HDSL system provides extensive ability to monitor the status and performance
of the DSX-1 signals, DS1 signals, and HDSL loop signals. Detailed performance monitoring is
provided by the front panel RS-232 control port. These features are valuable in troubleshooting
and isolating any system level problems that may occur at installation or during operation of
the HDSL system.
HTU-C Loopbacks
The DDM+ HTU-C responds to three different loopback activation processes. First, a loopback
may be commanded manually using the control port interface.
Figure 13
on page 27 depicts
the Loopback Options Screen which provides for DDM+ HTU-C, HTU-R, and HRE loopbacks.
Secondly, the DDM+ HTU-C responds to the defacto industry standard for HDSL loopbacks. A
detailed description of these loopback sequences is given in
"Appendix A, HDSL
Loopbacks".
Third, the DDM+ HTU-C responds to loopbacks initiated using the FCD located on the
faceplate of the unit. For more information, refer to
"Front Panel Operation"
on page 12.
This unit contains smartloop technology. That is, if the unit is optioned to operate in an
unframed mode, it constantly monitors the DSX-1 for a framing pattern. If a framed loopback
control sequence is sent, then the unit will initiate the proper loopback command. For more
information refer to
"Appendix A, HDSL
Loopbacks".
The loopback condition imposed in both cases is a logic level loopback at the point within the
DDM+ HTU-C where the DSX-1 signal passes into the HDSL modulators.
Figure 24
depicts all
the loopback locations possible with ADTRAN HDSL equipment.
In addition to network-side loopbacks, the DDM+ HTU-C provides customer-side loopbacks
initiated by using the terminal control port, as described in
"Control Port Operation"
on
page 16. In this mode, an AIS signal is supplied to the network.
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Table of Contents
Troubleshooting
