Hdsl System Testing; Figure 5. Hdsl Loopbacks - ADTRAN DDM Plus HTU-C Installation And Maintenance Manual

4. 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 faceplate-mounted 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 HTU-C responds to two different loopback
activation processes. First, loopback may be
commanded manually using the control port
interface. Figure 11 depicts the Loopback Options
Screen which provides for HTU-C, HTU-R and
HRE loopbacks.
Secondly, the HTU-C responds to the industry
defacto standard for HDSL loopbacks. A detailed
description of these loopback sequences is given in
Appendix A.
The loopback condition imposed in both cases is a
logic level loopback at the point within the HTU-C
where the DSX-1 signal passes into the HDSL
modulators. Figure 5 depicts all the loopback
locations possible with ADTRAN HDSL
equipment.
In addition to network-side loopbacks, the HTU-C
provides customer-side loopbacks initiated by using
the terminal control port. In this mode, an AIS
signal is supplied to the network.
61245003L6-5E
DSX-1
DSX-1
DSX-1
Dual HRE Network-Side Loopback
DSX-1
HTU-C M
* = This signal will be AIS if using 1245026Lx HTU-R.
Section 61245003L6-5, Issue 5
HTU-C Network-Side Loopback
LOCAL
LOOP
HTU-C M HTU-R
HTU-R Network-Side Loopback and/or
HTU-R NIU Loopback
LOCAL
LOOP
HTU-C M HTU-R
HTU-R Customer-Side Loopback
X
LOCAL
LOOP
D
HTU-C M HTU-R
HTU-R Bilateral Loopback
LOCAL
LOOP
HTU-C M HTU-R
HTU-C Customer-Side Loopback
X
LOCAL
LOOP
AIS
HTU-C M HTU-R
HRE Network-Side Loopback
HTU-C M HRE
HRE HRE
X = Signal Inactive
D = Data Sent

Figure 5. HDSL Loopbacks

D *
DS1
X
AIS
DS1
X
DS1
DS1
DS1
AIS
X
X
DS1
HTU-R
AIS
X
X
DS1
HTU-R
7