Hdsl System Testing; Figure 5. Htu-C M R Bantam Jack Arrangement; Figure 6. Hdsl Loopbacks - ADTRAN HTU-C M R Installation And Maintenance Manual

4. HDSL SYSTEM TESTING

The ADTRAN HDSL system provides the 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 or the
ADTRAN HDSL Fuse/Alarm/Control Unit (HFAC)
Shelf Controller. These features are valuable in
troubleshooting and isolating any system level
problems that may occur at installation or during
operation of the HDSL system. The following
subsections describe additional testing features.
HTU-C M R EQ Bantam Jacks
The front panel of HTU-C M R contains metallic
splitting bantam jacks for access to DSX-1 Tx and
Rx from the local loop. This permits intrusive
testing of the DSX-1 traffic on the HDSL local loop.
Figure 5 shows access provided by the DSX EQ
bantam jacks.
HTU-C M R
T
DSX-1
R
EQ
RX
EQ
TX
T1
DSX-1
R1
Figure 5. HTU-C Bantam Jack Arrangement
HTU-C M R Loopbacks
The HTU-C M R responds to two different loopback
activation processes. First, loopback may be
activated using the craft interface. The Loopback
Options Screen which provides for the HTU-C M R,
HTU-R, and HRE loopbacks are described in
subsection 5 of this practice
Secondly, the HTU-C M R responds to the industry
defacto standard for HDSL loopbacks. A detailed
description of these loopback sequences is given in
Appendix A.
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
6
HDSL
HDSL
LOOP 1
LOOP 1
HTU-C
HDSL
DATA
SPAN POWER
PUMP
HDSL HDSL
LOOP 2
LOOP 2
Section 61245001L6-5, Issue 7
pattern. If a framed loopback control sequence is
sent, then the unit will initiate the proper loopback
command (see Appendix A of this practice).
The loopback condition imposed in both cases is a
logic level loopback at the point within the
HTU-C M R where the DSX-1 signal passes into the
HDSL modulators. Figure 6 depicts all of the
loopback locations possible with ADTRAN HDSL
equipment.
HTU-C Network-Side Loopback
LOCAL
DSX-1
LOOP
HTU-C
HTU-R Network-Side Loopback and/or
HTU-R NIU Loopback
LOCAL
DSX-1
LOOP
HTU-C
HTU-R Customer-Side Loopback
X
LOCAL
AIS
LOOP
HTU-C
HTU-C Customer-Side Loopback
X
LOCAL
AIS
LOOP
HTU-C
Bilateral Loopback
LOCAL
DSX-1
LOOP
HTU-C
HRE Network-Side Loopback
DSX-1
HTU-C
HRE Customer-Side Loopback
X
AIS
HTU-C
Dual HRE Network-Side Loopback
DSX-1
HTU-C HRE
X = Signal Inactive
D = Data Sent

Figure 6. HDSL Loopbacks

In addition to network-side loopbacks, the
HTU-C M R provides customer-side loopbacks
initiated by using either the terminal control port or
inband loop codes (see Appendix A). In this mode,
an AIS signal is supplied to the network.
AIS
DS1
X
HTU-R
AIS
DS1
X
HTU-R
DS1
HTU-R
DS1
HTU-R
DS1
HTU-R
AIS
DS1
X
HRE HTU-R
DS1
HTU-R
HRE
AIS
X
X
HRE HTU-R DS1
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