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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.
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 DSX EQ Bantam Jacks
The front panel of HTU-C 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 4 shows access provided by the DSX EQ bantam
jacks.
HTU-C
T
DSX-1
R
EQ
RX
EQ
TX
T1
DSX-1
R1
Figure 4. HTU-C Bantam Jack Arrangement
HTU-C Loopbacks
The HTU-C 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, HTU-R, and HRE loopbacks will
be described in subsection 5.
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 of the loopback locations possible with
ADTRAN HDSL equipment.
61245.001L7-5A
Detailed
HDSL
HDSL
LOOP 1
LOOP 1
HTU-C
HDSL
DATA
SPAN POWER
PUMP
HDSL
HDSL
LOOP 2
LOOP 2
Section 61245001L7-5, Issue 1
When the unit is selected for framing, the addressable
loopback codes will only be detected when sent in the
appropriate framing mode. When the unit is selected for
unframed, the addressable loopback codes will be
detected regardless of the framing mode in which they
are sent.
In addition to network-side loopbacks, the HTU-C
provides customer-side loopbacks initiated by using the
terminal control port. In this mode, either an AIS signal
or customer data is supplied to the network. Customer
side loopbacks must be deactivated by using the terminal.
HTU-C Network-Side Loopback
DSX-1
LOCAL LOOP
HTU-C
HTU-R Network-Side Loopback and/or
HTU-R NIU Loopback
DSX-1
LOCAL LOOP
HTU-C
HTU-R Customer-Side Loopback
X
LOCAL LOOP
D
HTU-C
HTU-C Customer-Side Loopback
X
LOCAL LOOP
AIS
HTU-C
HRE Network-Side Loopback
DSX-1
HTU-C
X = Signal Inactive
D = Data Sent
Figure 5. HDSL Loopbacks
D
DS1
X
HTU-R
AIS
DS1
X
HTU-R
DS1
HTU-R
DS1
HTU-R
AIS
X
DS1
X
HTU-R
HRE
5
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