HDSL2 System Testing HDSL2 for General Distribution Installation and Maintenance Practice
14 61223HDSL2L2-5B
Figure 7. Bantam Jack Arrangements
Loopbacks
The ADTRAN HDSL2 modules respond to three different loopback activation processes. These
processes may be utilized to provide a loopback that affects either an H2TU-C or an H2TU-R
module (locally or remotely).
1. Loopbacks may be activated using the craft interface. The Loopback Options screen that
provides for the H2TU-C and H2TU-R loopbacks is described in “Control Port Operation”
on page 17.
2. The modules respond to the industry standard for HDSL loopbacks. A detailed description
of these loopback sequences is given in “Appendix A, HDSL2 Loopbacks”.
3. HDSL2 modules respond to loopbacks depending on the module type as follows:
• H2TU-C modules respond to loopbacks initiated using the software functions described
in 1 and 2 above.
• H2TU-R modules respond to loopbacks initiated using front panel pushbuttons. See
Table 8.
ADTRAN HDSL2 modules contain smartloop technology which constantly monitors the DSX-1
for a framing pattern. ADTRAN HDSL2 modules will initiate the proper loopback regardless of
how the loopback control sequence is sent (framed or unframed).
The loopback condition imposed in both cases is a logic level loopback at the point within an
H2TU-C module where the DSX-1 signal passes into the HDSL2 modulators. Figure 8 depicts
all of the loopback locations possible with ADTRAN HDSL2 equipment.
DSX-1
BRG
Rx
H2TU-C
DATA
PUMP
DSX-1
T1
R1
DSX-1
T
R
HDSL2
EQ
Rx
DSX-1
BRG
Tx
EQ
Tx
POWER
Tx
Rx
DS1
MON
CPE
DS1
INTERFACE
H2TUR
T
R
T1
R1
H2TU-C Bantam Jack Arrangement
(except DDM+ H2TU-C)
H2TU-R Bantam Jack Arrangement
