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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

H2TU-C

DATA

PUMP

DSX-1

HDSL2

DSX-1

BRG

POWER

DS1

MON

CPE

DS1

INTERFACE

H2TUR

H2TU-C Bantam Jack Arrangement

(except DDM+ H2TU-C)

H2TU-R Bantam Jack Arrangement

1 2 ... 19 20 21 22 23 24 25 26 27 28 29 ... 89 90

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