Issue 1, Section 150-231-164
Revision 04
Page 13
LBTO setting. Only one loopback can exist at any given
time. Pressing both push-buttons, again for three
seconds, terminates any active loopback, ends the
MANUAL loopback session and returns the display to
normal mode. Note that these same loopbacks can be
initiated from the RS-232 maintenance port by choosing
the LOOPBACK MODE, option D, from the MAIN
MENU. This displays the Loopback Menu (Figure 10),
from which any of the loopbacks can be
initiated/terminated.
4. TESTING
4.01
Table 2 through Table 7 provide step-by-step
test procedures for the HLU-231 List 6D as a
function of the loopback option selected. These
procedures allow verification of the integrity of the HDSL
channels at every module location as well as the DS1
channels to the customer and the local DSX-1 interface.
4.02
The HLU-231 List 6D 4-character front panel
display has many useful system diagnostic
messages. They are listed in Table 8. This display
turns on when power is initially applied to the HLU-231
List 6D. To conserve power, the display only remains on
for five minutes if neither the MODE or SEL buttons are
pressed. The use of either button activates the 4-
character display and restarts the 5-minute power-
control timer.
4.03
If trouble is encountered on the HLU-231 List
6D DSX-1 interface, verify that the HLU-231 List
6D is making a positive connection with its mounting
assembly (shelf) connector. Also, verify that the HLU-
231 List 6D internal equalizer is set to TEXT for driving
the external equalizer or to the correct distance range
per Table 1 for external equalization. All installations
should be set to the largest distance range value that
does not exceed the distance from the DSX-1 to the
shelf.
4.04
The transmit and receive T1 DSX-1 ports have
splitting access and bridging miniature 210-
series jacks as shown in Figure 2. Connecting one
cable between the two bridging jacks and another
between the two SPAN jacks splits the XMT and RCV
and creates metallic loopbacks towards both the DSX-1
and the HLU-231 List 6D. If plugs are inserted into both
SPAN jacks, the BRG jacks can be used to send and
receive test patterns towards the DSX-1.
Figure 5. HLU-231 non-Doubler Loopback Configurations. The most important of the HiGain family of loopback options is the
Smart-Jack loopback, which emulates the functions of a standard NID.
