Section 150-388-124
Revision 01
Page 15
14.08
Pressing both the Mode and SEL front panel
push buttons, for at least three seconds, initiates a
Manual Loopback session. This session allows the user to
select one of four HiGain system loopbacks. The message,
“MAN LPBK,” appears on the front panel display followed
by the message “NLO?” If the SEL button is pressed at this
time, an NLOC loopback is executed changing the message
from “NLO?” to “NLOC.” If the Mode button is pressed
instead of the SEL button, “NLO?” is replaced by “NRE?”
This now allows an NREM loopback to be executed with
the SEL button. Pressing the Mode button two more times
yields the “CRE?” (CREM) and “CLO?” (CLOC) customer
loopback options in the sequence listed. This interactive
button procedure permits any of the four HiGain loopbacks
to be executed. The next loopback option can be presented
by pressing the Mode push button, however, the previously
executed loopback will remain active until the SEL push
button is pressed, and a different loopback is activated. If,
after 30 seconds, neither button is pressed, this manual
loopback session terminates, and the normal margin
displays reappear. If this time-out occurs with an active
loopback in effect, the appropriate loopback and loop
margin messages appear. Once the manual loopback
session terminates, the loopback remains in effect until it
times out in accordance with the user LBTO setting. It can
also be terminated by re-entering the manual loopback
mode and selecting another loopback. Only one loopback
can exist at any given time. Pressing both the Mode and
SEL buttons again for three seconds, terminates any active
loopback, ends the Manual Loopback session, and returns
the display to normal. 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 (see Figure 11), from which
any of the loopbacks can be initiated/ terminated.
15. TESTING
15.01
Table 2 through Table 7 provide step-by-step test
procedures for the HLU-388, List 2D 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.
15.02
The HLU-388, List 2D 4-character front panel
display has many useful system diagnostic
messages. They are listed in Table 10. This display turns
on when power is initially applied to the HLU-388, List 2D.
To conserve power, the display remains on for only five
minutes when 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.
15.03
If trouble is encountered on the HLU-388 List 2D
DSX-1 interface, verify that the HLU-388, List 2D
is making a positive connection with its mounting assembly
(shelf) connector. Also, verify that the HLU-388, List 2D
equalizer is set to the correct distance range per Table 1.
All installations should be set to the largest distance range
value that does not exceed the distance from the DSX-1 to
the shelf.
