Section 150-431-114
Release 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-431, List 1D 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-431, List 1D 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-431, List
1D. 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-431 List 2D
DSX-1 interface, verify that the HLU-431, List
1D is making a positive connection with its mounting
assembly (shelf) connector. Also, verify that the HLU-
431, List 1D 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.
15.04
The transmit and receive 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 Line jacks, splits the XMT and RCV and creates
metallic loopbacks toward both the DSX-1 and the HLU-
431, List 1D. If plugs are inserted into both Line jacks,
the BRG jacks can be used to send and receive test
patterns toward the DSX-1.
