Section 150-319-124
Revision 03
Page 16
14.09
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-319, 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-319, 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-319, 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-319 List
2D DSX-1 interface, verify that the HLU-319, List 2D
is making a positive connection with its mounting
assembly (shelf) connector. Also, verify that the HLU-
319, 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.
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-319, List 2D. If plugs are inserted into both
Line jacks, the BRG jacks can be used to send and
receive test patterns toward the DSX-1.
