Section 150-319-124
Revision 03
Page 40
19.09
The HiGain system may take longer than
normal to respond to in-band loopback commands
when its framing mode is set to UNFR and the in-band
commands are sent in either an SF or ESF mode.
The frame bits override the command bits and cause
errors in the command sequence. These errors cause
the HiGain system to reject some sequences. This
can extend the detection interval.
19.10
Depressing both the Mode and SEL push
buttons on the front panel for at least three seconds
initiates a Manual Loopback session. This session
allows the user to select one of eight HiGain system
loopbacks. The message, “MAN LPBK,” appears on
the front panel display followed by the message
“NLO?” If the SEL push 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 push button, “NLO?” is
replaced by “ND1?” This now allows an NDU1
loopback to be executed (if it is a doubler application)
with the SEL push button. If this same routine is
followed, all eight loopbacks (NLOC, NDU1, NDU2,
NREM, CLOC, CDU2, CDU1, and CREM) are
presented and can be initiated in the sequence listed.
Pressing the Mode push button two more times yields
the CRE and CLO loopback options in the sequence
listed. This interactive push-button procedure permits
any of the four HiGain loopbacks to be
executed/activated. 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 and no loopback is in effect,
the manual loopback session terminates and the
normal margin displays reappear. If any loopback is
in effect, the 30-second time-out is inhibited. The
active loopback and the manual loopback session
continue until the loopback times out in accordance
with the user-selected LBTO setting. Only one
loopback can exist at any given time. Pressing both
Mode and SEL 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 (see
Figure 23), from which any of the eight loopbacks can
be initiated/terminated.
20. TESTING
20.01
Table 12 through Table 17 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.
20.02
The HLU-319, List 2D 4-character front panel
display has many useful system diagnostic messages,
which are listed in Table 18. The display turns on
when power is initially applied to the HLU-319, List
2D. In order to conserve power, it 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.
20.03
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 the mounting
assembly's connector. Also, verify that the equalizer
is set to EXT for driving external equalizers or per the
equalization settings of Table 1 for internal
equalization. All installations should be set to the
largest value that does not exceed the distance from
the DSX-1 to the shelf.
20.04
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.
