Section 150-431-114
Release 01
Page 39
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
Tables 12 through Table 17 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.
20.02
The HLU-431, List 1D 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-431, List
1D. 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-431 List 2D
DSX-1 interface, verify that the HLU-431, List
1D 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-
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.
