Section 363-712-100
Revision 02
Page 11
TABLE 3. FLL-712 COT LINE UNIT TROUBLESHOOTING
Indication
Problem
Action
POWER LED off
1. The COT Shelf is no longer
receiving CO battery.
a) Verify that the fuse on the CO
fuse panel is good.
b) Verify wiring between the COT
Shield and the CO fuse panel,
and from the panel to the CO
battery.
2. The COT Line Unit fuse F1
has blown.
Replace the fuse.
LOOP 1 (2) SYNC LED
flashing or off
1. The HDSL line is attempting
to synchronize with the
central office unit or cannot
detect the HDSL signal from
the central office unit. This is
usually an indication that
there is a problem with the
HDSL circuit between the
COT and RT (assuming the
FAULT LED is off).
2. COLU and RTLU
incompatible. That is, one is
a T1 version and the other is
an E1 version.
a) Verify the HDSL circuits are
terminated properly and with the
correct orientation.
b) Measure the loop resistance of
each HDSL circuit (shorting the
pair at the far end). The loop
resistance must be less than that
shown in Table 1.
LOOP 1 (2) MARGIN LED
on
The HDSL line margin level is
below a preset level.
See the previous discussion on the
SYNC LED flashing or off.
FAULT LED on
Faulty FLL-712 COT Line Unit.
a) Check that none of the HDSL
pairs are shorted to ground.
b) Check for continuity from COT
to RT on all HDSL lines.
c) Replace the COT Line Unit, if
the RT line unit is confirmed
good. Otherwise, replace the
RT line unit.
