46054
13
Troubleshooting
(cont’d)
* Water may cause most of these symptoms and may cause multiple symptoms to appear at
the same time.
Intermittent or
variable current
Wet cables or a bad
connection
If accompanied by noise, the cause is usually
wet cables.
If no noise is present, the cause is probably a
bad connection in a cross-connect or a bad
connection at the central office.
RFI (radio
frequency
interference)
Split pair
An unbalanced pair near a radio transmitter will
be prone to RFI. Adding radio filters can reduce
the interference on the line (the symptom), but
does not solve the imbalance (the problem). To
troubleshoot, break the circuit down into
sections and check each section for split pairs
or a resistive imbalance.
A strong amount of radio interference may
trigger the test set’s excessive DC voltage alarm
and prevent connection when you attempt to go
off-hook. If this happens, listen closely for the
sound of a radio broadcast to determine if this
is the cause of the alarm. If it is necessary to
make a call in this situation, you may safely
override the alarm by holding down the TALK
button for the duration of the override tone.
When the test set goes quiet, release the TALK
button and dial the number.
Note: This override procedure will not work if
the line is unpowered or if a hazardous DC
voltage is present.
Improperly removed bridge taps may also
introduce RFI. Bridge taps, which were once used
for party-line service (multiple users sharing a
cable pair), were often disconnected but left in
place, with a stub section of cable still connected.
This stub section can act as an antenna and
induce radio signals into the circuit.
Symptom*
Possible Cause /
Troubleshooting Step
Explanation
