Comdial DX-80, Инструкция по установке и обслуживанию, Страница: 319 / 352

DX-80 I
NSTALLATION AND
M
AINTENANCE
M
ANUAL
P7290 IMM
4-3
Symptom(s) Diagnostic Aid Cause(s) Action
Shorted station
cabling.
At the KSU, power the system down and remove
the power cord from the AC outlet. Remove the
KSU cover (four screws). Disconnect all station
wiring on the affected 408M, 408E, or DPM8 and
connect one known-good DET directly to one of the
interface ports. Replace the KSU cover and retest
with this phone. If this telephone works OK, follow
the above procedures to test each interface port. If
any port is found bad replace the module. If no port
is found bad, replace the wiring/cabling. Telephone/Terminal
apparatus dead CPU Heartbeat
LED flashing
and
408M/408E/DPM
8 module
Heartbeat
flashing but one
or more digital
telephones are
not functioning.
Bad telephone If the above test yields all working ports and no
cabling errors, test each connected telephone one
at a time until the bad telephone is discovered.
Replace the telephone.
Note:
Digital telephones use only one twisted cable pair for power, data control and voice
communications. There are no fuses for station interface protection. Instead, a current
sensing Polly-switch limits excessive current going to each terminal connection. If a
station cable pair is shorted or a telephone’s DC power supply is damaged, the Polly-
switch will temporarily open to protect the KSU Module circuitry.
Symptom(s) Diagnostic Aid Cause(s) Action
Cable distance is too
long for gauge of
wire/cable used.
If a digital telephone is not receiving clear
2B+D signaling from the KSU, test as follows:
1. With station cable cross-connect (jumper)
wire removed and telephone unplugged, place
a short circuit across the inside wiring cable
pair at the user end (jack) of the cable.
2. With a DVM, measure the short circuit
resistance one way. The short-circuited cable
pair ohm reading should not exceed ____
ohms.
Non-standard
telephone cable being
used.
Digital telephone erratic
operation:
- Erratic LED/LCD
operation
- Faint data noise in the
background during
conversations
Digital
Volt/Ohm Meter
Multiple digital
extensions being fed
from one common
cable or on the same
cable pair.
Each digital telephone should operate on one
dedicated, unshielded, twisted pair cable to
avoid data noise and interference between
adjacent cable pairs.