Cisco 8831 Administration Manual page 142

General troubleshooting information
Summary
Codec mismatch between the
conference phone and another
device
Dual-Tone Multi-Frequency
(DTMF) delay
conference phone does not ring
Loopback condition
Moving a network connection from
the conference phone to a
workstation
No dial tone
No LCD screen display
Cisco Unified IP Conference Phone 8831 Administration Guide for Cisco Unified Communications Manager
9.0
132
Explanation
The RxType and the TxType statistics show the codec that is being
used for a conversation between this conference phone and the other
device. The values of these statistics should match. If they do not, verify
that the other device can handle the codec conversation or that a
transcoder is in place to handle the service.
"Call Statistics
See the screen" section for information about displaying
these statistics.
When you are on a call that requires keypad input, if you press the keys
too quickly, some of them might not be recognized.
Check that the ringer setting is not "Ringer Off." Check the volume
level.
A loopback condition can occur when the following conditions are met:
• The conference phone receives power from an external power
supply
• The conference phone is powered down (the power supply is
disconnected)
In this case, the switch port on the conference phone can become
disabled and the following message will appear in the switch console
log:
HALF_DUX_COLLISION_EXCEED_THRESHOLD
To resolve this problem, re-enable the port from the switch.
If you are powering your conference phone through the network
connection, you must be careful if you decide to unplug the conference
phone network connection and plug the cable into a desktop computer.
The computer's network card cannot receive power through
Caution
the network connection; if power comes through the
connection, the network card can be destroyed. To protect
a network card, wait 10 seconds or longer after unplugging
the cable from the conference phone before plugging it into
a computer. This delay gives the switch enough time to
recognize that there is no longer a conference phone on the
line and to stop providing power to the cable.
Check that all connections are secure and in place. Make sure all
connections are correct.
Check to make sure that the conference phone has power. Make sure
that the power supply unit is plugged in.
Troubleshooting and maintenance