Cisco 7937G - Unified IP Conference Station VoIP Phone Administration Manual page 100

General Troubleshooting Tips
Table 9-1
Summary
Loopback condition
Moving a network connection from
the conference station to a
workstation
No dial tone
No LCD screen display
One-way audio
Cisco Unified IP Conference Station 7937G Administration Guide for Cisco Unified Communications Manager 6.0
9-10
Cisco Unified IP Conference Station 7937G Troubleshooting (continued)
Explanation
A loopback condition can occur when the following conditions
are met:
•
•
In this case, the switch port on the conference station 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 station through the
network connection, you must be careful if you decide to
unplug the conference station's network connection and plug
the cable into a desktop computer.
Caution
Check that all connections are secure and in place. Make sure
all connections are correct.
Check to make sure that the conference station has power.
Make sure that the power supply unit is plugged in.
When at least one person in a call does not receive audio, IP
connectivity between conference stations is not established.
Check the configurations in routers and switches to ensure that
IP connectivity is properly configures.
Chapter 9
The conference station receives power from an external
power supply
The conference station is powered down (the power supply
is disconnected)
The computer's network card cannot receive power
through 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 station before plugging it into a
computer. This delay gives the switch enough time to
recognize that there is no longer a conference station
on the line and to stop providing power to the cable.
Troubleshooting and Maintenance
OL-11560-01 Rev. B0