Cisco Systems 7940G Manual De Usuario

 provides general troubleshooting information for the Cisco Unified IP Phone Expansion 

Module 7914.

No display on the Cisco Unified IP Phone 
Expansion Module 7914

Verify that all of the cable connections are correct.

Verify that you have power to the Cisco Unified IP Phone Expansion 
Module 7914.

Lighted buttons on the first Cisco 
Unified IP Phone Expansion Module 7914 are all 
red.

Verify that the Cisco Unified IP Phone Expansion Module 7914 is 
defined in Cisco Unified Communications Manager.

Lighted buttons on the second Cisco 
Unified IP Phone Expansion Module 7914 are all 
amber.

Verify that the Cisco Unified IP Phone Expansion Module 7914 is 
defined in Cisco Unified Communications Manager.

Loopback condition.

A loopback condition can occur when the following conditions are met:

The SW Port Configuration option in the Network Configuration menu on the 
phone is set to 10H

 

(10-BaseT / half duplex)

The phone receives power from an external power supply.

The phone is powered down (the power supply is disconnected).

In this case, the switch port on the 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.