Cisco CP-7975G Administration Guide - Page 213

Chapter 9 Troubleshooting and Maintenance General Troubleshooting Tips Table 9-2 Cisco Unified IP Phone Troubleshooting (continued) Summary Explanation Moving a network connection If you are powering your phone through the network connection, from the phone to a workstation you must be careful if you decide to unplug the phone's network connection and plug the cable into a desktop computer. Caution 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 phone before plugging it into a computer. This delay gives the switch enough time to recognize that there is no longer a phone on the line and to stop providing power to the cable. Changing the telephone configuration LCD display issues Dual-Tone Multi-Frequency (DTMF) delay Codec mismatch between the phone and another device Sound sample mismatch between the phone and another device Gaps in voice calls By default, the network configuration options are locked to prevent users from making changes that could impact their network connectivity. You must unlock the network configuration options before you can configure them. See Unlocking and Locking Options, page 4-3 for details. If the display appears to have rolling lines or a wavy pattern, it might be interacting with certain types of older fluorescent lights in the building. Moving the phone away from the lights, or replacing the lights, should resolve the problem. When you are on a call that requires keypad input, if you press the keys too quickly, some of them might not be recognized. The RxType and the TxType statistics show the codec that is being used for a conversation between this Cisco Unified IP 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. See Call Statistics Screen, page 7-15 for information about displaying these statistics. The RxSize and the TxSize statistics show the size of the voice packets that are being used in a conversation between this Cisco Unified IP phone and the other device. The values of these statistics should match. See Call Statistics Screen, page 7-15 for information about displaying these statistics. Check the AvgJtr and the MaxJtr statistics. A large variance between these statistics might indicate a problem with jitter on the network or periodic high rates of network activity. See Call Statistics Screen, page 7-15 for information about displaying these statistics. OL-23092-01 Cisco Unified IP Phone Administration Guide for Cisco Unified Communications Manager 8.5 9-11