Performing a basic reset of a Cisco Unified IP Phone
provides a way to recover if the phone experiences an error and provides a way
to reset or restore various configuration and security settings.
The following table describes the ways to perform a basic
reset. You can reset a phone with any of these operations after the phone has
started up. Choose the operation that is appropriate for your situation.
Table 1 Basic Reset Methods
Directories and then press
Resets any user and network setup changes that you have made,
but that the phone has not written to its flash memory, to previously saved
settings, then restarts the phone.
To reset settings, press
Applications and choose
Settings > Reset
Settings > Network.
Resets user and network setup settings to their default
values, and restarts the phone.
To reset the CTL file, press
Applications and choose
Settings > Reset
Settings > Security.
measure the voice quality of calls that are sent and received within the
network, Cisco IP Phones use these statistical metrics that are based on
concealment events. The DSP plays concealment frames to mask frame loss in the
voice packet stream.
Concealment Ratio metrics—Show the ratio of concealment frames over total speech frames. An interval conceal ratio is calculated every 3 seconds.
Concealed Second metrics—Show the number of seconds in which the DSP plays concealment frames due to lost frames. A severely "concealed second" is a second in which the DSP plays more than five percent concealment frames.
ratio and concealment seconds are primary measurements based on frame loss. A
Conceal Ratio of zero indicates that the IP network is delivering frames and
packets on time with no loss.
access voice quality metrics from the Cisco IP Phone using the Call Statistics
screen or remotely by using Streaming Statistics.
When you observe significant and persistent changes to metrics, use the following table for general troubleshooting information.
Table 2 Changes to Voice Quality Metrics
Conceal Ratio and Conceal Seconds increase significantly
Network impairment from packet loss or high jitter.
Conceal Ratio is near or at zero, but the voice quality is poor.
Noise or distortion in the audio channel such as echo or audio levels.
Tandem calls that undergo multiple encode/decode such as calls to a cellular network or calling card network.
Acoustic problems coming from a speakerphone, handsfree cellular phone or wireless headset.
Check packet transmit (TxCnt) and packet receive (RxCnt) counters to verify that voice packets are flowing.
MOS LQK scores decrease significantly
Network impairment from packet loss or high jitter levels:
Average MOS LQK decreases may indicate widespread and uniform impairment.
Individual MOS LQK decreases may indicate bursty impairment.
Cross-check the conceal ratio and conceal seconds for evidence of packet loss and jitter.
MOS LQK scores increase significantly
Check to see if the phone is using a different codec than expected (RxType and TxType).
Check to see if the MOS LQK version changed after a firmware upgrade.
Voice quality metrics do not account for noise or distortion, only frame loss.
Voice Quality Metrics
When using the metrics for monitoring voice quality, note the
typical scores under normal conditions of zero packet loss and use the metrics
as a baseline for comparison.
It is also important to distinguish significant changes from
random changes in metrics. Significant changes are scores that change about 0.2
MOS or more and persist in calls that last longer than 30 seconds. Conceal
ratio changes indicate a frame loss greater than 3 percent.
The MOS LQK scores can vary based on the codec that the Cisco
Unified IP Phone uses. The following codecs provide these corresponding maximum
MOS LQK scores under normal conditions with zero frame loss for Cisco Unified
Phone 8941 and 8945:
G.711: 4.5 MOS LQK
G.722: 4.5 MOS LQK
G.728/iLBC: 3.9 MOS LQK
G729A/AB: 3.7 MOS LQK
Cisco Voice Transmission
Quality (CVTQ) does not support wideband (7 kHz) speech codecs, because ITU has
not defined the extension of the technique to wideband. Therefore, MOS LQK
scores that correspond to G.711 performance are reported for G.722 calls to
allow basic quality monitoring, rather than not reporting an MOS score.
Reporting G.711-scale MOS
scores for wideband calls through the use of CVTQ allows basic-quality
classifications to be indicated as good/normal or bad/abnormal. Calls with high
scores (approximately 4.5) indicate high quality or a low packet loss, and
lower scores (approximately 3.5) indicate low quality or a high packet loss.
Unlike MOS, the conceal
ratio and concealed seconds metrics remain valid and useful for both wideband
and narrowband calls.
A conceal ratio of zero indicates that the IP network is
delivering frames and packets on time with no loss.
The phones do not support video metrics. This means that you can't see the following information about the video portion of a call:
Cisco IP Phone Cleaning
To clean your Cisco IP Phone, use only a dry soft
cloth to gently wipe the phone and the phone screen. Do not apply liquids or
powders directly to the phone. As with all non-weatherproof electronics,
liquids and powders can damage the components and cause failures.
When the phone is in sleep mode, the screen is blank and
Select button is not lit. When the phone is in
this condition, you can clean the screen, as long as you know that the phone
will remain asleep until after you finish cleaning.