This chapter provides information that can assist you in troubleshooting problems with your Cisco Unified IP Phone or with your IP telephony network. It also explains how to clean and maintain your phone.
For additional troubleshooting information, refer to the Using the 79xx Status Information For Troubleshooting tech note. That document is available to registered Cisco.com users at this URL:
After installing a Cisco Unified IP Phone into your network and adding it to Cisco Unified Communications Manager, the phone should start up as described in the Verifying the Phone Startup Process. If the phone does not start up properly, see the following sections for troubleshooting information:
Symptom: The Cisco Unified IP Phone Does Not Go Through its Normal Startup Process
When you connect a Cisco Unified IP Phone into the network port, the phone should go through its normal startup process as described in Verifying the Phone Startup Process and the LCD screen should display information. If the phone does not go through the startup process, the cause may be faulty cables, bad connections, network outages, lack of power, and so on. Or, the phone may not be functional.
To determine whether the phone is functional, follow these suggestions to systematically eliminate these other potential problems:
1. Verify that the network port is functional:
– Exchange the Ethernet cables with cables that you know are functional.
– Disconnect a functioning Cisco Unified IP Phone from another port and connect it to this network port to verify the port is active.
– Connect the Cisco Unified IP Phone that will not start up to a different network port that is known to be good.
– Connect the Cisco Unified IP Phone that will not start up directly to the port on the switch, eliminating the patch panel connection in the office.
2. Verify that the phone is receiving power:
– If you are using external power, verify that the electrical outlet is functional.
– If you are using in-line power, use the external power supply instead.
– If you are using the external power supply, switch with a unit that you know to be functional.
3. If the phone still does not start up properly, power up the phone with the handset off-hook. When the phone is powered up in this way, it attempts to launch a backup software image.
4. If the phone still does not start up properly, perform a factory reset of the phone. For instructions, see Performing a Factory Reset.
If after attempting these solutions, the LCD screen on the Cisco Unified IP Phone does not display any characters after at least five minutes, contact a Cisco technical support representative for additional assistance.
Symptom: The Cisco Unified IP Phone Does Not Register with Cisco Unified Communications Manager
If the phone proceeds past the first stage of the startup process (LED buttons flashing on and off) but continues to cycle through the messages displaying on the LCD screen, the phone is not starting up properly. The phone cannot successfully start up unless it is connected to the Ethernet network and it has registered with a Cisco Unified Communications Manager server.
These sections can assist you in determining the reason the phone is unable to start up properly:
As the phone cycles through the startup process, you can access status messages that might provide you with information about the cause of a problem. See Status Messages Screen for instructions about accessing status messages and for a list of potential errors, their explanations, and their solutions.
Checking Network Connectivity
If the network is down between the phone and the TFTP server or Cisco Unified Communications Manager, the phone cannot start up properly. Ensure that the network is currently running.
Verifying TFTP Server Settings
You can determine the IP address of the TFTP server used by the phone by pressing the Settings button on the phone, choosing Network Configuration > IPv4 and scrolling to the TFTP Server 1 option.
If you have assigned a static IP address to the phone, you must manually enter a setting for the TFTP Server 1 option. See Network Configuration Menu.
If you are using DHCP, the phone obtains the address for the TFTP server from the DHCP server. Check the IP address configured in Option 150.
You can also enable the phone to use an alternate TFTP server. Such a setting is particularly useful if the phone was recently moved from one location to another. See Network Configuration Menu for instructions.
Verifying IP Addressing and Routing
You should verify the IP addressing and routing settings on the phone. If you are using DHCP, the DHCP server should provide these values. If you have assigned a static IP address to the phone, you must enter these values manually.
On the Cisco Unified IP Phone, choose Settings > Network Configuration > IPv4 Configuration, and look at the following options:
DHCP Server—If you have assigned a static IP address to the phone, you do not need to enter a value for the DHCP Server option. However, if you are using a DHCP server, this option must have a value. If it does not, check your IP routing and VLAN configuration. Refer to the Troubleshooting Switch Port and Interface Problems document, available at this URL: http://www.cisco.com/warp/customer/473/53.shtml
IP Address, Subnet Mask, Default Router—If you have assigned a static IP address to the phone, you must manually enter settings for these options. See Network Configuration Menu for instructions.
If you are using DHCP, check the IP addresses distributed by your DHCP server. Refer to the Understanding and Troubleshooting DHCP in Catalyst Switch or Enterprise Networks document, available at this URL:http://www.cisco.com/warp/customer/473/100.html#41
Verifying DNS Settings
If you are using DNS to refer to the TFTP server or to Cisco Unified Communications Manager, you must ensure that you have specified a DNS server. Verify this setting by pressing the Settings button on the phone, choosing Network Configuration, and scrolling to the DNS Server 1 option. You should also verify that there is a CNAME entry in the DNS server for the TFTP server and for the Cisco Unified Communications Manager system.
You must also ensure that DNS is configured to do reverse look-ups.
On the Cisco Unified IP Phone, press the Settings button, choose Device Configuration, and look at the Unified CM Configuration options. The Cisco Unified IP Phone attempts to open a TCP connection to all the Cisco Unified Communications Manager servers that are part of the assigned Cisco Unified Communications Manager group. If none of these options contain IP addresses or show Active or Standby, the phone is not properly registered with Cisco Unified Communications Manager. See Checking Network Connectivity for tips on resolving this problem.
Cisco CallManager and TFTP Services Are Not Running
If the Cisco CallManager or TFTP services are not running, phones may not be able to start up properly. However, in such a situation, it is likely that you are experiencing a system-wide failure, and other phones and devices are unable to start up properly.
If the Cisco CallManager service is not running, all devices on the network that rely on it to make phone calls will be affected. If the TFTP service is not running, many devices will not be able to start up successfully.
To start a service, follow these steps:
Step 1 From Cisco Unified Communications Manager Administration, choose Cisco Unified Serviceability from the Navigation drop-down list and click Go.
Step 2 Choose Tools > Control Center - Feature Services.
Step 3 Choose the primary Cisco Unified Communications Manager server from the Server drop-down list.
The window displays the service names for the server that you chose, the status of the services, and a service control panel to start or stop a service.
Step 4 If a service has stopped, click its radio button and then click the Start button.
The Service Status symbol changes from a square to an arrow.
Note A service must be activated before it can be started or stopped. To activate a service, choose Tools > Service Activation.
Creating a New Configuration File
If you continue to have problems with a particular phone that other suggestions in this chapter do not resolve, the configuration file may be corrupted.
To create a new configuration file, follow these steps:
Step 1 From Cisco Unified Communications Manager, choose Device > Phone > Find to locate the phone experiencing problems.
Step 2 Choose Delete to remove the phone from the Cisco Unified Communications Manager database.
Note ● When you remove a phone from the Cisco Unified Communications Manager database, its configuration file is deleted from the Cisco Unified Communications Manager TFTP server. The phone’s directory number or numbers remain in the Cisco Unified Communications Manager database. They are called “unassigned DNs” and can be used for other devices. If unassigned DNs are not used by other devices, delete them from the Cisco Unified Communications Manager database. You can use the Route Plan Report to view and delete unassigned reference numbers. Refer to Cisco Unified Communications Manager Administration Guide for more information.
Changing the buttons on a phone button template, or assigning a different phone button template to a phone, may result in directory numbers that are no longer accessible from the phone. The directory numbers are still assigned to the phone in the Cisco Unified Communications Manager database, but there is no button on the phone with which calls can be answered. These directory numbers should be removed from the phone and deleted if necessary.
Registering the Phone with Cisco Unified Communications Manager
A Cisco Unified IP Phone can register with a Cisco Unified Communications Manager server only if the phone has been added to the server or if auto-registration is enabled. Review the information and procedures in Adding Phones to the Cisco Unified Communications Manager Database to ensure that the phone has been added to the Cisco Unified Communications Manager database.
To verify that the phone is in the Cisco Unified Communications Manager database, choose Device > Phone > Find from Cisco Unified Communications Manager Administration to search for the phone based on its MAC Address. For information about determining a MAC address, see Determining the MAC Address for a Cisco Unified IP Phone.
If the phone is already in the Cisco Unified Communications Manager database, its configuration file may be damaged. See Creating a New Configuration File for assistance.
Symptom: Cisco Unified IP Phone Unable to Obtain IP Address
If a phone is unable to obtain an IP address when it starts up, the phone may be not be on the same network or VLAN as the DHCP server, or the switch port to which the phone is connected may be disabled. Make sure that the network or VLAN to which the phone is connected has access to the DHCP server, and make sure that the switch port is enabled.
Cisco Unified IP Phone Resets Unexpectedly
If users report that their phones are resetting during calls or while idle on their desk, you should investigate the cause. If the network connection and Cisco Unified Communications Manager connection are stable, a Cisco Unified IP Phone should not reset on its own.
Typically, a phone resets if it has problems connecting to the Ethernet network or to Cisco Unified Communications Manager. These sections can help you identify the cause of a phone resetting in your network:
Verify that the Ethernet connection to which the Cisco Unified IP Phone is connected is up. For example, check whether the particular port or switch to which the phone is connected is down and that the switch is not rebooting. Also make sure that there are no cable breaks.
Identifying Intermittent Network Outages
Intermittent network outages affect data and voice traffic differently. Your network might have been experiencing intermittent outages without detection. If so, data traffic can resend lost packets and verify that packets are received and transmitted. However, voice traffic cannot recapture lost packets. Rather than retransmitting a lost network connection, the phone resets and attempts to reconnect its network connection.
If you are experiencing problems with the voice network, you should investigate whether an existing problem is simply being exposed.
Verifying DHCP Settings
The following suggestions can help you determine if the phone has been properly configured to use DHCP:
2. Verify that the DHCP server has been set up properly.
3. Verify the DHCP lease duration. Cisco recommends that you set it to 8 days.
Cisco Unified IP Phones send messages with request type 151 to renew their DHCP address leases. If the DHCP server expects messages with request type 150, the lease will be denied, forcing the phone to restart and request a new IP address from the DHCP server.
Checking Static IP Address Settings
If the phone has been assigned a static IP address, verify that you have entered the correct settings. See Network Configuration Menu for more information.
Verifying the Voice VLAN Configuration
If the Cisco Unified IP Phone appears to reset during heavy network usage (for example, following extensive web surfing on a computer connected to the same switch as the phone), it is likely that you do not have a voice VLAN configured.
Verifying that the Phones Have Not Been Intentionally Reset
If you are not the only administrator with access to Cisco Unified Communications Manager, you should verify that no one else has intentionally reset the phones.
You can check whether a Cisco Unified IP Phone received a command from Cisco Unified Communications Manager to reset by pressing the Settings button on the phone and choosing Status > Network Statistics. If the phone was recently reset one of these messages appears:
Reset-Reset—Phone closed due to receiving a Reset/Reset from Cisco Unified Communications Manager Administration.
Reset-Restart—Phone closed due to receiving a Reset/Restart from Cisco Unified Communications Manager Administration.
Eliminating DNS or Other Connectivity Errors
If the phone continues to reset, follow these steps to eliminate DNS or other connectivity errors:
In most cases, a phone will restart if it powers up by using external power but loses that connection and switches to PoE. Similarly, a phone may restart if it powers up by using PoE and then gets connected to an external power supply.
Troubleshooting Cisco Unified IP Phone Security
Table 9-1 provides troubleshooting information for the security features on the Cisco Unified IP Phone. For information relating to the solutions for any of these issues, and for additional troubleshooting information about security and encryption, refer to Cisco Unified Communications Manager Security Guide.
Table 9-1 Cisco Unified IP Phone Security Troubleshooting
Device authentication error.
CTL file does not have a Cisco Unified Communications Manager certificate or has an incorrect certificate.
Phone cannot authenticate CTL file.
The security token that signed the updated CTL file does not exist in the CTL file on the phone.
Phone cannot authenticate any of the configuration files other than the ITL file.
The configuration file may not be signed by the corresponding certificate in the phone’s Trust List.
Phone cannot authenticate any of the configuration files other than the CTL file.
The configuration file may not be signed by the corresponding certificate in the phone’s Trust List.
Phone does not register with Cisco Unified Communications Manager.
The CTL file does not contain the correct information for the Cisco Unified Communications Manager server.
Phone does not request signed configuration files.
The CTL file does not contain any TFTP entries with certificates.
802.1X Enabled on Phone but Not Authenticating
Phone cannot obtain a DHCP-assigned IP address
These errors typically indicate that 802.1X is enabled on the phone, but the phone is unable to authenticate.
These errors typically indicate that the phone has completed a factory reset while 802.1X was enabled. A factory reset deletes the shared secret, which is required for 802.1X authentication and network access. To resolve this, you have two options:
Temporarily disable 802.1X on the switch.
Temporarily move the phone to a network environment that is not using 802.1X authentication.
Once the phone starts up normally in one of these conditions, you can access the 802.1X configuration menus and re-enter the shared secret.
Phone does not register with Cisco Unified Communications Manager
Phone status display as “Configuring IP” or “Registering”
Cannot access phone menus to verify 802.1X status
General Troubleshooting Tips
Table 9-2 provides general troubleshooting information for the Cisco Unified IP Phone.
Table 9-2 Cisco Unified IP Phone Troubleshooting
Connecting a Cisco Unified IP Phone to another Cisco Unified IP Phone
Cisco does not support connecting an IP phone to another IP phone through the PC port. Each IP phone should directly connect to a switch port. If phones are connected together in a line (by using the PC port), the phones will not work.
Poor quality when calling digital cell phones using the G.729 protocol.
In Cisco Unified Communications Manager, you can configure the network to use the G.729 protocol (the default is G.711). When using G.729, calls between an IP phone and a digital cellular phone will have poor voice quality. Use G.729 only when absolutely necessary.
Prolonged broadcast storms cause IP phones to reset, or be unable to make or answer a call.
A prolonged Layer 2 broadcast storm (lasting several minutes) on the voice VLAN may cause IP phones to reset, lose an active call, or be unable to initiate or answer a call. Phones may not come up until a broadcast storm ends.
Moving a network connection from the phone to a workstation.
If you are powering your phone through the network connection, 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.
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 for details.
The phone resets when it loses contact with the Cisco Unified Communications Manager software. This lost connection can be due to any network connectivity disruption, including cable breaks, switch outages, and switch reboots.
LCD display issues.
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.
Dual-Tone Multi-Frequency (DTMF) delay.
When you are on a call that requires keypad input, if you press the keys too quickly, some of them might not be recognized.
Codec mismatch between the phone and another device.
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.
Sound sample mismatch between the phone and another device.
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.
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 10 Half (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:
To resolve this problem, re-enable the port from the switch.
When at least one person in a call does not receive audio, IP connectivity between phones is not established. Check the configurations in routers and switches to ensure that IP connectivity is properly configured.
Peer Firmware Sharing fails.
If the Peer Firmware Sharing fails, the phone will default to using the TFTP server to download firmware. Access the log messages stored on the remote logging machine to help debug the Peer Firmware Sharing feature.
Note These log messages are different than the log messages sent to the phone log.
Cisco VT Advantage/Unified Video Advantage (CVTA)
If you are having problems getting CVTA to work, make sure that the PC Port is enabled, and that CDP is enabled on the PC port.
The phone does not have a DHCP IP address, is unable to register to Cisco Unified Communications Manager, and shows a Configuring IP or Registering message.
Verify the following:
1. The Ethernet cable is attached.
2. The Cisco CallManager service is running on the Cisco Unified Communications Manager server.
3. Both phones are registered to the same Cisco Unified Communications Manager.
4. Audio server debug and capture logs are enabled for both phones. If needed, enable Java debug.
Call established with the iLBC protocol does not show that the iLBC codec is being used
Call statistics display does not show iLBC as the receiver/sender codec.
1. Check the following by using Cisco Unified Communications Manager Administration:
– Both phones are in the iLBC device pool.
– The iLBC device pool is configured with the iLBC region.
– The iLBC region is configured with the iLBC codec.
2. Capture a sniffer trace between the phone and Cisco Unified Communications Manager and verify that SCCP messages, OpenReceiveChannel, and StationMediaTransmit messages have media payload type value equal to 86. If so, the problem is with the phone; otherwise, the problem is with the Cisco Unified Communications Manager configuration.
3. Enable audio server debug and capture logs from both phones. If needed, enable Java debug.
General Troubleshooting Tips for the Cisco Unified IP Phone Expansion Module
Table 9-3 provides general troubleshooting information for the Cisco Unified IP Phone Expansion Module 7914.
Table 9-3 Cisco Unified IP Phone Expansion Module 7914 Troubleshooting
No display on the Cisco Unified IP Phone Expansion Module.
Verify that all of the cable connections are correct.
Verify that you have power to the Cisco Unified IP Phone Expansion Module.
Lighted buttons on the first Cisco Unified IP Phone Expansion Module are all red.
Verify that the Cisco Unified IP Phone Expansion Module is configured in Cisco Unified Communications Manager.
Lighted buttons on the second Cisco Unified IP Phone Expansion Module are all amber.
Verify that the Cisco Unified IP Phone Expansion Module is configured in Cisco Unified Communications Manager.
Resetting or Restoring the Cisco Unified IP Phone
There are two general methods for resetting or restoring the Cisco Unified IP Phone:
Deletes the CTL file from the phone and restarts the phone.
Performing a Factory Reset
When you perform a factory reset of the Cisco Unified IP Phone, the following information is erased or reset to its default value:
User configuration settings—Reset to default values
Network configuration settings—Reset to default values
Locale information—Reset to default values
Phone application—Erased (phone recovers by loading the appropriate default load file (term62.default.loads, term61.default.loads, term42.default.loads, or term41.defaults.loads) depending on the phone model)
Before you perform a factory reset, ensure that the following conditions are met:
The phone must be on a DHCP-enabled network.
A valid TFTP server must be set in DHCP option 150 or option 66 on the DHCP server.
The default load file for your phone model and the files specified in that file should be available on the TFTP server that is specified by the DHCP packet.
To perform a factory reset of a phone, perform the following steps:
Step 1 Unplug the power cable from the phone and then plug it back in.
The phone begins its power-up cycle.
Step 2 While the phone is powering up, and before the Speaker button flashes on and off,
press and hold #.
Continue to hold # until each line button flashes on and off in sequence in amber.
Step 3 Release # and press 123456789*0#.
You can press a key twice in a row, but if you press the keys out of sequence, the factory reset will not take place.
After you press these keys, the line buttons on the phone flash red, and the phone goes through the factory reset process.
Do not power down the phone until it completes the factory reset process, and the main screen appears.
Using the Quality Report Tool
The Quality Report Tool (QRT) is a voice quality and general problem-reporting tool for the Cisco Unified IP Phone. The QRT feature is installed as part of the Cisco Unified Communications Manager installation.
You can configure users’ Cisco Unified IP Phones with QRT. When you do so, users can report problems with phone calls by pressing the QRT softkey. This softkey is available only when the Cisco Unified IP Phone is in the Connected, Connected Conference, Connected Transfer, and/or OnHook states.
When a user presses the QRT softkey, a list of problem categories appears. The user selects the appropriate problem category, and this feedback is logged in an XML file. Actual information logged depends on the user selection, and whether the destination device is a Cisco Unified IP Phone.
For more information about using QRT, refer to Cisco Unified Communications Manager Features and Services Guide.
Monitoring the Voice Quality of Calls
To measure the voice quality of calls that are sent and received within the network, Cisco Unified 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.
MOS-LQK metrics—Use a numeric score to estimate the relative voice listening quality. The Cisco Unified IP Phone calculates the mean opinion score (MOS) for listening quality (LQK) based audible concealment events due to frame loss in the preceding 8 seconds, and includes perceptual weighting factors such as codec type and frame size.
MOS LQK scores are produced by a Cisco proprietary algorithm, Cisco Voice Transmission Quality (CVTQ) index. Depending on the MOS LQK version number, these scores might be compliant with the International Telecommunications Union (ITU) standard P.564. This standard defines evaluation methods and performance accuracy targets that predict listening quality scores based on observation of actual network impairment.
Note Concealment ratio and concealment seconds are primary measurements based on frame loss while MOS LQK scores project a “human-weighted” version of the same information on a scale from 5 (excellent) to 1 (bad) for measuring listening quality.
Listening quality scores (MOS LQK) relate to the clarity or sound of the received voice signal. Conversational quality scores (MOS CQ such as G.107) include impairment factors, such as delay, that degrade the natural flow of conversation.
To use 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 important to distinguish significant changes from random changes in metrics. Significant changes are scores that change about 0.2 MOS or greater and persist in calls that last longer than 30 seconds. Conceal Ratio changes should indicate greater than 3 percent frame loss.
MOS LQK scores can vary based on the codec that the Cisco Unified IP Phone uses. The following codecs on the Cisco Unified IP Phones 7962G and 7942G provide these maximum MOS LQK scores under normal conditions with zero frame loss:
G.711 gives 4.5
G.722 gives 4.5
G.728/iLBC gives 3.9
G.729 A/AB gives 3.8
The following codecs on the Cisco Unified IP Phones 7961G/G-GE and 7941G/G-GE provide these maximum MOS LQK scores under normal conditions with zero frame loss:
G.711 codec gives 4.5 score
G.729A/ AB gives 3.7
Note ● CVTQ does not support wideband (7 kHz) speech codecs, as ITU has not defined the extension of the technique to wideband. Therefore, MOS 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/low packet loss, and lower scores (approximately 3.5) indicate low quality/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.
When you observe significant and persistent changes to metrics, use Table 9-5 for general troubleshooting information:
Table 9-5 Changes to Voice Quality Metrics
MOS LQK scores decrease significantly
Network impairment from packet loss or high jitter:
Average MOS LQK decreases could indicate widespread and uniform impairment.
Individual MOS LQK decreases indicate bursty impairment.
Cross-check with Conceal Ratio and Conceal Seconds for evidence of packet loss and jitter.
MOS LQK scores decrease 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.
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.
Note Voice quality metrics do not account for noise or distortion, only frame loss.
Where to Go for More Troubleshooting Information
If you have additional questions about troubleshooting the Cisco Unified IP Phones, several Cisco.com web sites can provide you with more tips. Choose from the sites available for your access level.
To clean your Cisco Unified IP phone, use only a dry soft cloth to gently wipe the phone and the LCD screen. Do not apply liquids or powders directly on the phone. As with all non-weather-proof electronics, liquids and powders can damage the components and cause failures.