Yealink SIP-T2XP, Administration Manual

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Troubleshooting
95
The phone LCD screen prompts ―No Service‖ message when there is no any available
SIP account on the IP phone.
Do one of the following:

Confirm if any account is actively registered on the IP phone at the path
Menu->Status->More ->Accounts.

Check if the SIP parameters of the account have been set up correctly.
Do one of the following:

Ensure that the target firmware is not the same as the current used firmware.

Ensure that the target firmware is applicable to the phone model.

Ensure that the current or the target firmware is not protected.

Ensure that the power is on and the network is available in the process of
upgrading.

Ensure the web browser is open when upgrading the firmware using the web user
interface.
Check if you have configured your phone to obtain the time and date from the NTP
server automatically. If your phone is unable to access the NTP server, configure the time
and date manually.
During a call, you may experience poor audio, including intermittent voice, low volume,
echo or other noise. The root cause of audio anomalies can be difficult to diagnose.

Problems may occur simply because the users are seated too far out of
recommended microphone range and sound faint, or are seated too close to
sensitive microphones and cause feedback.

Intermittent voice is mainly caused by packet loss and jitter. Packet loss may due to
network congestion. Jitter is mainly due to message recombination of transmission
or receiving equipment, such as timeout handling, retransmission mechanism or
buffer under run.

Noisy equipment, such as a computer or a fan, may make it difficult for hear the