Yealink SIP-T4X Administration Manual page 255

Administrator's Guide for SIP-T4X IP Phones
Do one of the following:
Reset another available IP address for the IP phone.

Check network configuration via phone user interface at the path

Menu->Advanced->Network->WAN Port->IPv4 (or IPv6). If the Static IP is selected,
select DHCP instead.
Reset your phone to factory configurations after you have tried all troubleshooting
suggestions but do not resolve the problem. Note that all custom settings will be
overwritten after resetting.
To reset your phone via web user interface:
1. Click on Settings->Upgrade.
2. Click Reset in the Reset to Factory Setting field.
The web user interface prompts the message "Do you want to reset to factory?".
3. Click OK to confirm the resetting.
The phone will be reset to factory sucessfully after startup.
Note
Reset of the phone may take a few minutes. Do not power off until the phone starts up
successfully.
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