Yealink SIP-T54S Administrator's Manual page 1022

Administrator's Guide for SIP-T2 Series/T19(P) E2/T4 Series/T5 Series/CP860/CP920 IP Phones
Click Reset to factory in the Reset to factory field.
2.
The web user interface prompts the message "Do you want to reset to factory?".
Click OK to confirm the resetting.
3.
The IP phone will be reset to factory sucessfully after startup.
Reset of your phone may take a few minutes. Do not power off until the phone starts up
Note
successfully.
How to reset the IP phone to custom factory configurations?
Procedure
Configuration changes can be performed using the following methods.
Central
Provisioning
(Configuration
File)
Web User Interface
996
Configure the Custom Factory Configuration
feature.
Parameter:
static.features.custom_factory_config.enable
<y0000000000xx>.c
fg
Configure the access URL of the custom
factory configuration files.
Parameter:
static.custom_factory_configuration.url
Configure the access URL of the custom
factory configuration files.
Navigate to:
http://<phoneIPAddress>/servlet?p=settings
-config&q=load