To restore factory default configuration of a managed phone, right-click on the phone in the device list and select the Factory Defaults option. This will delete any non-default configuration on the phone.
If you have the phone any extensions configured on the phones ports, the phone will receive this configuration when it starts up(If option 66 is correctly configured on the DHCP server). To have the phone remain in a factory default configuration, first delete or un-assign extensions on the phones ports and then factory default the phone.
Note: It is recommended that any phones that are added be factory defaulted as a part of their initial configuration. It is not possible to reassign lines on devices if they are already assigned to extensions, the association to the extension must first be deleted. Factory defaulting phones as you install them deletes any extensions configured in a previous installation and ensures that the Com.X is able to configure all lines seamlessly.
Some handsets, such as Yealink models featuring more recent firmware, prevent the issuing of factory default commands remotely. These devices should be defaulted manually, or using the phone’s configuration GUI.