Advanced Configuration Mode (SIP)
From Zenitel Wiki
When devices are used in a SIP System, some additional settings are available when entering the Advanced Configuration Mode.
Firmware version 7 and later
From version 7.1 the Advanced Mode is easily accessible in the top right corner:
Firmware version 5.x and 6.x
To enter the Advanced Configuration Mode go to Main -> Recovery -> Preferences
Type the offline password and tick off the Configuration check box and click Save.
Offline Password: 1851
To revert back to Basic Configuration mode, uncheck the same flag.