Before you sell it:
There is a reset on the rear panel.
Carefully insert the point of a pen or an
unwound paperclip into the opening.
•If you press the factory default button for less than
1/2 a second, the unit will continue to run as normal.
•If you press the factory default button for more than
15 seconds, when you release it, the Gateway will
perform a factory reset, clear all settings and configurations,
and reboot.
That will return the unit to factory defaults. You sell it with the manual. The new owner will put in their own key and security setup. No do not remove the serial number.
If you don't have a manual
then download it here.
Ron