Safety swith on lid on a KC40

Hi i have a KC40 laser engraver - with almost normal pins on the 40W power supply / p+ g / k- k+ / g in 5v / none of these are connected - but the power supply is connected to the digital display with a ethernet cable controlling the 40W power supply as far as i can find out this is a no name power supply. My question is there is no protection when opening the lid - the laser can fire - i want to build that safety in - isn’t it normally betveem k- and k+ that’s done - but with k- and k+ not used it must be a normally open function - as a safety circuit i prefer a normally closed circuit. and i guess the functions for controlling the power supply is done by the ethernet cable ?