Safety unit with built-in key switch, especially for Class 4 show laser lights. Developed to shut off laser projectors by using the interlock connection interface. In case of a blackout, with this unit the laser show will only continue by pushing the restart button. This safety unit can be connected to the standard RS-232 interlock interface (Pin 1 & 2) of a laser projector. Including a 5 meter Interlock connection cable.