There are three popular types of limit switch on laser machines. Mechanical contact and magnetic types have two pieces of wire. Proximity type needs power, so it has three pieces of wire.
Different laser controllers has different V+ output. If we are using the proximity type, we need to make sure its voltage rating matches the V+ output. Also, they are either normally closed or normally open. Under laser controller setting, we need to set the limit switch signal active high or active low to match that. For mechanical contact and magnetic types, the V+ is not needed.
When the switch is triggered, the Lm pin voltage value will change, from 5V to 0V for example.
Many controllers have two limit input for each axis at min and max travel range(Lm X+ and Lm X- for example). To use the homing of the laser controller, only one sensor is required for each axis.