he GLSL system consists of the two components light transmitters and light receiver.
The light-transmitter emitts ray an invisible, modulated infra-red light screen out. The receiver consists of a lining up of receiver modules.
Sensitivity is so adjustable that also smallest holes (≥1mm Ø) can be entered.
With the occurrence of a hole the output transistors conduct the relay and the LED " hole detected " light up.