Transparent material monitoring device, e.g. for glass panes

The monitoring unit monitors light conducting transparent material e.g. glass panels regarding breakage and danger points, by coupling in and evaluating using light waves lying in the IR range. With two units designed equipped with SMD LED for light rails (2,3) also a reference conductor arranged at the object to be monitored. One light rail (2) is designed for coupling in light and the other light rail (3) as detector. The resulting signals are compared in an assigned evaluation circuit. With deviation from a desired value, an acoustic and/or optical signal is activated. The light rails consist of PCB strip equipped with SMD LED.