Get introduced to the interesting operation and functionality of light barriers. A teaching booklet explains in detail the components used. It also introduces you to the circuit technology of a Schmitt trigger in connection with photoresistors. The assembly is explained step-by-step and in detail. Measurement points and calculation examples make the circuit easier to understand. Ideal for educational purposes as well. Application examples include light barriers, dusk switches, counting devices, alarm systems, etc. When using an NTC, it can also be used as a temperature switch.