Abstract: A circuit arrangement for detecting foreign bodies on a transparent element, particularly in a motor vehicle, including a dynamically driven reflection light barrier having a light emitting diode, a pulse generator connected electrically to the light emitting diode to produce light pulses and a phototransistor having a collector and an emitter. The phototransistor and the light emitting diode are positioned on the transparent element so the phototransistor receives reflected light produced by the LED. A resistor connects a power supply including a circuit, which can double an operating voltage in the motor vehicle, to the collector of the phototransistor. To neutralize the effects of stray light, e.g.