Passive infra-red detector, which reacts to moving heat sources (people, vehicles etc.). If the motion detector identifies a change in the heat rays in its field of detection, it switches, depending on the set light level, to the connected device, (e.g. lighting) for a set time. When the heat source leaves the detection area, the motion detector switches the devices off again according to a pre-selected time (3 seconds up to 20 minutes). The short-pulse function is another extra which is set via the built-in TIME-potentiometer under the cover ring on the sensor. This allows, for example, escalators in large buildings to be automatically activated.