<p>The switch comprises lamps and switching devices which are assigned to individual stair sections. The switching devices work together with movement alarms which monitor at least a single stair section and switch on the supply for the lamps assigned to this section. Each movement alarm monitors an up-going and a down-going stair section and the power supply for their lamps. Each movement alarm has an optical system and at least one sensor with associated circuitry. The optical system is subdivided into two separate evaluation regions to each of which one sensor with its circuitry is assigned. One evaluation region is for the up-going stair section, one for the down-going one.</p>
