Presence detector for ceiling mounting indoors. The sensor module detects moving heat sources (e.g., people) within an adjustable detection range and initiates a stair light timer. The sensor module needs to be completed with a compatible insert. It can be mounted in a 60mm flush-mounted box or in the surface-mounted housing available as an accessory. The sensor module features a light sensor with an adjustable brightness threshold, ensuring that the lighting is only activated below a certain brightness level. Thanks to the presence function, the sensor module can turn off the lighting even when a person is present if there is sufficient natural light. The switchable light control (only in combination with dimmable inserts) ensures a nearly constant brightness in the room. The sensor module continuously measures the brightness in the room and adjusts it to a set target value.