Fundamentally, there are many possibilities when it comes to detecting presence in a room. There are video cameras with suitable pattern recognition to detect persons, noise detection systems and systems with classic motion sensors which interpret changes in the input signal from the room area the sensor is targeting as movements. This sensor can be a video camera with simple image evaluation, an ultrasound sensor, a passive infrared sensor or a high-frequency sensor.
Commercially available light management systems for indoor use predominantly rely on motion detection via passive infrared sensors. In some cases, high-frequency sensors are used. Acoustic presence detection is occasionally used in addition to one of the aforementioned sensor systems in sanitary areas and staircases, e.g. in geriatric care homes, where mere motion detection is not sufficiently reliable. Other options are only used in special applications.