STEINEL high-frequency sensors (HF) are ideal for areas such as toilet facilities, offices and corridors, as they can detect movement even through glass or thin walls. Unlike passive infrared (PIR) technology, which relies on the heat radiation of people, HF sensors work with electromagnetic waves. This enables them to reliably detect motion even when the line of sight is obstructed. While PIR sensors require a direct line of sight, HF sensors offer more flexibility in more complex room structures. Another advantage of HF technology is that it is not dependent on external influences such as light or temperature conditions. The concealed installation makes them particularly vandal-proof, and models with Bluetooth technology enable smart control via an app. Compared to PIR and ultrasonic sensors, HF sensors are the better choice especially in sensitive areas with many obstacles where discreet installation is desired.