Abstract: A proximity detection system for a mobile device. The system includes an infrared emitter to emit infrared light, an infrared detector to detect the infrared light after reflection from a target and provide a detector signal; and a signal processing subsystem. The signal processing subsystem is configured to control the proximity detection system into a first, detect mode for detecting proximity of the target as the target approaches the mobile device, and after detection of the target to control the proximity detection system into a second, release mode for detecting movement of the target out of proximity to the mobile device. The signal processing subsystem also controls the proximity detection system such that, contrary to conventional hysteresis, for a given proximity of the target the detector signal reduces when the mode switches from the detect mode to the release mode, thus increasing reliability.