Intrusion detector for swimming pools has microphone in gravel trench prevents children drowning

摘要

The intrusion detector (10) is an electroacoustic transducer (12) with hollow resonator (11) buried in a gravel filled trench surrounding the pool with a processor (20) to sound and alarm (SA) when the sound energy in a specific frequency band exceeds a dynamic threshold determined by comparison with a signal emitted by the transducer.