Infra-sonic detector, and alarms including same

摘要

A volumetric infra-sonic pick-up may be used in various combinations to form an infra-sonic or low-frequency alarm and intrusion detector. The detection device for alarm, surveillance and/or monitoring comprises an infra-sonic pick-up (1) below the sonic frequency range. The infra-sonic pick-up (1) comprises means acting as a pressure or pressure variation pick-up (2), an amplifier (3), and a filter which eliminates the audio or higher frequency signals. The pressure pick-up (2) is a microphone.