Abstract: Device to deliver an alarm signal upon detection of a gravitational wave generated by a body falling into a swimming pool, using a differential detector that includes a comparison device for comparing a sensitivity threshold value to the value of the electrical signal received, and to deliver an alarm signal when the received electrical signal exceeds the sensitivity threshold value. The electrical signal resulting from the detected waves is delivered to a comparator and allows a programmed microprocessor to deliver variable-width pulses to the input of the comparator so as to reduce the sensitivity of the device when the device detects an atmospheric disturbance. The microprocessor triggers the alarm when the width of the output pulses from the comparator is larger than a predetermined critical reference and when the frequency F of the analogue electrical signal lies between two predetermined values F1 and F2.

Abstract: Device to deliver an alarm signal upon detection of a gravitational wave generated by a body falling into a swimming pool, using a differential detector that includes a comparison device for comparing a sensitivity threshold value to the value of the electrical signal received, and to deliver an alarm signal when the received electrical signal exceeds the sensitivity threshold value. The electrical signal resulting from the detected waves is delivered to a comparator and allows a programmed microprocessor to deliver variable-width pulses to the input of the comparator so as to reduce the sensitivity of the device when the device detects an atmospheric disturbance. The microprocessor triggers the alarm when the width of the output pulses from the comparator is larger than a predetermined critical reference and when the frequency F of the analogue electrical signal lies between two predetermined values F1 and F2.

Abstract: The invention concerns an alarm device including an acoustic pressure sensor (10) delivering an analog signal to first amplifying means (12) and to second amplifying means (14), a first comparator (34) whereof the + input is connected to the output of the second amplifying means and whereof the output delivers a warning signal to alarm means (26, 28) when there is a break-in or an attempt at breaking in, and self-adjusting means consisting of a microprocessor (26) programmed to deliver a digital signal at the −input of said first comparator whereof the pulses have a variable width which increases in accordance with the duration and the importance of said atmospheric disturbance so as to automatically increase the alarm device triggering threshold and hence reduce its sensitivity when the acoustic sensor detects an atmospheric disturbance such as wind.

Abstract: An improved acoustic burglar alarm detects an aperiodic wave resulting from opening of a door or window, and adapts the threshold level, which discriminates between alarm events and non-alarm events, according to the ambient environment, thereby preventing wind from setting off an alarm, yet maintaining adequate sensitivity. The detection system features a microphone 1, preferably of electret type, a threshold comparator 5, a filtering circuit 7, a window comparator acting as a peak value detector, an integrator circuit 9, a voltage monitor 10, and an oscillator-counter 14. A monostable 16 triggers a relay 21 which sets off the alarm. A switch 15 permits selection between two alternate operating modes.