Patent ID: 7170416

Claim:
A device intended to deliver an alarm signal upon detection of a gravitational wave generated by a body falling into a swimming pool, which comprises a means of sensing aquatic waves that is placed beneath the surface of the water of the swimming pool, a means of converting the aquatic waves sensed by said sensing means into an analogue electrical signal (S 1 ), and a differential detector that includes comparison means for comparing a sensitivity threshold value of said differential detector with the value of said analogue electrical signal and to deliver said alarm signal when said analogue electrical signal exceeds said sensitivity threshold value, said differential detector comprising autoregulation means which includes an analogue/digital converter that receives a preamplified analogue electrical signal as input and delivers a digital signal (S 2 ) as output when a disturbance in the water occurs, a comparator, the positive (+) input of which receives said preamplified analogue electrical signal, and a microprocessor programmed to deliver, in response to the detection of said digital signal delivered by said converter, a digital signal (S 3 ) to the negative (−) input of said comparator, the output pulses (S 4 ) of which have a variable width, which increases with the duration and with the magnitude of said disturbance so as to automatically increase the threshold for tripping an alarm means and therefore to reduce the sensitivity of the device when said sensing means detects an atmospheric disturbance; wherein said device microprocessor triggers said alarm means when the width (TS 4 ) of the output pulses (S 4 ) from said comparator is larger than a predetermined critical reference (REF) and wherein the frequency F of said analogue electrical signal lies between two predetermined values F 1 and F 2 .