초록 ▼

The oscillations which are generated during an attempted instrusion at a protected area or surface, for instance a vault wall or fence, are received at a sonic receiver and processed by an evaluation circuit such that only the oscillations emanating from an intrusion attempt trip an alarm, not howev

The oscillations which are generated during an attempted instrusion at a protected area or surface, for instance a vault wall or fence, are received at a sonic receiver and processed by an evaluation circuit such that only the oscillations emanating from an intrusion attempt trip an alarm, not however spurious oscillations from the surroundings. The received oscillations are mixed with a carrier frequency whose frequency periodically and continuously passes through a certain frequency range. The mixed signals are filtered in a narrow band frequency range, so that at the output, during each frequency through pass period, there appears the entire frequency spectrum of the received sonic oscillations in the evaluated frequency range. The filtered signals are integrated and the integrated signal, after a brief period of time, is reset as a frequency throughpass if no further signal appears. This integrated signal reaches an alarm threshold only upon occurrence of irregular oscillations in the evaluated frequency band, not however in the presence of disturbances due to individual periodic oscillations or spurious oscillations outside of the frequency range.

대표청구항 ▼

A method for detecting an intrusion, comprising the steps of: obtaining signals delivered by a sonic receiver mounted at the object to be protected; mixing the obtained signals with a carrier frequency whose frequency periodically and continuously passes within a given time duration through a predet

A method for detecting an intrusion, comprising the steps of: obtaining signals delivered by a sonic receiver mounted at the object to be protected; mixing the obtained signals with a carrier frequency whose frequency periodically and continuously passes within a given time duration through a predetermined frequency range; filtering the mixed signal in a narrow band frequency range; upon occurrence of a filtered signal activating a timing circuit having a predetermined time duration; integrating the filtered signal; resetting the result of the integrated filtered signal whenever the filtered signals are interrupted for at least said time duration of the timing circuit; said time duration at most being equal to the time duration of a frequency throughpass; and triggering an alarm signal as soon as the integrated signal reaches a predetermined threshold within the reset time.