| 摘要 |
PROBLEM TO BE SOLVED: To provide an antitheft system which can perform precise detection with small misrecognition of disturbance noise, resembling an alarm sound, due to BGM, noise, etc., in a store or an echo of the alarm sound depending upon the state of the individual store. SOLUTION: The antitheft system has an alarm unit which is coupled with an object of theft prevention and intermittently generate an alarm sound of fixed frequency against an illegal action and an alarm sound detecting device which detects the alarm sound of the alarm unit and generates an alarm signal. The alarm sound detecting device has a 1st decision means and a 2nd decision means which decide an input signal including the alarm sound of the alarm unit and a disturbance sound; and the 1st decision means decides a random disturbance sound included in the input signal and the 2nd decision means decides a reflected sound due to an echo of the alarm sound and generates the alarm signal.
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