| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a technique capable of accurately determining whether or not there is theft, while avoiding the influence of disturbance. <P>SOLUTION: When a sound sensor 102 detects a sound at which an output exceeding a warning reference voltage serving as a predetermined threshold is available, the output of a comparator C1 (107) becomes high. Then the delayed output of a low-pass filter 105 obtained from a phase shifting circuit 110 is compared with a predetermined reference value. In this way, the rising state of a detection signal is detected retroactively. Based on the result of the detection, a determination is made as to whether or not the sound is caused by impact due to theft. The warning reference voltage can thus be set high and the influence of disturbance can be excluded. <P>COPYRIGHT: (C)2006,JPO&NCIPI</p> |
