| 摘要 |
<p>PROBLEM TO BE SOLVED: To detect intrusion of an intruder into a specific space. SOLUTION: At least two from among acoustic or electromagnetic signals with different frequencies (f1, f2,..., fn) are emitted in a space by a transmitter 20, and a signal which is the combination of signals emitted and reflected in the space is received at a certain point in space by a receiver 22, and the characteristics of the decoded signals with the different frequencies are compared so that whether any intruder is present can be judged. When it is confirmed that an intruder is present, an intrusion signal is generated.</p> |
