| 摘要 |
PROBLEM TO BE SOLVED: To unnecessitate useless search and to reduce the power consumption as well, by constituting a transmitter carried by a person to be searched so as to start action when passing through the entrance/exit of residential block, namely, at the moment when that person strays outdoors. SOLUTION: A high frequency current from an oscillator 2 is always let flow through a loop antenna 1 extended around the entrance/exist of house. When a person 3 to be searched carrying a transmitter 4 with him passes the loop antenna 1, concerning the transmitter 4, a built-in coil is activated by sensing the line of magnetic force generated by the loop antenna 1 and radiates radio waves. An antenna 5, which enables azimuth measurement, is installed on the roof of residential house of the person 3 to be searched, etc. A signal processor 6 measures the coming direction and reception level of radio waves by amplifying the radio waves received from the transmitter 4 by the antenna 5 and displays the measured values at the positions of LED string on a display 7. At the time point when the person 3 to be searched gets out of the house and the turning-on position of LED string is moved from inside to center, an alarm is issued. |
