| 摘要 |
PURPOSE:To easily detect a lost child exiting from a specified area by allowing a receiver to receive and identify radio waves sent out of plural transmitters, classifying the signals every time an output level varies, and displaying and storing them. CONSTITUTION:A transmitter 1 consists of a crystal oscillator 6 which has an electrode installed in a crystal vibrator and oscillates at a predetermined frequency, a modulating circuit 3 which modulates the oscillation frequency of the transmitter 6 by a control part 4, and an antenna 2. The receiver 8, on the other hand, has an antenna 7 which receives the radio wave from the transmitter 1, a demodulating circuit 9 which demodulates the received signal, and a radio wave shaping circuit 10. A frequency matching circuit 14 extracts a component of frequency in the signal which is waveform-shaped by the circuit 10 and matches it with the stored frequency in a read-only memory 15 which is stored previously with the frequency. Further, the control part 16 inputs information from the circuit 14 and performs specific arithmetic to output a control signal to respective parts. Consequently, plural objects are identified at a time to easily detect the lost child, etc., exiting from the specified area.
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