| 摘要 |
<p>PROBLEM TO BE SOLVED: To detect approach of a mobile even at an intersection of low visibility by transmitting a sound wave of specified frequency and receiving a sound wave reflected on an object to be detected. SOLUTION: A sine wave electric signal of specified frequency outputted from an oscillation means 1 is amplified through a sound wave transmission amplifier 2 to transmit a sound wave of specified frequency from a sound wave transmission member 3, e.g. a speaker. The sound wave propagates around an obstacle and reflected on an object to be detected, i.e., a mobile, and the reflected sound is received by a sound wave receiving member 4, e.g. a microphone. When the mobile approaches (gets away), frequency of the sound wave increases (decreases). Received sound wave is converted 4 into an electric signal and a BPF 5 attenuates the components deviating from a specified frequency region before the electric signal is delivered to a sound wave receiving amplifier 6. Frequency of amplified 6 electric signal is measured by a frequency measuring means 7 and when continuous input of sound wave of specified frequency is determined, a specified signal is delivered to an alarm 8 which alarms 8 detection of mobile to a driver.</p> |
