| 摘要 |
PURPOSE:To improve the ability for detecting a near object by detecting the existence of the object by the use of an object detecting means from the rise after transmitting an ultrasonic wave pulse of waveform shaping means output. CONSTITUTION:The output of a level detecting circuit 9 obtains that of a differentiating circuit 10. A negative pulse indicating the fall of the output of the level detecting circuit 9 is removed by depriving the logical sum of the output of the differentiating circuit 10 by the use of an OR circuit 11 and the output based on the positive pulse indicating the rise of the output of the level detecting circuit 9 is obtained. But, since the rise output at the time of wave transmitting start of an ultrasonic pulse wave is produced in the output of the OR circuit 11, the gate signal which reverses a wave transmitting signal from a wave transmitting signal production circuit 2 is input in a detecting circuit 8, and the output of the OR circuit 11 is not received in the detecting circuit 8 while the gate signal is in the low level. Therefore, the existence of an object can be detected by detecting the rise after transmitting the ultrasonic pulse wave of the output of the level detecting circuit 9.
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