| 摘要 |
PURPOSE:To reduce malfunction and to improve detection precision by stopping the output of a receiving circuit when the time width of a received signal is longer than set time. CONSTITUTION:A transmitting circuit 2 consists of an integration circuit 7, monostable multivibrator 8, oscillating circuit 9, and amplifying circuit 10, and transmits an ultrasonic wave of frequency equal to the oscillation frequency of the oscillating circuit 9 from a transmitting oscillator 1. A receiving circuit 4 consists of an amplifier 11, turning and amplifying circuit 12, detecting circuit 13, gate circuit 14, comparator 15, switching circuit 16, and time comparing circuit 6. The time comparing circuit 6 compares the time width of an output with set time and then inhibits the output of the receiving circuit 4 from being supplied to the switching circuit 16 when the time width of the output is longer than the set time width. |
