| 摘要 |
PURPOSE:To eliminate malfunction due to interference from the adjacent ultrasonic switch by controlling the second ultrasonic switch transmitter by close-signal of gate circuit that restricts the first ultrasonic switch detection area, in case both ultrasnoic switches are located in the same sound field of reflection type US. CONSTITUTION:There are transmitter 1 that emits ultrasonic wave pulse by application of output from oscillator 2, and receiver 4 that receives reflected wave of emitted ultrasonic wave from the object to be detected 13. Output from the receiver 4 is supplied to detector D via gate circuit 6 that opens for a given period of time t2 after ultrasonic wave is emitted. The gate circuit 6 of the adjacent ultrasonic switch A in the same sound field emits close-signal, which, detected by differentiator 7, triggers univibrator 3 that controls the transmitter 1 of ultrasonic switch B. This causes ultrasonic switch B to be operated after completion of detecting operation of ultrasonic switch A. Therefore, if two or more ultrasonic switches are adjacently located, one ultrasonic switch receives reflected ultrasonic wave from another ultrasonic switch, so that no malfunction occurs. |
