| 摘要 |
PURPOSE:To detect an object as obstacle or the like accurately with a simple construction, by providing a plurality of sensors with a directivity to bring a directivity to the detection of the object utilizing the difference in the detection sensitivity of the object between the sensors. CONSTITUTION:When AC signals of a fixed frequency are applied in series to networks 21 and 22 from an oscillator 4, a high frequency output voltage is fed to a bandpass amplifier 5 according to the product of attenuations of the AC signals respectively proportional to the access of the object to the sensors 11 and 12 facing it. With the amplifier, noises induced in the sensors 11 and 12 are removed and hence, the high frequency component alone of a specified frequency is amplified. The resulting frequency signal is detected with a detector 6 to be fed to a voltage variations detecting circuit 7, which provides an alarm command to a driver 8 when the voltage drop of the DC voltage signal given falls below the preset reference. |
