| 摘要 |
PURPOSE:To enable tunnel detection to be performed without malfunction even under all weathers with a simple constitution by detecting the reflection of the ultrasonic waves from two oscillators equipped on a moving object by leaving a specified spacing and taking their logical product. CONSTITUTION:Ultraonic waves from an ultrasonic wave oscillator 5a are amplified and are sent out from a sounding body 2a. When a moving object 1 is within a tunnel, the waves are reflected by the ceiling, etc. of the tunnel and are collected by a sound collector 4a, from where they are inputted to an ultrasonic microphone 3a. The ultrasonic waves then pass through a band-pass filter 7a and are thereby detected. The ultrasonic waves from the other one set of ultraonic wave oscillator 5b are similarly reflected in the tunnel and are detected. The oscillation frequencies of the ultrasonic wave oscillators 5a and 5b are set at mutually different frequencies. The ultrasonic waves having been detected in both of the receiving amplifiers 8a and 8b in the tunnel are put in an AND circuit 9 and the logical product of detection is taken, whereby the tunnel detection is accomplished. |
