| 摘要 |
PURPOSE:To make a titled method convenient for detecting obstructions during retreating of an automobile or the like by producing continuous sounds when the distance from an ultrasonic transmitter and receiver up to the obstruction is within a specified value, changing the same to intermittent sounds when the distance exceeds the specified value and changing the periods of the intermittent sounds according to distances. CONSTITUTION:An ultrasonic wave transmitter and receiver 1 drives a transmitter 4 to generate ultrasonic waves. The ultrasonic waves are reflected by an obstruction 3 and are received in a receiver 5. The received output is applied to an ultrasonic wave receiver 2, which converts the same to the quantity of electricity corresponding to the distance up to the obstruction 3. The output of the receiver 2 is supplied to an oscillating circuit 13 and a comparator 14, both outputs whereof are fed through an AND circuit 15 and an amplifier 16 to operate a sounding body 17. Thus when the distance up to the obstruction is within a specified value, the sounds are continuous and when the distance exceeds the specified value, the sounds change to intermittent sounds. The periods of the intermittent sounds can be varied according to distances. It is also possible to change the timbres of the intermittent sounds or to display distances by lighting and flickering a lamp and changing the periods of the flickering. |
