JPS6483177A - Ultrasonic warning device - Google Patents

Abstract

PURPOSE:To obtain a highly reliable warning device against disturbance and the like from the outside by judging abnormality from the change of a received wave signal directly input into a receiver through detouring from a transmitter. CONSTITUTION:A transmitter 1 transmits an ultrasonic wave P of fixed frequency in a warning area and a receiver 2 receives a reflected wave from the warning area. An object detection means 3 detects a moving object on the basis of a Doppler component contained in a received wave signal received by the receiver 2. An abnormality judgement means 4 pulsatorily transmitts an ultrasonic wave from the transmitter 1 and judges outer abnormality of a warning device on the basis of a received wave signal obtained by receiving a detouring wave of an ultrasonic wave by the receiver 2. Further, a switching means 5 is changed over the connection of the detection means 3, the judgement means 4, the transmitter 1, and the receiver 2, and an object detecting mode and an abnormality judging mode are selected. In other words, the abnormality in the circumference to the warning device can be judged by monitoring whether the amplitude level of a detouring received wave signal is higher than a set point, and whether the length of a detouring received wave signal is within a set time.