PURPOSE: To eliminate a flicker of the discrimination display of a receiving and transmitting means which indicates the minimum time of the reception and transmission of a measured wave when a vehicle approaches an obstacle oppositely by displaying even a measured wave receiving and transmtitting means which indicates a time within a specific range for the minimum time together with the measured wave receiving and transmitting means which indicates the minimum time.
CONSTITUTION: A receiving and transmitting circuit 2 sends an exciting signal to ultrasonic transmitter and receivers 1AW1D provided to the rear bumper of the vehicle at proper intervals to transmit ultrasonic waves, and also receives reflected received signals to output a signal 2a whose pulse length is proportional to the time required from the transmission of the ultrasonic wave to the reception. The arithmetic circuit 3 consisting of an input interface 31, a microcomputer 32, and an output interface 33 inputs the signal 2a successively to detect the minimum time and also calculate and display the distance to the obstacle on a display device 4. Further, the circuit 3 displays one of the transmitter and receivers 1AW1D which indicates the minimum time and transmitter and receivers which indicate time within the specific range for the minimum time on the display device 4.
KODERA MASAO
MIKAMI SHIGENOBU
