Abstract: A distance measuring system includes a device for detecting ringing signals (false echoes) generated by ultrasonic transducers used to generate probe signals and detect echoes of the probe signals to determine the distance of an external object from the measurement system. The absence or duration of ringing signals are determined, and the display of the distance measuring system is operated accordingly. False indications of distance measurements are limited by storing a number of distance measurements in a memory, and selecting the measurement most likely to indicate the presence of an object from which the distance to the measuring system is determined.

Abstract: A vehicular distance measuring system includes a distance measuring device for detecting a distance to an object and, in response, supplying a distance signal. An ultrasonic transducer mounted in a vehicle taillight or running light assembly is used to ultrasonically detect and range objects in back of, and along side a vehicle in which the system is installed. A display includes (i) a vehicular mirror having an image reflecting surface with a transparent window portion located therein, and (ii) a digital display mounted on the vehicular mirror and viewable through the window portion. The digital display is responsive to the distance signal for displaying the detected distance to the object. The distance measuring device includes a comparator for comparing the distance to the object with a predetermined threshold distance and, in response, supplying a display unblank signal.