ultrasonic motion detector

ultrasonic motion detector

A motion detector employing sound waves having a frequency usually above 20,000 Hz.
References in periodicals archive ?
In the video, the speed of the cart is determined with an ultrasonic motion detector, and displayed as a real-time speed/velocity graph.
For those who need extra protection,many home-security systems are available, from simple alarm units, triggered by infrared or ultrasonic motion detectors, to elaborate central-station command systems that activate sirens or telephone for help in response to "entry" signals.