Velleman ultrasonic distance detector kit velleman k3502 the velleman parking radar kit can help you manoeuvre your car into the tightest space using ultrasonic sound waves whose frequency is beyond the range of human hearing this kit means you can measure the distance between your car and nearby obstacles for example a sensor mounted on the back of the car can give an indication of the distance between your car and the one parked behind you at the same height as the sensor when the pr