Click and drag answers to change the order, or select using ↹ Tab then move by pressing Space and the ↑ ↓ arrows on your keyboard.
sends signals to a timer when a passing object cuts its infrared beam
sends out sound pulses and the reflections from an object are detected
uses changes in frequency of reflected waves to measure speed
takes photos of road vehicles a short time apart
To pick up a draggable item, press the space bar.
While dragging, use the arrow keys to move the item.
Press space again to drop the item in its new position, or press escape to cancel.