... : 380pcs Digital Display Handle Functions: 1, ON /OFF: Press main Knob for 2 seconds, can turn on /off the trolley.2 ... , When you the trolley is on, turn the main Knob in clockwise, the trolley would go forward, keep turning clockwise ... , set the distance(between 1-30M) by adjusting the main knob, the main display would shows the distance you set. Then ...