HUD short for Head Up Display,the main function is to reflect the car dashboard information (e.g. speed,RPM,water temperature,voltage,trip distance etc),and keep the driver eyes always on road to avoid the dangerous of lowering down head to read the instrument.The working voltage of this product: 11V-18Vdc (12Vdc\/200mA).Please use the USB cable if car voltage 24V.This product is a dual system:Users can freely choose the mode(press the '+ ' key to select OBD or GPS system)before the OBD on screen stop to flash,it will automatically save and enter your last option.1.Light sensor: HUD can automatically adjust the brightness according to the environment2.Speed : OBD mode:speed Car ECU data,GPS mode:satellite data like compass3.System : short press the '+ ' key within 5 seconds to choose OBD or GPS system4. Multi-function area: Speed,water temperature,voltage,mileage,driving time,fuel consumption, altitude,clock,100 kilometers acceleration5. a + =100km acceleration, =altitude, =fuel consumption, MIN=travel time, TRIP=travel mileage6. Water temperature , Voltage 7. Over-speed alarm 8. Driving direction: Driving direction indication:W=West, N=North, S=South, E=East when the vehicle speed 5KM \/ H9. Speed display area10. Speed unit: KM\/H=kilometer\/hour, MPH=Mile\/hour11.Satellite : flashing will stop until satellite numbers been got, please move the car to the open road, the GPS light will stay on if satellite signal been founded.colour:BlackMaterial:plasticPackage Contents:1 x host1 x OBD line1 x USB cable1 x non-slip mat1 x manualOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +\/- 1-3cm.