1. Specially designed voice speaker can via human voice to notify driver the nearest distance of the obstacle. 2. LCD display can show the diatance of the obatacle according to each sensor synchronized, make it more safer when park a car 3. The quantity of sensors can be 4, 6, 8 each quantity can be matched at random 4. 3 alarming mode: Whisht sound, alarm sound and human voice, all sounds can setup at random according to one's interest 5. LCD display can close at random when no-backing a car, which will not shelter one's sight, make it more safer to drive. 6. Display precision can be adjusted within 2cm or 5 cm 7. Round-the-clock design to adapt to different environment 8. Sensors have perfect colours to meet different colours and models of cars 9. Warranty: 3 years