An auxiliary back-up and trailer coupling device for motor vehicles includes ultrasonic sensors mounted on the motor vehicle. The ultrasonic sensors transmit and receive sound waves, and are linked to a control and display device. The device permits the position of a trailer unit that is equipped with...http://www.google.es/patents/US5455557?utm_source=gb-gplus-sharePatente US5455557 - Auxiliary back-up and trailer coupling device for motor vehicles
Auxiliary back-up and trailer coupling device for motor vehicles
