Ultrasonic surveillance system for the interior of a motor vehicle

The system comprises an ultrasound transmitter and an ultrasound receiver that are attached to an interior space of a motor vehicle, for contactless monitoring of the interior space. The transmitter and the receiver are operable at a fixed pulse repetition rate in a pulse-echo operating mode and a doppler operating mode, and are configured to detect a position, a movement speed and/or a movement direction of a hand of a vehicle occupant such that the lamps (29a,29b) of the vehicle are actuated in the operating modes.