Device for restricting or controlling and regulating the movement of remote-controlled parts, more particularly parts of a vehicle bodywork as well as a process for operating the device. The device and process can be used with particular advantage as a collision protection for window winders, sunroofs, doors or flaps, more particularly in connection with electrical displacement devices for motor vehicles. The device is characterized by an actuator and a sensor which are mounted on a cohesive uninterrupted transmission path which is a constituent part of the closing surface area of the remote-controlled part and/or of the fixed part interacting therewith. The arrangement is selected so that a part of the energy supplied by actuator is converted into acoustic surface waves which can scatter over the transmission path and can be received by the sensor.