The invention relates to a control and processing unit for a touch-sensitive screen and comprises a communication unit and a memory. The control and processing unit is configured for receiving first sensor data which is generated by way of capacitive sensors of the touch-sensitive screen, for receiving second sensor data which is transferred from an input unit to the control and processing unit, wherein the second sensor data comprises data of a sensor of the input unit, said sensor being designed to detect a putting-down of the input unit, and for examining, on the basis of a temporal sequence of the first and second sensor data, whether a putting-down of the input unit has been detected simultaneously with the placing of an object with a conductive structure onto the touch-sensitive screen, in order to ascertain whether the input unit has been put down on the touch-sensitive screen. The invention further relates to a system with such a control and processing unit, as well as to a method for use.