an infrared sensor or a plurality of these sensors adapted to determine a position of an object in an environment of the touch screen 101 fig2 shows a perspective view of the mobile device 100 and a finger 200 of a user operating the mobile device 100 on the touch screen 101 a plurality of information element fields 201 205 is displayed the information fields 201 205 displayed on the touch screen 101 may comprise for example icons of applications or virtual operating elements like push buttons sliders and so on for example upon touching one of the information fields 201 205 a corresponding application may be started or an acoustic optic or haptic response may be output to the user operation of the mobile device 100 shown in fig1 and 2 will be described in more detail in the following in connection with fig3 in step 301 the processing unit 102 determines a position of the finger 200 by using the proximity sensor 103 the processing unit 102 may track the position or a change of position of the finger 200 to determine a moving direction 206 and a speed of the finger 200 preferably based on a sequence of position information determined using the proximity sensor 103 the moving direction 206 of the finger 200 approaching the touch sensitive surface 104 may be determined.