The general field of the invention is that of systems having a capacitive touch screen. The system according to the invention has a portable capacitive device that is intended, in operational mode, to be carried by a user. The touch screen operates at at least one first frequency. The system operates according to at least one first identification mode in which the portable device has transmission means for transmitting a first periodic analogue signal that is transmitted at a second frequency, referred to as “identification” frequency, that is different from the first frequency, said frequency being in a range of frequencies that are transmitted by the human body, said first signal being unique and associated with the user. The portable touch screen has first means for detecting and identifying said first signal and second means for authorizing or denying access to predetermined applications of the touch screen, which are dependent on the identification of the user. Other modes of operation of the system are possible.