A method and a mobile station, in which the CPU memory of the mobile station provides interfaces for a plurality of applications that are external to the mobile station. Applications program modules for the external applications are stored in that part of the CPU memory of a mobile station which is available after that the software than controls the conventional functions of the mobile station has been stored. The CPU of the mobile station thereafter performs the functions that connect external devices to the radio part of the mobile station and in this way replaces a conventional external CPU as interface between external devices and the mobile station.