Abstract: The present invention mentions a system that allows a user of the wireless mobile system to have access to the PSTN. Using its mobile device (9) connected to a concentrator (1), through an mobile radio interface, when the user will be located in the neighborhoods of the concentrator, also he allows the mobile terminal (9) to have access the mobile network when the user leaves the area of covering of the mentioned concentrator. The system is composed of a mobile device (9) with capacity of access to the wireless mobile system, a concentrator (1) that it includes an adapting module of wireless access (2), that it is added to the module of access to a fixed network. The submodule of access to the analogical line (11) can be connected to a MUX/DEMUX pair (13). This pair Mux/DEMUX (13) is used to combine the users pertinent to the area of covering of the concentrator in an only analogical line.