A radio system is installed in a building, wherein each terminal (T) communicates with neighbouring terminals and can transmit telegrams. The terminals (T) are contained in devices or installed as separate mobile terminals. A routing table is created, in which each acceptable route from a source (Q) to a destination (Z) is entered. Connection from source to destination is evaluated with consideration of the number of hops from terminal to terminal within a route, and of the availability of unique individual sections (SES) that cannot be replaced by a parallel path.