Abstract: A vehicle navigation system includes a message transmitter/receiver capable of holding a dialog with a central database under the control of a processor to request and obtain information signals. Messages are received in the form of a cession of reference numbers, and the processor searches its local database for intelligible data corresponding to each reference number. Since the local database contains a limited capacity, for certain reference numbers the corresponding intelligible data will not be in the memory. The processor then begins a dialog by means of the transmitter/receiver, between itself and a central database, so as to obtain the lacking data that corresponds to a received reference number.