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.

Abstract: A receiver, adapted to the reception of identification data in accordance with the RADIO DATA system (RDS) and having only one tuner, effects the acquisition of the identification code of an alternative channel by sampling the alternative channel during periods in which the audio output of the receiver is muted. These periods are of such a short duration that they are not noticed by the listener.

Abstract: Device for receiving and processing road information messages transmitted in digital form, each message including at least a first section for indicating the zone of the road network to which the message refers, which device includes for the control of the data processing a data processing unit which is connected to a bus for the transfer of data, to which bus are also connected a reception memory for temporarily storing the received messages, a selection unit enabling the selection from among the stored messages of those concerning a zone to be designated and a presentation unit for presenting the selected messages.