an automobile equipped with the vehicular portion of a traffic information and guidance system utilizing exchange of data between vehicles and the rest of the system through inductive coupling with loops set at various places in roadways , is provided with two - way telephone communication possibilities at places where roadway loops are provided where a car can stop for making a telephone call , as for example in a parking space . only small amounts of equipment need to be added to the vehicle and to the fixed installations to permit telephone communication between the vehicle and telephones in a public network . separate receivers and transmitters for speech communication operated with amplitude or frequency modulation can be switched in , or else the speech signals can be converted into pulse code modulation and simply supplied through input / output units to the data transmitter / receiver of the traffic information system . the telephone calling features are enabled only when the travel path measuring device of the traffic information system is at rest , but the vehicle can be reached while in motion by a paging system to ask the driver to stop at the next telephone communication location .