Abstract: An integrated circuit type car audio system can be operated at a general mode or an IC card mode. In the integrated circuit type car audio system, comparator compares a password number stored in the integrated circuit card which is loaded on said system with a reference password number. Mode select section generates a general mode select signal or an integrated circuit card mode signal to select a general mode or an integrated circuit card mode when the stored password number in the integrated circuit card and the reference password number coincide with each other. Controller receives any of the mode select signals selected by the mode select section and generates a mode execute control signal according to the one mode signal selected, and discriminates whether the integrated circuit card is a corresponding card for performing functions of the system based on the comparison result of the comparator.