An automotive information system has a main unit including a CPU and component units connected to the main unit through a universal serial BUS (USB), such as a car audio system including a CD-ROM auto-changer, a security control system, and a telephone system. At least one of the USB-connected component device, e.g., the security control system and/or the telephone system, has a detecting unit that detects occurrence of an event such as illegal approach to the automobile or receipt of telephone call. The USB-connected component device also has a start signal transmitting unit that transmits a start signal to the main unit when occurrence of the event is detected by the detecting unit. The main unit has a start signal receiving unit and a power control unit that serves turn on the power supply to the main unit in response to the start signal received by the start signal receiving unit. The main unit also has an inquiring unit which inquires the USB-connected component devices whether these component devices have sent the start signal. The USB-connected component device has an answering unit which answers the inquiry.