ELECTRONIC DEVICE

PROBLEM TO BE SOLVED: To prevent input connection of a disturbing signal to a conductor between a switch element and a seatbelt fastening device so as to dispense with a high performance switch element by connecting the switch element with an ignition element in parallel. SOLUTION: An ignition element is constructed of a resistor 10 and a capacitor 11 connected in series, and a switch element 13 is connected to the ignition element in parallel, while another resistor 12 is connected to the switch element 13 in series. A resistor 16 connected to the switch element 13 in parallel is used for recognition of disconnection. As the switch element 13 is normally closed, a current circuit informs that a seatbelt is not inserted into a buckle for recognition of a seatbelt operating state. When a seat belt is mounted, the current circuit is cut off. In this way, symmetric wiring protective against input connection of an electromagnetic disturbance can be accomplished. As ignition current for ignition elements 10, 11 is not needed to flow via the switch element 13, a low-cost switch element 13 for low current can be used.