| 摘要 |
PROBLEM TO BE SOLVED: To effectively protect the communication from external noise on the occasion of executing the communication through the power supply line. SOLUTION: To a side module 21 forming the air-bag system of vehicle, an output voltage of a battery 35 which is pumped with a DC-DC converter 36 connected to the power supply line 30 is supplied through the output line 44 of a constant voltage circuit 40. The output line 44 is used for communication to transmit the signal as a change of current under the control of an output transistor 25 by a microcomputer 22. Change of current is detected by the communication IC 45. In view of reducing the high voltage external noise entering the power supply line 30, a zener diode 37 is inserted. Moreover, the constant voltage circuit 40 reduces the high voltage external noise and the zener diode in the side module 21 protects over-voltage due to the external noise.
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