Each acceleration sensor of an air bag system includes a sensing device, a
communication device and an adjusting device. The sensing device
generates a measurement signal, which indicates a measurement value of
acceleration. The communication device performs two-way communication
relative to a master ECU and each remaining one of the acceleration
sensors of the air bag system. The adjusting device adjusts the
measurement value based on a physical quantity application state of its
own acceleration sensor and a physical quantity application state of each
remaining one of the acceleration sensors.