The measurement precision of a current detector of the fuel cell in a fuel cell system is improved. According to one aspect, if an optical transmitter for an individual remote terminal is active for a first prescribed time interval when it has not been enabled for such transmission, the optical transmitter is disabled. This configuration enables only the air bag control unit side to make a collision decision without making a collision decision in the satellite sensor unit side, which allows a simple and low-cost system. The outer race includes and inner bearing surface. A characteristic of the rod-like member is that it comprises a tapered portion formed in the external wall of the rod-like member, the tapered portion having the vertex of its taper facing towards the threaded portion and a taper angle, measured relative to the longitudinal axis, that is within a range variable between 2\xb0 and 6\xb0.