To identify a wheel position without use of a trigger machine, nor with the measurement of reception intensity and reception number required.
When detecting a wheel position, switching is made between a first mode which employs a reception sensitivity (first sensitivity) that can receive all frames transmitted from a transmitter attached to four wheels and a second mode which employs a reception sensitivity, and can receive only a frame that is transmitted from a transmitter attached to two wheels. With this configuration, it is determined that a frame that has been transmitted from a transmitter is attached whether to a left wheel or to a right wheel, based on the rotational direction information stored in the frames of four wheels received during the first mode. Further, it is determined that a frame that has been transmitted from a transmitter is attached whether to a front wheel or to a rear wheel, based on reception acceptance/rejection during the second mode. Thus, each of transmitters of all four wheels can be determined, and each transmitter is determined to be attached to which wheel.
WATABE NOBUYA
SEKIZAWA TAKATOSHI
