Patent attributes
A pressure detection sensor for detecting a tire internal air pressure and a wheel side communication device for transmitting a detection result of the pressure detection sensor using a preset transmission mode are provided on each wheel. The detection result from the pressure detection sensor is transmitted to an ECU via a vehicle body side communication device provided on a vehicle body. The ECU is able to notify a transmission mode determination device provided on each wheel that adjustment of the tire internal air pressure is being performed by manipulating a state of the tire internal air pressure. The transmission mode determination device determines a transmission mode to be used by the wheel side communication device such that a transmission frequency of a notification related to the occurrence of an abnormality of the wheel is reduced while adjustment of the tire internal air pressure is being performed.