A vehicle has a detecting section that detects, as a detection value, a rotational angle of each wheel assembly. A transmitter provided in each wheel assembly transmits transmission data when the rotational angle of the wheel assembly is any of specific angles. At the performance of transmission at the specific angle, the transmitter changes data that is different from angular data indicating the rotational angle of the wheel assembly and is included in the transmission data in accordance with the specific angle. A vehicle-mounted receiver collects the detection values detected by the detecting section upon reception of the transmission data. The receiver collects the detection values for each piece of the transmission data transmitted at the same specific angle based on a manner in which data included in the received transmission data is changed in accordance with the specific angle.