Abstract: A receiver receives frames transmitted by transmitters respectively attached to wheel assemblies. Each transmitter transmits three or more frames successively at different transmission intervals when a rotation angle of the associated wheel assembly agrees with a specific angle. When receiving the frames, the receiver determines the transmission ordinal numbers of the received ones of the frames from a previously stored correspondence relationship between an order of transmission and transmission intervals of the frames. The receiver derives, from the determined order of transmission of the frames, a specific point in time that is within specified time from the detection of the specific angle. Based on the rotation angle of the wheel obtained by a rotation angle detecting unit at the specific point in time, the receiver identifies the wheel assembly to which each of the transmitters is attached.

Abstract: A transmitter includes a power source of the transmitter, a condition detecting section that detects a condition of a tire, a data generating section that generates transmission data that contains tire condition data indicating the condition of the tire detected by the condition detecting section, a transmitting section that modulates the transmission data and transmits the modulated data, a storage section storing a correspondence relationship in which values of a specific bit among bits of the transmission data that change as the wheel assembly rotates are respectively assigned to specific angles set for the rotation angle of the wheel assembly, and a transmission control section that transmits the transmission data from the transmitting section when detecting that the rotation angle of the wheel assembly is any of the specific angles.

Abstract: A reception control section obtains the rotation angles of wheel assemblies when receiving transmission data by a reception circuit. The reception control section divides 360°, which is the range of the possible rotation angles of the wheel assembly, into equal parts to obtain angle ranges and assigns each of the obtained rotation angles to one of angle ranges. The reception control section derives the angle range in which the number of times (frequency) the obtained rotation angles are included is a maximum value. The reception control section calculates a reception-side angle difference, which is the difference between the median values of the angle ranges in which the number of times the obtained rotation angle is included is a maximum value. The reception control section associates the ID codes with the wheel assemblies based on the correspondence between the reception-side angle difference and the angle difference between specific angles.

Abstract: An acceleration detecting device includes a power source, an acceleration sensor, an acquiring section, a rotation period calculating section, and an acquisition period setting section. The acceleration sensor is configured to detect a centrifugal acceleration generated by rotation of a wheel assembly. The acquiring section is configured to acquire a detection value from the acceleration sensor with a predetermined acquisition period, thereby acquiring the detection value from the acceleration sensor each time the wheel assembly rotates a constant angle. The rotation period calculating section is configured to calculate a rotation period of the wheel assembly. The acquisition period setting section sets the acquisition period. The acquisition period setting section is configured to increase a number of times the detection value is acquired from the acceleration sensor per rotation of the wheel assembly as the rotation period calculated by the rotation period calculating section becomes longer.

Abstract: A transmitter includes a power source of the transmitter, a condition detecting section that detects a condition of a tire, a data generating section that generates transmission data that contains tire condition data indicating the condition of the tire detected by the condition detecting section, a transmitting section that modulates the transmission data and transmits the modulated data, a storage section storing a correspondence relationship in which values of a specific bit among bits of the transmission data that change as the wheel assembly rotates are respectively assigned to specific angles set for the rotation angle of the wheel assembly, and a transmission control section that transmits the transmission data from the transmitting section when detecting that the rotation angle of the wheel assembly is any of the specific angles.

Abstract: A reception control section obtains the rotation angles of wheel assemblies when receiving transmission data by a reception circuit. The reception control section divides 360°, which is the range of the possible rotation angles of the wheel assembly, into equal parts to obtain angle ranges and assigns each of the obtained rotation angles to one of angle ranges. The reception control section derives the angle range in which the number of times (frequency) the obtained rotation angles are included is a maximum value. The reception control section calculates a reception-side angle difference, which is the difference between the median values of the angle ranges in which the number of times the obtained rotation angle is included is a maximum value. The reception control section associates the ID codes with the wheel assemblies based on the correspondence between the reception-side angle difference and the angle difference between specific angles.

Abstract: An acceleration detecting device includes a power source, an acceleration sensor, an acquiring section, a rotation period calculating section, and an acquisition period setting section. The acceleration sensor is configured to detect a centrifugal acceleration generated by rotation of a wheel assembly. The acquiring section is configured to acquire a detection value from the acceleration sensor with a predetermined acquisition period, thereby acquiring the detection value from the acceleration sensor each time the wheel assembly rotates a constant angle. The rotation period calculating section is configured to calculate a rotation period of the wheel assembly. The acquisition period setting section sets the acquisition period. The acquisition period setting section is configured to increase a number of times the detection value is acquired from the acceleration sensor per rotation of the wheel assembly as the rotation period calculated by the rotation period calculating section becomes longer.

Abstract: A reception control section obtains a rotation angle of each wheel assembly when a reception circuit receives transmission data. The reception control section calculates the absolute value of the difference between the obtained rotation angle and a previously obtained rotation angle. The reception control section determines whether the absolute value of the difference is included in a reference range or a specific range. The reference range includes 0. The specific range includes the angle difference between specific angles.

Abstract: A reception control section obtains a rotation angle of each wheel assembly when a reception circuit receives transmission data. The reception control section calculates the absolute value of the difference between the obtained rotation angle and a previously obtained rotation angle. The reception control section determines whether the absolute value of the difference is included in a reference range or a specific range. The reference range includes 0. The specific range includes the angle difference between specific angles.

Abstract: A tire condition detection device includes a condition detecting section, a control section, a transmitting section, a receiving section, and battery, which is a power source for the tire condition detection device. When the receiving section continually receives information from an external device, a controller switches the state of the tire condition detection device from a responsive state to a non-responsive state. In the responsive state, the receiving section is maintained in a standby state, in which the receiving section is capable of receiving the information wirelessly transmitted from the external device, and a reception response is performed when the information is received. In the non-responsive state, the reception response by the receiving section is not performed regardless whether the receiving section is maintained in the standby state.