Abstract: A tire air pressure monitoring apparatus includes a plurality of transmitters provided in respective tires on a vehicle and a receiver mounted on the body frame of the vehicle. Each transmitter radio-transmits data regarding the internal air pressure of the associated tire. The receiver receives radio-transmitted data from each transmitter. The receiver displays the received data on a display and stores the data in a non-volatile memory. When a request signal from a predetermined external communication apparatus is received, the receiver radio-transmits data stored in the non-volatile memory to the external communication apparatus. This allows various kinds of data such as air pressure data to be easily loaded from the receiver to the external communication apparatus.

Abstract: A tire inflation pressure monitor includes a number of transmitters and a receiver. The transmitters transmit data concerning tire inflation pressure by radio waves, and the receiver receives the data from the transmitters. The receiver includes reception antennas and a synthesizer. The reception antennas respectively induce voltage signals based on the reception of the radio waves from the transmitters, and the synthesizer synthesizes the induced voltage signals into one voltage signal. The synthesizer selects the highest level voltage signal from the induced voltage signals and outputs the voltage signal to a reception circuit. Therefore, the synthesizer permits the reception circuit to receive the voltage signal of a given transmitter without fail.

Abstract: Each transmitter installed in tires on a vehicle generates a variable value, which is updated according to a predetermined sequence every time it sends data. The current value of the variable is transmitted to a receiver regularly along with other the information. The receiver determines whether any receptions have been skipped prior to the current reception based on whether or not the variable value included in the received data has been updated according to the sequence. The receiver judges that there is a communication failure when the number of skipped receptions is equal to or greater than an upper limit value and judges that there is no communication failure when the skipped reception number is less than the upper limit value. This permits easy and reliable detection of communication failures.

Abstract: A vehicle wheel information supply device for supplying wheel information relating to a state of a wheel of a vehicle, including a wheel state detector for detecting the state of the wheel, a wheel information generator for generating the wheel information relating to the state of the wheel, on the basis of an output of the wheel state detector, a transmitter for transmitting the wheel information, and a receiver which receives the wheel information transmitted by the transmitter, the wheel state detector, the wheel information generator and the transmitter being disposed on the wheel while the receiver being disposed on a body of said vehicle, wherein the wheel information generator is capable of selectively generating different kinds of wheel information having respective different volumes, and at least one of the wheel information generator and the transmitter operates in a manner depending upon at least one parameter indicative of the state of the wheel, which at least one parameter is detected by the whe