Transmitter for tire monitoring apparatus

The transmitter (30) has a transmission circuit generating a signal containing data that represents a measured air pressure. A magnetic ring (72) magnetizes magnetic pieces (62a, 62b), where the position of the ring relative to the pieces is changed. A magnetic resistance sensor (33) detects a magnetized state of the pieces. The signal contains data based on the detected magnetized state in addition to a tire condition data. An independent claim is also included for a tire condition monitoring apparatus comprising the transmitter.