Tire condition monitoring apparatus

A commander (6) transmits a command signal that includes a channel code set by a channel code setting switch (11). When receiving the transmission command signal from the commander (6), a transmitter (3) transmits a response signal that contains the channel code contained in the command signal and a unique ID code of the transmitter (3). When receiving the response signal from the transmitter (3), a receiver (5) stores the ID code contained in the response signal in the memory (34) if the channel code contained in the response signal is related to a channel code set by a channel code setting switch (30). As a result, the ID codes of the transmitter (3) is correctly registered in the receiver (5).