TRANSMITTER, TRIGGER DEVICE, ID CODE REGISTRATION SYSTEM, AND ID CODE REGISTRATION METHOD

A transmitter is coupled to each of a plurality of wheel assemblies included in a vehicle. The transmitter is configured to function in one of a plurality of formats that are selectable by a command from a trigger device. The transmitter includes a pressure sensor configured to detect the tire pressure, a memory that stores an ID code, a transmission unit configured to transmit a signal, a controller configured to control the transmitter, and a trigger reception unit configured to receive a trigger signal including the command from the trigger device. The controller is configured so that when the trigger reception unit receives a trigger signal including a command designating a format of the transmitter, the controller has the transmitter function in the designated format and has the transmission unit transmit the signal including the ID code to register the ID code to an in-vehicle receiver.