Transmitter in tire condition monitoring apparatus

A transmitter has a valve stem (10), an electronic element, a casing and a coupler. The valve stem (10) permits flow of air into the tire. The electronic element transmits a data representing the condition of the tire. The casing (40) accommodates the electronic element. The coupler couples the valve stem to the casing such that an angle of the casing (40) relative to the valve stem (10) is adjustable be controlled. This can be attached to wheels having different cross-sectional shape.