The invention provides a circuit that can observe data within shift registers without altering the data. The valve can be mounted flush on the exterior surface of the rim or in a recessed position within the rim, and can be connected to a manifold that is able to control the flow of pressurized fluid from the central tire inflation system to each valve and tire connected to the valve. Further, the control of a concentration ratio can be performed stably by detecting the concentration of oxygen. A coil spring is disposed about the rod, with the rod extending through a central aperture thereof.