A photo expansion gas detector includes a radiation emitter, a sample gas, an expansion gas hermetically sealed in a chamber, and a capacitive diaphragm for sensing pressure changes. In the present invention, a power system includes at least one hydraulic cylinder that defines a first fluid volume and a second fluid volume separated from one another via a moveable plunger. The splitting circuit receives the local oscillation and produces multiple copies of the local oscillation. A storage container mounted on the trailer includes bottom support skids at each end that seat in the cross channels and are secured in the channels by casters that are attached to the skids through mounting holes in the cross channels. In the method, whether a communication environment between a base station and the relay device changes is determined so that information representing the change in the communication environment is selectively created, and then a communication environment between the relay device and the mobile terminal is controlled based on the created information.