Communication and a communications apparatus are controlled with a communication intermediating apparatus. The on-board apparatus specifies an application from a command included in reception data received from the fixed station and starts a corresponding processing, when an acquired command is a menu selection command. An interface to the control node enables exchange of control messages between the data function and a control function in the control node. The above estimated negative hydraulic-fluid leakage flow, negative hydraulic-fluid work flow and positive fluid flow are added to a total flow communicating with the accumulator, and a value is obtained of the volume of the hydraulic fluid in the accumulator from the total flow communicating with the accumulator for controlling an operation mode of the pump. A microcontroller converts data received about changes in differential pressure and temperature sensing means to digital format and transmits the data along two differential digital lines to a driver and output connector. Also, an assembly of one or more conduits and one or more devices is provided in which a test pressure may be measured near the conduit or conduits, which may allow for adjustment of fluid flow through the conduit or conduits to adjust the pressure in the conduit or conduits.