A high frequency bus system which insures uniform arrival times of high-fidelity signals to the devices on the high frequency bus, despite the use of the bus on modules and connectors. An actuator responsive to nozzle diameters opens and closes shutters blocking nozzle entrance. The separator for fuel cells includes an insulating unit that exhibits low gas permeability and superior electrical insulation property, and the current-carrying unit that exhibits superior strength characteristics and conductivity, thus increasing voltage generated per one cell and considerably increasing a power generated per a constant area, when applied to the fuel cells.