One embodiment of an occupant propelled roundabout may have a body. At least one driver is disposed between the rail elements. Upon the rise of the piston 22, the air in the first chamber R1 is compressed, and the compressed high-pressure air is discharged to an accumulator 12 through a discharge valve 25. In other aspects, the invention includes a program storage medium encoded with instructions that, when executed, perform this method and a computer programmed to perform this method. In each of the first and second switching control processes, the number of repetition times of the second switch operation is counted until the potential of a terminal of a reference capacitance changes to a set potential. The attachment having various characteristics and capacity, such as a hydraulic breaker or a crusher, can be applied to the hydraulic circuit for an attachment in a simple configuration.