A hydraulic system includes at least one circulation pump assembly (2) provided with a speed controller (26), at least one hydraulic circuit (A, B) connected to the circulation pump assembly (2) as well as at least one mechanical switch device (86, 88; 120, 122) which is mechanically subjected to pressure by a fluid in the hydraulic circuit (A, B) and which can be moved into at least two different switch positions. The mechanical switch device (86, 88; 120, 122) moves by the circulation pump assembly (2) hydraulic coupling via the fluid. The speed controller is configured to initiate a movement of the switch device (86, 88; 120, 122), by at least one hydraulic force acting upon the switch device (86, 88; 120, 122) and causing a movement of the switch device (86, 88; 120; 122) via the hydraulic circuit, via a speed adaptation of the circulation pump assembly (2).