Hydraulic circuits transmit and control power from a mechanical input to a mechanical output by means of liquids, mostly oils. Power is transmitted hydrostatically, where high pressures make static forces dominate over dynamic forces, and energy is transmitted mostly through static pressure at low flow velocities.
Circuits are composed of a number of hydrostatic components which are connected to each other by means of piping, manifolds, or directly, to enable transmission and control of power or signals through liquids.