governor, automatic device used to regulate and control such variables as speed or pressure in the functioning of an engine or other machine. A governor may be an electric, hydraulic, or mechanical device, or it may employ some combination of electric, hydraulic, and mechanical components. The constant-speed governor serves to keep the speed of an engine constant under changes in load and other disturbances. It is very often a mechanical device, employing centrifugal force. Such a governor contains weights, called flyballs, each attached to the end of an arm. The arms are arranged, like the spokes of wheels, around a central spindle and are connected to the inlet valve (commonly called the governor valve). The flyballs are so attached that they move away from the spindle as the speed increases (decreasing the fuel or steam to the inlet) and come closer to the spindle as the speed decreases (increasing the fuel or steam), thereby keeping the speed constant. Varying degrees of closure and the speeds at which they are to occur can be set in advance. Where changes are required while an engine is in operation, a variable-speed governor is employed. A governor-synchronizing device is used to equalize the speed of two or more engines driving electric generators before they engage the generators. In order to control the speed of some engines, a governor's output must be strengthened by connecting the output to a hydraulic amplifier.