Abstract: An arrangement for supplying pilot oil to a servo-valve arranged to activate a main valve of a hydraulic system. The hydraulic system also includes a hydraulic oil pump, a valve located between the pump and the main valve, a pressure reducing valve located between the pump and the servo-valve, and at least one auxiliary assembly is arranged to deliver an electric signal to electromagnetic means arranged to activate the servo-valve. In accordance with the invention, the valve located between the pump and the main valve is arranged to be substantially or fully closed when standing at a given, pre-determined pressure corresponding to the servo pressure required by the servo-valve in order to carry out its intended function, and is arranged to be open when the pressure slightly exceeds the aforementioned pre-determined pressure. An electromagnetically operable shunt valve is located between the pump and pressure reducing valve and, when open, to pass oil direct from the pump to a tank.

Abstract: A control assembly comprises a housing; a control lever extending from the housing and pivotally mounted therein; spring means arranged in the housing and effective to return the control lever automatically to a neutral position; and a potentiometer for converting movement of the control lever relative to the housing from the aforesaid neutral position to an electrical signal. According to the invention, the spring means (4) comprises two mutually connected tubular parts (8,9), between which the end of the control lever (3) located in the housing (2) is mounted for pivotal, but not rotational, movement, wherein in the neutral position of the control lever (3) the longitudinal axis of respective tubular parts (8,9) extends substantially at right angles to the longitudinal axis of the lever.