Abstract: A control arrangement for use in a hydraulic control system including a control valve having at least two movable elements, such as spools or poppets, that is adapted to control a main flow through the control valve. The control arrangement further includes a control unit. In an embodiment the control arrangement is adapted to control the operation of the control valve in accordance with a first control scheme, monitor an operating parameter of the control system, and control the operation of the control valve in accordance with a second control scheme in the event that the value of the operating parameter falls outside of a predetermined range.

Abstract: A joystick actuator includes a fixed housing, a joystick member which is manually movable relative to the housing in at least one direction and which incorporates a light transmitter, a detection circuit within the housing incorporating at least two position sensing light detectors for receiving light of varying intensity from the light transmitter as the joystick member is moved in the at least one direction and a further light detector between the two position sensing light detectors. The actuator also includes parts in the detection circuit for making use of the output signal of the further light detector to linearize or substantially linearize the output signals of the position sensing light detectors. The detection circuit is arranged to provide an electrical output signal dependent on the light received by the light detectors and indicative of the position or rate of movement of the joystick member.