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.