A coupler apparatus for coupling electrical signals between an actuator and an end effector is disclosed. The end effector is disposed at a distal end of an elongate articulated positioner and used to position the end effector for performing surgical operations. The articulated positioner has a central lumen and the apparatus includes an elongate body sized to be slidingly received within the central lumen of the articulated positioner, at least a portion of the body being operable to flex during movement of the articulated positioner. The apparatus also includes a plurality of electrical conductors extending through the body, and a plurality of proximal electrical contacts disposed at a proximal end of the body for removably connecting each of the electrical conductors to respective electrical signal lines at the actuator.