Mechanisms or apparatus convert a number of inputs via a number of input members into a number of output movements of an output structure, providing control in three degrees-of-freedom (DOF), for example control over roll, pitch and yaw of the output structure. Inputs may be rotations about a common axis of rotation, for example via a first ring, a second ring, and one or more plates, concentrically array. Rotation of the first ring may control a first DOF, rotation of the first ring may control a second DOF, and rotation of the plate may control all three DOF. Three concentrically arrayed tubular shafts may be employed, providing a through-passage or cable fluid conduit run to accommodate wires, optical fibers, fluid carrying conduits. Such may be particularly advantageous when employed as part of a robot, or other device with a tool or sensor or transducer located at or proximate a distal end thereof.