Systems and techniques for signal filtering are described. The spokes each have a base attached to the body portion and a blunt tip located radially outwardly thereof. The alignment configuration uses a global coordinate reference system by providing a plurality of global reference marks that encompass up to the entire substrate wafer. The cage comprises a central circular disc with an outer edge and top and bottom sides. The check valve prevents standing fluid in the top drive from spilling onto the rig floor when the tool is withdrawn from the drill string. The body has a prism shape with a substantially planar upper surface which can bear against the superior vertebral endplate and a substantially planar lower surface which can bear against the inferior vertebral endplate.