a fixed base router has a base supporting an upright wall . a motor based driver assembly is received in a cylindrical interior space delimited by the wall and movable along a spiral path . a read - out system includes a position sensor that detects and applies the displacement of the driver assembly along the spiral path to a processor based circuit , which in turn generates a signal indicating the displacement and a display device showing up the displacement for visual inspection . the read - out system allows for precise positioning the driver assembly and thus setting a cutting depth of a tool bit carried on and driven by the driver assembly so that adjustment of positioning of the tool bit is made simple , readable and precise .