Abstract: A stepping motor is employed as a rotary position sensor by applying a bias current to one pair of its windings and sensing the signals produced by another pair of windings. The bias current produces a magnetic detent which defines the increments of rotation and the phase relationship of the signals produced by the other two windings indicates direction of rotation.

Abstract: A system for simultaneously displaying graphics and alphanumeric data on a raster scan display screen is particularly suited for use with a computerized and numerical control system for controlling machine tools or the like. A first memory stores a multi-bit data word which includes first and second subgroups of data bits respectively corresponding to an alphanumeric character and several modifications of the data to be displayed. The first subgroup of data bits defines a character field on the screen which consists of lines and columns of pixels, and is delivered as an address to a character generator which produces an output representing an alphanumeric character. A second memory stores graphics data in the form of multi-bit words which correspond to groups of pixels on each line of the screen. The alphanumeric and graphics data, as well as the second subgroup of modification bits, are selectively gated to a decoder which outputs signals to a video generator according to a preselected priority scheme.