Abstract: A high speed printing head comprises a circular array of stylii drivers for printing characters in a dot matrix format. Each driver includes a permanent magnet and bucking coil electromagnet which when energized causes a stylus to impact a printing surface. The stylus is carried on the end of an arm supported by crossed horizontal and vertical supporting flexures at its other end whereby the arm pivots about a virtual axis lying near the plane of the working air gap of the electromagnet to reduce wear of the pole piece and armature and increase impact rebound of the arm. The magnetic structure and arm structure intersect only above the pole piece reducing flux leakage and size and weight of the structure. The arm and flexure structures are non-magnetic except at said region of intersection to reduce, in conjunction with the single region of intersection of said structures, cross-talk between adjacent drivers.

Abstract: Recognition of characters, particularly handwritten characters, is facilitated by examining a character for holes (i.e. non-character portions enclosed by character portions), split characters (i.e. disconnected character segments), overhangs and underhangs (i.e. extensions of character segments to the left or right of other segments). In a specific embodiment a character to be recognized is quantized into a grid of vertical column and horizontal rows and then shifted in parallel by column, serially by row through a recognition mask which examines one row at a time. Results of the examination may be used either as positive character recognition or as pre-recognition exclusionary information to resolve possible ambiguities in conventional recognition processes.

Abstract: A threshold level is automatically varied to follow variations in an input signal reference level. In the disclosed embodiment the reference level is that produced by photodiode-amplifiers in an OCR machine when viewing white or non-character portions of a page, the reference level varying as a function of the change in the length of the optical path during a scan across the page. The threshold level is compared to the input signal level to determine whether a character segment is viewed by the photodiode. Variation of the threshold level is achieved by low pass filtering individual output signals from some of the photodiode-amplifiers and then averaging the filtered signals to provide the adjusted threshold.