Abstract: A parallel analog-to-digital ("A/D") converter utilizing only N comparators and at least N-1 summing networks made of the simple resistance elements. The A/D conversion process operates asynchronously without need for registers, a clock circuit or latches and determines at a high rate of speed the N output bits for a given analog input signal. Each of the summing networks produces a composite analog signal which is fed into a respective one of the comparators. The digital output bit produced by each comparator is fed into the summing networks associated with those comparators whose output bits are less significant. Accordingly, when all output bits are changing on account of a new analog input value, the converter determines the most significant bit first, the next most significant bit next, and so on, until the least significant bit is determined.

Abstract: A method and apparatus for determining whether a newly-signed signature and a previously recorded signature were made by the same person. The method and apparatus include the steps of and apparatus for scanning a document containing the newly-signed signature to provide an electrical signal representative of the reflectivity of the newly-signed signature and the document and generating a signature envelope from the electrical signal with the envelope being formed of selected points on the signature. A plurality of characteristics of the newly-signed signature are then calculated based on the location and magnitude of the selected points forming the signature envelope with respect to a reference line. The calculated characteristics of the newly-signed signature are then compared with corresponding characteristics of a standard signature formed from a group of previously recorded signatures and a signature verification decision is generated based on the degree with which the compared characteristics match.

Abstract: A pressure-sensitive writing stylus and associated circuitry for use in a personal identification system that uses handwriting pressure as an identifying discriminant. The stylus includes a housing, and a cartridge mounted within the housing. A capacitive transducer, preferably a piezoelectric crystal, is mounted contiguous with the upper end of the cartridge and is responsive to axial loading forces in the cartridge caused by contact of the cartridge tip against a writing surface. The transducer outputs a signal related to the time rate of change of the loading force or pressure. The associated circuitry receives the transducer output signal and amplifies and integrates it in successive stages to produce an output signal directly related to the user's handwriting pressure.