Abstract: An article of paper currency to be validated is scanned magnetically along the front to obtain a set of magnetic sample values and optically along the back to obtain a set of optical sample data values. Position-shifted versions of the magnetic data values are compared with stored sets of magnetic reference values for various denominations to obtain error figures for each denomination and degree of position shifting tested. A first indication of the denomination of the currency is generated on the basis of the least of the error figures so obtained. Position-shifted and amplitude-shifted versions of the optical data values are similarly compared with stored sets of optical reference values for various denominations to obtain error figures for each denomination and combination of position and amplitude shifting tested. A second indication of the denomination of the currency is generated on the basis of the least of the error figures obtained by this latter method and compared with the first indication.

Abstract: Apparatus for accepting a U.S. bill or other paper currency having a portrait area printed with magnetic ink with spaced parallel lines in the background portions thereof. A pair of zones of predetermined length normally containing said portions and disposed a predetermined distance from an edge of the bill are first magnetized and then moved past a magnetic head to produce a train of pulses spaced by time intervals corresponding to the distance between the lines. For each scanning zone the number of such time intervals falling within a predetermined range is counted, and the bill is rejected unless the number of such time intervals counted is at least a predetermined minimum. In another aspect of the disclosure, an area of the bill normally containing nonmagnetic ink is scanned by a sensor that generates a pulse edge on traversing a magnetic bill portion, and the bill is rejected if a predetermined number of pulse edges are generated during the scanning of such area.