Abstract: In a bill examination device in which a signal pattern obtained by scanning the bill with a photo-detector or a magnetic detector is compared with a reference for testing the authenticity, the signal is subjected to differentiation or removal of a direct-current component before the comparison. The effect of the differences or offsets of the detector or its associated circuit due to manufacturing variations, temperature change, or aging, and differences in the darkness of printing or smudge on the bill is reduced, and the reliability of the authenticity test is improved.

Abstract: A bill discriminating device includes sensor circuitry for scanning and reading all the printed patterns of a bill to be discriminated and producing discriminated data including bill scale data, the bill scale data representing the density of the printed patterns. A data storage memory stores the discriminated data including the bill scale data from the sensor circuitry. A bill scale data selector selects the bill scale data from the discriminated data and fetches the selected bill scale data from the data storage memory. A data segmentor segments the thus selected and fetched bill scale data into a plurality of blocks of data. An arithmetic unit subjects the segmented bill scale data to an arithmetic averaging process for each block of data. A reference data storage memory stores reference data for each of a plurality of predetermined reference bills.