Abstract: A currency counter for counting currency notes withdrawn from a supply and advancing the notes one by one along a path past a density detector and a magnetic material detector to a stacker at a delivery location upon energization of a common drive motor in which an amplifier responsive to the density detector is automatically calibrated each time the counter starts and in which density and motor current signals are combined for doubles detection. The motor speed is adjusted for document length to provide a predetermined number of counts per minute. An adaptive counterfeit check is made. The motor is deenergized at the end of a batch count and momentarily reenergized to ensure that the last note of the batch is stacked.

Abstract: A currency validator for testing both the magnetic and electrically conductive properties of a currency note in which core legs of magnetic and conductive material form spaced first and second gaps. Windings carried by the legs produce signals indicative of the magnetic property of a note moving across the first gap. A detector connected across the second gap indicates the presence of conductive material bridging the first gap.

Abstract: A method of and apparatus for determining the genuineness of a document such as a currency note printed at least in part with magnetizable ink in which there is produced a first signal as a measure of the saturation magnetization of a portion of the document printed with the ink and a second signal as a measure of the remanent magnetization of said portion and in which the ratio of the second signal to the first signal is determined as a measure of genuineness of the document.

Abstract: Counterfeit detection apparatus in which the coils of the magnetic head are utilized to produce a saturating current for the paper currency being examined which is sufficient to bring the magnetic ink printed upon the paper currency close to the saturation point to greatly facilitate the detection operation.

Abstract: A magnetic detection circuit in which the sensor signal is integrated over the length of the examined sheet and compared with a pair of reference levels to establish the presence of too much or too little magnetizable material. The integration technique assures proper operation in spite of changes in feed rate.