Abstract: In a method and apparatus for decoding data recorded on magnetic storage medium such as a "swipe card" to yield decoded data values, a magnetoresistive sensor is used to read the data as a pulse stream from the medium and to measure the widths of the received pulses. The data is preferably stored in the medium by the technique of two-frequency phase coherent recording (F2F). By comparing the widths of pulses to be decoded with the widths of previously read pulses to which data values have already been allocated circuitry for derivin a clock signal from a self-clocking recorded signal can be dispensed with. Pulse widths may be measured by monitoring the output of counters (20) incremented by a fast clock for the duration of each pulse, and the pulse widths are compared by comparing counter outputs stored in a memory (28) using a microprocessor (26).

Abstract: When an electrically conducting material is subjected to an alternating magnetic field local changes in the magnetic field adjacent to the conducting material are detected by a detector comprising a magnetoresistor or Hall crystal which generate an electrical signal when subjected to the magnetic field.The process and apparatus can be used to identify, classify and locate electrically conductive material.The detectors can be of the order of a few millimeters in size and so can be used to detect local changes in the magnetic field over correspondingly small areas of the material.The invention is particularly useful in identifying coins used in coin operated machines.

Abstract: The present invention provides thin film magneto-resistive readout apparatus for providing readout from magnetic memory devices such as magnetic tapes, the apparatus comprising a thin film magneto-resistive readout head element, a narrow pulse generator for applying sensing current to the readout head element in the form of trains of narrow pulses, and a signal averaging circuit connected to receive output signals from the readout head element for deriving an average output signal for the pulses in each train.