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摘要

1,135,041. Detecting coatings on tickets and other carriers. PLESSEY-UK Ltd. 27 Jan., 1966 [11 Feb., 1965], No. 5978/65. Heading G4T. A ticket 6 (Fig. 3) or other carrier with a magnetic or conductive coating is placed for test so that it influences the flux coupling the magnetic cores 14, 16 of a primary winding 11 (Fig. 1) and a secondary winding 13, and a winding 12 on a further core 15 coupled magnetically with the cores 14, 16 is either connected to oppose the field produced by the winding 11, as in Fig. 1, or is connected in series with the secondary 13 to oppose the voltage in this winding. The apparatus illustrated is designed to pass tickets with coatings lying in a predetermined permeability range while rejecting tickets with coatings whose permeability lies above or below this range or which are conductive. The apparatus cuts a portion from a valid ticket and imprints the remainder. The residual voltage from the secondary 13 when no ticket is present is arranged to be in the opposite sense from the voltage when a valid magnetic ticket is present. Thus if the coating on a ticket is below the acceptable permeability range (or the coating is conductive) the lower coupling provided causes a higher residual voltage. A coating with a permeability greater than the permitted range reverses the residual voltage so that in both cases the absolute value of the voltage is greater for an invalid ticket than for a valid ticket. The output from the secondary 13 (after correction by a pre-set component RV1) is amplified at 8 and rectified at 9a. The rectified voltage is compared with a rectified voltage from a further generator 3 in a comparator 9 which can be arranged to give a positive voltage for an invalid ticket and a negative voltage for a valid ticket or vice versa. The position of the ticket in the comparator is detected by two micro switches, one operated when the ticket is partly inserted and the other when the ticket is fully inserted. When the latter has been operated the signal from the comparator 9 causes the end section of a valid ticket to be cut away by a guillotine and an imprint to be made on the remaining portion of the ticket. The guillotine cannot again be operated until the microswitch indicating partial insertion of the ticket has been released and made again. The pressure of an invalid ticket causes a warning to be given. The tester may be fed by generators 1, 2, 3 on a single shaft 4 or by a transistor oscillator.