GB1251615A - - Google Patents

Abstract

1,251,615. Token-freed apparatus. TRAVAUX INDUSTRIES POUR L'ELECTRICITE TRINDEL. 23 Feb., 1970 [28 Feb., 1969], No. 8588/70. Headings G4T and G4V. A time check system comprises a token 1, including a capacitor 4, recording means (8, Figs. 3, 4) to charge the capacitor by electromagnetic induction and reading means 24 responsive to the residual voltage on the capacitor at a later time. The token includes a winding 3 and a diode 5 in series with the capacitor 4, a resistance 6 in parallel with the capacitor and a magnetically operated switch 7, e.g. two flexible reeds of ferromagnetic material, in parallel with the diode. The token is validated by inserting the winding 3 in the air-gap of the recording electromagnet (9). The capacitor is therefore charged to a voltage whose value depends upon the time of charging, the voltage of the electromagnet and the time-constant of the capacitor-resistance circuit. This voltage decays at a rate dependent upon that time-constant, which can be made very long if the resistance is dispensed with. The token may be used to free an exit gate, e.g. of a car park, provided the capacitor voltage is above a predetermined value, so that the token is valid only for a predetermined time. On presentation at the exit the token is inserted into reader 24 so that winding 3 occupies the air gap 27 of electromagnet 25 whilst switch 7 is adjacent permanent magnet 29. Preferably two electromagnets are arranged so that a token can be read whichever way it is inserted. The operation of switch 7 by magnet 29 shortcircuits diode 5, so that capacitor 4 discharges through winding 3, producing a pulse in read-out coil 26. If the signal is sufficiently large, i.e. if a sufficiently short time has elapsed since the token was energized, the pulse triggers the monostable shaping circuit 31 which sends a rectangular signal to the OR gate 32. The latter transmits a signal which is amplified at 33 and actuates relay 34 to close contact 35 which, for example, lifts the car park exit barrier.