Abstract: A read/write head circuit that insures the equivalence between the driving signal frequency and the resonance of the tank made up of an inductive sensor in parallel with a capacitor. The invention makes use of a voltage controlled oscillator (38)--VCO--to generate synchronism pulses (54) from the driving current generator (33), the controlling voltage being obtained from the comparison between the driving current and voltage phases through the resonant tank made up of the sensor (11) and capacitor (17) connected in parallel. The circuit further provides an amplitude limitation of the driving signal through the control of the driving current pulses applied to the inductive sensor.

Abstract: Apparatus for verifying, validating and codifying an inductive card having a plurality of individual credit cells, each of which represent a credit value until burned out so that a partially used card has valid and burned-out cells. The apparatus includes a card reader having a plurality of sensors corresponding to the plurality of credit cells on the inductive card, a device for comparing the distribution of burned-out cells on the card with a standardized order of burning out cells in using the card, and an indicating device for showing the quantity of credit values available on the card and whether or not the card is valid. The card reader has a matrix of sensors arranged in columns and rows, a set of column drivers, a set of row drivers, and is capable of detecting the condition of each credit cell on the card. The apparatus has an independent power supply and the comparing device has a microprocessor with a keyboard and a ROM memory.

Abstract: A reading head able to process both inductive debit cards and chip cards comprising two dissimilar complementary portions, the internal surfaces of the portions defining the channel housing the data card inserted in the head, the first portion (80) having inductive sensors (83) for the reading of inductive credit cells and the second portion (140) having a magnetic metal plate (142) which completes the magnetic circuit of the inductive sensors, as well as contact pins (162) engaging the terminal pads on the surface of the card. The portions remain normally kept apart by a first set of mechanical coupling devices (84, 85, 86, 88, 89, 93, 94, 95, 144) placed between the two portions, the opening thus provided being substantially wider than the thickness of the card, the mutual approximation of the portions being provided by the mechanical devices at the final part of the card's insertion travel.