Method of capacitively reading coded cards and device for carrying out such a method.

p0001The present invention relates to a method for capacitive reading code maps, used in the transmission electrodes of a reader to a radio frequency signal through a provided for a code card slot to be transmitted to receiver electrodes on the opposite side of the slot, and wherein the signal thus received by the effect of information given on the code menu changes. The invention also relates to an apparatus for capacitive reading code maps for performing the method, with a high-frequency generator, transmitting electrodes, receiver electrodes relative to the transmitting electrodes and provided between the transmitting electrodes and the receiving electrodes slot for insertion of a key card, wherein the transmission electrode for transmitting a high-frequency signal are connected to the generator and wherein a capacitively transmitted signal between the electrodes by the action of pieces of information given on the code card can be changed.

p0002In this type of known from the prior art devices for reading code maps the identification of a code card is not carried out when the code card has been fully inserted into the receiving slot of a reading device and has reached its static end position. This principle for reading a code limits the number of possible code combinations on a code card at a relatively modest size relative to the number of transmitting / receiving electrode pairs a reading device. But now it is obvious that a larger number of transmitting / receiving electrode pairs can increase the price of such a device. Another drawback with the known from the prior art devices for capacitive reading code cards is that they are quite sensitive and therefore Unzu reliably for interference. However, such devices for reading code cards are also used where a particularly high reliability is required and a large number of code combinations is needed. Such code cards and corresponding reading devices are becoming increasingly common to operate a variety of automatic devices, such as for opening of locks, in credit card machines, for example, in service stations, in bank credit cards, for example, ATMs, etc .. Because it is so far not been possible, the disadvantages explained above the capacitive reading code cards off in devices, primarily inductive and magnetic devices for reading code cards have become popular.

p0003The object of the invention to provide a new and better method for capacitive reading code cards, with the largest possible number of code combinations on a code card is accessible and this code combinations by Yerwendung a minimum number of transmitting / receiving electrode pairs in the reading device reliably identified ,

p0004The inventive method, in which the aforementioned object is achieved is characterized in that by successive (zueßnander adjacent) transmission electrodes different signals are sent that the signals alternately by inserting the code card between the electrodes by means of the guide points of the code card and a same receiving electrode are transferred, that a particular characteristic of each signal received by the receiving electrode, in which the signals of the transmitting electrodes are different, in relation to one of the transmission signals is monitored and that a change of this monitored characteristic feature is granted as to be read guidance point of the code card.

p0005Advantageous embodiments of the inventive method, and characteristics of a device for implementing such a method will be apparent from the claims.

p0006The invention is further illustrated by an only one embodiment illustrative drawing; it shows<ul><li>Fig. 1 in top view, a code to be read card,</li><li>FIG. 2, a schematic representation of the distribution of capacitive identification electrodes in one card reader</li><li>Fig. 3 shows a schematic representation in cross section, the electrodes for reading a code in a read apparatus according to the invention,</li><li>Fig. 4, the signals at different electrodes in Fig. 3,</li><li>Fig. 5 is a schematic representation in cross section the construction and relative position of positioning electrodes of a device of the invention, also various preamplifier in conjunction with a computer core for processing the signals and</li><li>Fig. 6 is a graph that lets a readout zone recognize B of electrodes for reading the code in relation to the distance traveled by a code card path S A of positioning electrodes and a read-out zone.</li></ul>

p0007A card reader is used, an existing plastic code card 1 to read, preferably the "service standard" dimensions 86 mm. 54 mm equivalent. The code card 1 has five lines of code, of which one is utilized for determining the position of the code card reader 1 relative to a 11th This line has only a guidance point 3 for positioning. The other four lines have a total of 31 guidance points 2 to form the code. A code is formed in that a certain number of pieces of information given 2 are designed for the code to be electrically conductive points. It is easily understood that the present in the illustrated embodiment, 31 guidance points 2 will be able to realize an enormous number of code combinations. The leading edge of the code card 1 has a blank space. 4 The rear edge has guide points 5 to show a possible misplacement of the code card 1 can.

p0008Fig. 2 shows how the electrodes of a reader 11 may be arranged. The position of the code card 1 relative to the reader 11 is read by 8 pairs of electrodes 13, whose construction will be explained later in connection with FIG. 5 in greater detail. The further electrodes 12 provided for reading a code next to each other are arranged in a single column that extends transverse to the insertion direction of the card code first The number of electrodes 12 for reading a code is four in accordance with the number of lines of the guide points 2 to form the code.

p0009Each electrically conductive guidance point 2 on the code card 1 is read by means of a capacitive sensor which is shown in Fig. 3. From a generator, a voltage of about 5 V (peak / peak) at a frequency of about 500 kHz with a substantially rectangular waveform is generated. These signals are coupled to the electrodes 12a, 12b on the transmitting side of the sensor. A kasenumkehrstufe 7 serves the phase of the signal f₁ 12a on the electrode in comparison with the phase of the signal <o>f</o>_<o>1</o> reverse to the electrode 12b (see. Fig. 4).

p0010If no senior guidance point 2 exists between the electrodes, so the signal is f₁ capacitively transmitted to the receiving electrode 12th A signal received by this receiving electrode 12 is od signal in a preamplifier ninth like. Amplified to the voltage level of 5V. Because of the rise time of the preamplifier 9 is the signal obtained in f₂ a short delay time T_D from the transmitted signal f₁ delayed.

p0011A code card 1 inserted into the slot between the electrodes with a guidance point 2 for reading a code, so there is the guidance point 2 in a position in which the receiving electrode 12 is partly or completely covered by it. Then, the congruent surface of the electrode 12b and the guide point 2 is greater than the coincident surface of the guide point 2 and the electrode 12a. From the electrode 12b is the signal<o>f</o>_<o>1</o> transferred to the guidance point 2 and from there further to the receiving electrode 12. As a result, the phase of the signal f₂ about 180⁰ with respect to the phase of the signal f₁ shifted. The finding of the guide point 2 or the phase reversal of the signal f₂ is displayed by the fact that from the signal f₂ at the rising edge of the signal f₁ Test values ​​are taken. As a result, when a guidance point 2 is present, an output value "1", otherwise "0".

p0012The design of the electrodes which are used for determining the position of the code card 1 is slightly different from the construction of the sensor for reading the code portion of a code card 1. From the sectional view in Fig. 5 appears that successive transmission electrodes 13a, 13b signals with mutually different phases result, since the signals f and <o>f</o>_<o>1</o> alternating with them. A signal<o>f</o>_<o>1</o> from the generator G by means of a phase inverter 7 into a signal f₁ vice versa. The receiving electrodes 13 have a small area and are, viewed in the insertion direction of the code card 1 opposite to the front edge of the respective transmitting electrode 13a, 13b. Between the receiving electrodes 13 ground electrodes 13c are further provided. If now a code card 1 inserted into a slot between the electrodes, thus achieves positioning guidance point 3 for example, an electrode 13, whereby the phase of the received signal f₂ is reversed. This effect is due to the fact that the congruent areas of the guide point 3 and the preceding transmission electrode 13b is greater than the congruent areas of the guide point 3 and a transmitting electrode 13a above and opposite the receiving electrode. 13

p0013The phase of the received signal f₂ changes back again as soon as the guidance point 3 further below the transmitting electrode 13a travels above the receiving electrode. 13

p0014The electrode arrangement results in a read-out zone A for positioning guide points 3, which is narrower than a read-out zone B for the electrodes 12 for reading the code (see. FIG. 6). For this reason, it is absolutely certain that if a positioning guidance point 3 is found a code card 1, the possible code-guide points 2 this special cross-column have been determined with certainty and that the data which characterize the code of this column , for example, "1 1 0 1", regardless of the slide speed and the direction of insertion of the code card 1 are correct. A practically occurring region for the insertion speed of the code card 1 is between 0 and 50 m / s.

p0015The preamplifier 8 and 9 of the receiving electrodes 12, 13 can for example be configured as a non-buffered inverter in CMOS technology.

p0016A processor core 10 for the data signals can be accomplished using freely available integrated circuits in the di- ^Gare designed italtechnik usual manner. The design of such a computer core 10 depends on the particular application.