United States Patent 3868057

An improved form of credit or identification card and a system for verifying the propriety of ownership thereof. The card comprises, in addition to the conventional embossed indicia which ordinarily includes a name and an account number, a laminated or encapsulated center layer of material upon which is deposited an electrical circuit consisting of a matrix of electrical conductors and semiconductors coupled to a plurality of contact points. At least three of the contact points are coupled to certain ones of the semiconductor devices thereby providing a code number unique to each card and the remaining contacts are coupled to other parts of the circuit to give a false code. A card verifier has a like plurality of electrical contacts adapted to engage the card contacts and a plurality of selectors for selectively coupling the circuit in the card with a circuit in the verifier so as to produce a YES or NO output signal to verify selection of the proper code number.

Application Number:
Publication Date:
Filing Date:
Primary Class:
Other Classes:
235/443, 235/487, 235/488, 235/492, 283/83, 283/904, 340/5.86
International Classes:
G06K7/06; G06K19/067; G07F7/10; (IPC1-7): G06K5/00; G06K7/06; G06K19/06
Field of Search:
View Patent Images:
US Patent References:
3665162IDENTIFICATION SYSTEM1972-05-23Yamamoto et al.
3221304Electronic identification system employing a data bearing identification card1965-11-30Enikeieff et al.
3142823Punchable memory card having printed circuit thereon1964-07-28Lewin et al.
3028659Storage matrix1962-04-10Chow et al.
2817824Card switching device1957-12-24Albright
2629166Method of forming resistor assemblies1953-02-24Marsten et al.

Primary Examiner:
Cook, Daryl W.
Attorney, Agent or Firm:
Lyon; & Lyon
Parent Case Data:

This is a continuation-in-part of my previous application, Ser. No. 157,928 filed June 29, 1971, now abandoned.
I claim

1. An improved identity verification system, comprising:

2. The system set forth in claim 1 wherein said indicator means includes first and second output means, said first output means providing a first output signal when all of said contact points are coupled to said first circuit means, and said second output means providing a second output signal when any of said contact points are coupled to said second circuit means.

3. The system set forth in claim 1 wherein said first circuit means comprises a three terminal semiconductor device.

4. The system set forth in claim 1 wherein said first circuit means comprises a unijunction transistor.

5. The system described in claim 1 wherein said first circuit means comprises a NAND gate.

6. The system described in claim 3 wherein said second circuit means comprises a plurality of diodes coupled in randomly-oriented fashion between various of said contact points.

7. The system described in claim 1 wherein:

8. The system described in claim 1 wherein:

9. The system described in claim 1 wherein:

10. The system set forth in claim 9 werein said indicator means comprises a light-emitting diode coupled to the output conductor of said first rectifiers, a silicon-controlled-rectifier coupled in parallel with said diode, said silicon-controlled-rectifier having a gate electrode coupled to the output conductor of said second plurality of rectifiers.

11. The system described in claim 1 wherein said card reader includes means for selectively sensing said contact points, said means comprising means for receiving a card in the reader, contact means in said receiving means for contacting each of said contact points, a plurality of switching means coupled to said contact means for selecting certain ones of said contact means according to the aforesaid system of index numbers assigned to the contact points on a card, said switching means having indexing means for selecting contact points according to said series of code numbers.

12. The system described in claim 11 wherein said indicating means in said card reading means comprises a fourth circuit means, said fourth circuit means having first and second output indicating devices, a source of electrical power, means for coupling said source of power to said switching means, current responsive means coupled to said switching means and said indicating devices, said current responsive means being operative to energize said first output device when said switching means is coupled only to said first circuit means in a card, said current responsive means operative to energize said second output device when said switching means is not coupled only to said first circuit means.

13. An improved identity verification system, the combination comprising:

14. An improved identification card and a system for verification thereof comprising, in combination:

15. The system described in claim 12 wherein said current responsive means comprises a relaxation oscillator.

16. The system set forth in claim 1 wherein said first and second circuit means of said card have portions thereof coupled together therein whereby external electrical measurements taken at said contact points will not indicate which contact points are unique to said first circuit means.

17. The system as set forth in claim 9 wherein said first and second circuit means of said card have portions thereof coupled together therein whereby external electrical measurements taken at said contact points will not indicate which contact points are unique to said first circuit means.

18. An improved identification card verification system comprising:

19. An improved identification card verification system comprising:


The present invention relates generally to a credit card system which makes possible the virtual elimination of credit card misuse. The ensuing description deals with the use of the invention as a credit card, although it will be apparent that potential scope of the invention would include any use as a positive means of identification. The advent of credit cards for the convenient acquisition of goods and services in lieu of the use of currency has carried with it considerable problems in what may be generally called credit card misuse. Misuse of credit cards includes the use by others of cards which have been either lost or stolen, unpremediated felonious users who have received unsolicited credit cards in the mail, but who deny having used them, outright counterfeiting of credit cards, and the use of cards by the rightful owner thereof beyond the agreed credit limits. In such cases, substantial financial liability may be borne by either the credit card holder, the credit card company or both, and recent reports have indicated that losses sustained on account of credit card misuse total in the hundreds of millions of dollars annually. It is submitted that such losses are sustained as a direct result of the fact that credit card misuse is relatively easy to commit by those persons so disposed because of the lack of a positive and easy means of identification.

Most credit cards currently in use have a place for the signature of the authorized user but this proper signature is seldom, if ever, checked or compared with the actual user's signature because the clerks handling an individual transaction are not competent to analyze the handwriting. Other credit cards currently in use have a picture of the authorized user but again this is not a positive means of identification, it is an inconvenience when the rightful user desires to permit another to use his card, and it certainly does not prevent counterfeiting. Other methods of positive identification have been proposed, such as a fingerprint check or a magnetically-encoded strip of material on the card which can be read by an appropriate card-reading device but these systems are very costly to implement.


The foregoing shortcomings may be eliminated through the use of the present invention inasmuch as the credit card herein proposed is provided with a secret code number which shall be known only to the rightful user thereof. When the holder of the credit card desires to use it, it is inserted in a verification device and the rightful user thereof selects by means of appropriate control on the verification device the code number known only to him and when he selects the proper series of numbers, there will be a visual indication that the number encoded on the card corresponds with the number selected by the card user. Obviously, not knowing the proper number, one who finds or steals the card will not be able to use it. The manner in which the code number is encoded on the card makes it extremely difficult to ascertain the correct code number.

In one embodiment the credit card contains a matrix of contact points, ideally a hundred or more and each contact point can then be assigned a code according to a numerical or alpha-numerical system. Each of the contact points is interconnected with the other by thin deposits of electrical conducting material but rather than being directly connected to one another each of the points is electrically connected to a small deposit of semiconductor material which in the form of diode provides a finite electrical resistance between any two points. Three or more of these contact points are not interconnected in the manner just described but in turn are electrically connected to a semiconductor device having three or more terminals, such as a transistor. The contact points which are connected to the semiconductor device are selected at random in the matrix. It is these three or more points which determine the unique code number for the individual card, as determined by the coding system.

The card verification device contains a plurality of sensing devices adapted to contact the contact points on the card when the card is inserted in the device. The verification device also contains a number of selectors by which the card user selects the contact points corresponding to the code or index number so that the device electrically connects to the three or more terminals which communicate with the semiconductor device. By this method, the semiconductor device is coupled to a circuit in the verification device so that an electrical circuit is completed whereby current will be conducted to indicate a proper selection of code numbers. If the incorrect number is selected, the circuit within the verification device will not be properly completed and an error signal will result. The interconnection of all of the unused contact points through semiconductor material renders it extremely difficult to ascertain the proper code number inasmuch as resistance measurements made upon the card using an ohmmeter, for example, will provide confusingly false readings between any two contact points whether the meter is attached to the proper contact points or not. Thus, resistance measurements made upon all of the contact points trying all of the various combinations will not permit a wrongful possessor of the card to determine the proper code number.

In a modified form of the invention a unique coding circuit employing a series of SCR's is embedded in the card and due to the configuration of this circuit the number of contact points on the card, and therefore in the verifier as well, is reduced to a small number. This circuit still provides a very large number of possible combinations while also providing false code indications if effort is made to decode the same.

It is an object therefore of the present invention to provide a credit card and a credit card verification device whereby improper use can be substantially eliminated.

It is also an object of the present invention to provide an improved credit card system whereby the proper owner of a credit card may utilize it without fear of financial liability on account of loss or theft and in addition permitting the credit card company to utilize the card verification device for accounting purposes.

It is a further object of the invention to provide a credit card verification system which will substantially facilitate the recovery of lost or stolen cards.

Further objects and advantages of the present invention will be readily apparent upon reading the ensuing detailed description in conjunction with the accompanying drawings.


FIG. 1 is a pictorial representation of a form of a credit card verification device showing a credit card in association therewith.

FIG. 2 is an exploded perspective view of a credit card made in accordance with one embodiment of the present invention.

FIG. 3 is an enlarged sectional view showing the relationship of the credit card verifier and the credit card.

FIG. 4 is an enlarged plan view of one embodiment of the intermediate layer showing the matrix arrangement and semiconductors thereon.

FIG. 5 is a circuit diagram of one embodiment of the electrical portion of the credit card verifying device.

FIG. 6 is a plan view of the intermediate layer of the card showing another embodiment thereof employing a NAND gate.

FIG. 7 is another circuit diagram for an alternative electrical portion of the card verifier.

FIG. 8 is the equivalent circuit for the NAND gate employed in FIG. 6.

FIGS. 9a and 9b are circuit diagrams of another embodiment of the present invention showing an improved and simplified coding circuit for the card in FIG. 9a and a simplified code selection and verification circuit in FIG. 9b.


As shown in FIG. 1, the new credit card generally designated 10 comprises three initially separate layers of material which are subsequently permanently bonded together. As is the current practice, the materials used in the three separate layers may be any suitable, somewhat rigid plastic. The top layer 12 would have the same general appearance as do most credit cards today including the name 13 of the credit card holder, his account number 14 and an insignia or name indicating the credit card company as represented by the design 15. The name 13 and the account number 14 are ordinarily embossed on the surface of the card and provide a means for imprinting the name and account numberon invoices. When constructed in this manner, the credit card of the present invention is compatible with credit card imprinting devices currently in use but it is contemplated that the credit card verification device disclosed herein may also incorporate the details of credit card invoice printing devices although it is not deemed necessary to show the details of such construction inasmuch as they are well known in the art.

The bottom layer of the card 16 is a substantially flat member with no raised or embossed indicia thereon but is provided with a plurality of spaced apertures 18 which are symmetrically located over the entire surface of the bottom layer 16 in a grid or matrix fashion defining a system of coordinates. The purpose of the apertures 18 is to provide access to contact points in the interior of the card as will soon be readily apparent.

The middle layer or lamina 20 is also a substantially flat, thin piece of pliable plastic material which is electrically nonconductive as are layers 12 and 16. on the surface of lamina 20 which when bonded will be facing the bottom layer 16 there is deposited or etched a plurality of electrical contact points 22. Contact points 22 are symmetrically arranged on this surface of layer 20 in the same manner as are the apertures 18 in layer 16 providing a system which can be described by numerical or alpha-numerical coordinates and these contact points are positioned to coincide with apertures 18. As shown in FIG. 2 and more completely in FIGS. 4 and 6, deposited on the surface of lamina 20 are a plurality of diodes 24. Each of the contact points 22 is connected to one or more of these diodes by means of conductor paths 26 which are also etched upon the surface of lamina 20. The diodes are thus connected in strings, the polarities being alternated at random, and the strings not necessarily connected together. The exception to the foregoing statement is that three or more of these contact points will not be interconnected to these diodes but will be connected to a semiconductor device.

FIG. 4 shows one embodiment of the invention in which the semiconductor is a unijunction transistor 28 deposited upon a surface of intermediate layer 20 which can be made, according to present technology very small so as not to provide a bulky area or excess thickness in the card. Unijunction 28 has an emitter electrode 30, and two base electrodes 32 and 34. Each of these electrodes is connected through an etched-on circuit path, respectively to selected ones of the contact points 22a, those contact points being ones which are not interconnected to any of the diodes 24. As shown in FIG. 4, in which the set of coordinates established by the contact points is numbered from left to right, it is shown that the emitter electrode 30 is connected to the contact point indexed No. 56, the base electrode 32 is connected to the contact point indexed No. 22 and the other base electrode 34 is connected to the contact point indexed No. 108. Thus, the code number established by the coordinates for the card shown in FIG. 4 is the number 56-22-108.

Turning now to the details of the card verification device, this is pictorially represented in FIG. 1 and indicated generally by the numeral 40. The device 40 includes a slot 42 into which the card to be verified shall be inserted. It would be desirable, in order to assure that the card is properly inserted in the slot 42 to provide the card with some sort of indexing means. It should be obvious that because the contact points are indexed according to a certain numerical order, it is necessary that the card not be reversed. Thus, the card could have a notch cut in one end as shown at 41 in FIG. 1 which would permit the card to be inserted all the way into slot 42 there being an embossment 43 (See FIG. 3) which would be received in notch 41 to permit the card to be inserted all the way. The exterior of the card reading device has a number of selector knobs on the exterior thereof. The first series of knobs 44, 45 and 46 are multiple position rotatable switches used to select an index number. Another series of knobs 47, 48 and 49 are again multiple position switches having three or more positions which select which set of the series of numbers in the combination shall correspond to the number selected by the corresponding number selection switch. In other words, in order to prevent someone from learning the combination of the credit card, the user may select switch 48 to be the first digit whereupon he will set that to the first digit position and then set dial 45 to his first number, in our case that being number 56 then he might select the knob 47 to be the second digit whereupon he will adjust knob 44 to number 22, and so on. After having properly adjusted all of these knobs, the card holder or the attendant depresses button 50 and if the proper card has been properly inserted and the numbers properly selected as aforesaid, an indicator light 52 will be lighted indicating and thereby verifying that the card holder is in possession of a proper card.

As previously described, bottom layer 16 of the card is provided with a series of apertures 18. In FIG. 3, the card 10 is shown inserted in slot 42 with the bottom layer 16 facing downwardly. In the interior of slot 42 there is positioned a plurality of contact members 54 herein shown as electrically conducting spheres. The contact spheres 54 are held in place by a perforated plate 56 having apertures 58 therein, the diameter of which is slightly less than the diameter of spheres 54. The spheres are biased upwardly by springs 60 which also provide electrical conducting paths and to which are connected conductor leads 62. It should be apparent that when card 10 is properly inserted all the way in slot 42 all of the contact spheres 54 will reside in the apertures 18 providing electrical connections to each contact point 22.

FIG. 5 shows one embodiment of an electrical circuit diagram contained in the card verification unit 40 specifically a circuit to operate in conjunction with the unijunction device shown in FIG. 4. The three coordinate number selecting switches 44, 45 and 46 are shown with the contacts being dependent upon the number of contact points designed to be on each card. To the contact points 64 are connected the conductors 62 which connect to the spring contacts as previously described. It should be apparent that all of the contacts 64 assigned No. 1 are connected to spring contact No. 1 and so on. The wiper 66 of selector switch 44 connects through condctor 68 to one of the terminals of each of the digit selector switches 47, 48 and 49. Likewise, the wipers of the other number selecting switches 45 and 46 connect to corresponding terminals on digit selector switches 47 and 48.

Assuming the digit and number selectors are properly set, line 72 connected to wiper 70, will be coupled to the emitter 30 of unijunction 28, line 74 connected to wiper 76 will be coupled to one base 32 and line 78 connected to wiper 80 will be coupled to the other base electrode 34. Conductor 72 is connected to junction point 82 between capacitor 84 and variable resistor 86 which are coupled in series. Capacitor 84 is connected to the negative ground bus 88 to which is connected the negative terminal of battery 90. Resistor 86 is coupled through positive bus line 87 to push button switch 92, relay contact 98a and power switch 94 to the positive terminal of battery 90. Line 74 is connected through series resistor 96 to positive bus line 87. Line 78 is connected to one side of relay coil 87. Line 78 is connected to one side of relay coil 98 the other side of which is connected to negative bus 88. Relay coil 100 is coupled in series with resistor 102 between negative bus 88 and positive bus 87. Relay contact 100a is normally open (operated in response to current in relay coil 100) is coupled across switch 92.

Lamp 104 is coupled in series with relay contacts 98b and 100b, both of which are normally closed, between negative bus 88 and positive bus 87. Lamp 106 is coupled in series with relay contact 100c, which is normallyopen, between negative bus 88 and positive bus 87. In this configurations as properly connected to the unijunction transistor, the circuit is a relaxation oscillator, lamp 104 indicating when power normally open on and lamp 106 indicating proper interconnection Of the unijunction into the oscillator circuit.

Following are typical types and values of the circuit elements employed in this circuit:

Unijunction transistor 2N1671B Texas Inst. Capacitor 84 100 Microfarad Resistor 86 1 Megohm Resistors 96, 102 330 ohm Relays 98, 100 WABCO No. 6739, 26.5VDC, 700 Ohm Power supply 24 VDC

When power switch 94 is closed, lamp 104 lights indicating the system is ready. The DC voltage is applied across the push button switch 92 which when depressed applies current through relay coil 100 closing contacts100a across the switch 92, and opening contacts 100b with the result that lamp 104 goes out. At the same time contacts 100c close turning on lamp 106. Release of switch 92 will not change this condition. DC power will also be applied to base electrode 32 through resistor 96 and current will also flow through capacitor 84 starting it to charge. After a specific time determined by the values of resistor 86 and capacitor 84, the charge on the capacitor will bias the emitter 30 sufficiently to cause unijunction 28 to conduct. When it conducts, capacitor 84 discharges through base electrode 34 and through relay coil 98. The current through coil 98 being sufficient to momentarily energize the relay, contacts 98a and 98b both open, cutting off current to relay 100 and thereby returning the entire circuit to its original state.

The flashing sequence of lamps 104 and 106 indicates proper connection of the card into the circuit. If lamp 106 is green and lamp 104 is red, the sequence will be first a green light, then upon depressing switch 92 a red light for a preset time, followed by a green light again.

Improper connection of the card contacts into this circuit will cause either no change in the initial green light signal or other sequences all indicating wrong code selection. For example, if conductors 74 and 78 were connected across a diode of the wrong polarity, relay 100 would energize turning on the red lamp, but relay 98 will never energize so the red lamp will remain lit. If conductors 74 and 78 were conducted across a diode of proper polarity both relays will energize but contact 98a will keep opening and closing causing lamps 104 and 106 to continue blinking on and off as long as switch 92 is depressed. The same action will occur if conductors 72 and 74 are coupled across a diode of either polarity. Relay 98 will never energize, thus keeping the red lamp 106 on.

The chains of diodes 24 to which the unused contact points are connected provide a means for giving erroneous electrical readings between the inactive contact points so that someone trying to electrically determine the combination number through resistance measurements would not be able to do so. Resistance measurement between contact points will indicate either a small finite resistance representing the forward resistance of the diodes (about 200 ohms) or the unijunction or an open circuit indicative of the back resistance of one or more diodes or the unijunction. The forward resistance of the unijunction is E to B1, approximately 200 ohms, E to B2 - 600 ohms and B1 to B2 infinite To effectively decode the card would take a three element resistance check and it should be recalled that there are over one million possible combinations. With all of these measurements. it is clear that the investigator has determined nothing about the location of the proper contact points. A card containing 100 electrical contact points, of which three are active, provides one million possible combinations. Since the correct selection of the switches 47, 48 and 49 is also required, this multiplies the number of possible combinations by three. Four terminal semiconductor devices are also available which if used could raise the number of possible combinations to three hundred million.

FIGS. 6 through 8 set forth another embodiment of the invention of a more simplified form. Here, the operative semiconductor element comprises a NAND circuit 120 deposited upon the intermediate lamina 20. NAND circuit 120 has input terminals 121 and 123 which are coupled to unused contact points 122 and 124 respectively, and an output terminal 125 connected to contact point 126. In addition, the NAND circuit requires biasing, so the positive or B+ terminal is connected to contact point 128 and the negative or B- terminal is connected to contact point 130. because all cards using a NAND circuit will require this biasing, contact points 128 and 130 may preferably be additional to the contact points making up the encoding grid and may be situated along the edges of the card. Location of the biasing contacts within the encoding grid would of course increase the number of possible code combinations but may make false readings possible.

In FIG. 7, the switching apparatus previously described in connection with FIG. 5 schematically designated by the boxes 132, 133 and 134 inasmuch as the details thereof are the same. Switches 132 and 133 couple the inputs 122 and 124 through a push button switch 136 to a DC power supply 138 the output of which may be aslow as 1 VDC. The output terminal 126 is coupled through switches 134, through Zener diode 140, to indicator lamp 142 to the negative terminal 144 of supply 138. The negative supply terminal 144 couples directly to the card B- terminal 130. The positive supply terminal 146 of approximately 4 VDC is coupled through power switch 148 to the B+ terminal 128. power lamp 150 is coupled across switch 148 and negative supply terminal 144.

When switched on, lamp 150 preferably green is it. If the proper contact points the card are selected, depression of switch 136 will produce an output at terminal 126 of sufficient amplitude to cause Zener diode 140 to conduct, causing indicator lamp 142 to light, signifying a proper code selection. Zener diode having a Zener level of about 3 VDC will prevent improper input connections from causing lamp 142 to light since the input signals are only about 1 VDC.

FIG. 8 is the equivalent circuit of a typical NAND gate employing two transistors and appropriate biasing resistors. It will be readily apparent that resistance measurements made attempting to decode a card will not be fruitful because the overall diode matrix will produce similar results. With the NAND gate biasing points separate from the encoding matrix, it cannot be shorted to the output, so a false reading cannot occur in that way either.

FIGS. 9a and 9b set forth an improved embodiment of the present invention in that the circuitry therein shown provides the previously discussed feature of having a single unique code sequence for a card together with the provision of false code indications so that the card cannot be easily decoded but this embodiment permits the reduction of contact points on the card, and therefore on the card verifying unit to a very low number while still permitting an extremely large number of possible code combinations. The obvious advantage of reducing the number of contact points is that it will reduce the number of possible mechanical failures in reading or verifying cards. It is apparent that for a large number of contact points, it is possible that one of the important contacts may become dirty and fail to make the proper electrical contact with the verifier unit, or the spring loaded contacts of the verifier unit may, upon continued usage, suffer some mechanical defect which could result in wrongly failing to properly verify a good card. It is important that the card verifiers be dependable so that customers who use them and proprietors who have them can maintain a high degree of confidence in them.

The verification unit, the circuitry of which is shown in FIG. 9b may be constructed in virtually any configuration, it being necessary only that there be provided the number of contact points to be hereinafter discussed together with a number of momentary contact switches or push buttons and a pair of multi-positioned rotary switches. It will be seen from the ensuing discussion that the power supply requirement of this particular circuitry is extremely low so that the unit can be small, portable and self contained. The verification unit consists of 14 contact points generally designated in FIG. 9b by the numeral 200 and these contact points are indexed by the digits "0" through "9," letters "A" and "B" and signs "-" and "+." Each of the contact points 200 is coupled to one terminal 202 of momentary push button switches 204. A first rotary switch 206 has a wiper arm 208 and a plurality of contacts 210. A second rotary switch 212 is similarly provided with a wipe arm 214 and a plurality of contacts 216. The switch contacts 210 and 216 have, in addition to "off" positions to which no connections are made, connections indicated by the arrows and numered from "0" to "9" which are coupled in turn to the terminals 202 of the push button switches 204 numbered "0" through "9" and "A" and "B" so that contacts 210 and 216 are coupled in parallel to the correspondingly numbered push button switches, such as one-one, two-two, etc. The exception to the foregoing manner of connection is that one of the contacts 210a, which may be any of the numbered contacts 210 is coupled through conductor 218 to terminal 202aof push button switch 204a, which is in turn also coupled to the contact designated by the letter "A." Similarly, one of the contacts 216b of rotary switch 212 is coupled through conductor 220 to terminal 202b of push button switch 204b, that terminal also being coupled to the contact indexed with the letter "B."

A power switch 222 has one contact coupled to a source of positive DC voltage, herein designated as the B+ terminal 224 and, for example, the value of the B+ voltage is indicated as 10.5 volts DC. The other terminal of switch 222 is coupled to ground terminal 226. All of the push button switches 204 have their other terminals tied to a common bus line 228 which in turn is coupled to conductor 230 to the base electrode 232b of transistor 232. The collector 232c is coupled through an appropriate biasing resistor 234 to the B+ line 235. The emitter 232e is likewise coupled to the B+line 235 through biasing resistor 236, as is the base electrode 232b coupled through resistor 238. The emitter 232e is similarly coupled through resistor 240 to conductor 242 which is connected to the wiper 214 of switch 212. The wiper 214 is also coupled through a conductor 244 to the grounding terminal 226 of switch 222. The circuit also includes a capacitor 246 coupled between base electrode 232b and ground conductor 242.

The emitter 248e of transistor 248 is connected directly to the B+ line 235, the collector electrode 248c is coupled to the wiper 208 of rotary switch 206. Thus, power is supplied to the circuit upon the closure of switch 222 so that positive potential is applied through line 235 to transistor 232 and 248, a common ground for the circuit being coupled through switch contacts 226 to the wiper of switch 212, and in the configuration shown in FIG. 9b,ground will be supplied through conductor 220 to the contact point "B" coupled to push button switch 202b. When power is applied to the circuit, the base of transistor 232 goes positive and supplies approximately 11/2 volts on the bus line 228 to all of the switches 204. The collector of transistor 248 also goes positive supplying plus 10.5 volts to the wiper 208 and through conductor 218 to the contact terminal 202a. Thus, in the configuration of the circuit shown in FIG. 9b, the unit provides a11/2 volt trigger signal to all of the 14 contacts; and, through the selector switches 206, 212, anode voltage of plus 10.5 volts to any one of the contacts, and ground potential to any other one of the contacts. The indicia herein given to the various contacts are for the purpose of explanation and it is equally possible that other numerical systems or alpha-numerical systems may be adopted for the contacts other than the "+" and "-" or the other indices herein indicated.

Turning now to FIG. 9a, there is shown a plurality of silicon controlled rectifiers (SCR), there being 14 in number. Of those 14 SCR's, six are employed for the purpose of providing a false code signal, seven are employed to establish a six-digit code and a final SCR is used to control the function of an output indicator. SCR's 250, 252, 254, 256, 258 and 260 each have their gate electrodes connected directly to the contact points on the card herein designated by the index digits "1," "4," "6," "5," "7" and "+" respectively. These gate electrodes are likewise coupled through resistors 251, 253, 255, 257, 259, 261 to the card common ground bus 262 which is in turn coupled to contact point 264 indexed "B." The anodes of SCR's 250-260 are all coupled in parallel and connected to B+ conductor 266, which is in turn coupled to contact point 268 herein designated "A." The cathodes of SCR's 250-260 are coupled in parallel and connected to conductor 270. SCR's 272, 274 and 276 are coupled in series with the anode of SCR 272 coupled to B+ line 266. The gate electrodes of SCR's 272, 274 and 276 are connected directly to contact points on the card herein designated by the digits "2", "-" and "8". These gate electrodes are likewise coupled through resistors 273, 275, 277 respectively to ground bus 278 which is in turn coupled to the other ground bus 262. Resistors 280, 281 and 282 are coupled between the cathodes of SCR's 272, 274 and 276 respectively and ground, to keep each SCR conducting after removal of its respective trigger signal until the next successive SCR is made conductive.

Another SCR 282 has its anode coupled to B+ line 266 and its cathode coupled in series with SCR's 284, 286 and 288. The gate electrode of SCR 282 is coupled through a resistor 290 to the cathode of SCR 276. The gate electrodes of SCR's 284, 286 and 288 are connected directly to contact points on the card herein given the index digits "3," "9" and "0". As with SCR 272, SCR's 284, 286 and 288 are provided with resistors coupled between the gate electrodes and ground and between their cathodes and ground, with the exception SCR 288 the cathode of which is coupled to one terminal of a light emitting diode 290 the other terminal of which is coupled through resistor 292 to ground. An additional SCR 294 is connected across the light emitting diode 290, with its anode coupled to the cathode of SCR 288, and the cathode of SCR 294 coupled to the junction between the diode 290 and resistor 292. The gate electrode of SCR 294 is coupled through resistor 296 to conductor 270 and through resistor 298 to ground.

The index digits mentioned herein as assigned to the contact points on the card are given for illustrative purposes only, it being understood that the indexing of the card contacts may be done so as to provide any combination of digits. Here, the first two digits of the combination are determined by the switches 206 and 212 and the positions of those switches which provide the utputs to contacts "A" and "B." With reference to FIG. 9b, it will be indicated that the positions of those two rotary switches would correspond to index digits "5" and "3" for letters "A" and "B" respectively. In this manner, proper connection of those terminals to contacts "A" and "B" will provide appropriate B+ and ground terminals to contacts 268 and 264 on the card. The third, fourth and fifth digits in the code will be represented by index digits "2", "-" and "8" and the remaining digits in the code number will be determined by the connections of the gate electrodes of SCR's 284, 286 and 288, here shown to be assigned the digits "3," "9" and "0." Thus, the combination of the card shown in the drawings is AB2-8390.

When the proper combination of the card is known, and the card is inserted in the verification unit until all contacts are properly made, the rotary switches 206 and 212 are moved to the proper positions, here positions "A" and "B" or "5" and "3" respectively. Power switch 222 is closed and the verification unit will thereby provide a positive anode voltage at contact "A" and a ground connection to contact "B," plus an SCR trigger voltage available at each push button switch through common bus 228. Anode voltage is provided to all of the SCR's 250-260, 272 and 283. The trigger voltage is available to each gate of each SCR through the contacts except of course the gates to SCR's 283 and 294. The next six digits of the combination are introduced into the card by pushing the proper push buttons in the correct sequence, in this case "2-8390." When push button 2 is depressed, a trigger voltage is applied to the gate of SCR 272 causing current to flow through the SCR and through the cathode resistor 280 to ground so that SCR 272 is turned on and maintained in that condition, at the same time supplying anode voltage to SCR 274. When the dash or minus button is depressed, SCR 274 will be turned on in a similar manner supplying anode voltage to SCR 276 which is in turn turned on by depression of push button corresponding to that number. The resistors coupled between the gates of the SCR's to ground desensitize the gates so that they will not trigger the SCR's in the event there is a stray noise. When SCR 276 is turned on it turns on automatically SCR 283 thereby enabling SCR 284 and supplies to the anode of SCR 284 the full anode voltage. It has been found that due to junction voltage drops occuring between the anode and cathode of an SCR, where SCRs are cascaded, the voltage drop is too great if more than three SCR's are coupled in series. Accordingly the series combination of SCR 272, 274 and 276 is provided to trigger the intermediate SCR 283 which thereby supplies full anode voltage to the next successive series of three SCR's. Then, when push buttons "3," "9" and "0" are depressed, each of the corresponding SCR's 284, 286 and 288 will fire, each enabling the following SCR to fire in the same manner. When the "0" push button is depressed, power is supplied to the light emitting diode 290 which lights to signify that the correct combination has been introduced in the correct sequence, thereby verifying that the owner of the card has properly identified himself.

If the proper combination is not known, particularly if the proper positions for rotary switches 206 and 212 are not known, proper bias can never be supplied to the card circuit. Even assuming that those proper positions are known, only SCR 272 can be turned on even if all of the push buttons are depressed. Assuming that SCR 272 was turned on, then if push button "9," for example, is depressed, SCR 286 would have no anode voltage and cannot be fired. Furthermore, the trigger voltage supplied to the gate of SCR 286 will be coupled through the gate resistor to ground and would cause SCR 272 to turn off. Any other wrong sequence will have the same effect. The reason that the circuit works in the correct sequence is that the SCR's, when they have anode voltage, will turn on fast enough to keep the reviously fired portion of the circuit from resetting. If any push button other than those numbers which comprise the correct combination or code sequence are depressed, the corresponding SCR will fire since SCR 250, for example, will always have anode voltage and if button "1" is depressed SCR 250 will indeed fire. The output of SCR's 250-260, i.e., their cathodes, are all coupled through line 270, through resistor 296 to the gate of SCR 294. If any outputs are obtained from SCR's 250-260 they will trigger SCR 294 on so that current will be shunted across the diode 290 thereby preventing it from turning on. Therefore, even if the proper code sequence was used, pushing any one button corresponding to a number which is not an element of the sequence, the LED will not light since SCR 294 would be enabled, there being an available anode voltage to it as soon as an output is obtained from SCR 288.

It is necessary that the first SCR of the proper code sequence be immediately enabled and for that reason the anode of 272 is connected directly to the B+ conductor 266. It would be possible to determine electrically which is the first digit of the code by determining which SCR turns on first, and then the next SCR and so on. But, SCR's 250-260 are provided to give an additional set of SCR's which can be turned on at any time to further confuse the investigator. These six SCR's will effectively hide which SCR out of the group 250-260 and 272 is the correct first digit since any of them can be turned on first. It will also be noted that any of the six SCR's 250-260 can be turned on one after the other and by coupling those SCR's in parallel with essentially no load and all having anode voltage it has been found that the SCR's will interact between themselves in random fashion based upon the inherent internal characteristics of each SCR, its relative location within the circuit, the number of other SCR's that have been turned on, etc. In other words, it is possible that all six of the SCR's can be turned on, but in most cases several will be turned on and then when a button is depressed to turn on an additional one, it may reset one or all of the others in a random fashion which makes an electrical investigation of the circuit extremely confusing.

It will thus be seen that the present invention has provided a greatly improved method of credit card verification and which will substantially reduce credit card misuse. While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those persons skilled in the art that changes and modifications might be made and it is, therefore, contemplated that such changes and modifications are within the scope of this invention.