GB2115349A - Debit card - Google Patents

Abstract

A debit card, e.g. for telephone call-making purposes, has its value indicated by a number of value-unit indicating patches or spots of a material which changes its state significantly in response to the application of a burst of light or heat. One such material which is normally translucent goes dark when thus irradiated. When the card is placed in - or adjacent to - the reader, the latter first checks for the presence of unchanged spots, and then when it finds such a spot it reverses its state. This detection followed by reversal indicates that the card is valid, and an output is sent to the associated equipment - e.g. a telephone exchange.

Description

SPECIFICATION Debit card This invention relates to debit cards, and especially to such cards on which the cancellation of unit values is possible without the need for the card to enter the card reader.

According to the invention, there is provided a debit card on which the value of the card is indicated by one or more value unitrepresenting patches of a material whose propeprties can be changed by the application to that material of a burst of light or heat, the arrangement being such that when the card is read and a said value unit is used up a burst of heat or light applied to the card changes the properties of a patch which represents the used-up value unit, and that the change of properties is such that the number of value units remaining available to the holder of the debit card can be readily detected.

A number of materials exist which are suitable for use in the value unit-representing patches, and these materials are herein referred to generically as photo-chromic. As an example it is assumed that the 3 M's type 383 imaging film is used; when heated above a critical temperature it abruptly changes from being clear to being black. As used for the unit-representing patches, the material is applied in one case as an array of dots which are normally invisible. The reader checks the absence of dark marks in an expected area, which indicates that the card is valid. it then irradiates a value-indicating spot, which causes blackening which is readily detectable by the machine. This indicates that the credit is good and the service is then given. in the present example where the debit card is for telephone service this would be call initiation or maintenance.

Unless a prospective forger has access to the material, forgery would be difficult. Thus merely scraping off a blackened spot would be insufficient since although the machine would respond to the first test, it would fail to blacken it when the irradiation took place.

Hence the tampered-with card would fail the second test. Either transmitted or reflected light heatvan be used, which enables the method to be used inside or outside the machine. A material with inverse properties, i.e. an opaque-transparent change, can also be used as it would be equally immune to forgery or revalidation. Materials which change colour are also usable since the machine can be easily made to detect such a change, e.g. from yellow to blue, as in the material referred to in U.S. Patent No.

4104515 (Thornberg and Lahr). Some such materials are opaque, in which case only reflective methods could be used, but these are well suited to external reading/cancellation.

Other photo-chromic materials which are usable suffer changes in birefringency when illuminated, examples including some propylenes and polyethylenes. Another effect obtainable in some cases is volume change due to gas being generated and retained which, by lifting a film can produce a colour change.

Another material resembles "carborless" paper as it is coated with encapsulated substances which are released when heated to stain the paper.

In some cases, dependent on the material used, the verifications and cancellation may use forms of radiation other than visible light, e.g. ultra-violet and infra-red or possibly even radio frequencies. Some care may be needed in using some forms of radiation to avoid health hazards, but this can be achieved by ensuring that the radiation is only generated when the card is actually in its reading position. In that case the card itseif would act as a screen for the user.

We have mentioned above the use of materials whose polarisation properties change, i.e. birefringency when subjected to heat or light. Such a change is not of itself detectable by the human eye, and to make it so detectable it is necessary to make each patch a sandwich of different polarising materials only part of which is sensitive to heat or light. This converts the spatial and phrase changes caused by birefringency into amplitude changes, so that the visible change is "light" to "dark". This is in essence a transmissive method, so is best suited to internal reading/cancellation, but external methods can be used.

The use of cards embodying the invention will now be described with reference to the accompanying drawings, in which Fig. 1 indicates schematically the general principles of card readers for debit cards embodying the invention, while Fig. 2a and 2b show the principles of two reading/cancelling methods.

In view of the similarities between the various photo-chromic materials, the same basic block diagram, Fig. 1, serves for several variants of each method. These methods may not be equally attractive, and at present it is felt that the "shape or size" method is the least attractive.

The general principle with all forms of material contemplated is important since it permits both reading and cancellation "at a dis tance", i.e. outside a reader. Fig. 1 distinguishes between those elements which would always be found in any variant, and those which would either be appropriate to only certain variants, or would be optional these being shown in dashed lines. Important differences concern the relationship between validation and valuation. Thus in some cases, the method of valuation, i.e. the provision of the "units", is so secure that the mere presence of a "value" marking establishes the card's validity. At the other extreme, we may have rather insecure valuation and cancellation techniques: to these it would be advantageous to add a separate and more secure valida- tion" means.Between these two extremes we have other combinations of mutually supportive valuation and validation processes.

It is also necessary to choose between multiple and single reading/cancellation heads.

The first uses one head per unit, which allows "static" operation, i.e. neither the card nor reader is physically moved. Hence all units can be read simultaneously, which is a useful feature for an "external" reader. However, it may be uneconomic if the heads are expensive. With a single head, reader, one reading/cancellation head is physically stepped along the card and reads each unit in turn.

Either the card or the head may be moved if reading/cancellation is "internal": for "external" reading/cancellation, the card is fixed and the head moved. The movement is conventionally mechanical although the movements could be quite small, e.g. the tilting of small mirrors to allow a fixed head to see each of a fixed card's units in turn. It is also possible to use a combination of fixed mirrors and fixed "light switches" (e.g. liquid crystals) to attain the same result without mechanical movement.

Reverting to the multiple head method, some techniques require the coded, unit defining, patches to be so irradiated that they can be "seen" by the detector. In such cases, it may be possible to use a single source to irradiate all the units, plus a detector head per unit (or vice versa).

In all methods, the reader checks that at least one valid unit remains on the card before giving the go-ahead to the following circuits, which in the present case where the debit card is for telephone call making, is the telephone exchange circuitry. However, it is also possible for the reader to check the presence of other valid units, and present this information to both the user and the system which the reader controls. This early warning of a card's expiry can be useful operationally, but is more easily provided by some reading techniques than others.

In view of the detailed discussion above, and of the annotations on Fig. 1, it is felt that no detailed description of Fig. 1 is needed.

However, the reference to validation area indicates that validation of the card may depend at least in part on the detection of some special mark or its equivalent in the debit card. This could be done with the same material as used for the value-representing patches, but without alteration thereof. As indicated the reader for this purpose may be combined with the unit reader.

With the various materials contemplated, the card reading and cancellation process is much the same. The mark signifying a unit is first examined: usually this can only be done by irradiating it with something to which the mark responds (e.g. by exposing it to another form of radiation) so as to alter it irreversibly in a way readily detectable by the machine and, preferably, by the human eye as well. An idealised example shown in Fig. 2a, consists of a patch of transparent material which defines a unit and is illuminated by a light source S. A photo-cell D on the opposite side of the card from the light source S detects that light is being transmitted by the patch, a condition to be expected of a valid unit.The patch is now heated, e.g. by an infra red beam, and as it is photosensitive it darkens: this change is also detected by the photo-cell and is the condition expected of a validity cancelled unit.

A similar effect can be achieved using reflected or scattered light, Fig. 2b, allowing single-sided operation, which is especially desirable when the card is read outside the reader. Clearly similar methods can be based on other changes of optical properties (e.g. of colour or polarisation).

It is useful to be able to provide a card with an indication of the value left, in a manner legible to the user. This can readily be achieved by adding to the basic reading/cancellation machine a device which makes a mark on the card each time it is used. Such a mark can be made by conventional printing, by the used of thermally-sensitive or light sensitive material or by clipping or punching.

It would be initiated by the same action that cancels the "invisible" unit stored on the card in a hologram, semiconductor memory or magnetic pattern, depending on the type of card. The only slight complication resides in the need to separate, physically, the humanvisible markings. In fact the card-reader can determine the identity or "serial number" of the stored unit which has to be cancelled and so can arrange for the corresponding visible mark to be made in a specific place, either by moving the card relative to a single marking head, or by providing a fixed marking head for each unit. We can add complications ad lib. For example, we could print the date of use or the number of the machine in which it was used. An exhausted card or a detected forgery could be marked "CANCELLED" or seriously mutilated.

The fact that the credit cards can be read from outside the reader is advantageous in that it obviates the need for a card-receiving slot. This greatly reduces the card reader's vulnerability to vandals.

Claims (6)

1. A debit card on which the value of the card is indicated by one or more value unit representing patches of a material whose pro perties can be changed by the application to that material of a burst of light or heat, the arrangement being such that when the card is read and a said value unit is used up a burst of heat or light applied to the card changes the properties of a patch which represents the used-up value unit, and that the change of properties is such that the number of value units remaining available to the holder of the debit card can be readily detected.

2. A debit card as claimed in claim 1, and in which, when a card is applied to a reader, the reading takes place in two stages one of which involves checking that the card has at least one value indicating unit patch while the other of which involves checking that the said patch has had its characteristics changed.

3. A debit card as claimed in claim 1 or 2, and, in which said change of proportion is suich that the number of value units remaining available to the holder is readily detectable by the holder as well as by an associated card reader.

4. A debit card substantially as hereinbefore described.

5. A debit card reader for use with debit cards as claimed in claim 1, 2, 3 or 4 in which the card is placed in the reader via a slot so that light is applied to the card, which light passes through a said patch to check that at least one unaltered patch remains, in which after said check the said burst of light or heat is applied to the card to effect said change of the patch, and in which after both said operations have been effected it is assumed that the card is valid.

CLAIMS (1 Jul 1982)

6. Apparatus for the cashless payment for goods or services, which apparatus includes debit cards and a card reader, wherein the value of a said debit card is indicated by one or more value unit-indicating patches of a material whose properties can be changed by the application to the material of a burst of light of heat, wherein each said patch is on the surface of the debit card and is backed by a reflective surface, wherein when a said card is to be read it is placed in operÉiye relation with the reader which initially c6eí,Cs that the card has at least one valid value!íS'dicating patch, wherein the detection and' reading of the patches is effected reflectively by detection means, wherein if a said valid patch is present the holder of the card is afforded credit and the reader, when a value unit has been used up, applies a said burst of light or heat to a patch appropriate to a said used-up unit, and wherein the application of a said burst of light or heat causes a detectable change of the properties of that patch, such that the number of value units remaining available to the holder of the debit card is readily detectable.