GB2186732A

GB2186732A - Improvements in encoding magnetic cards

Info

Publication number: GB2186732A
Application number: GB08600875A
Authority: GB
Inventors: Toshihiko Yamashita
Original assignee: UNIQEY
Current assignee: UNIQEY
Priority date: 1986-01-15
Filing date: 1986-01-15
Publication date: 1987-08-19
Also published as: GB2186732B; GB8600875D0

Abstract

A system and apparatus for encoding magnetic information on a magnetisable substrate where the substrate is liable to be moved erratically, e.g. manually, past a magnetic head. Two parallel tracks are provided on the substrate and the first is encoded with binary information conventionally with shorter spaces between change of field representing one binary digit and longer spaces representing the other digit. The other track is encoded using changes in field on the first track as a timing reference such that any change of field on the second track substantially coincides with a change of field on the first track and one digit of the binary pair is represented by no change in field as the field changes on the first track whilst the other binary digit is represented by a change of field coincidentally with a change of field on the first track. The system and apparatus are eminently suited for use in parking meters where a power source to drive a card consistently past a reading head is not available.

Description

SPECIFICATION Improvements in encoding magnetic cards This invention relates to the encoding of magnetic cards or other magnetic substrates and to the associated card writers.

Cards which have a strip of magnetic material on them on which information can be encoded magnetically by a card reading and writing head are very well known. They are widely used in electronic banking and to control entry to and exit from public transport systems. In circumstances such as these, however, the card writer is generally a relatively complex piece of machinery and is generally very expensive. Also it is usually housed indoors so that it is well protected from the environment. Further, this usually uses a plentiful supply of electricity to drive some form of electric motor which advances the card past the read-write head at a substantially constant speed so that good writing can be achieved.

It would be very desirable to adapt this type of technology to simple situations like parking meters. Thus, a user could get a stored value ticket from a central location and then insert that into a parking meter where he parks his car and the parking meter would then automatically check the ticket, extract the appropriate time by reading the remaining time on the stored value ticket and re-writing with the reduced remaining value. Parking meters, however, do not have a ready supply of electricity for driving a motor and also it would not be practical to use a very expensive card writer in such circumstances because of the numerous parking meters which exist.

It is therefore an object of the invention to provide a system which is much simpler and whereby the user can manually insert and withdraw the ticket so that only a relatively small power supply, e.g. as obtainable from a battery pack, is necessary to drive the electronics associated with the read-write head.

According to the invention, there is provided a system for encoding magnetic information on a magnetic substrate in which the substrate has two parallel tracks, on the first track, binary information is encoded conventionally with shorter spaces between changes of field representing one of the two binary digits and longer spaces representing the other of the two binary digits, and the second track is encoded with binary information in such a way that a change of field substantially coincides with a change of field in the first track and one digit of the binary pair is represented by no change in field as the field changes on the first track whilst the other binary digit is represented by a change of field at the same time as a change of field on the first track.

By following such a system, one can provide å relatively simple read-write head and writing means for encoding the information.

Thus, electric means for driving the card are not necessary and the card can be advanced and retracted manually. Obviously this will risk having one user moving the card faster past the read-write head than another user. In the system according to the invention, however, this does not matter because the absolute timing of changes of field on the track are not relevant but only the relative timing of changes of field as between one track and the other. It is therefore possible to use this system in simple circumstances such as the example of the parking meter noted above where only a relatively low amount of battery power is available which would be more than sufficient to operate the read-write head but would not be sufficient to operate, say, an electrical drive motor for advancing the card.

In, say, the parking meter example noted above, the first track can be encoded with binary information representing the time and place of purchase of the stored value ticket.

Simultaneously with purchase, the second track can be encoded with the time of the ticket. Then as the ticket is used the second track is read to determine the amount of time remaining, the allowed parking time is deducted and the second track re-written according to the then remaining stored time.

The invention will now be illustrated, with reference with the accompanying drawings, which show a number of timing graphs explaining the operation of the invention.

A card carrying a magnetic strip is a well known item of commerce and so will not itself be described. Additionally, the read-write head and the associated electronics will not be described in detail since they are also well known.

Referring to timing graph A, this shows plotted against distance the magetic field on track 1 of the magnetic strip. It has been assumed that the binary information to be encoded is 00000000000000000 10 1000 11111 10 100 1 10. This is represented in entirely conventional fashion by fields which appear above the longitudinal axis as magnetic north and fields below the longitudinal axis as magnetic south. The actual question of whether a field is north or south is irrelevant as to the question of whether the field represents a binary 0 or a binary 1. As is entirely conventional, a binary 0 is represented by a short field which changes from a north to a south or a south to a north after one unit of length whilst a binary 1 is represented by a longer field of substantially twice the length.

Thus the change can be from a north to a south or a south to a north but provided the change occurs after a short length that represents a binary 0 and after a long length represents a binary 1.

Graph B shows plotted against time the electrical output from a magnetic read-head.

At each change of field, a pulse arises and it can be seen that again it is the spacing between the pulses which determines whether the pulse represents a binary 0 or a binary 1.

Thus, a short space represents a binary 0 and a longer space a binary 1. As is conventional that electrical signal is rectified and amplified to give pulses as shown in Graph C and the electronics associated with the system will recognise this as the binary encoded information O00000000000000001010001 1111 10100110 in the example shown.

The magnetic encoded information on this track 1 is inserted at a central accurate location where the magnetic write head will be electrically driven and so the spacings and timings of the binary 0 and 1 can be accurately determined. In a card according to the invention, this first track is not thereafter altered by the read-write head of the parking meter but in effect this track is used as a timing pulse clock for the second track. This first track however does contain basic information relating to the card and for example the encoded information can represent the centralised location where the card was purchased, the date of purchase, its initial value and so on.

At the time of purchase of the card, the second track is also encoded with information relating to the amount of time remaining in the ticket and the second track will of course conventionally be positioned on the same magnetic strip on the card alongside the first track and the encoding of two tracks on a magnetic strip is entirely conventional and analogous, for example, to the method of recording stereo signals on audio magnetic tapes.

When the user inserts the ticket into a parking meter, it will be read in a manner described below and then when he thereafter removes the ticket, new information concerning the amount of the stored time will be encoded on the second track. We will take for example the situation where the information to be encoded is the binary number 000011010100111100.

As the user withdraws the ticket from the machine, this information has to be encoded but of course the user may not withdraw the ticket at a uniform speed as would an electric motor and equally one user may withdraw a ticket at a different rate from another user.

Therefore, in accordance with the invention, the first track is used as a timing pulse clock during the writing of the amended information on the second track.

To achieve this, the electronics associated with the system writes only a pulse when a binary 1 is to be recorded and no electronic pulse when a binary 0 is to be recorded. Additionally, the binary number to be recorded on the second track is synchronized with the pulses read from the first track. Turning to Graph D, it can be seen that as the card is withdrawn, the first track will provide from the read head a series of pulses in the manner as has been described above in connection with Graphs A to C. The pulses will be spaced apart at varying distances depending upon whether they are to represent a binary 0 or a binary 1. As far as writing in the second track is concerned, it is irrelevant whether these pulses from track 1 are binary 0 or binary 1 and purely important to consider a pulse which represents a change of field.On receipt of the first pulse, the second track is either written, i.e. the field changed, if a binary 1 is to be written and so a pulse is provided or no pulse is provided for the second track if a binary 0 is to be written. This continues and it can be seen that for the first four pulses, i.e. O to 3 received from the track 1, no corresponding pulse is provided for writing on track 2. However, at the fifth pulse, i.e. number 4 where a binary 1 is to be written, then a pulse is provided and the field of the write head for track 2 changes polarily. At the sixth pulse, i.e. number 5, another binary 1 is to be written and so the field is changed again. This continues as the card is withdrawn.It should be emphasized again that the spacing of the pulses 0 to 18 on track 1 are immaterial and it is only when a binary 1 is to be written that a pulse and so a corresponding field change is provided for track 2.

If one follows along Graph E, one can see the resulting field which will be provided on track 2, using the same format as in Figure A for track 1, and the number which has been written is indeed the number 000011010100111100.

When the card is next used and inserted into a parking meter, the reverse occurs.

Again, track 1 is used solely as a timing pulse clock to enable accurate readings of binary encoded information to be obtained from track 2.

No detailed explanation has been given of the actual electronics associated with the reading and writing of the heads and tracks since this is entirely conventional and no further explanation is believed required. However, it can be seen from this explanation how on track 2 magnetically encoded information can be provided in a very simple fashion where there can be accurate discrimination between binary 1s and binary Os without having at the same time to have an accurate absolute timer or, for that matter, an accurate absolute distance between changes of fields on track 2 to represent binary Os and binary 1s as is conventional and necessary for track 1 where track 1 is of course written centrally by an accurate machine.

Claims

1. A system for encoding information on a magnetisable substrate, in which the substrate has two parallel tracks, on the first track, binary information is encoded with shorter spaces between changes of field representing one of the two binary digits and longer spaces representing the other of the two binary digits, and the second track is encoded with binary information in such a way that any change of field substantially coincides with a change of field in the first track and one digit of the binary pair is represented by no change in field on the second track as the field changes on the first track whilst the other binary digit is represented by a change of field on the second track coincidentally with a change of field on the first track.

2. A system as claimed in Claim 1 in which the magnetic substrate is provided as a stripe of magnetisable material on a flat card.

3. A system as claimed in either preceding claim as applied to parking meters, in which the magnetic substrate is provided on a ticket, the two tracks are encoded with information at a central location, and a parking meter itself has a read/write head capable of reading information from the second track when the magnetic substrate is manually moved past the head and if appropriate rewriting encoded information on the second track after deduction of appropriate parking charges.

4. A system as claimed in Claim 3 in which the first track is encoded at the central location with information representing the time and place of purchase and the second track is encoded with information relating to the value of the ticket, the read/write head in a parking meter reading that information as the ticket is inserted into a meter and writing on the second track information as to the remaining value, if any, of the ticket after deduction of parking charges as the ticket is withdrawn from the meter.

5. A system for encoding information on a magnetisable substrate substantially as herein described with reference to the accompanying drawings.

6. A card carrying a magnetisable substrate which has been encoded by a system as claimed in any preceding claim.

7. Apparatus for encoding information on a magnetisable substrate which has a magnetic head capable of writing two parallel tracks on the substrate, on the first track binary information being encoded with shorter spaces between changes of field representing one of the two binary digits and longer spaces representing the other of the two binary digits, and on the second track binary information is encoded in such a way that any change of field substantially coincides with a change of field in the first track and one digit of the binary pair is represented by no change in field on the second track as the field changes on the first track whilst the other binary digit is represented by a change of field on the second track coincidentally with a change of field on the first track.

8. Apparatus for reading and encoding information on a magnetisable substrate which has a magnetic head capable of reading magnetically encoded information from two parallel tracks on the substrate, the first track having been encoded with binary information represented by changes in the magnetic field of that track and the second track having been encoded with binary information in such a way that any change of field substantially coincides with a change of field on the first track and one digit of the binary pair is represented by no change in field on the second track as the field changes on the first track whilst the other binary digit is represented by a change of field on the second track coincidentally with a change of field on the first track, electronic means for receiving signals from the head and determining the binary information encoded on the second track in a first pass in one direction and sending signals to the head to rewrite the second track in a second pass in the opposite direction in such a manner that any change of field substantially coincides with a change of field of the first track and one digit of the binary pair is represented by no change in field on the second track as the field changes on the first track whilst the other binary digit is represented by a change of field on the second track coincidentally with a change of field on the first track.