US 5,471,040 AGranted

Capacitive data card system

OwnerGeorge Mayinventor

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Abstract

A data storage and retrieval system is disclosed which includes an interface module and a data card. Both the interface module and card include a plurality of primary and secondary electrodes having the same pattern. The data card further includes a plurality of fuses extending between each of the primary and secondary electrodes. When the fuse is intact, it will conduct current. When the fuse is blown, the resistance will substantially increase. The state of the resistance of the fuse is used to represent bits of data. In operation, the card is juxtaposed with respect to the interface module so that the respective electrodes can be capacitively coupled. In order to read the data on the card, a an output having a predetermined voltage and frequency is applied to the electrodes. The level of AC current passing through the fuse is measured and the result is used to derive the state of the fuse. When information is to be written onto the card, the voltage level and the oscillating frequency are increased causing the current flow in the electrodes to increase thereby blowing the fuse. The hardware is low in cost, requires low power to operate and provides a write once/read many memory (WORM) in the form of a disposable data card.

Claims33

Dependent claims

A data storage and information retrieval system comprising:

an interface module, said interface module including;
a plurality of individually addressable primary interface electrodes;
at least one secondary interface electrode, said interface electrodes being arranged in a predetermined pattern;
a data card having changeable bits of information, said card including;
a plurality of primary card electrodes;
at least one secondary card electrode, said card electrodes being arranged in a predetermined pattern selected so that when the card is placed next to the interface module, the interface electrodes will be in register with the card electrodes;
and
a bridge formed between each primary card electrode and the secondary card electrode, said bridge having a resistance which can be either a first level or a second level, with the level of resistance being representative of a bit of information;
and
means located in said interface module for generating an alternating current output having two different voltage profiles, said output being applied to selectable interface electrodes in a manner to capacitively couple a current to the opposing card electrodes and wherein the level of resistance of a particular bridge on said card can be evaluated by measuring the amount of current which passes through the bridge when an output having a first voltage profile is applied to the interface electrodes and wherein the resistance of said bridge can be changed by applying an output having a second voltage profile to said interface electrodes and wherein the frequency of said second voltage profile is greater than the frequency of the first voltage profile.

7 more elements

A data storage and information retrieval system comprising:

an interface module, said interface module including;
a plurality of individually addressable primary interface electrodes;
at least one secondary interface electrode, said interface electrodes being arranged in a predetermined pattern;
a data card having changeable bits of information, said card including;
a plurality of primary card electrodes;
at least one secondary card electrode, said card electrodes being arranged in a predetermined pattern selected so that when the card is placed next to the interface module, the interface electrodes will be in register with the card electrodes;
and
a bridge formed between each primary card electrode and the secondary card electrode, said bridge having a resistance which can be either a first level or a second level, with the level of resistance being representative of a bit of information;
and
means located in said interface module for generating an output having two different voltage profiles, said output being applied to selectable interface electrodes in a manner to capacitively couple a current to the opposing card electrodes and wherein the level of resistance of a particular bridge on said card can be evaluated by measuring the amount of current which passes through the bridge when an output having a first voltage profile is applied to the interface electrodes and wherein the resistance of said bridge can be changed by applying an output having a second voltage profile to said interface electrodes and wherein said first voltage profile is defined by applying an alternating current to one of said interface electrodes while holding the other interface electrode at ground and wherein said second voltage profile is defined by applying an alternating current to both said interface electrodes, in opposite phase, so that the voltage difference across the interface electrodes generated when the second voltage profile is applied is twice the voltage difference generated when the first voltage profile is applied.

7 more elements

Dependencies are inferred from the claim text.