Electrographic system and method

Claim 1

An electrographic system comprising: an electrically insulative substrate; a resistive layer exhibiting substantially uniform electrical resistance supported upon said insulative substrate and having an operational region extending in an x-coordinate sense between first and second parallel, spaced apart border regions, and extending in a y-coordinate sense between third and fourth parallel, spaced-apart border regions; stylus means for generating localized electromagnetic radiation from an a.c. source to effect the propagation thereof toward said resistive layer from positions selectively spaced therefrom to effect interaction therewith; first, discrete, spaced-apart contacts electrically coupled with said resistive layer at said first border region; second, discrete, spaced-apart contacts electrically coupled with said resistive layer at said second border region; third, discrete, spaced apart contacts electrically coupled with said resistive layer at said third border region; fourth discrete, spaced-apart contacts electrically coupled with said resistive layer at said fourth border region; signal treating means including voltage converter means having an input for receiving electrical signals generated by said stylus means interaction and conveyed thereto for providing an alternating voltage output corresponding therewith, means responsive to said alternating voltage output to derive a constant voltage output corresponding therewith and means responsive to said constant voltage outputs corresponding with electrical signals at said first and second border regions for deriving x-coordinate signals corresponding with the ratio of the difference of said constant voltage outputs corresponding with said first and second border regions divided by the sum thereof, and responsive to said constant voltage outputs corresponding with electrical signals at said first and fourth border regions for deriving y-coordinate signals corresponding with the ratio of the difference of said constant voltage outputs corresponding with said third and fourth border regions divided by the sum thereof; and analog switching means including first discrete low impedance switches, each coupled between a selected one of said first contacts and said signal treating means voltage converter means input and actuable to effect conveyance of said electrical signals thereto, second discrete low impedance switches, each coupled between a selected one of said second contacts and said signal treating means voltage converter means input and actuable to effect conveyance of said electrical signals thereto, third discrete low impedance switches, each coupled between a selected one of said third contacts and said signal treating means voltage converter means input and actuable to effect conveyance of said electrical signals thereto, fourth discrete low impedance switches, each coupled between a selected one of said fourth contacts and said signal treating means voltage converter means input and actuable to effect conveyance of said electrical signals thereto, said switching means effecting a mutual open circuit isolation of said third and fourth contacts when said first and second switches are actuated and effecting a mutual, open circuit isolation of said first and second contacts when said third and fourth switches are actuated.

Claim 8

The method for generating coordinate signals in conjunction with a surface comprising the steps of: providing a resistive surface of selected impedance value having an operational region extending in spaced apart x-coordinate sense between first and second spaced apart border regions having respective first and second spaced contacts thereon, and extending in a y-coordinate sense between third and fourth spaced apart border regions having respectivve third and fourth spaced apart contacts thereon; transmitting localized electromagnetic radiation of predetermined frequency from an a.c. source to effect the propagation thereof toward a select coordinate identifiable location upon said resistive surface from positions selectively spaced therefrom to effect interaction with said layer; providing first and second discrete low impedance switches coupled with respective said first and second contacts and actuable from off to on conditions to provide a low impedance transfer of radiation induced currents at said first and second border regions; providing third and fourth discrete low impedance switches coupled with respective said third and fourth contacts and actuable from on to off conditions to provide a low impedance transfer of radiation induced currents at said third and fourth border regions; actuating said first and second low impedance switches to an on condition while effecting a said third and fourth low impedance switches off condition to effect conveyance of said radiation induced currents from said first and second border regions; converting said radiation induced currents conveyed by said first and second low impedance switches into respective first and second alternating voltage signals; converting said first and second alternating voltage signals into respective first and second constant voltage levels proportional to said alternating voltage signal; and deriving x-coordinate signals as the ratio of the difference of said first and second constant voltage levels divided by the sum thereof.

Claim 9

The method for generating coordinate signals in conjunction with a surface comprising the steps of: providing a resistive surface of selected impedance value having an operational region extending in spaced apart x-coordinate sense between first and second spaced apart border regions having respective first and second spaced contacts thereon, and extending in a y-coordinate sense between third and fourth spaced apart border regions having respectivve third and fourth spaced apart contacts thereon; transmitting localized electromagnetic radiation of predetermined frequency from an a.c. source to effect the propagation thereof toward a select coordinate identifiable location upon said resistive surface from positions selectively spaced therefrom to effect interaction with said layer; providing first and second discrete low impedance switches coupled with respective said first and second contacts and actuable from off to on conditions to provide a low impedance transfer of radiation induced currents at said first and second border regions; providing third and fourth discrete low impedance switches coupled with respective said third and fourth contacts and actuable from on to off conditions to provide a low impedance transfer of radiation induced currents at said third and fourth border regions; actuating said first and second low impedance switches to an on condition while effecting a said third and fourth low impedance switches off condition to effect conveyance of said radiation induced currents from said first and second border regions; converting said radiation induced currents conveyed by said first and second low impedance switches into respective first and second alternating voltage signals; converting said first and second alternating voltage signals into respective first and second constant voltage levels proportional to said alternating voltage signal; and deriving x-coordinate signals as the ratio of the difference of said first and second constant voltage levels divided by the sum thereof.