Patent 4550221 Issued on October 29, 1985. Estimated Expiration Date: October 7, 2003. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
A touch sensitive control device translates touch location into output signals. The device includes a substrate which supports first and second interleaved, closely spaced, nonoverlapping arrays of conductive plates. The plates are aligned in rows and columns so that edges of each plate of one array are proximate to but spaced from the edges of plates of the other array. The plates of each column of the first array are connected together and the plates of each row of the second array are connected together. An insulating layer overlies the first and second arrays so that when the outer surface of the insulating layer is touched, the capacitance of at least one of the columns of plates of the first array and the rows of plates of the second array underlying the insulating layer at the location being touched exhibits a change of capacitance with respect to ambient ground. The columns of the first array and the rows of the second array are periodically connected on a multiplexed basis to a capacitance measuring circuit. Based upon the measured capacitance of each column of the first array and row of the second array, the microcomputer produces output signals which represent the coordinates of the location being touched. These output signals can be used, for example, to control the position of a cursor on a display screen or to make selected function commands.
Other References
IBM Technical Disclosure Bulletin, "Generation of X and Y Coordinate Information, A. Bezgin, vol. 1, No. 6, pp. 13 and 14, Apr. 1959
James K. Johnson, Datamation, "Touching Data"
"New Products, Continued . . . Pheripherals . . . Touch Sensor", Creative Computing, Jul. 1983