Telegraphy – Systems – Position coordinate determination for writing
Patent
1986-08-26
1987-10-06
Schreyer, Stafford D.
Telegraphy
Systems
Position coordinate determination for writing
G08C 2100
Patent
active
046984607
ABSTRACT:
A touch panel has panel scanning signals selectively applied to the four sides of a touch sensing surface of the panel so as to establish alternating current voltage gradients in desired directions across the touch sensing surface. When the panel is touched, touch signals or currents result and are utilized by a touch location circuit in determining the location of touch. The impedance touch current resulting from a user's touch may also be determined and used. The touch panel circuit automatically compensates for changes in impedance touch current, such as result when users touch the panel with ungloved and gloved fingers. An analog multiplier is included in the touch location circuit to improve noise rejection. Auto nulling and automatic frequency adjustment is included in the touch panel device, together with overcurrent protection circuitry.
REFERENCES:
patent: 3497617 (1970-02-01), Ellis
patent: 4293734 (1981-10-01), Pepper
Krein Philip T.
Meadows Robert D.
Murdock Bruce
Teichmer Daniel G.
Petersen David P.
Schreyer Stafford D.
Tektronix Inc.
Winkelman John D.
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