Importance

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Abstract

A multi-electrode capacitive position sensor functions as part of a computer pointing device that can be integrated with the computer's keyboard (20) and that employs ratiometric capacitive sensing techniques. This approach allows a computer user to move a cursor (12) about on a display (14) by skimming his or her fingers (24) over the keyboard (20) without actually depressing any of the keys. The preferred sensing arrangement comprises a circuit for first charging a resistive layer (16) disposed on an active portion of the keyboard and then discharging the layer (16) by simultaneously connecting each of several spaced apart electrodes (36) to respective inputs of a multi-channel charge detection circuit (40). For a one-dimensional pointing device, two or more charge transferring switches (62) and electrodes 36 are required, with two being the preferred number. For a two-dimensional pointing device, three or more charge transferring switches (62) and electrodes (36) are required, with four being a preferred number.

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First Claim