Patent ID: 7023427

Claim:
A method for indicating if a set of simultaneous contact points on a touch-sensitive screen contains a plurality of contact points, the method comprising: setting a multiple contact point discrimination threshold representing a minimum difference in voltage expected between conductors at opposing edges of the touch-sensitive screen when multiple contact points are presented; setting a conductor on a first edge of the touch-sensitive screen to a first reference voltage; setting a conductor on a second edge of the touch-sensitive screen to a second reference voltage, the second edge being across the touch-sensitive screen from the first edge; taking a first measurement of a voltage associated with a conductor on a third edge of the touch-sensitive screen, the third edge being adjacent to the first and second edges; taking a second measurement of a voltage associated with a conductor on a fourth edge of the touch-sensitive screen, the fourth edge being adjacent to the first and second edges and across the touch-sensitive screen from the third edge; comparing the multiple contact point discrimination threshold with a difference between the first and second voltage measurements, the difference reflecting a difference in proximity between the set of simultaneous contact points and the third and fourth edges of the touch-sensitive screen; and if the difference between the first and second voltage measurements is greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a plurality of contact points.