US Patent 7372455 Touch detection for a digitizer

A detector for detecting touches by fingers or like body parts on a sensor comprises at least one sensing conductor, typically a grid of such conductors, extending into the sensor, a source of oscillating electrical energy at a predetermined frequency, and detection circuitry for detecting a capacitive influence on the sensing conductor when said oscillating electrical energy is applied, the capacitive influence being interpreted as a touch. The detector is advantageous in that the same sensing conductors can be used both for touch sensing and for detection of an electromagnetic stylus.