1. US20050162411 - Input system

A user input system (1), comprising a coil (44) for generating an alternating magnetic field, a cordless pen (9), and a capacitive current measuring arrangement or an electric field sensing arrangement. The cordless pen (9) comprises a resonant circuit (34), a conductive housing (28) and a conducting tip (36). The alternating magnetic field induces an alternating voltage in the resonant circuit (34), which is coupled to the conducting tip (36). The capacitive current measuring arrangement comprises a resistive sheet (40) and current measuring means (42) arranged to measure a capacitive current flowing from the conducting tip (36) to the resistive sheet (40). The electric field sensing arrangement comprises an electric field sensing reception electrode (47) and current sensing circuitry (48) for determining a current excited in the electric field sensing reception electrode (47) by an electric field generated by the conducting tip (36). In each case the currents are sensed at plural locations and the differing magnitudes compared to determine a position of the conducting tip (36) relative to the plural locations. The system may also be adapted to sense a user's finger (8). The user input system (1) may be incorporated in a display device, for example an active matrix liquid crystal display device (4).