Abstract: There are provided an apparatus for detecting an approaching conductor and an approach point or position of a conductor, in which a signal processing is simply performed and an improvement in the noise resistance is performed without the influence of a floating capacity. The apparatus has a voltage-oscillating system for equivalently receiving electric oscillation (AC signal) from a detected conductor so that the received electric oscillation is processed as a signal to ground and the processed signal is send to a non-oscillating system through an isolator, the system including a sensor panel or a sensor conductive array, a shield plate, a signal processing circuit, a ground, and power source. In addition, in order to clearly and securably identify a cause of the false earth effect of a detected conductor such as a human body, over 200 kHz oscillation frequency is provided.

Abstract: A touch panel apparatus has a sensor panel using a tin oxide resistive film that avoids the palm effect and has an improved noise margin and S/N ratio. A finger or conductor is brought into direct contact with the touch panel and injected with an AC signal of 200 kHz or more, a signal current is detected, and the current is converted into a voltage by a transistor connected to an LC resonance circuit. The touch panel is contained in a voltage-floating system insulated from a non-floating system through a capacitor of 5000 pF or less and has an A/D converter in which a step-shaped triangular wave is superimposed on a measured voltage so that output at each step of an analog/digital converter is added.

Abstract: A noiseproof digitizing apparatus for digitizing the coordinates of a point on a tablet having grid conductors disposed along X and Y coordinate axes includes a cordless pen having a conductive end for transmitting an electrical signal to the grid conductors through of electrostatic capacitive coupling. An AC signal generator generates an AC signal and applies a balanced output of the AC signal to the conductive end, such that electrostatic capacitive coupling between the conductive end and the grid conductors causes a major balanced AC signal component and two minor unbalanced AC signal components to be produced in the grid conductors in response to the AC signal on the conductive end. A power supply supplies electrical power to the AC signal generator. A signal level measuring device measures the level of a signal current resulting from a sum of the major balanced AC signal component and the two minor unbalanced AC signal components produced in the grid conductors.