Circuitry for compensating for the effect of light on the operation of infrared-sensitive phototransistors in a contact display panel.

摘要

The invention relates to a circuitry for compensating the effect of external light on infrared-sensitive phototransistors (2) in a contact display panel, the phototransistors being coupled via diodes (3) to a common line (c). The compensation circuitry is a voltage-dependent resistor (4) between the common line (c) and the ground of the circuit, the resistance value of the resistor decreasing as the direct-voltage level of the line (c) rises. The resistor (4) is preferably a transistor circuit.