Circuit arrangement for contact switches

摘要

In the circuit arrangement proposed by the invention and the associated method, the side (13) of a basic capacitance (12) which is connected to the mains voltage and the second side (15) of which can be touched by an operator, is connected to an input (16) of a differential amplifier (17), the output (18) of which is connected to the second input (21) via a resistor (20). This input (21) is connected via a capacitance (24) to the mains voltage (22). By feeding back the output signals, a switching threshold of the differential amplifier is created which adjusts itself automatically and thus a self-regulating operating sensitivity of the circuit arrangement is created which is independent of temperature changes and the type of assembly of the contact area. In the case of a number of contact areas, the output signals of only one differential amplifier are preferably fed back to the inputs of a number of differential amplifiers. An annular contact area can be preferably provided which surrounds the other contact areas and is associated with a protective circuit which causes the remaining circuits to be blocked or otherwise switched off. <IMAGE>