Schneider Electric Sa

Frank Schmitz

Christoph Klees

Michael Schlicker

Protective circuit

Safety circuits with an actuating device for electrical appliances, where the actuating device is capable of being operated by means of two key buttons or switch stacks are of use in many different areas of application. In order to create a generally suitable safety circuit, which is very simple and clear and which therefore brings with it low costs, which however stands up to all safety criteria, including the avoidance of any manipulation it is proposed that the two key buttons (S1, S2) each have a break contact (s1o, s2o) and a make contact (s1s, s2s) and act in combination with an associated driver stage (2), preferably a transistor driver stage with transistors (Q1, Q2, Q3, Q4), that the driver stage has two relays (K1, K2), that an astable circuit or multivibrator (1) with an elementary frequency of about 1000 Hz for the generation of two complementary square wave signals is connected to the relays (K1, K2) via contacts (k1, k2) so that the relays (K1, K2) are dynamically switchable.

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Bergisch-Gladbach, Germany

Frank Schmitz