Circuit for monitoring an alternative current power switch

摘要

A circuit (1) for monitoring the state-open or closed-of an ac switch (2) has an input (4) which is connected by way of a diode (9) and a first resistor (10) to a high-ohmic input (11) of a first digital component (12). One terminal of the ac switch (2) is connected to the phase (P) of a mains voltage (UPN), while the other terminal is connected to the input (4) of the circuit (1). The high-ohmic input (11) of the first digital component (12) is connected by way of a second resistor (13) to an output (14) of a second digital component (15). In accordance with a predetermined time lapse, the output (14) of the second digital component (15) is either connected to the neutral point (N) of the mains voltage (UPN) or carries a voltage which is greater than the threshold voltage (US) of the input (11) of the first digital component (12).