| 摘要 |
The invention concerns an electric apparatus, such as a time switch, permanently powered by the mains supply between two terminals A and B and whereof the functioning can be triggered by a control input E brought to the terminal B potential by an external contact SW. The following circuit structure is provided to take into account the possible presence of a light indicator or any other load between the terminals E and A: a low voltage supply circuit AL, operating in mono-alternating rectification, supplies a voltage Vdd to a microcontroller MC. The Vdd terminal is connected to terminal B and the voltage Vdd is regulated on another conductor to a potential considered as a zero volt reference. The control input E of the apparatus is connected to a detection input DT of the microcontroller. The microcontroller scans said input to detect whether the contact SW is open or closed: if it is open, the input DT sees a null voltage or an alternative voltage at the period of the 50 Hz or 60 Hz sector; if it is closed, the input DT sees a voltage close to Vdd, and the microcontroller triggers for example the timing of the time switch. The apparatus also operates if the permanent supply between A and B is in direct current.
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