Found in American documentation from the 1980s, this circuit can be designed with equivalent components. The microphone can be of the piezoelectric type.
A touch of a sensor triggers this minute for a time determined by R4 and C3. Times can be between a...
In the figure we have a simple thermometer with NTC, using an analog current indicator. The...
We found this circuit in an old documentation. What it does is flash two LEDs when night falls or when...