Poptronics recommends this circuit for use in the car when the headlights are left on. The circuit uses a sensitive relay with contact current according to the headlights.
This touch sensor, found in an American documentation on transistors, has gained 8 million times...
The block shown in the figure is a basic source with a configuration widely used in technical...
The output of this circuit must be connected to the input of an audio amplifier. The microphone is a small...