Found in a Popular Electronics from the 90's, this circuit can generate frequencies according to the values of the employed components, according to the table next to the diagram.
This circuit monitors extra-low frequency (ELF) fields. We found it in an American documentation from the...
We can use any type of resistive transducer with central resistance in the range of 10 k ohms to 1...
This circuit controls two lamps so that when one increases in brightness the other decreases. The...