Found in a 1967 Electronics World, this circuit can use any modern equivalent FET. Observe the amplitude of the input and output signals.
We adapt this circuit of Radio Electronics - March 1990. The magazine no more exists, but the...
The input impedance of this circuit is about 700 k ohm and the output impedance is about 1 k ohm....
Radio Electronics magazine published in a 90's issue this simple alarm that can use any general...