The idea of this circuit found in a Radio Electronics from January 1966. The idea of the circuit is to improve the reception of audio signals, mainly telegraphy, working as a filter.
This circuit was obtained in a 1995 Electronics Now. It switches off a relay after an interval that...
This circuit with a MOSFET is from an old American documentation. The capacitor should be leak...
We found this circuit in old documentation. Modern equivalent operational amplifiers can be used....