Found in American documentation from the 90s, this circuit can be applied to other operational ones. We found it in an EDN of the time. Next to the diagram is the response curve.
Found in American documentation from the 1970s, this circuit employs an integrated circuit from...
This circuit was obtained in the publication 101 Electronics Projects of 1979. The circuit can be...
This assembly circuit using a small motor as a generator was found in Radio Electroics magazine from...