Using the LM3909 this circuit was found in the January 1992 issue of Radio Electronics magazine. Resistor R1 should be chosen according to the table given next to the diagram.
This circuit had its assembly described in a Radio Electronics from March 1963. The circuit uses 2...
We found this configuration in a documentation for radio amateurs from 1974. The circuit can be...
We found this circuit in an English documentation from 1989. The integrated circuit used is not...