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 was found in 1966 General Electric documentation. The circuit uses components from the era...
We found this circuit in a magazine 73 for radio amateurs from the 80's. The circuit makes use of an...
This circuit uses one of the first comercial transistor and is from a 1958’s magazine. Tone...