We found this circuit in the Radio Electronics magazine of May 1977. The circuit has the frequency given by the components according to the formula next to the diagram.
This circuit was obtained in an American documentation translated in the 80's. The circuit can be...
This electronic roulette circuit with 10 numbers was found in a Popular Electronics from the 80s....
Based on a CA3059 zero-cross switch, this circuit was found in the July 1995 Electronics Now...