This circuit shows that we can implement a voltage-controlled oscillator with almost any CMOS that can be connected as an inverter. The circuit is from Radio Electronics from January 1987.
Found in an American publication from the 1980s, this circuit can be found in commercial sound...
With the use of an additional diode and a resistor, the configuration of the figure can be...
This sound meter or sonometer was found in a Popular Electronics from the 80's. The circuit can be...