We found this simple toy organ circuit in the February 1968 issue of Radio Electronics magazine. The transistors were common at the time and the transformer was from a transistor radio output.
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...