The circuit shown is from the 1994 Linear Applications Handbook by National Semiconductor. Some of the components are not currently common and should be looked for equivalents.
This circuit is for transducers (headphones or speakers) of 200 to 300 ohms. The frequency is...
This circuit uses only two transistors, the first being low noise, being indicated for dynamic...
Found in 1960's Radio Electronics, this circuit provides an audio tone that depends on the logic...