This circuit was found in a Popular Electronics from the 90's. The output signal can be applied to a headphone or speaker. The microphone can be a piezoelectric tweeter capsule or other type.
This circuit, suggested by Texas Instruments, is based on the integrated TL497A, designed for...
In the figure we have the way to implement a sinusoidal oscillator with the 4093 IC. The component...
This circuit was found in an old American documentation. It can operate with signals from 40 Hz to...