This circuit was found in the February 1985 issue of Radio Electronics magazine. It is based on an AY-3-1350 melody generator that was common at the time. It is suitable for analog lines only.
This circuit is from the 80's component manual itself, but can be applied to more modern...
A more efficient filter is the one that diverts the signal to the ground and not only short it, as...
The figure shows the basic configurations for unijunction oscillators. They are relaxation...