This small tone generator was found in the November 1987 issue of Radio Electronics magazine. The phototransistor is common and controls the sounds generated. The basic frequency is given by C1.
The circuit shown is suggested by National Semiconductor in its 1994 Linear Applications Handbook. We...
The ZN416E integrated circuit is uncommon today. It consists of a complete radio, like the one...
In the figure we show how to implement a voltage reference with the ON Semiconductor rail-to-rail...