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.
Using power transistors of the time, this source was published in Radio Electronics magazine in...
Found in an American publication on transistors from the 60's, this circuit uses a transistor...
This circuit is from a very old publication, from the 60s. It uses germanium transistors from the...