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 suggested in the figure differentiates the signal from the negative front of a...
This frequency triple oscillator circuit was found in an American publication in 1967. The FET is...
This circuit was originally recommended for an electric oven warning system. However, we can use...