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.
This circuit uses one of two D-type flip-flops available on an integrated circuit 4013. The...
We found this circuit in an old English documentation. The idea is a momentary indicator that...
I found this circuit in an old document from 1981. The circuit can be implemented today with the...