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 can be used to receive signals from CB18636E and other modulated light transmitters in this...
Due to its low working voltage, this circuit of an old EDN can be associated with a...
We found this circuit in a 1983 English magazine, but it can be easily assembled with the BC548...