Found in American documentation from the 1980s, this circuit uses transistors from that time. It generates increasing and decreasing tones when we press and release the push button.
The circuit shown in figure 5 generates square signals based on a transconductance operational amplifier...
By adding a transistor to the output and some polarization features we can obtain a higher output...
Found in the 1990 special issue of Radio Electronics Experimenter magazine, this circuit uses an...