We have many versions of biofeedback with the 555 IC on this site. This is another one. We found it in October 1986 Radio Radio Electronics magazine. The power supply must be isolated.
The block shown in the figure is a basic source with a configuration widely used in technical...
Found in July 1975, Radio Electronics magazine this circuit can use any operating circuit,...
This oscillator produces an audible signal on a piezoelectric transducer. The frequency is...