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.
This circuit shows how to use flip-flops in a SIPO circuit with serial input and parallel output....
This circuit was found in the National Semiconductor Linear Applications Handbook, published in...
This circuit is from an 80's technical newsletter. The circuit can use any general purpose...