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 can be used in PLL, frequency synthesizer in FM and VHF receivers, reducing a...
We found this circuit in an old documentation. Transistor can be BC548 and relay according to...
This is a typical 3 ½ digit TTL counter. We found it in the September 1973 issue of Radio...