This circuit can be used as an answering password system in a store, office, or other location. The circuit is from Intersil using components of the time. The circuit is from the 80's.
This capacitive sensor that operates with a high frequency oscillator was found in Radio...
We have many versions of biofeedback with the 555 IC on this site. This is another one. We found it...
This amplifier, found in a 1980s documentation, should be powered by a symmetrical source. Modern...