Using the CA3140 in the figure we have a comparator that goes low in the window voltage space. The circuit was found in June 1986 Radio Electronics magazine.
The purpose of this circuit is to eliminate RF picked up by a turntable. The circuit is from a...
This circuit synchronized by the power grid can be used as a shield. We found it in an 80's...
This is a very simple version in which we simply fit the jacks, plugs with red and green LEDs,...