Found in an American publication from the 1980s, this circuit can be found in commercial sound equipment of the time. The list with the component values is given next to the diagram.
This sensitive motion sensor with inductive sensor was found in a 90s Elektor. The circuit uses only...
This simple balance indicator for sound equipment was found in a 1982 documentation. The M1...
This circuit was found in a 1992 documentation. It uses a photo diode as a receiver and an...