This circuit for musical instruments was found in a 90’s Elektor. The circuit still applies, as the components used can still be obtained with some ease.
The circuit, shown in the figure, activates a relay when the logic level applied to its input, from...
The traditional circuit was taken from a French magazine Radio Plans that no longer exists but can...
This circuit makes use of the LM11, 112 or 113 operatives and was found in a 1980s documentation. The...