This VCA was found in the July 1988 issue of Radio Electronics magazine. It uses an OTA op amp and has its gain adjusted by the voltage at the gain input.
This very simple circuit must use coal microphones of the type found in very old equipment. The...
This biestable circuit was found in a Popular Electronics from the 90s. The circuit has an unusual...
This circuit was found in a 1969 US documentation. It provides a signal that can be externally...