This is an improved version of the previous circuit also found in the December 1990 Radio Electronics magazine. The duty cycle is also 50%.
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...