This circuit was found in a 1970s documentation. The components are from that time, and semiconductors are difficult to obtain today.
This metronome circuit was found in an American 1980s documentation. The circuit uses the 4001...
This circuit was found in the December 1992 issue of Radio Electronics magazine. The current is a...
This circuit operates at a voltage of 1.3 V from a single mercury cell. We found in an old...