This circuit appears in several versions in publications of the time and can be modified by changing the capacitors. This one is from Radio Electonics magazine from October 1992.
Using 555 integrated circuits, this alarm circuit was found in a 90s American documentation. The signal...
Found in the May 1988 issue of Radio Electronics magazine, this circuit is sensitive to small...
We found this circuit in an English publication from the 1980s. The circuit uses current...