This circuit is for a siren that can be used with any of the above alarms and also other types. The circuit is from a Radio Electronics magazine from May 1975.
The integrated circuit used in this project is not common today, but it can be implemented with more...
Found in an American publication from 1969, this circuit can be adapted to be used as a shield....
This current meter with many scales was found in a 80s American documentation. The operational amplifier...