This alarm goes off if someone leaves a door open. We found it in the Encyclopedia of Electronic Circuits Volume 5 from 1995. The circuit uses components that are still common today.
Using transistors of the time, this circuit was published in Radio Electronics magazine in...
) The integrated circuit used in this control is uncommon today and the maximum current obtained allows...
We found this circuit in an old American documentation. Accuracy has 0.02% error and 0.003%...