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.
The circuit is from 1968, but we can use a modern one like the 741. The symmetrical power supply...
The circuit presented uses Linear Technology Operationals, having been found in a 1993 manual. The...
Found in American documentation from the 90s, this circuit triggers a buzzer with a Sonalert-type...