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 integrated circuit used is a version close to the 555 manufactured by Motorola. The circuit shown...
The circuit shown is from an American publication from 1970. It produces a tone that attracts fish...
Suggested by General Electric documentation from 1968, this circuit activates a relay after 60...