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.
Found in a 90s Radio Electronics, this circuit is intended to drive a neon lamp from a 9 V source....
This simple tester was found in a Popular Electronics from the 90s. The circuit is powered by two...
Electronics Now from the 90's suggests this pulse conditioner circuit for use in tachometers. The...