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 1969 documentation, this circuit consists of a multi-oscillator with neon lamps....
This circuit is suggested by Motorola and consists of a voltage reference based on an MC1403. The...
Published in Radio Electronics in January 1963, this circuit uses 5 transistors of the time. The...