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.
If the input voltage falls below 12 V the LED glows up. Other voltages can be monitored by...
This motor control using transistors was found in a recent English publication. The circuit is for...
In the figure we have an electronic toy organ that can both serve to amuse children as a basis for...