This indicator circuit used and game machines (arcades) to indicate that the machine is being shaken was found in NASA documentation. The circuit uses as a sensor a container with water and three sensors.
This circuit for the 3.5 MHz band (80 meters) was found in an old radio amateur documentation. The circuit...
This JFET amplification stage was found in the April 1993 issue of Electronics Now. The input...
We found this circuit in a Popular Electronics of the 80s. The circuit can be made with almost any...