This circuit was originally intended for reading movie soundtracks. The circuit is from 1967 and was found in an English publication. The sensor is semiconductor type.
This configuration for switching signals uses only common general-purpose diodes such as 1N4148. The...
This digital electronic game circuit was found in a 1982 publication. It randomly draws the...
This version works in the opposite way to the previous one, activating when the light falls on the...