This circuit visually indicates that a high voltage is present in an outlet or other point. The neon lamp is common, and the appearance of the assembly is suggested in the same figure.
Found in a Hands On Electronics from the 90s, this circuit can be easily assembled today, as the...
Found in a 90's EDN, this circuit generates signals in the frequency range given by the graph. The...
This flip-flop circuit with general purpose transistors was found in American documentation from...