This dual-LED circuit indicates three signal levels. It was found in the January 1996 issue of Electronics Now magazine. The integrated circuit may be an LM339 or another comparator.
This circuit from an old documentation includes the power supply for the 117 V power grid. It can be...
Found in a Popular Electronics from the 90s, this circuit presents the difficulty of obtaining the...
This ultra-simple 9 V power source was obtained in an Argentine publication of the 1970s, but it...