This circuit is from an article in Radio Electronics magazine from October 1958. The circuit is for testing electrolytics that operate at high voltages depending on the source.
This LED special effects circuit was found in the February 1992 Radio Electronics magazine. The...
Found in an American publication from the 1980s, this circuit can be found in commercial sound...
Found in Philips' 90s documentation, this small source can use modern transistors like the BD135...