This circuit drives 4 sequences of 5 LEDs that can be of any color. The frequency depends on the characteristics of the photosensor. The circuit is from an 80's documentation.
In the figure we have the typical configuration of a Hartley oscillator. This circuit generates...
Found in an Electronics Now from the 90s this mixer has several inputs. The integrated circuit can...
This useful power supply was found in an 1985 Italian publication, but can still be assembled...