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.
This stage was used in old audio ampliiers and radios from the 1950s and 1960s. It uses one of the...
Found in a 90s R-E Experimenter Handbook, this amplifier uses an integrated circuit from that...
We find this circuit in an American 1980s documentation. The unijunction transistor may be the...