This sequential circuit appears in other versions on this site. This is from American documentation from the 1960s. The speed of the effect is set to R1.
We found this heart rate sensor circuit in a Popular Electronics from the 90s. The placement of...
Based on an LM317T, this circuit found in Popular Electronics works with signals of frequencies up to...
The circuit shown is from a 1972 publication. Transistors can be current types like 2N2222. The...