This circuit is designed to analyze the distortion of an audio signal. We found it in an article in the October 1988 Radio Electronics magazine that teaches how to use it.
We found this measurement circuit with a logarithmic scale in an Electronics Now from November 1995....
This circuit assumes that a pulse produced by S1 has a constant duration determined by R1 and C1....
This circuit is used for remote current monitoring. In the original version of the 80s a lamp is...