This circuit with a bargraph scale was found in a 90s Popular Electronics. The circuit measures the intensity of a sound in three scales. R14 works as a sensitivity adjustment.
This circuit, from a publication from the 1970s, can be implemented with more modern transistors and 6 or...
This circuit switches off a load in case of excess current acting as a fuse. The circuit is from a...
This circuit was obtained from a manual of the integrated circuit itself, but can be applied to...