This circuit was found in a RE Experimenter Handbook from the 90's. The components are of the time, rare nowadays, except the 555 and 4017.
This circuit is from 1990 documentation. When we press D1 the lamp remains on for a time interval that...
Some old multimeters have a high resistance scale that has an internal circuit powered by a 22.5 V...
This circuit, from a 2001 documentation, appears elsewhere on this site. Its purpose is to obtain a...