Found in a 1965 Electronic Design, this circuit makes it possible to select signals with an inverted phase using a relay and a unit gain stage.
This stethoscope or hearing aid amplifier has excellent gain. It was found in Popular Electronics from...
Found in Fairchild documentation from the 90s, this circuit generates signals with the...
This configuration, widely used in our articles and on this website, uses a 555 to control a relay...