This circuit for signals up to 30 MHz can improve your reception in the medium and short-wave band. We found it in the Radio Electronics magazine of February 1989.
This circuit, which appears with variations on the website, is from European documentation from...
This circuit for old analog telephones is from period documentation. It controls a relay that can...
This circuit, found in an English publication in 1982, has an inverted sequential effect, as the...