This two-tone decoder has a bandwidth of 24%. The circuit is from a 1994 Electronics Now. The components without the value determine the recognized frequency.
This circuit was found in a 2006 publication. It can serve as the basis for a microcontrolled...
This circuit was found in a 90s Signetics documentation. The circuit is switched based on...
Using an operational amplifier TLC271, but with a more effective action, we have in the figure, a...