This circuit is from National Semiconductor using an LM11, which is uncommon nowadays. The circuit can be implemented with other operational ones.
The circuit suggested by National Semiconductor mows signals from a peak determined by the...
This 90's project shows how to use an old cassette recorder to practice telegraphy. In position A of the...
This circuit from Radio Electronics magazine, March 1994 edition uses two LM388 bridged, providing a 4...