This circuit was found in documentation for radio amateurs of the 1980s. The circuit is intended to produce a tone for modulation in telegraphic transmissions.
In this circuit, from a 1977 publication, we have the traditional version of a filter that rejects 1...
The integrated circuit used in this application is uncommon today. However, the basic...
This physical line servo control uses components that are not currently common. The circuit is from...