This interference rejection circuit for telegraphy was found in a 1980s documentation for radio amateurs. The integrated circuits used are common today.
This is the traditional configuration of a 5 V supply with the 7805 for a current of 1 A. The...
This several short-wave bands receiver, according to the chosen values of the components, was found in...
In the figure we have a stereo decoder from the 70's with pilot lamp for signal indication. The...