When I was looking at catalogs of various analog circuit designs, a lot of them were circuits RCA patented that now are public domain because the patents are no

When I was looking at catalogs of various analog circuit designs, a lot of them were circuits RCA patented that now are public domain because the patents are now expired. They probably aren't the only ones, but they certainly contributed a lot. https://patents.google.com/?q=(analog+circuit)&assignee=rca&oq=assignee:rca+analog+circuit&sort=old&page=1 https://patents.google.com/?q=(analog+circuit)&assignee=rca&...