Using Hand Signals

I got a ticket for not having turn signals on an old farm trailer with a triangulated yield sign attached, and despite using hand signals still got a ticket. I told the cop I was within the law and that the triangulated sign was legal and so were hand signals. He informed me that not everybody knew what hand signals meant, at which point I informed him that it was my job to obey the law, not teach others about the law. Had to go to court to fight it, and I told the judge and the cop who was present the same thing again, and the ticket was dismissed.