Turn signal indicator 64 Barracuda- help me understand

Thanks 67Dart273. I figured it must use the other circuit of the signals somehow but wasn't sure how. This explains it very well. I've been working on these cars for almost 50 years and had never dealt with this. Never stop learning! All of my turn signal lamps work but I'll clean up everything on my front signal connections to ensure low resistance and see if that helps.