If this is a repeated question, please let me know. I'm a hobbyist electronics person, and ran across symbols on a diagram I didn't recognize. I've attached the image below:
What I'm trying to figure out is what the different rings around the wires mean. For example, Earphone Pilot has a connection that shows a ring around one of the wires, and then that hits a T connection where all of them have rings around the wires, too. I've been trying to look it up, but I'm having a really hard time finding info. The full diagram is part of the wiring diagram for a Becker Avionics AR620X transceiver, and the diagram is on page 77 of the PDF here.