Relay cable to connect/add the relay packs. DE9 (db9) com cable m-f. somtimes call 9pin Dplug. for the 8 channel analog controler or the copilot. I have controller and a relay pack, but I can not test without a relay cable. If I knew what the pinout configuration was, I would try a 6ft computer com cable and re-pin it. I don't want to spend 30 bucks for a cable, when I am just testing to see if it works.