This will need to be connected to your RS232 interface. In my use case, I built a RJ12 > DB9 cable to use with a Serial > USB adapter. The RJ12 connector on the controller has 6 pins, with the first 3 ...

Starting with an Apple MiniDin8 Male cable, he cut off one end and attached the wiring to a RJ45 connector. That got plugged into a modular adapter with a DB9 Female Plug end and wired up.