The IntelliChlor Controller Circuit Board communicates to the IntelliCenter MotherBoard via an RS-485 4-conductor, 22 AWG or larger cable.
The cable connects to either JP2, JP3 or JP4 on the IntelliChlor Controller Circuit Board and connects to either of the COM PORTS on the MotherBoard. Either RS485-A (J5) OR RS485-B (J4).
Here is a diagram and which can also be found on pp 33 of your IntelliCenter Control System Installation Guide.