The pilot has two control channels that can support up to SIX total control heads (three each per channel). Each channel must end with a bus terminator. If you have one control now, it is normally simple enough to remove the bus terminator from the back, then connect a cable to the second and then put the terminator on the end of the last unit in the bus. (Called daisy chain) The part number of the cable depends on the length of cable you need. The normal one used it 10 meters (p/n 000-147-231).