I am running a LCX16ci and a GLOBALMAP 3000mt off the same antennae, you have to find out the pin out and wire colors on each unit which is on the Lowrance site and hook up the send wires from your head end unit to the receive wires on your second unit. Then go into the setup menu on the respective units setup the send receive for each unit and then make sure the baud rates are the same. It may all sound complicated but I had the same question last spring and someone from this site helped me out. Hope this helps, possibly do a search on GPS units to find the thread. Good luck, know you will get the units working together.