Here are a few questions for you sonar experts. I am looking to network an old HDS 5 or 7 with a new HDS 7 Touch. What model HDS 5 or 7 do I need to network with the newer unit and be able to mirror the information from the new unit on the older unit? Does the older unit need to have both sonar and GPS capability to accomplish this? Does that make sence? Also what hardware is needed to physically needed to make that connection? What else may be needed that I don't know about? Thanks for the help!