Sonar data is transmitted over an ethernet cable. GPS and temperature information is transmitted over a NMEA 2000 backbone. These are two seperate sets of differing cables. After the appropiate cables are ran, then the user would need to go into the menu of each unit and adjust the settings so the desired function is obtained.
For sonar you will need an ethernet cable, this is the one with the yellow ends. Go to http://www.lei-extras.com and click on networking and then hit ethernet and the page will come up that has all the ethernet cables on it. Here you will see the different lengths and can choose the one that fits your needs.