You will need an AS EC QDE adapter cable for each head unit ... http://www.humminbird.com/Products/AS-EC-QDE/
if you want to Ethernet 2 units and iLink you will need AS ETH 5XPG Ethernet switch ... http://www.humminbird.com/Products/AS-EC-QDE/
The AS ETH 5XPG requires 12v power so plan it's installation ...
Then you will need an Ethernet cable for each head unit long enough to reach the AS ETH 5XPG switch ... http://www.humminbird.com/Freshwater...s/?facets=7319,
The iLink should come with an Ethernet cable to reach the AS ETH 5XPG switch ...
Rickie