There are several different combinations of product networking with the Humminbird family of products.  Below you will see a chart of what is networkable and what cables or accessories are required to network these products together.  

The most important note regarding this chart.  ION Series can only network with ION Series and ONIX Series can only network with ONIX Series.  There is no cross over for these products.  

Click to enlarge image.

NetworkingChart