Humminbird uses Ethernet to share data and connect to Ethernet accessories.
Engine data is via the AS ETH NMEA2K connected to the unit with an Ethernet cable.
To have more than two devices connected to share data takes the Ethernet switch AS ETH 5PXG. Each device connects to the switch and all data is shared.
The Helix units need an Ethernet adapter to connect an Ethernet cable to them-AS EC QDE.
The first generation Helix 10 SI uses a HDSI transducer and the second generation G2N SI model uses the MEGA SI transducer. The MEGA has a dedicated Down Imaging crystal and the first generation gets the DI view by blending the two SI pulses.
Humminbird Helix 12 CHIRP SI, 1198c SI, 1198c SI, ONIX 10 SI NT, Helix 7 CHIRP SI GPS G2, SOLIX 12 SI, 360, RC-1