There are a number of things that happen in various multiplexors. They can do protocol changes and speed changes. Not all do everything.
There are a lot of flavors of Seatalk
: 1, hs, 2, and ng. There are speeds and flavors of NMEA
protocols: NMEA 0183
at 4800 bps and 38400 bps and NMEA 2000
. There are a few other protocols floating around out there (Robertson and Simrad
are a couple).
Depending on what kind of hardware
you have you may need some conversion somewhere. Although Raymarine pushes SeaTalk most of their chartplotters and autopilots also have ports
for NMEA 0183
It's a real pain but you can get everything to talk to everything. The multiplexor you have may be a necessity or an installation