Adding AIS650 to existing NMEA0183 Network

[bbayne]

Refreshing my memory on this as I haven't added AIS yet. Looking over the connection chart (attached again), I'm wondering why the S3G is required to an NMEA Out to the MUX. Isn't this data already contained in the ST1 network? Or does fast heading output data only get transmitted via NMEA?

I took this from the S3G manual:
a NMEA 1 output so the radar/chartplotters can use the fast
heading output from the course computer to enable MARPA
(see page 37)

Does this answer my question above or does fast heading output data also talk via ST1?

Thanks!