Seatalk2 to STng

[tgsail1]

Ok I think I understand this. I tried attaching the i50 installation and operating instructions 81341-4-ENG, but it wouldn't let me. Page 30 (sec 4.7) shows a seatalk network. Here the devices will bridge the data between the devices. It appears that even though STNG connections are being used, only ST data are being transferred, so even though it looks like instruments 2,3 &4 are talking via STNG, they are in fact talking via ST. Is that the case? If that is the case then no device which requires STNG (eg ST290 speed or p70) will operate on this network. Note that while the p70 does not "require", STNG, you can't calibrate the autopilot without it, so it kind of does require it.
Thanks