This whole discussion appears to be relevant to a problem I am having. No intent to hijack....
I've got a functional Furuno GP 31 (GPS) trying to communicate with a new B&G h3000 instrument system via 0183. The B&G just ignores the Furuno, which has operated successfully with the B&G's predessor, an h1000. I have very limited diagnostic resources...no computer at hand at the moment.
The data stream from the Furuno seems to exist, that is, there is a series of positive-going (from 0) pulses, 2V at 1-1.5 seconds which, according to the B&G techs, is good news in that the pulses exist at all, bad news that the pulses are only 2V. I took the measurements at the input plug of the h3000. Furuno NMEA + out goes to the B&G + in; FURUNO out - to the B&G - in , not to gnd .
The Furuno folks are taking the position that even if the problem is not theirs, they are probably in the best position to do something about it. What a pleasant surprise THAT is.