On Mon, 25 Aug 2014 16:35:43 -0400, Wayne.B
wrote:

On Mon, 25 Aug 2014 16:16:47 -0400, "Sir Gregory Hall, Esq."
wrote:

OMG! You are stupid. Here's a clue: The ONLY reason direct
current works is when it is able to complete a circuit from
the positive terminal of the 12V battery to the negative
terminal of the battery. NMEA is but an extension of the
mother board circuit in any VHF or GPS. It must be able
to complete a circuit from positive to negative.

===

Stupid is as stupid does. NMEA 183 does not require a ground
reference, just two legs of a circuit. As I understand it, it is
sometimes coupled using opto isolators to prevent an
accidental/unwanted ground reference.

So you have a LED and a photo receptor of some sort. Big
deal. Neither of them will work unless grounded. Nor will
the two NMEA wires work unless one of them is positive and
one of them is negative.

I would direct you to the following sentence found he

http://en.wikipedia.org/wiki/NMEA_0183

"Although the standard calls for isolated inputs and outputs, there
are various series of hardware that do not adhere to this
requirement."


From the same article: "The NMEA 0183 standard uses a simple ASCII,
serial communications protocol..."

Serial port circuits don't work without a positive and a negative
wire or pin.

Just like NMEA circuits don't work without a positive and
negative wire. No circuit - no current can flow.

--
Sir Gregory