Jason KG4WSV kg4wsv at gmail.com
Sat Feb 5 13:54:34 EST 2011

On Sat, Feb 5, 2011 at 12:41 PM, Joe Della Barba <joe at dellabarba.com> wrote:
> I just got a Garmin GPS-18-C to replace my Magellan 315. It is on my boat
> connected to the laptop, VHF and TT2. This has always worked fine until now
> with the 315. The Garmin will not run the TT2 and the computer at the same
> time. If I connect the computer, it works and the VHF works, but the green
> light goes out on the TT2. Disconnect the computer and the TT2 works again.
> Very frustrating. Any ideas?????

RS232 is specified for point-to-point; your 1-to-2 arrangement usually
works, but it isn't spec.

The Garmin GPS18PC, GPS18LVC, and GPS18-5Hz units do not output
standard rs232 voltages; they use 0V and 5V (TTL voltages) instead.
This generally works in spite of being non-spec, but I suspect when
you are adding an additional receiver there isn't enough drive for


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