"Dick Locke" wrote in message
...
Hi, I have a Furuno GPS-32 that has been successfully interfaced to a
PC for navigation for quite some time. Now I want to hook up the GPS
output to a Uniden Polaris VHF.

Dick,

The TD-C/SG is indeed the common return for both outputs. The difference
between both outputs is that Data 2 (SD/RD/SG) is at RS-232 levels and Data1
(TD-H/TD-C) is a current loop output, meant to drive an input with an
optocoupler for galvanic isolation. This output can drive more current than
the RS-232 can. If the VHF only has one signal in, connect this to TD-H and
connect the ground of the VHF to SG.

Meindert