I have a 2 ft. long piece of shielded four-core cable coming out from
the bottom left of my panel near the map pocket on the pilot's side.
The cable is terminated in connector so that the converter can be used
without permanent installation. The four cores carry ship's power at
12V, ground, the RS-232 from the panel mount GPS, and the RS-232 output
to the 396. The 396 was installed on the pilot's yoke earlier. See
linke [1] below for details. The panel mount GPS RS-232 signal comes
from either my #1 or #2 GPS, as selected by an already-installed switch
that is used to route the same signal to the WX-1000E StormScope.

[1] http://www.mikeg.net/plane/n8096j/gps396/