[GPSNavX]

MacENC uses NMEA data to navigate with. The Garmin antenna itself does not have the ability to send the NMEA data to a Mac or MacENC. Instead you must interface to the Garmin GPS receiver through its power data cable. The power data cable has NMEA out, NMEA in and ground. They can be connected to the following cable ..

http://www.gpsnavx.com/html/datacable.html

Which in turn is connected to a Keyspan adapter that plugs into the USB port on your Mac ..

http://www.tripplite.com/EN/products/mod...delID=3914

On the GPSMap220 the round connector:

Pin 2 black is ground
Pin 3 blue is NMEA out
Pin 4 brown is NMEA in

More here for configuring MacENC to use the NMEA data via a Keyspan adapter ..

http://www.gpsnavx.com/MacENC/help/connectinggps.htm

Or if you prefer not to bother with the wiring it is far simpler to use a BU-353 USB GPS as reference in an earlier post. It plugs into the Macs USB port.