Just FYI: 

I have feed into an Ag Leader Integra , with NMEA string; from a AG15 globe  (500 Ez-guide system) BUT it required a special cable so that Ag Leader didn't backfeed a 12 volt circuit into the 500 system, which will "burn-up" the 500 unit. 

There was actually 2 short cables involved = got both from Ag Leader dealer (note: It turns out, I actaully owned one of the short cables, if I had only looked into my old Integra shipping box, before driving to Ag Leader Dealer)