Nikon D300 User Manual page 226

Other GPS Units
Optional Garmin GPS units that conform to version 2.01 or 3.01 of
the National Marine Electronics Association NMEA0183 data
format can be connected to the camera's ten-pin remote terminal
using an MC-35 GPS adapter cord (available separately; pg. 370).
Operation has been confirmed with Garmin eTrex and Garmin
geko series devices equipped with a PC interface cable connector.
These devices connect to the MC-35 using a cable with a D-sub 9-
pin connector provided by the manufacturer of the GPS device.
See the MC-35 instruction manual for details. Before turning the
camera on, set the GPS device to NMEA mode (4800 baud).
MC-35
t
200