Garmin Connector
Connecting the Garmin GPS Unit:
A beautiful drawing thanks to: Dr. Thomas Vonesch from Switzerland

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The GPS unit is connected to the serial port (9 pin (DB-9) or 25 pin (DB-25))
of the computer by using the cable described in Garmin's User Manual.
There are only three pins used by PC programs - Data in, Data out and Ground.
Computer
Garmin GPS* 9-pin serial 25-pin serial
Ground pin 2 -------------> pin 5 Ground pin 7
Data Output pin 4 -------------> pin 2 Receive pin 3
Data Input pin 5 -------------> pin 3 Transmit pin 2
* The pin numbering is valid for the Garmin GPS 45.
Consult your manual for other models.