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Number of NMEA 0183 sources that can feed data to a single GMI 10 or GMI 20 at one time
The GMI 10 and GMI 20 have only one NMEA 0183 port. Garmin recommends connecting only one device to the existing NMEA 0183 port.
If more than three NMEA sources are desired, a NMEA 0183 Multiplexor will be required. The NMEA 0183 Multiplexor will take multiple NMEA 0183 inputs and output a single NMEA 0183 data stream which can then be connected to the GMI 10 or GMI 20.
Garmin does not offer a NMEA 0183 Multiplexor.
For more information about wiring a NMEA 0183 device to the GMI 10 or GMI 20, please review the Installation Instructions for the device.