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Connection Considerations
The marine instrument connects to power and to data sources
through a NMEA 2000 network.
Although the instrument cannot directly receive NMEA 0183
data, it can display NMEA 0183 data from sources connected to
a GNX
™
20 or GNX 21 device (sold separately) on the same
NMEA 2000 network.
The instrument can also receive data from Nexus
and sensors using a GND
™
NMEA 2000 Connection Considerations
If you are connecting this device to an existing NMEA 2000
network, the NMEA 2000 network should already be connected
to power. Do not connect the NMEA 2000 power cable to an
existing NMEA 2000 network, because only one power source
should be connected to a NMEA 2000 network.
If you are connecting this device to an existing NMEA 2000
network or engine network by another manufacturer, you should
install a NMEA 2000 Power Isolator (010-11580-00) between
the existing network and the Garmin devices.
If you are installing a NMEA 2000 power cable, you must
connect it to the boat ignition switch or through another in-line
switch. NMEA 2000 devices will drain your battery if the NMEA
2000 power cable is connected to the battery directly.
The marine instrument connects to a NMEA 2000 network on
your boat. The NMEA 2000 network provides power to the
marine instrument and data from NMEA 2000 devices such as a
wind sensor. The included NMEA 2000 cables and connectors
allow you to either connect the device to your existing NMEA
2000 network or create a basic NMEA 2000 network if needed.
If you are unfamiliar with NMEA 2000, you should read the
"NMEA 2000 Network Fundamentals" chapter of the Technical
Reference for NMEA 2000 Products. To download the
reference, go to garmin.com/manuals/nmea_2000.
2
®
instruments
10 device (sold separately).
NOTICE
Wind transducer
GND 10 black box bridge
Marine instrument
Ignition or in-line switch
NMEA 2000 power cable
NMEA 2000 drop cable
Power source
NMEA 2000 terminator or backbone cable
NMEA 2000 T-connector
NMEA 2000 terminator or backbone cable
NMEA 0183 Connection Considerations
• The marine instrument can receive NMEA 0183 data from
one device using a NMEA data cable (not included), but it
cannot transmit data from the NMEA 0183 device to the
NMEA 2000 network.
• If you are replacing a legacy Garmin marine instrument that
currently uses a NMEA data cable, you do not need to
purchase a new data cable, but you might need to replace
the quarter-turn locking ring with a threaded locking ring. See
your local Garmin dealer or
information.
• The installation instructions provided with your NMEA 0183
compatible device should contain the information you need to
identify the transmitting Tx/A (Out +) and Tx/B (Out -) wires.
• When connecting NMEA 0183 devices with two transmitting
wires, it is not necessary for the NMEA 2000 bus and the
NMEA 0183 device to connect to a common ground.
• When connecting a NMEA 0183 device with only one
transmitting Tx (Out) wire, the NMEA 2000 bus and the
NMEA 0183 device must connect to a common ground.
• For extended runs, you should use at least 0.33 mm
(22 AWG) wire.
• You must solder and seal all connections with heat-shrink
tubing.
Wire Color Wire Function
Red
A red wire is present only on some variations of the data
cable, and should not be connected.
Black
Accessory (-). This wire is used only when connecting the
marine instrument to a Garmin HVS GPS antenna.
Yellow
Accessory (+). This wire is used only when connecting the
marine instrument to a Garmin HVS GPS antenna.
Blue
Tx/A (Out +). This wire is used only when connecting the
marine instrument to a Garmin HVS GPS antenna.
White
Tx/B (Out -). This wire is used only when connecting the
marine instrument to a Garmin HVS GPS antenna.
Brown
Rx/A (In +)
Green
Rx/B (In -)
NMEA 0183 Connection Diagrams
This diagram is an example of a connection to a standard NMEA
0183 device with two Tx wires.
www.garmin.com
for more
2
GMI 20 Installation Instructions
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