Garmin GNX 20 Installation Instructions page 2

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Securely fasten the marine instrument to the mounting
surface using the supplied screws.
If you are mounting the marine instrument in fiberglass, use a
anti-galling lubricant as advised in the notice.
15
Snap the bezel into place.
Connection Considerations
The marine instrument connects to power and to data sources
through a NMEA 2000 network. In addition, the marine
instrument can connect to a NMEA 0183 data source using a
data cable (not included).
NMEA 2000 Connection Considerations
If you have an existing NMEA 2000 network on your boat, it
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 installing the included 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 using the port labeled NMEA 2000. The NMEA 2000
network provides power to the marine instrument and data from
NMEA 2000-compatible 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.
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NOTICE
Item Description
Wind sensor
Marine instrument
Ignition or in-line switch
NMEA 2000 power cable
NMEA 2000 drop cable
12 Vdc 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.
• The installation instructions provided with your NMEA 0183
compatible device should contain the information you need to
identify the transmitting (Tx) A (+) and B (-) 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) 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 (+). This wire is used only when connecting the
marine instrument to a Garmin HVS GPS antenna.
White Tx/B (-). This wire is used only when connecting the
marine instrument to a Garmin HVS GPS antenna.
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