Raymarine A50 Installation Instructions Manual page 15

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SeaTalk
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SeaTalk (New Generation) is an onboard network utilizing a back-
bone cable running through the boat. Drop cables go from T
connectors in the backbone up to individual instruments. Devices
that have a low draw can be powered from the network.
NMEA 0183
The NMEA 0183 Data Interface Standard was developed by the
National Marine Electronics Association of America. It is an interna-
tional standard to enable equipment from many different
manufacturers to be connected together and share information.
The NMEA 0183 standard carries similar information to SeaTalk.
However it has the important difference that one cable will only carry
information in one direction. For this reason NMEA 0183 is generally
used to connect a data receiver and a transmitter together, e.g. a
compass sensor transmitting heading to a radar display.
This information is passed in 'sentences', each of which has a three
letter sentence identifier. It is therefore important when checking
compatibility between items that the same sentence identifiers are
used some examples of which are:
• VTG - carries Course and Speed Over Ground data.
• GLL - carries latitude and longitude.
• DBT - carries water depth.
• MWV - carries relative wind angle and wind speed data.
NMEA 2000
NMEA 2000 offers significant improvements over NMEA 0183, most
notably in speed and connectivity. Up to 50 units can simultaneously
transmit and receive on a single physical bus at any one time, with
each node being physically addressable.
Chapter 2: Planning the installation
The standard was specifically intended to allow for a whole network
of marine electronics from any manufacturer to communicate on a
common bus via standardized message types and formats.
See also
For a list of NMEA message types supported, refer to
sages on page 54.
NMEA Mes-
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