Preamble (Intendend Application and Limitations on Use)

The NMEA 0183 standard is intendend to support one-way serial data transmission from a SINGLE TALKER to one or more LISTENERS. The data transmited is human readable because is in ASCII and the data includes information such as: position, speed, depth, frequency, allocation, altitude, course, etc… And the instruments which can “speak” in NMEA can be GPS, Weather, Sounder, Heading, Velocity, Randar and others. A typical message in ACII mode might be 11 to a maximum of 79 characters in length and generally require transmission no more often than once per 20 mili-seconds.

The eletronical definitions in this standard are intended to operate at 38.4K-baud, a higher data rate than 4800-baud NMEA 0183.

IMPORTANT: Since there is no provision of guaranteed delivery of messages and only limited error-checking capability, this standard should be used with caution in crtical applications.

Just to understand:

1 – TALKER: Is any device that sends data to other devices within NMEA standard. We can indentify the type of talker by the 2-character mnemonic.

Some of these 2-character mnemonic can be for example:

Heading Track Controller (Autopilot) General AG*
Magnetic AP
Automatic Indentification System AI
COMUNICATIONS: Digital Selective Calling (DSC) CD*
Data Receiver CR
Satellite CS*
Radio-Telephone (MF/HF) CT*
Radio-Telephone (VHF) CV*
Scanning Receiver CX*

DECCA Navigator DE
Direction Finder DF*
Eletronic Chart System (ECS) EC
Eletronic Chart Display & Information System (ECDIS) EI
Emergency Position Indicating Beacon (EPIRB) EP*
Engine room Monitoring Systems ER
GLONASS Receiver GL
Global Navigation Satellite System (GNSS) GN
Global Positioning System (GPS) GP
HEADING SENSORS: Compass, Magnetic HC*
Gyro, North Seeking HE*
Gyro, Non-North Seeking HN

Integrated Instrumetation II
Integrated Navigation IN
Loran C LC
Propietary Code P
Radar and/or Radar Plotting RA*
Sounder, depth SD*
Eletronic Positioning System, other/general SN
Sounder, scanning SS
Turn Rater Indicator TI*
VELOCITY SENSORS: Doppler, onther/general VD*
Speed Log, Water, Magnetic VM
Speed Log, Water, Mechanical VW
Voyage Data Recorder VR
Transducer YX
TIMEKEEPERS, TIME/DATE: Atomic Clock ZA
Chronometer ZC
Quartz ZQ
Radio Update ZV
Weather Instruments WI

*Designated by IEC for use with IMO maritime eletronic devices. This is the minimum requirement for equipment that is required by IMO in the SOLAS Convention (1974, as amended).

2 – LISTENER: is any device that receives data from another device within the NMEA standard.

Thats it, for now.
References:

Nmea Publications, NMEA 0183-HS 38.4 K Baud Serial Data Standard For Interfacing Marine Eletronic Devices, Version 1.01, November 1, 2002

Nmea 0183 Standard For Interfacing Marine Eletronics Devices, Version 3.01, January 1, 2002

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