IEC 61162-1:2000

Maritime navigation and radiocommunication equipment and systems - Digital interfaces - Part 1: Single talker and multiple listeners

Contains the requirements for data communication between maritime electronic instruments, navigation and radiocommunication equipment when interconnected via an appropriate system. Is intended to support one-way serial data transmission from a single talker to one or more listeners. Is closely aligned with NMEA 0183 version 2.30. Reference is made to IEC 61162-2 for applications with higher transmission rates.

General Information

• Status: Published
• Publication Date: 06-Jul-2000
• ICS: 33.060.01 - Radiocommunications in general
• ICS: 47.020.70 - Navigation and control equipment
• Technical Committee: TC 80 - Maritime navigation and radiocommunication equipment and systems
• Drafting Committee: WG 6 - TC 80/WG 6
• Current Stage: DELPUB - Deleted Publication
• Start Date: 11-Apr-2007
• Completion Date: 26-Oct-2025

Relations

• Revised: IEC 61162-1:2007 - Maritime navigation and radiocommunication equipment and systems - Digital interfaces - Part 1: Single talker and multiple listeners
• Effective Date: 05-Sep-2023

Overview

IEC 61162-1:2000 - "Maritime navigation and radiocommunication equipment and systems - Digital interfaces - Part 1: Single talker and multiple listeners" defines a widely used serial ASCII data interface for marine electronics. Closely aligned with NMEA 0183 v2.30, the standard specifies one-way, low-rate serial communication from a single talker to multiple listeners for exchanging navigation and radiocommunication data (position, speed, depth, heading, DSC, GNSS, etc.).

Key topics and technical requirements

• Single talker / multiple listeners model: One device transmits while one or more devices receive; talker type identified by a 2-character mnemonic.
• Data format: Printable ASCII sentences organized into characters, fields and sentences (typical length ~20–79 characters).
• Transmission rate: Generally no faster than one message per second; limited error checking - not intended for safety-critical guaranteed-delivery applications.
• Wiring and electrical:
  • Interconnect: two-conductor, shielded, twisted-pair (signal lines A and B plus shield).
  • Shielding: Listener shields should be connected to the talker chassis only.
  • Electrical signalling referenced to ITU‑T X.27/V.11 and related standards.
• Manufacturer documentation: Must include identification of A/B lines, talker output capability, list of approved sentences and transmission intervals, listener load requirements, connector/electrical details, and compliance/version data.
• Sentence sets and fields: Standard defines many maritime sentence types (GGA, RMC, GLL, DSC-related messages, heading/autopilot commands, GNSS fixes, wind, depth, text transmissions, etc.) and normative tests (Annex C).

Applications

IEC 61162-1 is ideal for low-bandwidth, interoperable shipboard data sharing between devices such as:

• GNSS/GPS receivers to chart plotters and autopilots
• Echo sounders and depth displays to navigation systems
• VHF/DSC transceivers to logging and control systems
• Heading sensors and autopilot interfaces It is not suitable for high-bandwidth applications (radar/video) - use IEC 61162-2 for high-speed serial interfaces.

Who uses this standard

• Marine electronics manufacturers and firmware developers
• Shipboard integrators and system installers
• Vessel automation and navigation system designers
• Regulatory and certification bodies ensuring interoperability
• Marine software vendors implementing NMEA/IEC sentence parsing

Related standards

• IEC 61162-2 - High-speed single talker / multiple listeners
• NMEA 0183 v2.30 - Closely aligned sentence set
• References: ITU‑R DSC recommendations, ISO/IEC 8859‑1, ITU‑T X.27/V.11

IEC 61162-1 remains a foundational, SEO-relevant specification for maritime digital interfaces enabling reliable, low-rate serial communication across marine navigation and radiocommunication equipment.

Standards Content (Sample)

INTERNATIONAL IEC
STANDARD
61162-1
Second edition
2000-07
Maritime navigation and radiocommunication
equipment and systems –
Digital interfaces –
Part 1:
Single talker and multiple listeners
Matériels et systèmes de navigation et
de radiocommunication maritimes –
Interfaces numériques –
Partie 1:
Emetteur unique et récepteurs multiples

Reference number
Numbering
As from 1 January 1997 all IEC publications are issued with a designation in the
60000 series.
Consolidated publications
Consolidated versions of some IEC publications including amendments are

available. For example, edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the
base publication, the base publication incorporating amendment 1 and the base

publication incorporating amendments 1 and 2.

Validity of this publication
The technical content of IEC publications is kept under constant review by the IEC,
thus ensuring that the content reflects current technology.
Information relating to the date of the reconfirmation of the publication is available
in the IEC catalogue.
Information on the subjects under consideration and work in progress undertaken
by the technical committee which has prepared this publication, as well as the list
of publications issued, is to be found at the following IEC sources:
• IEC web site*
•
Catalogue of IEC publications
Published yearly with regular updates
(On-line catalogue)*
• IEC Bulletin
Available both at the IEC web site* and as a printed periodical
Terminology, graphical and letter symbols
For general terminology, readers are referred to IEC 60050: International
Electrotechnical Vocabulary (IEV).
For graphical symbols, and letter symbols and signs approved by the IEC for
general use, readers are referred to publications IEC 60027: Letter symbols to be
used in electrical technology, IEC 60417: Graphical symbols for use on equipment.
Index, survey and compilation of the single sheets and IEC 60617: Graphical symbols
for diagrams.
* See web site address on title page.

INTERNATIONAL IEC
STANDARD
61162-1
Second edition
2000-07
Maritime navigation and radiocommunication
equipment and systems –
Digital interfaces –
Part 1:
Single talker and multiple listeners
Matériels et systèmes de navigation et
de radiocommunication maritimes –
Interfaces numériques –
Partie 1:
Emetteur unique et récepteurs multiples

 IEC 2000  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission 3, rue de Varembé Geneva, Switzerland
Telefax: [phone] e-mail: [e-mail] IEC web site http://www.iec.ch
Commission Electrotechnique Internationale
PRICE CODE
XC
International Electrotechnical Commission
For price, see current catalogue

– 2 – 61162-1 © IEC:2000(E)
CONTENTS
Page
FOREWORD . 3

INTRODUCTION .5

Clause
1 General. 6

1.1 Scope . 6
1.2 Normative references. 6
1.3 Definitions. 7
2 Manufacturer's documentation. 7
3 Hardware specification . 8
3.1 Interconnecting wire . 8
3.2 Conductor definitions . 8
3.3 Electrical connections/shield requirements . 8
3.4 Connector . 8
3.5 Electrical signal characteristics. 8
4 Data transmission . 9
5 Data format protocol. 10
5.1 Characters . 10
5.2 Fields. 11
5.3 Sentences. 12
6 Data content . 16
6.1 Character definitions . 16
6.2 Field definitions. 19
6.3 Approved sentences. 22
7 Applications .55
7.1 Example sentence. 55
7.2 Examples of receiver diagrams . 58
Annex A (informative) Minimum required sentences for equipment with digital interfaces
conforming to IMO resolutions and ITU recommendations and their association with
the relevant IEC and ISO standards . 59

Annex B (informative) Glossary . 63
Annex C (normative) Guidelines for methods of testing and required test results . 70
Bibliography . 76

61162-1 © IEC:2000(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION

___________
MARITIME NAVIGATION AND RADIOCOMMUNICATION

EQUIPMENT AND SYSTEMS –
DIGITAL INTERFACES –
Part 1: Single talker and multiple listeners

FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization
for Standardization (ISO) in accordance with conditions determined by agreement between the two
organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61162-1 has been prepared by IEC technical committee 80:
Maritime navigation and radiocommunication equipment and systems.
This second edition cancels and replaces the first edition published in 1995, and constitutes a
technical revision. This part of IEC 61162 is closely aligned with NMEA 0183 version 2.30.

The text of this standard is based upon the following documents:
FDIS Report on voting
80/240/FDIS 80/264/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 3.
Annex C forms an integral part of this standard.
Annexes A and B are for information only.

– 4 – 61162-1 © IEC:2000(E)
The committee has decided that the contents of this publication will remain unchanged until

2004. At this date, the publication will be

• reconfirmed;
• withdrawn;
• replaced by a revised edition, or

• amended.
61162-1 © IEC:2000(E) – 5 –
INTRODUCTION
IEC TC 80 interface standards are developed with input from manufacturers, private and

government organisations and equipment operators. The information contained in this standard

is intended to meet the needs of users at the time of publication, but users must recognise that

as applications and technology change, interface standards must change as well. Users of this

document are advised to immediately inform the IEC of any perceived inadequacies in this

standard.
The following notes provide the background to changes introduced to the first edition of this

standard.
NOTE 1 The sentences in IEC 61162-1:1995-11 which were indicated as “(to be further developed)” have now
been developed. The sentences involved are:
DSC – Digital selective calling (DSC) (see also DSE, DSI and DSR)
DTM – Datum reference
ASD – Autopilot system data has been deleted and renamed in line with IMO definitions – see HTC and HTD below.
NOTE 2 New sentences have been added:
ACK Acknowledge alarm
ALR Set alarm state
DSE Expanded digital selective calling
DSI DSC transponder initiate
DSR DSC transponder response
GNS GNSS fix data
HMS Heading monitor set
HMR Heading monitor receive
HTC Heading/track control command
HTD Heading/track control data
MLA GLONASS almanac data
MWD Wind direction and speed
TLB Target label
TXT Text transmission
NOTE 3 The following sentences have been deleted, as the systems referred to are no longer in operation:
GXA – TRANSIT position, OLN – OMEGA lane numbers, TRF – TRANSIT fix data.
NOTE 4 Detailed modifications have been made to the following sentences:
FSI, GBS, GGA, GRS, MSK, MSS, OSD, RMA, RMB, RMC, SFI, TLL, TTM, VBW, XDR and ZDA.
Details of the changes are given in the relevant pages.
NOTE 5 A mode indicator character field “a” has been added as a new last data field to specific sentences,
namely APB, BWC, BWR, GLL, RMA, RMB, RMC, VTG, WCV and XTE.
The mode indicator character “a” has been defined to include the following when used in the designated sentences:
A = Autonomous mode
D = Differential mode
E = Estimated (dead reckoning) mode
M = Manual input mode
S = Simulator mode
N = Data not valid
NOTE 6 A note has been added to sentences APB, GLL, RMA, RMB, RMC and XTE (which contain a status field
“A”) as follows:
“Note: the mode indicator field supplements the status field (field n), the status field shall be set to V = Invalid for
all values of mode indicator except for A = Autonomous and D = Differential.”
NOTE 7 A note has been added to all appropriate sentences to state that “the quality indicator, mode indicator,
operating mode and status fields shall not be null fields.”

– 6 – 61162-1 © IEC:2000(E)
MARITIME NAVIGATION AND RADIOCOMMUNICATION

EQUIPMENT AND SYSTEMS –
DIGITAL INTERFACES –
Part 1: Single talker and multiple listeners

1 General
1.1 Scope
This part of IEC 61162 contains the requirements for data communication between maritime
electronic instruments, navigation and radiocommunication equipment when interconnected via
an appropriate system.
This standard is intended to support one-way serial data transmission from a single talker to
one or more listeners. This data is in printable ASCII form and may include information such as
position, speed, depth, frequency allocation, etc. Typical messages may be from about 20 to a
maximum of 79 characters in length and generally require transmission no more rapidly than
one message per second.
The electrical definitions in this standard are not intended to accommodate high-bandwidth
applications such as radar or video imagery, or intensive database or file transfer applications.
Since there is no provision for guaranteed delivery of messages and only limited error checking
capability, this standard should be used with caution in all safety applications.
For applications where a faster transmission rate is necessary, reference should be made to
IEC 61162-2.
Annex A contains a list of relevant International Maritime Organization (IMO) resolutions and
International Telecommunication Union (ITU) recommendations to which this standard applies.
1.2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this part of IEC 61162. For dated references, subsequent amendments
to, or revisions of, any of these publications do not apply. However, parties to agreements
based on this part of IEC 61162 are encouraged to investigate the possibility of applying the
most recent editions of the normative documents indicated below. For undated references, the

latest edition of the normative document referred to applies. Members of IEC and ISO maintain
registers of currently valid International Standards.
Maritime navigation and radiocommunication equipment and systems –
IEC 61162-2:1998,
Digital interfaces – Part 2: Single talker and multiple listeners, high-speed transmission
ISO/IEC 8859-1:1998, Information technology – 8-bit single-byte coded graphic character sets
– Part 1: Latin alphabet No.1
ITU-R M.493-9:1997, Digital selective-calling system for use in the maritime mobile service
ITU-R M.821-1:1997, Optional expansion of the digital selective-calling system for use in the
maritime mobile service
61162-1 © IEC:2000(E) – 7 –
ITU-R M.825-3:1998, Characteristics of a transponder system using digital selective calling

techniques for use with vessel traffic services and ship-to-ship identification

ITU-T X.27/V.11:1996, Electrical characteristics for balanced double-current interchange

circuits operating at data signalling rates up to 10 Mbit/s

NMEA 0183:1998, National Marine Electronics Association (USA) – Standard for interfacing

marine electronic devices, version 2.30

RTCM:1998, RTCM (Radio Technical Commission for Maritime Services) SC-104

Recommended standards for differential GNSS (Global Navigation Satellite Systems) service,

version 2.2
IHO:1994, Special publication No. 60, User’s handbook on datum transformations involving
WGS 84
GLONASS:1995, Interface control document
Rockwell International Corporation ICD-GPS-200:1987, Interface control document, Navstar
GPS space segment/navigation user interface
1.3 Definitions
Common terms are defined in the glossary of annex B. Where there is a conflict, terms shall be
interpreted wherever possible in accordance with the references in 1.2.
For the purposes of this part of IEC 61162, the following definitions apply.
talker
any device which sends data to other devices. The type of talker is identified by a 2-character
mnemonic as listed in 6.2 (Table 4)
listener
any device which receives data from another device
2 Manufacturer's documentation
Operator manuals or other appropriate literature provided for equipment that is intended to
meet the requirements of this standard shall contain the following information:

a) identification of the A and B signal lines;
b) the output drive capability as a talker;
c) a list of approved sentences, noting unused fields, proprietary sentences transmitted as a
talker and transmission interval for each sentence;
d) the load requirements as a listener;
e) a list of sentences and associated data fields that are required as a listener;
f) the current software and hardware revision if this is relevant to the interface;
g) an electrical description or schematic of the listener/talker input/output circuits citing actual
components and devices used, including connector type and part number;
h) the version number and date of update of the standard for which compliance is sought.

– 8 – 61162-1 © IEC:2000(E)
3 Hardware specification
One talker and multiple listeners may be connected in parallel over an interconnecting wire.

The number of listeners depends on the output capability and input drive requirements of

individual devices.
3.1 Interconnecting wire
Interconnection between devices may be by means of a two-conductor, shielded, twisted-pair

wire.
3.2 Conductor definitions
The conductors referred to in this standard are the signal lines A and B, and shield.
3.3 Electrical connections/shield requirements
All signal line A connections are connected in parallel with all device A connections and all
signal line B connections are connected in parallel with all device B connections. The shields of
all listener cables should be connected to the talker chassis only and should not be connected
at each listener.
3.4 Connector
No standard connector is specified. Wherever possible readily available commercial
connectors shall be used. Manufacturers shall provide means for user identification of the
connections used.
3.5 Electrical signal characteristics
This subclause describes the electrical characteristics of transmitters and receivers.
3.5.1 Signal state definitions
The idle, marking, logical 1, OFF or stop bit states are defined by a negative voltage on line A
with respect to line B.
The active, spacing, logical 0, ON or start bit states are defined by a positive voltage on line A
with respect to line B.
It should be noted that the above A with respect to B levels are inverted from the voltage
input/output requirements of standard UARTs and that many line drivers and receivers provide

a logic inversion.
3.5.2 Talker drive circuits
No provision is made for more than a single talker to be connected to the bus. The drive circuit
used to provide the signal A and the return B shall meet, as a minimum, the requirements of
ITU-T X.27/V.11.
3.5.3 Listener receive circuits
Multiple listeners may be connected to a single talker. The listener receive circuit shall consist
of an opto-isolator and shall have protective circuits to limit current, reverse bias and power
dissipation at the opto-diode as shown in figure 1. Reference is made to example circuits
in 7.2.
61162-1 © IEC:2000(E) – 9 –
The receive circuit shall be designed for operation with a minimum differential input voltage of

1)
2,0 V and shall not take more than 2,0 mA from the line at that voltage.

A
Protective
circuits
B
Opto-isolator
Listener No. 2
A A
Protective
circuits
B B
Opto-isolator
Shields
Listener No. 1
Talker
IEC  910/2000
Figure 1 – Listener receive circuit
3.5.4 Electrical isolation
Within a listener there shall be no direct electrical connection between the signal line A, return
line B, or shield and ships' ground or power. Isolation from ships’ ground is required.
3.5.5 Maximum voltage on bus
The maximum applied voltage between signal lines A and B and between either line and
ground shall be in accordance with ITU-T X.27/V.11.
For protection against mis-wiring and for use with earlier talker designs, all receive circuit
devices shall be capable of withstanding 15 V between signal lines A and B and between either
line and ground for an indefinite period.
4 Data transmission
Data is transmitted in serial asynchronous form in accordance with the standards referenced in
2.1. The first bit is a start bit and is followed by data bits, least-significant-bit first, as illustrated
by figure 2.
The following parameters are used:
– baud rate 4 800;
– data bits 8 (D7 = 0), parity none;
– stop bits 1.
___________
1)
For reasons of compatibility with equipment designed to comply with earlier versions of NMEA 0183, it is noted
that the idle, marking, logical "1", OFF or stop bit state had previously been defined to be in the range –15,0 V to
+0,5 V. The active, spacing, logical "0", ON or start bit state was defined to be in the range +4,0 V to +15,0 V
while sourcing was not less than 15 mA.

– 10 – 61162-1 © IEC:2000(E)
D0    D1   D2    D3    D4   D5   D6   D7

Data bits Stop bit
Start bit
IEC  911/2000
Figure 2 – Data transmission format
5 Data format protocol
5.1 Characters
All transmitted data shall be interpreted as ASCII characters. The most significant bit of the
eight-bit character shall always be transmitted as zero (D7 = 0).
5.1.1 Reserved characters
The reserved character set consists of those ASCII characters shown in 6.1 (Table 1). These
characters are used for specific formatting purposes, such as sentence and field delimiting,
and except for code delimiting, shall not be used in data fields.
5.1.2 Valid characters
The valid character set consists of all printable ASCII characters (HEX 20 to HEX 7E) except
those defined as reserved characters. The list of the valid character set is given in 6.1
(Table 2).
5.1.3 Undefined characters
ASCII values not specified as either “reserved characters” or “valid characters” are excluded
and shall not be transmitted at any time.
When it is necessary to communicate an 8-bit character defined by ISO/IEC 8859-1 that is a
reserved character (Table 1) or not listed in Table 2 as a valid character (e.g. in a proprietary
sentence or text sentence), three characters shall be used.

The reserved character “^“ (HEX 5E) is followed by two ASCII characters (0-9, A-F)
representing the HEX value of the character to be communicated. For example:
– to send heading as "127.5°", transmit “127.5 ^F8”;
– to send the reserved characters , transmit “^0D^0A”;
– to send the reserved character "^", transmit “^5E”.
5.1.4 Character symbols
When individual characters are used in this standard to define units of measurement, to
indicate the type of data field, type of sentence, etc. they shall be interpreted according to the
character symbol in 6.1 (Table 3).

61162-1 © IEC:2000(E) – 11 –
5.2 Fields
A field consists of a string of valid characters, or no characters (null field), located between two

appropriate delimiter characters.

5.2.1 Address field
An address field is the first field in a sentence and follows the "$" delimiter; it serves to define
the sentence. Characters within the address field are limited to digits and upper case letters.
The address field shall not be a null field. Only sentences with the following three types of

address fields shall be transmitted.

5.2.1.1 Approved address field
Approved address fields consist of five characters defined by this standard. The first two
characters are the talker identifier, listed in 6.2 (Table 4). The talker identifier serves to define
the nature of the data being transmitted.
Devices that have the capability to transmit data from multiple sources shall transmit the
appropriate talker identifier (e.g., a device with both a GPS receiver and a Loran-C receiver
shall transmit GP when the position is GPS-based, LC when the position is Loran-C-based, and
IN for integrated navigation shall be used if lines of position from Loran-C and GPS are
combined into a position fix).
Devices capable of re-transmitting data from other sources shall use the appropriate identifier
(e.g. GPS receivers transmitting heading data shall not transmit $GPHCD unless the compass
heading is actually derived from the GPS signals).
The next three characters form the sentence formatter used to define the format and the type
of data. A list of approved sentence formatters is given in 6.2 (Table 5).
5.2.1.2 Query address field
The query address field consists of five characters and is used for the purpose of requesting
transmission of a specific sentence on a separate bus from an identified talker.
The first two characters are the talker identifier of the device requesting data, the next two
characters are the talker identifier of the device being addressed and the final character is the
query character Q.
5.2.1.3 Proprietary address field
The proprietary address field consists of the proprietary character P followed by a

three-character manufacturer's mnemonic code, used to identify the talker issuing a proprietary
sentence, and any additional characters as required. A list of valid manufacturer's mnemonic
codes may be obtained from NMEA (see 5.3.3).
5.2.2 Data fields
Data fields in approved sentences follow a "," delimiter and contain valid characters (and code
delimiters “^”) in accordance with the formats illustrated in 6.2 (Table 6). Data fields in
proprietary sentences contain only valid characters and the delimiter characters “,” and “^”, but
are not defined by this standard.
Because of the presence of variable data fields and null fields, specific data fields shall only be
located within a sentence by observing the field delimiters ",". Therefore, it is essential for the
listener to locate fields by counting delimiters rather than counting the total number of
characters received from the start of the sentence.

– 12 – 61162-1 © IEC:2000(E)
5.2.2.1 Variable length fields

Although some data fields are defined to have fixed length, many are of variable length in order

to allow devices to convey information and to provide data with more or less precision,

according to the capability or requirements of a particular device.

Variable length fields may be alphanumeric or numeric fields. Variable numeric fields may

contain a decimal point and may contain leading or trailing zeros.

5.2.2.2 Data field types
Data fields may be alpha, numeric, alphanumeric, variable length, fixed length or fixed/ variable
(with a portion fixed in length while the remainder varies). Some fields are constant, with their
value dictated by a specific sentence definition. The allowable field types are summarized in
6.2 (Table 6).
5.2.2.3 Null fields
A null field is a field of length zero, i.e. no characters are transmitted in the field. Null fields
shall be used when the value is unreliable or not available.
For example, if heading information were not available, sending data of "000" is misleading
because a user cannot distinguish between "000" meaning no data and a legitimate heading of
"000". However, a null field, with no characters at all, clearly indicates that no data is being
transmitted.
Null fields with their delimiters can have the following appearance depending on where they are
located in the sentence:
",,"  ",*"
The ASCII NULL character (HEX 00) shall not be used as the null field.
5.2.3 Checksum field
A checksum field shall be transmitted in all sentences. The checksum field is the last field in a
sentence and follows the checksum delimiter character "*". The checksum is the eight-bit
exclusive OR (no start or stop bits) of all characters in the sentence, including "," delimiters,
between but not including the "$" and the "*" delimiters.
The hexadecimal value of the most significant and least significant four bits of the result is
converted to two ASCII characters (0-9, A-F) for transmission. The most significant character is

transmitted first.
Examples of the checksum field are:
$GPGLL,5057.970,N,00146.110,E,142451,A*27 and
$GPVTG,089.0,T,,,15.2,N,,*7F .
5.3 Sentences
This subclause describes the general structure of sentences. Details of specific sentence
formats are found in 6.3. Some sentences may specify restrictions beyond the general
limitations given in this part of this standard. Such restrictions may include defining some fields
as fixed length, numeric or text only, required to be non-null, transmitted with a certain
frequency, etc.
61162-1 © IEC:2000(E) – 13 –
The maximum number of characters in a sentence shall be 82, consisting of a maximum of 79

characters between the starting delimiter "$" and the terminating delimiter .

The minimum number of fields in a sentence is one (1). The first field shall be an address field

containing the identity of the talker and the sentence formatter which specifies the number of

data fields in the sentence, the type of data they contain and the order in which the data fields

are transmitted. The remaining portion of the sentence may contain zero or multiple data fields.

The maximum number of fields allowed in a single sentence is limited only by the maximum

sentence length of 82 characters. Null fields may be present in the sentence and shall always

be used if data for that field is unavailable.

All sentences begin with the sentence-starting delimiter character "$" and end with the
sentence-terminating delimiter .
5.3.1 Description of approved sentences
Approved sentences are those designed for general use and detailed in this standard.
Approved sentences are listed in 6.3 and shall be used wherever possible. Other sentences,
not recommended for new designs, may be found in practice. Such sentences are listed in
NMEA 0183. Information on such sentences may be obtained from the National Marine
Electronics Association (NMEA)(USA).
An approved sentence contains, in the order shown, the following elements:
ASCII HEX Description
"$" 24 – start of sentence

– talker identifier and sentence formatter
["," ] – zero or more data fields
["," ]
"*" – checksum field
0D 0A – end of sentence
5.3.1.1 Approval sentence structure
The following provides a summary explanation of the approved sentence structure:
$aaccc, c---c*hh
ASCII HEX Description
"$" 24 Start of sentence: starting delimiter
aaccc Address field: alphanumeric characters identifying type of talker,
and sentence formatter. The first two characters identify the
talker. The last three are the sentence formatter mnemonic code
identifying the data type and the string format of the successive
fields. Mnemonics will be used as far as possible to facilitate
read-outs by users.
"," 2C Field delimiter: starts each field except address and checksum
fields. If it is followed by a null field, it is all that remains to
indicate no data in a field.
– 14 – 61162-1 © IEC:2000(E)
c---c Data sentence block: follows address field and is a series of data

fields containing all of the data to be transmitted. Data field

sequence is fixed and identified by the third and subsequent

characters of the address field (the sentence formatter). Data

fields may be of variable length and are preceded by delimiters

",".
"*" 2A checksum delimiter: follows last data field of the sentence. It

indicates that the following two alpha-numeric characters show
the HEX value of the checksum.

hh Checksum field: the absolute value calculated by exclusive-
OR'ing the eight data bits (no start bits or stop bits) of each
character in the sentence between, but excluding, "$" and "*".
The hexadecimal value of the most significant and least
significant four bits of the result are converted to two ASCII
characters (0-9, A-F) for transmission. The most significant
character is transmitted first. The checksum field is required in all
cases.
0D 0A End of sentence: sentence terminating delimiter.
5.3.2 Query sentences
Query sentences are intended to request approved sentences to be transmitted in a form of
two-way communication. The use of query sentences implies that the listener shall have the
capability of being a talker with its own bus.
The approved query sentence contains, in the order shown, the following elements:
ASCII HEX Description
"$" 24 start of sentence
talker identifier of requester
talker identifier for device from which data is being requested
"Q" query character, identifies query address
"," data field delimiter
approved sentence formatter of data being requested
"*"  checksum field
0D 0A end of sentence
5.3.2.1 Reply to query sentence
The reply to a query sentence is the approved sentence that was requested. The use of query
sentences requires cooperation between the devices that are interconnected. A reply to a query
sentence is not mandatory and there is no specified time delay between the receipt of a query
and the reply.
61162-1 © IEC:2000(E) – 15 –
5.3.3 Proprietary sentences
These are sentences not included within this standard; these provide a means for

manufacturers to use the sentence structure definitions of this standard to transfer data which

does not fall within the scope of approved sentences. This will generally be for one of the

following reasons:
a) data is intended for another device from the same manufacturer, is device specific, and not

in a form or of a type of interest to the general user;

b) data is being used for test purposes prior to the adoption of approved sentences;

c) data is not of a type and general usefulness which merits the creation of an approved

sentence.
The manufacturers' reference list of mnemonic codes is a component of the equivalent
2)
specification NMEA 0183.
A proprietary sentence contains, in the order shown, the following elements:
ASCII HEX Description
"$" 24 start of sentence
"P" 50 proprietary sentence ID
manufacturer's mnemonic code (The NMEA secretariat
maintains the master reference list which comprises codes
registered and formally adopted by NMEA)
[] Manufacturer's data
"*” checksum field
0D 0A end of sentence
Proprietary sentences shall include checksums and conform to requirements limiting overall
sentence length. Manufacturer’s data fields shall contain only valid characters but may include
“^” and “,” for delimiting or as manufacturer’s data. Details of proprietary data fields are not
included in this standard and need not be submitted for approval. However, it is required that
such sentences be published in the manufacturer’s manuals for reference.
5.3.4 Valid sentences
Approved sentences, query sentences and proprietary sentences are the only valid sentences.
Sentences of any other form are non-valid and shall not be transmitted on the bus.
___________
2)
The NMEA Secretariat maintains the master reference list which comprises codes registered and formally
adopted by NMEA.
The address for the registration of manufacturer’s codes is:
NMEA 0183 Standards Committee Fax: [phone]
PO Box 3435 e-mail: [e-mail]
New Bern, NC 28564-3435 web site http://www.nmea.org
USA.
– 16 – 61162-1 © IEC:2000(E)
5.3.5 Sentence transmission timing

Frequency of sentence transmission when specified shall be in accordance with the approved

sentence definitions (see 6.3). When not specified, the rate shall be consistent with the basic

measurement or calculation cycle but generally not more frequently than once per second.

It is desirable that sentences be transmitted with minimum inter-character spacing, preferably

as a near continuous burst, but under no circumstance shall the time to complete the

transmission of a sentence be greater than 1 s.

5.3.6 Additions to approved sentences

In order to allow for improvements or additions, future revisions of this standard may modify
existing sentences by adding new data fields after the last data field but before the checksum
delimiter character "*" and checksum field. Listeners shall determine the end of the sentence
by recognition of "" and "*" rather than by counting field delimiters. The checksum
value shall be computed on all received characters between, but not including, "$" and "*"
whether or not the listener recognizes all fields.
6 Data content
6.1 Character definitions
Table 1 – Reserved characters
ASCII HEX DEC Description
0D 13 Carriage return
0A 10 Line feed – End of sentence delimiter
$ 24 36 Start of sentence delimiter
* 2A 42 Checksum field delimiter
, 2C 44 Field delimiter
! 21 33 Reserved for future use
\ 5C 92 Reserved for future use
^ 5E 94 Code delimiter for HEX representation of ISO 8859-1 (ASCII) characters
~ 7E 126 Reserved for future use

61162-1 © IEC:2000(E) – 17 –
Table 2 – Valid characters
ASCII HEX DEC ASCII HEX DEC ASCII HEX DEC

Space 20 32 @ 40 64 ` 60 96
Reserved 21 33 A 41 65 a 61 97

" 22 34 B 42 66 b 62 98
# 23 35 C 43 67 c 63 99
Reserved 24 36 D 44 68 d 64 100

% 25 37 E 45 69 e 65 101
& 26 38 F 46 70 f 66 102
' 27 39 G 47 71 g 67 103
( 28 40 H 48 72 h 68 104
) 29 41 I 49 73 i 69 105
Reserved 2A 42 J 4A 74 j 6A 106
+ 2B 43 K 4B 75 k 6B 107
Reserved 2C 44 L 4C 76 l 6C 108
- 2D 45 M 4D 77 m 6D 109
. 2E 46 N 4E 78 n 6E 110
/ 2F 47 O 4F 79 o 6F 111
0 30 48 P 50 80 p 70 112
1 31 49 Q 51 81 q 71 113
2 32 50 R 52 82 r 72 114
3 33 51 S 53 83 s 73 115
4 34 52 T 54 84 t 74 116
5 35 53 U 55 85 u 75 117
6 36 54 V 56 86 v 76 118
7 37 55 W 57 87 w 77 119
8 38 56 X 58 88 x 78 120
9 39 57 Y 59 89 y 79 121
: 3A 58 Z 5A 90 z 7A 122
; 3B 59 [ 5B 91 { 7B 123
< 3C 60 Reserved 5C 92  7C 124
= 3D 61 ] 5D 93 } 7D 125
> 3E 62 Reserved 5E 94 Reserved 7E 126
? 3F 63 _ 5F 95 Reserved 7F 127

– 18 – 61162-1 © IEC:2000(E)
Table 3 – Character symbol
A Status symbol; Yes; Data valid; Warning flag clear; Auto; Ampere

a Alphabet character variable A through Z or a through z

B Bar (pressure, 1 000 mb = 100 kPa(Pascal(Pa))),Bottom
C Celsius (Degrees); Course-up
c Valid character; Calculating

D Degrees (of arc)
E Error; East; Engine
F Fathoms (1 fathom equals 1,828 766 m)

f Feet (1 foot equals 0,304 79 m)

G Great circle; Green
g Good
H Compass heading; Head-up; Hertz; Humidity
h Hours; HEX number
I Inches (1 inch equals 0,0254 m)
J Input operation completed
K Kilometres; km/h
k Kilograms
L Left; Local; Lost target
l Latitude; Litres; l/s
M Metres; m/s; Magnetic; Manual; Cubic metres
m Minutes; message
N Nautical miles; Knots; North; North-up; Newtons
n Numeral; address
P Purple; Proprietary (only when following "$"); Position sensor; Per cent; Pascal
(pressure)
Q Query; Target-being-acquired
R Right; Rhumb line; Red; Relative; Reference; Radar tracking; revolutions/min (RPM)
S South; Statute miles (1 609,31 m); Statute miles/h; Shaft
s Seconds
T Time difference; True; Track; Tracked target
tTest
U Dead reckoning estimate
u Sign, if minus "-" (HEX 2D)
V Data invalid; No; Warning flag set; Manual; Volt
W West; Water; Wheelover
x Numeric character variable
y Longitude
ZTime
61162-1 © IEC:2000(E) – 19 –
6.2 Field definitions
Table 4 – Talker identifier mnemonics

Talker device Identifier
Heading/track controller (autopilot)  general *AG

magnetic AP
Automatic identification system A I

Communications: 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
Electronic chart systems (ECS) EC
Electronic chart display and information system (ECDIS) EI
Emergency position indicating radio beacon (EPIRB) *EP
Engine room monitoring systems ER
Global positioning system (GPS) GP
GLONASS receiver GL
Global navigation satellite system (GNSS) GN
Heading sensors: compass, magnetic *HC
gyro, north seeking *HE
gyro, non-north seeking HN
Integrated instrumentation II
Integrated navigation IN
LORAN: LORAN-C LC
Proprietary code P
Radar and/or radar plotting *RA
Sounder, depth *SD
Electronic positioning system, other/general SN
Sounder, scanning SS
Turn rate indicator *TI
*
Velocity sensors: Doppler, other/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 in this standard for use with IMO maritime electronic devices. This is the minimum requirement for
equipment that is required by IMO in the SOLAS Convention (1974, as amended).

– 20 – 61162-1 © IEC:2000(E)
Table 5 – Approved sentence formatters

Formatter Meaning
AAM Waypoint arrival alarm
ACK Acknowledgement alarm
ALM GPS almanac data
ALR Set alarm state
APB Heading/track controller (Autopilot) sentence B

BEC Bearing and distance to waypoint, dead reckoning

BOD Bearing, origin to destination

BWC Bearing and distance to waypoint
BWR Bearing and distance to waypoint, rhumb line
BWW Bearing, waypoint to waypoint
DBT Depth below transducer
DCN DECCA position
DPT Depth
DSC Digital selective calling information
DSE Expanded digital selective calling
DSI DSC transponder initialise
DSR DSC transponder response
DTM Datum reference
FSI Frequency set information
GBS GNSS Satellite fault detection
GGA Global positioning system fix data
GLC Geographic position, LORAN-C
GLL Geographic position, latitude/longitude
GNS GNSS fix data
GRS GNSS range residuals
GSA GNSS DOP and active satellites
GST GNSS pseudorange error statistics
GSV GNSS satellites in view
HDG Heading, deviation and variation
HDT Heading, true
HMR Heading monitor – receive
HMS Heading monitor – set
HSC Heading steering command
HTC Heading/track control command
HTD Heading/track control data
LCD LORAN-C signal data
MLA Glonass almanac data
MSK MSK receiver interface
MSS MSK receiver signal status
MTW Water temperature
MWD Wind direction and speed
MWV Wind speed and angle
OSD Own ship data
RMA Recommended minimum specific LORAN-C data
RMB Recommended minimum navigation information
RMC Recommended minimum specific GNSS data
ROT Rate of turn
RPM Revolutions
RSA Rudder sensor angle
RSD Radar system data
RTE Routes
SFI Scanning frequency information
STN Multiple data ID
TLB Target label
TLL Target latitude and longitude
TTM Tracked target message
61162-1 © IEC:2000(E) – 21 –
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