IEC 61162-2:2024

IEC 61162-2 ®
Edition 2.0 2024-04
COMMENTED VERSION
INTERNATIONAL
STANDARD
colour
inside
Maritime navigation and radiocommunication equipment and systems –
Digital interfaces –
Part 2: Single talker and multiple listeners, high-speed transmission
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IEC 61162-2 ®
Edition 2.0 2024-04
COMMENTED VERSION
INTERNATIONAL
STANDARD
colour
inside
Maritime navigation and radiocommunication equipment and systems –
Digital interfaces –
Part 2: Single talker and multiple listeners, high-speed transmission
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 47.020.70 ISBN 978-2-8322-8713-2
– 2 – IEC 61162-2:2024 CMV © IEC 2024
CONTENTS
FOREWORD .4
1 General .
1 Scope .6
2 Normative references .6
3 Terms, definitions and abbreviated terms .7
3.1 Terms and definitions .7
3.2 Abbreviated terms .7
4 Manufacturer's documentation .7
4.1 Standard documents .7
4.2 Additional information .8
5 Hardware specification .8
5.1 General .8
5.2 Interconnecting wires .8
5.3 Conductor definitions .8
5.4 Electrical connection/shield requirements .8
5.5 Connector .9
5.6 Electrical signal characteristics .9
5.6.1 Signal state definitions. 10
5.6.2 Talker drive circuits . 10
5.6.3 Listener receive circuits . 10
5.6.4 Electrical isolation . 10
5.6.5 Maximum voltage on the bus . 10
6 Data transmission . 10
7 Data format protocol. 11
5.1 Characters .
5.2 Fields .
5.3 Sentences .
5.4 Error detection and handling .
8 Data content . 16
9 Applications . 16
10 Methods of testing and required test results . 16
10.1 Test preparation . 16
10.1.1 General . 16
10.1.2 Testing under ambient conditions . 16
10.2 Test sequence . 16
10.3 Standard test signals . 16
10.4 Test of the interface . 17
10.4.1 Electrical test of the interface . 17
10.4.2 Protocol test of input and output. 17
10.4.3 Test under maximum interface workload . 17
Annex A (informative) IMO resolutions and ITU recommendations and relevant
IEC/ISO standards to which this standard applies for maritime navigation and
radiocommunication equipment and systems.
Annex B (informative) Glossary .
Bibliography . 28
List of comments . 29

Figure 1 – Talker/listener connections.8
Figure 2 – Cables – Electrical shield requirements .9
Figure 3 – Data transmission format . 10

Table A.1 – Navigation .
Table A.2 – Radiocommunications for the global maritime distress and safety system
(GMDSS) .

– 4 – IEC 61162-2:2024 CMV © IEC 2024
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MARITIME NAVIGATION AND RADIOCOMMUNICATION
EQUIPMENT AND SYSTEMS – DIGITAL INTERFACES –

Part 2: Single talker and multiple listeners,
high-speed transmission
FOREWORD
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This commented version (CMV) of the official standard IEC 61162-2:2024 edition 2.0
allows the user to identify the changes made to the previous IEC 61162-2:1998
edition 1.0. Furthermore, comments from IEC TC 80 experts are provided to explain the
reasons of the most relevant changes, or to clarify any part of the content.
A vertical bar appears in the margin wherever a change has been made. Additions are in
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This publication contains the CMV and the official standard. The full list of comments is
available at the end of the CMV.

IEC 61162-2 has been prepared by IEC technical committee 80: Maritime navigation and
radiocommunication equipment and systems. It is an International Standard.
This second edition cancels and replaces the first edition published in 1998. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) alternative hardware is given in 5.1 which may now be as specified in this document or as
specified in IEC 61162-1;
b) the data transmission rate given in Clause 6 is now configurable. The default remains as
38 400 (bits/s) but higher rates may be provided;
c) the description of the data format protocol has been removed as this information is given in
IEC 61162-1;
d) former Annex A and Annex B have been deleted as now of historic interest.
The text of this International Standard is based on the following documents:
Draft Report on voting
80/1065/CDV 80/1083/RVC
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

– 6 – IEC 61162-2:2024 CMV © IEC 2024
MARITIME NAVIGATION AND RADIOCOMMUNICATION
EQUIPMENT AND SYSTEMS – DIGITAL INTERFACES –

Part 2: Single talker and multiple listeners,
high-speed transmission
1 General
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 interface.
This document 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 can include any information
as specified by approved sentences or information coded according to the rules for proprietary
sentences. Typical messages may can be from 11 to a maximum of 79 characters in length and
generally require repetition rates up to once per 20 ms.
The electrical definitions in this document are intended to accommodate higher data rates than
are specified in IEC 61162-1. Since there is no provision for guaranteed delivery of messages
and only limited error-checking capability, it is important this document should be is used with
caution in all safety applications.
Annex A contains a list of relevant IMO resolutions and ITU recommendations to which this
standard applies. 1
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60945:1996, Maritime navigation and radiocommunication equipment and systems –
General requirements – Methods of testing and required test results
IEC 61162-1:1995, Maritime navigation and radiocommunication equipment and systems –
Digital interfaces – Part 1: Single talker and multiple listeners
ITU-T Recommendation X.27/V.11:1996, Electrical characteristics for balanced double-current
interchange circuits operating at data signalling rates up to 10 Mbits/s
NMEA 0183 – Version 2.30:1998, National marine electronics association (USA) – Standard for
interfacing marine electronic navigational devices 2
EIA 485:1991, Electrical characteristics of generators and receivers for use in balanced digital
multipoint systems 2
3 Terms, definitions and abbreviated terms
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 document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1 Terms and definitions
3.1.1
talker
any device which sends data to other devices
Note 1 to entry: The type of talker is identified by a two-character mnemonic as listed in IEC 61162-1.
3.1.2
listener
any device which receives data from another device
3.1.3
latency
time interval between an event and its resulting information, including time for processing,
transmission and/or reception
3.2 Abbreviated terms 3
EMC electromagnetic compatibility
EUT equipment under test
4 Manufacturer's documentation
4.1 Standard documents
Operator Installation manuals or other appropriate literature 4 provided for equipment that is
intended to meet the requirements of this document shall contain as a minimum the following
information:
a) identification of the A, B and common (C) signal lines (see Figure 1);
b) the output drive capability as a talker;
c) a list of approved sentences, noting unused fields, proprietary sentences transmitted as a
talker, data latency 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 by, or are acceptable to, 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;
i) list of supported baud rates (bits/s) including any limitations per each baud rate supported. 5

– 8 – IEC 61162-2:2024 CMV © IEC 2024
4.2 Additional information
As latency, filtering, error handling and data transmission interval can have a serious influence
on the performance of a system, the manufacturer shall give careful consideration to consider
these aspects. Documentation should include such data where applicable.
5 Hardware specification
5.1 General
One talker and multiple listeners may be connected in parallel over interconnecting wires.
Because of EMC requirements, shielded cables are recommended. The number of listeners
depends on the output capability, the input drive requirements of the connected devices, and
on the use of termination resistors.
Two alternatives apply for the hardware:
1) method based on 5.2 to 5.6;
2) method based on IEC 61162-1. 6
5.2 Interconnecting wires
Interconnection between devices may be by means of a shielded two-conductor twisted-pair
wire (A, B) plus any means to secure common signal ground potential (C) for transmitting and
receiving devices. For this purpose, a third wire additional to the twisted pair or the inner shield
of double-shielded cable with insulated shields may be used.

Figure 1 – Talker/listener connections
5.3 Conductor definitions
The conductors referred to in this document are the signal lines A, B, C (common) and shield.
5.4 Electrical connection/shield requirements
All signal and common line connections A, B and C are connected in parallel.

With single-shielded cables and a separate wire as common line C (signal ground), the shield
shall be connected to the talker chassis and shall not be connected to any listener. However,
the shield shall be continuous (unbroken) between all listeners – see Figure 1 and Figure 2 a).
With double-shielded cables and the inner shield used as common line C (signal ground), the
outer shield shall be connected to the talker chassis and shall not be connected to any listener.
However, the outer shield shall be continuous (unbroken) between all listeners – see Figure 1
and Figure 2 b).
With double-shielded cables and a separate wire as common line C (signal ground), the inner
shield shall be connected to the talker chassis and shall not be connected to any listener.
However, the inner shield shall be continuous (unbroken) between all listeners. The outer shield
may be connected to the chassis on either side if required – see Figure 1 and Figure 2 c).
The cabling shall be designed in a way that stubs are avoided or kept as short as possible. If
long cables are necessary, termination at the end of the line according to ITU-T
Recommendation X.27/V.11 shall be considered.

a) Single-shielded cable
b) Double-shielded cable
c) Double-shielded cable with separate wire
Figure 2 – Cables – Electrical shield requirements
5.5 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.
5.6 Electrical signal characteristics
This subclause describes the electrical characteristics of transmitters and receivers. 7

– 10 – IEC 61162-2:2024 CMV © IEC 2024
5.6.1 Signal state definitions
The idle, marking, logical 1, OFF or stop bit state is defined by a negative voltage on line A with
respect to line B, as in IEC 61162-1.
The active, spacing, logical 0, ON or start bit state is defined by a positive voltage on line A
with respect to line B, as in IEC 61162-1.
5.6.2 Talker drive circuits
No provision is made for more than a single talker to be connected to the bus. The drive circuit
shall meet, as a minimum, the requirements of ITU-T Recommendation X.27/V.11.
Improved and compatible driver circuits (e.g. EIA TIA-485) used in a compliant way are allowed.
5.6.3 Listener receive circuits
Multiple listeners may be connected to a single talker. The listener's receive circuit shall comply
with ITU-T Recommendation X.27/V.11. Optional termination resistors for the line shall be
provided. The input terminals A, B and C shall be electrically isolated from the remaining
electronics of the listening device. Reference is made to 5.6.4 and a sample circuit shown in
Figure 1.
5.6.4 Electrical isolation
Within a listener, there shall be no direct electrical connection between the signal lines A and
B, the signal ground C or the shield to ship's mains ground or power line. This isolation shall
be in accordance with IEC 60945.
5.6.5 Maximum voltage on the bus
The maximum applied voltage between signal lines A and B and between either line and
ground C shall be in accordance with ITU-T Recommendation X.27/V.11.
For protection against miswiring and for unintended connection to earlier talker designs, all
receive circuit devices shall be capable of withstanding 15 V between either signal lines A and
B and between either line and ground for an indefinite period.
6 Data transmission
Data is transmitted in serial asynchronous form in accordance with 1.2 IEC 61162-1 8. The first
bit is a start bit and is followed by data bits, least-significant-bit first as in Figure 3.

Figure 3 – Data transmission format
The following parameters are used:
– baud rate default and required is 38 400 (bits/s), higher baud rates are allowed based on
equipment configuration setup; 5
– data bits 8 (D7 = 0), parity none;
– stop bits 1.
7 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) of
IEC 61162-1. These characters are used for specific formatting purposes, such as sentence
and field delimiting, and 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)
of IEC 61162-1.
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.
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) of IEC 61162-1.
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) of IEC 61162-1. 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) of IEC 61162-1.
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.
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.

– 12 – IEC 61162-2:2024 CMV © IEC 2024
5.2.2 Data fields
Data fields in approved sentences follow a "," delimiter and contain valid characters in
accordance with the formats illustrated in 6.2 (table 6) of IEC 61162-1. Data fields in proprietary
sentences contain only valid characters 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.
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 alpha-numeric 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, 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) of IEC 61162-1.
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 any sentence. 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
$GPVTG,089.0,T,,,15.2,N,,*7F.
5.3 Sentences
This subclause describes the general structure of sentences. Details of specific sentence
formats are found in 6.3 of IEC 61162-1. Some sentences may specify restrictions beyond the
general limitations given in this part of this standard. Such restrictions may include defining
some fields as fixed length, numeric or text only, required to be non-null, transmitted with a
certain frequency, etc.
The maximum number of characters in a sentence shall be 82, consisting of a maximum of 79
characters between the starting delimiter "$" 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 "$" and end with the sentence
terminating delimiter .
5.3.1 Description of approved sentences
Approved sentences are those designed for general use and detailed in this standard. Approved
sentences are listed in 6.3 of IEC 61162-1 and shall be used wherever possible. Other
sentences, not recommended for new designs, may be found in practice. Such sentences are
listed in NMEA 0183. Information on such sentences may be obtained from NMEA (see 5.3.3).
An approved sentence contains, in the order shown, the following elements:
ASCII HEX Description
"$" 24 – start of sentence