SIST EN 300 338-6 V1.3.1:2024

EUROPEAN STANDARD
Technical characteristics and methods of measurement
for equipment for generation, transmission
and reception of Digital Selective Calling (DSC)
in the maritime MF, MF/HF and/or VHF mobile service;
Part 6: Class M DSC
2 ETSI EN 300 338-6 V1.3.1 (2024-03)

Reference
REN/ERM-TGMAR-616
Keywords
DSC, GMDSS, maritime, radio, SAR

ETSI
650 Route des Lucioles
F-06921 Sophia Antipolis Cedex - FRANCE

Tel.: +33 4 92 94 42 00  Fax: +33 4 93 65 47 16

Siret N° 348 623 562 00017 - APE 7112B
Association à but non lucratif enregistrée à la
Sous-Préfecture de Grasse (06) N° w061004871

Important notice
The present document can be downloaded from:
https://www.etsi.org/standards-search
The present document may be made available in electronic versions and/or in print. The content of any electronic and/or
print versions of the present document shall not be modified without the prior written authorization of ETSI. In case of any
existing or perceived difference in contents between such versions and/or in print, the prevailing version of an ETSI
deliverable is the one made publicly available in PDF format at www.etsi.org/deliver.
Users of the present document should be aware that the document may be subject to revision or change of status.
Information on the current status of this and other ETSI documents is available at
https://portal.etsi.org/TB/ETSIDeliverableStatus.aspx
If you find errors in the present document, please send your comment to one of the following services:
https://portal.etsi.org/People/CommiteeSupportStaff.aspx
If you find a security vulnerability in the present document, please report it through our
Coordinated Vulnerability Disclosure Program:
https://www.etsi.org/standards/coordinated-vulnerability-disclosure
Notice of disclaimer & limitation of liability
The information provided in the present deliverable is directed solely to professionals who have the appropriate degree of
experience to understand and interpret its content in accordance with generally accepted engineering or
other professional standard and applicable regulations.
No recommendation as to products and services or vendors is made or should be implied.
In no event shall ETSI be held liable for loss of profits or any other incidental or consequential damages.

Any software contained in this deliverable is provided "AS IS" with no warranties, express or implied, including but not
limited to, the warranties of merchantability, fitness for a particular purpose and non-infringement of intellectual property
rights and ETSI shall not be held liable in any event for any damages whatsoever (including, without limitation, damages
for loss of profits, business interruption, loss of information, or any other pecuniary loss) arising out of or related to the use
of or inability to use the software.
Copyright Notification
No part may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm except as authorized by written permission of ETSI.
The content of the PDF version shall not be modified without the written authorization of ETSI.
The copyright and the foregoing restriction extend to reproduction in all media.

© ETSI 2024.
All rights reserved.
ETSI
3 ETSI EN 300 338-6 V1.3.1 (2024-03)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
1 Scope . 6
2 References . 6
2.1 Normative references . 6
2.2 Informative references . 7
3 Definition of terms, symbols and abbreviations . 7
3.1 Terms . 7
3.2 Symbols . 8
3.3 Abbreviations . 8
4 General requirements . 8
4.1 General . 8
4.2 Frequency of operation . 9
4.3 Class of emission . 9
4.4 Controls . 9
4.5 Indicators . 9
4.5.0 General . 9
4.5.1 Audible indicators . 9
4.5.2 Visual Indicators . 9
4.6 Labelling. 10
4.7 Self ID . 10
4.8 Own vessel MMSI . 10
4.9 Battery requirement . 10
5 DSC Operation . 11
5.1 Listen Before Talk (LBT) Protocol . 11
5.1.1 General . 11
5.1.2 Prioritized wait for class-M devices. 11
5.1.3 Active Mode Wait Period Calculation . 11
5.1.4 Test Mode Wait Period Calculation . 11
5.2 DSC messages . 11
5.2.1 Active mode . 11
5.2.1.1 General . 11
5.2.1.2 Inadvertent activation . 12
5.2.1.3 Closed loop operation . 12
5.2.1.4 Open loop operation . 12
5.2.1.5 Distress self-cancel. 13
5.2.2 Test mode. 13
5.3 Action on receipt of acknowledgment messages to alerts . 13
6 Internal electronic position fixing device . 13
Annex A (normative): AIS message bursts . 15
A.1 General . 15
A.2 Active mode . 15
A.3 Test mode . 16
A.4 Default message field values . 17
Annex B (informative): LBT and Prioritized Wait Algorithm . 18
B.1 Description of the algorithm . 18
B.2 Interruptions for AIS transmissions . 18
ETSI
4 ETSI EN 300 338-6 V1.3.1 (2024-03)
B.3 Analysis of the algorithm . 18
Annex C (informative): Change history . 20
History . 21

ETSI
5 ETSI EN 300 338-6 V1.3.1 (2024-03)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The declarations
pertaining to these essential IPRs, if any, are publicly available for ETSI members and non-members, and can be
found in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to
ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the
ETSI Web server (https://ipr.etsi.org/).
Pursuant to the ETSI Directives including the ETSI IPR Policy, no investigation regarding the essentiality of IPRs,
including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not
referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become,
essential to the present document.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
DECT™, PLUGTESTS™, UMTS™ and the ETSI logo are trademarks of ETSI registered for the benefit of its

Members. 3GPP™ and LTE™ are trademarks of ETSI registered for the benefit of its Members and of the 3GPP
Organizational Partners. oneM2M™ logo is a trademark of ETSI registered for the benefit of its Members and of the ®
oneM2M Partners. GSM and the GSM logo are trademarks registered and owned by the GSM Association.
Foreword
This European Standard (EN) has been produced by ETSI Technical Committee Electromagnetic compatibility and
Radio spectrum Matters (ERM).
The present document is part 6 of a multi-part deliverable. Full details of the entire series can be found in part 1 [i.1].

National transposition dates
Date of adoption of this EN: 26 February 2024
Date of latest announcement of this EN (doa): 31 May 2024
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 30 November 2024
Date of withdrawal of any conflicting National Standard (dow): 30 November 2025

Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
6 ETSI EN 300 338-6 V1.3.1 (2024-03)
1 Scope
The present document states the minimum requirements for devices using Digital Selective Calling (DSC) Class M, for
Man Overboard (MOB). The present document defines the requirements for equipment that uses DSC alerting and
signalling in the maritime mobile bands and particularly the GMDSS distress and safety channels. Such equipment is
not intended to provide any subsequent communications or telephony facilities.
The present document is part 6 of a multi-part deliverable that covers the channel access rules and technical
requirements applicable to these devices.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] Recommendation ITU-R M.493-15 (01/2019): "Digital selective-calling system for use in the
maritime mobile service".
[2] IEC EN 60945 (2002): "Maritime Navigation and Radiocommunication Equipment and Systems -
General Requirements - Methods of Testing and Required Test Results".
[3] Recommendation ITU-R M.585-9 (05/2022): "Assignment and use of identities in the maritime
mobile service".
[4] Recommendation ITU-R M.821-1 (02/1997): "Optional expansion of the digital selective-calling
system for use in the maritime mobile service".
[5] EN 61108-1: "Maritime navigation and radiocommunication equipment and systems - Global
navigation satellite systems (GNSS) - Part 1: Global positioning system (GPS) - Receiver
equipment - Performance standards, methods of testing and required test results", produced by
CENELEC.
[6] EN 61108-2: "Maritime navigation and radiocommunication equipment and systems - Global
navigation satellite systems (GNSS) - Part 2: Global navigation satellite system (GLONASS) -
Receiver equipment - Performance standards, methods of testing and required test results",
produced by CENELEC.
[7] EN 61108-3: "Maritime navigation and radiocommunication equipment and systems - Global
navigation satellite systems (GNSS) - Part 3: Galileo receiver equipment - Performance
requirements, methods of testing and required test results", produced by CENELEC.
[8] EN 61108-5: "Maritime navigation and radiocommunication equipment and systems - Global
navigation satellite systems (GNSS) - Part 5: BeiDou navigation satellite system (BDS) - Receiver
equipment - Performance requirements, methods of testing and required test results", produced by
CENELEC.
[9] Recommendation ITU-R M.1371-5 (02/2014): "Technical characteristics for an automatic
identification system using time division multiple access in the VHF maritime mobile frequency
band".
ETSI
7 ETSI EN 300 338-6 V1.3.1 (2024-03)
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI EN 300 338-1: "Technical characteristics and methods of measurement for equipment for
generation, transmission and reception of Digital Selective Calling (DSC) in the maritime MF,
MF/HF and/or VHF mobile service; Part 1: Common requirements".
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the terms given in ETSI EN 300 338-1 [i.1] and the following apply:
acknowledged: automated procedure which indicates that the objective of the initial DSC message has been achieved
activation: initial triggering of the MOB device i.e. both parts of the two step procedure are performed
active mode: activated mode, transmitting in an emergency situation
class M: specific class of DSC functionality for use by man overboard devices
closed loop: individual transmission to own vessel
default: value selected or an action taken by the equipment software in the absence of any operator input
distress alert: name given to the single distress DSC message with the format symbol 112
distress DSC message: DSC message or acknowledgement containing the distress information
distress information: symbols within a DSC message describing a distress situation consisting of the MMSI of the
vessel in distress, the nature of distress, the position of the vessel in distress, the UTC time of that position and the mode
of subsequent communication
F1D: direct frequency modulation of data (no subcarrier)
factory default: default value that is set by the manufacturer such that the field or behaviour is defined prior to any
operator intervention
G2B: indirect phase-modulation (frequency modulation with a pre-emphasis of 6 dB/octave)
information characters: set of symbols in a DSC message that contains the items of interest for the recipient and is
used to compute the ECC symbol that terminates the message
non distress DSC message: DSC messages or acknowledgements that do not have the format specifier or category of
"distress"
open loop: transmitting to all ships (broadcast) 'using All ships call types'
primary battery: non-rechargeable primary power source
symbol (as part of the DSC sentence): 7 binary bits of a 10 bit DSC word that have the information content
test mode: self-testing mode using an individual test call to own vessel
ETSI
8 ETSI EN 300 338-6 V1.3.1 (2024-03)
word (as part of the DSC sentence): 10 binary bits that make up the coded entities of a transmitted DSC message
NOTE: The 10 bits consist of a 7 bit "symbol" that gives the information content and 3 bit error check that gives
the number of 0 binary bits in the 7 bit symbol.
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AIS Automatic Identification System
CIRM Comité International Radio-Maritime
COG Course Over Ground
DSC Digital Selective Calling
ECC Error Check Character
EDS Expansion Data Specifier
EOS End Of Sequence
FM Frequency Modulation
GMDSS Global Maritime Distress and Safety System
GMSK Gaussian Minimum Shift Keying
GNSS Global Navigation Satellite System
GPS Global Positioning System
HF High Frequency
ID IDentity
ITU International Telecommunications Union
ITU-R ITU - Radiocommunications sector
LBT Listen Before Talk
MF Medium Frequency
MMSI Maritime Mobile Service Identity
MOB Man Overboard
MSLD Maritime Survivor Locating Device
PM Phase Modulation
RX Receiver
SOG Speed Over Ground
SOTDMA Self-Organized Time Division Multiple Access
TX Transmitter
UTC Universal Time Co-ordinated
VHF Very High Frequency
4 General requirements
4.1 General
Class M MOB devices are employed in situations of grave and imminent danger to persons that require immediate
assistance from other vessels or search and rescue services.
MOB devices shall be:
• Fitted with an internal electronic GNSS position fixing device.
• Fitted with a transceiver operating on VHF DSC channel 70.
• Fitted with an Automatic Identification System (AIS) transmitter operating in accordance with annex A to
provide radio location.
ETSI
9 ETSI EN 300 338-6 V1.3.1 (2024-03)
• Fitted with audio and visual indicators to designate operation of the MOB device, intrinsically safe MOB
devices shall be fitted with a minimum of visual indicators.
• Capable of manual activation and deactivation and optionally automatic activation (see clause 4.4).
4.2 Frequency of operation
The MOB device shall operate on 156,525 MHz (Channel 70), 161,975 MHz (AIS 1) & 162,025 MHz (AIS 2) only.
4.3 Class of emission
DSC: G2B Phase Modulation (PM) with digital information modulated on a sub-carrier.
AIS: F1D GMSK 9 600 baud.
4.4 Controls
The MOB device shall be initially activated by the use of two simple, but independent mechanical actions, neither of
which on its own shall activate the equipment. If the second mechanical action is replaced by an immersion sensor, then
the first mechanical action should be an arming or enabling function thus to ensure the MSLD is armed for automatic
activation when submerged.
It should only be possible to activate the equipment after a seal or other mechanical restraint has been removed from the
first mechanical action. After activation it shall be possible to de-activate the equipment and the means to deactivate the
equipment shall be clearly marked. It should be possible to determine that the equipment has been previously activated.
4.5 Indicators
4.5.0 General
The MOB device shall be provided with a visual and, with the exception of intrinsically safe MOB devices, audible
indications that designate the operation of the MOB device as specified in clauses 4.5.1 and 4.5.2.
4.5.1 Audible indicators
The audible indicator shall signal:
• When the MOB device is first activated.
• Prior to any DSC transmission.
4.5.2 Visual Indicators
The visual indicator shall clearly distinguish the following states:
• The MOB device has been activated and is transmitting in active mode.
• The MOB device has a GNSS position fix and is transmitting in active mode.
• The MOB device is undergoing test and is transmitting in test mode.
• The MOB device cannot complete a test because it could not obtain a GNSS position.
• The MOB device cannot complete a test because it has not been properly programmed with own vessel MMSI
(closed loop devices only).
• The MOB device has completed a test or has been deactivated locally.
ETSI
10 ETSI EN 300 338-6 V1.3.1 (2024-03)
• The MOB device has received a DSC acknowledgement and the DSC transmitter has been deactivated.
4.6 Labelling
The MOB device shall be provided with a label, or labels, permanently affixed to the exterior, containing the following
information:
• Self ID of the MOB device (see clause 4.7) and manufacturer serial number.
• Open loop devices shall be marked DSC-MOB-O.
• Closed loop devices shall be marked DSC-MOB-C.
• Adequate instructions to enable the equipment to be a
...

SLOVENSKI STANDARD
01-maj-2024
Tehnične karakteristike in merilne metode za naprave, ki generirajo, oddajajo in
sprejemajo digitalni selektivni klic (DSC) v pomorski mobilni storitvi, ki deluje v
območju MF, MF/HF oziroma VHF - 6. del: Digitalni selektivni klic razreda M
Technical characteristics and methods of measurement for equipment for generation,
transmission and reception of Digital Selective Calling (DSC) in the maritime MF, MF/HF
and/or VHF mobile service - Part 6: Class M DSC
Ta slovenski standard je istoveten z: ETSI EN 300 338-6 V1.3.1 (2024-03)
ICS:
33.060.20 Sprejemna in oddajna Receiving and transmitting
oprema equipment
47.020.70 Navigacijska in krmilna Navigation and control
oprema equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
Technical characteristics and methods of measurement
for equipment for generation, transmission
and reception of Digital Selective Calling (DSC)
in the maritime MF, MF/HF and/or VHF mobile service;
Part 6: Class M DSC
2 ETSI EN 300 338-6 V1.3.1 (2024-03)

Reference
REN/ERM-TGMAR-616
Keywords
DSC, GMDSS, maritime, radio, SAR

ETSI
650 Route des Lucioles
F-06921 Sophia Antipolis Cedex - FRANCE

Tel.: +33 4 92 94 42 00  Fax: +33 4 93 65 47 16

Siret N° 348 623 562 00017 - APE 7112B
Association à but non lucratif enregistrée à la
Sous-Préfecture de Grasse (06) N° w061004871

Important notice
The present document can be downloaded from:
https://www.etsi.org/standards-search
The present document may be made available in electronic versions and/or in print. The content of any electronic and/or
print versions of the present document shall not be modified without the prior written authorization of ETSI. In case of any
existing or perceived difference in contents between such versions and/or in print, the prevailing version of an ETSI
deliverable is the one made publicly available in PDF format at www.etsi.org/deliver.
Users of the present document should be aware that the document may be subject to revision or change of status.
Information on the current status of this and other ETSI documents is available at
https://portal.etsi.org/TB/ETSIDeliverableStatus.aspx
If you find errors in the present document, please send your comment to one of the following services:
https://portal.etsi.org/People/CommiteeSupportStaff.aspx
If you find a security vulnerability in the present document, please report it through our
Coordinated Vulnerability Disclosure Program:
https://www.etsi.org/standards/coordinated-vulnerability-disclosure
Notice of disclaimer & limitation of liability
The information provided in the present deliverable is directed solely to professionals who have the appropriate degree of
experience to understand and interpret its content in accordance with generally accepted engineering or
other professional standard and applicable regulations.
No recommendation as to products and services or vendors is made or should be implied.
In no event shall ETSI be held liable for loss of profits or any other incidental or consequential damages.

Any software contained in this deliverable is provided "AS IS" with no warranties, express or implied, including but not
limited to, the warranties of merchantability, fitness for a particular purpose and non-infringement of intellectual property
rights and ETSI shall not be held liable in any event for any damages whatsoever (including, without limitation, damages
for loss of profits, business interruption, loss of information, or any other pecuniary loss) arising out of or related to the use
of or inability to use the software.
Copyright Notification
No part may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm except as authorized by written permission of ETSI.
The content of the PDF version shall not be modified without the written authorization of ETSI.
The copyright and the foregoing restriction extend to reproduction in all media.

© ETSI 2024.
All rights reserved.
ETSI
3 ETSI EN 300 338-6 V1.3.1 (2024-03)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
1 Scope . 6
2 References . 6
2.1 Normative references . 6
2.2 Informative references . 7
3 Definition of terms, symbols and abbreviations . 7
3.1 Terms . 7
3.2 Symbols . 8
3.3 Abbreviations . 8
4 General requirements . 8
4.1 General . 8
4.2 Frequency of operation . 9
4.3 Class of emission . 9
4.4 Controls . 9
4.5 Indicators . 9
4.5.0 General . 9
4.5.1 Audible indicators . 9
4.5.2 Visual Indicators . 9
4.6 Labelling. 10
4.7 Self ID . 10
4.8 Own vessel MMSI . 10
4.9 Battery requirement . 10
5 DSC Operation . 11
5.1 Listen Before Talk (LBT) Protocol . 11
5.1.1 General . 11
5.1.2 Prioritized wait for class-M devices. 11
5.1.3 Active Mode Wait Period Calculation . 11
5.1.4 Test Mode Wait Period Calculation . 11
5.2 DSC messages . 11
5.2.1 Active mode . 11
5.2.1.1 General . 11
5.2.1.2 Inadvertent activation . 12
5.2.1.3 Closed loop operation . 12
5.2.1.4 Open loop operation . 12
5.2.1.5 Distress self-cancel. 13
5.2.2 Test mode. 13
5.3 Action on receipt of acknowledgment messages to alerts . 13
6 Internal electronic position fixing device . 13
Annex A (normative): AIS message bursts . 15
A.1 General . 15
A.2 Active mode . 15
A.3 Test mode . 16
A.4 Default message field values . 17
Annex B (informative): LBT and Prioritized Wait Algorithm . 18
B.1 Description of the algorithm . 18
B.2 Interruptions for AIS transmissions . 18
ETSI
4 ETSI EN 300 338-6 V1.3.1 (2024-03)
B.3 Analysis of the algorithm . 18
Annex C (informative): Change history . 20
History . 21

ETSI
5 ETSI EN 300 338-6 V1.3.1 (2024-03)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The declarations
pertaining to these essential IPRs, if any, are publicly available for ETSI members and non-members, and can be
found in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to
ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the
ETSI Web server (https://ipr.etsi.org/).
Pursuant to the ETSI Directives including the ETSI IPR Policy, no investigation regarding the essentiality of IPRs,
including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not
referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become,
essential to the present document.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
DECT™, PLUGTESTS™, UMTS™ and the ETSI logo are trademarks of ETSI registered for the benefit of its

Members. 3GPP™ and LTE™ are trademarks of ETSI registered for the benefit of its Members and of the 3GPP
Organizational Partners. oneM2M™ logo is a trademark of ETSI registered for the benefit of its Members and of the ®
oneM2M Partners. GSM and the GSM logo are trademarks registered and owned by the GSM Association.
Foreword
This European Standard (EN) has been produced by ETSI Technical Committee Electromagnetic compatibility and
Radio spectrum Matters (ERM).
The present document is part 6 of a multi-part deliverable. Full details of the entire series can be found in part 1 [i.1].

National transposition dates
Date of adoption of this EN: 26 February 2024
Date of latest announcement of this EN (doa): 31 May 2024
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 30 November 2024
Date of withdrawal of any conflicting National Standard (dow): 30 November 2025

Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
6 ETSI EN 300 338-6 V1.3.1 (2024-03)
1 Scope
The present document states the minimum requirements for devices using Digital Selective Calling (DSC) Class M, for
Man Overboard (MOB). The present document defines the requirements for equipment that uses DSC alerting and
signalling in the maritime mobile bands and particularly the GMDSS distress and safety channels. Such equipment is
not intended to provide any subsequent communications or telephony facilities.
The present document is part 6 of a multi-part deliverable that covers the channel access rules and technical
requirements applicable to these devices.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] Recommendation ITU-R M.493-15 (01/2019): "Digital selective-calling system for use in the
maritime mobile service".
[2] IEC EN 60945 (2002): "Maritime Navigation and Radiocommunication Equipment and Systems -
General Requirements - Methods of Testing and Required Test Results".
[3] Recommendation ITU-R M.585-9 (05/2022): "Assignment and use of identities in the maritime
mobile service".
[4] Recommendation ITU-R M.821-1 (02/1997): "Optional expansion of the digital selective-calling
system for use in the maritime mobile service".
[5] EN 61108-1: "Maritime navigation and radiocommunication equipment and systems - Global
navigation satellite systems (GNSS) - Part 1: Global positioning system (GPS) - Receiver
equipment - Performance standards, methods of testing and required test results", produced by
CENELEC.
[6] EN 61108-2: "Maritime navigation and radiocommunication equipment and systems - Global
navigation satellite systems (GNSS) - Part 2: Global navigation satellite system (GLONASS) -
Receiver equipment - Performance standards, methods of testing and required test results",
produced by CENELEC.
[7] EN 61108-3: "Maritime navigation and radiocommunication equipment and systems - Global
navigation satellite systems (GNSS) - Part 3: Galileo receiver equipment - Performance
requirements, methods of testing and required test results", produced by CENELEC.
[8] EN 61108-5: "Maritime navigation and radiocommunication equipment and systems - Global
navigation satellite systems (GNSS) - Part 5: BeiDou navigation satellite system (BDS) - Receiver
equipment - Performance requirements, methods of testing and required test results", produced by
CENELEC.
[9] Recommendation ITU-R M.1371-5 (02/2014): "Technical characteristics for an automatic
identification system using time division multiple access in the VHF maritime mobile frequency
band".
ETSI
7 ETSI EN 300 338-6 V1.3.1 (2024-03)
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI EN 300 338-1: "Technical characteristics and methods of measurement for equipment for
generation, transmission and reception of Digital Selective Calling (DSC) in the maritime MF,
MF/HF and/or VHF mobile service; Part 1: Common requirements".
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the terms given in ETSI EN 300 338-1 [i.1] and the following apply:
acknowledged: automated procedure which indicates that the objective of the initial DSC message has been achieved
activation: initial triggering of the MOB device i.e. both parts of the two step procedure are performed
active mode: activated mode, transmitting in an emergency situation
class M: specific class of DSC functionality for use by man overboard devices
closed loop: individual transmission to own vessel
default: value selected or an action taken by the equipment software in the absence of any operator input
distress alert: name given to the single distress DSC message with the format symbol 112
distress DSC message: DSC message or acknowledgement containing the distress information
distress information: symbols within a DSC message describing a distress situation consisting of the MMSI of the
vessel in distress, the nature of distress, the position of the vessel in distress, the UTC time of that position and the mode
of subsequent communication
F1D: direct frequency modulation of data (no subcarrier)
factory default: default value that is set by the manufacturer such that the field or behaviour is defined prior to any
operator intervention
G2B: indirect phase-modulation (frequency modulation with a pre-emphasis of 6 dB/octave)
information characters: set of symbols in a DSC message that contains the items of interest for the recipient and is
used to compute the ECC symbol that terminates the message
non distress DSC message: DSC messages or acknowledgements that do not have the format specifier or category of
"distress"
open loop: transmitting to all ships (broadcast) 'using All ships call types'
primary battery: non-rechargeable primary power source
symbol (as part of the DSC sentence): 7 binary bits of a 10 bit DSC word that have the information content
test mode: self-testing mode using an individual test call to own vessel
ETSI
8 ETSI EN 300 338-6 V1.3.1 (2024-03)
word (as part of the DSC sentence): 10 binary bits that make up the coded entities of a transmitted DSC message
NOTE: The 10 bits consist of a 7 bit "symbol" that gives the information content and 3 bit error check that gives
the number of 0 binary bits in the 7 bit symbol.
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AIS Automatic Identification System
CIRM Comité International Radio-Maritime
COG Course Over Ground
DSC Digital Selective Calling
ECC Error Check Character
EDS Expansion Data Specifier
EOS End Of Sequence
FM Frequency Modulation
GMDSS Global Maritime Distress and Safety System
GMSK Gaussian Minimum Shift Keying
GNSS Global Navigation Satellite System
GPS Global Positioning System
HF High Frequency
ID IDentity
ITU International Telecommunications Union
ITU-R ITU - Radiocommunications sector
LBT Listen Before Talk
MF Medium Frequency
MMSI Maritime Mobile Service Identity
MOB Man Overboard
MSLD Maritime Survivor Locating Device
PM Phase Modulation
RX Receiver
SOG Speed Over Ground
SOTDMA Self-Organized Time Division Multiple Access
TX Transmitter
UTC Universal Time Co-ordinated
VHF Very High Frequency
4 General requirements
4.1 General
Class M MOB devices are employed in situations of grave and imminent danger to persons that require immediate
assistance from other vessels or search and rescue services.
MOB devices shall be:
• Fitted with an internal electronic GNSS position fixing device.
• Fitted with a transceiver operating on VHF DSC channel 70.
• Fitted with an Automatic Identification System (AIS) transmitter operating in accordance with annex A to
provide radio location.
ETSI
9 ETSI EN 300 338-6 V1.3.1 (2024-03)
• Fitted with audio and visual indicators to designate operation of the MOB device, intrinsically safe MOB
devices shall be fitted with a minimum of visual indicators.
• Capable of manual activation and deactivation and optionally automatic activation (see clause 4.4).
4.2 Frequency of operation
The MOB device shall operate on 156,525 MHz (Channel 70), 161,975 MHz (AIS 1) & 162,025 MHz (AIS 2) only.
4.3 Class of emission
DSC: G2B Phase Modulation (PM) with digital information modulated on a sub-carrier.
AIS: F1D GMSK 9 600 baud.
4.4 Controls
The MOB device shall be initially activated by the use of two simple, but independent mechanical actions, neither of
which on its own shall activate the equipment. If the second mechanical action is replaced by an immersion sensor, then
the first mechanical action should be an arming or enabling function thus to ensure the MSLD is armed for automatic
activation when submerged.
It should only be possible to activate the equipment after a seal or other mechanical restraint has been removed from the
first mechanical action. After activation it shall be possible to de-activate the equipment and the means to deactivate the
equipment shall be clearly marked. It should be possible to determine that the equipment has been previously activated.
4.5 Indicators
4.5.0 General
The MOB device shall be provided with a visual and, with the exception of intrinsically safe MOB devices, audible
indications that designate the operation of the MOB device as specified in clauses 4.5.1 and 4.5.2.
4.5.1 Audible indicators
The audible indicator shall signal:
• When the MOB device is first activated.
• Prior to any DSC transmission.
4.5.2 Visual Indicators
The visual indicator shall clearly distinguish the following states:
• The MOB device has been activated and is transmitting in active mode.
• The MOB device has a GNSS position fix and is transmitting in active mode.
• The MOB device is undergoing test and is transmitting in test mode.
• The MOB device cannot complete a test because it could not obtain a GNSS position.
• The MOB device cannot complete a test because it has not been properly programmed with own vessel MMSI
(closed loop devices only).
• The MOB device has completed a test or has been deactivated locally.
ETSI
10 ETSI EN 30
...