ETSI EN 300 338-3 V1.2.1 (2017-02)

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 3: Class D DSC
2 ETSI EN 300 338-3 V1.2.1 (2017-02)

Reference
REN/ERM-TG26-087-3
Keywords
DSC, GMDSS, maritime, radio
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 - NAF 742 C
Association à but non lucratif enregistrée à la
Sous-Préfecture de Grasse (06) N° 7803/88

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3 ETSI EN 300 338-3 V1.2.1 (2017-02)
Contents
Intellectual Property Rights . 6
Foreword . 6
Modal verbs terminology . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 7
3 Definitions and abbreviations . 8
3.1 Definitions . 8
3.2 Abbreviations . 9
4 Controls and indicators in Class D DSC equipment . . 10
4.1 Visual indication . 10
4.1.0 General . 10
4.1.1 DSC alphanumeric display . 10
4.1.1.0 Primary display information. 10
4.1.1.1 Additional display information . 10
4.1.2 Display requirements for additional controllers . 10
4.1.3 Handling visual information . 11
5 Technical requirements . 11
5.1 Facilities for DSC transmission and reception . 11
5.1.1 Watch receiver capabilities . 11
5.2 Facilities for coding and decoding of DSC . 11
5.2.1 Call functions . 11
5.2.2 INDIVIDUAL calls . 11
5.2.3 ALL SHIPS calls . 11
5.2.4 DSC call functionality . 12
6 Automated and non-automated procedure requirements in Class D DSC equipment . 12
6.1 Introduction . 12
6.2 Non-automated features . 13
6.2.0 Introduction. 13
6.2.1 DSC Message Composition . 13
6.2.2 Transmission of DSC messages and prioritized wait . 14
6.2.3 Alarms . 14
6.3 Standby . 14
6.4 Sending distress automated procedure . 16
6.4.1 Procedure . 16
6.4.2 Tasks . 17
6.4.3 Display . 17
6.4.3.0 General . 17
6.4.3.1 Examples of sending distress procedure displays on VHF equipment . 18
6.4.4 Dedicated distress button sub procedure . 18
6.4.5 Transmission of the alert attempt . 19
6.4.6 Updating position . 19
6.4.7 Handling received DSC Messages . 19
6.4.8 Alarms . 20
6.4.9 Determining Subsequent communications . 20
6.4.10 Automated tuning . 20
6.4.11 Cancelling the Distress Alert . 20
6.4.11.0 General . 20
6.4.11.1 Examples of cancel-distress displays on VHF equipment. 20
6.4.12 Acknowledgments . 21
6.4.13 Termination. 21
6.4.14 Warnings . 21
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4 ETSI EN 300 338-3 V1.2.1 (2017-02)
6.5 Receiving distress automated procedure . 22
6.5.1 Procedure . 22
6.5.2 Tasks . 23
6.5.3 Display . 23
6.5.3.0 General . 23
6.5.3.1 Examples of received distress procedure displays on VHF equipment . 24
6.5.4 Handling received DSC Messages . 24
6.5.5 Alarms . 25
6.5.6 Determining Subsequent communications . 25
6.5.7 Automated tuning . 25
6.5.8 Acknowledgments . 25
6.5.9 Termination. 25
6.5.10 Warnings . 25
6.6 Sending non distress automated procedure . 25
6.6.1 Procedure . 25
6.6.2 Tasks . 26
6.6.3 Display . 27
6.6.3.0 General . 27
6.6.3.1 Examples of sending non distress procedures displays on VHF equipment . 28
6.6.4 Handling received DSC Messages . 28
6.6.5 Alarms . 28
6.6.6 Automated tuning . 28
6.6.7 Delayed Acknowledgements . 29
6.6.8 Termination. 29
6.6.9 Warnings . 29
6.7 Receiving non distress automated procedure . 29
6.7.1 Procedure . 29
6.7.2 Tasks . 30
6.7.3 Display . 31
6.7.3.0 General . 31
6.7.3.1 Examples of receiving non distress procedures displays on VHF equipment . 32
6.7.4 Handling received DSC messages . 32
6.7.5 Alarms . 32
6.7.6 Automated tuning . 32
6.7.7 Acknowledgments . 33
6.7.8 Termination. 33
6.7.9 Warnings . 33
6.8 Communications automated procedure . 34
6.8.1 Procedure . 34
6.8.2 Tasks . 34
6.8.3 Display . 34
6.8.4 Handling received DSC Messages . 34
6.8.5 Tuning of the general receiver and transmitter . 34
6.8.6 Termination. 34
6.9 Handling incoming calls while the equipment is engaged . 35
6.9.1 Procedure . 35
6.9.2 Tasks . 35
6.9.2.0 Introduction . 35
6.9.2.1 Higher priority calls . 35
6.9.2.1.0 Priority . 35
6.9.2.1.1 Higher priority calls - acceptance . 35
6.9.2.1.2 Higher priority calls - non acceptance . 36
6.9.2.2 Other calls . 36
6.9.2.3 Termination of automated procedures . 36
6.9.2.4 Action after termination of an automated procedure . 36
6.9.2.5 Putting automated procedures on hold (optional) . 36
6.9.2.6 Controlling non-terminated automated procedures (optional) . 36
Annex A (normative): DSC message composition . 38
A.1 Default values . 38
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5 ETSI EN 300 338-3 V1.2.1 (2017-02)
Annex B (normative): Automated non distress channel selection algorithm . 39
Annex C (normative): Alarms . 40
C.1 Alarm specifications . 40
C.2 Alarming with critical errors . 41
C.3 Default alarm sounds . 41
C.4 Recommended alarm sounds . 42
History . 43

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6 ETSI EN 300 338-3 V1.2.1 (2017-02)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is 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 IPR Policy, no investigation, 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.
Foreword
This European Standard (EN) has been produced by ETSI Technical Committee Electromagnetic compatibility and
Radio spectrum Matters (ERM).
The present document is part 3 of a multi-part deliverable. Full details of the entire series can be found in part 1 [i.2].
The present document covers the operator interfaces and operating system for Class D DSC equipment.

National transposition dates
Date of adoption of this EN: 8 February 2017
Date of latest announcement of this EN (doa): 31 May 2017
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 30 November 2017
Date of withdrawal of any conflicting National Standard (dow): 30 November 2018

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.
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7 ETSI EN 300 338-3 V1.2.1 (2017-02)
1 Scope
The present document states the minimum requirements for general communication for shipborne fixed installations using
DSC - class D.
Class D DSC is intended be used in the Very High Frequency (VHF) band of the Maritime Mobile Service (MMS), for
distress, urgency and safety communication and general communications using telephony for subsequent
communications.
The present document is part 3 of a multi-part deliverable that covers the requirements to be fulfilled by equipment that
is either integrated with a transmitter and/or a receiver or equipment that is a stand-alone DSC terminal.
These requirements include the relevant provisions and the guidelines of the IMO as detailed in MSC/Circ.803 [i.1] for
non-SOLAS vessels participating in the GMDSS as well as Commission Decision of 4 September 2003
(2004/71/EC [i.5]).
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
http://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] ITU Radio Regulations (2016).
[2] Recommendation ITU-R M.493-14 (2015): "Digital selective-calling system for use in the
maritime mobile service".
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] IMO Circular MSC/Circ-803: "Participation of non-SOLAS ships in the Global Maritime Distress
and Safety System (GMDSS)".
[i.2] 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".
[i.3] MSC 302(87): "Adoption of performance standards for bridge alert management".
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8 ETSI EN 300 338-3 V1.2.1 (2017-02)
[i.4] IEC 61924-2 Edition 1 (including Corrigendum 1 November 2013): "Maritime navigation and
radiocommunication equipment and systems - integrated navigation systems - Part 2: Modular
structure for INS - operational and performance requirements, methods of testing and required test
results".
[i.5] 2004/71/EC: "Commission Decision of 4 September 2003 on essential requirements relating to
marine radio communication equipment which is intended to be used on non-SOLAS vessels and
to participate in the Global Maritime Distress and Safety System (GMDSS)".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in ETSI EN 300 338-1 [i.2] and the following
apply:
acknowledged: automated procedure which indicates that the objective of the initial DSC message has been achieved
active: automated procedure which has control of the general receiver and transmitter and is thus able to engage in
subsequent communications and receive DSC messages on both the watch receiver and general receiver
automated procedure: set of actions necessary to complete the objective of an initiating DSC message or non DSC
communication event
NOTE 1: Four DSC automated procedures are designed to process these. They are the receiving of distress DSC
messages, the receiving of non distress DSC messages, the sending of distress DSC alert attempts and the
sending of non distress DSC messages. In addition a fifth procedure is designed to handle non DSC
communication events.
NOTE 2: These automated procedures are called:
received distress automated procedure;
sending distress automated procedure;
received non-distress automated procedure;
sending non-distress automated procedure;
communications automated procedure.
class D: class of DSC intended to provide minimum facilities for VHF DSC distress, urgency and safety as well as
routine calling and reception, not necessarily in full accordance with IMO GMDSS carriage requirements for VHF
installations
default: value selected or an action taken by the equipment software in the absence of any operator input
distress DSC message: DSC message or acknowledgement containing the distress information
distress event: unique distress situation identified by two parameters of the distress information; the MMSI of the
vessel in distress and the nature of distress
engaged: equipment that is busy handling an automated procedure
factory default: default value that is set by the manufacturer such that the field or behaviour is defined prior to any
operator intervention
general receiver: receiver part of the transceiver used for the reception of all subsequent communications
NOTE: It is important to distinguish this unit from the watch receiver.
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9 ETSI EN 300 338-3 V1.2.1 (2017-02)
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
NOTE: These symbols are repeated in the DX/RX time diversity pattern.
initial DSC message: DSC message that starts an automated procedure
non distress DSC message: DSC messages or acknowledgments that do not have the format specifier or category of
"distress"
objective: intent of the DSC message either to establish subsequent communications or request information
operator options: any choices the operator can make while the automated procedure is engaged
pertinent to the automated procedure: DSC messages that have something to do with the procedure and are therefore
'handled' by the procedure
NOTE: A DSC message is pertinent to an automated procedure if the set of information characters in the DSC
message has the correct values.
pertinent to the station: any DSC message that would start an automated procedure if the transceiver were in standby
self-terminating alarm: short alarm that stops by itself without operator intervention
NOTE: The purpose of this alarm is to inform the operator that a DSC message is received but it does not require
his immediate attention.
symbol (as part of the DSC sentence): 7 binary bits of a 10 bit DSC word that have the information content
top level: items, buttons, or functions are present and visible without requiring any action by the operator (such as
scrolling, opening up menus, or removing any obscuring covers, etc.)
two-tone alarm: alarm consisting of a repetition of the 2 200 Hz frequency for 250 ms followed by a 1 300 Hz
frequency for 250 ms
NOTE: This alarm is used for the initiation of the received distress DSC automated procedure.
urgency alarm: alarm consisting of a repetition of the 2 200 Hz frequency for 250 ms followed by 250 ms period of
silence
NOTE: This alarm is used for the initiation of the received non distress DSC automated procedure when the
category of the initiating DSC message is "urgency".
watch receiver: separate receiver in DSC radios that continuously monitors VHF channel 70
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 Abbreviations
For the purposes of the present document, the abbreviations given in ETSI EN 300 338-1 [i.2] apply.
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10 ETSI EN 300 338-3 V1.2.1 (2017-02)
4 Controls and indicators in Class D DSC equipment
4.1 Visual indication
4.1.0 General
Any visual display of the information content shall be clearly legible under all ambient light conditions.
4.1.1 DSC alphanumeric display
4.1.1.0 Primary display information
The display characters shall have a minimum height of 3,5 mm, and a nominal character width/height ratio of 0,7.
The display shall have a minimum of 12 characters per line and a minimum of 32 characters total.
Any displayed information shall be static. Horizontal scrolling techniques are not permitted (see clause 4.1.3).
The display shall be capable of:
• prompting the operator if an incorrect operation is attempted;
• displaying error messages;
• displaying incoming and logged calls in plain language;
• displaying all the user programmable information content of a DSC call.
4.1.1.1 Additional display information
Additional display characters or symbols shall be capable of:
• showing the functions and options currently available;
• displaying that unread received DSC calls are present in memory;
• displaying other visual alarms;
• displaying whether the position and time information is automatically entered or manually entered.
For integrated equipment there shall be additional display characters and symbols as required for displaying channel
designator and other radio parameters.
Where logic flows and procedural guidance, expressed by graphical symbols, have an advantage over text, this shall be
allowed. Any graphical symbols shall be clearly defined in the operation manual.
4.1.2 Display requirements for additional controllers
Where the additional controller is a fixed installation, it shall have exactly the same characteristics as the primary
controller, including the display.
Where the additional controller is a handheld device, it shall have exactly the same characteristics as the primary
controller, except for the display, which may be scaled down for a minimum character height of 2 mm.
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11 ETSI EN 300 338-3 V1.2.1 (2017-02)
4.1.3 Handling visual information
In case all information, or user options, required for the active automated procedure, cannot be contained on a single
screen, means shall be available to inform the user:
a) that more information is available;
b) how to select the relevant information not yet displayed, e.g. by means of a next button or info key.
5 Technical requirements
5.1 Facilities for DSC transmission and reception
5.1.1 Watch receiver capabilities
The watchkeeping receiver part of the DSC equipment shall be designed for continuous operation on channel 70 but the
receiver need not operate when the transmitter is in use.
5.2 Facilities for coding and decoding of DSC
5.2.1 Call functions
The facilities for coding and composition of calls shall be so arranged that it is possible for the operator quickly and
precisely to enter a call. The types of DSC calls provided in this equipment are specified in clause 5.2.4.
The CALL functions shall permit selection of the following functions:
• INDIVIDUAL: for making a call to a specific MMSI.
• GROUP: for making a call to a specific Group MMSI.
• ALL SHIPS: for making all ships calls.
• RECEIVED CALLS: for retrieving stored incoming DSC calls.
• OTHER: for equipment housekeeping functions.
5.2.2 INDIVIDUAL calls
The INDIVIDUAL call facility shall permit either the MANUAL entry of a MMSI or the selection of a station from the
DIRECTORY list. The DIRECTORY list shall have a facility for at least 10 entries. Their MMSIs shall be
programmable. If the called station is a coast station (i.e. MMSI commencing 00) no further information shall be
requested from the operator. If the called station is a ship station the equipment shall request input of a channel number.
The equipment shall assist the operator by suggesting a suitable inter-ship channel as defined in appendix 18 of the ITU
Radio Regulations [1].
5.2.3 ALL SHIPS calls
It shall be possible to transmit ALL SHIPS calls by means of deliberate actions, such as two levels of menu instructions.
The operator shall be able to select either Urgency or Safety category and the equipment shall propose the default
subsequent working channel of 16 (the operator shall have the option to change the working channel).
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12 ETSI EN 300 338-3 V1.2.1 (2017-02)
5.2.4 DSC call functionality
The following DSC calls shall be available in the equipment.
Table 1
CALL TYPE Tx Rx Format specifier Notes
Distress alert Y Y 112 TX: All natures of distress except "EPIRB"
Distress acknowledgement # Y 116
Distress relay RT Individual # Y 120 This includes DROBOSE
Distress relay RT Geographic area # O 102
Distress relay RT All ships # Y 116
Distress relay MoB Group # Y 114
Distress relay EPIRB Individual # Y 120
Distress relay EPIRB Geographic area # O 102
Distress relay EPIRB All ships # Y 116
Distress relay ACK Individual # Y 120
Distress relay ACK DROBOSE to Group Y Y 114 Nature of Distress 110
Distress relay ACK DROBOSE to MoB Y N 120 Nature of Distress 110
Distress relay ACK RT All ships # Y 116
Distress relay ACK EPIRB # Y 120
Distress relay ACK EPIRB All ships # Y 116
All ships RT call Y Y 116 Urgency (110) and Safety (108) only
All ships Duplex RT call # O 116 These are FULL duplex calls. Urgency
(110) and Safety (108) only
Individual RT call N Y 120 Urgency (110) and Safety (108) only
Individual RT call acknowledgement Y N 120 Urgency (110) and Safety (108) only
Individual RT call acknowledgement Y N 120 Urgency (110) and Safety (108) only
"unable to comply"
Individual test call Y Y 120 Safety (108) only
Individual test call acknowledgement Y Y 120 Safety (108) only
Routine group call RT Y Y 114
Routine individual RT call Y Y 120
Routine individual RT ACK Y Y 120
Position request N Y 120 Safety (108) only
Position request ACK Y N 120 Safety (108) only
Distress Alert Cancel Y Y 112 This is the "self addressed" distress ACK

If any other calls, not listed in table 1, are implemented in the device, they shall comply with tables A1-4.1 to A1-4.9 of
Recommendation ITU-R M.493-14 [2]. Individual routine category polling and position calls from previous versions of
this Recommendation may be implemented for the sake of reverse compatibility.
Call types marked # shall not be available in the equipment.
Call types marked Y shall be available in the equipment.
Call types marked N are not required to be available in the equipment.
Call types marked O are for reverse compatibility with older equipment.
6 Automated and non-automated procedure
requirements in Class D DSC equipment
6.1 Introduction
This clause covers the minimum level of software automation, operational simplicity, and interface consistency
requirements for shipborne fixed installations using class D Digital Selective Calling equipment.
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13 ETSI EN 300 338-3 V1.2.1 (2017-02)
Perhaps the most important issue concerns an implied expectation for the use of the terminology "automated procedure"
as used in the present document to appear in the user interface. The terminology "automated procedure" describes the
set of algorithms that are used to encapsulate all the activities necessary to perform DSC, and non DSC communication
events. The operator does not need to know anything about the existence of automated procedures in order to operate a
radio that makes use of these algorithms. Though the present document refers to items such as the "Sending Distress
Automated Procedure" such language shall not appear on the user interface of the equipment.
The primary purpose of DSC signalling is to provide the means to set-up subsequent communications between vessels
and/or coast stations. A call may be considered as being the total duration from the start of the DSC signalling until the
end of the subsequent communications, and the automated procedure is terminated.
The operational functionality described in the present document has the objective of not disturbing any ongoing call.
Furthermore, the equipment shall assist the operator by providing simple audible indication of a received DSC call
whilst the equipment is engaged and if that received DSC call is of a higher priority than the call in progress then the
equipment shall be capable of displaying the information of this new call.
6.2 Non-automated features
6.2.0 Introduction
This clause describes the features of the equipment that are necessary to assure compliance to the ITU-R DSC
functionality standards and support a smoother operation of the automation algorithms, but are not directly related to the
automation algorithms.
6.2.1 DSC Message Composition
The equipment shall provide factory default values for all non distress DSC messages as specified in Recommendation
ITU-R M.493-14 [2], annex 3 and summarized in figure A.1 for all parameters where the operator has the option to
select or enter more than one value and has not already done so.
The default values for the operator-composed distress alert shall be the default distress alert as specified in the sent
distress automated procedure.
A destination MMSI that does not have at least 9 digits entered is invalid.
No DSC message shall be able to be sent that has an invalid parameter.
For simplicity of the user interface:
a) the DSC message composition interface shall be such that the operator needs no user manual to initiate the
desired DSC message;
b) parameter descriptions and terms shall be provided in plain language;
c) all parameters of the DSC message that do not require an operator choice shall be entered automatically;
d) guidance and/or prompting shall be provided for the entry of any necessary parameters of the DSC message if
these parameters and/or their values are not plainly visible from context or on the display.
For data entry:
a) the equipment shall only allow the operator to compose and send DSC messages that are compliant with
clause 5.2.4;
b) acknowledgements shall be automatically composed by the equipment and user options for these
acknowledgements are provided by the automated procedures;
c) the equipment shall provide an automatic determination of the channel and or frequencies of subsequent
communication according to the algorithm given in Recommendation ITU-R M.493-14 [2], annex 3 and
summarized in annex B.
The automated channel selection shall be able to be overridden.
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14 ETSI EN 300 338-3 V1.2.1 (2017-02)
It shall not be possible to select a distress channel for subsequent communications for DSC messages of priority routine.
The equipment shall automatically set the dot pattern length to 20 bits for all transmitted DSC messages.
6.2.2 Transmission of DSC messages and prioritized wait
If the channel is free the transmission shall begin immediately. If the channel is not free, and the DSC message is a
distress alert, the alert shall be transmitted as soon as the channel becomes free or after 1s, whichever occurs first.
(The 1 s value is approximate average duration of a VHF DSC message). For all other DSC messages, the equipment
shall wait for the channel to become free and then the equipment shall delay transmission of the DSC message for a
specified wait time.
The specified wait time shall depend upon the message type and priority. Distress DSC messages (except for alerts),
urgency, safety, routine and test DSC messages shall wait one, two, three, and four "fixed" units of time plus a random
addition described below, respectively, before attempting to transmit. Transmission occurs if and only if the channel is
still free after this wait time has elapsed, otherwise the process is repeated.
The fixed "unit" of time shall be 50 milliseconds. The randomly generated component shall be some positive integer
with resolution in milliseconds between zero and the fixed interval. The randomly generated part of the wait time shall
be recomputed for every transmission attempt.
6.2.3 Alarms
Alarms shall have both a visual and aural component.
Any alarm that initiates for the purpose of getting the operator's attention shall provide the reason for and means to
terminate the alarm.
Alarms shall be initiated for the reasons given in table C.1.
The means to terminate the alarms are given in table C.1.
The "two-tone" and "urgency-sound" alarms shall not be able to be disabled.
Those aural alarms are
...

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.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 3: Class D DSC47.020.70Navigacijska in krmilna opremaNavigation and control equipment33.060.20Sprejemna in oddajna opremaReceiving and transmitting equipmentICS:Ta slovenski standard je istoveten z:ETSI EN 300 338-3 V1.2.1 (2017-02)SIST EN 300 338-3 V1.2.1:2017en01-april-2017SIST EN 300 338-3 V1.2.1:2017SLOVENSKI
STANDARD
EUROPEAN STANDARD SIST EN 300 338-3 V1.2.1:2017

ETSI ETSI EN 300 338-3 V1.2.1 (2017-02) 2
Reference REN/ERM-TG26-087-3 Keywords DSC, GMDSS, maritime, radio ETSI 650 Route des Lucioles F-06921 Sophia Antipolis Cedex - FRANCE
Tel.: +33 4 92 94 42 00
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Important notice The present document can be downloaded from: http://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 only prevailing document is the print of the Portable Document Format (PDF) version kept on a specific network drive within ETSI Secretariat. 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 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.
© European Telecommunications Standards Institute 2017. All rights reserved.
DECTTM, PLUGTESTSTM, UMTSTM and the ETSI logo are Trade Marks of ETSI registered for the benefit of its Members. 3GPPTM and LTE™ are Trade Marks of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners. GSM® and the GSM logo are Trade Marks registered and owned by the GSM Association. SIST EN 300 338-3 V1.2.1:2017

ETSI ETSI EN 300 338-3 V1.2.1 (2017-02) 3 Contents Intellectual Property Rights . 6 Foreword . 6 Modal verbs terminology . 6 1 Scope . 7 2 References . 7 2.1 Normative references . 7 2.2 Informative references . 7 3 Definitions and abbreviations . 8 3.1 Definitions . 8 3.2 Abbreviations . 9 4 Controls and indicators in Class D DSC equipment . 10 4.1 Visual indication . 10 4.1.0 General . 10 4.1.1 DSC alphanumeric display . 10 4.1.1.0 Primary display information. 10 4.1.1.1 Additional display information . 10 4.1.2 Display requirements for additional controllers . 10 4.1.3 Handling visual information . 11 5 Technical requirements . 11 5.1 Facilities for DSC transmission and reception . 11 5.1.1 Watch receiver capabilities . 11 5.2 Facilities for coding and decoding of DSC . 11 5.2.1 Call functions . 11 5.2.2 INDIVIDUAL calls . 11 5.2.3 ALL SHIPS calls . 11 5.2.4 DSC call functionality . 12 6 Automated and non-automated procedure requirements in Class D DSC equipment . 12 6.1 Introduction . 12 6.2 Non-automated features . 13 6.2.0 Introduction. 13 6.2.1 DSC Message Composition . 13 6.2.2 Transmission of DSC messages and prioritized wait . 14 6.2.3 Alarms . 14 6.3 Standby . 14 6.4 Sending distress automated procedure . 16 6.4.1 Procedure . 16 6.4.2 Tasks . 17 6.4.3 Display . 17 6.4.3.0 General . 17 6.4.3.1 Examples of sending distress procedure displays on VHF equipment . 18 6.4.4 Dedicated distress button sub procedure . 18 6.4.5 Transmission of the alert attempt . 19 6.4.6 Updating position . 19 6.4.7 Handling received DSC Messages . 19 6.4.8 Alarms . 20 6.4.9 Determining Subsequent communications . 20 6.4.10 Automated tuning . 20 6.4.11 Cancelling the Distress Alert . 20 6.4.11.0 General . 20 6.4.11.1 Examples of cancel-distress displays on VHF equipment. 20 6.4.12 Acknowledgments . 21 6.4.13 Termination. 21 6.4.14 Warnings . 21 SIST EN 300 338-3 V1.2.1:2017

ETSI ETSI EN 300 338-3 V1.2.1 (2017-02) 4 6.5 Receiving distress automated procedure . 22 6.5.1 Procedure . 22 6.5.2 Tasks . 23 6.5.3 Display . 23 6.5.3.0 General . 23 6.5.3.1 Examples of received distress procedure displays on VHF equipment . 24 6.5.4 Handling received DSC Messages . 24 6.5.5 Alarms . 25 6.5.6 Determining Subsequent communications . 25 6.5.7 Automated tuning . 25 6.5.8 Acknowledgments . 25 6.5.9 Termination. 25 6.5.10 Warnings . 25 6.6 Sending non distress automated procedure . 25 6.6.1 Procedure . 25 6.6.2 Tasks . 26 6.6.3 Display . 27 6.6.3.0 General . 27 6.6.3.1 Examples of sending non distress procedures displays on VHF equipment . 28 6.6.4 Handling received DSC Messages . 28 6.6.5 Alarms . 28 6.6.6 Automated tuning . 28 6.6.7 Delayed Acknowledgements . 29 6.6.8 Termination. 29 6.6.9 Warnings . 29 6.7 Receiving non distress automated procedure . 29 6.7.1 Procedure . 29 6.7.2 Tasks . 30 6.7.3 Display . 31 6.7.3.0 General . 31 6.7.3.1 Examples of receiving non distress procedures displays on VHF equipment . 32 6.7.4 Handling received DSC messages . 32 6.7.5 Alarms . 32 6.7.6 Automated tuning . 32 6.7.7 Acknowledgments . 33 6.7.8 Termination. 33 6.7.9 Warnings . 33 6.8 Communications automated procedure . 34 6.8.1 Procedure . 34 6.8.2 Tasks . 34 6.8.3 Display . 34 6.8.4 Handling received DSC Messages . 34 6.8.5 Tuning of the general receiver and transmitter . 34 6.8.6 Termination. 34 6.9 Handling incoming calls while the equipment is engaged . 35 6.9.1 Procedure . 35 6.9.2 Tasks . 35 6.9.2.0 Introduction . 35 6.9.2.1 Higher priority calls . 35 6.9.2.1.0 Priority . 35 6.9.2.1.1 Higher priority calls - acceptance . 35 6.9.2.1.2 Higher priority calls - non acceptance . 36 6.9.2.2 Other calls . 36 6.9.2.3 Termination of automated procedures . 36 6.9.2.4 Action after termination of an automated procedure . 36 6.9.2.5 Putting automated procedures on hold (optional) . 36 6.9.2.6 Controlling non-terminated automated procedures (optional) . 36 Annex A (normative): DSC message composition . 38 A.1 Default values . 38 SIST EN 300 338-3 V1.2.1:2017

ETSI ETSI EN 300 338-3 V1.2.1 (2017-02) 5 Annex B (normative): Automated non distress channel selection algorithm . 39 Annex C (normative): Alarms . 40 C.1 Alarm specifications . 40 C.2 Alarming with critical errors . 41 C.3 Default alarm sounds . 41 C.4 Recommended alarm sounds . 42 History . 43
ETSI ETSI EN 300 338-3 V1.2.1 (2017-02) 6 Intellectual Property Rights IPRs essential or potentially essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is 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 IPR Policy, no investigation, 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. Foreword This European Standard (EN) has been produced by ETSI Technical Committee Electromagnetic compatibility and Radio spectrum Matters (ERM). The present document is part 3 of a multi-part deliverable. Full details of the entire series can be found in part 1 [i.2]. The present document covers the operator interfaces and operating system for Class D DSC equipment.
National transposition dates Date of adoption of this EN: 8 February 2017 Date of latest announcement of this EN (doa): 31 May 2017 Date of latest publication of new National Standard or endorsement of this EN (dop/e):
30 November 2017 Date of withdrawal of any conflicting National Standard (dow): 30 November 2018
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. SIST EN 300 338-3 V1.2.1:2017

ETSI ETSI EN 300 338-3 V1.2.1 (2017-02) 7 1 Scope The present document states the minimum requirements for general communication for shipborne fixed installations using DSC - class D. Class D DSC is intended be used in the Very High Frequency (VHF) band of the Maritime Mobile Service (MMS), for distress, urgency and safety communication and general communications using telephony for subsequent communications. The present document is part 3 of a multi-part deliverable that covers the requirements to be fulfilled by equipment that is either integrated with a transmitter and/or a receiver or equipment that is a stand-alone DSC terminal. These requirements include the relevant provisions and the guidelines of the IMO as detailed in MSC/Circ.803 [i.1] for non-SOLAS vessels participating in the GMDSS as well as Commission Decision of 4 September 2003 (2004/71/EC [i.5]). 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 http://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] ITU Radio Regulations (2016). [2] Recommendation ITU-R M.493-14 (2015): "Digital selective-calling system for use in the maritime mobile service". 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] IMO Circular MSC/Circ-803: "Participation of non-SOLAS ships in the Global Maritime Distress and Safety System (GMDSS)". [i.2] 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". [i.3] MSC 302(87): "Adoption of performance standards for bridge alert management". SIST EN 300 338-3 V1.2.1:2017

ETSI ETSI EN 300 338-3 V1.2.1 (2017-02) 8 [i.4] IEC 61924-2 Edition 1 (including Corrigendum 1 November 2013): "Maritime navigation and radiocommunication equipment and systems - integrated navigation systems - Part 2: Modular structure for INS - operational and performance requirements, methods of testing and required test results". [i.5] 2004/71/EC: "Commission Decision of 4 September 2003 on essential requirements relating to marine radio communication equipment which is intended to be used on non-SOLAS vessels and to participate in the Global Maritime Distress and Safety System (GMDSS)". 3 Definitions and abbreviations 3.1 Definitions For the purposes of the present document, the terms and definitions given in ETSI EN 300 338-1 [i.2] and the following apply: acknowledged: automated procedure which indicates that the objective of the initial DSC message has been achieved active: automated procedure which has control of the general receiver and transmitter and is thus able to engage in subsequent communications and receive DSC messages on both the watch receiver and general receiver automated procedure: set of actions necessary to complete the objective of an initiating DSC message or non DSC communication event NOTE 1: Four DSC automated procedures are designed to process these. They are the receiving of distress DSC messages, the receiving of non distress DSC messages, the sending of distress DSC alert attempts and the sending of non distress DSC messages. In addition a fifth procedure is designed to handle non DSC communication events. NOTE 2: These automated procedures are called:
received distress automated procedure;
sending distress automated procedure;
received non-distress automated procedure;
sending non-distress automated procedure;
communications automated procedure. class D: class of DSC intended to provide minimum facilities for VHF DSC distress, urgency and safety as well as routine calling and reception, not necessarily in full accordance with IMO GMDSS carriage requirements for VHF installations default: value selected or an action taken by the equipment software in the absence of any operator input distress DSC message: DSC message or acknowledgement containing the distress information distress event: unique distress situation identified by two parameters of the distress information; the MMSI of the vessel in distress and the nature of distress engaged: equipment that is busy handling an automated procedure factory default: default value that is set by the manufacturer such that the field or behaviour is defined prior to any operator intervention general receiver: receiver part of the transceiver used for the reception of all subsequent communications NOTE: It is important to distinguish this unit from the watch receiver. SIST EN 300 338-3 V1.2.1:2017

ETSI ETSI EN 300 338-3 V1.2.1 (2017-02) 9 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 NOTE: These symbols are repeated in the DX/RX time diversity pattern. initial DSC message: DSC message that starts an automated procedure non distress DSC message: DSC messages or acknowledgments that do not have the format specifier or category of "distress" objective: intent of the DSC message either to establish subsequent communications or request information operator options: any choices the operator can make while the automated procedure is engaged pertinent to the automated procedure: DSC messages that have something to do with the procedure and are therefore 'handled' by the procedure NOTE: A DSC message is pertinent to an automated procedure if the set of information characters in the DSC message has the correct values. pertinent to the station: any DSC message that would start an automated procedure if the transceiver were in standby self-terminating alarm: short alarm that stops by itself without operator intervention NOTE: The purpose of this alarm is to inform the operator that a DSC message is received but it does not require his immediate attention. symbol (as part of the DSC sentence): 7 binary bits of a 10 bit DSC word that have the information content top level: items, buttons, or functions are present and visible without requiring any action by the operator (such as scrolling, opening up menus, or removing any obscuring covers, etc.) two-tone alarm: alarm consisting of a repetition of the 2 200 Hz frequency for 250 ms followed by a 1 300 Hz frequency for 250 ms NOTE: This alarm is used for the initiation of the received distress DSC automated procedure. urgency alarm: alarm consisting of a repetition of the 2 200 Hz frequency for 250 ms followed by 250 ms period of silence NOTE: This alarm is used for the initiation of the received non distress DSC automated procedure when the category of the initiating DSC message is "urgency". watch receiver: separate receiver in DSC radios that continuously monitors VHF channel 70 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 Abbreviations For the purposes of the present document, the abbreviations given in ETSI EN 300 338-1 [i.2] apply. SIST EN 300 338-3 V1.2.1:2017

ETSI ETSI EN 300 338-3 V1.2.1 (2017-02) 10 4 Controls and indicators in Class D DSC equipment 4.1 Visual indication 4.1.0 General Any visual display of the information content shall be clearly legible under all ambient light conditions. 4.1.1 DSC alphanumeric display 4.1.1.0 Primary display information The display characters shall have a minimum height of 3,5 mm, and a nominal character width/height ratio of 0,7. The display shall have a minimum of 12 characters per line and a minimum of 32 characters total. Any displayed information shall be static. Horizontal scrolling techniques are not permitted (see clause 4.1.3). The display shall be capable of: • prompting the operator if an incorrect operation is attempted; • displaying error messages; • displaying incoming and logged calls in plain language; • displaying all the user programmable information content of a DSC call. 4.1.1.1 Additional display information Additional display characters or symbols shall be capable of: • showing the functions and options currently available; • displaying that unread received DSC calls are present in memory; • displaying other visual alarms; • displaying whether the position and time information is automatically entered or manually entered. For integrated equipment there shall be additional display characters and symbols as required for displaying channel designator and other radio parameters. Where logic flows and procedural guidance, expressed by graphical symbols, have an advantage over text, this shall be allowed. Any graphical symbols shall be clearly defined in the operation manual. 4.1.2 Display requirements for additional controllers Where the additional controller is a fixed installation, it shall have exactly the same characteristics as the primary controller, including the display. Where the additional controller is a handheld device, it shall have exactly the same characteristics as the primary controller, except for the display, which may be scaled down for a minimum character height of 2 mm. SIST EN 300 338-3 V1.2.1:2017

ETSI ETSI EN 300 338-3 V1.2.1 (2017-02) 11 4.1.3 Handling visual information In case all information, or user options, required for the active automated procedure, cannot be contained on a single screen, means shall be available to inform the user: a) that more information is available; b) how to select the relevant information not yet displayed, e.g. by means of a next button or info key. 5 Technical requirements 5.1 Facilities for DSC transmission and reception 5.1.1 Watch receiver capabilities The watchkeeping receiver part of the DSC equipment shall be designed for continuous operation on channel 70 but the receiver need not operate when the transmitter is in use. 5.2 Facilities for coding and decoding of DSC 5.2.1 Call functions The facilities for coding and composition of calls shall be so arranged that it is possible for the operator quickly and precisely to enter a call. The types of DSC calls provided in this equipment are specified in clause 5.2.4. The CALL functions shall permit selection of the following functions: • INDIVIDUAL: for making a call to a specific MMSI. • GROUP: for making a call to a specific Group MMSI. • ALL SHIPS: for making all ships calls. • RECEIVED CALLS: for retrieving stored incoming DSC calls. • OTHER: for equipment housekeeping functions. 5.2.2 INDIVIDUAL calls The INDIVIDUAL call facility shall permit either the MANUAL entry of a MMSI or the selection of a station from the DIRECTORY list. The DIRECTORY list shall have a facility for at least 10 entries. Their MMSIs shall be programmable. If the called station is a coast station (i.e. MMSI commencing 00) no further information shall be requested from the operator. If the called station is a ship station the equipment shall request input of a channel number. The equipment shall assist the operator by suggesting a suitable inter-ship channel as defined in appendix 18 of the ITU Radio Regulations [1]. 5.2.3 ALL SHIPS calls It shall be possible to transmit ALL SHIPS calls by means of deliberate actions, such as two levels of menu instructions. The operator shall be able to select either Urgency or Safety category and the equipment shall propose the default subsequent working channel of 16 (the operator shall have the option to change the working channel). SIST EN 300 338-3 V1.2.1:2017

ETSI ETSI EN 300 338-3 V1.2.1 (2017-02) 12 5.2.4 DSC call functionality The following DSC calls shall be available in the equipment. Table 1 CALL TYPE Tx Rx Format specifier Notes Distress alert Y Y 112 TX: All natures of distress except "EPIRB" Distress acknowledgement # Y 116
Distress relay RT Individual # Y 120 This includes DROBOSE Distress relay RT Geographic area # O 102
Distress relay RT All ships # Y 116
Distress relay MoB Group # Y 114
Distress relay EPIRB Individual # Y 120
Distress relay EPIRB Geographic area # O 102
Distress relay EPIRB All ships # Y 116
Distress relay ACK Individual # Y 120
Distress relay ACK DROBOSE to Group Y Y 114 Nature of Distress 110 Distress relay ACK DROBOSE to MoB Y N 120 Nature of Distress 110 Distress relay ACK RT All ships # Y 116
Distress relay ACK EPIRB # Y 120
Distress relay ACK EPIRB All ships # Y 116
All ships RT call Y Y 116 Urgency (110) and Safety (108) only All ships Duplex RT call # O 116 These are FULL duplex calls. Urgency (110) and Safety (108) only Individual RT call N Y
120 Urgency (110) and Safety (108) only Individual RT call acknowledgement Y N 120 Urgency (110) and Safety (108) only Individual RT call acknowledgement "unable to comply" Y N 120 Urgency (110) and Safety (108) only Individual test call Y Y 120 Safety (108) only Individual test call acknowledgement Y Y 120 Safety (108) only Routine group call RT Y Y
Routine individual RT call Y Y 120
Routine individual RT ACK Y Y 120
Position request N Y 120 Safety (108) only Position request ACK Y N 120 Safety (108) only Distress Alert Cancel Y Y 112 This is the "self addressed" distress ACK
If any other calls, not listed in table 1, are implemented in the device, they shall comply with tables A1-4.1 to A1-4.9 of Recommendation ITU-R M.493-14 [2]. Individual routine category polling and position calls from previous versions of this Recommendation may be implemented for the sake of reverse compatibility. Call types marked # shall not be available in the equipment. Call types marked Y shall be available in the equipment. Call types marked N are not required to be available in the equipment. Call types marked O are for reverse compatibility with older equipment. 6 Automated and non-automated procedure requirements in Class D DSC equipment 6.1 Introduction This clause covers the minimum level of software automation, operational simplicity, and interface consistency requirements for shipborne fixed installations using class D Digital Selective Calling equipment. SIST EN 300 338-3 V1.2.1:2017

ETSI ETSI EN 300 338-3 V1.2.1 (2017-02) 13 Perhaps the most important issue concerns an implied expectation for the use of the terminology "automated procedure" as used in the present document to appear in the user interface. The terminology "automated procedure" describes the set of algorithms that are used to encapsulate all the activities necessary to perform DSC, and non DSC communication events. The operator does not need to know anything about the existence of automated procedures in order to operate a radio that makes use of these algorithms. Though the present document refers to items such as the "Sending Distress Automated Procedure" such language shall not appear on the user interface of the equipment. The primary purpose of DSC signalling is to provide the means to set-up subsequent communications between vessels and/or coast stations. A call may be considered as being the total duration from the start of the DSC signalling until the end of the subsequent communications, and the automated procedure is terminated. The operational functionality described in the present document has the objective of not disturbing any ongoing call. Furthermore, the equipment shall assist the operator by providing simple audible indication of a received DSC call whilst the equipment is engaged and if that received DSC call is of a higher priority than the call in progress then the equipment shall be capable of displaying the information of this new call. 6.2 Non-automated features 6.2.0 Introduction This clause describes the features of the equipment that are necessary to assure compliance to the ITU-R DSC functionality standards and support a smoother operation of the automation algorithms, but are not directly related to the automation algorithms. 6.2.1 DSC Message Composition The equipment shall provide factory default values for all non distress DSC messages as specified in Recommendation ITU-R M.493-14 [2], annex 3 and summarized in figure A.1 for all parameters where the operator has the option to select or enter more than one value and has not already done so. The default values for the operator-composed distress alert shall be the default distress alert as specified in the sent distress automated procedure. A destination MMSI that does not have at least 9 digits entered is invalid. No DSC message shall be able to be sent that has an invalid parameter. For simplicity of the user interface: a) the DSC message composition interface shall be such that the operator needs no user manual to initiate the desired DSC message; b) parameter descriptions and terms shall be provided in plain language; c) all parameters of the DSC message that do not require an operator choice shall be entered automatically; d) guidance and/or prompting shall be provided for the entry of any necessary parameters of the DSC message if these parameters and/or their values are not plainly visible from context or on the display. For data entry: a) the equipment shall only allow the operator to compose and send DSC messages that are compliant with clause 5.2.4; b) acknowledgements shall be automatically composed by the equipment and user options for these acknowledgements are provided by the automated procedures; c) the equipment shall provide an automatic determination of the channel and or frequencies of subsequent communication according to the algorithm given in Recommendation ITU-R M.493-14 [2], annex 3 and summarized in annex B. The automated channel selection shall be able to be overridden. SIST EN 300 338-3 V1.2.1:2017

ETSI ETSI EN 300 338-3 V1.2.1 (2017-02) 14 It shall not be possible to select a distress channel for subsequent communications for DSC messages of priority routine. The equipment shall automatically set the dot pattern length to 20 bits for all transmitted DSC messages. 6.2.2 Transmission of DSC messages and prioritized wait If the channel is free the transmission shall begin immediately. If the channel is not free, and the DSC message is a distress alert, the alert shall be transmitted as soon as the channel becomes free or after 1s, whichever occurs first. (The 1 s value is approximate average duration of a VHF DSC message). For all other DSC messages, the equipment shall wait for the channel to become free and then the equipment shall delay transmission of the DSC message for a specified wait time. The specified wait time shall depend upon the message type and priority. Distress DSC messages (except for alerts), urgency, safety, routine and test DSC messages shall wait one, two, three, and four "fixed" units of time plus a random addition described below, respectively, before attempting to transmit. Transmission occurs if and only if the channel is still free after this wait time has elapsed, otherwise the process is repeated. The fixed "unit" of time shall be 50 milliseconds. The randomly generated component shall be some positive integer with resolution in milliseconds between zero and the fixed interval. The randomly generated part of the wait time shall be recomputed for every transmission attempt. 6.2.3 Alarms Alarms shall have both a visual and aural component. Any alarm that initiates for the purpose of getting the operator's attention shall provide the reason for and means to terminate the alarm. Alarms shall be initiated for the reasons given in table C.1. The means to terminate the alarms are given in table C.1. The "two-tone" and "urgency-sound" alarms shall not be able to be disabled. Those aural alarms are given by table C.2. Alarms for other calls are specified in clause C.4. 6.3 Standby NOTE: Standby is the state of the equipment when it is not engaged in a communications or DSC automated procedure. The
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