MSC.1/Circ.

MSC.1-Circ.1403 - REVISED NAVTEX MANUAL (Secretariat)

MSC.1/Circ.1403 23 May 2011

MSC CIRCULAR
REVISED NAVTEX MANUAL
1 The Maritime Safety Committee (MSC), at its eighty-ninth session (11 to 20 May 2011), noted and approved the revised NAVTEX Manual, prepared by IHO, WMO and IMSO and agreed by the Sub-Committee on Radiocommunications and Search and Rescue (COMSAR), at its fifteenth session (7 to 11 March 2011), as set out in the attachment.
2 This circular supersedes documents COMSAR/Circ.7, COMSAR/Circ.28 and COMSAR/Circ.34, and replaces the existing text of the NAVTEX Manual.
3 The Committee decided that the revised text of the NAVTEX Manual will come into force on 1 January 2013.
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PREFACE
SOLAS regulation IV/12.2 states that "Every ship, while at sea, shall maintain a radio watch for broadcasts of maritime safety information on the appropriate frequency or frequencies on which such information is broadcast for the area in which the ship is navigating".
At the request of the IMO Sub-Committee on Radiocommunications, the NAVTEX Manual was first produced in 1988. Three subsequent editions have been produced, with the fourth edition published in 2005 containing amendments endorsed by the Maritime Safety Committee at its seventy-eighth session in May 2004 by MSC/Circ.1122.
At its seventh meeting in September 2005, the IHO Commission on the Promulgation of Radio Navigational Warnings (CPRNW1) established a Working Group to review all World-Wide Navigational Warning Service (WWNWS) documentation. The Working Group included representation from the WMO and firstly prepared revisions to IMO resolutions A.705(17), "Promulgation of Maritime Safety Information" and A.706(17), "World-Wide Navigational Warning Service". The proposed revisions of these resolutions were circulated to IHO Member States under IHB CL 104/2007, endorsed by COMSAR at its twelfth session in April 2008 and subsequently approved by the Maritime Safety Committee at its eighty-fifth session in November/December 2008 by MSC.1/Circ.1287 and MSC.1/Circ.1288 respectively.
The Working Group then prepared the revised Joint IMO/IHO/WMO Manual on Maritime Safety Information incorporating the revised information from resolutions A.705(17), as amended, and A.706(17), as amended. The revised text was circulated to IHO Member States under cover of IHB CL 70/2008, endorsed by COMSAR at its thirteenth session in January 2009 and subsequently approved by the Maritime Safety Committee at its eighty-sixth session in May/June 2009.
The Working Group subsequently prepared the third revision of the International SafetyNET Manual. The revised text of the International SafetyNET Manual was circulated to IHO Member States under cover of IHB CL 68/2009, endorsed by COMSAR at its fourteenth session in March 2010 and approved by the Maritime Safety Committee at its eighty-seventh session in May 2010 by MSC.1/Circ.1364.
Continuing with the holistic approach of reviewing all maritime safety information documents from the top-down, the Working Group prepared the fifth revision of the NAVTEX Manual. The revised text of the NAVTEX Manual was circulated to IHO Member States under cover of IHB CL 74/2010, endorsed by COMSAR at its fifteenth session in March 2011 and subsequently approved by the Maritime Safety Committee at its eighty-ninth session in May 2011.
1 CPRNW was renamed the IHO WWNWS Sub Committee (WWNWS) with effect from 1 January 2009.
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CONTENTS
SECTION PAGE
1 GENERAL INFORMATION .............................................................................
5
2 NAVTEX SERVICE .........................................................................................
2.1 Introduction ............................................................................................... 2.2 Definitions .................................................................................................
2.2.2 Delimitation of NAVAREAS ............................................................ 2.2.3 Delimitation of METAREAS ............................................................
5
5 7
10 11
3 GENERAL FEATURES OF NAVTEX SYSTEM ..............................................
11
4 PLANNING NAVTEX SERVICES ....................................................................
4.2 International NAVTEX services on 518 kHz ............................................. 4.3 National NAVTEX services on 490 kHz or 4209·5 kHz ............................ 4.4 National NAVTEX services on other frequencies .....................................
12
12 15 15
5 NAVTEX MESSAGE TECHNICAL CHARACTERS ........................................
5.1 Overview of technical characters, B1, B2, B3, B4 ....................................... 5.2 B1 – Transmitter Identification Character .................................................. 5.3 B2 – Subject Indicator Character ............................................................... 5.4 B3 B4 – Message Numbering Characters (NAVTEX Number) ..................
15
15 17 18 19
6 MESSAGE IDENTITY .....................................................................................
20
7 MESSAGE FORMAT .......................................................................................
7.7 Examples of Navigational Warning messages ......................................... 7.8 Examples of Meteorological messages .....................................................
20
22 23
8 LANGUAGE AND NATIONAL BROADCAST OPTIONS ................................
24
9 INFORMATION CONTROL .............................................................................
24
10 MESSAGE CONTENT ....................................................................................
10.2.1 Navigational warnings ......................................................................... 10.2.2 Meteorological warnings and forecasts ............................................... 10.2.3 Search and rescue information ........................................................... 10.2.4 Piracy attack warnings ........................................................................ 10.2.5 Tsunamis and other natural phenomena warning messages ............. 10.2.6 Pilot and VTS service messages ........................................................ 10.2.7 No messages on hand ........................................................................ 10.2.8 Use of abbreviations ........................................................................... 10.2.9 National NAVTEX Services .................................................................
24
24 25 25 25 26 26 26 26 26
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11 MESSAGE PRIORITIES AND BROADCAST PROCEDURES IN THE INTERNATIONAL NAVTEX SERVICE ...........................................................
11.1 Message priorities .................................................................................. 11.2 Broadcast procedures ............................................................................ 11.3 Meteorological NAVTEX Messages ....................................................... 11.4 National NAVTEX Services ....................................................................
26
26 27 27 28
12 RESPONSIBILITIES OF A NAVTEX CO-ORDINATOR ..................................
12.3 Management of the service .................................................................... 12.4 Balancing the volume of data to be broadcast throughout the daily transmission cycle ...................................................................................
28
29
29
13 BEST PRACTICE FOR THOSE USING THE SERVICE ................................
30
14 MUTUAL INTERFERENCE BETWEEN NAVTEX STATIONS ........................
30
15 NOTIFICATION OF NAVTEX SERVICES .......................................................
31
Annex 1 – IMO NAVTEX CO-ORDINATING PANEL TERMS OF REFERENCE ....
32
Annex 2 – RECCOMENDATION ITU-R M.540 .....................................................
34
Annex 3 – IMO RESOLUTION MSC.148(77) ........................................................
40
Annex 4 – EXTRACT FROM IMO RESOLUTION A.801(19) ANNEX 4 ................
44
Annex 5 – PROCEDURE FOR AMENDING THE NAVTEX MANUAL ..................
45
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1 – GENERAL INFORMATION
NAVTEX is an international automated direct-printing service for promulgation of navigational and meteorological warnings, meteorological forecasts and other urgent information to ships. It was developed to provide a low-cost, simple and automated means of receiving maritime safety information on board ships at sea in coastal waters. The information transmitted may be relevant to all sizes and types of vessel and the selective message-rejection feature ensures that every mariner can receive a safety information broadcast which is tailored to his particular needs.
NAVTEX fulfils an integral role in the Global Maritime Distress and Safety System (GMDSS) developed by the International Maritime Organization (IMO) and incorporated into the 1988 amendments to the International Convention for the Safety of Life at Sea (SOLAS), 1974, as amended, as a requirement for ships to which the Convention applies.
This Manual describes the structure and operation of the NAVTEX Service. It is intended primarily for use by Maritime Administrations and others concerned with the preparation and broadcasting of maritime safety information. It will also be of interest to seafarers, shipowners and others who need to receive such information in order to safely go about their business at sea. It should be used in conjunction with the Joint IMO/IHO/WMO Manual on Maritime Safety Information (also published as the IHO/IMO World-Wide Navigational Warning Service Guidance Document, IHO Publication S-53, and S-53 Appendix 1).
2 – NAVTEX SERVICE
2.1 Introduction
2.1.1 NAVTEX provides shipping with navigational and meteorological warnings, meteorological forecasts and other urgent information (as listed in Table 1, Section 5) by automatic display or print-out from a dedicated receiver. It is suitable for use in all sizes and types of ships. Figure 1 illustrates the way the service is typically structured.
2.1.2 NAVTEX is a component of the IMO/IHO World-Wide Navigational Warning Service (WWNWS) defined by IMO Assembly resolution A.706(l7), as amended, and the WMO Manual on Marine Meteorological Services, Part 1bis, Provision of warnings and weather and sea bulletins (GMDSS application). It has also been included as an element of the Global Maritime Distress and Safety System (GMDSS).
2.1.3 In the GMDSS, a NAVTEX receiving capability is part of the mandatory equipment which is required to be carried in certain vessels under the provisions of the International Convention for the Safety of Life at Sea (SOLAS), 1974, as amended.
2.1.4 Authority for co-ordinating the use of the frequencies 518 kHz, 490 kHz and 4209·5 kHz for NAVTEX services worldwide was effectively delegated by ITU to IMO at WRC-95 through Resolution 339. This was reaffirmed at WRC-97. IMO has vested responsibility for the overall management and co-ordination of the global NAVTEX services in its Co-ordinating Panel on NAVTEX Services. The co-ordination function of the panel with respect to National NAVTEX broadcasts on 490 kHz and 4209·5 kHz is limited to the allocation of transmission identification characters2. The Terms of Reference for this panel are attached
2 The transmitter identification character is a single letter allocated to each transmitter to identify the NAVTEX station and broadcast times.
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at Annex 1. It shall be noted that the provisions of the NAVTEX manual do not apply when planning a national NAVTEX service on other nationally assigned frequencies.
2.1.5 Details of operational and planned NAVTEX services are published periodically in the various national lists of radio signals, in an annex to the International Telecommunication Union's (ITU) List IV – List of coast stations and special service stations, and in the GMDSS Master Plan published by IMO in its series of GMDSS Circulars.
Figure 1 – Basic concept of the NAVTEX system
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2.2 Definitions
2.2.1 For the purposes of this manual, the following definitions apply:
.1 Coastal warning means a navigational warning or in-force bulletin promulgated as part of a numbered series by a National co-ordinator. Broadcast shall be made by the International NAVTEX service to defined NAVTEX service areas and/or by the International SafetyNET service to coastal warning areas. (In addition, Administrations may issue coastal warnings by other means).
.2 Coastal warning area means a unique and precisely defined sea area within a NAVAREA/METAREA or Sub-Area established by a coastal State for the purpose of co-ordinating the broadcast of coastal maritime safety information through the SafetyNET service.
.3 Global Maritime Distress and Safety System (GMDSS) means the global communications service based upon automated systems, both satellite and terrestrial, to provide distress alerting and promulgation of maritime safety information for mariners.
.4 HF NBDP means High Frequency narrow-band direct-printing, using radio telegraphy as defined in Recommendation ITU-R M.688.
.5 In-force bulletin means a list of serial numbers of those NAVAREA, Sub-Area or coastal warnings in force issued and broadcast by the NAVAREA Co-ordinator, Sub-Area Co-ordinator or National Co-ordinator during at least the previous six weeks.
.6 International NAVTEX service means the co-ordinated broadcast and automatic reception on 518 kHz of maritime safety information by means of narrow-band direct-printing telegraphy using the English language3.
.7 International SafetyNET service means the co-ordinated broadcasting and automated reception of maritime safety information via the Inmarsat Enhanced Group Call (EGC) system, using the English language, in accordance with the provisions of the International Convention for the Safety of Life at Sea, 1974, as amended.
.8 Local warning means a navigational warning which covers inshore waters, often within the limits of jurisdiction of a harbour or port authority.
.9 Maritime safety information (MSI)4 means navigational and meteorological warnings, meteorological forecasts and other urgent safety-related messages broadcast to ships.
.10 Maritime safety information service means the internationally and nationally co-ordinated network of broadcasts containing information which is necessary for safe navigation.
3 As set out in this Manual. 4 As defined in regulation IV/2 of the 1974 SOLAS Convention, as amended.
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.11 METAREA means a geographical sea area5 established for the purpose of co-ordinating the broadcast of marine meteorological information. The term METAREA followed by a roman numeral may be used to identify a particular sea area. The delimitation of such areas is not related to and shall not prejudice the delimitation of any boundaries between States.
.12 METAREA issuing service means the National Meteorological Service which has accepted responsibility for ensuring that meteorological forecasts and warnings for shipping are disseminated through the international SafetyNET and NAVTEX services to the designated area for which the Service has accepted responsibility under the broadcast requirements of the GMDSS6.
.13 Meteorological information means the marine meteorological warning and forecast information in accordance with the provisions of the International Convention for the Safety of Life at Sea, 1974, as amended.
.14 National Co-ordinator means the national authority charged with collating and issuing coastal warnings within a national area of responsibility.
.15 National NAVTEX service means the broadcast and automatic reception of maritime safety information by means of narrow-band direct-printing telegraphy using frequencies other than 518 kHz and languages as decided by the Administration concerned.
.16 National SafetyNET service means the broadcasting and automated reception of maritime safety information via the Inmarsat EGC system, using languages as decided by the Administration concerned.
.17 NAVAREA means a geographical sea area7 established for the purpose of co-ordinating the broadcast of navigational warnings. The term NAVAREA followed by a roman numeral may be used to identify a particular sea area. The delimitation of such areas is not related to and shall not prejudice the delimitation of any boundaries between States.
.18 NAVAREA Co-ordinator means the authority charged with co-ordinating, collating and issuing NAVAREA warnings for a designated NAVAREA.
.19 NAVAREA warning means a navigational warning or in-force bulletin promulgated as part of a numbered series by a NAVAREA Co-ordinator.
.20 Navigational warning means a message containing urgent information relevant to safe navigation broadcast to ships in accordance with the provisions of the International Convention for the Safety of Life at Sea, 1974, as amended.
.21 NAVTEX means the system for the broadcast and automatic reception of maritime safety information by means of narrow band direct-printing telegraphy8.
5 Which may include inland seas, lakes and waterways navigable by seagoing ships. 6 In the context of this manual, "designated area" means the NAVTEX service area. 7 Which may include inland seas, lakes and waterways navigable by seagoing ships. 8 See Annex 2.
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.22 NAVTEX coverage area means an area defined by an arc of a circle having a radius from the transmitter calculated according to the method and criteria given in IMO resolution A.801(19), Annex 4.
.23 NAVTEX service area means a unique and precisely defined sea area, wholly contained within the NAVTEX coverage area, for which maritime safety information is provided from a particular NAVTEX transmitter. It is normally defined by a line that takes full account of local propagation conditions and the character and volume of information and maritime traffic patterns in the region, as given in IMO resolution A.801(19), Annex 4.
.24 NAVTEX Co-ordinator means the authority charged with operating and managing one or more NAVTEX stations broadcasting maritime safety information as part of the International NAVTEX service.
.25 Other urgent safety-related information means maritime safety information broadcast to ships that is not defined as a navigational warning, meteorological information or SAR information. This may include, but is not limited to, significant malfunctions or changes to maritime communications systems, and new or amended mandatory ship reporting systems or maritime regulations affecting ships at sea.
.26 Rescue Co-ordination Centre (RCC) means a unit responsible for promoting efficient organization of search and rescue services and for co-ordinating the conduct of search and rescue operations within a search and rescue region.
.27 SafetyNET means the international service for the broadcasting and automatic reception of maritime safety information via the Inmarsat EGC system. SafetyNET receiving capability is part of the mandatory equipment which is required to be carried by certain ships in accordance with the provisions of the International Convention for the Safety of Life at Sea, 1974, as amended.
.28 SAR information means distress alert relays and other urgent search and rescue information broadcast to ships.
.29 Sub-Area means a sub-division of a NAVAREA/METAREA in which a number of countries have established a co-ordinated system for the promulgation of maritime safety information. The delimitation of such areas is not related to and shall not prejudice the delimitation of any boundaries between States.
.30 Sub-Area Co-ordinator means the authority charged with co-ordinating, collating and issuing Sub-Area warnings for a designated Sub-Area.
.31 Sub-Area warning means a navigational warning promulgated as part of a numbered series by a Sub-Area Co-ordinator. Broadcast shall be made by the International NAVTEX service to defined NAVTEX service areas or by the International SafetyNET service (through the appropriate NAVAREA Co-ordinator).
.32 UTC means Co-ordinated Universal Time which is equivalent to GMT (or ZULU) as the international time standard.
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.33 World-Wide Navigational Warning Service (WWNWS)9 means the internationally and nationally co-ordinated service for the promulgation of navigational warnings.
.34 In the operating procedures co-ordination means that the allocation of the time for data broadcast is centralized, the format and criteria of data transmissions are compliant as described in the Joint IMO/IHO/WMO Manual on Maritime Safety Information and that all services are managed as set out in IMO Assembly resolutions A.705(17) as amended and A.(706)17, as amended.
2.2.2 Delimitation of NAVAREAS
9 As set out in resolution A.706(17), as amended.
Figure 2 NAVAREAS for co-ordinating and promulgating navigational warnings The delimitation of such areas is not related to and shall not prejudice the delimitation of any boundaries between States.
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2.2.3 Delimitation of METAREAS
3 – GENERAL FEATURES OF NAVTEX SYSTEM
3.1 The principal features are:
.1 use of a single frequency, with transmissions from stations within and between NAVAREAs and METAREAs co-ordinated on a time-sharing basis to reduce the risk of mutual interference. The following frequencies may be used for NAVTEX broadcasts:
518 kHz
Type of service: International Content: Maritime safety information Language: English Co-ordination: By IMO NAVTEX Co-ordinating Panel
Figure 3 METAREAS for co-ordinating and promulgating meteorological warnings and forecasts The delimitation of such areas is not related to and shall not prejudice the delimitation of any boundaries between States.
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490 kHz and 4209·5 kHz
Type of service: National Content: Maritime safety information Language: As selected by the national administration Co-ordination: Transmitter identification character allocated by IMO NAVTEX Co-ordinating Panel
Other national frequencies allocated by the ITU
Type of service: National Content: As selected by the national administration Language: As selected by the national administration Co-ordination: By appropriate national administration
.2 a dedicated NAVTEX receiver, comprising radio receivers, a signal processor and either:
a) an integrated printing device; or b) a dedicated display device with a printer output port and a non-volatile message memory; or c) a connection to an integrated navigation system and a non-volatile message memory;
which has the ability to select messages to be printed, or viewed and stored in a memory according to:
a) a technical code (BlB2B3B4), which appears in the preamble of each message; and b) whether or not the particular message has already been printed/received;
3.2 The operational and technical characteristics of the NAVTEX system are contained in Recommendation ITU-R M.54010. Performance standards for shipborne equipment, if installed before 1 July 2005, are laid down in IMO Assembly resolution A.525(13). If installed on or after 1 July 2005, they should conform to IMO resolution MSC.148(77)11.
4 – PLANNING NAVTEX SERVICES
4.1 When planning NAVTEX services, it is strongly recommended that administrations obtain guidance at an early stage from IMO, through its NAVTEX Co-ordinating Panel. This may be particularly important when installation of new stations and/or purchase of new equipment is under consideration. Details of how to contact the Panel may be found at Annex 1.
4.2 International NAVTEX services on 518 kHz
When planning an International NAVTEX service it is essential to appreciate the high level of national and international co-ordination required. The central principles which should be borne in mind are as follows:
10 See Annex 2. 11 See Annex 3.
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.1 all NAVTEX stations are part of the strategic infrastructure of both the GMDSS and WWNWS.
.2 it is essential for the efficiency and effectiveness of the service that a minimum number of stations are used. This may require national administrations to either share facilities or promulgate information provided by administrations of other nations.
.3 each station shall contribute to the overall service in a co-ordinated way, bearing in mind the geographical area covered by each station and the effective co-ordination and control of information to be transmitted.
.4 the two basic areas which must be defined when establishing a NAVTEX station are the NAVTEX coverage area and the NAVTEX service area. Each station will provide all the information for a particular NAVTEX service area. The boundaries of the NAVTEX service area must be wholly contained within the coverage area, and must not overlap with adjacent NAVTEX service areas (see Figure 4).
.5 national administrations seeking to establish NAVTEX services shall undertake preliminary discussions with the NAVAREA Co-ordinator, METAREA Issuing Services and neighbouring administrations prior to formal application to IMO through the IMO NAVTEX Co-ordinating Panel. These discussions shall consider the most appropriate NAVTEX service area boundaries, possible geographical locations for transmitter sites to ensure optimal coverage and links with Information Providers.
.6 the range of a NAVTEX transmitter depends on the transmitted power and local radio propagation conditions. The actual range achieved shall be adjusted to the minimum required for adequate reception in the specified NAVTEX service area, taking into account the needs of ships approaching from other areas. Experience indicates that the required range of 250 to 400 nautical miles will normally be attained by transmitted power of no more than 1 kW during daylight with a 60% reduction during night conditions.
.7 after the choice of transmitter sites, the main need for co-ordination lies in the assignment of B1 transmitter identification characters (time schedules) and the agreement of proposed NAVTEX service areas (if appropriate). Preliminary discussions between national administrations seeking to establish or amend NAVTEX services and neighbouring administrations shall be co-ordinated by the NAVAREA Co-ordinator prior to formal application for a B1 transmitter identification character. Throughout the process the IMO NAVTEX Co-ordinating Panel is available to advise and liaise on the final limits of NAVTEX service areas if these cannot be agreed locally.
.8 the IMO NAVTEX Co-ordinating Panel will only allocate B1 transmitter identification characters after the NAVTEX service areas have been agreed.
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Figure 4 – Example of NAVTEX service areas The Baltic Sea and its approaches has been divided into four individual NAVTEX service areas. Within each service area, maritime safety information is provided from a separate NAVTEX station which has been allocated a dedicated B1 transmitter identification character. It is a fundamental requirement that the range of each NAVTEX transmitter is sufficient to include the whole of the NAVTEX service area assigned to its B1 transmitter identification character.
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.9 once a NAVTEX transmitter has been declared operational, if a national administration wishes to:
a) move the transmitter site; and/or b) amend the limits of its NAVTEX service area
then the whole co-ordination process outlined above must be repeated, keeping the NAVTEX Co-ordinating Panel informed at all times.
.10 a national NAVTEX Co-ordinator shall be established to oversee the operation of the NAVTEX services established by each national administration. The responsibilities of the NAVTEX Co-ordinator are defined in Section 12 of this Manual.
4.3 National NAVTEX services on 490 kHz or 4209·5 kHz
The provisions of the NAVTEX Manual apply to National NAVTEX Services on 490 kHz or 4209.5 kHz. When planning a National NAVTEX Service, the IMO NAVTEX Co-ordinating Panel is responsible for the allocation of B1 transmitter identification characters; however, the establishment of NAVTEX service areas and the compulsory use of the English language are not required.
4.4 National NAVTEX services on other frequencies
The provisions of the NAVTEX manual do not apply when planning a national NAVTEX service on nationally assigned frequencies.
5 – NAVTEX MESSAGE TECHNICAL CHARACTERS
5.1 Overview of technical characters, B1, B2, B3, B4
5.1.1 NAVTEX messages include instructions to the NAVTEX receiver for processing maritime safety information in the form of the NAVTEX message identity, which consists of four technical "B" characters which make up an alphanumeric code. In order for messages to be correctly processed, they must consist of data conforming to these B characters:
B1 Transmitter Identification Character B2 Subject Indicator Character B3B4 Message Numbering Characters
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B1 Transmitter Identification Character
B2 Subject Indicator Character
B3 B4 Message Numbering Characters 1 letter 1 letter 2 digits
A to X
A = Navigational warnings
01 to 99
(message numbering characters "00" are not to be used for routine messages)
B = Meteorological warnings C = Ice reports D12 = Search and rescue information, acts of piracy warnings, tsunamis and other natural phenomena E = Meteorological forecasts F = Pilot and VTS service messages G = AIS service messages (non navigational aid) H = LORAN messages I = currently not used J = GNSS messages K = Other electronic navigational aid system messages L = Other Navigational warnings – additional to B2 character A13 M = N = O = P = Q = R = S = T = U = V = W = X = Y = Z = No messages on hand
12 Use of B2 character D will automatically set off the alarm at the NAVTEX receiver. 13 On some older NAVTEX receivers it may be possible to deselect B2 character L (continuation of B2 subject group A), however, it is strongly recommended that this character is not deselected.
Special services allocation by the IMO NAVTEX Co-ordinating Panel
currently not used
Table 1 – Technical "B" characters which make up the full NAVTEX message identity
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5.2 B1 – Transmitter Identification Character
5.2.1 The transmitter identification character is a single letter which is allocated to each transmitter. It is used to identify the broadcasts which are to be accepted by the receiver and those to be rejected, and also the time slot for the transmission.
5.2.2 In order to avoid erroneous reception and interference of transmissions from two stations having the same transmitter identification character, it is necessary to ensure that such stations have a large geographical separation. Allocation of transmitter identification characters by alphabetical sequence to adjacent sites can also cause problems; hence, consecutive transmitter identification characters are not normally allocated to adjacent stations. Experience has shown that this removes the risk of a station which over-runs its time slot masking the phasing signal of an adjacent station which is about to begin its transmission.
5.2.2 NAVTEX transmissions have a designed maximum range of about 400 nautical miles. The minimum distance between two transmitters with the same transmitter identification identifier must, therefore, be sufficient to ensure that a receiver cannot be within range of both at the same time.
5.2.3 Close co-ordination between transmitting stations in adjacent NAVAREAs/METAREAs is necessary to achieve this separation. For this reason, national administrations shall request the advice of the IMO NAVTEX Co-ordinating Panel at an early stage in the planning of a new NAVTEX service. The Panel will allocate B1 transmitter identification characters in such a way as to minimize the risk of interference occurring.
Figure 5 – Example of NAVTEX receiver with LCD Screen
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5.2.5 Table 2 shows the transmitter identification characters and their associated transmission start times used by the IMO NAVTEX Co-ordinating Panel to evaluate and allocate transmitter identification characters A to X, regardless of the geographical position of the station anywhere in the world. Each transmitter identification character is allocated a maximum transmission time of 10 minutes every 4 hours. Because the NAVTEX system always utilizes a single frequency, it is fundamental to its successful operation that the following time slots are strictly adhered to, and that broadcasts do not overrun their allotted 10 minutes.
Transmitter identification character (B1)
Transmission start times (UTC)
A 0000 0400 0800 1200 1600 2000 B 0010 0410 0810 1210 1610 2010 C 0020 0420 0820 1220 1620 2020 D 0030 0430 0830 1230 1630 2030 E 0040 0440 0840 1240 1640 2040 F 0050 0450 0850 1250 1650 2050 G 0100 0500 0900 1300 1700 2100 H 0110 0510 0910 1310 1710 2110 I 0120 0520 0920 1320 1720 2120 J 0130 0530 0930 1330 1730 2130 K 0140 0540 0940 1340 1740 2140 L 0150 0550 0950 1350 1750 2150 M 0200 0600 1000 1400 1800 2200 N 0210 0610 1010 1410 1810 2210 O 0220 0620 1020 1420 1820 2220 P 0230 0630 1030 1430 1830 2230 Q 0240 0640 1040 1440 1840 2240 R 0250 0650 1050 1450 1850 2250 S 0300 0700 1100 1500 1900 2300 T 0310 0710 1110 1510 1910 2310 U 0320 0720 1120 1520 1920 2320 V 0330 0730 1130 1530 1930 2330 W 0340 0740 1140 1540 1940 2340 X 0350 0750 1150 1550 1950 2350
5.2.6 In some regions, it has become necessary to accommodate a large number of stations. In extreme cases, it has even been necessary to reuse some transmitter identification characters for a second time within a region. Where this occurs every effort is made to ensure stations with the same character are as far apart as possible to reduce the risk of mutual interference.
5.3 B2 – Subject Indicator Character
5.3.1 Information is grouped by subject in the NAVTEX broadcast and each subject group is allocated a B2 subject indicator character.
5.3.2 The subject indicator character is used by the receiver to identify the different classes of messages as listed in Table 1.
Table 2 – NAVTEX transmission start times
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5.3.3 Some subject indicator characters can be used to reject messages concerning certain subjects which may not be required by the ship (e.g., LORAN messages may be rejected by deselecting the B2 subject indicator character H on the NAVTEX receiver on board a ship which is not fitted with a LORAN receiver).
5.3.4 Reception of messages, transmitted using subject indicator characters A, B, D and L, which have been allocated for navigational warnings, meteorological warnings, search and rescue information, acts of piracy warnings, tsunamis and other natural phenomena, is mandatory and cannot be deselected on the NAVTEX receiver. This has been designed to ensure that ships using NAVTEX always receive the most essential information.
5.3.5 It is not possible to transmit or receive two NAVTEX messages with the same NAVTEX message identity (made up of the four technical characters). Therefore the B2 subject indicator character L has been designated for use in the unlikely event that a NAVTEX Co-ordinator has more than 99 navigational warning messages in force and requiring transmission at the same time, all using B2 subject indicator character A, with the same B1 transmitter identification character.
5.3.6 Messages received which have been transmitted using subject indicator character D will set off an alarm built into the NAVTEX receiver.
5.3.7 In the International NAVTEX Service, Administrations shall obtain the agreement of the IMO NAVTEX Co-ordinating Panel for all proposals for the use of special service subject indicator characters. Such proposals shall meet the following criteria:
.1 The full international service must remain unaffected.
.2 The special service broadcasts shall be transmitted only when time allows, and with due regard to the necessity for the frequency to remain unused for a high percentage of the time.
.3 The special service broadcast shall only be used for its approved purpose.
5.4 B3 B4 – Message Numbering Characters (NAVTEX Number)
5.4.1 Each message within each subject group, is allocated a two digit sequential serial number, beginning at 01 and ending at 99. The B3B4 message numbering characters together, are often referred to as the "NAVTEX number".
5.4.2 The NAVTEX number is solely allocated as a component of the NAVTEX message identity and should not be confused with (and bears no correlation to), the series identity and consecutive number of the NAVAREA or Coastal warning contained in the message.
5.4.3 Messages broadcast using NAVTEX number B3B4 = 00 cannot be rejected and will automatically override any selection of B1 transmitter identification characters as well as any B2 subject indicator characters selected on the NAVTEX receiver.
5.4.4 Use of NAVTEX number B3B4 = 00 must therefore be strictly controlled, since messages carrying it will always be printed or displayed every time they are received. Routine messages and service messages must never be allocated B3B4 = 00. The correct use of B2 characters A, B, D and L, will ensure that messages containing safety information will always be printed or displayed on first receipt.
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6 – MESSAGE IDENTITY
6.1 The individual NAVTEX message identity is the amalgamation of all four technical characters B1B2B3B4 (transmitter identification character/subject indicator character/message numbering characters).
6.2 When a message is received for the first time by a NAVTEX receiver, the message identity is recorded and stored in the memory for 72 hours. This ensures that subsequent transmissions of the same message are not re-printed or repeated in the display, unless they are re-received over 72 hours later. In the unlikely event that all 99 NAVTEX numbers for a particular subject group, from a particular transmitter, are in use at the same time, or have been allocated within the past 72 hours, an alternative B2 character must be utilized; for example, B2 = L has been set aside to be used for additional navigational warnings if all 99 NAVTEX numbers for subject group B2 = A are in use.
6.3 Each NAVTEX message identity shall be allocated by the relevant NAVTEX Co-ordinator, who is the authority responsible for the selection of information to be broadcast by each transmitter within each subject group. A single NAVTEX Co-ordinator may have more than one transmitter under their control. Specific advice on the use of alternative B2 subject indicator characters as mentioned in 6.2 above, can be provided by the IMO NAVTEX Co-ordinating Panel. 7 – MESSAGE FORMAT
7.1 NAVTEX messages must be composed in accordance to the guidelines contained in the Joint IMO/IHO/WMO Manual on Maritime Safety Information and IHO Publication S-53. The format of all messages shall be in strict accordance with Figure 6. This defines the essential elements of the messages which influence the operation of the receiver. Great care is required to avoid errors of syntax in the groups ZCZC B1B2B3B4 and NNNN as they will cause receivers to operate incorrectly, and may well result in messages not being received.
Figure 6 – Standard format for NAVTEX messages
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7.2 The phasing signal is automatically transmitted by the NAVTEX transmitter at the beginning of each message and is critical to the effective operation of the system. It is this signal which enables a receiver to lock-on to a particular station's transmission, providing the frequency is not already in use.
7.3 If another station within transmitting range and with a time slot prior to the station selected overruns its time slot (regardless of the B1 transmitter identification character in use), its transmission will blank the phasing signal of the subsequent transmitter. It will then seem to the receiver as if the second station is off the air and its broadcast will not be received, possibly denying the user significant safety information. This is the primary reason behind the importance of each station adhering to its allocated time slots. Similarly if the phasing signal for a particular station is too short, some receivers will be unable to lock on to the transmission.
7.4 Basic message elements:
Element Example Phasing signal Start of message group ZCZC One space NAVTEX message identity FA01 Carriage return + line feed
Message content
(Date Time Group – Optional e.g. 040735 UTC OCT 10) NAV I 114/10 ENGLISH CHANNEL. START POINT SOUTHWARD. CHART BA 442 (INT 1701). UNEXPLODED ORDNANCE LOCATED 49-51.97N 003-39.54W AND 49-55.24N 003-40.79W. End of message instruction NNNN Carriage return + two line feeds Phasing signal
7.5 When a message has been received error-free, a record is made by the receiver of the NAVTEX message identity. This unique identifier is used to suppress the printing or display of repeated transmissions of the same message.
7.6 On national NAVTEX services it is important to keep to the same basic message format as that required for the International NAVTEX service. It is also important to ensure that the full broadcast does not overrun the allocated time slot. However, in order to meet national requirements, message content may deviate from the guidelines provided for the International NAVTEX Service if required.
Table 3 – Basic message elements
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7.7 Examples of Navigational Warning messages
ZCZC LA18 140356 UTC AUG 10 NORWEGIAN NAV.WARNING 280 CHART 4 AREA OSLOFJORDEN TORPENE LIGHTBUOY 59-46.1N 010- 33.2E UNLIT NNNN
ZCZC LA26 250911 UTC JUN 10 DANISH NAVIGATIONAL WARNING NO. 154/10 KATTEGAT, AALBORG BIGHT LIGHTHOUSE SVITRINGEN RENDE NO.13 56-54.4N 010-30.6E DESTROYED AND MAKES AN OBSTRUCTION. DEPTH ABOVE FOUNDATION 1 METRE. THE POS. IS MARKED AS FOLLOWS: GREEN LIGHT BUOY Q.G. APPROX 50M SW YELLOW BUOY APPROX. 50M N YELLOW BUOY APPROX. 50M ESE MARINERS ARE ADVISED TO KEEP WELL CLEAR NNNN
ZCZC SA38 NAVTEX-HAMBURG (NCC) 131120 UTC SEP 10 NAV WARN NO. 428 TSS TERSCHELLING-GERMAN BIGHT 'TG 2/GW' LIGHTBUOY 53-52N 006-22E OFF STATION AND DAMAGED. NNNN
ZCZC TA93 151530 UTC JAN OOSTENDERADIO - INFO 17/10 1. OSTEND HARBOUR - WORKING AREA EASTERN BREAKWATER. ALL SHIPPING (EXCEPT GOVERNMENT VESSELS AND WORKBOATS INVOLVED IN THIS PROJECT) FORBIDDEN IN THE WORK ING AREA BOUNDED BY THE FOLLOWING POS: 51-14.278N 002-55.719E 51-14.424N 002-55.696E 51-14.840N 002-55.370E 51-14.579N 002-55.058E 51-14.462N 002-55.186E 51-14.381N 002-55.293E 51-14.253N 002-55.360E SHIPPING REQUESTED TO PASS WITH REDUCED SPEED 2. CANCEL INFO 121/09 NNNN
ZCZC KA79 AVURNAV CHERBOURG 098 DOVER STRAIT TSS AIS AID TO NAVIGATION MMSI NUMBER: 992271107 ETABLISHED ON ZC2 BOUY 50-53.6N 001-30.9E (WGS 84) NNNN
ZCZC MA99 301435 UTC AUG 10 WZ 972 ENGLAND, EAST COAST. THAMES ESTUARY. 1. EXPOSED CABLE EXISTS ON SEABED IN VICINITY OF LINE JOINING: 51-28.7N 000-46.8E 51-29.2N 001-01.7E 51-28.5N 001-09.5E 51-28.8N 001-14.0E 51-28.3N 001-18.6E AND 51-28.7N 001-25.2E. WIDE BERTH REQUESTED. 2. CANCEL WZ957 NNNN
ZCZC JA93 101200 UTC SEP GERMAN NAV WARN 424 WESTERN BALTIC. FEHMARN. PUTTGARDEN. UNDERWATER OPERATIONS BY 'DEEP DIVER 1/J8HC7', IN VICINITY OF: 54-32.8N 011-16.9E. GUARD VESSELS STANDING BY VHF CHANNEL 16. 0.5 NM BERTH REQUESTED NNNN
ZCZC MA97 291351 UTC AUG NAVAREA I 238/10 ENGLAND EAST COAST. THAMES ESTUARY APPROACHES. CHART BA 1138(INT 1561). WAVERIDER LIGHT-BUOY AND FOUR GUARD LIGHT-BUOYS, ALL FL (5) Y.20S, ESTABLISHED 51-42.5N 001-51.0E. WIDE BERTH REQUESTED. NNNN
ZCZC JA38 051444 UTC AUG KALININGRAD NAV WARN 097 SOUTHEASTERN BALTIC, KUSHKAYA KOSA LIGHT LESNOJ 55-01.0N 020-36.8E UNLIT NNNN
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7.8 Examples of Meteorological messages
OE35 ISSUED BY THE MET OFFICE AT 0620 ON TUESDAY 14 SEPTEMBER
GALE WARNINGS: LUNDY FASTNET IRISH SEA ROCKALL MALIN HEBRIDES BAILEY FAIR ISLE FAEROES SE ICELAND
THE GENERAL SITUATION AT MIDNIGHT LOW NE OF ICELAND 986, MOV SWWARDS, THEN SEWARDS, EXP N HEBRIDES 988 BY MIDNIGHT TONIGHT
24-HR FCSTS
LUNDY FASTNET SW VEER NW 5 TO 7, OCNL GALE 8 AT FIRST. ROUGH. RAIN, FAIR LATER. MOD OR POOR, BECMG GOOD
IRISH SEA SW VEER NW 5 TO 7, OCNL GALE 8, PERHAPS SEV GALE 9 LATER. ROUGH. RAIN THEN SQUALLY SHWRS. MOD OR GOOD, OCNL POOR AT FIRST
ROCKALL MALIN HEBRIDES BAILEY W 6 TO GALE 8, OCNL SEV GALE 9, VEER NW LATER. VERY ROUGH OR HIGH. SQUALLY SHWRS. MOD OR GOOD, OCNL POOR
FAIR ISLE FAEROES SW 5 TO 7, OCNL GALE 8 IN S, VEER N 5 OR 6 LATER. ROUGH BECMG VERY ROUGH OR HIGH. SQUALLY SHWRS. MOD OR GOOD
SE ICELAND SW BECMG CYCLONIC, THEN N 5 TO 7, INCR GALE 8 LATER. ROUGH, BECMG VERY ROUGH IN S. SQUALLY SHWRS. MOD OR GOOD, OCNL POOR
OUTLOOK FLW 24 HOURS: STRG WINDS EXP IN LUNDY AND FASTNET. GALES EXP IN ALL OTHER AREAS WITH SEV GALES IN IRISH SEA, MALIN, HEBRIDES AND SE ICELAND
IB54 WWJP73 RJTD 140600 IMPORTANT WARNING FOR YOKOHAMA NAVTEX AREA 140600 UTC ISSUED AT 140900 UTC
LOW 1002HPA AT 38N 150E MOVING SE 10 KNOTS COLD FRONT FROM 38N 150E TO 34N 143E 31N 139E 30N 133E STATIONARY FRONT FROM 30N 133E TO 30N 127E 31N 122E 31N 119E
WARNING(NEAR GALE) EASTERN SEA OFF SANRIKU
WARNING(DENSE FOG) EASTERN SEA OFF SANRIKU POOR VISIBILITY 0.3 MILES OR LESS IN PLACES
NEXT WARNING WILL BE ISSUED BEFORE 141500 UTC
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8 – LANGUAGE AND NATIONAL BROADCAST OPTIONS
8.1 International NAVTEX Service messages on 518 kHz shall be broadcast only in English.
8.2 There is often a requirement for NAVTEX broadcasts to be made in national languages in addition to English. This shall only be achieved by the provision of a national NAVTEX service. National NAVTEX services use frequencies other than 518 kHz, and languages as decided by the Administrations concerned. These National NAVTEX services may be broadcast on 490 kHz or 4209·5 kHz, or on an alternative nationally assigned frequency.
9 – INFORMATION CONTROL
9.1 The time-shared nature of NAVTEX services imposes the need for strict discipline in controlling the information flow of the broadcast. To achieve this, it is necessary to co-ordinate the messages in each B2 category at each transmitter. In general, all messages shall be brief and clear and avoid duplication. Strict adherence to relevant guidelines such as those in IMO Assembly resolution A.706(17), as amended, the Joint IMO/IHO/WMO Manual on Maritime Safety Information and the WMO Manual on Marine Meteorological Services, Part 1bis, Provision of warnings and weather and sea bulletins (GMDSS application) is recommended, but certain additional operating procedures have also been found necessary:
.1 messages in each category shall be broadcast in reverse order of receipt by the NAVTEX Co-ordinator, with the latest being broadcast first; and
.2 cancellation messages shall be broadcast once only. The cancelled message shall not be transmitted on the broadcast in which its cancellation message appears.
10 – MESSAGE CONTENT
10.1 It is important that national administrations operating or planning NAVTEX services are quite clear about what sort of information shall or shall not be included in the messages.
10.2 The International NAVTEX service shall be used for transmitting maritime safety information only and shall NOT be used as a medium for providing Notices to Mariners or for broadcasting Local Warnings. NAVTEX is essentially a medium for broadcasting information that is needed by ships to safely navigate through the NAVTEX service area of the appropriate NAVTEX station, particularly those ships on coastal passages. More detailed guidance in respect to different classes of messages is given below. Examples of the content and layout of NAVTEX messages are shown in the Joint IMO/IHO/WMO Manual on Maritime Safety Information. This publication shall be available to all personnel responsible for the drafting of messages to be broadcast by NAVTEX stations.
10.2.1 Navigational warnings
.1 coastal warnings and NAVAREA warnings (B2 = A or L) issued under the guidance of IMO Assembly resolution A.706(17), as amended, which would be of concern to ships in the NAVTEX service area allocated to the transmitter shall be included in the broadcast. Relevant coastal warnings shall normally be repeated at every scheduled transmission for as long as they remain in force; however, if they are readily available to mariners by other official means, for example in Notices to Mariners, then after a period of six weeks they may
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no longer be broadcast. NAVTEX Co-ordinators shall arrange to receive NAVAREA warnings appropriate to their area for inclusion in their broadcasts. These shall be broadcast at least twice each day – to avoid overloading the broadcast time slot, they shall normally be scheduled for transmission during slots that do not include weather forecasts (see 12.4);
.2 a summary of navigational warnings remaining in force shall normally be broadcast each week; and
.3 local warnings shall not be broadcast on NAVTEX, i.e. information relating to inshore waters, often within the limits of jurisdiction of a harbour or port authority, as defined in IMO Assembly resolution A.706(17), as amended.
10.2.2 Meteorological warnings and forecasts
.1 meteorological warnings (B2 = B), e.g., gale warnings, shall be allocated a priority of IMPORTANT (see Section 11) and be repeated at subsequent scheduled transmissions for as long as the warning is in force. These messages shall contain only the appropriate warnings and shall be separate from the weather forecasts;
.2 weather forecasts (B2 = E) shall be broadcast at least twice each day. This service shall be carefully co-ordinated where transmitters are geographically close together;
.3 routine ice reports are normally broadcast on NAVTEX once a day; and
.4 ice accretion warnings (icing warnings) are normally included in gale warnings. If no gale warning is issued, they are to be treated as a meteorological warning (see 10.2.2.1).
10.2.3 Search and rescue information
.1 the NAVTEX broadcast is not suitable for distress traffic. Therefore, only the initial distress message shall be retransmitted on NAVTEX, using B2 = D, in order to alert mariners to a distress situation, by setting off an audio alarm.
.2 a single authority, which will normally be a Maritime Rescue Co-ordination Centre (MRCC), shall be designated SAR Co-ordinator to input information via the NAVTEX Co-ordinator, for a NAVTEX message. The initial shore-to-ship distress-related message shall have previously been broadcast on the appropriate distress frequency prior to any related NAVTEX message being broadcast.
10.2.4 Piracy attack warnings
Piracy attack warnings shall be transmitted using B2 = D, in order to alert mariners by setting off an audio alarm. They shall be broadcast immediately on receipt and at subsequent scheduled transmissions.
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10.2.5 Tsunamis and other natural phenomena warning messages
Tsunami warnings, and negative tidal surge warnings shall be transmitted using B2 = D, in order to alert mariners by setting off an audio alarm. They shall be broadcast immediately on receipt and at subsequent scheduled transmissions.
10.2.6 Pilot and VTS service messages
Technical subject indicator character B2 = F, is only to be used for broadcasting temporary alterations, movement or suspension to pilot or VTS services. This category is for the information of all ships and is not to be used for specific instructions to individual ships or pilots.
10.2.7 No messages on hand
When there are no NAVTEX messages to be disseminated at a scheduled broadcast time, a brief message shall be transmitted to advise the mariner that there is no message traffic on hand. Technical subject indicator character B2 = Z is to be used to announce "NO MESSAGES ON HAND".
10.2.8 Use of abbreviations
Common examples of abbreviations used in the international NAVTEX service are contained in the Joint IMO/IHO/WMO manual on Maritime Safety Information.
10.2.9 National NAVTEX services
Transmissions on 490 kHz or 4209·5 kHz, may simply repeat the messages broadcast over the International NAVTEX service but in a national language, or they may be tailored to meet particular national requirements, for example by providing different or additional information to that broadcast on the International NAVTEX service, targeted at recreational vessels or fishing fleets.
11 – MESSAGE PRIORITIES AND BROADCAST PROCEDURES IN THE INTERNATIONAL NAVTEX SERVICE
11.1 Message priorities
11.1.1 The message originator is responsible for assessing the urgency of the information and inserting the appropriate priority marking. One of three message priorities is used to dictate the timing of the first broadcast of a new warning in the NAVTEX service. In descending order of urgency, they are:
VITAL for immediate broadcast, subject to avoiding interference to ongoing transmissions. Such messages shall also be passed to the appropriate NAVAREA Co-ordinator for possible transmission as a NAVAREA message via SafetyNET; IMPORTANT for broadcast at the next available period when the frequency is unused; and ROUTINE for broadcast at the next scheduled transmission.
11.1.2 Both VITAL and IMPORTANT messages shall be repeated, at least once at the next scheduled transmission time slot, if the situation is still extant.
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11.1.3 The message priority is a procedural instruction for the NAVTEX Co-ordinator or the transmitting station and shall not be included in the message. By selecting the appropriate priority of VITAL, IMPORTANT or ROUTINE at the transmission terminal, the message will be broadcast with the correct priority.
11.1.4 In order to avoid unnecessary disruption to the service, the priority marking VITAL is to be used only in cases of extreme urgency, i.e. to relay an initial shore-to-ship distress-related message or acts of piracy warnings, tsunamis and other natural phenomena warnings. In addition, VITAL messages are to be kept as brief as possible. The information provider is responsible for ensuring that the NAVTEX Co-ordinator is fully and immediately aware when a message shall be broadcast with the priority of VITAL.
11.1.5 VITAL messages will normally be broadcast using NAVTEX number B3B4 = 00.
11.2 Broadcast procedures
.1 VITAL priority messages.
Messages assessed as VITAL, are to be broadcast immediately, subject to avoiding interference to ongoing transmissions. On receipt of a message with a VITAL priority, the NAVTEX Co-ordinator will commence monitoring the NAVTEX frequency. If the frequency is clear, the VITAL message is to be transmitted immediately. If the frequency is in use, the Co-ordinator shall contact the station which, according to the schedule, will be transmitting during the following time slot and ask it to postpone their transmission start by one minute, to allow a space for the VITAL message. Once the VITAL message has been transmitted, the scheduled station is free to start its routine transmissions;
.2 IMPORTANT priority messages.
Messages assessed as IMPORTANT, are to be broadcast during the next available period when the NAVTEX frequency is unused. This is to be identified by monitoring the frequency. It is expected that this level of priority will be sufficient for the majority of urgent information; and
.3 ROUTINE priority messages.
Messages assessed as ROUTINE, are to be broadcast at the next scheduled transmission time. This level of priority will be appropriate for almost all messages broadcast on NAVTEX and is always to be used unless special circumstances dictate the use of the procedures for an IMPORTANT or VITAL priority message.
11.3 Meteorological NAVTEX Messages
The following priorities shall be assigned to meteorological NAVTEX messages:
a) Meteorological forecasts = ROUTINE priority b) Meteorological warnings = IMPORTANT priority c) Tsunami warnings = VITAL priority d) For other natural phenomena warnings, either IMPORTANT or VITAL priorities may be used.
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11.4 National NAVTEX Services
The broadcast procedures concerning differing message priorities are the same for both the International and National NAVTEX services.
12 – RESPONSIBILITIES OF A NAVTEX CO-ORDINATOR
12.1 The NAVTEX Co-ordinator is responsible for the messages transmitted by each station under their control. This responsibility includes checking that the content of each message is in accordance with the Joint IMO/IHO/WMO Manual on Maritime Safety Information and also, that it is relevant to the NAVTEX service area of the transmitting station. Thus a user may choose to accept messages, as appropriate, either from the single transmitter which serves the sea area around their position or from a number of transmitters. Ideally, the user should select the station within whose coverage area their vessel is currently operating and the station into whose coverage area their vessel will transit next.
12.2 The NAVTEX Co-ordinator must:
.1 act as the central point of contact on matters relating to NAVTEX transmissions for a given transmitter or number of transmitters;
.2 be responsible for continuously ensuring quality-control for the operation of the NAVTEX transmitting stations under its jurisdiction. This shall be achieved with the co-operation of the information providers to ensure that:
a) messages are always concise and can be transmitted within the designated 10 minute time slots assigned by the IMO NAVTEX Co-ordinating Panel;
b) MINIMUM power is used to achieve satisfactory range performance; and
c) the co-ordinated service is operating satisfactorily;
.3 assess all requests for NAVTEX messages immediately upon receipt;
.4 schedule each message for broadcast in accordance with the requested priority of VITAL, IMPORTANT or ROUTINE;
.5 monitor the international NAVTEX frequency along with any other National frequency used by the transmitters under their jurisdiction in order to ensure that the messages have been correctly broadcast;
.6 monitor the international NAVTEX frequency along with any other National frequency used in order to identify vacant transmission periods required for VITAL or IMPORTANT messages;
.7 pass maritime safety information which warrants promulgation outside of their NAVTEX service area directly to the appropriate authority, using the quickest possible means;
.8 allocate a message identity to each message, including the sequential NAVTEX number;
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.9 ensure that NAVTEX messages which have been cancelled are removed from the broadcast schedule at the same time as the cancellation message is promulgated;
.10 promote and oversee the use of established international standards and practices with respect to the format and protocols associated with NAVTEX messages;
.11 maintain records of source data relating to NAVTEX messages in accordance with the requirement of the National Administration of the NAVAREA Co-ordinator;
.12 be aware of the responsibilities of a NAVAREA, Sub-area and National Co-ordinator contained in IMO resolution A.706(17), as amended, paying particular attention to the specific guidance for the promulgation of internationally co-ordinated maritime safety information provided there-in; and
.13 take into account the need for contingency planning
12.3 Management of the service
.1 Data priority:
Most information broadcast on NAVTEX services relates to either Navigational Warnings or Meteorological Information. These types of information often originate from different organizations within a country and it is not until they arrive with the NAVTEX Co-ordinator that an assessment can be made as to whether there is too much information for the relevant broadcast time slot. Each data provider may consider their data to be more important and therefore, require transmission in full. However, the NAVTEX Co-ordinator needs to control the overall volume of data broadcast and may need to refer back to data providers to prioritise their information and reduce the amount of data to be broadcast. Some NAVTEX Co-ordinators utilize digital systems which include software that provides a readout of predicted transmission times for data held ready for broadcast. This enables the Co-ordinator to anticipate any problems and take action before the scheduled broadcast.
Data to meet purely national requirements shall not be broadcast on the International NAVTEX service, but shall be migrated to a national NAVTEX service (see section 14).
.2 Data formatting:
The period of each transmission shall be kept to a minimum by strictly formatting messages and avoiding the use of free text whenever possible.
12.4 Balancing the volume of data to be broadcast throughout the daily transmission cycle
For many categories of message there is no option with regards to when they shall be transmitted. However, in order to minimize the risk of over-running the allocated 10-minute time slot, it is possible to balance the overall length of transmissions by broadcasting NAVAREA warnings at different times from weather forecasts and the weekly summary of navigation warnings in force. An example of how this may be managed is given below for a station with a B1 transmitter identification character C:
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Time Slot Content
0020-0030 coastal warnings NAVAREA warnings 0420-0430 coastal warnings summary of navigational warnings in-force (once/week only) 0820-0830 coastal warnings weather forecasts 1220-1230 coastal warnings NAVAREA warnings 1620-1630 coastal warnings ice reports 2020-2030 coastal warnings weather forecasts
13 – BEST PRACTICE FOR THOSE USING THE SERVICE
13.1 In order to ensure that all necessary maritime safety information has been received, it is recommended that the NAVTEX receiver is switched on at least 12 hours before sailing, or preferably left on at all times.
13.2 Logging. The reception of weather forecasts or navigational warnings on NAVTEX does not need to be noted in the radio log; the NAVTEX printout (or the non-volatile message memory) satisfies the requirements of regulation 17 of chapter IV of the 1974 SOLAS Convention, as amended.
14 – MUTUAL INTERFERENCE BETWEEN NAVTEX STATIONS
14.1 The two principal causes of interference are:
a) transmission overruns; and b) excessive power output.
14.2 Although NAVTEX continues to be generally reliable and an effective medium for the promulgation of maritime safety information, the world-wide infrastructure continues to expand and the volume of information that each Administration disseminates through the international NAVTEX service continues to increase. There is a danger that in some geographical areas, without firm management, both the system and system users may become overloaded with information on the single frequency used. This is of particular importance when handling messages of VITAL priority.
14.3 Many stations are filling their allotted 10-minute time slots and an increasing number are over-running. Instances of interference with neighbouring stations, as a result of over-running the time allocation, are also increasing. Where adjacent stations have transmitter identification characters which follow alphabetically (i.e. adjacent time slots), if the first station over runs, it may mask the phasing signal of the second station such that, to the user, it seems as if the second station is off the air. Safety-critical information from the second station, although broadcast, may not be received by the system users. Over-run is usually caused by one or more of the following which must be avoided at all costs, preferably by controlling the volume of data broadcast:
.1 a significant increase in safety-critical activity such as cable laying. Navigational warnings promulgating such activity often include numerous waypoints which are listed by Latitude and Longitude;
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.2 meteorological information provided in a manner which is not concise and easily assimilated by the system user or for a much wider area than is covered by the NAVTEX station; and
.3 additional information provided for non-SOLAS system users, e.g., longer-range weather forecasts for fishing and recreational vessels.
14.4 As the GMDSS spreads to non-SOLAS mariners, their requirements for information are often different from the SOLAS ships and may be determined at a national level. SOLAS ships trading internationally usually pass through the area of coverage of a NAVTEX transmitter in a day; for them a 24-hour weather forecast usually suffices. However, fishing vessels and recreational vessels often remain in the same vicinity for several days and may require much longer range forecasts which take up more transmission time.
14.5 In order to keep the quantity of information that is broadcast on 518 kHz to manageable levels and to reduce avoidable interference on this frequency, Administrations must:
.1 monitor the volume of data broadcast and, together with adjacent Administrations, actively manage the system to ensure that interference caused by over-running allocated time slots is eliminated; and
.2 transmit non-English language broadcasts for SOLAS vessels and broadcasts of information provided specifically for non-SOLAS vessels on 490 kHz or 4209·5 kHz as required. B1 characters for these frequencies will be allocated by the IMO NAVTEX Co-ordinating Panel, on request.
14.6 Excessive power output also causes interference between stations with the same B1 transmitter identification character/time slot, but located in different regions. This has particularly been identified at night, as the number of operational NAVTEX stations increases. Occasionally, this can be caused by atmospheric conditions, but is generally caused by excessive power output from one of the stations. It is recommended that Administrations restrict the power output from their transmitters to that required to cover the designated NAVTEX service area, particularly at night, in order to avoid interference. As a general rule, transmitted power shall not exceed 1 kW by day and 300 watts by night.
14.7 When interference is detected, particularly when it affects the service to system users, the matter shall be addressed immediately. When the interference is with adjacent stations, attempts shall be made to resolve the problem locally. Advice may also be sought from the NAVAREA Co-ordinator. If this is unsuccessful, the IMO NAVTEX Co-ordinating Panel shall be alerted to the problem and their advice sought. When the interference is from a station with the same B1 character in a different area, the NAVTEX Co-ordinating Panel must be contacted and they will initiate any necessary investigation/action.
15 – NOTIFICATION OF NAVTEX SERVICES
15.1 National Administrations shall ensure that mariners are informed of the establishment of, and/or changes to, NAVTEX services by inclusion of full details in Notices to Mariners and lists of radio signals. In addition, full details shall be forwarded to the appropriate NAVAREA Co-ordinator, METAREA Issuing Service and:
• International Maritime Organization • International Telecommunication Union 4 Albert Embankment Radiocommunication Bureau London SE1 7SR Place des Nations United Kingdom 1211 Genève 20 Switzerland
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Annex 1 IMO NAVTEX Co-ordinating Panel Terms of Reference
1 Terms of Reference
.1 advise Administrations planning to implement a NAVTEX service on the frequencies 518 kHz, 490 kHz or 4209·5 kHz, on the operational aspects of the system. In particular, advise on the optimum number of stations, the allocation of transmission identifying characters (B1) and broadcast message criteria;
.2 co-ordinate with Administrations over the operational aspects of NAVTEX in the planning stages in order to prevent mutual interference owing to the number of stations, transmitter power, or transmission identifying character assignment;
.3 remain aware of system problems which arise, through reports from sea and correspondence with operational NAVTEX Co-ordinators. When problems are identified, liaise with appropriate Administrations involved, NAVAREA Co-ordinators, METAREA Issuing Services, the Sub-Committee, IHO or WMO, as appropriate, recommend solutions or mitigating measures and, when agreed, co-ordinate their implementation; and
.4 prepare documentation supporting the system for the Sub-Committee, including both that needed by Administrations to guide their operations, and that needed to inform the user of the service (mariner, shipowner and operator).
2 Contact addresses
The NAVTEX Co-ordinating Panel can be contacted at the following addresses:
The Chairman IMO NAVTEX Co-ordinating Panel International Maritime Organization 4 Albert Embankment London SE1 7SR United Kingdom
Telephone: +44 (0)20 7735 7611 Telefax: +44 (0)20 7587 3210 E-mail: info@imo.org
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3 Panel membership and participation
3.1 The IMO NAVTEX Co-ordinating Panel is open to membership by all Member Governments and also includes one member nominated by each of the following international organizations:
i) International Maritime Organization (IMO) ii) World Meteorological Organization (WMO) iii) International Hydrographic Organization (IHO) iv) International Mobile Satellite Organization (IMSO)
3.2 The following may be represented as observers on the panel:
i) IHO World-Wide Navigational Warnings Service Sub-Committee ii) International SafetyNET Co-ordinating Panel iii) Expert Team on Maritime Safety Services (ETMSS) of the WMO/IOC Joint Technical Commission for Oceanography and Marine Meteorology (JCOMM)
3.3 The work of the Panel is conducted mainly by correspondence. Meetings, when appropriate, are announced in advance and normally scheduled to be held in the margins of other IMO or IHO meetings.
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Annex 2
RECOMMENDATION ITU-R M.540
Operational and Technical Characteristics for an Automated Direct-Printing Telegraph System for Promulgation of Navigational and Meteorological Warnings and Urgent Information to Ships
(Question 5/8)
The CCIR,† (1978-1982-1990)
CONSIDERING
(a) that the availability of navigational and meteorological warnings and urgent information on board ships is of great importance for safety;
(b) that the existing radiocommunication system for promulgation of navigational and meteorological warnings and urgent information to ships can be improved by use of modern techniques;
(c) that the IMO has established the following definitions on the promulgation of maritime safety information:
• NAVTEX means the system for the broadcast and automatic reception of maritime safety information by means of narrow-band direct-printing telegraphy;
• international NAVTEX service means the co-ordinated broadcast and automatic reception on 518 kHz of maritime safety information by means of narrow-band direct-printing telegraphy using the English language, as set out in the NAVTEX manual, published by the IMO;
• national NAVTEX service means the broadcast and automatic reception of maritime safety information by means of narrow-band direct-printing telegraphy using frequencies and languages as decided by the Administrations concerned;
(d) that the 1988 Amendments to the International Convention for the Safety of Life at Sea, 1974, require that every ship to which the Convention applies shall be provided with a receiver capable of receiving international NAVTEX service broadcasts;
(e) that several countries are operating a co-ordinated international NAVTEX service based on narrow-band direct-printing in accordance with Article 14A of the Radio Regulations;
(f) that the system should be applicable to the maritime mobile service (both international and national);
† The name "CCIR" was changed to "Radiocommunication Bureau" by the reorganization of the International Telecommunication Union on 1 March 1993.
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(g) that it is desirable that the service fulfils the requirements of all types of ships desiring to use it;
(h) that although each area may need specific guidance, the use of standard technical and operational characteristics would facilitate the extension of the service,
UNANIMOUSLY RECOMMENDS
1. that the operational characteristics for the promulgation of navigational and meteorological warnings and urgent information using NBDP should be in accordance with Annex I;
2. that the technical characteristics for the promulgation of navigational and meteorological warnings and urgent information using NBDP should be in accordance with Annex II.
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Annex I to Recommendation ITU-R M.540
OPERATIONAL CHARACTERISTICS
1 Narrow-band direct-printing techniques should be used for an automated telegraph system for promulgation of navigational and meteorological warnings and urgent information to ships. Common frequencies for such transmissions should be internationally agreed upon and the frequency 518 kHz has been designated for world-wide use in the international NAVTEX service (see Radio Regulations Nos. 474, 2971B and N2971B).
1.1 For national NAVTEX services Administrations should also utilize the format of this Recommendation on the appropriate frequencies as defined in the Radio Regulations.
2 The radiated power from the coast station transmitter should only be that sufficient to cover the intended service area of that coast station. The range extension occurring during night hours should also be considered.
3 The information transmitted should primarily be of the type used for coastal waters preferably using a single frequency (Resolution No. 324 (Mob-87)).
4 The transmission time allocated to each station should be restricted to that which is adequate for the anticipated messages to be broadcast to the area concerned.
5 Scheduled broadcasts should take place at intervals not exceeding eight hours and be co-ordinated, to avoid interference with broadcasts from other stations.
6 Message priorities
6.1 Three message priorities are used to dictate the timing of the first broadcast of a new warning in the NAVTEX service. In descending order of urgency they are:
VITAL: for immediate broadcast, subject to avoiding interference to ongoing transmissions;
IMPORTANT: for broadcast at the next available period when the frequency is unused; and
ROUTINE: for broadcast at the next scheduled transmission period.
Note: Both VITAL and IMPORTANT warnings will normally need to be repeated, if still valid, at the next scheduled transmission period.
6.2 In order to avoid unnecessary disruption to the service, the priority marking VITAL is to be used only in cases of extreme urgency, such as some distress alerts. In addition, VITAL messages are to be kept as brief as possible.
6.3 Periods should be scheduled between the regular transmission periods permitting immediate/early transmission of VITAL messages.
6.4 By use of the message serial number 00 in the preamble of a message (see also Annex 11 § 6) it is possible to override any exclusion of coast stations or of message types which might have been made in the receiving equipment.
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7 Initial shore-to-ship distress-related messages should first be broadcast on the appropriate distress frequency by coast stations in whose SAR area distress cases are handled.
8 Participating transmitting stations should be provided with monitoring facilities to enable them to:
 monitor their own transmissions as to signal quality and transmission format;  confirm that the channel is not occupied.
9 In case a message is repeated by more than one transmitting station within the same NAVTEX region (e.g., for better coverage) the original preamble B1~B4 (see annex II) should be used.
10 In order to avoid overloading of the channel it is desirable to use a single language and where a single language is used it shall be English.
11 Dedicated onboard equipment is recommended.
12 Other operational characteristics and detailed guidance are given in the NAVTEX Manual developed by the International Maritime Organization.
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Annex II to Recommendation ITU-R M.540
TECHNICAL CHARACTERISTICS
1 The signals transmitted should be in conformity with the collective B-mode of the direct-printing system specified in Recommendations 476 and 625.
2 The technical format of the transmission should be as follows:
in which ZCZC defines the end of the phasing period,
the B1 character is a letter (A-Z)14 identifying the transmitter coverage area,
the B2 character is a letter (A-Z) for each type of message.
2.1 Both the B1 characters identifying the different transmitter coverage areas and the B2 characters identifying the different types of messages are defined by IMO and chosen from Table I of Recommendations 476 and 625, combination numbers 1-26.
2.1.1 Ship equipment should be capable of automatically rejecting unwanted information using character B1.
2.1.2 Ship equipment should be capable of disabling print-out of selected types of messages using character B2 with the exception of messages with B2 characters A, B, and D15 (see also § 2.1).
2.1.3 If any facility is rejected or disabled in § 2.1.1 and 2.1.2 above, the extent of any such limitation must be clearly indicated to the user.
2.2 B 3B4 is a two-character serial number for each B2, starting with 01 except in special cases where the serial number 00 is used (see § 6 below).
2.3 The characters ZCZC B1B2B3B4 need not be printed.
3 The printer should only be activated if the preamble B1~B4 is received without errors.
14 Only letters A-X are used on 518 kHz, 490 kHz and 4209·5 kHz, see Table 2 of the NAVTEX Manual. 15 B2 character L (continuation of B2 subject group A), shall also not be capable of being suppressed (see IEC 61097-6).
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4 Facilities should be provided to avoid printing of the same message several times on the same ship, when such a message has already been satisfactorily received.
5 The necessary information for the measures under § 4 above should be deduced from the sequence B1B2B3B4 and from the message.
6 A message should always be printed if B3B4 = 00.
7 Extra (redundant) letter and figure shifts should be used in the message to reduce garbling.
8 In case a message is repeated by another transmitting station (e.g., for better coverage) the original preamble B1~B4 should be used.
9 The equipment on board ships should be neither unduly complex or expensive.
10 The transmitter frequency tolerance for the mark and the space signals should be better than + 10 Hz.
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Annex 3
IMO RESOLUTION MSC.148(77) (adopted on 3 June 2003)
Adoption of the Revised Performance Standards for Narrow-Band Direct-Printing Telegraph Equipment for the Reception of Navigational and Meteorological Warnings and Urgent Information to Ships (NAVTEX)
THE MARITIME SAFETY COMMITTEE,
RECALLING Article 28(b) of the Convention on the International Maritime Organization concerning the functions of the Committee,
RECALLING ALSO resolution A.886(21), by which the Assembly resolved that the functions of adopting performance standards for radio and navigational equipment, as well as amendments thereto, shall be performed by the Maritime Safety Committee on behalf of the Organization,
NOTING the carriage requirement in SOLAS chapter IV/7.1.4 for a receiver capable of receiving International NAVTEX narrow-band direct-printing (NBDP) broadcasts for the promulgation of navigational and meteorological warnings to shipping,
NOTING FURTHER the success of the International NAVTEX service in the promulgation of Maritime Safety Information (MSI),
NOTING ALSO with regard to the enhanced storage, processing and display possibilities offered by recent technical advances,
CONSIDERING that further growth in information promulgated to ships will be constrained by the capacity of the International NAVTEX service and the increasing importance of National NAVTEX services,
HAVING CONSIDERED the recommendations on the revision of resolution A.525(13) MSC.148(77) made by the Sub-Committee on Radiocommunications and Search and Rescue at its seventh session,
1. ADOPTS the revised Recommendation on Performance Standards for Narrow-Band Direct-Printing Telegraph Equipment for the Reception of Navigational and Meteorological Warnings and Urgent Information to Ships (NAVTEX), set out in the Annex to the present resolution;
2. RECOMMENDS Governments to ensure that NAVTEX receiver equipment:
(a) if installed on or after 1 July 2005 conforms to performance standards not inferior to those specified in the Annex to the present resolution;
(b) if installed before 1 July 2005, conforms to performance standards not inferior to those specified in the Annex to resolution A.525(13).
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Annex to IMO RESOLUTION MSC.148(77)
Revised recommendation on performance standards for Narrow-band direct-printing telegraph equipment for The reception of navigational and meteorological Warnings and urgent information to ships (NAVTEX)
1 INTRODUCTION
1.1 The equipment, in addition to meeting the requirements of the Radio Regulations, the provisions of Recommendation ITU-R M.540 applicable to shipborne equipment and the general requirements set out in resolution A.694(17), should comply with the following performance standards.
2 GENERAL
2.1 The equipment should comprise radio receivers, a signal processor and:
either:
.1 an integrated printing device; or
.2 a dedicated display device1, printer output port and a non-volatile message memory; or
.3 a connection to an integrated navigation system and a non-volatile message memory.
3 CONTROLS AND INDICATORS
3.1 Details of the coverage areas and message categories which have been excluded by the operator from reception and/or display should be readily available.
4 RECEIVERS
4.1 The equipment should contain one receiver operating on the frequency prescribed by the Radio Regulations for the International NAVTEX System. The equipment should contain a second receiver capable of working at the same time as the first one on at least two other frequencies recognized for the transmission of NAVTEX information. The first receiver should have priority in the display or printing of received information. Printing or displaying of messages from one receiver should not prevent reception by the other receiver.
4.2 The receiver sensitivity should be such that for a source with an e.m.f. of 2V in series with a non-reactive impedance of 50 , the character error rate is below 4%.
5 DISPLAY DEVICE AND PRINTER
5.1 The display device and/or printer should be able to display a minimum of 32 characters per line.
1 Where there is no printer, the dedicated display device should be located in the position from which the ship is normally navigated.
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5.2 If a dedicated display device is used, the following requirements should be met:
.1 an indication of newly received unsuppressed messages should be immediately displayed until acknowledged or until 24 hours after receipt; and
.2 newly received unsuppressed messages should also be displayed.
5.3 The display device should be able to display at least 16 lines of message text.
5.4 The design and size of the display device should be such that displayed information is easily read under all conditions by observers at normal working distances and viewing angles.
5.5 If automatic line feed entails division of a word, this should be indicated in the displayed/printed text.
5.6 When displaying received messages on a display device, a clear indication of the end of a message should be given by automatically adding line feeds after the message or including some other form of delineation. The printer or printer output should automatically insert line feeds after completing print of the received message.
5.7 The equipment should display/print an asterisk if the character is received corrupted.
5.8 Where the printer is not integrated, it should be possible to select the following data to be output to a printer:
.1 all messages as they are received;
.2 all messages stored in the message memory;
.3 all messages received on specified frequencies, from specified locations or having specified message designators;
.4 all messages currently displayed; and
.5 individual messages selected from those appearing on the display.
6 STORAGE
6.1 Non-volatile message memory
6.1.1 For each receiver fitted it should be possible to record at least 200 messages of average length 500 characters (printable and non-printable) in non-volatile message memory. It should not be possible for the user to erase messages from memory. When the memory is full, the oldest messages should be overwritten by new messages.
6.1.2 The user should be able to tag individual messages for permanent retention. These messages may occupy up to 25% of the available memory and should not be overwritten by new messages. When no longer required, the user should be able to remove the tag on these messages which may then be overwritten in normal course.
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6.2 Message identifications
6.2.1 The equipment should be capable of internally storing at least 200 message identifications for each receiver provided.
6.2.2 After between 60 h and 72 h, a message identification should automatically be erased from the store. If the number of received message identifications exceeds the capacity of the store, the oldest message identification should be erased.
6.2.3 Only message identifications which have been satisfactorily received should be stored; a message is satisfactorily received if the error rate is below 4%.
6.3 Programmable control memories
6.3.1 Information for location (B1)2 and message (B2)2 designators in programmable memories should not be erased by interruptions in the power supply of less than 6 h.
7 ALARMS
7.1 The receipt of search and rescue information (B2 = D) should give an alarm at the position from which the ship is normally navigated. It should only be possible to reset this alarm manually.
8 TEST FACILITIES
8.1 The equipment should be provided with a facility to test that the radio receiver, the display device/printer and non-volatile message memory are functioning correctly.
9 INTERFACES
9.1 The equipment should include at least one interface for the transfer of received data to other navigation or communication equipment.
9.2 All interfaces provided for communication with other navigation or communication equipment should comply with the relevant international standards.3
9.3 If there is no integrated printer, the equipment should include a standard printer interface.
2 Refer to Recommendation ITU-R M.540. 3 Refer to publication IEC 61162.
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Annex 4
EXTRACT FROM IMO RESOLUTION A.801(19), ANNEX 4
Criteria for use when providing a NAVTEX service
1 There are two basic areas which must be defined when establishing a NAVTEX service. They are:
Coverage area: An area defined by an arc of a circle having a radius from the transmitter calculated according to the method and criteria given in this annex.
Service area: A unique and precisely defined sea area, wholly contained within the coverage area, for which maritime safety information is provided from a particular NAVTEX transmitter. It is normally defined by a line that takes full account of local propagation conditions and the character and volume of information and maritime traffic patterns in the region.
2 Governments desiring to provide a NAVTEX service should use the following criteria for calculating the coverage area of the NAVTEX transmitter they intend to install, in order to:
 determine the most appropriate location for NAVTEX stations having regard to existing or planned stations;  avoid interference with existing or planned NAVTEX stations;  establish a service area for promulgation to seafarers.
3 The ground-wave coverage may be determined for each coast station by reference to Recommendation ITU-R PN.368-7 and ITU-R Report P.32216 for the performance of a system under the following conditions:
Frequency - 518 kHz Bandwidth - 500 Hz Propagation - ground-wave Time of day - 17 Season - 17 Transmitter power - 18 Antenna efficiency - 18 RF S/N in 500 Hz bandwidth - 8 db19 Percentage of time - 90
4 Full coverage of NAVTEX service area should be verified by field strength measurements.
16 Recommendations ITU-R PN.368-7 and ITU-R Report P.322 are superseded by: Recommendation ITU-R P.368-9 and Recommendation ITU-R P.372-10 respectively. 17 Administrations should determine time periods in accordance with NAVTEX time transmission table (NAVTEX Manual, Table 2) and seasons appropriate to their geographic area based on prevailing noise level. 18 The range of a NAVTEX transmitter depends on the transmitter power and local propagation conditions. The actual range achieved should be adjusted to the minimum required for adequate reception in the NAVTEX area served, taking into account the needs of ships approaching from other areas. Experience has indicated that the required range of 250 to 400 nautical miles can generally be attained by transmitter power in the range between 100 and 1,000 W during daylight with a 60% reduction at night. 19 Bit error rate 1 x 10-2.
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Annex 5
PROCEDURE FOR AMENDING THE NAVTEX MANUAL
1 Proposals for amendments to the NAVTEX Manual shall be examined in substance by the Sub-Committee on Radiocommunications and Search and Rescue (COMSAR), followed by approval of the Maritime Safety Committee.
2 Amendments to the Manual should normally be approved at intervals of approximately two years or at such longer periods as may be determined by the Maritime Safety Committee. Amendments approved by the Maritime Safety Committee will be notified to all concerned, will provide at least 12 months' notification and will come into force on 1 January of the following year.
3 The agreement of the International Hydrographic Organization and World Meteorological Organization, and the active participation of other bodies, shall be sought according to the nature of the proposed amendments.
___________
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