Clasification Society Rulefinder 2018 - Version 9.30
Statutory Documents - IMO Publications and Documents - Circulars - Maritime Safety Committee - MSC.1/Circular.1403 – Revised NAVTEX Manual – (23 May 2011) - Annex - 5 NAVTEX Message Technical Characters - 5.3 B2 – Subject Indicator Character

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 .

  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.

Parent topic: 5 NAVTEX Message Technical Characters
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