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Digtal Selective Calling

Digtal Selective Calling. Background. Under the “Old system, calling a ship has always involved using traffic list, or special calling channels. DSC is the new calling system which is a very essential part of the GMDSS.

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Digtal Selective Calling

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  1. Digtal Selective Calling

  2. Background Under the “Old system, calling a ship has always involved using traffic list, or special calling channels. DSC is the new calling system which is a very essential part of the GMDSS. DSC is being used as the PRIMARY alerting system on VHF, MF and the HF bands. The DSC control unit is able to monitor/keep watch on all DSC frequencies allocated for distress and safety purposes. In addition to the printout of message, an audible/visual alarm will be activated..

  3. Cellphone VHF/MF/HF Voice Radio Telephony Text Message DSC or Digital Selective Calling

  4. DSC • A system used for calling: • A particular ship • A particular coast station • A group of ships • All ships SHIP TO SHIP SHIP TO SHORE

  5. Acknowledge received Waiting for acknowledgement Press SEND to acknowledge

  6. The Individual Elements of the DSC Call

  7. Dot Pattern: A sequence of dots transmitted so that the scanning-receivers can be tuned, and stop scanning. • Phasing sequence: In-phasing signals making the receiver ready for reception of information from the DSC transmitter. • Format specifier: Call Specifications:

  8. Address: the MMSI (Maritime Mobile Service Identity) number of the ship or the coast station which is being called.

  9. DISTRESS URGENCY SAFETY IMPORTANT SHIP TRAFFIC ROUTINE • Category: The type of call • Self identification: the ship’s own MMSI

  10. Message 1: Nature of distress:

  11. Message 2: describes the distress position

  12. Message 3: Time of position in UTC

  13. Message 4: Kind of communication desired for the traffic which will follow. • End of sequence: acknowledgement or reply to a call • Error check character: transmitted as a control bit for the entire call.

  14. Selective calling numbers in the GMDSS • Consists of 9 digits • MID XXX XXX • MID (Maritime Identification Digit) allocations is found in the ITU “Manual for use by the Maritime Mobile and Maritime Mobile-Satellite Services”. • Example • Norwegian ships have MID or Maritime Identification Digit 257, 258 and 259 • Followed by 6 digits where the last digit is “0” • Used to identify the FLOAT FREE EPRIB and VHF/MF/HF DSC Equipment

  15. MMSI Single ship MMSI: 257 123450 + 6 DIGITS MID Group of Ships MMSI: 0257 12340 0 + + MID 5 DIGITS Coast Radio Station MMSI: 00 257 1230 MID 00 + 4 DIGITS +

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