DSC

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DSC
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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..

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• Cellphone

• VHF/MF/HF

Voice
Radio Telephony
Text Message
DSC or Digital Selective Calling
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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
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Acknowledge received
Waiting for acknowledgement
Press SEND to acknowledge
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The Individual Elements of the DSC Call
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• 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

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

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• Category The type of call

• Self identification the ships own MMSI

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• Message 1 Nature of distress

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• Message 2 describes the distress position

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• Message 3 Time of position in UTC

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• 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.

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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

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MMSI
Single ship
MMSI 257 123450
MID

6 DIGITS
Group of Ships
MMSI 0257 12340
MID
0

5 DIGITS

Coast Radio Station
MMSI 00 257 1230
00

4 DIGITS

MID
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Thank you