1. DSC

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..

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

5. 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

7. Waiting for acknowledgement Press SEND to acknowledge
Acknowledge received
Waiting for acknowledgement
Press SEND to acknowledge

8. The Individual Elements of the DSC Call

9. 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:

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

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

12. Message 1: Nature of distress:

13. Message 2: describes the distress position

14. Message 3: Time of position in UTC

15. 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.

16. 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

17. MMSI Single ship MMSI: 257 123450 MID + 6 DIGITS Group of Ships+
MID
5 DIGITS +
Coast Radio Station
MMSI: 00 +
MID
4 DIGITS +

18. Thank you