DSC

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..

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

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

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

The Individual Elements of the DSC Call

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:

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

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

Message 1: Nature of distress:

Message 2: describes the distress position

Message 3: Time of position in UTC

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.

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

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

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