Digital Selective Calling (DSC)

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Basic Description of DSC

DSC is basically a calling system. Each call consists of a "packet" of digitised information of one of four priorities: Distress, urgency, Safety or Routine. Messages can be routed to "All Stations", to an individual station or to a group of stations, using their Maritime Mobile Selective-call Identity code (MMSI). Distress messages are automatically broadcast to "All Stations". In addition to the MMSI of source and destination stations, information can be conveyed in the DSC message. For example, to aid the Rescue Services, the DSC Distress alert message is configured to contain the following: Ship's identity (the nine digit MMSI) Time Nature of distress (in the form of a standard code) Ship's position Where fitted, ship's officers should ensure they are fully conversant with the procedure for entering the necessary information into the DSC equipment. At sea, unless provided automatically from a navigation system, ship's position should be updated at least once during each watch period.