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Digital Selective Calling
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DIGITAL SELECTIVE CALLING CLASSES

The DSC protocol is defined by ITU-R Recommendation M.493 (series), available from the International Telecommunications Union in Geneva, Switzerland DSC operation is defined by ITU-R Recommendation M.541 (series).

Click the Classes hyperlinks in blue to go to that Class.
A B D E
Class A: Return to the top of the page
  • Distress call
  • All-ships call
  • Individual station call
  • Semi-automatic/automatic service call
  • Use of distress, urgency, safety and routine priorities
  • Nature of distress
  • Distress coordinates
  • Time for last (distress) position update
  • Type of subsequent communications
  • Distress relay
  • Distress acknowledgment
  • Test call (for MF/HF only)
  • Radio frequency or channel
  • Display
  • Receive geographical area calls
  • Alarm
  • Optional means for canceling a distress alert
  • Polling
  • Position acknowledgement
  • Test call
  • Test acknowledgement
  • Data
  • Data acknowledgement
All DSC options provided. DSC capability on vessels required to carry a VHF or MF/HF DSC radio under SOLAS or US regulations. Class A includes polling and vessel tracking, data, and numerous other functions in addition to voice.
Class B: Return to the top of the page

DSC capability on vessels required to carry a VHF DSC radio under SOLAS or US regulations, though most such radios in fact meet Class A. Class B required capabilities include:

  • Distress call
  • All-ships call
  • Individual station call
  • Semi-automatic/automatic service call
  • Use of distress, urgency, safety and routine priorities
  • Nature of distress
  • Distress coordinates
  • Time for last (distress) position update
  • Type of subsequent communications
  • Distress relay
  • Distress acknowledgment
  • Test call (for MF/HF only)
  • Radio frequency or channel
  • Display
  • Receive geographical area calls
  • Alarm
  • Optional means for canceling a distress alert
Class D: Return to the top of the page

DSC capability for VHF marine radios used by recreational vessels and other vessels not required to carry a VHF DSC radio. Class D required capabilities include:

  • Distress call
  • All-ships call
  • Individual station call
  • Use of distress, urgency, safety and routine priorities
  • Nature of distress
  • Distress coordinates
  • Time for last (distress) position update
  • Type of subsequent communications
  • Radio VHF channel
  • Display
  • Receive distress relay and distress acknowledgment calls
  • Alarm
  • Distress acknowledgement (receive)
  • Geographical area call (receive)
  • Test call
  • Test acknowledgement
Class E: Return to the top of the page

DSC capability for HF marine radios used by recreational vessels and other vessels not required to carry an HF DSC radio. Class E required capabilities include:

  • Distress call
  • Individual station call
  • Use of distress, urgency, safety and routine priorities
  • Nature of distress
  • Distress coordinates
  • Time for last (distress) position update
  • Type of subsequent communications
  • Radio channel or frequency
  • Display
  • Receive distress relay and distress acknowledgment calls
  • Test call
  • Test acknowledgement