Uscg Response Policy
USCG Response Policy for MF/HF Digital Selective Calling (Acrobat PDF)(22 Oct 99)
Distress Relays
The single largest operational problem of the U.S. Coast Guard concerning DSC is responding to the large number of MF/HF DSC distress relays being sent by ships. ITU regulations require each relay to be individually acknowledged. The Coast Guard treats each distress alert relay as if it were a separate distress. Worse, certain radios insert the identity of a ship sending a relay, rather than a ship sending a distress, into the menu of a relay message, and ship operators are transmitting this relay falsely identifying the ship in distress to Coast Guard rescue coordination centers. The USCG requests that vessels not relay any DSC distress message which has already been acknowledged. If you do relay a distress message, make sure the identity of the vessel in distress is correct, and send the relay to a USCG radio station using an identity such as 003669999, rather than sending it to all ships.
Imo Flowcharts
The International Maritime Organization Communications and Search & Rescue Subcommittee released COMSAR Circular 21 of 25 January 2000, which includes simplified flowcharts on the actions a person on a ship should perform on receipt of a distress alert using DSC-equipped radios. Documents are in Acrobat PDF format.
Actions on receipt of a VHF DSC distress alert
Actions on receipt of a MF/VHF DSC distress alert
Actions on receipt of an HF DSC distress alert
Complete COMSAR Circular
Dsc Forum
As a result of delays and questions associated with the implementation of DSC, the US Coast Guard has agreed to host a web-based Internet discussion forum on DSC technical and operational issues. We are encouraging the technical experts around the world who helped design and who use DSC to participate in this forum, and we encourage those who have used the system to also participate. The forum is "threaded", which means that comments from different individuals on a given subject are grouped together, with replies connected to the message being replied to. The purpose of establishing this forum is to help identify and resolve problems associated with DSC discovered during its implementation.
By participating in the Forum, you agree to act in a courteous and professional manner. Do not post offensive or inappropriate material, or engage in personal attacks on other participants.
Vessel tracking and position fixing
The new Universal Shipborne Automatic Identification System will be backwards compatible to DSC, allowing countries having GMDSS A1 areas to establish AIS operating frequencies, and additionally identify and track vessels equipped with AIS.
Classes of Digital Selective Calling
The DSC protocol is defined by ITU-R (CCIR) Recommendation M.493-9, adopted and now available from the International Telecommunications Union in Geneva, Switzerland. DSC operation is defined by ITU-R Recommendation M.541-8.
Class A:
All DSC options provided. Required on MF/HF radios used by SOLAS-regulated ships. Class A includes polling and vessel tracking, data and telex connection in addition to voice, and optional means for canceling a distress alert.
Class B:
Required on VHF and MF radios used by SOLAS-regulated ships. 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
Optional expansion to DSC protocol..
USCG Notice to Mariners MF/HF DSC Guidelines (pdf)
DSC Operational Procedures for Ships
How Digital Selective Calling Works
Maritime Mobile Service Identities Explained
Why Coast Guard Supports DSC on Marine Radios
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