DSC - Digital Selective Calling

SDC. Digital Selective Calling is used by marine or MF/HF VHF transceivers to digitally transmit a signal.

Its importance

Tasto Distress DSC
DSC Distress Button

The DSC is one of the most important elements of a GMDSS station, allowing the digital transmission of the station's identification data such as the MMSI code and coordinates, so that the receiving station immediately locates the boat and thus avoiding transmitting these data on the phone where they are often misinterpreted, especially if the communication takes place in a different language.

Particularly in emergency situations, the distress launch is almost completely automated and the user only has to press a red button to be located by the coastal station, so he will have to follow a subsequent communication in voice, but the coastal station already has some important data for the coordination of the rescue.

DSC distress operates on channel 70 (see VHF Marini Channels), so this channel cannot be used for voice or any other service.

The Regulations

See also marine VHF.


In pleasure craft it is only optional, but the user must have an SRC or LRC or ROC or GOC certificate and be in possession of the MMSI code.

Fishing vessels

SDC class "D" is mandatory on fishing vessels authorised to navigate beyond 3 miles. VHF-RTF/DSC-EPIRB Certificate or higher is required.

Charter Boats (Charter)

The DSC class "D" is mandatory on boats qualified to sail over 6 miles. An LRC or SRC certificate or higher is required. If the boat can carry more than 12 passengers, please refer to the GMDSS regulation.

Ships subject to GMDSS


Will the SDC become mandatory for pleasure craft too?

On February 4, 2017, Sole 24 Ore released a news report suggesting that the Government is considering the possibility of better regulating the use of the SDC in the recreational sector.

The Government may regularize the use of the distress button only and/or all the functions related to the DSC.

Regularisation of the distress button is desirable without the need for an examination. While for the use of the other DSC functionalities it seems necessary to us to have an examination, because the procedures are complex and the operator assumes various responsibilities.

In fact, the DSC represents a bit of the heart of GMDSS stations, where in ships there is a certified person to use this equipment, who sometimes has to be able to handle complex situations according to a specific protocol where errors are not tolerated (an example could be the mayday relay).

When the SDC became mandatory for fishing vessels in Italy, there were many difficulties that the authorities had to face in order to increase the number of users, which threatened to compromise the safety of much more important ships.

Among the related entries you will find the link to an article where we discuss this topic in more detail on MPS News.