Digital Selective Calling (DSC) – What you need to know

What is DSC?
DSC or Digital Selective Calling is a standard method of transmitting messages via VHF (ä vein via MF and VF). It is primarily used to send distress calls to both other ships and land systems.

DSC allows you to "dial" or receive a call directly, instead of to have to listen to a speaker. DSC can alsoå support emergency, security and routine calls in addition to emergency calls.

When an emergency call is made, it provides certain information automatically when connected to other units, which can significantly improve response and rescue times. The vessel's identity is sent together with the MMSI. If the VHF / DSC is connected to a GPS, it can also send the current position of the vessel instead of having to enter it manually. Since DSC allows you to contact the Coast Guard directly, this also saves vital time in an emergency.

If a distress call is sent from a ship via DSC, all nearby shore stations and other DSC-equipped ships will receive this call, and it will alarm. This call alert is repeated until it is acknowledged, to ensure that it is not missed or forgotten.

In addition to this, på due to its narrow bandwidth and no "squelch" på the receiver, DSC has a greater range than voice calls on; about 15-25%, which means that it is much more likely that when anyone else.

DSC has its own unique channel (channel 70), which all DSC-compatible radios will automatically monitor. It is worth noting that if a call is made between 2 ships, while the first call is unique, the conversation after that will work on; a working channel that can be picked up by any VHF equipment within range.

What is MMSI (Maritime Mobile Service Identity)?
An MMSI ä is a unique 9-digit number used to identify ships, coast stations, SAR aircraft etc... essentially like registration numbers for cars. This number is assigned to a DSC radio or an AIS. Identification MMSI is an individual call number for the vessel, which means that a shore station or another vessel can call your vessel using the MMSI.

There are 6 categories for MMSI;

• Ship station
• Group ship station
• Coast station
• Group coast station
• SAR aircraft
• Navigation aids and crafts

For bringing; an MMSI requires a license from Post and Telestyrelsen. It is an offense to use or install a radio on board without a licence. Once a license has been obtained, an MMSI is assigned to the vessel, and all radio equipment must operate under this MMSI. This is for security and traffic management purposes.