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DSC MMSI information

2500 Views 0 Replies 1 Participant Last post by  Dave B.
Just some info to pass on for anyone interested in how the VHF DSC MMSI is used and it's purpose. It's actually pretty cool, dont be fooled into believing this is rocket science, it's fairly straight forward.

About MMSI Registration for VHF Radios with DSC

Your VHF radio is the single most important piece of safety equipment you can have on board your vessel. By using a VHF radio with Digital Select Calling (DSC) capability, you increase your safety dramatically by taking advantage of enhanced communications options. These options link you to other vessels and rescue facilities, providing a strong, modern safety net.

The Role of BoatU.S.:BoatU.S. has been authorized by both the Federal Communications Commission and the U.S. Coast Guard to assign MMSI numbers to vessels with DSC capable radios that are not required by law to carry a radio, and do not make international voyages or communications. BoatU.S. is responsible for relaying the MMSI registration information to the U.S. Coast Guard for search and rescue purposes.

The BoatU.S. MMSI Service is limited by agreement to registering recreational vessels only - those not otherwise required to have an FCC ship station license (also called "voluntarily equipped".) Vessels required to carry a radio on board are "compulsory equipped" and therefore FCC licensed and should obtain an MMSI from the FCC.

GMDSS (Global Maritime Distress & Safety System): Is a major overhaul of the international system governing safety radio equipment on commercial ships. While recreational boaters are not required to participate in GMDSS, for safety reasons it makes sense to take advantage of the improved telecommunications, and rapid distress monitoring and reporting for mariners.

For more information on GMDSS visit:

DSC (Digital Selective Calling): Marine radios equipped with DSC serve as one facet of the GMDSS. A DSC equipped radio has all the features of your current VHF radio, and more. DSC technology makes a VHF radio work more like a telephone. It allows boaters to send a digital call directly to another DSC-equipped vessel or shore station, much like a person-to-person telephone call.

Channel 70 has been set aside as the VHF/DSC digital call channel. Once the DSC call has been confirmed, both parties are automatically switched to a working voice channel.

In an emergency, one push of a button and your DSC radio will send an automated digital distress alert consisting of your identification (MMSI) number, and position (if your radio is linked to a GPS receiver) to other DSC-equipped vessels and rescue facilities.

MMSI (Maritime Mobile Service Identity): Obtaining an MMSI is necessary in order to use the DSC functions of the radio. The MMSI number serves as both a nine digit “telephone number” and as a unique identification number for the U.S. Coast Guard to use in order to locate and identify you in an emergency.

During normal communications, vessels with DSC capable radios may call each other over channel 70 using the MMSI as a "telephone number". The signal will only be received by those vessels with the MMSI numbers that were called.

During an emergency, the boater may push a button to automatically transmit a May Day call which would include their MMSI number (and location if the radio is linked to a GPS receiver) to every DSC radio within range. When the U.S. Coast Guard receives the unique MMSI number, it will use the information on file (emergency contact number, type of vessel, etc.) to mount a more effective rescue effort.

For more information regarding MMSIs, visit:

Depending on the make and model of your DSC radio, it may limit the number of times you can try to program your MMSI number into the radio. If you try to enter an MMSI number too many times, the radio may lock out future attempts, forcing you to send the unit to the manufacturer to re-program the MMSI number. Typically the radios offer you two (2) opportunities to program your MMSI number, but be sure to read the owner’s manual regarding your specific model. Please be careful when initially programming your newly assigned MMSI number.
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