MMSI - Maritime Mobile Service Identity
Maritime Mobile Service Identity, or MMSI is a key component for ensuring your safety while boating. Additionally, a MMSI number allows you to use Digital Selective Calling(DSC).
Why MMSI?
Any boater could face a sudden situation caused by a fire, collision, capsize, sinking boat or medical emergency. With a registered VHF DSC-compatible radio using your unique MMSI number, your emergency situation is immediately transmitted with critical data to the US Coast Guard and other vessels in your vicinity. Press the “Red” button on the radio and the communications begins.
What is a MMSI?
The Maritime Mobile Service Identity (MMSI) is a unique nine-digit number that identifies transmitted signals within the GMDSS system. It functions like a telephone number for the devices on your boat. The MMSI is assigned to a vessel, and the same MMSI is programmed into all shipboard equipment that transmits and receives digital signals, including VHF radio, medium and high frequency radios, AIS (Automatic Identification System), and INMARSAT satellite terminals. Learn more at the US Coast Guard Maritime Telecommunications website.
How to Update or Change an MMSI Registration?
If your MMSI registration information or contact information changes for any reason, you must update your registration. If you sell your DSC-equipped radio or AIS or the boat these devices are mounted on, you must cancel your MMSI registration and should inform the new owner of the need to reregister the MMSI. This is necessary to ensure that the US Coast Guard is able to contact the right persons if a distress situation were ever to occur. These registration changes can be accomplished by contacting the organization or agency which originally registered your MMSI.
How do I test it once I have my VHF radio configured with an MMSI?
Do NOT push the Red button to test your DSC/MMSI capability! The US Coast Guard has a specific procedure to perform a test DSC call. Here are those instructions.
Want to Learn More?
The America’s Boating Club offers an in-depth look at this system in their Marine Communications Systems course.
Want to learn more but not take a course? Then take the US Power Squadron Using VHF & VHF/DSC Marine Radio seminar.
Additional Information?
DSC technology allows boaters to send a digital call directly to other DSC-equipped vessels and shore stations, somewhat like a telephone call. Once the DSC call has been confirmed, both parties are automatically switched to a working voice channel. If properly installed, one push of a button in an emergency, and your DSC radio will send an automated digital distress alert consisting of your MMSI identification number (if it was input), and position (if it is interfaced with a GPS receiver) to other DSC-equipped vessels and search & rescue facilities. When they respond, they will automatically be connected to whatever channel your radio is set to. Of course, if you haven't interfaced it with your GPS and MMSI number, the only thing you will do is send an alarm.
One other nifty feature is that your MMSI number can act as a direct homing device to other similarly equipped radios that have your number. It’s a like a VHF phone number. You program in your friend’s MMSI and that radio is automatically and directly called without having to hail them on a public frequency. Of course, as soon as they answer, they will connect with you on the radio frequency you are standing by on, so keep in mind it’s still a public channel. Make sure you are standing by on a working channel not on a reserved frequency like channel 16.
Some Basic MMSI info from USCG: https://www.navcen.uscg.gov/maritime-mobile-service-identity
You can get your free MMSI at the USPS MMSI Registration page: https://www.usps.org/php/mmsi_new/
Or at the BoatUS MMSI page: https://www.boatus.com/products-and-services/membership/mmsi
Here are some fact filled article on benefits of registering and programming your MMSI: http://cruising.coastalboating.net/Seamanship/Radio/DSC.html
A good article summarizing Use of VHF & DSC radio: https://www.sailmagazine.com/cruising/are-you-using-your-vhf-radio-correctly
Good overall MMSI, DSC, GPS integration article: http://wow.uscgaux.info/content.php?unit=170&category=dsc-vhf-radio-rescue-21
Watch a few short videos describing the value of having a DSC VHF Radio and an MMSI: https://www.youtube.com/watch?v=AiXN8pNoA0I
https://www.youtube.com/watch?v=JZOXtB1SoIs