MMSI FAQ's

MMSI, the Maritime Mobile Service Identity, at BoatUS, has expanded our Frequently Asked Questions (FAQ's) to answer your questions regarding online difficulties, VHF radio questions and general questions about MMSI and how it pertains to your boat.

Questions are grouped by category, so please click on the appropriate question to view the answer. For additional information please contact us at MMSI@BoatUS.com

Back to MMSI FAQ's Homepage

What is MMSI?

 

What does MMSI stand for?

Maritime Mobile Service Identity

Return to Top

What is MMSI?

A unique 9 digit number that is assigned to a DSC radio station

Return to Top

What does DSC stand for?

Digital Selective Calling — which is a new radio technology allowing enhanced distress radio messages to be sent digitally.

Return to Top

Is my radio capable of sending a DSC message?

Maybe. Radios with DSC capability have been on the U.S. market for nearly a decade. Since 1999, the FCC (Federal Communications Commission) has required new fixed mount models introduced in the U.S. to be equipped with the DSC feature. Minimally, DSC radios are equipped with single-button emergency transmission capability. The earlier SC-101 class radios have been largely replaced by superior Class D DSC radios.

Return to Top

What does MMSI do?

Similar to a cell phone number, it is your unique calling number for DSC VHF. It also registers the boat information in the U.S. Coast Guard's national distress database for use in emergency situations. Your MMSI number is transmitted with a DSC call, like “caller ID.”  

Return to Top

What are some advantages of a DSC equipped radio?

DSC radios have a one-button emergency transmit button that sends the vessel's unique MMSI number. In addition, if the DSC equipped radio is linked to a GPS or Loran unit, the distress call will include the vessel's position. Should the skipper become incapacitated, the radio will continue sending the mayday. In addition, a DSC equipped vessel with an MMSI number can make a "private" hailing call to another DSC-equipped vessel. Only the vessel being called will receive the hail.

Return to Top

Does the U.S. Coast Guard monitor DSC maydays?

Not completely nationwide yet, until Rescue 21 is declared operational throughout the continental U.S. by 2012 and, later (2011-17)for Alaska, Puerto Rico and Guam. However, Rescue 21 is operational on many coasts, for example, from New York to Florida and around the Gulf Coast to Houston as well as the Pacific Northwest. Commercial ships are required to monitor the DSC-reserved Channel 70 for distress calls and have relayed maydays to the Coast Guard. In an emergency, Channel 16 should be used first. (See implementation map at www.BoatUS.com/mmsi)

Return to Top

I am required to have an FCC License.  How do I obtain one?

Go to: http://www.fcc.gov/Forms/Form605/605.html and be sure to complete Schedule B to get an MMSI number. (An MMSI no longer comes automatically with the FCC license — it has to be requested.)

Return to Top

Does the Coast Guard plan to cease monitoring Channel 16 once GMDSS is operational
in the U.S. after 2005-2006?

No. The Coast Guard has no plans to stop monitoring Channel 16 at any time in the foreseeable future.

Return to Top

Is there a channel reserved for DSC?

Yes, channel 70 is to be used exclusively for DSC.

Return to Top

As a recreational boater, do I have to maintain a watch on Channel 70?

No.

Return to Top

What is "private calling" as related to DSC?

It is in effect "private hailing" of another vessel whose MMSI number is known to you. Once contact is established between the vessels, they are automatically switched to the preselected "working channel", and the "privacy" ends at that point, meaning that the transmission (conversation) can be heard by any other vessel monitoring that channel.

Return to Top

I thought MMSI numbers were supposed to begin with a "366". I received mine and it has a different prefix.

The first digit or two identifies one of the four kinds of Maritime Mobile Service Identities:

  • Ship station identities
  •  Group ship station identities
  • Coast station identities
  • Group coast station identities

For a complete breakdown and explanation of the 3-digit prefixes, visit the following USCG web site: http://www.navcen.uscg.gov/marcomms/gmdss/mmsi.htm

Return to Top