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Maritime Mobile Service Identity (MMSI)

Maritime Mobile Service Identity (MMSI) is a unique 9 digit number that is assigned to a (Digital Selective Calling) DSC radio or an AIS unit. Similar to a cell phone number, your MMSI number is your unique calling number for DSC radios or an AIS unit.

The information provided when obtaining a MMSI number is transferred into the U.S. Coast Guard’s national distress database for use in emergency situations.

Understanding DSC and MMSI - PassageMaker

BoatUS has been authorized by both the Federal Communications Commission (FCC) 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.

BoatUS is responsible for relaying the MMSI registration information to the U.S. Coast Guard for search and rescue purposes.

MMSI numbers are free for BoatUS Members or $25 for non-Members

What is DSC and how do I know if my radio has it?

Digital Selective Calling (DSC) is a radio technology allowing enhanced distress radio messages to be sent digitally. Since 1999, the FCC (Federal Communications Commission) has required new fixed mount VHF radio sold in the U.S. to be equipped with the DSC feature.

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 operator 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 initial contact, but the subsequent conversation will take place on an open, “working” channel, which can be monitored by any VHF equipped vessel within your broadcast range.

Please refer to you radio’s owner’s manual or contact the radio manufacturer for additional information about you radio’s capabilities.

Maritime Mobile Service Identity (MMSI) from CT Corporation | Wolters Kluwer

What is the difference between obtaining an MMSI from the FCC and obtaining a number from BoatUS?

BoatUS MMSI numbers are for US registered or documented, recreational vessels under 65’ that are not visiting or communicating with foreign ports.

The registration data provided to BoatUS is only transferred into the U.S. Coast Guard Search & Rescue Database (MISLE). International search & rescue agencies do not have access to the registration data provided to BoatUS.

Registration data for FCC-assigned MMSI numbers go into the International Telecom Union (ITU) database that is accessible to international search & rescue agencies. In order to be accepted into the ITU database, any FCC assigned MMSI must end in zero.

This is why the BoatUS MMSI number cannot be re-used when later applying for an FCC MMSI number for international cruising.

An introduction to your new Member Portal, powered by MMSI | GAAR Blog | Greater Albuquerque Association of REALTORS®

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.

Registration Criteria

BoatUS has been authorized by both the Federal Communications Commission (FCC) and the U.S. Coast Guard to assign MMSI numbers only to vessels that meet the following criteria:

  • Used for recreation only
  • Not required by law to carry a radio
  • Not required by law to have a FCC Ship Station license
  • Vessel is under 65′ in length
  • Do not communicate with or visit foreign ports (i.e. Canada, Bahamas, Mexico, and the Caribbean)

If you do not meet these criteria, you are legally required to obtain a Ship Station License from the FCC. They will issue an MMSI number with a Ship Station License.

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