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 BoatUS

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

The BoatUS 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)

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 built into your modern marine radio allows the radio to perform a number of enhanced functions. It permits direct contact with another specific DSC capable unit, polling other DSC units for their locations, and various other special features. The most significant function is its ability to transmit an automated distress call.

In an emergency, one push of the distress button transmits the distress signal conatining your MMSI # and, assuming a built-in or external GPS link, your Lat/Lon information to USCG and all other DSC capable receivers within your broadcast range. It continues to transmit until acknowledged, even if you can't be attending it.

Channel 70 has been designated as the VHF/DSC digital call channel, but you do not have to select Ch 70. That happens automatically whenever a DSC function is activated. Once the DSC call has been confirmed by the receiving unit, both parties are automatically switched to the pre-selected working channel for voice transmission. . Once the DSC call has been confirmed, both parties are automatically switched to a working voice channel.

MMSI (Maritime Mobile Service Identity)

You must obtain (do not create your own) an MMSI and enter it into your DSC capable marine radio in order to enable the unit's DSC functions. The MMSI number serves as both a nine digit “telephone number” and as a unique identification number that the U.S. Coast Guard will use to identify you in an emergency. This is especially important if communications were to break down.

During normal communications, vessels with DSC capable radios may call each other digitally by using the MMSI as a "telephone number". The signal will only be received by those vessels with the MMSI numbers that were called, after which everyone on the call is switched automatically to a pre-selected working channel for normal voice transmission.

During an emergency, the boater may push a button to automatically transmit a distress 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 alert, the unique MMSI number will be used to access the related information on file (emergency contact number, type of vessel, etc.) to help them mount a more efficient rescue effort.

For more information regarding MMSIs, visit:
http://www.imo.org/blast/mainframe.asp?topic_id=69&doc_id=581 and/or MMSI FAQs.

Important Notice

All DSC capable radios limit the number of times you can program an MMSI into them. Older units generally allow an MMSI to be logged in TWICE, but the newer models are mostly limited to ONE MMSI login attempt only. If you exceed the MMSI entry attempt limit, the radio will lock out any future attempts, forcing you to send the unit to the manufacturer for reprogramming. Be sure to read the owner’s manual regarding that restriction, and please be careful when initially entering your newly assigned MMSI number into the unit.