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posted Jan 14, 2013, 4:47 PM by Unknown user   [ updated Jan 14, 2013, 4:54 PM ]
Do you have your MMSI?
This is one of the most important things you can do as a responsible boater for you and your occupant's safety.
Did you know most radios have a menu built in?  
Some access the menu by holding down one button or they may have a dedicated "menu" button.
For example, on a NAVMAN radio, hold down the CALL button to access a menu area. Inside this menu area is an ability to add your DSC number.
MMSI and DSC refer to the same thing, a designated number specifically tied to your boat.
While MMSI is geared toward rescue and emergency operations, DSC is a feature geared toward making "ship to ship" calls over a VHF radio.
How do you obtain this number?
Obtain a free MMSI for your boat here:
When you begin this process, you'll notice the site asks a lot of question about you, your family, and your boat. 
For emergency situations, it is best to fill out the forms as accurate and detailed as possible.
Pay close attention to the last box - remarks.  It would be beneficial to let the Coast Guard know how to quickly identify your boat.
What color is it?  What color is the canvas?  For example, I left a note there may be a newborn baby onboard.
Here is why.... 
When the DISTRESS button is pushed on a radio with an MMSI entered, the Coast Guard is notified of that number.
They are able to look up the information you have entered - to include number of potential people onboard, children, color and type of boat, etc...
Combine that with the next important step, a radio connected to a GPS feed, they will also get your coordinates.
A child could press the DISTRESS button and transmit just about everything the Coast Guard would need to locate and identify your boat.
The only missing piece of information would be the nature of the distress.
The MMSI also opens up the Digital Selective Calling feature on your radio as well....
The newest radios are required by law to provide an operating mode called Digital Selective Calling, DSC.
This new technique is a part of the Global Marine Distress Signaling System, GMDSS (a part of the international SOLAS treaty).

DSC capability is available in two forms;

Category A DSC and Category D DSC.

Both category A and D radios can send and receive digitally encoded distress calls on channel 70, which is reserved exclusively for digital communications. 
Category A radios have two separate receivers, with one constantly tuned to channel 70.
Category A radios are therefore more flexible and capable of delivering advanced communication capabilities.
With the press of a button, all DSC equipped VHF radios can send a distress call in digital form on channel 70.
The call, sent in much less than one second, includes your unique identification number (MMSI) and if the radio is connected to a GPS or Loran C, the precise location of your boat.
The distress call will continue to be sent until it is answered by another station.

The station hearing the call will likely call your radio on channel 16 or, in the case of the Coast Guard on 22A and begin the process of bringing you the help you need.
Having a highly automatic way of making your need for assistance known has obvious advantages.
Because class A VHF/DSC radios have added capability they are more costly than the Class D versions.
The separate, dedicated channel 70 receiver in the Class A radio ensures that it is always ready to receive and respond to both emergency and routine DSC calls, even when it is monitoring any of the normal working channels or weather channels.
In addition to the second receiver, most Class A DSC radios are equipped with extensive calling number memory and caller I.D. systems and telephone like keypads that greatly simplify entering the MMSIs and names of frequently called vessels and shore stations.

A Class A VHF/DSC radio makes use of the "Selective" in DSC by calling other DSC radios by their unique MMSI number.
These radios usually provide an electronic notepad that stores names and MMSIs for other boats or shore stations.

Another station can be called by selecting the name or number from the stored list, choosing the channel number on which you wish to communicate and pressing a button.
A digital call containing the MMSI being called, the MMSI of your radio and the channel number on which you wish to communicate is sent on channel 70.
The called radio recognizes its MMSI and alerts its operator to the incoming call by emitting a ringing tone.
The radio automatically switches to the communication channel chosen by the caller, allowing voice communication to proceed with no further action required of either party.
If your MMSI is stored in the called radio's memory the operator will be informed of your identity as in a land-line caller I.D. system.
Depending on the particular capability of the radio, it may also provide call waiting alert and log calls received when the radio was unattended.

Overall, a Class A DSC radio performs much like a cellular telephone.
With widespread use, the VHF/DSC system will gradually eliminate the need to monitor the often busy and noisy channel 16 for incoming calls or, as required by regulation, for distress calls.