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What is DSC and MMSI and why do I care? PDF Print E-mail
Written by Carlos   
Wednesday, 14 April 2010 08:08

The terms "DSC" and "MMSI" are often seen in specifications and advertising for marine radios.  But what do they mean, and why would I care?



DSC stands for Digital Selective Calling.  It requires that you get an MMSI (Maritime Mobile Service Identity) number and program it into your radio.  DSC uses the MMSI to identify every radio as unique.  This enables you to make a direct "call" to another radio, or a group of radios.  Instead of keying the microphone and hailing your friend, you can enter his MMSI in your radio and make a direct DSC call to him, which tunes his radio to your channel automatically and begins a conversation.  The same is true for group hailing, such as a fishing group, or a distress call.  At the same time, your radio is identified to the person(s) being called.  This saves precious time in an emergency situation.  Emergency responders will have instant access to your boat's details as well as your information and emergency contacts.

In addition, if your radio is connected to a GPS input, it will send your exact position.  This is practical when you simply want to have a friend meet you at a certain spot, but more importantly, sends your exact location if you make a distress call.  DSC also has more range than a voice conversation, so the Coast Guard and other vessels are more likely to catch your mayday call and position if you use DSC.  If you connect the radio's output to a plotter that has a proper input, your friend's position can then be shown on your plotter.  The same is true if a DSC mayday call is sent in your area.

All radios manufactured in the last ten years are required to support DSC.  However they leave the rest up to you.  You must request an MMSI number, and you must program it into the radio.  You also need to connect a GPS to your radio.  There are two ways to get an MMSI; via Boat US, or via the FCC.  Boat US numbers are good only within the US, and are free.  FCC numbers are for international travel, and come with a ship's station license for your radio, which costs $200.  A station license is only required for commercial use or for international travel.

Click here to get a new MMSI or modify your existing one with new details.

In an upcoming article, I'll discuss how to interconnect your radio with a GPS and a plotter.


Last Updated on Friday, 04 June 2010 13:52
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