6 GPSMAP 496 Owner’s ManualAppendix > Digital Selective Calling (DSC)Digital Selective Calling (DSC)Digital Selective Calling (DSC) uses marine VHF radio and GlobalPositioning System (GPS) technologies to transmit and receivelocation information. DSC is used by mariners to assist them in twomajor areas: Distress Calls and Position Reporting.A non-emergency DSC Position Report allows mariners to exchangeand show the locations of one another. When you receive a DSClocation, you can create a waypoint or to show the received locationon an electronic map.An emergency DSC Distress Call allows a vessel in trouble totransmit a substantial amount of information in a single transmissionor “call,” without the need for voice communication. When anynearby rescuer receives the DSC signal, an alarm sounds and theyimmediately receive the location of the caller.The rescuer can choose to navigate (Go To) the caller’s location toassist or forward the call on to the Coast Guard. When the CoastGuard receives the call, they can immediately access the caller’sinformation (such as who they are and the type of vessel) in theirdatabase while they are in transit to the caller’s location.Any time a vessel receives a DSC call, they can store that locationand quickly navigate to that location using a Go To. This makesDSC a time-saver, especially in an emergency situation. In order touse DSC, users must first register their VHF radio with the FCC andreceive a Maritime Mobile Service Identity (MMSI) number.What is a Maritime Mobile Service Identity(MMSI)?Maritime Mobile Service Identity (MMSI) basically allows a VHFradio to act like a phone. The 9-digit MMSI number acts like aphone number when used in a Position Report and as a uniqueidentifier to the Coast Guard when used in an emergency DistressCall. To obtain a Maritime Mobile Service Identity (MMSI) number,users must register their VHF radio with the FCC (Form 605).garmin does not supply this number!For more information regarding MMSI’s visitwww.navcen.uscg.gov/marcomms/gmdss/mmsi.htm.
