Digital Selective Calling (Dsc) - Garmin GPSMAP 496 - Aviation GPS Receiver Owner's Manual

Digital Selective Calling (DSC)

Digital Selective Calling (DSC) uses marine VHF radio and Global
Positioning System (GPS) technologies to transmit and receive
location information. DSC is used by mariners to assist them in two
major areas: distress calls and position reporting.
A non-emergency DSC position report allows mariners to exchange
and show the locations of one another. When you receive a DSC
location, you can create a waypoint or to show the received location
on an electronic map.
An emergency DSC distress call allows a vessel in trouble to
transmit a substantial amount of information in a single transmission
or "call," without the need for voice communication. When any
nearby rescuer receives the DSC signal, an alarm sounds and they
immediately receive the location of the caller.
The rescuer can choose to navigate (Go To) the caller's location to
assist or forward the call on to the Coast Guard. When the Coast
Guard receives the call, they can immediately access the caller's
information (such as who they are and the type of vessel) in their
database while they are in transit to the caller's location.
Any time a vessel receives a DSC call, they can store that location
and quickly navigate to that location using a Go To. This makes
DSC a time-saver, especially in an emergency situation. In order to
GPSMAP 496 Owner's Manual
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use DSC, users must first register their VHF radio with the FCC and
receive a Maritime Mobile Service Identity (MMSI) number.
What is a Maritime Mobile Service Identity
(MMSI)?
Maritime Mobile Service Identity (MMSI) basically allows a
VHF radio to act like a phone. The 9-digit MMSI number acts like
a phone number when used in a position report and as a unique
identifier when used in an emergency distress call. To obtain a
Maritime Mobile Service Identity (MMSI) number, users must
register their VHF radio with the International Telecommunications
Union or the local telecommunications authority/ship registry.
garmin does not supply this number!
For more information regarding MMSIs visit
How Can Garmin Help You with DSC?
To receive distress calls or position reports, you must have a DSC-
equipped chartplotter as well as a VHF radio with DSC support.
During normal, non-emergency Position Report communication,
Channel 70 (156.525 MHz) has been set aside as the VHF/DSC
digital call channel.
For a distress call, press the MayDay button on the VHF radio. The
call transmits on an emergency channel with the MMSI number
attached to the call, if the receiver has DSC support. Any DSC-
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