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22 GPSMAP 188/188C Sounder Owner’s Manual
BASIC OPERATION > DSC
DSC
The DSC tab on Main Menu controls and sets up the Digital
Selective Calling (DSC) features on the GPSMAP 188/188C
Sounder.
DSC uses marine VHF radio and Global Positioning System (GPS)
technologies to transmit and receive location information. The
chartplotter repeats the call properties received from the VHF radio
on the chartplotter. The GPSMAP 188/188C Sounder requires input
from a DSC enabled VHF radio to display position, and sound/
display alerts from a Distress Call or Position Report. Conversely,
the VHF radio requires input from a GPS to transmit position
coordinates for a Distress Call or Position Report. For connection
information, refer to “Connecting the Power/Data Cable” on
page 98.
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 rescuers receives the DSC signal, an alarm
sounds and they immediately receive the location of the caller.
The rescuer can choose to navigate 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.
A non-emergency DSC Position Report allows mariners to
exchange and display the positions of one another. When a DSC
position is received, the mariner can choose to create a waypoint or
to show the received location on an electronic map.
Anytime a vessel receives a DSC call, they can store and quickly
navigate to that location using a Go To. To use DSC, users must
first register their VHF radios with the FCC and receive a Maritime
Mobile Service Identity (MMSI) number. Garmin does not provide
MMSI numbers.
For more information about Digital Selective Calling and Maritime
Mobile Service Identity (MMSI) numbers, refer to page 103 in the
“Appendix.”
Understanding Distress Calls
When the GPSMAP 188/188C Sounder receives a Distress Call
from a connected DSC-enabled VHF radio, an alert message and
notification page appear, and an alarm tone sounds. Distress Calls
are shown in the DSC Call List and Log with a checkered symbol.