Raymarine RAY91 - Introduction to DSC

7.1DigitalSelectiveCalling(DSC)
TraditionalVHFradiosystemsrequireuserstolistenuntilsomeonespeaks,andthendetermine
whetherthecallisforthem.DSCensuresthatcallsarereceivedbyalertingorannouncingthe
intendedrecipient(s)firstsotheyarereadytolistentothesubsequentmessageontherelevant
channel.
DSCispartoftheGlobalMaritimeDistressandSafetySystem(GMDSS),amaritimecommunications
systemforemergencyanddistressmessagesandalltypesofroutinecommunicationssuchas
ship-to-shiporship-to-shore.
DSCisadigitalsignallingsystem,whichoperatesonVHFchannel70.DSCcallsincludeotherdata
suchasyourvessel’sidentificationnumber,purposeofthecall,yourpositionandthechannel
youwanttospeakon.
DSCcallscanbedividedinto4categoriesandareprioritizedasshownbelow:
1.Distress
2.Urgency
3.Safety
4.Routine
Distress
ADistresscallshouldonlybeusedwhenthereisimminentdangertoavehicleorpersonthat
requiresimmediateassistance.
Whenmakingadistresscallthefollowinginformationistransmittedtoallstationswithinrange:
•VesselMMSInumber.
•Vesselposition(mustbeinputmanuallyifnopositiondataisavailable).
•Localtime(mustbeinputmanuallyifnopositiondataisavailable).
•Natureofthedistress(whendesignated).
•Transmissionfrequency.
Thecallisautomaticallyrepeatedatapproximately4minuteintervalsuntilitisacknowledgedeither
byacoastradiostation(CRS)oravesselwithinradiorange.Distresscallsmustbefollowedbya
MAYDAYcallonprioritychannel16.
Urgency
Anurgencycallshouldbeusedwhenthereisdangertoavehicleorpersonthatdoesnotrequire
immediateassistance.
Whenmakinganurgencycallthefollowinginformationistransmittedtoallstationswithinrange:
•VesselMMSInumber.
•Vesselposition(mustbeinputmanuallyifnopositiondataisavailable).
•Localtime(mustbeinputmanuallyifnopositiondataisavailable).
•Transmissionfrequency.
OnceanurgencycallissentitmustbefollowedwithaPANPANvoicemessageonchannel16and
includethenecessarydetails.
Safety
Asafetycallshouldbeusedwhenthereisanimportantnavigationalwarningormeteorological
forecast/broadcast.Safetyalertscanalsousedforcommunicationsduringsearchandrescue
operations.
Whenmakingasafetycallthefollowinginformationistransmittedtoallstationswithinrange:
•VesselMMSInumber.
•Vesselposition(mustbeinputmanuallyifnopositiondataisavailable).
•Localtime(mustbeinputmanuallyifnopositiondataisavailable).
•Transmissionfrequency.
OnceasafetycallissentitmustbefollowedwithaSECURITEvoicemessageonchannel16and
includethenecessarydetails.
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