Raymarine Ray260 - DSC System Overview and Call Types

7.1DigitalSelectiveCalling(DSC)
TraditionalVHFradiosystemsrequireuserstolistenuntil
someonespeaks,andthendeterminewhetherthecallisfor
them.DSCensuresthatcallsarereceivedbyalertingor
announcingtheintendedrecipient(s)rstsotheyarereadyto
listentothesubsequentmessageontherelevantchannel.
DSCispartoftheGlobalMaritimeDistressandSafetySystem
(GMDSS),amaritimecommunicationssystemforemergency
anddistressmessagesandalltypesofroutinecommunications
suchasship-to-shiporship-to-shore.
DSCisadigitalsignallingsystem,whichoperatesonVHF
channel70.DSCcallsincludeotherdatasuchasyourvessel’s
identicationnumber,purposeofthecall,yourpositionandthe
channelyouwanttospeakon.
DSCcallscanbedividedinto4categoriesandareprioritized
asshownbelow:
1.Distress
2.Urgency
3.Safety
4.Routine
Distress
ADistresscallshouldonlybeusedwhenthereisimminent
dangertoavehicleorpersonthatrequiresimmediateassistance.
Whenmakingadistresscallthefollowinginformationis
transmittedtoallstationswithinrange:
•VesselMMSInumber.
•Vesselposition(mustbeinputmanuallyifnoGPSposition
dataisavailable).
•Localtime(mustbeinputmanuallyifnoGPSpositiondata
isavailable).
•Natureofthedistress(whendesignated).
•Transmissionfrequency.
Thecallisautomaticallyrepeatedatapproximately4minute
intervalsuntilitisacknowledgedeitherbyacoastradiostation
(CRS)oravesselwithinradiorange.Distresscallsmustbe
followedbyaMAYDAYcallonprioritychannel16.
Urgency
Anurgencycallshouldbeusedwhenthereisdangertoavehicle
orpersonthatdoesnotrequireimmediateassistance.
Whenmakinganurgencycallthefollowinginformationis
transmittedtoallstationswithinrange:
•VesselMMSInumber.
•Vesselposition(mustbeinputmanuallyifnoGPSposition
dataisavailable).
•Localtime(mustbeinputmanuallyifnoGPSpositiondata
isavailable).
•Transmissionfrequency.
OnceanurgencycallissentitmustbefollowedwithaPANPAN
voicemessageonchannel16andincludethenecessarydetails.
Safety
Asafetycallshouldbeusedwhenthereisanimportant
navigationalwarningormeteorologicalforecast/broadcast.
Safetyalertscanalsousedforcommunicationsduringsearch
andrescueoperations.
Whenmakingasafetycallthefollowinginformationis
transmittedtoallstationswithinrange:
•VesselMMSInumber.
•Vesselposition(mustbeinputmanuallyifnoGPSposition
dataisavailable).
•Localtime(mustbeinputmanuallyifnoGPSpositiondata
isavailable).
•Transmissionfrequency.
OnceasafetycallissentitmustbefollowedwithaSECURITE
voicemessageonchannel16andincludethenecessarydetails.
Routinecalls
Routinecallsareusedforcontactingothervessels,marinas,
orshorestations.
Routinecallsaremadeonchannel70usingthededicated
MaritimeMobileServiceIdentity(MMSI)numberofthestation
tobecontacted,selectingaVHFworkingchannelandsending
thecall.Bothradiosautomaticallyswitchtothechosenchannel
forconversation.
Routinecallscanalsobemadetogroups—Whengroupsof
shipsneedthesameinformation(yachtraces,clubralliesetc.)
aspecialgroup-callidentitycanbeusedtoenablerestricted
broadcastcalls.
Note:Totransmitprecisepositions,theradiomustbe
interfacedtoaGPSreceiver.Otherwise,regularmanual
positionupdatingisrequired.
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Ray260