Raymarine RAY70 - Digital Selective Calling (DSC)

7.1DigitalSelectiveCalling(DSC)
TraditionalVHFradiosystemsrequireuserstolisten
untilsomeonespeaks,andthendeterminewhether
thecallisforthem.DSCensuresthatcallsare
receivedbyalertingorannouncingtheintended
recipient(s)rstsotheyarereadytolistentothe
subsequentmessageontherelevantchannel.
DSCispartoftheGlobalMaritimeDistress
andSafetySystem(GMDSS),amaritime
communicationssystemforemergencyanddistress
messagesandalltypesofroutinecommunications
suchasship-to-shiporship-to-shore.
DSCisadigitalsignallingsystem,whichoperates
onVHFchannel70.DSCcallsincludeotherdata
suchasyourvessel’sidenticationnumber,purpose
ofthecall,yourpositionandthechannelyouwant
tospeakon.
DSCcallscanbedividedinto4categoriesandare
prioritizedasshownbelow:
1.Distress
2.Urgency
3.Safety
4.Routine
Distress
ADistresscallshouldonlybeusedwhenthereis
imminentdangertoavehicleorpersonthatrequires
immediateassistance.
Whenmakingadistresscallthefollowinginformation
istransmittedtoallstationswithinrange:
•VesselMMSInumber.
•Vesselposition(mustbeinputmanuallyifnoGPS
positiondataisavailable).
•Localtime(mustbeinputmanuallyifnoGPS
positiondataisavailable).
•Natureofthedistress(whendesignated).
•Transmissionfrequency.
Thecallisautomaticallyrepeatedatapproximately
4minuteintervalsuntilitisacknowledgedeitherby
acoastradiostation(CRS)oravesselwithinradio
range.DistresscallsmustbefollowedbyaMAYDAY
callonprioritychannel16.
Urgency
Anurgencycallshouldbeusedwhenthereis
dangertoavehicleorpersonthatdoesnotrequire
immediateassistance.
Whenmakinganurgencycallthefollowing
informationistransmittedtoallstationswithinrange:
•VesselMMSInumber.
•Vesselposition(mustbeinputmanuallyifnoGPS
positiondataisavailable).
•Localtime(mustbeinputmanuallyifnoGPS
positiondataisavailable).
•Transmissionfrequency.
Onceanurgencycallissentitmustbefollowed
withaPANPANvoicemessageonchannel16and
includethenecessarydetails.
Safety
Asafetycallshouldbeusedwhenthereisan
importantnavigationalwarningormeteorological
forecast/broadcast.Safetyalertscanalsoused
forcommunicationsduringsearchandrescue
operations.
Whenmakingasafetycallthefollowinginformation
istransmittedtoallstationswithinrange:
•VesselMMSInumber.
•Vesselposition(mustbeinputmanuallyifnoGPS
positiondataisavailable).
•Localtime(mustbeinputmanuallyifnoGPS
positiondataisavailable).
•Transmissionfrequency.
Onceasafetycallissentitmustbefollowedwith
aSECURITEvoicemessageonchannel16and
includethenecessarydetails.
Routinecalls
Routinecallsareusedforcontactingothervessels,
marinas,orshorestations.
Routinecallsaremadeonchannel70usingthe
dedicatedMaritimeMobileServiceIdentity(MMSI)
numberofthestationtobecontacted,selectinga
VHFworkingchannelandsendingthecall.Both
radiosautomaticallyswitchtothechosenchannel
forconversation.
Routinecallscanalsobemadetogroups—When
groupsofshipsneedthesameinformation(yacht
races,clubralliesetc.)aspecialgroup-callidentity
canbeusedtoenablerestrictedbroadcastcalls.
Note:T otransmitprecisepositions,theradio
mustbeinterfacedtoaGPSreceiver.Otherwise,
regularmanualpositionupdatingisrequired.
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Ray50/Ray60/Ray70