D Igital S Elective Calling (Dsc); Igital S Elective Calling (Dsc) O N - Raymarine RAY90 Installation & Operating Instruction

6.1 D igital S elective Calling
(DSC)
Traditional VHF radio systems require users to listen
until s omeone speaks, a nd then determine whether t he
call i s for t hem. DSC ensures that c alls are received by
alerting or a nnouncing the intended recipient(s) fi rst s o
they are ready to listen to the subsequent m essage on
the relevant c hannel.
DSC is part o f t he Global M aritime Distress and Safety
System (GMDSS), a maritime communications system
for e mergency and distress messages and all t ypes
of r outine communications such as ship-to-ship or
ship-to-shore.
DSC is a digital s ignalling system, w hich operates on
VHF channel 7 0. DSC calls include other d ata such as
your v essel's identification number, purpose of t he call,
your p osition and the channel y ou want t o speak on.
DSC calls can be divided into 4 categories and are
prioritized as shown below:
Distress 1.
2. Urgency
3. Safety
4. Routine
Distress
A Distress call s hould only be used when there is
imminent d anger t o a vehicle or p erson that r equires
immediate assistance.
When making a distress call t he following information is
transmitted to all s tations within range:
• Vessel MMSI n umber.
• Vessel position (must b e input m anually if n o GPS
position data is available).
• Local t ime (must b e input m anually if n o GPS position
data is available).
• Nature of t he distress (when designated).
• Transmission frequency.
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The call i s automatically repeated at a pproximately 4
minute intervals until i t i s acknowledged either b y a
coast r adio station (CRS) o r a vessel w ithin radio range.
Distress calls must b e followed by a MAYDAY call o n
priority channel 1 6.
Urgency
An urgency call s hould be used when there is danger
to a vehicle or p erson that d oes not r equire immediate
assistance.
When making an urgency call t he following information
is transmitted to all s tations within range:
• Vessel MMSI n umber.
• Vessel position (must b e input m anually if n o GPS
position data is available).
• Local t ime (must b e input m anually if n o GPS position
data is available).
• Transmission frequency.
Once an urgency call i s sent i t m ust b e followed with
a PAN PAN voice message on channel 1 6 and include
the necessary details.
Safety
A safety call should be used when there is an
important n avigational w arning or m eteorological
forecast/broadcast. Safety alerts can also used for
communications during search and rescue operations.
When making a safety call t he following information is
transmitted to all s tations within range:
• Vessel MMSI n umber.
• Vessel position (must b e input m anually if n o GPS
position data is available).
• Local t ime (must b e input m anually if n o GPS position
data is available).
• Transmission frequency.
Once a safety call i s sent i t m ust b e followed with a
SECURITE voice message on channel 1 6 and include
the necessary details.
Routine calls
Routine calls are used for c ontacting other v essels,
marinas, o r s hore stations.
Routine calls are made on channel 70 using the
dedicated Maritime Mobile Service Identity (MMSI)
number o f t he station to be contacted, s electing a
VHF working channel a nd sending the call. Both
radios automatically switch to the chosen channel f or
conversation.
Routine calls can also be made to groups — When
groups of s hips need the same information (yacht r aces,
club rallies etc.) a special g roup-call i dentity can be used
to enable restricted broadcast c alls.
Note: To transmit p recise positions, t he radio must
be interfaced to a GPS receiver. Otherwise, r egular
manual p osition updating is required.
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