SEA 7157, Operator'S Manual, Page: 26 / 49

GMDSS CLASS A CALLS
21
DETAILS OF A “CLASS A” CALL
The DSC call formats described earlier in this manual are predefined message
formats of all the possible formats defined by ITU 493. The predefined versions
allows the operator to place calls quickly and efficiently without having to input
several keypresses for most routine calls.
Calls that contain more specific information, such as requiring a data response
rather than voice communications, must access the CLASS A menu to create these
types of messages. The following describes the structure or organization of
CLASS A calls for the sections dealing with the individual format types.
To transmit a DSC call using the Class A format,
press
.
Most calls contain the following information:
Format Type, Priority Category, Telecommand1, Telecommand2
The CLASS A menu gives 6 DSC format types that may be used for calling.
DSTRESS , ALLSHIPS , INDIVIDL and
PHONE have a predefined or simple version
message format. GEOAREA and GROUP , do
not have predefined message formats.
Depending on which DSC format was selected,
the operator may be prompted for additional
information before the priority category prompt
appears. The format type of Distress (not a priority category of distress) has a
specific structure and will prompt for the nature of the distress rather than a priority
category.
The priority category designates the importance of the selected message format.
Routine indicating a normal priority.
Ship Business relates to management of the ship.
Safety indicates important navigational or
meteorological warning.
Urgency
relates to safety of life or property.
Distress is grave and imminent danger to life and
property with immediate assistance required.
3:01 47° 47N 122° 19W
1=DSTRESS
3=GEOAREA
5=GROUP
1
US EXAMP
A
2=ALLSHIPS
4=INDIVIDL
6=PHONE
Format Types
3:01 47° 47N 122° 19W
1=REVIEW
3=DSC
5=RELAY
7=PHONE
1
US EXAMP A
8=CLASS A
2=PROGRAM
4=ALT CHAN
6=ALL SHIP
Primary DSC menu selections
8
T
U
V
DSC
3:01 47° 47N 122° 19W
1=ROUTINE
3=SAFETY
5=DISTRESS
1
US EXAMP
A
2=SHIP-BUS
4=URGENCY
Priority categories