Gmdss Class A Calls; Details Of A "Class A" Call - SEA 7157 Operator's Manual

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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,

DSC

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.