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2. DSC OVERVIEW
2-2
Contents of a DSC call
• Calling category
DISTRESS
: DISTRESS ALERT, DISTRESS RELAY ALL, DISTRESS RELAY IN-
DIVIDUAL, DISTRESS RELAY AREA (Received only), DISTRESS ACK
GENERAL
: MEDICAL MSG, NEUTRAL MSG, INDIVIDUAL MSG, PSTN MSG,
TEST MSG, GROUP MSG, ALL SHIPS MSG, POSITION MSG, POLLING MSG
• Station ID (MMSI)
Your ship ID and sending station ID. Coast station ID begins with 00; Group ID be-
gins with 0.
• Priority
Distress
: Grave and imminent danger and request immediate assistance.
Urgency
: A calling station has a very urgent call to transmit concerning safety of
ship, aircraft or other vehicle or safety of person.
Safety
: A station is about to transmit a call containing an important navigational or
meteorological warning.
Routine
: General calling
• Communication mode
TELEPHONE
: Telephone (F3E/G3E) by VHF radiotelephone
• Communication channel
Working frequency channel used to call by telephone. The sending station may
have the receiving station (ship or coast station) assign the frequency channel to
use.
• Position
Position can be automatically or manually set.
• End code
The end of a DSC call is indicated with "EOS" (acknowledgement, acknowledge-
ment required, no acknowledgement required).
2.3 Audio Alarms
When you receive a distress alert or general call addressed to your ship, the audio and
visual alarms are released. The audio alarm can be silenced with the CANCEL key.
Alarm When Frequency (interval)
Count
alarm
Counting down the time remaining before the distress
alert is transmitted.
2000 Hz (500 ms) → silent
(500 ms); three times
Distress
RX alarm
The following sessions are received:
distress alert, relay individual, relay area, or relay all.
2200 Hz (250 ms) → 1300 Hz
(250 ms); repetition
Distress
TX alarm
Sending or resending the distress alert. 2200 Hz (2000 ms); once
Distress
ACK
alarm
The following sessions are received or received then ac-
knowledged:
distress ACK, distress ACK (cancel ACK), relay individ-
ual ACK, or relay all ACK.
2200 Hz (500 ms) → 1300 Hz
(500 ms); repetition
Urgency
alarm
The following urgency sessions are received:
all ships, neutral, medical, or individual.
2200 Hz (250 ms) → silent
(250 ms); repetition
Urgency
ACK
alarm
The sessions for urgency individual ACK are received
then acknowledged. The sessions for delayed ACK are
received.
2200 Hz (500 ms) → silent
(500 ms); repetition