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alert relay.
80.2 Ship stations should normally consider transmitting a distress alert relay only
when a distress alert has been received on 4207.5, 6312, 8414.5, 12577 or
16804.5 kHz and no other station is heard communicating with the distressed
vessel on the associated radiotelephony channel. The distress alert relay must
be addressed to an appropriate maritime communication or limited coast
station. The distress alert relay must not be addressed to "all ships".
80.3 Ship stations receiving a DSC distress alert on either 2187.5 kHz or VHF
Channel 70 should not transmit a distress alert relay. Instead a radiotelephony
acknowledgment should be made to the distressed vessel on 2182 kHz or
VHF channel 16, and the nearest maritime communication station or limited
coast station should be informed.
80.4 Ship stations may transmit a DSC distress alert relay in situations where a
distress alert has not been received. However, this is restricted to situations
where it is learnt that another vessel in distress is not able to transmit the
distress alert and the Master of the ship not in distress considers that further
help is necessary. In this case the DSC distress alert relay should be in the
"all ship" format or, preferably, addressed to an appropriate maritime
communication station or limited coast station.
80.5 Some small vessel DSC transceivers may not provide a DSC distress alert
relay facility. In these situations a MAYDAY RELAY message on the
associated radiotelephony frequency may be substituted and every endeavour
made to inform a maritime communication station or limited coast station. In
the situation detailed in paragraph 80.3, the MAYDAY RELAY message should
be transmitted on a radiotelephony frequency or channel considered
appropriate to the situation. A MMSI may be used in cases where a vessel's
name and call sign are not known.
80.6 Operators should exercise careful judgement in relaying DSC distress alerts
received on the higher frequencies as these could be received from and by
vessels at distances of thousands of miles. Indiscriminate relaying will merely
increase the area that stations are alerted without performing any useful
function.
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81. Acknowledgment of a DSC Distress Alert Relay
81.1 Where considered appropriate, ship stations receiving a DSC distress alert
relay from another station should acknowledge receipt by radiotelephony on
the associated radiotelephony frequency/channel using the procedures
detailed in paragraph 61 of this handbook.
82. Cancellation of an Inadvertent DSC Distress Alert
82.1 Unlike radiotelephony procedures, it is possible to inadvertently initiate a DSC
distress alert. Should this occur then it is essential that the initiating station
immediately carry out the following procedures:
" immediately switch off the transceiver in question (this will cancel
any automatic repeats of the DSC distress alert which would
normally continue until a DSC acknowledgment is received); then
" switch the transceiver back on and select the radiotelephony
frequency/channel associated with the DSC frequency/channel on
which the inadvertent alert was transmitted; then
" broadcast an "all stations" radiotelephony message giving the
vessel's name, call sign and MMSI, and cancel the distress alert,
giving an approximate time of the inadvertent transmission.
If the inadvertent DSC distress alert was transmitted on several frequencies, it
is necessary to broadcast cancellations on all associated radiotelephony
frequencies.
82.2 If for some reason these procedures cannot be carried out then the station
must use other means to advise authorities that the alert was accidental.
82.3 Failure to appropriately advise authorities may result in the distress alert being
treated as genuine and lead to a waste of valuable search and rescue
resources. A ship station operator will not be penalised for reporting an
inadvertent distress alert.
83. Transmission of a DSC Urgency Alert
83.1 A DSC urgency alert may be transmitted only with the authority of the master
or skipper, or the person responsible for the safety of the vessel. It indicates
that the station has a very urgent message to transmit concerning the safety of
a vessel or aircraft, or the safety of a person.
83.2 The transmission of a DSC urgency alert by maritime communication, limited
coast and ship stations is carried out in the following manner:
" the announcement of the urgency message by DSC alert on a DSC
frequency/channel; followed by
" the transmission of the urgency call and message on the
associated radiotelephony frequency/channel using radiotelephony
procedures.
83.3 The announcement is carried out by:
" tuning the transceiver to the appropriate DSC frequency or channel
(2187.5 kHz, VHF channel 70 etc);
" selecting the "all ship" call format;
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" selecting the urgency priority; and
" transmitting the DSC urgency alert
83.4 The transmission of the urgency call and message should follow immediately
on the associated radiotelephony frequency/channel using the radiotelephony
procedures detailed in paragraph 67 of this handbook.
83.5 Stations receiving a DSC urgency alert should not acknowledge receipt but
simply tune their transceiver to the associated radiotelephony
frequency/channel and await the radiotelephony transmission.
83.6 Should the initiating station wish that the urgency alert is received only by a
particular station, then the "single ship" call format should be selected. In this
case the MMSI of the station must be known and programmed into the
transceiver.
Steps to transmit a DSC urgency alert and subsequent urgency call and
message
Select Initiate Change to Transmit
DSC DSC Associated Radiotelephony
Distress Urgency Radiotelephony Urgency Call
Channel Alert channel and Message
84. Transmission of a DSC Safety Alert
84.1 The transmission of a DSC safety alert indicates that the station has a
message to transmit concerning an important navigational or weather warning.
84.2 The transmission of a DSC safety alert by maritime communication, limited
coast and ship stations is carried out in the following manner :
" the DSC announcement of the safety message by DSC alert on a
DSC frequency/channel; followed by
" the radiotelephony announcement on the associated
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