7-13
2. Countermeasures against Various Failures
6. DSC communication can not be performed.
Are the scan frequencies for general watch keeping selected?
The transmitting station specifies DSC transmitting/receiving frequencies; sends ACK RQ message; and
waits for ACK BQ signal from the receiving station. The receiving frequency of the transmitting station
is the transmitting frequency of the receiving station.
The receiving station receives the messages at the transmitting frequency of the transmitting station, and
sends ACK BQ signal at the receiving frequency of the transmitting station. DSC message does not
include DSC communication frequencies.
The ship-to-ship DSC communication is made at same frequency in both transmission and reception,
while the ship-to-shore communication is made with a pair of frequencies assigned to the station.
In the case of DSC-60:In the case of DSC-60:
In the case of DSC-60:In the case of DSC-60:
In the case of DSC-60:
DSC-60 receives ACK RQ signals with the registered scan frequencies and transmits ACK BQ signals
at the frequency paired with the received signal frequency.
Be sure to register the scan frequencies and perform the listening on those frequencies.
At the communication on 2177/2189.5 kHz;
- If ACK RQ is received from a ship (known from MMSI No.), transmit ACKBQ signal at the
same registered frequency as that of the received signal.
- If ACK RQ is received from a coast radio station (known from MMSI No.), transmit ACKBQ
signal at the registered frequency paired with the receiving frequency.
Sending Receiving
ACK RQ
ACK BQ
Tx:2177kHz
Tx:2177kHz
Rx:2177kHz
Rx:2177kHz
ex)MMSI:431456789
Setting scan frequency
Tx:2189.5kHz
Rx:2177kHz
Setting DSC frequency
Tx:2177kHz
Rx:2177kHz
Sending(Ship) Receiving(Coast)
ACK RQ
ACK BQ
Tx:2189.5kHz
Tx:2177kHz
Rx:2177kHz
Rx:2189.5kHz
Tx:2177kHz
ex)MMSI:004314567
Setting DSC communication
freqency
- Tx:2189.5kHz
- Rx:2177kHz
Ship to Shore communication at MF band.
Ship to Ship communication at MF band.
Communication on HF band
When DSC individual call uses paired frequencies such as international parired frequency, Tx frequency in the paired
frequency is used to send ACK RQ, and paired RX frequency is used to receive ACK BQ.
For intership calling, the same frequency is registered onto transmitting and receiving user channels. A message sending
station uses the registered frequency when creating a message. A message receiving station uses the registered frequency
when registering scanning frequencies.
* Group of ships and geographical area calls use only TX frequency in the paired frequency because no
reception is made.
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