If the GMDSS Radio Operator does not have time to select the follow on frequency/mode then the unit will default to the standard answering frequency and mode .
With the DSC system we can indicate the Priority of these Communications, Distress, Urgency, Safety or Routine. When using the "All Ships" Distress mode then the radios will set up on the Highest Priority .
If the GMDSS Radio Operator does not have time to enter all the extra information by keying it into the equipment, the nature of the distress will be "UNSPECIFIED" on the screen or on the printed record.
If a distress alert is received the bridge alarm will sound. The DSC will display, or print the alert message, including the MMSI of the calling station. The rest of the total message will print, priority of communications, time of receipt, Follow on communications, and time of receipt.
To insure that someone will hear the distress alert, the call is repeated a second time. In VHF the call is repeated a second time, if it is not answered the first time. In the case of MF/HF the distress alert is sent out on the six DSC frequencies and then there is a timed wait (to see if someone answers the alert) then this sequence is repeated. If there is no answer then the GMDSS Radio Operator can repeat the distress alert a second time.
The receiving station will acknowledge the DSC call with an DSC "Acknowledge" and will move to the new working frequency. If the sending station did not have time to insert the variable individual messages then the method of communications will be Radiotelephone.
To increase the probability of reception for DSC distress calls, it is wise to repeat the alert several times until you obtain a response, at regular intervals .
It is wise to wait form 3 to 5 minutes to allow the coastal station time to answer and/or notify the Coast Guard or other authority before answering the alert. Relaying the distress alert might do more harm to the radio waves and good. Due to HF propagation you might not be in the range of another station that may be answering the distress alert.
