The coded DSC transmission also includes an indication of a call’s priority:-


Distress — equivalent to “Mayday” in voice procedure;


Urgency — equivalent to “Panpan” in voice procedure;


Safety — equivalent to “Securitay” in voice procedure; 


Ship’s business (not on class D controllers); 


Routine.


In most cases, the priority of the call is decided automatically by the software within the DSC controller. It is pretty obvious, for instance, that a distress call cannot be sent with anything less than distress priority.


DSC controllers and position


A DSC controller needs to “know” the boat’s position, if only so that it can include it in a distress alert.


To do this, it must be interfaced (connected) to a GPS receiver, which will then send position and time updates to the DSC controller about once every second or so.


As a back-up, the position and time can be keyed in manually.


Using a Class D controller


There is no standard layout for the control panel of a Class D DSC controller, although there are certain similarities between the different makes and models:-


they all feature a prominent “Distress” button, protected by a cover to prevent accidental operation


 


most have an alphanumeric keypad, similar to that of a mobile phone

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