DSC is a paging system that uses data signals to automate the transmission and reception of calls on VHF marine radio channel 70.

A DSC message is a brief burst of digitised information transmitted from one station to alert another station or stations.  The DSC message automatically indicates the identity of the calling station and the priority/purpose of the call. 

Every DSC radio has a unique number, which you use to call other radios, just like a mobile phone.  However, unlike mobile phones, DSC allows you to call every other radio in range at the same time if you are in trouble.

Following an alert by DSC message, communications are established between the transmitting station and the receiving station(s) by radiotelephone on a different channel to that used for the DSC call.

DSC is used by ship and coast stations for sending and relaying distress alerts and for other urgency and safety traffic.  It can also be used for routine calls.

DSC also offers the ability to send and receive GPS positions - all DSC radios can be connected to a GPS receiver.