Digital Selective Calling (DSC) is a radio technology allowing enhanced distress radio messages to be sent digitally. In addition, a DSC equipped vessel with an MMSI number can make a "private" hailing call to another DSC-equipped vessel. Only the vessel being called will receive the initial contact, but the subsequent conversations will take place on an open, “working” channel, which can be monitored by any VHF equipped vessel within your broadcast range.