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What is DSC?

Digital Selective Calling (DSC) provides a means of automating all day-to-day marine terrestrial calling - making marine radio as easy to use as a telephone. DSC effectively provides the operator with a digital dialling system capable of ringing an alarm at a distant radio station when a call is addressed to that station.

Under GMDSS, all vessels are allocated a unique Maritime Mobile Service Identity (MMSI), which is a unique nine digit code. The digital calling information is transmitted on specially designated channels. In the case of a VHF radio, this is Channel 70. Channel 70 is dedicated for DSC use and must under no circumstances be used for anything else. An added benefit of DSC is that the digital dialling signal can also carry other information, such as your vessel’s identity, position and the nature of the call as well as information specifying the channel upon which subsequent communication should take place. The entire message is transmitted in one quick burst, thus reducing the demand time on the calling channel.

In a distress situation, all necessary information can be sent automatically at the touch of a single button. The vessel’s position can be determined from a GPS navigation receiver connected to the radio or entered manually. Its identity is permanently coded into the radio in the form of the allocated vessels MMSI number. The nature of distress can also be selected by the operator if there is time to do so. Using digital coding, DSC automates all the radio functions with which existing marine operators are familiar.. Operators must be licensed to use the equipment onboard the vessel so, should hold the the RYA Short Range Certificate or equivalent.