GMDSS/DSC

Global Marine Distress and Selective calling System, ATIS used on VHF channels in some countries (Germany,The Netherlands).

Digital Selective Calling is a variation of Sitor-B, 100 baud 170 shift, but uses a special set of 127 symbols with a 10 bit error correcting code. The system is defined in the ITU recommendation ITU-R M493-6. A DSC signal is short, about 6-7 seconds on MF/HF and contains the following:

station ID, priority, station being called, frequency to use. This system is used to establish the initial contact between ships and shore stations using GMDSS.

DSC signals can be found the following frequencies:

2187.5, 4207.5, 6312.0, 8414.5, 12577.0, 16804.5