Technical informations - Systems

GMDSS - Global Marine Distress and Selective calling System
Si tratta di una variante del Sitor B, di cui mantine la velocitÓ di 100 Baud e lo shift tipico di 170 Hz ed utilizza un particolare set di 127 simboli unitamente ad una correzione di errore di 10 Bit. Conforme alle specifiche CCIR 493-5 e CCIR 541-2, e da maggio 1999 opera con copertura mondiale. Le frequenze assegnate al servizio GMDSS sono:
2187.5, 4207.5, 6312, 8414.5, 12577 e 16804.5 KHz e in VHF canale 70 156.525 MHz

GMDSS/DSC
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 (also on VHF on Ch. 70 - 156.525 @ 1200bd).