They are divided into conventional and satellite communications
Conventional (terrestrial) communications:
They operate in the MF, HF, and VHF frequency areas. They use the digital selective-calling (DSC), radiotelephony, radioteletypy, NAVTEX and RADAR transmitters.
They are conducted via the satellite systems Inmarsat and Compass-Sarsat.
International satellite maritime organization that operates with four geostationary satellites that characterize the four oceanic regions of the system:
AOR- E: Atlantic Ocean Region East
AOR- W: Atlantic Ocean Region East
POR: Pacific Ocean Region
IOR: Indian Ocean Region
A polar- orbiting satellite system that receives and retransmits ‘EPIRB’ distress alerts.