List IV contains important information for the mariner in relation to radiocommunications, including GMDSS (Global Maritime Distress and Safety System) and CP (Public Correspondence) services. Detailed information is provided in relation to the facilities available at each maritime coast radio station. These stations may provide watch-keeping using digital selective calling (DSC) techniques and radiotelephony. The frequencies for transmitting and receiving and the geographical coordinates for each station are listed. Details of additional services such as medical advice, navigational and meteorological warnings, MSI (Maritime Safety Information), AIS (Automatic Identification System), meteorological bulletins and radio time signals are also provided, along with hours of service and operational frequencies. List IV also contains information on port stations, pilot stations, coast Earth stations, VTS stations, contact information of RCC (Rescue Coordination Centres), SAR agencies, NAVAREA coordinators and AtoNs (AIS Aids to Navigation). It should be noted that no supplements will be printed between two editions. However, the compilation of changes notified to this List, will be made available for information and free of charge, through the ITU MARS webpage.www.itu.int/en/ITU-R/terrestrial/mars/Pages/MARS.aspx
Users may also visist the MARS site to retrieve and/or submit information related to the maritime database. Guidelines and forms are available in order to support this activities.