List IV contains important information for the mariner in relation to radiocommunications, including the 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, which may provide watch-keeping using digital selective calling (DSC) techniques and radiotelephony. Also included are receive and transmit frequencies, as well as the geographical coordinates for each station. List IV also lists 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, along with the hours of service and operational frequencies. It also contains information on port stations, pilot stations, coast Earth stations, VTS stations, contact information of RCC (Rescue Coordination Centers), SAR agencies, Navarea coordinators and AtoNs (AIS Aids to Navigation).