systems within their STN Atlas VTS installations. in the efficiency and safety of their operations. operator complete control over it. automatically. receive its messages. within a designated area for which there is a central control. options unavailable on the AIS system. reporting intervals and content of the transponder signals. from the display if crowding makes it desirable. the radar track table data back to the port control. data links between each station and the control headquarters. linked to a TDMA receiver. pilots and harbor craft. a TDMA unit operating within the area.