An AIS transponder manages maritime data links. It automatically transmits its own data and receives data from other ships, VTS stations and other AIS stations over the AIS VHF data link. The main onboard components include antennas, a VHF transmitter, multiple VHF receivers, a processor, GNSS timing and redundancy, sensor interfaces, display and input facilities, and a built-in integrity test. AIS primarily uses two dedicated VHF channels and time-division access so participating stations can share the radio link, with current technical characteristics specified in ITU-R M.1371-6. Class A and Class B equipment have different capabilities and reporting behaviour; Class B does not necessarily provide all functions required of Class A equipment.
