The AIS data telegrams can be transmitted using various methods. So far, the CSTDMA (Carrier Sense Time-Division Multiple Access) method has been used for leisure shipping (Class B). The SOTDMA technology (Self-Organized Time-Division Multiple Access) was previously reserved for commercial shipping (Class A), but is now also approved for Class B level.
AIS receivers receive the AIS signals transmitted by commercial shipping (class A) and pleasure craft (class B) via a VHF antenna and convert them into an NMEA protocol. This data can then be further processed by a chart plotter or by PC software and displayed on the appropriate screens. Class B AIS transmitters/receivers simultaneously transmit own ship data to all AIS devices in the vicinity.