For pleasure crafts used only for recreational or fishing purposes, there is no obligation to equip AIS transceivers.
However, since an AIS transceiver has many advantages, there are the so-called Class B AIS transceivers. Class B AIS transceivers are generally less expensive than class A transceivers because there are less strict requirements for their performance. Class B transceivers are reduced to the most important data. Often only the MMSI number of the vessel, the current position, course, and size are transmitted. This makes the operation of class B transceivers very easy. The vessel name and dimensions must be programmed once, then the AIS transceiver is ready for use.
Class B AIS transceivers have a lower reporting rate than class A transceivers. Their maximum transmission power is 2W. While class A transceivers use a complex system (SOTDMA = Self Organising Time Division Multiple Access) to coordinate with other transceivers in the environment to occupy the transmission frequencies, class B transceivers usually simply use the free time slots to transmit their data (CSTDMA = Carrier Sense Time Division Multiple Access).
However, there are also class B AIS transponders that make use of SOTDMA technology. The transmission frequency of AIS data in class B transponders depends on the speed of the vessel and the frequency utilization and ranges from every 5 seconds to every 3 minutes.
