KP-27A with built in Class B+ AIS transceiver All Onwa AIS products have a Class B+ AIS transceiver. Class B+ is the later version of the original Class B two Watt system but having five Watts output and using SOTDMA transmitting technology (Class B is CSTDMA). SOTDMA is superior to Class B CSTDMA, not only in being higher power, but also in enabling a transmitting vessel to access a transmission slot in the AIS system even in AIS crowded waters. Class B can reserve a slot but if the AIS system is in heavy use the slot is not guaranteed so it may not be able to transmit until a slot is available. SOTDMA also has an advantage in that the transmission is sent more frequently if the speed of the vessel increases which is highly desirable for high-speed craft such as a RIB. Features of the built-in KP27A AIS transceiver:
