What a delight to have such informed discussion on my inquiry in less than twelve hours. Many thanks to all who commented.
If I may summarize:
--all the AIS
Class-B transponders presently being made are of the carrier sense time division multiple access type (CSTDMA), as opposed to the self-organizing time division multiple access (SOTDMA) that is used in Class-A devices; and these Class-B transponders are all 2-Watt transmitters;
--there is some allowance for a sort of hybrid Class-B transponder with SOTDMA and 5-Watt transmitters, but there are actually none of these available on the market today;
require an AIS
Class-B transponder to have a dedicated GPS receiver, and with good reasons, including having a single
integrated system that provides the entire functionality needed and to be able to certify the device or system as being compliant;
--but some models of AIS Class-B transponder allow for configuration of the device to use an input from another GPS receiver, thus ignoring their own internal GPS receiver.
Is that a fair summary?