Navigation General · AIS
A Class B AIS transponder differs from Class A in that Class B:
- ATransmits at higher power and a faster update rate
- BIs required on all SOLAS vessels regardless of size
- CTransmits at lower power with a slower position update rate and does not transmit voyage data✓ Correct
- DProvides encrypted position reports accessible only to coast guard stations
Explanation
Class B AIS is designed for non-SOLAS vessels (recreational and small commercial craft). It transmits at 2 watts (vs. 12.5 W for Class A), updates position every 30 seconds when moving at less than 2 knots and every 3 seconds at higher speeds (slower than Class A), and does not include some voyage-data fields such as destination and ETA. Class A is mandatory on most SOLAS vessels.
Authority: Bowditch (Pub. 9), Ch. 13
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