Class B units are different from Class A devices in that they are less powerful, don’t need to include an integrated display and use their receivers differently. Because of these, and more differences, Class B units are not able to be used on large vessels over 300 gross tonnes or passenger vessels on international voyages.
The feature giving the the most significant reduction in performance between a Class B and Class A device is power. Class B devices operate on 2W output, compared to Class A’s 12.5W, which significantly limits the range available. However, the price of Class B units against Class A devices mean that smaller vessels are able to experience the benefits AIS gives at a reasonable price.
When purchasing a Class B transciever you need to consider:
- It's price
- Dimensions
- Whether it comes with a display
- What interfaces are available
- If it includes an internal antenna splitter
- Whether it can run in silent mode and how it is activated
- What IP rating the enclosure is
- Whether it is fully approved and by who
- If it has a multiplexer
- What software is provided