Class A transceivers are designed to meet the carriage requirements of the IMO for large, ocean going, vessels on an international voyages. In simple terms, the IMO requirements state that vessels over 300 gross tonnes and passenger vessels on international voyages must have a Class A AIS device fitted.
Class A devices use SOTDMA to transmit and receive data. Using this system, their space in the AIS slot map is reserved, so every AIS message gets through. They also have any subsequent AIS space reserved for them so they don’t have to scan for free slots like Class B units do.
When purchasing a Class A unit, you should take into account:
- The price
- Dimensions
- Whether it is a single or multiple units
- The size and make up of the display
- The user interface
- What approvals are included
- Whether it has European Inland Waterway approval
- What interfaces are included
- Power supply voltage
- What languages are supported
- What it's operating temperature is
- What IP rating it has
- What accessories you get with it