Aids to Navigation devices can be found out at sea, or near to port, generally on buoys. They can perform many different functions from carrying out hydrological and metrological tests to extending the range of base stations; and from monitoring vessels to warning them of any hazards. AtoNs are highly configurable and can include many different circuit boards or inputs and outputs to meet the requirements.

The main constraints to AtoNs are power consumption and price. AtoNs are primarily situated on buoys at sea which have limited power supplies – usually a solar panel powers all the buoy’s functions. Therefore, the AtoN must keep power to an absolute minimum whilst carrying out its functions. This causes a problem for AtoNs using the RATDMA protocol as they must power up receivers for one minute prior to transmission to search for available space in the AIS slot map.

Aids to Navigation come in three different types.  Type one just transmits data, type two transmits and receives data via another source (eg. GSM), and type three transmits and receives via AIS. Types one and three are the most popular on the market.

When purchasing an AtoN, you need to consider:

• It's power consumption
• Price
• Serial interfaces available
• Analogue interfaces available
• Digital interfaces available
• What type it is
• Whether it is designed for inside or outside the buoy