The best way to confirm whether or not your unit is transmitting is to ask another AIS equipped vessel (within the near vicinity) if they can see your AIS information on their own display. AIS websites should not be relied on as they do not always show real-time AIS information.
The following LED flash sequence will also indicate if the unit is transmitting;
1 short flash in 5 seconds for Red LED variant
1 short green flash in 5 seconds for RGB LED variant