The
primary function of the NGW-1’s NMEA 0183 LED is to indicate reception
of a valid NMEA 0183 sentence.
The NMEA 2000 LEDs main function is to
indicate reception of a PGN on the NGW-1 conversion list.
For more information on the LED behaviour and what it indicates, please refer to this Article: https://www.actisense.com/knowledge-base/nmea-2000/ngw-1/ngw-1-normal-led-behaviour/
The LED behaviour of the NGT / NGW is also detailed in the UM.