NMEA 2000 is intended as a plug & play data transmission network, with a structure linked to a central cable (CANbus) through which all the instruments of the network are connected to provide or read information, but also to be able to be powered (if these do not need an independent power supply).
The NMEA 2000 is therefore considered a sort of LAN (Local Area Network) on board, where all the information provided by the various devices of the boat run, with a data rate of 250 Kbps.
The National Marine Electronics Association not only outlines the standards of data packet composition, but also the specific wiring components. Manufacturers that fully comply with these standards can produce NMEA 2000 certified devices.
Some manufacturers use proprietary standards, where many of the specifications are similar to NMEA 2000, but differ either in the configuration of the data package or in the wiring or in the connectors and in this case they cannot declare their devices NMEA 2000 certified.