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How do I give my GPS unit priority on the NMEA data Mulitplexer network?

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The Actisense NDC-2 and NDC-3 have many useful features, among which is the ability to prioritise their input ports. The usefulness of this feature becomes apparent when the NMEA network is running over 50% loading/capacity (most setups). At this point a standard NMEA Multiplexer could start to delay the important information by an unacceptable amount and may even lose it altogether.

The Actisense NDC however, will always transfer the highest priority input’s NMEA sentences first, keeping the delay to the minimum possible. The remainder of the inputs will have their NMEA sentences transferred in turn, until all data is either transferred or no more time / bandwidth is available in the NMEA output.

For example, the most relied upon unit e.g. GPS, should be attached to input port 1 (the highest priority). It is possible to change the port priority order from within the Control Centre software if you do not want to manually reconnect the cables to the Actisense NDC. However, it may be simpler to keep the port priority in a logical order (1 highest – 4 lowest).

The Actisense NDC-2 ‘Port Priority’ default is the same as the port number, i.e. port 1 is the highest priority and port 4 the lowest.


Take a look at the newer NDC-5 unit.

For more information on NMEA 0183 and how it works, please download our free guide to NMEA 0183 networking.
For more information on NMEA 2000 and how it works, please download our free guide to NMEA 2000 networking.