Mike — NMEA2000 (and SeaTalkNG) are just variants on the CANBus data bus 
architecture, which is used heavily in industrial control and automotive 
systems.  Your car probably has many dozens of CANBus nodes in it; virtually 
everything these days is controlled over a CANBus system between the car’s 
computer and all the various components that are monitored and controlled.

The system uses a backbone with spurs from it to the devices.  Each end of the 
backbone needs to be properly terminated to avoid signal reflection issues.

So you need a terminator at each end of the backbone, regardless of whose 
system you’re using.  All the marine manufacturers now use either the NMEA2000 
standard (which uses DeviceNet cables and connectors) or a variant on it.  
SeaTalkNG uses different connectors, and also adds a sixth wire to the 
standard’s five wires (+ and – power, + and – data and shield) to carry legacy 
SeaTalk1 signals, so it will be backwards-compatible with some older Raymarine 
gear.

Probably more info than you needed…   :^)

— Fred

Fred Street -- Minneapolis
S/V Oceanis (1979 C&C Landfall 38) -- Bayfield, WI

> On Sep 11, 2015, at 7:26 AM, Hoyt, Mike via CnC-List <[email protected]> 
> wrote:
> 
> Fred
>  
> This reminds me of early Ethernet and Arcnet computer network cabling.  I was 
> hoping the days or requiring a terminator were in the far distant past.
>  
> Do you recall if the i50/i60 style networks also require a terminator? It 
> seems to me I had to buy a couple of items that look like that is what they 
> are
>  
> Mike

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