Specifications

between termination resistors. However, if the distance from
a trunk line tee to the farthest device connected to the trunk
line is greater than the distance from the tee to the nearest
terminating resistor (TR), then you MUST include the drop
line length as part of the cable length in your maximum cable
distance calculation. Figure 2 shows an example where both
5 meter drops must be included in the maximum cable
distance since the drops are longer than the distance from
the tee to termination resistor.
1.3 Cumulative Drop Line Length
The cumulative drop line length refers to the sum of all drop
lines, Mini, Mid or Micro cable in the cabling system. This
sum cannot exceed 78 meters (256 feet). Figure 3 shows
an example using four drop tees and two multiport drops to
attach 11 devices to the trunk line. The cumulative drop line
length is 37 meters (122 feet) and no single device is more
than 6 meters (20 feet) from the trunk line.
1.4 Maximum Drop Line Length
The maximum cable distance from any device on a branching
drop line to the trunk line is 6 meters (20 feet).
1.5 Maximum Number of Devices
A maximum of 50 physical devices shall be connected to
the network, and the disconnection of any device shall not
interrupt any other device on the network.
1.6 NMEA 2000® Cable
The Mini, Mid and Micro cables contain five wires: One
twisted pair (red and black) for 12VDC power, one twisted
pair (blue and white) for signal and a drain wire (bare).
The following table shows the color, name, and usage for
each wire contained within the cable.
Color Name Usage
White NET-H Signal
Blue NET-L Signal
Bare SHIELD Drain
Black NET-C Ground
Red NET-S Power
Figure 3
Maximum
Cumulative
Drop Line Length
Determination
70
Multi
Port
Box