What physical topology does NMEA 2000 use, and what must be installed at the ends of the backbone?

• A. A star topology with a central hub and no terminators.
• B. A ring topology with 120-ohm terminators at each node.
• C. A trunk-and-drop CAN bus topology with terminators; 120-ohm terminators are required at both physical ends of the backbone.
• D. A linear bus with terminators at both ends and no junctions.

Answer: (C)

NMEA 2000 networks use a trunk-and-drop CAN bus: a single backbone carries the signal and each device connects to it with a short drop cable. To keep the signal clean and prevent reflections on the CAN pair, the backbone must be terminated at both physical ends with 120-ohm resistors connected across CAN High and CAN Low. This setup isn’t a star network (no central hub) or a ring, and the existence of drops means there are junctions along the backbone. The terminators belong only at the ends of the backbone, not at every device connection.