Which of the following describes Ethernet in a BAS context?

• A. A device that prints alarms
• B. A local area network architecture that can connect up to 1024 nodes and supports data transfer rates of 10 megabits per second
• C. A handheld device used for field service
• D. A wireless protocol for sensors

Answer: (B)

Ethernet is a wired local-area network technology used to connect BAS devices such as controllers and sensors, allowing them to share data over a common network. In its classic form (often called 10BASE-T), Ethernet defines how devices address and transmit data over the network and historically supports up to about 1024 nodes at a data rate of 10 megabits per second. In a building automation setting, this means it’s the standard way devices communicate over a wired LAN, providing a common, interoperable networking foundation.

This matches the description of a local area network architecture that can connect up to 1024 nodes and supports data transfer rates of 10 Mbps. It’s not a device that prints alarms, not a handheld field service tool, and not a wireless protocol for sensors—the latter would refer to wireless technologies, whereas Ethernet in this context is wired.