What does the SFD signal indicate to the receiving device?

The SFD (Start Frame Delimiter) signal has a specific role in network communication protocols, particularly in Ethernet frames. Its primary function is to signal to the receiving device that the preamble portion of the frame, which is used for synchronization, has concluded. Following the SFD, the actual frame contents, such as the source and destination addresses and the data, will begin. This helps the receiving device prepare to interpret the incoming data appropriately.

The preamble consists of bits that allow the network interface to synchronize with the incoming signals; once this is done, the SFD indicates that the frame's actual data is about to start. This is crucial for ensuring that the device can correctly process and understand the information being transmitted.

In contrast, the other options relate to different aspects of data transmission. Starting a new packet, signaling the end of a transmission, or indicating transmission errors pertain to different protocols/functions and do not define the purpose of the SFD. Understanding the SFD's function helps in grasping the flow of data in networking and reinforces the importance of precise signaling in ensuring effective communication.