Which code represents a 14 volt DC line common?

• A. Lb
• B. Nlp
• C. Lc
• D. Ns

Answer: (C)

In this labeling system, the prefix or first letter indicates the general function, and the suffix defines its specific role. For a DC signaling line, the line that serves as the return path or reference is labeled with a “c” for common. So the conductor designated as the 14-volt DC line’s return path is called the line common, abbreviated as Lc. That makes it the correct choice because it explicitly identifies the common return conductor of the 14 V DC line.

The other codes imply different roles (such as other line functions or separate circuits) and do not represent the return path for the 14 V DC line, so they don’t fit as the line common.