Which code represents 24 volt DC common?

• A. CX
• B. CX24
• C. C24
• D. CBX24

Answer: (C)

The essential idea is how wiring is labeled by function in a 24 V DC control circuit. The common, or return, conductor—the reference point for the entire circuit—is indicated by the single letter C. This concise designation keeps the label unambiguous on diagrams and wiring.

Seeing the label simply as C makes it clear it’s the common return path. Adding extra characters like X or B, or including the voltage in the label (such as CX24 or C24), changes the meaning away from the plain return conductor. The extra letters or digits imply a variant, connector, or a specific version of something, not the fundamental common reference.

So the best match for the 24 V DC common is the straightforward C designation.