Which code is for 'Reverse switch operating relay'?

• A. RWZ
• B. RN
• C. RWR
• D. RVP

Answer: (C)

In signaling codes, three-letter abbreviations are built from pieces of the device description: the first letter often signals the action or state, the middle letter marks the component or the operation related to the device, and the last letter identifies the device itself. For “Reverse switch operating relay,” the order aligns with Reverse at the start, a middle element tied to the switch operation, and Relay at the end. That combination forms R-W-R, corresponding to Reverse–Switch-Operating Relay in this coding scheme. The other options introduce letters that don’t match the described components (for example, ending with a letter that isn’t Relay or replacing the middle element with something unrelated), so they don’t fit the phrase.