Which code stands for the normal switch control relay?

• A. Nwr
• B. Nwz
• C. Nx
• D. Os

Answer: (B)

In this signaling code system, the letters are read as a shorthand for the component’s function and state. The first letter N signals a normal position, the middle letter w identifies the component as a switch (turnout), and the final letter z marks a relay or control device. Put together, Nwz directly encodes a normal switch control relay—the device that monitors or controls the switch when it’s in its normal alignment and feeds interlocking logic accordingly. The other options don’t fit this exact combination: Nx misses the switch-specific designation, and Nwr or Os either imply a different function or a different kind of device. So Nwz is the correct match for the normal switch control relay.