Which device maps to code XS?

• A. Bell
• B. Contact rail indicating relay
• C. Contact rail alarm bell
• D. Exit push button stick repeater relay

Answer: (D)

In signaling practice, two‑letter codes name specific pieces of equipment used in interlocking and track circuits. The code XS is assigned to the exit push button stick repeater relay. This device's role is to duplicate or repeat the action of an exit push button so that the interlocking can register the command even when the button isn’t at the exact point of control. That replication function is what XS designates.

The other devices have different roles: a bell provides audible indication, a contact rail indicating relay conveys track-circuit status to the interlocking, and a contact rail alarm bell serves as an audible warning for track faults. None of these replicate an exit push button’s action, so they don’t map to the XS code.