ZX maps to which device?

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

Answer: (A)

In signaling diagrams, codes like ZX are used to quickly identify specific devices without long descriptions. Knowing what ZX stands for lets you trace circuits and locate equipment efficiently during testing.

ZX corresponds to the contact rail alarm bell. This device is wired to alert personnel when there’s a fault related to the contact rail or the associated track circuit, typically by sounding an audible alarm nearby. It’s a specialized alert device rather than a general bell or a relay, which is why the exact term “contact rail alarm bell” is used.

The other options don’t fit this code because they refer to different equipment: an exit push button stick repeater relay is a relay for repeating an input from an exit button, a contact rail indicating relay serves as an indicator relay for rail status, and a plain bell would be a general bell rather than the specific alarm bell linked to the rail fault condition.