Which of the following describes Class A, Class N, and Class X circuits?

• A. They are types of circuit classifications that must be separated by a minimum distance when run vertically.
• B. They are weatherproofing standards.
• C. They are building occupancy categories.
• D. They are color-coding for cables.

Answer: (A)

These circuit classifications tell you how to treat fire alarm signaling wires in a building to keep the system reliable. Class A, Class N, and Class X specify different requirements for how those circuits are routed and protected, including a rule that they must be kept a minimum distance apart when they run vertically through shafts or risers. The idea behind this separation is to limit the chance that a fault, damage, or interference in one circuit will affect others and to help ensure that life-safety signaling remains intact across floors. Weatherproofing, occupancy categories, or simple color-coding describe other, unrelated aspects and aren’t about how circuits are classified or routed for reliable fire alarm operation.