Which class is prohibited for the wiring between the fire alarm control unit and the emergency function control device?

• A. Class A
• B. Class B
• C. Class C
• D. Class D

Answer: (C)

In fire alarm wiring, circuits between the control unit and devices like an emergency function control device must follow defined, recognized classifications that ensure proper supervision and reliability. The approved types for signaling circuits are those that provide fault tolerance: Class A loops keep signaling if a conductor is damaged because the circuit can use alternate paths, while Class B circuits are a simpler, two-wire configuration that returns to the control unit.

There isn’t a recognized Class C for fire alarm signaling in the standard definitions, and using an undefined or nonstandard class would fail to meet supervision and reliability requirements. That’s why wiring between the control unit and the emergency function control device is prohibited if it uses Class C.