If a single conductor in a Class A fire alarm system breaks, what happens to the pull stations?

If a single conductor in a Class A fire alarm system breaks, what happens to the pull stations?

• A. All of the pull stations will work
• B. The alarm will sound
• C. Only the pull stations between the panel and the broken wire will work
• D. None of the pull stations will work

Answer: (A)

In a Class A signaling loop, the wiring forms a complete two-wire loop so there’s redundancy in the path back to the panel. If one conductor breaks, the loop around that break is still intact through the remaining path, so current can continue to flow and reach every pull station. That means any pull station can be activated and will send an alarm to the panel, keeping all pull stations operable despite the single open fault. This redundancy is what Class A circuits are designed to provide.

In a Class A signaling loop, the wiring forms a complete two-wire loop so there’s redundancy in the path back to the panel. If one conductor breaks, the loop around that break is still intact through the remaining path, so current can continue to flow and reach every pull station. That means any pull station can be activated and will send an alarm to the panel, keeping all pull stations operable despite the single open fault. This redundancy is what Class A circuits are designed to provide.