Which statement best describes the role of the end-of-line resistor in a fire alarm loop?

Which statement best describes the role of the end-of-line resistor in a fire alarm loop?

• A. Provides power to loops
• B. Reduces voltage to the detectors
• C. Supervises the circuit
• D. Helps maintain steady loop impedance

Answer: (C)

Supervision of the circuit is what the end-of-line resistor provides. Placed at the far end of the fire alarm loop, it gives the control panel a defined resistance so the loop can be continuously monitored for faults. When the loop is intact, the panel sees the expected impedance; if a wire opens or a short occurs, the impedance changes and the panel can trigger a fault or alarm. This makes the system reliably detect wiring or device failures. It isn’t there to power the loop or to drop voltage to detectors, and while it helps define the loop’s impedance, its primary role is to enable circuit supervision.

Supervision of the circuit is what the end-of-line resistor provides. Placed at the far end of the fire alarm loop, it gives the control panel a defined resistance so the loop can be continuously monitored for faults. When the loop is intact, the panel sees the expected impedance; if a wire opens or a short occurs, the impedance changes and the panel can trigger a fault or alarm. This makes the system reliably detect wiring or device failures. It isn’t there to power the loop or to drop voltage to detectors, and while it helps define the loop’s impedance, its primary role is to enable circuit supervision.