An end-of-line resistor is used to ___.

• A. Minimize voltage drop on a fire alarm circuit
• B. Make sure a fire alarm circuit is grounded
• C. Supervise the fire alarm circuit
• D. Ensure the fire alarm circuit will not have a dead short when the alarm is activated

Answer: (D)

The key idea is circuit supervision. An end-of-line resistor is placed at the far end of a fire alarm signaling loop so the control panel has a known reference impedance. With that reference, the panel can reliably tell when the loop is normal, when there’s an open, or when there’s a short fault. By providing this defined end-of-line resistance, the system avoids situations where a fault—like a dead short—could be mistaken for normal signaling or go undetected when the alarm activates. In this sense, the end-of-line resistor helps ensure the circuit won’t behave like a dead short during signaling, because any abnormal condition will be detected and reported. It’s not about grounding the circuit or minimizing voltage drop; its purpose is to supervise and detect faults on the loop, including conditions that could resemble a dead short.