Where is an end-of-line resistor typically installed in an initiating-device circuit?

Where is an end-of-line resistor typically installed in an initiating-device circuit?

• A. At the far end
• B. Near the power supply
• C. In the middle of the circuit
• D. At the FACP

Answer: (A)

End-of-line supervision uses a resistor placed at the far end of the initiating-device loop so the control panel can monitor the entire circuit. With the resistor at the far end, the panel expects a specific resistance when the loop is intact all the way from the panel through every device to the far end. If any fault occurs along the wiring or a device opens or shorts, that change shows up as a deviation from the expected resistance, triggering a fault or alarm as designed. Putting the resistor near the power supply or in the middle could mask faults farther down the line, because the panel would still see the expected value for the portion of the loop up to the resistor. Placing it at the FACP would remove the end-of-line reference entirely, defeating supervision of the entire loop.

End-of-line supervision uses a resistor placed at the far end of the initiating-device loop so the control panel can monitor the entire circuit. With the resistor at the far end, the panel expects a specific resistance when the loop is intact all the way from the panel through every device to the far end. If any fault occurs along the wiring or a device opens or shorts, that change shows up as a deviation from the expected resistance, triggering a fault or alarm as designed.

Putting the resistor near the power supply or in the middle could mask faults farther down the line, because the panel would still see the expected value for the portion of the loop up to the resistor. Placing it at the FACP would remove the end-of-line reference entirely, defeating supervision of the entire loop.