End-of-Line Resistor Chart
Typical end-of-line (EOL) supervision resistor values by fire alarm panel. There is no universal value — it varies by manufacturer AND by circuit type within a brand, and using the wrong value can void the panel's listing. These are planning references only; always confirm against the specific panel's installation manual.
Typical EOL resistor by panel
| Manufacturer | Typical EOL | Circuit | Note |
|---|---|---|---|
| Fire-Lite / Notifier | 4.7 kΩ | NAC (notification) | Part 4.7K-BP; also common for System Sensor NAC modules |
| Fire-Lite / Notifier | 47 kΩ | Conventional IDC (initiating) | Parts ELR-47K / REL-47K — do not confuse with the 4.7 kΩ NAC value |
| Silent Knight (Honeywell) | 4.7 kΩ | Varies by circuit | Verify per panel |
| Potter | 5.1 kΩ | Varies by circuit | Potter EOLR — 5.1 kΩ, not 5.6 kΩ |
| Edwards / EST | 4.7, 10, or 15 kΩ | Depends on panel & circuit | Parts EOL-4.7 / EOL-10 / EOL-15 |
| Simplex (Johnson Controls) | Varies — by part # | Circuit-specific | No single universal value; confirm the part number |
The two traps
Two mistakes cause most EOL problems. The first is confusing circuit types: within the same brand, the notification (NAC) resistor and the conventional initiating (IDC) resistor are usually different — 4.7 kΩ versus 47 kΩ on Fire-Lite and Notifier, an easy transposition on a busy job. The second is substituting a value or part the listing does not call out; the resistor is part of the listed system, and a mismatched one can void the listing even when the panel reads "normal."
Addressable systems increasingly replace the physical resistor with an addressable end-of-line module or electronic supervision, but conventional NAC and IDC circuits still rely on the resistor at the physical end of the run — not at the panel, where it would supervise nothing.
Common questions
What is the end-of-line resistor value for a fire alarm?
It depends on the panel and the circuit type — there is no universal value. The most common value for a notification (NAC) circuit is 4.7 kΩ, but the same brand often uses a very different value on a conventional initiating (IDC) circuit: Fire-Lite and Notifier use 4.7 kΩ on NACs but 47 kΩ on conventional IDCs. Always read the value off the panel's installation manual.
Why does the end-of-line resistor matter?
The EOL resistor lets the panel supervise the wiring: a small current flows through it continuously, so a break in the circuit (open) or a short is detected as a change in that current and reported as a trouble. Without the correct resistor at the physical end of the run, the panel cannot tell a healthy circuit from a damaged one.
Can I use any resistor of the right value?
No. Using a different value — or even a different part than the listing specifies — can void the panel’s UL listing even if the circuit appears to supervise correctly. The resistor is part of the listed system, so match the manufacturer’s specified value and part for that exact circuit.
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