Lesson 1.8: Supervising the Line (EOL Resistors)
Lesson 1.8: Supervising the Line (EOL Resistors)
⚡ The Logic (Mermaid)
flowchart LR
CTRL["Controller Input"]
R2["2k2 Resistor
in Series"]
subgraph SEN["Sensor Assembly"]
direction LR
subgraph SENSOR["NC Sensor"]
direction TB
SWITCH["NC Sensor / Contact"]
R1["2k2 Resistor
in Parallel"]
SPACE1[" "]
end
TAMPER["NC Tamper"]
SPACE1 ~~~ TAMPER
end
CTRL -- "Wire" --- SWITCH
SWITCH -- "Wire" --- TAMPER
TAMPER -- "Wire" --- R2
R2 -- "Wire" --- CTRL
SWITCH --- R1
R1 --- SWITCH
style SPACE1 fill:transparent,stroke:transparent,color:transparent!Pasted image 20260521083803.png
with NC Sensor
| Resistance | Meaning |
|---|---|
| 0Ω | Zone fault. Wire shorted - Alarm Activated |
| 2200Ω | Zone secure. |
| 4400Ω | Zone violated. Sensor tripped - Alarm Activated |
| Infinite Ω | Zone tampered with. Wire cut - Alarm Activated |
| with NC Sensor |
| Resistance | Meaning |
|---|---|
| 0Ω | Zone fault. Wire shorted - Alarm Activated |
| 4400Ω | Zone secure. |
| 2200Ω | Zone violated. Sensor tripped - Alarm Activated |
| Infinite Ω | Zone tampered with. Wire cut - Alarm Activated |
Hardware Landmark: Dual EOL Resistors
!300
Above: A typical EOL resistor pack. In Inner Range, we use 2.2k (Red-Red-Red) or 10k resistors to monitor line integrity.
!Pasted image 20260521083242.png
!Pasted image 20260521083312.png
🧠 The Concept
Standard wiring can only tell if a circuit is Open or Closed. If a thief cuts the wire, the system thinks the door is open. By adding End-of-Line (EOL) Resistors, the controller can measure the electrical resistance.
- 2k2 Ohms: Sealed/Healthy.
- 0 Ohms: Short Circuit (Tamper).
- Infinite Ohms: Open Circuit/Cut Wire (Tamper).
🛠️ Hands-on Steps
- Identify Resistance: Inner Range defaults to 2k2 / 2k2 (Dual EOL).
- Placement: Resistors MUST be placed at the Sensor end, not at the controller.
- Testing: Use your multimeter at the controller end of the cable to verify you see ~2.2k ohms when the door is closed.