EOL End of Line Resistors

EOL End of Line Resistors

Security systems and fire alarm panels use end of line resistors in order to supervise the alarm/fire zone.  This means the alarm/fire panel can detect a problem like a short circuit where someone may have tampered with the zone or lets say a nail through drywall has caused a short.  EOL resistors can be used with "normally open" or "normally closed" zones.  Check the panel manufacturer's wiring diagram and eol resistor specifications as applicable.
  1. Without the EOL resistor the zone may always show as secure even if the wiring is shorted.
  2. End of line resistors ONLY work effectively if they are installed at the end of the circuit where the last device on the circuit is installed. 
  3. The EOL resistor must be installed at the end of line as it only "protects" from where it is installed back to the panel.
  4. If the EOL resistor is installed at the alarm/fire panel it will not do its job.

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