How to Use Resistors in Alarms

End-of-line (EOL) resistors help an alarm system monitor itself for system integrity problems including sensor malfunctions. Before EOL resistors became commonplace, security systems operated with a simplistic electrical circuit featuring a closed or open circuit, providing either full or no voltage to the control panel. Implementing the resistors causes a resistance in the flow of current.



The resistors are installed at the end of the line, in the panel, to most effectively prevent circumvention of the system. A resistor placed mid-wire would not indicate a problem -- such as intruder tampering or accidental puncturing with a screwdriver -- occurring in the length of wire separating the resistor from the panel.

Things You'll Need

• Screwdrivers
• Pliers

Show More

Instructions

1. • 1

     Completely shut off power to the alarm system, if possible. Call the security company and inform them of the maintenance project and that the power will need to be temporarily cut. Switch the power off at the circuit breaker.

   • 2

     Remove the cover of the control panel. Bend the leads of the EOL resistors to a 90-degree angle. Create clockwise loops out of the leads. This ensures they fit into the terminal screw spacing.

   • 3

     Put the looped leads under the terminal screws and tighten the screws. It doesn't matter which wire attaches to which screw as the resistors lack sensitivity to polarity.

   • 4

     Close the panel. Turn on the circuit breaker. Call the alarm company and inform them of the project completion and that the alarm may be armed again.