How to Use the End of Line Resistance in Intrusion Alarm Systems

Written by mike aguilar
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How to Use the End of Line Resistance in Intrusion Alarm Systems
Alarm system access control panel (Thinkstock Images/Comstock/Getty Images)

Installing an intrusion detection alarm system is a great way to be able to feel safer and more secure while in your own home. Many insurance companies will also give significant discounts to homeowners and renters who install alarm systems. The main control panel detects intrusion when a circuit is either opened or closed. Opening or closing a door will normally cause a magnetic switch to open, telling the system to initiate an alarm. Breaking glass usually closes a circuit, again, telling the control panel to initiate an alarm condition. An end of line resistor allows a panel to monitor a circuit and warn you if the wire breaks.

Skill level:

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Things you need

  • Wire cutters
  • Wire strippers
  • Crimpers
  • Crimp connectors
  • Resistors
  • Wire
  • Control panel
  • Electrical tape

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  1. 1

    Locate and install the main control panel and access control keypad. The keypad should go near a door, and the control panel should be somewhat difficult to access.

  2. 2

    Route the wires to the various locations that will be controlled. Be sure to avoid sources of heat and pinching to protect the wires. Make sure you label each wire at both ends to signify where it goes (front door, rear door, master bedroom east window, etc.)

  3. 3

    Install intrusion detection switches at all controlled locations, as well as glass breakage detectors near accessible windows.

  4. 4

    Read the installation manual thoroughly to determine end of line resistance values for each protected zone. A zone is an area being protected. See previous list.

  5. 5

    Cut and strip the wire at each location, leaving enough length on the wire to give it some slack and keep it from binding.

  6. 6

    Connect the two contact/switch/device leads individually to one of the conductors in the wire. Door and window switches/contacts will usually have two leads. Glass breakage detectors will usually have four leads: power, ground and the two switch legs. Make the wiring connections by twisting one lead to one conductor of the wire and the other lead to the second conductor.

  7. 7

    Trim the resistor leads to approximately 1/2 inch length and twist one set of wires to one lead and the other set to the other lead.

  8. 8

    Insert the two twisted sets of leads and wire into crimp connectors and firmly crimp the connectors. Tug lightly on the wires and leads to make sure you have a good connection.

  9. 9

    Wrap the wire connections with electrical tape to keep them from shorting out.

Tips and warnings

  • Most panels are different. Make sure you carefully read the installation manual to be sure you use the right resistor values.
  • Any unused zones will have to have a resistor jumpered across the control panel contacts to prevent false alarms.
  • Connect the panel ends of the wires after all device end connections have been made and connect power and ground last to prevent shock and unit damage.

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