How Do You Install the DSL Alarm Filter on an RJ31X?

Written by eric skramsted
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How Do You Install the DSL Alarm Filter on an RJ31X?
Filter your alarm system for proper operation. (inside the alarm box. image by Kevin Chesson from

With the proliferation of "wired" homes, many homeowners have encountered conflicts between their home security system and DSL line. Alarm systems are analogue devices that operate on the voice band of a phone line. DSL technology operates at a much higher frequency band on that same phone line. The resultant noise can cause communication errors with alarm systems.

Skill level:
Moderately Easy

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  1. 1

    Locate the security alarm box. In most instances, this will be a square box mounted on a wall, with a keyhole latch and a bundle of wires running into it. It should also have some sort of designator on the face of the box, with the type of alarm system or the name of the alarm company.

  2. 2

    Check to see if there is a phone jack mounted outside of, but near, the security panel. In most instances, it will be a square jack mounted on the surface of the wall. There should be a phone cord plugged into it, leading into the security panel. If this is the case, skip the next step.

  3. 3

    Open the security panel if you do not have a phone jack mounted outside the panel. Locate the phone jack inside.

  4. 4

    Unplug the cord from the phone jack. Plug the male end of the DSL filter, which will look like a standard phone cord, into the phone jack.

  5. 5

    Plug the phone cord that feeds the alarm equipment into the female end of the filter.

Tips and warnings

  • RJ31x DSL alarm filters should be available at most computer or electronics stores. Some alarm companies will also carry them and will provide them for you.
  • Make sure that you are using a RJ31x DSL filter made specifically for alarm systems. A standard DSL filter used for telephones will not work. Standard filters block out the high frequency, broadband signal. Since alarm systems are connected to your phone line before the line reaches the rest of your equipment, a standard filter will block your DSL signal from reaching the modem. An RJ31x alarm filter is specially made to block the broadband signal from the alarm system, but pass it on to your modem, allowing both pieces of equipment to operate as designed.
  • If the alarm system is monitored, make sure to call the alarm company beforehand to let them know that you will be disconnecting the line temporarily. This will help you avoid any false reports or dispatches.

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