Installing the DSL Splitter Near the NID


In the diagrams on this page,
  • pair 1 (wht/blu) = "voice" connections for line one
  • pair 2 (wht/org) = "voice" connections for line two (if present)
  • pair 3 (wht/grn) = DSL data connections
  • pair 4 (wht/brn) = line connection from the NID to the splitter
Where possible, I would recommend actually using the pairs shown for the purposes indicated.   That should minimize the need for rewiring jacks to complete your DSL installation and will make it as simple as possible if it is necessary to remove DSL service in the future.

Where "DSL" appears on this page, it always refers to ADSL.


If your DSL service provider installs a splitter in or near your NID, they will probably also reroute the cable going to your telephone jacks to the "voice" terminals of the splitter so that telephone service will not be interrupted.   If you request "inside wiring", they may also complete the DSL data connection (for an additional charge no doubt).   Unless there is an existing CAT3 (or higher) cable available for the DSL data connection, if you are paying for "inside wiring" they should install a new cable from the splitter to the DSL data jack.   Normally, you are at least responsible for running the cable to establish the DSL data connection and usually you'll also be responsible for the installation of the splitter.

Note:  If you have an alarm system, special factors need to be considered while planning for your DSL splitter installation.   Even if you have a star topology, you may find it preferable to use a splitter located near the NID, so that you only need to make minor changes to the connections to the RJ 31X jack.  Refer to "Installing A DSL Splitter With An Alarm System".

Ring, Bus, or Hybrid Topology

If you have a ring, bus, or hybrid topology, it is probably most practical to locate the splitter near the NID and simply run a new cable from the splitter to the DSL modem location.   You can use a splitter in a separate exterior enclosure or you can use a less expensive splitter without an exterior enclosure located inside the house at a protected location where the cable coming from the NID can be accessed before it goes to any jacks.


Identify a location where you can access the cable coming from the NID before it goes to any jacks (before the RJ 31X if you have an alarm system).   If you do not have an alarm system and your existing cable is CAT3 (or higher), determine if there are spare pairs available in the cable.   If you only have one or two phone lines, you will probably find that the pair 3 (wht/grn) and pair 4 (wht/brn) are both unused.   If you can place your DSL data jack at the same location as an existing phone jack, then you can use one of the spare pairs for your DSL data connection and avoid pulling in a separate cable.   If you have "JK" quad cable, if there is not a spare pair available in your CAT3 (or higher) cable, or if you don't wish to locate your DSL data jack at the same location as an existing telephone jack, you'll need to run a new cable for the DSL data connection.   Identify a path where you can route a new cable for the DSL data from the location where you plan to locate the DSL modem/router.   If you're using an indoor splitter, make sure the splitter location will provide protection from weather and physical damage.   Install the DSL data cable first so that if you have difficulty finding a path for the cable you'll have the option of changing where you planned to locate the splitter. Then install the jack for DSL data and connect the cable.   If there is slack in the cable coming from the NID, you may be able to cut it where the splitter will be located and connect the end coming from the NID to the "line" terminals of the splitter and the end going towards the jacks to the "voice" terminals of the splitter.   If there isn't enough slack to do that, install a new cable from the NID to the splitter location and pull the excess cable going to the jacks back from the NID to the splitter location. Mount the splitter securely and connect your cables.   Make sure that all of your connections are secure and that you don't have any shorts.   Refer to the information provided by your DSL service provider to install and configure your DSL modem or router.   You should then be ready to begin using your DSL service.

If you have two (or more) telephone lines, you may have the option of having your DSL service placed on either of them. Of course some telephone companies and/or DSL service providers may insist that DSL be provided on your "primary billing number", which is normally what most people refer to as line one (their primary phone number). If you really want your DSL on line two but are told that is has to be on you "primary billing number", perhaps the phone company can change your "primary billing number" to the number on line two. That limitation is administrative and not technical, so there should be a way to adjust the records so that you can get what you really want. Given an option, some people have DSL service placed on line one with the thought that they may have the second line disconnected in the future. Other people firmly plan to keep the second line and have DSL service place on line two with the thought that they don't want any DSL related problems to impact their primary phone line.

If you have two telephone lines and your splitter will be near but not in your NID, the easiest cable arrangement is to route the cable going into the house to the splitter as described above. The non-DSL line can then be connected using a pair in the cable from the NID to the splitter location spliced to a pair in the cable going into the house. Crimp splices are ideal for making such a splice as shown in these diagrams.

Star Topology


Other than where the DSL data cable terminates, the process of connecting a splitter near the NID to a star topology is not significantly different than connecting to a ring, bus, or hybrid topology.   If you have a star topology and it is at all practical, route the DSL data cable to the hub/junction.   This will preserve your star topology and ensure maximum flexibility for any future change in requirements.   You can then cross-connect the DSL service either to an existing cable to the DSL modem/router location or to a new cable installed for that purpose. If an existing CAT3 (or higher) cable at the desired modem/router location has a spare pair (e.g. pair 3 - wht/grn), you can use that pair for DSL data instead of running a new separate cable.   If the distances and available cable path make it significantly less difficult, you could install a cable direct from the splitter to the modem/router location without going through the hub/junction, but you'll lose some flexibility for future changes.

If you have a star topology, you also have several other options for the location and type of splitter to install.   You could locate the splitter at the hub/junction point or you could locate the splitter near the modem/router.   Either of these options allow you to use a less expensive splitter without an exterior enclosure.



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