Wiring for a Third Phone Line



The decision to add a third phone line is a major move for most people.  The phone wiring in most modern homes will support two lines, but often will NOT support three or more lines.  Adding a third line will often require adding to existing wiring or completely replacing or reconfiguring the phone wiring throughout the house.

If the third line is only to be used at one location for a single purpose, it is can be installed as a separate single line.  This is relatively simple.  This would only involve running one cable from the NID and installing one single-line jack.  This process will not be covered here. Installing a third line in this manner severelylimits the service you will obtain from the additional line and I do not recommend it.  If you are going to pay the monthly charges for a third line, you should want to get maximum use from it.  The expense of reconfiguring your wiring will give you considerably more flexibility and should prove to be money well spent.

My advice here is aimed towards homes wired in a "star topology".  I will explain how three lines can be connected in various manners to meet varying requirements.  This will provide you with the most flexibility in determining how to use your expanded phone service.  This advice is only applicable if your home is wired in a "star topology" with station cable with two or more pairs of wire.  I'll also cover how jacks are wired for three lines.

Wiring the Central Hub of the Star

Hint: Time spent planning, diagramming, and documenting the arrangement of the wiring at the hub of your "star" will pay many dividends as you progress with the installation and do future changes.

A 66-block is ideal for use as a central hub for connecting multiple cables in a "star topology".  These blocks come in various sizes and configurations. I recommend using a "split-50" type block.  This type block permits termination of twelve 4-pair cables by using both sides of the block and one cross-connect for each wire using jumper wire.  (Positions 25 and 50 are not used.)  That is what is illustrated at the left below.  The procedures and methods I describe here can be changed considerably so long as the connections made result in connection of the lines to the desired cables.  I will describe my example illustration in depth to assist you in understanding the guiding principles.  If you have more than 11 station cables to terminate on your wiring hub, you can use multiple 66-blocks or you could use a 110-block.  More information about blocks is available at: Wiring Block Techniques and Tips.

Note: Terminating cable and doing cross-connects on a 66-block will require a punchdown tool such as the Paladin 3573 with a 66-blade.  The 66-blade has two reversible ends.  One end punches and cuts the wire being terminated and is used when terminating cables and at the end of a cross-connect wire.  The other end punches the wire without cutting it and is used to punch cross-connect wire that connects at one lug and then goes on to another lug.
66 Block Wiring Cables are terminated on the outside row of punch lugs and cross-connects are made on the inner lugs.  This avoids accidently cutting the cable wires when placing cross-connects.  The "tip" is terminated on the top lug of a pair and the "ring" on the lower lug of a pair.  All pairs of a cable should be terminated, even if they will not be used immediately.  This allows you to add more lines at that location in the future or switch pairs if one is broken somewhere in the cable.  This will also prove useful if you should ever install a key-system, since many systems will require a 4-pair station cable to each jack.  If you use a mix of 4-pair and 2-pair cable, I recommend reserving the two positions after each 2-pair cable.  That permits future expansion of that jack location to 4-pair by either replacing the cable or running a second 2-pair cable.

The first concern is to get the lines from the NID to the 66-block.  This is done with standard phone cable.  I recommend using one cable with at least four pairs.  Two 2-pair cables can also be used if that is already available.  If 2-pair cableis used for the NID connection, be careful to tag and identify which cable is used for line one and two and which for line three, since the wires will be the same color in both cables.  In the example at left, a 4-pair cable from the NID is terminated on pair positions 1-4.

Station cables can be 4-pair or 2-pair cables coming from a jack location.  If the house was originally wired with 2-pair cable, some jack locations will require more pairs than are available in the existing cable.  I recommend running a new 4-pair cable to these locations.  However, you may be able to salvage and reuse some of your existing 2-pair wiring going to locations which will only require access to one or two lines.  Just make sure that they only go to one jack and route them to the hub.  If the cable will not reach the hub you will either have to replace it or splice on an extension.  Splices are a potential failure point, so be careful if you decide to extend a cable.  Where practical, I would recommend replacing all cable with new 4-pair cable.

The example shown is based on the following scenario:
  • Line one is the primary voice line to be used by the adults in the home.

  • Line two is primarily for fax and modem use in the study and is also a secondary voice line for use by the adults in the home.

  • Line three is the primary voice line to be used by a teen-ager in the home and should also be available in the study in case the other two lines are in use.

In the example illustrated, the cables would be used as follows:
  • the 4-pair cables on positions 5-8 and 9-12 would go to rooms requiring access to lines one and two, such as the kitchen and living room

  • the 2-pair cables on positions 13-14 and 17-18 would go to rooms only requiring access to line one, such as the master bedroom and a portable phone for the garage or deck

  • the 4-pair cable terminated on positions 26-29 would go to the study and provide access to all lines

  • the 2-pair cable terminated on positions 30-31 would go to a location such as a family room that requires access to lines one and three

  • the 2-pair cable terminated on positions 34-35 would go to the teen-ager's bedroom and provide only line three

The cross-connects shown connect the lines as described above. Your cables and cross-connects will vary according to your particular requirements.  This example should serve to help you understand the methods used.  By changing the cross-connects, you change which line is connected to a jack and which pair of a jack the line appears on.

For the purpose of the illustration, I have shown the cross-connects for each line in different colors.
  • cross-connects for line one are shown with a green/red pair
  • cross-connects for line two are shown with a black/yellow pair
  • cross-connects for line three are shown with a orange/blue pair
Cross-connects are normally done by phone technicians using a yellow and blue cross-connect wire.  You might find it useful to strip the sheath from a length of unused 4-pair cable and use wire pairs that match the cable coming from the NID.  This makes it fairly easy to determine which line is connected on a pair of lugs.

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Wiring the Jacks for a Three Line Home

Wiring jacks for three line installations is actually very simple.  This is because all changes of which line are connected to the jacks are made at the central hub.

One Jack Two Jacks If a jack is connected via a 2-pair cable, it is probably already wired correctly.  These jacks will provide access to one or two lines depending on the cross-connects made at the central hub.  This is exactly the same as a basic two line jack, so if you are expanding to a third line, you probably won't need to make any changes to these jacks.

Two jack faceplates and four cable pairs are required where access to three lines is required.  These jacks are wired in much the same manner.  Pairs one and two of the cable are connected to the top jack and pairs three and four are connected to the bottom jack.

Take note to check correct connection of tip and ring.  Refer to color code translation if needed.  The pairs three and four are the most likely to cause confusion.  Tip white/green connects to tip green, ring green/white connects to ring red, tip white/brown connects to tip black, and ring brown/white connects to ring yellow.

For some locations, you might want a special jack faceplate which would allow you to place each pair on a separate jack.  These are especially useful when each line is used for a different purpose, such as line one to a phone, line two to a fax, and line three to a modem.

Beyond Three Lines

As you may have noted, when you finish wiring as described above, your home will really be ready for four lines.  Itis a simple matter of placing the desired cross-connects on the 66-block at the star hub and your fourth line would be wired.  Some homes may need four lines.  If you think you need four or more lines, I recommend looking into a key-system to help manage access to your lines and maximize your flexibility.  It should be a relatively painless process to connect a key-system in a home wired with 4-pair cable in a star topology for three or four lines.



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