•  Digital home conversion 101

    One obstacle to replacing traditional phone service with Voice over IP is that for your existing home phone jacks to work, it's necessary to make a change to your inside telephone wiring.

    Fortunately, this change is very easy to make. In some cases it's as simple as removing a plug from a jack. Still, a basic understanding of how telephone wiring works is useful before attempting to make such a switch. Some readers may choose to skip this preliminary information, but if you do that you may be cheating yourself out of acquiring some useful knowledge that will almost certainly come in handy at some point in the future.


    Traditional telephone service is provided over a pair of wires. Virtually all telephone wiring installed in the past 50 years or so contains at least two pairs of wires, but that does not mean that all phone wiring is suitable for carrying two phone lines. In today's telephone wiring, each phone line is put on a pair that consists of a solid colored wire (such as solid blue) twisted together with a white wire. Usually this white wire will have a stripe of the same color as the solid wire of the pair (so you would have a blue wire paired with a white wire with a blue stripe), so that you don't get the white wires mixed up. Occasionally you'll see variations on this (for example, the mostly "solid" wire will have a white stripe in it) but you can usually tell what the pairs are, in part because the wires in each pair are twisted together inside the cable.

    In newer homes Cat 5 wire is almost always used for communications wiring — if not it will probably be at least Cat 3, which uses the same color coding ("Cat" is short for "category", by the way). Cat 5 wire generally has four pairs, while Cat 3 may have a different number of pairs, generally anywhere from three to six.

    The primary pair, or "Line 1", is usually the blue and white (with blue stripe) pair. If there is a "Line 2", it is usually placed on the orange and white (with orange stripe) pair. Line three is on the green pair, and line four on the brown pair (if there is a fifth pair, it will be grey, or to use correct telephone company terminology, "slate"). This color coding scheme for multi-line telephone wiring has been used for years. It is VERY bad practice to split pairs (that is, to use one wire from one of the twisted pairs, and another wire from another of the twisted pairs as a pair). For example, we've seen an online video where they actually told people to use the solid green wire and the solid orange wire to make a pair. That is wrong, wrong, WRONG. We apologize for harping on this, but it boggles the mind that anyone would actually tell people to do this, given the potential for introducing electrical and radio frequency noise, as well as crosstalk into conversations. Keep the twisted pairs together — each line on its own twisted pair!

    The outer jacket of this wiring may be blue, green, grey, beige, white, or occasionally some other color (blue is apparently the most popular outer jacket color for Cat 5 wire these days). The same colors are used for 10/100BaseT computer network cables, although the pairs are utilized differently in that situation. With telephone wiring, particularly if Cat 3 wire was used, the actual number of pairs in a cable may vary, but if standards were followed during the installation, the blue and white (with blue stripe) pair is always the primary phone line.

    In older homes, you may find a whole different scheme, called "quad" wiring, which contains four wires colored red, green, yellow, and black. The primary phone line is normally the red and green wires. Sometimes you will find a second line on the yellow and black wires, but this is not good practice because, in quad cable, the wire pairs are not twisted together, which can (and often does) result in "crosstalk" between the two lines. That is the main reason why "quad" wire is rarely seen in homes newer than a decade or so (in fact, it is a violation of a Federal Communications Commission rule to use any wiring that does not meet at least Cat 3 specifications for new and retrofit telephone wire installations made after July 8, 2000). We do NOT recommend putting two voice lines on quad cable — you might get by with using it for one voice line and one fax line (if you don't mind hearing fax screeches in the background of your voice calls), but it really should never be used for two voice lines. If you have more than one voice line, we strongly recommend replacing the quad wiring with Cat 5 twisted pair wiring, if it is at all possible to do so.

    One other drawback to "quad" wire is that, because the pairs are not twisted, it is much more susceptible to picking up radio-frequency interference (RFI) from nearby transmitters. If you live near a radio station, or even a busy highway where vehicles travel with high-powered transmitters, you may hear interference from these transmitters in your phones. If this is the case, you should definitely consider replacing any "quad" wire with Cat 5 wire (not just Cat 3 — Cat 5 has tighter twists and resists RFI much better, and costs only a bit more).

    To recap, if you only have one phone line in your home, it is probably on the blue and white (with blue stripe) pair, or if you have older wiring, the red and green wires. This assumes that whoever did the telephone wiring in your home followed the standard color codes. It's possible that in your home you find something different (particularly if the previous homeowner did the wiring, or someone actually followed the bad advice in one of those online videos), including things that will make you shudder, like seeing wires from completely different pairs used to form a circuit (the aforementioned split pairs). If this is the case, and you don't know how to fix it yourself, you may require professional assistance to fix things up first.

    Also, should you discover a non-standard type of wire used as telephone wiring, this should be replaced with approved Cat 5 telephone wire. Examples of non-standard wire would include doorbell wire, lamp cord, speaker cable, antenna wire, or any kind of stranded wire (telephone wire is always solid copper, never stranded wire, except for the modular cords used to connect a telephone or telephone device to a wall jack). If the wires do not conform to one of the color code schemes shown above, the wiring is probably not standard phone wire, and should be replaced.

    Some homes built in the first half of the 20th century (or earlier) may have very old phone wiring which uses two or three wires twisted together, usually all with the same dark color insulation and with no outer jacket. It's a judgment call on whether to replace that wiring — if it is still working and the insulation appears to still be in good condition, with no visible damage, and it would be difficult to replace, then you may want to leave it alone for now. However, rubber-coated wire should always be replaced, because 50-year-old rubber insulation cannot be trusted, and is likely to crack and crumble at the slightest touch! If you need to replace old or non-standard wire, you should again seek professional assistance, if you don't know how to do it yourself.