Michigan VOIP

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), including things that will make you shudder, like seeing wires from completely different pairs used to form a circuit. 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.