Phone wiring

In the past people used quad wire, or POTS wire. This wire is not twisted, is susceptible to interference, and is not suitable for telephone systems with several lines. If you are updating an old system and you encounter this wire, your best option is to replace the old wire with some type of twisted pair wire, such as Cat 3 or Cat 5e, rather than expanding the system with the quad wire in place.Most installers have been using Cat 3 for phones, but Cat 3 is getting harder to find, and the price difference between Cat 3 and Cat 5e has narrowed considerably to around five dollars per thousand feet. Cat 3 is still recommended for phones, but if there's any chance that your phone system may be used for data transmission in the future, an upgrade to Cat 5e would be well-advised.

There are a few installers who use Cat 6 for telephone systems. Unless the phone network may be used as a computer network in the future, this is a strange choice. It is the equivalent of using a speed boat to cross a swimming pool or using a chainsaw to remove a small twig from a bush--it's very unecessary, very expensive, a big hassle for what you're trying to accomplish, but it will work. [via Network Know How]