Though four wires are typically used in U.S. phone cabling, only two are necessary for telecommunication. In the event that a second line is needed, the other two are used. They are also sometimes used to provide power for telephone dial lamps (6 volts AC, as in the Princess phone), or other features.

What cable do I use for phone line?

One of the most common telephone cables is called the coaxial cable. It is called coaxial because it has one physical channel, which is an insulated layer that is a woven shield of copper. This inner layer carries the signal and is surrounded by another physical channel that is created out of a plastic sheath.

Is Cat 5 the same as phone cable?

Network cables are usually thicker and rounder than a telephone cable. Network cables, including Cat5, Cat5e, Cat6, Cat6a, etc., are twisted pair cables for carrying signals in structured cabling for computer networks such as Ethernet. While phone cables are narrower and flat, and are made up of four wires.