Most everyone knows what coaxial cables are, as they are used in almost every home for cable television connections.
These data cables are also popular in local area networks (LAN) because they are highly resistant to signal interference. This resistance is due to the cable construction, which includes a round copper conductor and then three layers of insulation and shielding which prevents crosstalk from motors, lighting and other sources of EMI. This design also gives coax cables the ability to support longer cable lengths between two devices.
However, coax cables can be difficult to install, so sometimes twisted pair cabling may be called for, in which two conductors are twisted together. This twisting helps to eliminate EMI and crosstalk, especially in the more common unshielded, twisted pair designs. The biggest advantage to twisted pair cabling is in installation, as it is often thinner than coax. However, because they are thinner, they can not support very long runs like coax cables.
These tightly twisted designs cost less than coaxial cables and provide high data transmission rates. They connect with the RJ45 connector, which looks similar to a telephone jack but is designed for twisted pair pins.
In environments with extreme interference, especially those running motors, shielded twisted pair cabling should be used. Like coax, it supports greater cable lengths, and can be shielded in a variety of ways—with a foil shield on each conductor, a foil or braid inside the jacket or a combination of individual conductor and jacket shielding.
In the end, twisted pair cabling is better suited when cost and installation are an issue and if EMI and crosstalk are not too much of a problem. However, they do not provide electrostatic shielding and do not work as well as coaxial cables at higher frequencies, so having a full understanding of your application is necessary before selecting these data cables.