written by: Jesma•edited by: Lamar Stonecypher•updated: 6/11/2009
Continuing our discussion on various types of network cabling, we take a closer look at Twisted Pair cabling, its design, purpose, and various specifications and standards.
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Twisted Pair Cables
In modern home and office network environments, Twisted Pair cabling is the type that is most commonly seen. Interestingly enough, though, its proper name is not what we most often use to refer to it. Twisted Pair cabling is more popularly referred to as Ethernet cable, Internet cable, Network cable, and by we techies, Cat 5. Regardless of what semi-accurate name you choose to give it, Twisted Pair cabling is, quite simply, your standard (usually) gray cable that you use to connect your cable/dsl modem/router to your computer. Sometimes it is also found in white, blue, and yellow. Still not sure what I'm talking about? Here's a picture.
Your average UTP cable has pretty much zero resistance to interference, be it Electromagnetic Interference (EMI) or Radio Frequency Interference (RFI). This can cause it to be highly unreliable in areas where this type of interference might run rampant. To counter this problem, we use STP cables. STP cabling uses an outer shielding around the twisted wires that sort of resembles tin foil. The end connectors also have a metal casing where they merge with the cable. STP is considerably more expensive than UTP, so use of it is limited to only places where it is absolutely necessary. It typically also needs to be purchased in set manufactured lengths as it is much more difficult to cut and attach connectors to.
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Twisted Pair Categories
At the outset of this article I mentioned that we "techies" tend to refer to this type of cable as Cat 5. The reason for this is that the most common type of this cable is known as Category 5. While Twisted Pair encompasses the entire body of network cables that uses pairs of wires twisted around eachother, Cat 5 refers to a specific type that conforms to a set of standards, and that is incredibly popular in modern networks. There are various types besides just Cat 5, so lets talk about them briefly. Unless otherwise noted, all Twisted Pair cables mentioned here are capable of transmitting a full 100 meters in a single segment.
Category 3 - Category 3 is one of the earlier types of Twisted Pair cabling, and was used fairly extensively until faster speed Cat cables came along. Cat 3 supports a maximum data transmission rate of 10 megabits per second (Mbps), which in its time was still pretty fast. Its speed still supports use in telephone and VoIP systems.
Category 5 & Cat 5e - The original Category 5 was briefly on the scene as a replacement to Cat 3, offering a speed boost up to 100Mbps. A similar revised standard was released a short time after, called Cat 5e. Cat 5e has replaced the original Cat 5 alltogether, and supports speeds of 100Mbps and 1000Mbps (1Gbps or Gigabit).
Category 6 and Cat 6a - Category 6 TP cable isn't incredibly common, but is designed for Gigabit networks and has strict standards in regards to limiting crosstalk and interference. It can also support 10Gbps speeds but is subject to segment length restrictions under the normal 100 meters. The revised 6a standard is more suited for 10Gbps speeds, and will run over the full 100 meters.
There are many different types of network cables, like Coax, Twisted Pair, and Fiberoptic. Then, those broad types are further divided down into numerous specifications and standards. We seek to make sense of all of these different types and their intended uses.