Unshielded Twisted Pair (UTP)

Unshielded twisted pair (UTP) is a ubiquitous type of copper cabling used in telephone wiring and local area networks (LANs). There are five types of UTP cables -- identified with the prefix CAT, as in category -- each supporting a different amount of bandwidth.

Alternatives to UTP cable include coaxial cable and fiber optic cable. There are benefits and tradeoffs to each type of cabling, but broadly speaking, most enterprises favor UTP cable due to its low cost and ease of installation. 

Content Continues Below

How UTP cables work: Twisted pair design

Inside a UTP cable is up to four twisted pairs of copper wires, enclosed in a protective plastic cover, with the greater number of pairs corresponding to more bandwidth. The two individual wires in a single pair are twisted around each other, and then the pairs are twisted around each other, as well. This is done to reduce crosstalk and electromagnetic interference, each of which can degrade network performance. Each signal on a twisted pair requires both wires.

Twisted pairs are color-coded to make it easy to identify each pair. In North America, one wire in a pair is identified by one of five colors: blue, orange, green, brown or slate (gray). This wire is paired with a wire from a different color group: white, red, black, yellow or violet. Typically, one wire in a pair is solid-colored, and the second is striped with the color of its mate -- e.g., a solid blue wire would be paired with a white-and-blue striped wire -- so they can be easily identified and matched.

UTP color codes

Different uses, such as analog, digital and Ethernet, require different pair multiples.

The twisted-pair design was invented by Alexander Graham Bell in 1881.

Types of UTP cables

The five categories of UTP cable are defined by the TIA/EIA 568 standard:

  • CAT3: Rarely used today, CAT3 is usually deployed in phone lines. It supports 10 Mbps for up to 100 meters.
  • CAT4: Typically used in token ring networks, CAT4 supports 16 Mbps for up to 100 meters.
  • CAT5: Used in Ethernet-based LANs, CAT5 contains two twisted pairs. It supports 100 Mbps for up to 100 meters.
  • CAT5e: Used in Ethernet-based LANs, CAT5e contains four twisted pairs. It supports 1 Gbps for 100 meters.
  • CAT6: Used in Ethernet-based LANs and data center networks, CAT6 contains four tightly wound twisted pairs. It supports 1 Gbps for up to 100 meters and 10 Gbps for up to 50 meters.

The most common connector used with UTP cable is an RJ-45.

Shielded vs. unshielded twisted pair cables

The unshielded in UTP refers to the lack of metallic shielding around the copper wires. By its very nature, the twisted-pair design helps minimize electronic interference by providing balanced signal transmission, making a physical shield unnecessary. In addition, different twist rates -- that is, varying the amount of twists between different pairs -- can also be used to reduce crosstalk. Because these protections come from how the wires are physically laid out, bending or stretching a UTP cable too much can damage the pairs and make interference more likely to occur.

In a shielded twisted pair (STP), the wires are enclosed in a shield that functions as a grounding mechanism. This is done to provide greater protection from electromagnetic interference and radio frequency interference; however, STP cable is more expensive and difficult to install, compared with UTP.

Unshielded twisted pair categories
This was last updated in April 2019

Continue Reading About Unshielded Twisted Pair (UTP)

Dig Deeper on Campus area network

Join the conversation


Send me notifications when other members comment.

Please create a username to comment.

What do you see as the greatest benefits and drawbacks of UTP cable?
I w'd like to more abt this cables, advantages and disadvantages.
Benefits- Cheaper, less expensive. 
Drawback- The only thing I see different with UTP and STP is the metallic coding, and that alone with the benefits that a physical barrier carries sets STP higher up in competition with UTP (copper shielding reduces crosstalk and electromagnetic interference better than UTP), yet STP is more expensive and difficult to install. 
Cat3 UTP is not only used for VF telephony, but for All types of Digital Subscriber Line (DSL) as well, connecting subscriber modems to centrally located DSL Access Modules (DSLAMs). 

Bandwidth, both spectral and digital, decreases with range and are also governed by the condition of the line; balance, external noise, crosstalk, etc. 

However, my company's product, TurboLine, increases both range and digital bandwidth by reducing the line's susceptibility to external noise to nearly zero and at the same time balancing both the signal in and the impedance of the pair. 

The result is a line that is capable of carrying up to 500% more data than a standard telephone wire.  DSL gets a new lease of life.

Inexpensive and easy to install, TurboLine makes any cat 3 line act at least like a cat 5 or 6.

John Fortier.  Celeriss Inc.
if we use Angle single for digital  and we cut the o+os   
The  individual shield (IS ) of the IS+OS  cable can be  cut-off at the point where the insulation is removed  and hence the IS will not be terminated to the TB.
why did u put this on