Ultimate Guide to Twisted Pair Cable

Author Yana

Date 08/31/2022

Twisted pair cable, coaxial cable and optical fiber cable are three major types of transmission media used in local area networks (LANs). Twisted pair cable is known as low cost, usually used in structured cabling systems within buildings. This article will give a detailed introduction to twisted pair cable, including how it works, the types of twisted pair cable (STP and UTP), CAT grade, and the most frequently asked questions about twisted pair cable.

What is a Twisted Pair Cable?

The twisted pair is the frequently used transmission medium in the generic cabling system project. It consists of two copper cables with insulating protective layers. These two insulated copper wires are twisted together to reduce electromagnetic radiation and resist external interference. The radio wave radiated by one of the wires will be canceled by the radio wave emitted by the other wire.

Twisted Pair Cable Diagram

A twisted pair cabling system consists of one or more copper twisted pairs. Different twisted wires have different twist lengths. Generally, the twist length is between 38.1 to 14cm. The twisting length of adjacent pairs is beyond 12.7cm. Each copper wire is twisted counterclockwise.

Compared with fiber optic cable and other transmission media, twisted pair cable is limited in data transmission speed, transmission distance, and channel width. However, its price is relatively low.

Types of Twisted Pair Cables: UTP and STP

Shielded twisted pair (STP) and unshielded twisted pair (UTP) are two types of twisted pair LAN cables.

UTP vs STP

STP (Shielded Twisted Pair):

Compared with UTP cables, STP cables, such as Cat7 shielded twisted pair cables, have an extra insulation layer in the form of aluminum foil and copper braid mesh.

Advantages of STP:

• The outer layer of aluminum foil helps reduce electromagnetic radiation.

• Support higher data rate and bandwidth than UTP.

Disadvantages of STP:

• Price is relatively higher than UTP.

• Installation is more complex than UTP. Like a coaxial cable, STP must be equipped with specific connectors that support shielding function and professional installation skills.

Application of STP:

High-efficiency information transmission is the field that STP cabling is commonly seen in. Shielded twisted pair provides higher transmission performance than the unshielded twisted pair. It is usually applied in an environment with large interference or harsh electromagnetic requirements.

UTP (Unshielded Twisted Pair):

The unshielded twisted pair is covered by insulating rubber and has no metal shielding layer.

Advantages of UTP:

• Space saving without any shielding layer and small diameter.

• Easy installation with light weight.

• High flexibility, suitable for the structured generic cabling system.

• Low cost.

Disadvantages of UTP:

• UTP link is not as secure as STP link.

• Only accepts distances up to 100 meters. When distances are beyond 100m, it must be installed in sections.

• It has limited bandwidth and data rate.

Application of UTP:

Unshielded twisted pair (UTP) cabling is more commonly used in most local area networks (LANs) because of its cost-effectivity, high flexibility, and easy installation and maintenance advantages. The twisted pair ethernet cable comprises a certain length of twisted pair and RJ45 crystal.

Twisted Pair Cable Category

Cat1: 750 kHz bandwidth, only allows voice transmission, does not support data transmission, mainly used in telephone cables before the 1980s.

Cat2: 1 MHz bandwidth, allows voice transmission and data transmission within 4 Mbps data rate, mainly used in token ring networks.

Cat3: 16 MHz bandwidth, described in EIA/TIA-568, allows voice transmission and data transmission within a 10 Mbps data rate. The typical application is 10BASE-T.

Cat4: 20 MHz bandwidth, 16 Mbps data rate, mainly used in LANs based on the token ring and 10/100BASE-T. Not commonly used.

Cat5: 100 MHz bandwidth, supports 100 Mbps data rate based on increased twisting density and high-quality insulating jacket. The typical application is 100BASE-T and 1000BASE-T, reaching up to 100m.

Cat5e: lower attenuation and crosstalk than Cat5, better signal-to-noise ratio (SNR), and minor delay error, mainly used in 1000BASE-T.

Cat6: 250 MHz bandwidth, supports 10 Gbps data rate, improved performance in crosstalk and return loss, mainly used in 1000BASE-T (reaching up to 100m) and 10GBASE-T (reaching up to 55m).

Cat6a: 500 MHz bandwidth, supports 10 Gbps data rate, improved alien crosstalk, mainly used in 10GBASE-T, reaching up to 100m.

Cat7: 600 MHz bandwidth, improved EMI and crosstalk protection, using GG45 or TERA connectors.

Cat8: 2000 MHz bandwidth, supports a maximum data rate of 40 Gbps within 30 meters. It is compatible with IEEE 802.3bq 25G/40G Ethernet, suitable for short-range high-speed interconnect in server rooms. Cat 8 twisted pair is often seen as a twisted shielded cable pair in the market, known as a Shielded Foil Twisted Pair (S/FTP). Cat 8 SFTP cables have advantages in high speed, industrial-grade anti-interference capability, and low latency features (used in short-distance applications).

Twisted Pair Category	Max. Bandwidth	Max. Data Rate	Max. Length Under Max Rate	Shielded Type	Application
Cat 1	750 kHz	1 Mbps	-	UTP	Telephone cable
Cat 2	1 MHz	4 Mbps	-	UTP	Token ring network
Cat 3	16 MHz	10 Mbps	100m	UTP	Token ring network, 10BASE-T
Cat 4	20 MHz	16 Mbps	100m	UTP	Token ring network
Cat 5	100 MHz	100 Mbps	100m	UTP/STP	100BASE-T, 1000BASE-T
Cat 5e	100 MHz	1 Gbps	100m	UTP	1000BASE-T
Cat 6	250 MHz	10 Gbps	100m	UTP/STP	1000BASE-T, 10GBASE-T(55m)
Cat 6a	500 MHz	10 Gbps	100m	UTP/STP	10GBASE-T
Cat 7	600 MHz	10 Gbps	100m	S/FTP/UTP	10GBASE-T
Cat 8	2000 MH	40 Gbps	30m	S/FTP	25G/40GBASE-T

FAQs About Twisted Pair Cable

Q: Why are wires twisted together in twisted pair cables?

A: Copper wires twisted together help reduce electromagnetic radiation and resist external interference. The twisted way also helps limit interference with adjacent twisted-pair cables; the radio wave radiated by one of the wires will be canceled by the radio wave emitted by the adjacent wire.

Q: What are the two types of twisted pair cables?

A: Unshielded twisted pair (UTP) and Shielded twisted pair (STP). STP has an extra aluminum foil insulation layer, while UTP doesn’t.

Q: What is twisted pair cable used for?

A: Twisted pair cable mainly transmits analog voice information and short-range digital data information. The use cases for twisted pair copper cabling include telephone lines, DSL lines, and local area networks (LANs)

Q: Which connector uses an unshielded twisted pair (UTP) cable?

A: RJ45 connector is the standard connector for unshielded twisted pair cabling.

Q: What is shielded twisted pair cable used for?

A: Shielded twisted pair cable has an extra insulation layer to reduce crosstalk and electromagnetic interference (EMI). It is usually used in environments with large interference or harsh electromagnetic requirements.