Twisted Pair Wires

Twisted pair cabling is a type of communications cable in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted balanced pair, a twisted pair reduces electromagnetic radiation from the pair and crosstalk between neighboring pairs and improves rejection of external electromagnetic interference. It was invented by Alexander Graham Bell.

For additional noise immunity, twisted-pair cabling may be shielded.

• STP : Cable with shielding is known as shielded twisted pair (STP)
• UTP : Cable without shielding is known as unshielded twisted pair (UTP).

Twisted-pair cabling was invented by Alexander Graham Bell in 1881. By 1900, the entire American telephone network was either twisted pair or open wire with transposition to guard against interference. Today, most of the millions of kilometers of twisted pairs in the world are outdoor landlines, owned and maintained by telephone companies, used for voice service.

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.

Explanation to Why Twisting ?

For every extension cord or anything that carries electrons through it, there will be a magnetic field enveloping it to some degree. The lower the voltage, the smaller the magnetic field. Ethernet cable is very low voltage in nature, but the voltage is still present, and the twists in the conductor pairs protect the cable from itself.

The twists reverse the polarity of the conductors at each and every twist, and this cancels out differences in their individual electromagnetic fields. The result is electromagnetic balance, and why Ethernet cable is called balanced twisted pair.

Read More : The astute observer will notice that different pairs have different twist rates. This means more twists per inch on some pairs, and less on others. This is by design, and not a defect. Now that one pair is working in harmony at a certain twist rate, it will be susceptible to potential interference with another harmonious pair at the same twist rate. The solution is to vary the twist rates between the pairs that are next to each other inside the cable.