Definition – What does Unshielded Twisted Pair Cable (UTP)mean?
Unshielded twisted pair (UTP) cables are widely used in the computer and telecommunications industry as Ethernet cables and telephone wires.
In an CAT6 UTP Internet Cable Wire, conductors which form a single circuit are twisted around each other in order to cancel out electromagnetic interference (EMI) from external sources. Unshielded means no additional shielding like meshes or aluminum foil, which add bulk, are used. UTP cables are often groups of twisted pairs grouped together with color coded insulators, the number of which depends on the purpose.
An UTP cable is made up of a bundle of twisted pairs. The twisted pairs are small 22- or 24- American Wire Gauge (AWG) sized wires twisted around each other.
Twisted pair cabling is a type of wiring 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, crosstalk between neighboring pairs and improves rejection of external electromagnetic interference. It was invented by Alexander Graham Bell.
In a balanced line operation, the two wires carry equal and opposite signals, and the destination detects the difference between the two. This is known as differential modetransmission. Noise sources introduce signals into the wires by coupling of electric or magnetic fields and tend to couple to both wires equally. The noise thus produces a common-mode signal which is canceled at the receiver when the difference signal is taken.
This method starts to fail when the noise source is close to the signal wires; the closer wire will couple with the noise more strongly and the common-mode rejection of the receiver will fail to eliminate it. This problem is especially apparent in telecommunication cables where pairs in the same cable lie next to each other for many miles. One pair can induce crosstalk in another and it is additive along the length of the cable. Twisting the pairs counters this effect as on each half twist the wire nearest to the noise-source is exchanged.
Providing the interfering source remains uniform, or nearly so, over the distance of a single twist, the induced noise will remain common-mode. Differential signaling also reduces electromagnetic radiation from the cable, along with the associated attenuation allowing for greater distance between exchanges.
The twist rate (also called pitch of the twist, usually defined in twists per meter) makes up part of the specification for a given type of cable. When nearby pairs have equal twist rates, the same conductors of the different pairs may repeatedly lie next to each other, partially undoing the benefits of differential mode. For this reason it is commonly specified that, at least for cables containing small numbers of pairs, the twist rates must differ.
In contrast to shielded or foiled twisted pair (typically F/UTP or S/FTP cable shielding), UTP (unshielded twisted pair) cable is not surrounded by any shielding. UTP is the primary wire type for telephone usage and is very common for computer networking, especially as patch cables or temporary network connections due to the high flexibility of the cables.