Interestingly ...
UTP (Unshielded Twisted Pair) and
STP (Shielded Twisted Pair) cables terminate in
almost-identical connectors. However, the wiring mechanism (the protocol that dictates how many pins of the plug will be used, which wires will carry data in which direction, and other similar specifications) is different in the two.
While UTP cables employ
RJ-45 wiring, STP cables generally employ
RJ-48 wiring, although it is possible to wire them according to RJ-45 standards as well.
In the field of telecommunication, wiring and cabling are primary concerns, as only by making use of the most suited cables can one successfully implement a network of any architecture, which has a satisfactory throughput yield.
It can be surmised by someone with even the most basic knowledge of electrical systems, that an electrical pulse traveling a distance over a plain copper wire will not reach the other end with the same signal strength. Factors like signal attenuation and external interference contribute to the loss of its signal power. Since time immemorial, engineers have been trying to establish communication networks of acceptable standards with minimum losses, and for this, they have been experimenting with different types and various combinations of electrical cables.
After years of research and implementation, it was concluded that an electrical signal traveling through a cable that contains pairs of twisted wires is less susceptible to electromagnetic influence, also known as
crosstalk, than one that travels on a different kind of cable. Cables having such twisted pairs of wires come in two variants namely,
Shielded Twisted Pair (STP) cables and
Unshielded Twisted Pair (UTP) cables. We have looked into both these types of cables in great depth in order to compare them with each other.
Shielded Twisted Pair Cables
Structure
• Like in all varieties of twisted pair cables, inside an STP cable, there are a number of pairs of individually insulated (with rubber) copper wires, where the wires in each pair are twisted around each other.
• However, the factor that differentiates STP cables from other cables is the presence of protective aluminum casing or shielding.
• The role of this protective shielding in the cable is to attract all external signal influences to itself, and then neutralize them (similar to the analogy of a lightning conductor). Hence, the grounding aspect of STP cables is of prime importance.
• Three types of STP cables exist:
Foiled Twisted Pair Cables,
Screened Twisted Pair Cables, and
Screened Shielded Twisted Pair Cables.
♦ In
Foiled Twisted Pair Cables, aluminum foil shielding is present only around an individual pair of twisted wires.
♦ In
Screened Twisted Pair Cables, all the twisted pairs collectively are encased in a protective aluminum sheath.
♦ In Screened Shielded Twisted Pair Cables, both individual twisted wire pairs as well as the entire braid are protected by shielding, and hence, they are the bulkiest of the three types of STP cables.
Pros and Cons
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The protective casing/shielding of STP cables works in connection with the other crosstalk-eliminating techniques implemented in Twisted Pair cables, giving it a performance edge over other types like UTP and coaxial cables.
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Properly installed STP cables are the most secure of all.
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However, the operation of STP cables is not that simple. First of all, they are bulky, as well as fragile. They need to be correctly installed and then regularly maintained, taking into account physical factors like their bending radius and maximum tension, otherwise they could easily get damaged.
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They are costlier than other types of cables, and additionally, the cost of their installation and maintenance is high.
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STP cables need to be properly grounded. If this is not taken care of, the shielding will have the opposite effect; rather than eliminating crosstalk, the cable will start attracting stray signals and interference.
Applications
• Due to their bulky, yet fragile nature, and also owing to their need for proper installation and regular maintenance, STP cables are best suited for an industrial environment.
• They are suitable for use in Token Ring-type networks.
• Their use is quite widespread in Europe, and they are commonly employed in T1/E1 (Internet-leased) lines.
Unshielded Twisted Pair Cables
Structure
• As the name suggests, UTP cables are 'unshielded', or the inherent twisted wire pairs are not protected by shielding.
• The function of crosstalk elimination is implemented in UTP cables mainly by the twists in the pair of wires. Out of the two wires that are twisted, one carries the signal, while the other has the ability to absorb interference.
• The density (or rate) of twists in a given pair of wires, the number of copper wire strands that make up one wire, and other similar factors, which vary with the category of wire, all contribute to the wire's capability to block interfering signals.
• There are many different categories of UTP cables; however,
Cat 5,
Cat 5e, and
Cat 6 are most commonly used today mainly for Ethernet connection, as they have sufficient data rates.
♦ Cat 5 UTP Cables have a maximum data transfer rate of 100 Mbps, and hence, are suited for use with Ethernet (10 Mbps), Fast Ethernet (100 Mbps), and Token Ring-type networks having up to 16 Mbps speed.
♦ Cat 5e UTP Cables have a maximum data transfer rate of 1000 Mbps, and hence, they are suited for use with Fast Ethernet, as well as Gigabit Ethernet.
♦ Cat 6 UTP Cables also have a maximum data transfer rate of 1000 Mbps, and were originally designed exclusively for use with Gigabit Ethernet. They differ from Cat 5 UTP cables in terms of internal structure; they are less susceptible to interference.
Pros and Cons
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Since these cables are inexpensive, less bulky, perform satisfactorily when used to provide basic connectivity, are easy to install, and also require less maintenance, they are very popular.
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Various categories of UTP cables are available, which have different specifications, including data speed. UTP cables have the ability to match STP cables' data transmission rates.
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In the absence of casing, twisted pairs alone are not as capable of blocking out crosstalk, and hence, UTP cables depend on other techniques of signal balancing, including the use of devices like filters and baluns.
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Due to the fact that they are susceptible to noise, they have limited applications.
Applications
• In a domestic or an office environment, UTP cables are ideal.
• They are well-suited for networks having a Star topology, as well as Token Ring-type networks.
• UTP cables are mostly used in Ethernet (LAN) network connections.
Since both STP and UTP cables have merits as well as demerits, the conclusion that we drew from our analysis is that although
neither of the two should be considered as the ultimate, universal standard, each of them is perfectly optimized to work with the applications it is most commonly utilized for. Cables are comparable to the building blocks of a telecommunication system, and hence, to ensure maximum efficiency, one should employ situation-appropriate cabling while designing any network.
