Get it Twisted: Twisted Pair vs. Non-Twisted Pair Cables

How should I appeal to you, the reader?  Do I get very technical and industry focused and make this article geared towards “engineers” or should I swing this article towards “philosophers”.  Depending on the topic, one may be more suited than the other.  Instead, I decided to write this blog for the “artist”, which both can be considered.

Twisted Pairs: “For the Artist”

Cables are an essential component in communication systems.  They are a vital form of transmission media used all over the world.  One type of cable used across multiple industries is multi-conductor cable.  It is a cable that has a minimum number of 2 insulated copper conductors, whose overall construction may vary depending on the application of interest.  Another form of multi-conductor cable is called multi-pair.  While they both can be considered multi-conductor cables, the main difference between these cables is their conductor construction.  While the multi-conductor cable consists of multiple cores, the multi-paired cable (a.k.a.  twisted paired cables) conductors are twisted into pairs.  Both cables are sometimes referred to as ‘data cables’ or ‘electronic cables’.  These names are due to the applications these cables are typically used for.  Some of these applications include data transmission systems, communication systems, audio systems, power transmissions, and many others.

Some may ask, what is the point in twisting the conductors?  Well, I will tell you the point and that relates to functionality.  Twisted pair cabling is used for most modern Ethernet networks, amongst other things.  A pair of wires are twisted and forms a circuit that transmits data.  When it comes to data communications, bandwidth is a major factor as we all know. 

There are different factors that can affect a cables performance such as noise and other signal interferences (EMI, RFI, ESI).  One of those factors involves magnetism.  We all know electricity creates magnetism.  When a high frequency signal is transmitted along a wire, it generates a magnetic field that can induce a signal on an adjacent wire within the cable.  This induced signal is called “cross-talk”, a form of electromagnetic interference.  Just imagine if you were on your cellphone having a conversation and you can hear another conversation taking place out of the blue.  You would have a hard time having that conversation so much so that you may end it.  Picture todays transmissions doing that.  A lot of data would not be sent.

With today’s growing complexity of control and communication systems, coupled with the increase in distances that signals must travel, the frequency of electrical interference related failures has increased as well.  To minimize electromagnetic interference and resist external interference, twisting the wires is necessary.  By twisting the wires, some part of the noise signals goes in one direction (sending) while the other part goes in the opposite direction (receiving).  This twisting helps dampen the magnetic effect on the wires and thus the external waves cancel out due to the different twists.  This also helps reduce interference with adjacent twisted pairs (crosstalk).   The degree of twists corresponds to the category level as well.  A Category 6 cable designed for gigabit networking has tighter twists than a Category 3 (10 Mbps) Ethernet cable.

There are two types of twisted pair cable that exist, unshielded twisted pair (UTP) and shielded twisted pair (STP).

UTP Cables

In UTP cable, each of the individual copper wires are covered by insulating material and then the wires in each pair are twisted around each other.  This cable relies solely on the cancellation effect produced by the twisted wire pairs to reduce signal degradation produced by RFI (radio frequency interference) and EMI (electromagnetic interference).  The number of twists also aids in reducing crosstalk between the pairs.  The more twists, the more reduction of EMI between the pairs.  This is the main type of wiring used for telephones and very common in computer networking, especially as patch cables due to its high flexibility.  There are some advantages of using UTP cable.  One is its small size, which is beneficial during installation, due to having a small external diameter, this cable does not fill up wiring ducts as fast as bulkier cables.  In addition to being easier to install, this cable is less expensive than other types of networking media.  UTP cable is popular due to its ability to be used with most major networking structures.

There are also some disadvantages of using UTP cable.  UTP cable is more susceptible to electrical noise and interference than some other types of media and the signal boost distance is less than it is for coaxial or fiber-optic cables.

STP Cables

In STP cables, each pair of wires are wrapped in a metallic foil, usually aluminum.  This cable combines the cancellation and wire twisting techniques with that of shielding.  After wrapping the pairs, the overall wires are wrapped again with a metallic braid or foil.  Particularly in Ethernet network installations, STP cabling is used to reduce electrical noise within the cable (crosstalk) and from external interferences like EMI and RFI.  STP cable can also help to provide grounding.  STP cable prevents signal interference better than UTP cable.  However, STP cable is more expensive and more difficult to install than UTP cable.  Also, this cable must be grounded properly because if it is not, the shielding can act like an antenna and pick up additional unwanted signals.  Due to these factors, and the fact that most buildings are already wired with UTP, it is used less when wiring Ethernet networks.

In a nutshell, multi-conductor cables are geared toward general purpose use with a high performance in power distribution applications.   Since multi-paired cables permit higher data speeds, they excel at tasks related data transmission.  If you are looking to wire up your automation facility, office or even home, MISUMI carries many options for your multi-conductor and multi-pair cabling needs.

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