By Jennifer Leah Stong-Michas | Aug 15, 2004
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Money usually decides this debate

One of the great debates that affects contractors—especially those dealing with communications systems—may be the question of shielded twisted pair (STP) or unshielded twisted pair (UTP). There are four main types of cable on the market—coaxial, UTP, STP and fiber optic—but this article will focus on the two that share the most characteristics.

Twisted pair cable, the TP part, refers to the specific type of cable that is generally installed for telephone and Ethernet systems, because the cable has pairs of wire that are twisted to help hinder crosstalk, a common culprit in system inefficiency.

Twist and shout

In both UTP and STP, the individual wires are twisted around one another, creating better conduction. One wire acts as the carrier of the signal itself while the other one (which is grounded) acts as a shock absorber of sorts and blocks interference. This is an important aspect, especially in voice communications where crosstalk can hinder system performance.

The problem is that the twisting itself is not enough to completely protect against crosstalk and interference, which is why shielding exists. The choice of whether to use shielding or not really depends on the situation.


Unshielded twisted pair cable is the less expensive of the two. Though the benefits of STP are valid, many still follow the cost rule and opt for UTP purely for budgetary reasons.

Though the name implies no coating, the truth is that UTP cable does have a protective coating, in the form of an insulating material that enrobes each of the eight (or relevant strand count of) copper wires contained within the cable. The problem is not coating, but shielding, and the truth is that UTP has no shielding, which is sometimes required.

On the bright side, UTP has made amazing strides in recent years and it is actually the faster transmission medium of the two. That helps add to its desirability and popularity. UTP is ranked by categories. Though some of the newer offerings such as Categories 6 and 7 are becoming increasingly popular, Category 5 still reigns supreme since it is fast enough to support most operations and the price is right.


STP takes the concepts behind UTP and goes one step further. In an STP cable, cable pairs (not individual wires) are shielded by a metallic substance, and then all four pairs (once again, this is assuming an eight-strand cable, though there are many other options and strand counts available) are wrapped in yet another metallic protector. This is done with the intention of preventing interference via the usage of three techniques known as shielding, cancellation and wire twisting.

One problem with STP—the one that maintains its reputation of being harder to install—is that if it is not installed and grounded properly, the shielding acts as an antenna and picks up signals. So much for the “cutting down on crosstalk” theory. Because if both ends are not grounded, you have more than crosstalk to deal with—who knows what kind of signals you could wind up receiving in our communication-driven world?

It’s a tie

There really is no clear-cut winner in this scenario. Choice depends on the individual situation and budget. Many feel that STP is best suited for Token Ring networks, and others feel that the shielding associated with STP provides an added benefit of making the cable more secure, so there are some devout proponents of STP out there. STP is still quite popular in Europe.

UTP seems to be everywhere, including just about every building a contractor will ever enter. Because it appears to be dominant in the marketplace, many believe UTP is the winner. UTP does have a larger market share and infrastructure presence, no argument there.

Many use UTP simply because it is already installed in their facility and why bother swapping out all of the cables just to make some moves, adds and changes?

Contractors can be assured that, regardless of the choice the end-user makes, the system will operate properly, as long as everything was installed and tested accurately. EC

STONG-MICHAS, a freelance writer, lives in central Pennsylvania. She can be reached at [email protected]. 


About The Author

Jennifer Leah Stong-Michas is a freelance writer who lives in central Pennsylvania.





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