Twisted-pair cable is the stuff of legends. Developed in the 1970s, it is unlikely that anyone at that time could have imagined the technological, industrial or societal impact it would have. Through the 1980s, the Institute of Electrical and Electronics Engineers (IEEE) published multiple Ethernet standards. But it was not until 1991 that the Electronic Industries Association (EIA), together with the Telecommunications Industry Association (TIA), published TIA/EIA 568, the first standard for telecommunications cabling in commercial buildings. Modern structured cabling was born.
That publication standardized the requirements for Category 3, and it was quickly followed by TIA/EIA Telecommunications Systems Bulletin (TSB) 36, which defined the standards for Category 5 cable with specified transmission performance up to 100 megabits per sec-ond (Mbps).
A data transmission rate of 100 Mbps was considered to be a staggering rate of speed at that time, and most people expected it to meet the technology needs for the foreseeable future. Yet time would demonstrate that copper twisted-pair was only just getting started.
As the age of structured cabling approaches the completion of its second decade, it has repeatedly done the unbelievable, with Cat 6a now supporting 10 gigabits per second.
But as with any legend, myths can enter the popular belief system. ELECTRICAL CONTRACTOR recently spoke with several industry experts, and they identified five commonly held myths about twisted-pair cable.
Myth #1: The death of copper cabling is inevitable and imminent at the hands of fiber optics.
Harbingers of copper’s impending demise have never been hard to find. As a marketing piece from one major fiber optic manufacturer proclaims, “It’s time to get over copper and make the move to fiber optics … . There have been six generations of copper cable in the past 20 years alone—each one designed to address the next wave of bandwidth demand and each one becoming more complex to design around and install. A single generation of multimode optical fiber has outlived, and continues to surpass the bandwidth capability of, every one of those copper designs, not to mention the fact that fiber has gotten easier—not harder—to design with and install.”
All true, but not the whole story.
“Low-voltage twisted-pair cabling is alive and well!” said Greg Niemiera, director of technical support and field services for Mohawk Cable, Leominster, Mass.
“Fifteen years ago, we started hearing that fiber-to-the-desktop was just around the corner,” he said. “But now, that just seems to be get-ting further and further away. The growth of copper has been phenomenal. Data transmissions of gigabit and beyond used [to] only be pos-sible over fiber optics, but now you can do that and more with copper. We used to say that there’s no way that copper could ever do that, and now it’s a reality. What’s next for copper? I don’t know, but we didn’t know before either.”
Niemiera said that copper twisted-pair cabling is more commonly known by installation technicians and information technology (IT) personnel than fiber optics, and it’s more user-friendly because it is more easily terminated. It also does not require the cost of fiber transceivers, which have remained relatively high.
“We are in copper’s greatest days,” Niemiera said. “The fact is that most industries have found that they can do what they need with this tried-and-true technology.”
Myth #2: The death of copper cabling is inevitable and imminent at the hands of wireless.
Dave Hess, a technical manager with Berk-Tek/Nexans Inc., New Holland, Pa., emphatically agreed that copper is here to stay, and one thing it does not need to be worried about is wireless.
“Ethernet is pervasive,” he said. “And now with wireless over a copper network, there are more applications than ever. We just keep making more and better uses of twisted-pair cabling.”
“Wireless, fiber optics and copper all work together to create bigger systems than any one of them could create on its own,” he said. “There-fore, wireless is simply not a long-term threat to copper because it can’t function without it. There’s still wire in wireless.”
Hess cited the Internet as an example; many people access the Internet wirelessly.
“Every Internet connection has a layer of Ethernet at each end. The only thing wireless does is eliminate the patchcord, which is just the last tether. Everything else stays the same.”
He also pointed to the cell phone industry.
“One of the biggest applications for copper cable today is in wireless towers,” he said. “They are full of big, expensive cables. And with the convergence of cell phone and Wi-Fi technologies, that just means more and more twisted-pair cable. It’s nonsense to believe that wireless will be the end of twisted-pair.”
Myth #3: Installer certification isn’t really necessary. Twisted-pair is so easy to use that it requires only minimal (or no) training to install.
Of course, a great strength of twisted-pair cable is that it is easy to understand and install and requires comparatively less in technical skills, training and expensive equipment than some other telecommunications media. Nonetheless, installers and technicians still must be well trained.
“Installers need to know how to do field terminations and perform tests if they are going to get systems up to their required stan-dards with margins, especially with the higher performance cables,” said Paul Kish, director of systems and standards, Belden, Rich-mond, Ind.
“And not only do they need training on twisted-pair in general,” he said, “but they also need manufacturer-specific training. While it’s true that cable systems are sometimes more installer-friendly than in the past when moving from manufacturer to manufacturer, differ-ent companies still have different ways that their devices must be terminated.”
“Contractors will do themselves and their clients a disservice if they do not make sure that their field techs are properly trained and cer-tified on each manufacturer’s products that they install,” Kish said.
“If a contractor sends untrained or unprepared people to a job site, that will just cost more in the long run,” said Harley Lang, mar-keting manager, Fluke Networks.
Myth #4: Shielded or screened twisted-pair is always a better solution than unshielded twisted-pair (UTP).
“Screened twisted-pair is nice, but lots can go wrong,” Kish said. “Both designers and installers must really be trained on screened products if they are to perform quality installations. For example, even the ground wires can carry a lot of electrical noise, so it is criti-cal that screened cabling installers must have really good grounding. A poorly installed screened system can end up worse than a well-installed UTP system.”
“Installing a shielded system makes some sense,” Niemiera said, “but UTP usually more than meets the requirements. And that’s why 95 percent of the market is, and will remain, UTP. A shielded solution requires more expensive materials, and it is harder ... to install and terminate, which results in increased labor costs.
“There really needs to be an accurate environmental assessment before an owner chooses shielded,” Niemiera said. “Will the system be in a high noise environment, like in an industrial setting with a lot of DC motors creating electromagnetic interference? Or on a multibuild-ing campus near a radio tower? Then the shielded cable may eliminate a lot of external electrical noise. But the owner and designer should still test for high ambient noise on a floor-by-floor basis before deciding to use a shielded solution.”
“Shielded cables are common overseas,” said Hugo Draye, marketing manager for Certification Tools, Fluke Networks. “It can be a way to prevent alien crosstalk, but only if it is done right. The installers must follow the proper procedures.”
Draye recommended that contractors test for alien crosstalk, regardless of whether they are using shielded or unshielded cable.
“It’s really a bad idea not to test for it. But the good news is that contractors really don’t need to test each cable for it. If contractors will just judiciously test selected cables, then they will know if they have an alien crosstalk problem or not,” Draye said.
He explained that often it is only necessary to test one cable from each bundle for alien crosstalk.
“Contractors only need to look on a bundle-by-bundle basis, and that significantly reduces the time and labor required for testing alien crosstalk,” Draye said.
Myth #5: Since twisted-pair is made out of metal, it is more durable than glass fiber optics, so it is does not require delicate handling.
“Twisted pair is copper, but it must be treated with TLC,” Draye said. “Contractors can’t sidestep the rules and meet the standards, or their networks will pay later. They just can’t cut corners. Networks must be designed within the proper parameters and then installed with care.”
For example, pulling tension is critical, Niemiera said, adding that, “It is so critical that twisted-pair not be pulled with more than 25 pounds of tension. If a contractor is pulling a cable overhead for more than 100 feet, then the installer needs to pop a ceiling tile and help that cable along midway.”
“Twisted-pair is a robust [cable], but you need to understand how to use it,” he said, providing yet another example. “If you have a slab on grade, you need to expect that water will get in there, so use an indoor/outdoor product instead of a regular indoor cable.”
Twisted-pair cabling is here to stay. Its continued lower cost and ever-increasing functionality have made it the product of choice for networks, and industry sales suggest no change in this longstanding trend. Properly trained and sufficiently dedicated employees can install this media to provide state-of-the-art capabilities for nearly all modern industries. As a result, the vast reach of twisted-pair cable is almost legendary.
MUNYAN is a freelance writer in Olathe, Kan., specializing in technical and business writing. He can be reached at www.russwrites.com.