Word problems - Cabling Installation & Maintenance

Word problems


Nov 1, 2004

It was seven years ago when I first wrote an editorial that appeared in this magazine. I was a staff editor at the time, and my boss, who traditionally wrote the monthly editorial column, gave me the opportunity to voice an opinion to the thousands who subscribe to CI&M.

In that editorial, I called for a moratorium on the word “futureproofing.” In 1997, industry “experts” were chanting about enhanced Category 5 (we were still a long way from the official Category 5e specifications) as a provider of headroom and futureproofing. And if you really wanted to be ready for anything the future would bring, many also said, then have your contractor pull a multimode fiber (FDDI-grade 62.5-micron, of course) to each workstation as well. Seven years and 1 Gigabit later, many users can point to the unused 62.5-micron optical-fiber cable in their walls not as futureproofing, but as current proof that not all promises are kept.

I only revisited that old column because I have decided it’s time once again to pick on a few words that get tossed around our industry and, for one reason or another, get my goat:

NIC card. It’s not a NIC card. It’s a NIC-network interface card. Not network interface card card. Just like the ATM at a bank stands for automatic teller machine, but you hear “ATM machine” all the time. And VIN stands for vehicle identification number, but many say VIN number. Stop saying NIC card, everybody. You are driving me crazy.

ACR. It stands for “attenuation to crosstalk ratio,” and represents the difference between the strength of a signal being transmitted and the noise sources interfering with that signal. I have two problems with ACR. First, attenuation does not describe the strength of a signal; it describes the loss of signal strength as that signal travels. And the number used in an ACR calculation is not the attenuation; it’s the remaining signal. My second problem is with “ratio.” To me, it’s not a ratio, it’s a difference. I remember from mathematics class that a subtraction yields a difference-just like an addition yields a sum, a multiplication yields a product, and a division yields a quotient. So, if we’re subtracting the interference from the signal strength, we should have a difference, not a ratio. (I like the term SNR-signal-to-noise ratio-a bit better than ACR because it at least gets the first part right. But SNR still uses “ratio,” so I have to give it the thumbs-down, too.)

Certify. This word is my ulterior motive for writing this column. An article that I authored this month (page 20) talks about some testing products new to the market, and also about the nomenclature in the testing world. The gory details are there, but I’ll summarize by saying that the word “certify,” although used all over the place to describe TIA/EIA-568 standard-compliant structured cabling systems, does not appear in the 568 standard. In conducting research for the article, I asked with all sincerity where the word appears in the standards. I was sure that it was there somewhere, and wanted to be able to cite chapter and verse so I could explain just exactly what is and is not a certified system. When I asked where it was, the rather simple response was: nowhere.

I have attended technical seminars, conducted interviews, and walked trade-show floors for years, freely using the words “certify” and “certification” to mean that a system meets standards specifications. Then I found out that the TIA has been hesitant to use the word because doing so could be risky, even though my dictionary tells me that the word means “to guarantee as meeting a standard.”

My advice here is for end users of communications cabling systems to be cautious-and meticulous-about the wording of testing requirements in your contracts. Make sure to demand that your cabling system is tested in accordance with TIA/EIA-568-B.1 Clause 11, Cabling Transmission Performance and Test Requirements.

It certainly was shocking to me to learn after several years that to call a system “certified” doesn’t mean what I thought it did. Though it was a bit embarrassing, I’ll get over it. But I would hate for a user to learn the same lesson the hard way.

Patrick McLaughlin
Chief Editor
patrick@pennwell.com


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