5E or 5e? Both provide some hEadroom

Sept. 1, 2002
I recently received a question from a government agency asking which cable to specify, "Cat 5E" or "Cat 5e."

I recently received a question from a government agency asking which cable to specify, "Cat 5E" or "Cat 5e." Upper and lower case mean the same-Category 5 enhanced. With the confusion that does exist, I thought a table comparing "apples to apples" would be helpful. The table below provides performance parameters for Category 5, 5e, and 6 at 100 MHz.

So, with Category 5, 5e, and 6 at 100 MHz, what are you really paying for? Headroom, lots of headroom.

Standards compliance
I also received an inquiry about the media converter pictured on page 17 of this pub lication's July issue (with in the article "Media converters facilitate horizontal fiber architectures"). The person inquiring stated that ADC, employer of the article's author and manufacturer of the media converter pictured, has a novel approach to the problem of converters at the workstation outlet. But he wanted to know how he could employ this solution and remain standard compliant, considering that the devices are installed behind the telecommunications outlet (TO). Don't standards specify that all cable converters must be installed outside the TO, he wants to know?

Well, it certainly is correct that the media converter shown in that photo would be behind the faceplate, with only the 8-pin connector visible from the user side of the media converter. But is this really forbidden within the TIA building cabling standards?

Click here to enlarge image

To answer his question (and my own), let's take a trip down memory lane. In July 1991, ANSI/TIA/EIA-568 was published. This was before there were categories of copper cabling, and optical fiber appeared only in informative Appendix A, which discussed "some additional cables which may be of interest."

ANSI/TIA/EIA-568 spoke of tele communications outlets and horizontal wiring. The standard defined telecommunications outlet as "a connecting device located in a work area on which horizontal wiring system cable terminates and which can receive a mating connector." And Chapter 4 described horizontal wiring as the portion of the telecommunications wiring system that extends from the work area TO to the telecommunications closet (it was called a "closet" back then). The horizontal wiring includes a TO in the work area, mechanical terminations for horizontal cables, and crossconnections located in the closet.

TIA/EIA-568 also cautioned us, "Some networks or services require electrical componentsellipseon the tele communications outlet of the horizontal wiring. These electrical components shall not be installed as part of the horizontal wiring. When needed, such electrical components shall be placed external to the telecommunications outlet. This will facilitate the use of the horizontal cabling for varying network and service requirements."

We could all close our eyes and visualize exactly what the text meant. The problem was, we did not all see the same picture. So, very subtle changes were made in ANSI/TIA/ EIA-568-A to make things "more clear" for the reader, and to reflect what the members of the committee felt was the most advantageous for their respective companies. You may recall connector designs in which the UTP cable was actually terminated on card-edge connectors into which outlet/connectors actually inserted. These products were selling well as the standard was in draft, and they had a strong lobby in the committee.

Fast forward to October 1995, when ANSI/TIA/EIA-568-A was published. Optical fiber was now a recognized cable for use in the horizontal and backbone cabling systems. 568-A defined telecommunications outlet/connector as "a connecting device located in a work area on which horizontal cable terminates." The standard also described horizontal cabling as "the portion of the telecommunications cabling system that extends from the work area telecommunications outlet/connector to the horizontal crossconnect in the telecommunications closet. The horizontal cabling includes horizontal cables, telecommunications outlet/connectors in the work area, mechanical terminations, and patch cords or jumpers located in the telecommunications closet."

It is interesting that this description disagrees with the definition of horizontal cabling, which first appears within ANSI/TIA/EIA-568-A as "horizontal cabling: the cabling between and including the telecommunications outlet/connector and the horizontal crossconnect." No mention of patch cords or jumpers located in the telecommunications closet.

Fast forward again, to April 2001 when 568-B.1 was published. With the exception of adding multi-user telecommunications outlet assemblies and consolidation points to the list of things included in horizontal cabling, little change occurred between ANSI/TIA/EIA-568-A and ANSI/TIA/EIA-568-B. This is a good thing, yes? Well, not exactly. When you closed your eyes and visualized what they were actually telling you, you pictured a faceplate with outlet/connectors in place, probably on the front of an electrical box. And the area inside the box was hallowed ground-no application-specific electrical component allowed in there.

But that is not what is required by the standards. There is nothing in B.1 that requires the media converter to hang "in harm's way" on the front side of the faceplate. In fact, the word "faceplate" does not even appear in 568-B.1.

The media converter is an application-specific electrical component installed external to the outlet/connector, which in this case is the ST-to-ST interface at the media converter. We have now hit network equipment-end of channel. The 8-pin modular jack on the other side of the media converter is the beginning of another channel. It's like the backbone fiber going into the switch and the Category 5e cable going out to the crossconnect in the telecom room.

Click here to enlarge image

Donna Ballast is BICSI's standards representative, and a BICSI registered communications distribution designer (RCDD). Send your questions to Donna via e-mail: [email protected].

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