Navy 'dress blues,' Cat 7, and power over data cabling

Q: While recently reviewing a Navy specification, NFGS 16710, I found a reference to requiring a blue color for horizontal cabling jacket material when installed in plenum spaces

Aug 1st, 2002
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Q: While recently reviewing a Navy specification, NFGS 16710, I found a reference to requiring a blue color for horizontal cabling jacket material when installed in plenum spaces. Is this requirement a carryover from the TIA/EIA standards? I see nothing in the National Electrical Code that requires a specific color. Will the new Category 6 specifications address the outer jacket color?

Charlie Mandeville, PE, EE
Pace Collaborative
Virginia Beach, VA

A: NFGS 16710 is a specification issued by the Atlantic Division, Naval Facilities Engineering Command, for regional use in Italy. Per NFGS 16710 Section 2.4.2.1 Horizontal Copper, if you are installing horizontal cabling for the United States Navy in Italy, the outer jacket of the cable is to be blue. That is, any four-pair, 100-W, unshielded twisted-pair (UTP) Category 3 or Category 5e cable- regardless of the CMR or CMP rating-shall have a blue PVC jacket.

My best guess for the origin of this particular requirement is that it's a takeoff on the color specified for the horizontal cabling termination field in TIA-606-blue.

There isn't an NFPA code or a TIA standard requirement for cable jacket color code for UTP cable. This is not to say that having different colors of cable in a facility isn't a good idea, and I encourage designers to consider establishing a site-specific color code based on the category of cabling being installed. This makes identification for cable removal much easier when the time comes.

Back when they were first kicking around the idea of categories of cable, jacket color was a hot topic. I argued against having the standards mandate a particular color jacket to indicate a particular category of cable. Why? Because standards are voluntary in the U.S., and the TIA does not own the right to certain Pantone colors. Anyone can make a cable jacket that is a particular color; say, for instance, blue for Category 5. Then it would become common knowledge that anytime, anywhere you see a blue cable jacket, it would be a Category 5 cable. But what about the cable manufacturer that also makes its Category 3 cable blue? Then the installer goes into the distributor and says, "I need 10 boxes of the blue cable." You get the idea.

Cat 7 on the wish list
On June 7, TIA TR-42 announced publication of its Category 6 standard for telecommunications cabling as TIA/EIA-568B.2-1. During an ad hoc meeting held to discuss planning for ANSI/TIA/EIA-568C, it was decided that development of a Category 7 cabling system specification should be added to the "wish list" for ANSI/TIA/EIA-568C.1, for consideration in the future. Yes, the photocopies are hardly cold on the first of the two addenda addressing Category 6, and Category 7 is already on the "wish list." Will this Cat have nine lives?

Power over data cabling
Lately, the construction documents I have been reviewing include telecommunications cabling for the usual voice and data, but also include cabling to support lighting controls, security access controls, monitoring systems, building automation systems, wireless access points, point-of-sale terminals, Web cameras, and even Internet Protocol (IP) telephony. In most cases, you can read "support" to include power-delivered to the device over the same telecommunications cabling.

So, how will adding power to the signal affect the channel performance? That is a job for the TR-42 DTE task group, which has been charged to develop specifications and guidelines for horizontal cabling with mid-span power. While the urgency for this work is to support equipment defined in Clause 33 of the IEEE 802.3 Data Terminal Equipment (DTE) Power via Media Independent Interface for Ethernet, other applications could also use their findings.

To date, they have developed a matrix of parameter values, including resistance, resistance unbalance, current capacity, voltage rating, and power capacity for components (solid cable, flexible cable, and connector), and configurations (permanent link and channel). What remains is to fill in those blanks.

At their June meeting, the DTE group estimated that it would take them 12 months to complete their work. After that, we can expect to see an addendum to TIA/EIA-568B.1 for channel performance, which will specify topology, design, installation practices, and field testing. We will also see an addendum to TIA/EIA-568B.2 for specifications for all components that comprise a powered cabling system.

So, how does this work? Generally speaking, you remove one of the components of the channel and replace it with a power-sourcing component (PSC). The PSC would not only perform the function of that particular component, but also add power to the cabling-typically, only the 4-5 and 7-8 pairs.

For example, when a PSC replaces a cord, all pairs would have to meet the mechanical, conductor, and pair-designation requirements, but only the 1-2 and 3-6 pairs would have to meet the performance requirements for the category specified. This is so that when the cabling is reconfigured and the PSC is removed, a category cord can simply be plugged into the connector, restoring the channel to compliance. While the same requirements apply for connectors, restoring the channel to compliance would not be as simple as changing a patch cord.

A PSC cord would resemble a three-legged octopus with plugs. The plug with all pairs terminated would connect to the horizontal cabling, while the other two would connect to the power source and the signal source as appropriate. This is where careful cable management pays off. Plug the wrong half of the cord into the power and ...

Or, a better solution might be to patch from the equipment into a rack-mounted "black box" with a standard category patch cable, and from the "black box" to the horizontal cable with another standard category patch cable, thereby avoiding the confusion. This "black box" is commonly called a power bridge. While this does not meet TIA-568, neither does the split-cord scenario. That's why they are working on the addenda.

I was recently asked my thoughts regarding powering Ethernet devices using the spare pairs, and what sort of industry standard would apply in this situation. For years, we have all been taught that the cabling system's transmission performance depends on the quality of the equipment cord, crossconnect, horizontal cable, connector, and work-area cord, as well as the "workmanlike manner" with which they are installed and maintained. That "workmanlike manner" included maintaining separation from power sources where possible. But now we will be sharing the sheath.

ANSI/TIA/EIA-568 was written to support voice and data over balanced cabling. The channel was not intended to supply power (unbalanced common mode) to the devices, so some limits will need to be defined-like maximum current, maximum voltage, and DC loop resistance.

The usual field-testing of category cable involves testing an end-to-end permanent link or channel. But with a PSC in the link or channel, you would likely need to test twice-once without the PSC to ensure category compliance of the link or channel, and one test, with the PSC plugged in, of only the non- powered pairs.

Now if they can just figure out how to stop the arching, which often occurs when plugging and unplugging the components, I think we will be there.


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Donna Ballast is BICSI's standards representative, and a BICSI registered communications distribution designer (RCDD). Send your questions to Donna via e-mail: ballast@utexas.edu.

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