Q: Does the tia/eia-568a Commercial Building Telecommunications Cabling Standard allow me to bring the cable into the closet, punch it down on a wall-mounted 110 block, off the 110 block to the 110 connector on a rack-mounted patch panel, and then use a patch cord to connect to a hub? Or should I eliminate the wall-mounted 110 block and punch it down directly on the 110 connector on a rack-mounted patch panel? The first scenario seems more flexible.
Richard Tweet
State of Alaska
Anchorage, AK
A: The standard does allow such an approach, but it is not the best-performing solution. In fact, every time you add another piece of connecting hardware to the channel, performance is degraded. The answer depends on how good your channel needs to be. Trading some performance for better cable administration may work fine in your particular situation, but I am more cautious.
Since the Telecommunications Industry Association and Electronic Industries Alliance (Arlington, VA) "invented" Category 5 cable back in November 1991, we have learned a plethora of new terms, such as short-link resonance phenomena, propagation delay, delay skew, structural return loss, and the latest--alien crosstalk (see "Alien crosstalk mandates E.T.--extra testing," Cabling Product News, page 16). Alien crosstalk occurs between the conductor pairs in one cable with conductor pairs in an adjacent cable.
I remember a cartoon from the days of the asbestos scare: Two rats were using handheld hairdryers and the caption read, "Remember the good old days, when all we had to do was smoke cigarettes and drink booze?" Now the cartoon could be: One Category 5 link says to the other, "Remember the good old days, when all we had to worry about was attenuation and near-end crosstalk?" My point is, the surprises just keep coming. The cable in the wall continues to be required to meet additional parameters that were not in the standard when the cable came off the production line and was installed in buildings around the globe.