Q: We occupy a 20-story building in central Philadelphia and are planning to move one block to another building with similar capacity. The new building is being stripped and rebuilt inside, including all telecommunications cabling. For the last five months, everyone has been trying to sell us Category 5 equipment. In the process, we`ve realized that there`s more to cable and outlets than just twisting some wire together and putting a PC board together with an RJ-45 jack and a 110 clip.
After seeing a few vendors of cable and connecting hardware, we identified significant ease-of-use differences among products. However, we are confused about the Category 5 link-performance claims from the different vendors. With electrical products, we understand connecting hardware, but with telecommunications cable, we`re really lost.
Two issues that we`ve identified so far include:
Pair balancing--This relates to what you do in the RJ-45 termination assembly to compensate for imbalance caused by separation of pair 2 in the jack. There are a few techniques--the Siemon Co. (Watertown, CT) does it one way, Krone Inc. (Englewood, CO) another. Ortronics Inc. (Pawcatuck, CT) uses some PC-board plate equipment, and AMP Inc. (Harrisburg, PA) hides its plates between layers of the board.
Twisted-pair cable performance--What makes one cable better than the next? What influences impedance, structural return loss and near-end crosstalk?
We need to be able to differentiate vendors. With connecting hardware, the ease-of-use issue makes the choice easy, and electrical information on the hardware is presented in a uniform manner. With cable, it`s a different story. When cable from Berk-Tek Inc. (New Holland, PA) is $245 per 1000 feet and Commscope Inc.`s (Claremont, NC) is $270/1000 feet, why pay $300/1000 feet for DT-350 from Belden Wire & Cable Co. (Richmond, IN) and deal with separating the pairs during installation? And what`s the difference between Berk-Tek and Commscope cable?
Please tell me how to get the information we need.
Christopher C. Kohl
Reliance Insurance Co.
Philadelphia, PA
A: Welcome to telecommunications infrastructure design, 1995 edition. The information you need about Category 5 is in the Telecommunications Industry Association/Electronic Industries Association standard 568-A. However, balance is currently under study in the Connecting Hardware Task Group. BICSI at (800) 242-7705 can provide a list of registered communications distribution designers and RCDD/local area network specialists available for consultation in your area.
