Q: I hope you will be able to clarify my understanding of the tia/eia-568a standard. Clause 5.5.1, "Intra and Inter-Building Distances," has an allowance of 5 meters for equipment connection cables or cords. I have assumed that this is for applications requiring Category 3, 4, or 5 unshielded twisted-pair (utp) cable or stp-a shielded twisted-pair (stp) cables. I presume the standard makes no allowance for crossconnect jumpers or patch cords, and that the connections to the equipment are single-port, since consolidating ports requires a crossconnect type of install-ation.
However, if consolidating equipment cable is required, is a crossconnect allowed, and how might the 5-meter distance limit be split between the patch cord and the equipment cable? Also, do the distance limitations in clauses 5.5.3, "Crossconnections," and 5.5.4, "Cabling to Telecommunications Equipment," apply only to voice transmission over utp and fiber media, or may these distances also be applied to utp and stp-a data circuits? The distance stated in clause 5.5.4 appears to conflict with the distance stated in clause 5.5.1.
Metro Board of Education
A: While it may not be easy to decipher, the intent of the passage in the tia/eia-568a standard is to give guidance on both utp, which is typically used for voice, and Category 3, 4, 5 and stp-a for data applications. The transmission parameters for Category 3, 4, 5 and stp-a are all based on 100-m horizontal cable lengths. Hence, the reduced lengths for patch cables and equipment cables are necessary. Hopefully, the information in the figure and tables can demystify the maximum-length requirements outlined in tia/ eia-568a and telecommunications systems bulletin tsb-75.
Donna Ballast is a communications analyst at the University of Texas at Austin and a bicsi registered communications distribution designer (rcdd). Questions can be sent to her at Cabling Installation & Maintenance or at PO Drawer 7580, University of Texas, Austin, TX 78713; tel: (512) 471-0112, fax: (512) 471-8883, e-mail: email@example.com.