Q: I work in the Telecommunications Department at Louisiana State University and have several questions. Let`s presume I have two Buildings, A and B. The service provider`s demarcation point is in Building A, which contains a private branch exchange (PBX). A 100-pair cable connects the two buildings. Within Building B, a 50-pair cable connects the first floor to the second.
Should the backboard colors be brown where the cable originates in Building A and terminates in Building B?
We are using protection at both ends of the cable. Shouldn`t each end of the cable land on a green instead of a brown backboard?
Concerning the 50-pair cable in Building B that connects the first and second floors, should the backboards be white?
Ric Simmons
Louisiana State University
Baton Rouge, LA
A: Colored backboards are a carryover from the old days. Using colored labels on the termination fields is more commonplace today.
ansi/tia/eia-606, the little-known and difficult-to-understand standard of the American National Standards Institute (New York City) and the Telecommunications Industry Association and the Electronic Industries Alliance (tia/eia--Arlington, VA), addresses color-coding. But the way that most of us actually color-code cabling is another carryover from the old days. The most notable exception between these is the crux of your problem.
In pre-divestiture days, AT&T always used purple for PBX equipment; red for key system equipment; blue for distribution; and green for feeder cables. When PBX vendors began providing turnkey systems for customers, AT&T introduced orange as "the company side" of the demarcation point, which was then termed the "network interface."
tia/eia-606 specifies purple for PBX equipment; red for key system equipment; blue for horizontal cabling at the telecommunications closet (TC) or the equipment room, not at the telecommunications outlet; and orange for the service provider side and green for the customer side of the demarcation point.
Backbone cable in tia/eia-606 (previously called feeder and distribution cable) is based on the two-level hierarchical star backbone described in tia/eia-568a. The first level is from the main crossconnect (MC) to a TC in the same building or to an intermediate crossconnect in a remote building. The second level is between two TCs within the building containing the MC or between an intermediate crossconnect and a TC in a remote building.
During the development of tia/eia-606, AT&T proposed additional colors to provide granularity for the various hierarchical levels of backbone cabling. tia/eia-606 specifies brown for interbuilding backbone cabling; white for first-level backbone cabling in the building containing the MC or second-level backbone cabling in buildings not containing the MC; and gray for second-level backbone cabling in the building containing the MC.
The standard also specifies yellow for auxiliary circuits, alarms, maintenance, security, and other miscellaneous circuits.
My first and most important rule for color-coding cabling is: Always use the same color label at each end of a cable.
Having spent the last 21 years at the University of Texas at Austin on the "green side" of the network interface, I have had to devise a plan that could easily be understood not only by our technicians, most of whom had Bell System experience, but also by service providers who extend their services to various campus buildings via our cabling. As a result, all interbuilding cabling terminates on protected fields, with green labels indicating the cable and pair.
When we began installing and administering intrabuilding structured cabling systems in 1988, the Bell System legacy continued, with one exception: All intrabuilding backbone cabling was terminated on fields, with white labels indicating the cable and pair. When tia/eia-606 was published, nothing at the university changed. We do not use brown or gray labels and we do not claim to be tia/ eia-606-compliant.
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, the University of Texas, Austin, TX 78713; tel: (512) 471-0112, fax: (512) 471-8883, e-mail: [email protected].