Horizontal cabling in open offices

A draft proposal on specialized horizontal cabling practices for open-office work groups is working its way through the Telecommunications Industry Association`s TR-41.8 standards committee, and should soon be accepted as a TIA technical system bulletin. This draft resurrects the work-area transition point in the guise of a multiuser telecommunications outlet or consolidation point, depending on whether you plug in or punch down. This modified transition point is offered as a panacea for all the

L. Steve Brown, RCDD

Intel Corp.

A draft proposal on specialized horizontal cabling practices for open-office work groups is working its way through the Telecommunications Industry Association`s TR-41.8 standards committee, and should soon be accepted as a TIA technical system bulletin. This draft resurrects the work-area transition point in the guise of a multiuser telecommunications outlet or consolidation point, depending on whether you plug in or punch down. This modified transition point is offered as a panacea for all the frustrations of designing telecommunications systems into modular furniture.

Most telecommunications system designers and installers are familiar with transition points and the kinds of frustrations they create. A transition point, for example, will add attenuation and, unless the equipment cords are Category 5 cable, degrade the end-to-end channel. In addition, for the typical high-density open-office environment--with approximately three 4-pair cables for every 72 square feet of office space--the addition of transition points can markedly increase the cost of fit-up in labor and materials. And the addition of transition points, while seeming to ease worries about later reconfiguration, adds to cable management complexity, resulting in increased administrative cost.

Is flexibility increased?

These costs have been acceptable because it has been argued that the design increases flexibility, but is this an illusion? It would appear so. Facilities designers, space planners and furniture people have no idea where multiuser telecommunications outlets are placed.

In section 4, paragraph 1, the draft proposal states: "The use of multiuser telecommunications outlets allows horizontal building cabling to remain intact when the open-office plan is changed." It will remain intact, but will it be any more useful than last decade`s 25-pair cables, which are probably still in the ceiling?

Let`s assume, for example, that a multiuser outlet has been placed 75 meters from the nearest closet to serve a work-group cluster. Six months later, the facilities group decides the modular furniture should be rearranged to accommodate a change in the work group. The rearrangement creates two locations in the cluster that are beyond the 15-meter distance allowed from the multiuser outlet. The only solution, of course, is to add another multiuser outlet. If this happens regularly, then five years later there may be enough multiuser outlets and consolidation points to enable you to add a location almost anywhere--no matter what the furniture configuration is.

The major problem with this proposal, however, is that modular furniture is not designed to comply with Category 5 installation requirements as outlined in EIA/TIA-568A. Even with the use of multiuser outlets and consolidation points, there are still limitations on raceways in the furniture, because most of the horizontal space is consumed by power cable. Other problems with these furniture partitions include

- Scarcity of telecommunications outlets and the placement of outlet openings, which are usually punched to be convenient for power

- Insufficient raceway depth, calling for the use of mounting boxes so the required bend radius is maintained and the raceway is not blocked by jacks

- Difficulty of removing installed cable from splines.

Issue is vendor orientation

The issue here is not the lack of a standard. The issue is that instead of providing direction to the modular-furniture manufacturers on how to comply with standards, the TR-48.1 committee is letting the modular-furniture manufacturers write their own standard. For example, the fourth draft of the proposal was revised by the Business and Industry Furniture Manufacturers Association (Grand Rapids, MI); it was altered without following the usual procedure of contributions being made and then accepted or rejected by the committee. In this revision, all entries that started with "furniture manufacturers are strongly encouraged..." were altered or deleted.

In the strawman version of this draft, all these issues were pointed out and many were addressed. But the recommendations on furniture changes have been left out.

The ratification of this standard may only result in absolving modular-furniture manufacturers of the responsibility of addressing the lack of provision for telecommunications in their products. The user community will then have traded the straightforward simplicity of TIA/EIA-568A for the illusion of flexibility.

L. Steve Brown, RCDD,is wiring infrastructure standards manager at Intel Corp., Folsom, CA. His remarks first appeared in the February 1995 BICSI News.

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