Consulting-Specifying Engineer - August 2008 - (Page 61) Equipment Lifecycles Choosing the right communication cable A variety of cable types are available on the market. The one you select for a commercial office building may not be the same as for a manufacturing facility. BY TIM KUHLMAN, PE, RCDD, Electrical Engineer and Telecommunications Specialist, CH2M HILL—Electronics and Advanced Technologies business unit, Portland, Ore. V oice and data cabling from the communications room to the outlet can represent a sizeable investment to install or replace. It is worth taking the time to consider the choices of cabling, striking a balance between capital costs of installation and having an infrastructure that will not be obsolete in a few years. Understanding the networking protocol and related bandwidth it will need to support are important factors in determining cable type. The most common protocol for data networking is Ethernet, and specific Ethernet protocols may be selected by bandwidth such as 10 Megabit, 100 Megabit, 1,000 Megabit (or 1 Gigabit), and 10 Gigabit. The protocol usually is chosen by the information technology group or person responsible for the network applications and network architecture. The lower the bandwidth, the less data that travels through the cable, and the lower the performance—which requires a less expensive cable. Likewise, higher bandwidth means higher performance and higher cost. The overall trend in the industry is that data packets have become larger. Applications that once used only text now use graphics. Another trend is to augment text with video, or to replace text entirely with video. This is common for training and presentation material. Access to the Internet also has driven the need for more network bandwidth. There once was a time when product catalogs were printed and shipped to the office. Now most catalogs are online downloads. All of this has driven the need for more network bandwidth. The standards When choosing a cable type for networking (both voice and data), the cabling standard for reference is “TIA/EIA 568.B: Commercial Building Telecommunication Standard.” Several parts of the standard address different components of the cabling infrastructure. This cabling standard works in conjunction to support the IEEE 802.3 Ethernet Standards. Table 1 lists the cable type and the Ethernet protocol supported. The Category 5e, 6, 6 shielded, and 6a cables are all four-pair copper 100 ohm twisted-pair cables designed for a maximum cable channel distance of 100 meters, or 90 meters from the communication room to the outlet. The TIA 568.B Standard and its companion document, “TIA/EIA 569: The Commercial Building Standard for Telecommunication Pathways and Spaces,” are two resources for the design of communications infrastructure in a commercial building environment. The resources for communications cabling in the industrial building environment are not as well developed as they are for the commercial environment. There isn’t an industrial standard comparable to the commercial cabling standards. Good engineering judgment is required to adapt the commercial standards to industrial applications. Consulting-Specifying Engineer • AUGUST 2008 61
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