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Planning guidelines for wired communications.

Tired of all the hoopla for wireless communications? Then read on, as we'll be updating you on some of the key issues associated with plain old wire-based installations.

Chances are most of your current installed base of communications equipment uses some from of physical wiring. But the days of "JK" station wiring and "PIC" cables are quickly passing into history.

Bandwidth available with twisted pair wires is being stretched daily. We regularly accept 100 Mb/s over twisted pair, and are talking about additional bandwidth leaps in the next few years.

Will fiber supplant copper? Eventually, this will happen (most likely in the next century). However, the costs associated with fiber must drop sharply if it is to occur.

To find out more about the key issues associated with wire-based cable installations, we spoke with Tom Hahn, president of Response Time, Inc., a cable installation and systems integration firm based in Williamstown, N.J.

The biggest difference in cable installations today, compared with 10 years ago, is speed. "Back then, the average data speed was 1200 baud," Hahn says, "while today the norm is 10Base-T and megabyte speeds."

Cable technology has also changed, according to Hahn. "Older cables required shielding, while today's cables do not," he adds.

"It's important for users to conduct a needs analysis," Hahn says, "and if they can't do it themselves, they should bring in an experienced consultant."

Hahn suggests doing a needs analysis in combination with the cabling company and equipment vendor.

Before beginning any cable work, check to see what permits and authorizations are needed. These will vary by area and, often, by community. "Cable requirements in a major city can be much tougher than in the suburbs," Hahn says. He adds that high-voltage (e.g., electrical) lines usually require permits, while low voltage (e.g., telephone) lines may not. A reputable cabling contractor will know the codes and regulations.

After cables are installed, but before they are connected to telecomm apparatus, they should be tested for proper operation. While numerous types of test equipment are available, Hahn believes a time domain reflectometer (TDR) is one of the most important. It can identify most problems along a circuit, such as crossed pairs, cable cuts or other potential problems. Hahn recommends a test for near end crosstalk (NEXT) as crucial to proper circuit operation.

With fiber optic cable, the most significant issues are terminating the cable, properly polishing the cable ends, and not exceeding the specified bend radius when cables go around corners.

Environment, such as temperature and humidity, are not necessarily major concerns. However, placement of unshielded cable near power sources or near water pipes can be asking for potential problems.

Ensuring that facilities are available in an outage is usually limited to running extra wire pairs along a cable route or diversely routing backup cables.

"Sometimes the extra pairs we install are helpful when we find that primary pairs do not test satisfactorily," he says. "That way we can switch over to the alternate pair with no loss of service to the customer."

When selecting a cabling contractor, check credentials and references. "Experience is important," Hahn says, "Because once you've identified experienced people, then you can shop for the best price."

Many electricians now perform telecomm cable installations. However, some firms are not really qualified to install cable for these applications. One important way to differentiate among contractors is tools. Check for the types of tools and test gear a company plans to use, especially more expensive ones like TDRs. A device to test near end crosstalk costs about $6,500.

"Contractors who do fiber installations must have the proper terminating tools," Hahn says, "and these tools are usually quite expensive." If these kinds of tools are not present, Hahn adds, users should be suspicious of the contractor.

Also, check for the use of name brand products, such as wire, connectors, cross-connects and patch panels. Check for the gold content in cable connectors. The higher the gold content, the better the overall connection will be. Some cable and terminal manufacturers, such as AMP, are well known for their use of gold in components.

"Gold content is one of the most critical factors when selecting cable products," Hahn says. "It often means the difference between an excellent installation and an acceptable one."
COPYRIGHT 1993 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1993 Gale, Cengage Learning. All rights reserved.

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Author:Kirvan, Paul
Publication:Communications News
Article Type:Tutorial
Date:Aug 1, 1993
Words:718
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