by Jeff Carrell, Electronic Communications Chairman
I am embarking on a series of articles that will cover LAN technologies over the course of the next year or so. My goal is to make this series a form of tutorial that can be compiled into an introduction guide to LANs.
The series will follow the OSI Model, as defined by the ISO and including IEEE specifications. Although the chart (below) depicts a top down view of operation, the technologies are discussed from the bottom up, as each subsequent layer builds on the previous layer.
The first area of discussion is the physical medium in which all the LAN data is transported - the cable. Cabling for LANs has evolved over the course of 24 years, from coax to fiber optics, with every imaginable option and type available.
Today the predominate cable type used is ANSI/TIA/EIA 568A - UTP Category (Cat) 5. This cable has four twisted pair conductors, and can support frequencies up to 350Mhz (at least so far) and transmission data rates of up to 1Gb (in trial at 1Gb). Depending on the topology type either two pairs or all four pairs may be used, and also pin-outs vary depending on topology. The predominant connector used is an RJ-45, 8 pin/8 conductor jack/outlet.
For most LAN topologies, the ANSI/TIA/ EIA 568A specifications for Cat 5 allow for a total end-to-end distance of 100M. This is broken down into 90M for the horizontal (or main) run (MC/TC to WAO), 7M for the interconnection to the active electronics (in the MC/TC) and 3M for the connection of the device (usually the workstation) to the WAO.
Under the ANSI/TIA/EIA 586A specs, there are two supported pin-out configurations.
Although the differences between T568A and B are subtle, if they are mixed within a cable plant most topologies will not operate when the pairs are "crossed." When installing a new cable plant, if the ANSI/TIA/EIA 586A spec is not included detailing T568A or B, T568A is the default. However I have seen many more new and upgraded cable plants installations using T568B.
The pinouts used for Ethernet and Token Ring are as follows:
I have also seen many cable plant installations where only the specific pins required for the topology were connected/terminated, thus allowing for either a duplex RJ-45 WAO to use a single cable run, or the extra conductors at the end of the cable were simply cut off. This does not follow the ANSI/TIA/EIA 586A specs, nor does it allow for some of the newer topologies to be used on the existing Cat 5 cable plant. Therefore, in order to be fully compliant with the ANSI/TIA/EIA 586A specs and allow for future topologies to be implemented, all 8 conductors must be terminated per the ANSI/TIA/EIA 586A specs, following either the T568A or B guidelines.
In the next article I'll discuss the active electronics that the
cabling connects to….hubs.
Copyright © 1997 Jeffrey L. Carrell All Rights Reserved
The Fort Worth and Dallas Power Engineering Societies present the Ninth Annual Dallas and Fort Worth IEEE/PES Industry Exposition on Wed., May 21 from 3 to 6:30 p.m. at the Arlington La Quinta, 825 N. Watson Rd.
If you are a involved in the engineering, specification or purchase of electrical equipment or related telecommunication or computer equipment, come to the PES Expo to find out about the latest products and services from over 40 vendors serving the industry. Visit http://www.flash.net/~ieeeftw/dfwexpo to find out about the participating vendors.
All qualified preregistered attendees will receive two free tickets to see the Texas Rangers play the Oakland Athletics at 7:35pm at the Ballpark in Arlington.
Mail or fax your registration before Friday, May 16, 1997 to: IEEE Expo Registrar, c/o TU Electric, ESB 117, P.O. Box 970, Fort Worth, TX 76101-0970, FAX: 817-215-6889. Include: name, member number, company, address, email, phone, and fax information. You may also register on our Web page or call Bill Hutchings 214-956-0608, Michael Quinn 817-215-6649 or Chuck Preecs 214-812-8218.
Metrocon '97 was a great success this year. One of the goals of Metrocon was to conduct a local conference where relevant technical and professional material was made available to our local Section IEEE members. This goal was far exceeded. There were a wide variety of sessions to choose from and each of the presenters were very knowledgeable professionals. This year we enjoyed good weather, good sessions and good food. Thanks to all who planned, presented sessions and attended the conference and awards ceremony. Metrocon is an excellent way to kickoff Engineers Week so go ahead and mark your calendars for next year.
Terry Mayo, Metrocon Chairman
Debra Wawro, UTA student and winner of the Section's Student Paper Contest, has placed second in the South Area Contest and advances to the Region Contest taking place in Denver in April. Congratulations, Debra!
AAES NEWSLETTER NOW AVAILABLE VIA EMAIL: IEEE members can now receive the FactsFax newsletter of the American Association of Engineering Societies, which provides the latest engineering-related news from Capitol Hill, directly by e-mail. To subscribe, send an e-mail message to majordomo@major-domo.ieee.org with no subject line and the text message: "subscribe aaes@majordomo. ieee.org." Questions or problems, contact Chris Brantley at 202-785-0017 or c.brantley@ieee.org.
ENGINEERING RADIO ADS AVAILABLE: A series of radio public-service announcements highlighting the achievements of U.S. engineers is now available from the IEEE-USA Washington Office. The 60-second ads, produced by the American Association of Engineering Societies' Media Relations Advisory Committee and sponsored by Tau Beta Pi, illustrate the theme, "Engineers: Inventing Today, Implementing Tomorrow," and feature such engineering greats as Jack Kilby, John Pierce, Harold Rosen, Marvin Camras, Wilson Greatbatch, Paul Lauterbur, Albert Babb, and Abel Wolman. For a copy of the tapes to air on your local station, contact Chris Currie at 202-785-0017, ext. 342, or c.currie@ieee.org.
MEMBERSHIP DEVELOPMENT COMMITTEE REPORTS that total U.S. membership in IEEE, including students, dropped by 5,436, or 2.5 percent, from 1995 to 1996. U.S. membership in 1995 was 222,600, compared to 217,164 in 1996. Overall IEEE membership was down slightly, by .88 percent, with membership outside North America rising 2.9 percent.
IEEE STANDARDS IS OFFERING A NEW VHDL TUTORIAL on CD-ROM to aid in the comprehension and use of IEEE Std 1076-1993 (Very High Speed Integrated Circuit Hardware Description Language). The interactive tutorial is organized into four modules designed to incrementally add to the users' understanding of VHDL and its application. This product is licensed for single user purposes. Use for multiple-user environments will be available upon request. For more information, please email stds.vhdinfo@ieee.org or call 908-562-3804.
Young Engineers (0-10 years experience) are invited to free videoconference on career issues April 16 (4:30 - 8 p.m. CST). The 2nd Young Engineers Forum broadcast will address emerging technologies, opportunities for international employment, staying competitive in the employment market, managing interpersonal relations for career development, and lifelong learning and problem-solving techniques. IEEE member Robert L. Krause, P.E., will discuss "The MBA Option." This broadcast will be live and interactive: you will be able to call or fax your questions to the speakers and they will be answered on the air.
The Young Engineers Forum satellite broadcast is produced by the American Society of Mechanical Engineers (ASME) is funded by a grant from the Engineering Foundation with the participation of the American Institute of Chemical Engineers (AIChE), the American Society of Civil Engineers (ASCE), and the Institute of Electrical and Electronics Engineers (IEEE). For more information or for registration materials, contact ASME's Ellen Lung at lunge@asme.org (800) 843-2763; fax: (201) 882-1717.
They are two very different companies: United Services Automobile Association (USAA), one of the largest property and casualty insurers in the United States, and City Public Service (CPS), the country's oldest public electric utility and a natural gas distributor. However, they both have many employees who work in the electrical, electronics and computer fields, the home turf of the IEEE.
Institute members visited USAA and CPS in February in San Antonio, Texas to determine how new or existing IEEE resources and programs can enhance the skills and careers of the companies' technical employees. The IEEE and the companies' executives also discussed ways the Institute can help these corporations meet their business objectives.
Clarence R. "Reggie" Williams, vice president, Network Services at USAA, said his company is interested in developing in-house standards in a number of areas, in addition to technology assessment, a new area for the IEEE. 1995 IEEE President Tom Cain, suggested the Institute's New Opportunities in Standards committee examine ways in which the IEEE can share its experience in standards development for application on a micro rather than the usual macro scale to help meet the company's needs.
City Public Service, one of most progressive companies in the electric power industry, raised some different issues. Arthur von Rosenberg, CPS General Manager, noted, among other concerns, young engineers' general lack of communications skills, particularly conversational abilities.
"Deregulation and mergers among utilities have brought about significant turmoil," said IEEE President Chuck Alexander. "This includes shifting engineers to new jobs and new skill requirements. Institute resources and programs can help engineers map their careers while also improving their technical and 'soft' skills such as business and technical writing and presentation techniques."
As a result of the meetings, the IEEE is examining the possibility of setting up training in these non-technical areas specifically for CPS. For information on IEEE industry visits contact: Sonny Barber, 908-562-6823, or s.barber@ieee.org.
In response to a growing demand, the IEEE has taken several steps to make more technical information available to members and customers on the World Wide Web. Here are three recent examples:
Recognizing our Section members for their long-time commitment to the profession on the anniversary of their joining IEEE.
35 yrs
30 yrs
25 yrs
20 yrs
What is the largest amount of change in US coins you can have in your pocket and still not have change for a dollar bill?
Answer to last month's Brainbuster:
What are the next two letters in the sequence: O T T F F S S ? E and N. The sequence is the first letter of the numbers One, Two, Three…
Jean Eason, Editor