by Jeff Carrell, Electronic Communications Chairman
Part 1 of this series discussed the first component of the OSI Physical Link Layer - cabling. In LAN technology, the electronics of the physical layer electronics have been referred to as: amplifiers concentrators, hubs, and MSAU's, depending on the topology used. Most of the time, "hub" is the operative word.
Hubs come in many variations: from a few ports, to hundreds of ports; from a small enclosure not much bigger than an apple, to larger than a mini-fridge; from under $50 to well in excess of $25K.
There are basically three types of hub designs:
Unless otherwise stated, this article assumes the use of the RJ45, an 8P8C style connector supported by most hubs.
In Ethernet, there are three different speeds: 10Mb/s, 100Mb/s and 1Gb/s (although gigabit Ethernet is not yet a standard). Additionally, there is the capability to support full-duplex speeds which doubles the effective throughput. Token Ring has three speeds: 4Mb/s, 16Mb/s and 100Mb/s (100Mb/s TR is referred to as FDDI or CDDI). Token Ring also supports full-duplex, but only on 16Mb/s and 100Mb/s technologies.
Many hubs have an LED indicator per port known as "link." This indicates that a device has successfully loaded or been powered up, and the connection between the device and the hub is active and OK. However, depending on many issues a link light does not always guarantee a signal is passing. Bad or improperly pinned cabling can allow some pins to provide a link light, but no signal passing or the physical port of the hub may be bad and still provide a link light.
When connecting devices to an Ethernet hub, a straight pinned cable is used (following either T568A or T568B wiring configurations - see April Signals). When connecting two Ethernet hubs together, a cross-over cable must be used (T568A on one end, and T568B on the other), or one of the hubs must have a port that can be configured to "cross-over," a common feature on higher priced stand-alone and modular hubs. If a cross-over cable is used, a link state LED may be active/on, but no signal will pass. If a straight pinned cable is used to connect two hubs together, usually no link state LED is on, and therefore no signal will pass (this assumes that neither hub has a "cross-over" port capability or it is not in use).
When connecting devices to a Token Ring hub, a straight pinned cable is used (following either T568A or T568B wiring configurations). When connecting two Token Rings hubs together, two straight pinned cables are used to connect a pair of ports designated as "Ring In/Ring Out" (not device ports). Because of the function of the signal is moving in a logical 'ring,' you must extended the ring by connecting the two hubs together so that the ring is maintained and lengthened. You cannot simply connect a device port (IBM "lobe" port) on one hub to another device port on the second hub - no signal will pass. If IBM MAUs or 100% compliant devices are being used, there are special cables available for connecting both devices to the MAU and MAU-to-MAU, since the connector (IBM Data Connector) is not an RJ45 type connector.
In the next article I'll discuss the active electronics that is installed in host devices…NICs.
Copyright © 1997 Jeffrey L. Carrell All Rights Reserved
Debra Wawro took first place in the Region Paper Contest on April 12 in Denver. Her presentation and paper, "Waveguide-grating Couplers for Photonic Antenna Illumination" topped the field of twelve outstanding submissions from around the Region. Congratulations, Debra!
The Dallas/Fort Worth Chapter of the IEEE Lasers and Electro-optics Society announces its 1997 Student Research Competition.
Graduate and undergraduate students attending colleges and universities in the Metroplex are invited to submit papers (five copies) not later than May 5, 1997 to Andrew Ketterson, Secretary-DFW LEOS Chapter, Texas Instruments Incorporated, 13588 N. Central Expressway M/S 134, Dallas, Texas 75265 (Phone: 972-995-5725, FAX: 972-995-2836, email: andrew.ketterson@ti.com). Students need not be a member of IEEE or LEOS.
Papers should be 3-4 pages long, describing original research in the area of lasers and electro-optics. They will be judged on technical content, originality, significance of work, clarity, and interest to the LEOS community. Recently published papers are acceptable. Include phone number, email address, school affiliation, and name of advisor in cover letter.
Cash awards and winning papers will be presented at LEOS May 21 meeting (see Calendar of Events).
Slightly more than 18% of Fort Worth Section members (333) went into arrears last month for non-payment of dues. Historically, half of these will renew membership before September. However, these individuals have been dropped from distribution lists for IEEE publications (in case you're not reading this and wondering where your magazines are).
IEEE Central Texas Consultants Network and PACE will be hosting
their first annual Industry/Consultants Workshop in Austin on
May 17th. The workshop will provide a forum for discussing industry
trends with multidisciplined experts, and initiating potential
time-saving solutions. It will include member presentations on
determining product feasibility, advertising on the Web, statistical
process control, genetic engineering, and designing for noise
minimization. For more information, contact Bill Thorpe at 512-863-8621.
JOB CUTS HIT 15-MONTH HIGH - The economic numbers may be painting a rosy picture of the jobs market, but the good times did not keep companies from cutting jobs last month at the fastest pace in 15 months. That's according to a survey by a leading outplacement firm. Challenger, Gray & Christmas, which tracks job cuts nationwide, says 50,182 workers lost their jobs in March, up 33.9% from last year. The industry sectors with the most job cuts were aerospace-defense, computers, financial services, retail, transportation, automotive, services, industrial goods, consumer goods, and food.
IEEE-USA wants to ensure that efforts to restructure the electric power industry are consistent with sound engineering and economic principles. To further its educational effort on this issue, IEEE-USA is sponsoring a one-day symposium entitled, "What Should be the Role of the Federal Government in Restructuring the Electric Power Industry: A Technology Policy Perspective" to discuss the many difficult technical and related regulatory issues inherent in restructuring.
The symposium will address restructuring from the standpoint of technology policy and the need to plan and operate future electric power systems. The goal is to inform policy makers and IEEE members about key technological and institutional issues of the debate. Leaders from government, industry and academia will speak at panel sessions covering a range of policy perspectives.
Electric power industry leaders are invited to participate in the Symposium scheduled for June 11, 1997 at the Hyatt Regency Washington at 400 New Jersey Avenue, NW in Washington, DC. Contact Paul Johnson at 202-785-0017 ext. 320 or at p.johnson@ ieee.org for information. Or, keep an eye on the IEEE-USA's Energy Policy Committee web page at http://www.ieee.org/usab/ DOCUMENTS/ FORUM/COMMITTEE/epc.html.
Efforts begun in 1995 to deregulate the electric utility industry are picking up speed in the states and in the 105th Congress, where committees with jurisdiction over energy matters have already scheduled hearings and workshops to help legislators and the public.
On Jan. 30, Sen. Dale Bumpers, D-Ark., a new player in the field, introduced the Electric Consumer Protection Act (S. 237), a bill "to protect residential users and small business operatives"; to ensure fairness to utility companies that have been "following the rules laid down by statute over the past 60 years"; and to promote an orderly transition to a competitive retail electric market.
The Department of Energy (DOE) and the Administration have confirmed their willingness to work with Congress and the states "to move America to a more competitive electricity future." Deputy Energy Secretary Charles B. Curtis notes that there is no actual experience on whether or not competition will be good for typical electricity consumers. Some think competitive forces will lead to a drop in prices; others think most, "if not all, of the benefits of competition will go to large users of electricity such as heavy industry."
Eight states have already adopted laws or regulatory arrangements to permit retail competition in the next few years. They are California, Massachusetts, New Hampshire, New York, Pennsylvania, Rhode Island, Vermont, and Arizona. Full-blown deregulation has cleared legislative and regulatory hurdles in California, Pennsylvania and Rhode Island. In all, every state except Tennessee is examining the possibility of requiring deregulation of retail electrical markets.
Two high-profile studies released in February report alarming shortages of talented technology workers in the United States and elsewhere. The findings come from a university-based group, the Stanford Computer Industry Project, and from the Information Technology Association of America (ITAA).
According to the ITAA, there is currently a shortage of 190,000 qualified workers in the United States to fill industry jobs. Sen. John Warner, D-Va. characterized the report "as a clarion call to Congress to re-examine the uses made of federal tax dollars for educational purposes." He promised to examine Department of Education programs aimed at finding innovative solutions to workforce problems.
The results of the Stanford industry project, which were released Feb. 21, indicate that there is a global shortage of talented software people. This shortage has already had an effect on all segments of the software industry; and even more extensive use of "underutilized software talent, e.g. from India," will "not alleviate the shortfall during the next decade."
IEEE was one of the 23 sci/tech organizations that combined forces to call attention to the fact that the FY 1998 budget marks the fifth consecutive year of constant-dollar decline in the federal investment in research. Organizers of the unusual collaborative effort were able to attract the attention of several lawmakers, including Sens. Phil Gramm, R-Texas, and Joseph Lieberman, D-Conn., and Reps. James Sensenbrenner, R-Wis., and George Brown, D-Calif.
On Jan. 21, Sen. Gramm introduced the National Research Investment Act of 1997 (S. 124) with co-sponsors Sens. Connie Mack, R-Fla., and Kay Bailey Hutchison, R-Texas . According to Gramm, the bill would double the amount spent by the federal government on non-defense research over ten years. It gives priority to investments in basic science and medical research and does not allow funds to be used for commercialization of technologies.
In the House, Rep. George Brown, D-Calif., announced that he favors an increase in Federal R&D spending of at least 5% and plans to incorporate a provision to this effect in a future bill aimed at balancing the budget.
THE IEEE PRODUCED NEARLY 30 PERCENT OF THE WORLD'S LITERATURE in electrical engineering, computers and control topics in 1996, according to a recent penetration survey conducted by INSPEC. The IEEE published nearly 28,000 articles on electrical engineering topics and more than 20,000 articles on computers, control theory and technology. Together, the IEEE and the Institution of Electrical Engineers (IEE) published more than 33 percent of the world's literature in those areas.
THE UPDATED IEEE STANDARD DICTIONARY OF ELECTRICAL AND ELECTRONICS TERMS IS AVAILABLE - This new edition provides an accurate, dependable and comprehensive resource of the most current collection of standardized terms and definitions. The dictionary has undergone an intense and complete revision and contains more than 33,000 standardized terms and definitions from every field of electrical engineering, electronics and information technology. For more information or to order, contact IEEE Customer Service, 800-IEEE (4333) or 908-981-0060. List: $95.00, Mbr: $80.00; Product No. SH94459; ISBN 1-55937-833-6.
With new officer elections here, I wanted to reflect on where we, the Fort Worth Section, have come and perhaps where we are going.
The beginning of this year was marked by the publication of a "1997 Strategic Plan." Within this plan were several goals both for the short term and the long term.
Our first short term goal is one I am particularly proud of: host a metroplex conference during engineers week. Metrocon '97, thanks to Terry Mayo and his committee, provided a rich variety of topics and tutorials to over 100 attendees. Truly a success either standing alone or compared with our past conference events.
In accordance with our second short term goal of planning for the 1998 Region 5 conference, Alan Triggs and his planning committee have worked very hard to take this event to a new level. A level that will reach not only the administrative personnel of IEEE, but the members who attend this event. Another success "in the making."
Our first long term goal was to enhance our financial stability. Several options have been discussed this year and recently the Executive Committee formalized a "Revenue Resource Committee" chaired by Ed Safford. The charge of this committee is to funding for existing and additional services.
To excel in community citizenship, as our second long term goal states, will require more than officers of the Section attending community events. While these certainly keep us moving in the right direction, we need your help. Many of you have opportunities to speak of electrical engineering and of IEEE. We ask that you do just that, particularly to the youth who are our next generation of engineers.
In closing, the Section has a clear mission to Provide Superior Service to Fort Worth Members of the IEEE. I believe that we are headed in this direction, perhaps now with a renewed focus. We certainly have and will continue to change "drivers" on this journey and it has been my sincere pleasure to "drive for a while."
- James C. Painter, P.E.
Recognizing our Section members for their long-time commitment to the profession on the anniversary of their joining IEEE.
60 yrs
55 yrs
45 yrs
40 yrs
35 yrs
30 yrs
25 yrs
20 yrs
According to legend, one day when the mathematician K. F. Gauss was a schoolboy, his teacher wanted to leave the classroom for a while. To keep the students busy he asked them to add all the integers from one to 100. Before he was out of the room, Gauss had the answer. Can you make the calculation in less time than it takes a teacher to leave the room?
Answer to last month's Brainbuster:
The largest amount of change in US coins you can have and still
not be able to change a dollar is $1.19: three quarters (or half
dollar and quarter), four dimes and four pennies.
Jean Eason, Editor