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34754 results in Cambridge Textbooks

Page 1656 of 1738

  • Chapter 4 - Boundary

  • from Part I - Practice
  • Etienne Wenger
  • Book:
    Communities of Practice
    Published online:
    05 July 2013
    Print publication:
    28 July 1998, pp 103-121

  • Summary

    In the previous chapter, I characterized communities of practice as shared histories of learning. Over time, such histories create discontinuities between those who have been participating and those who have not. These discontinuities are revealed by the learning involved in crossing them: moving from one community of practice to another can demand quite a transformation. But practice does not create only boundaries. At the same time as boundaries form, communities of practice develop ways of maintaining connections with the rest of the world.

    So far, I have focused almost exclusively on communities of practice as if they were isolated. But that focus was artificial. Communities of practice cannot be considered in isolation from the rest of the world, or understood independently of other practices. Their various enterprises are closely interconnected. Their members and their artifacts are not theirs alone. Their histories are not just internal; they are histories of articulation with the rest of the world.

    As a result, engagement in practice entails engagement in these external relations. For a job like claims processing, which is considered by many to be relatively narrow, the range of related communities of practice as well as constituencies without a shared practice is actually rather complex. It involves, among others, claims technicians, underwriters, system designers, and various levels of management at Alinsu; beyond the company, there are other claims processors, patients, benefit representatives, accounting clerks, and a variety of medical and legal professionals.

  • 8 - Video cassette recorders

  • Philip Hoff, California State University, Northridge
  • Book:
    Consumer Electronics for Engineers
    Published online:
    13 September 2019
    Print publication:
    28 July 1998, pp 345-458

  • Summary

    Although recorders capable of recording a TV signal on magnetic tape have been available since the early 1950s and vidéocassette recorders have been since the early 1970s, they never became a consumer item until 1975, when Sony introduced the Betamax VCR. Earlier units were generally too complex, too expensive, and too voracious in their appetite for tape. The first Betamax units could record for one hour on a cassette, making them almost as easy to use as an audio tape recorder. Two years later, Matsushita introduced the VHS (Video Home System) VCR, which boasted recording times of two or four hours on a somewhat larger cassette. The Betamax system was then modified to allow two hours of recording. Subsequently VHS achieved a six-hour record time and Beta got up to three hours. For both machines, the longer record time yielded slightly inferior picture quality relative to the shorter record times. Although both systems used the same general principles in their electronics, they were not compatible either mechanically or electrically. If both systems were played at their fastest speed (one-hour play time for Beta; two hours for VHS), the Beta probably produced a slightly better picture quality, but if both were operated in the two-hour mode, the VHS picture was generally better. The fundamental reason for this is that the Beta cassette is smaller and simply cannot hold as much tape as the VHS cassette does. Thus the Beta achieved the two- and threehour modes by slowing down the tape speed. This hurt high-frequency response and so picture details were lost.

    Although there were a number of more esoteric differences between the Beta and VHS systems such as tape tension (Beta lower in record and playback; VHS lower in fast forward and reverse), it can hardly be maintained that the chief issue in the minds of most consumers was anything but the longer record time of the VHS. This led to the situation in 1985 that all manufacturers of the Beta system except Sony had either switched to the VHS system or were “hedging their bets” by manufacturing both VHS and Beta systems. The dominance of VHS over Beta is now total. Virtually no tapes are produced in Beta format any longer. For these reasons, we will direct our attention exclusively to the VHS system.

  • Chapter 6 - Identity in practice

  • from Part II - Identity
  • Etienne Wenger
  • Book:
    Communities of Practice
    Published online:
    05 July 2013
    Print publication:
    28 July 1998, pp 149-163

  • Summary

    There is a profound connection between identity and practice. Developing a practice requires the formation of a community whose members can engage with one another and thus acknowledge each other as participants. As a consequence, practice entails the negotiation of ways of being a person in that context. This negotiation may be silent; participants may not necessarily talk directly about that issue. But whether or not they address the question directly, they deal with it through the way they engage in action with one another and relate to one another. Inevitably, our practices deal with the profound issue of how to be a human being. In this sense, the formation of a community of practice is also the negotiation of identities.

    The parallels between practice and identity are summarized in Figure 6.1. To highlight them in this chapter, I will (as I did in Coda I) go through the themes of Part I, chapter by chapter, but recast them in terms of identity. This exercise will yield the following characterizations.

    1. • Identity as negotiated experience. We define who we are by the ways we experience our selves through participation as well as by the ways we and others reify our selves.

    2. • Identity as community membership. We define who we are by the familiar and the unfamiliar.

    3. • Identity as learning trajectory. We define who we are by where we have been and where we are going.

    4. • Identity as nexus of multimembership. We define who we are by the ways we reconcile our various forms of membership into one identity.

    5. • Identity as a relation between the local and the global. We define who we are by negotiating local ways of belonging to broader constellations and manifesting broader styles and discourses.

  • Synopsis: Design for learning

  • from Epilogue: Design
  • Etienne Wenger
  • Book:
    Communities of Practice
    Published online:
    05 July 2013
    Print publication:
    28 July 1998, pp 225-229

  • Summary

    Learning cannot be designed. Ultimately, it belongs to the realm of experience and practice. It follows the negotiation of meaning; it moves on its own terms. It slips through the cracks; it creates its own cracks. Learning happens, design or no design.

    And yet there are few more urgent tasks than to design social infrastructures that foster learning. This is true not only of schools and universities, but also of all sorts of organizations in the public and private sectors, and even of entities usually not called organizations, like states and nations. In fact, the whole human world is itself fast becoming one large organization, which is the object of design and which must support the learning we need in order to ensure there is to be a tomorrow. Those who can understand the informal yet structured, experiential yet social, character of learning – and can translate their insight into designs in the service of learning – will be the architects of our tomorrow.

    By way of conclusion, I will use the concepts introduced in this book to discuss some issues of design as they relate to learning and practice, and by extension to community and identity. This discussion will do two things. It will provide a summary of the main themes and, at the same time, illustrate the use that can be made of the conceptual framework I have outlined.

  • Vignette I: Welcome to claims processing!

  • from Prologue: Contexts
  • Etienne Wenger
  • Book:
    Communities of Practice
    Published online:
    05 July 2013
    Print publication:
    28 July 1998, pp 18-34

  • Summary

    Ariel runs down the stairs. She has to be at work at 8:00, and with the traffic, she will need a lot of luck to make it. She should really stop using the snooze button. The fact is, she would rather go to work earlier and come home earlier. But it's people with more seniority who get to choose their hours first: they can take the 7:00 to 3:00 schedule. She had it for a while. It's a bit hard in the morning, but when you get off at 3:00, it's like you still have the day in front of you. Staying there until 4:00 makes a big difference. But now the office needed some people to answer the phones between 3:00 and 4:00, so junior processors have to stay later. Although she has been working in the claims office for well over a year, Ariel is still considered a junior processor. She has recently been promoted to a level 6.

    Predictably, it's congested between Ridgewell and Lincoln. As her car comes to a halt, Ariel grabs the rearview mirror to check her makeup. Overall, she takes good care of herself. She makes up, but discreetly, and dresses cleanly but not aggressively. Fortunately, the office is rather informal about appearance. You could spend a fortune otherwise. Of course, she could not go to work in shorts, but even jeans are OK as long as they are not torn.

  • Coda I: Knowing in practice

  • from Part I - Practice
  • Etienne Wenger
  • Book:
    Communities of Practice
    Published online:
    05 July 2013
    Print publication:
    28 July 1998, pp 134-142

  • Summary

    I will end this first part of the book with a brief essay on the nature of knowing in practice. This essay, which is philosophical but in a lighthearted kind of way, will allow me to provide a summary of the themes introduced in Part I in the context of discussing a specific topic. Focusing on knowing for this purpose is a useful topic, but this choice should not be interpreted as assuming that knowing is all that communities of practice are about, especially if by “knowing” one refers to some instrumental kind of expertise. Communities of practice should not be reduced to purely instrumental purposes. They are about knowing, but also about being together, living meaningfully, developing a satisfying identity, and altogether being human.

    Flowers and bits

    I will start with two odd questions. The first one was concocted long ago by Zen teachers to help their students think more sharply: What does a flower know about being a flower? The second question is the information-age version of the first: What does a computer know about being a flower?

    The question of what a flower knows about being a flower is somewhat troubling because there seem to be two contradictory answers. Being a flower is to no one as transparent, immediately obvious, fully internalized, and natural as it is to a flower: spreading those leaves, absorbing that specific spectrum of light from the sun, taking the energy in, building protein, sucking nutrients from its roots, growing, budding, blooming, being visited by a bee.

Consumer Electronics for Engineers
  • Philip Hoff
  • Published online:
    13 September 2019
    Print publication:
    28 July 1998
  • This book explains clearly the operating principles of 'real world' electronic devices, including video recorders, compact disk players, and mobile phones. Each chapter begins with a brief historical overview of the device concerned. The author then describes the key principles of each device's operation and presents a block circuit diagram. Next he analyzes these 'real world' circuits in detail, and, finally, he discusses the present state-of-the-art. This approach will help to integrate the many different aspects of an electrical engineer's course work, from physical optics to digital signal processing, as never before. Very accessible and containing over 350 illustrations and many exercises, this book will be an ideal textbook for undergraduate students of electrical engineering, and will also appeal to practising engineers.

  • Intro I: The concept of practice

  • from Part I - Practice
  • Etienne Wenger
  • Book:
    Communities of Practice
    Published online:
    05 July 2013
    Print publication:
    28 July 1998, pp 45-50

  • Summary

    Being alive as human beings means that we are constantly engaged in the pursuit of enterprises of all kinds, from ensuring our physical survival to seeking the most lofty pleasures. As we define these enterprises and engage in their pursuit together, we interact with each other and with the world and we tune our relations with each other and with the world accordingly. In other words, we learn.

    Over time, this collective learning results in practices that reflect both the pursuit of our enterprises and the attendant social relations. These practices are thus the property of a kind of community created over time by the sustained pursuit of a shared enterprise. It makes sense, therefore, to call these kinds of communities communities of practice.

    Claims processors: a community of practice

    Ariel and her colleagues do not come to Alinsu to form a community of practice; they come to earn a living. Gathered in Alinsu's office by their need for work, they want to fulfill their individual production quota. They want to make money in order to go on with their own lives, which they see taking place mostly outside of the office. They do focus on their work, but they keep glancing at the clock, waiting for the moment they are free to leave. For most of the time they spend at Alinsu, most of them would rather be somewhere else doing something else. Everyone knows this, employees and employer alike.

  • Coda 0: Understanding

  • from Prologue: Contexts
  • Etienne Wenger
  • Book:
    Communities of Practice
    Published online:
    05 July 2013
    Print publication:
    28 July 1998, pp 39-42

  • Summary

    As a nickname for the COB worksheet, the claims processors' expression “the C, F, and J thing” is quite telling. It names the activity not by reference to the insurance concepts it implements but by reference to lines in the worksheet. Indeed, the location of the data and the calculation are prescribed in terms of lines within the worksheet itself, to the point where knowing what to do next does not require any interpretation of the worksheet's underlying purpose. If one assumes that the worksheet has been designed correctly, then one need not take any responsibility for the outcome of the calculation and its implementation of actual contractual relations. The worksheet was specifically designed with this assumption in mind. Instead of giving claims processors the capacity to figure out how to do the calculation, the designers of the worksheet decided to prescribe exactly how to do it, step by step. The form removed from the execution of the procedure the need to assume responsibility for its meaning.

    This kind of form is very common, not only in claims processing but in all kinds of activities. Many people who fill out U.S. tax returns, for instance, would be hard-pressed to explain the exact meanings of some of the calculations involved in the various forms, tables, and worksheets, as intended by those who designed them.

  • Chapter 11 - Organizations

  • from Epilogue: Design
  • Etienne Wenger
  • Book:
    Communities of Practice
    Published online:
    05 July 2013
    Print publication:
    28 July 1998, pp 241-262

  • Summary

    Organizations are social designs directed at practice. Indeed, it is through the practices they bring together that organizations can do what they do, know what they know, and learn what they learn. Communities of practice are thus key to an organization's competence and to the evolution of that competence. I have argued, however, that communities of practice differ from institutional entities along three dimensions.

    1. 1) They negotiate their own enterprise, though they may at times construct a conforming response to institutional prescriptions (Chapter 2).

    2. 2) They arise, evolve, and dissolve according to their own learning, though they may do so in response to institutional events (Chapter 3).

    3. 3) They shape their own boundaries, though their boundaries may at times happen to be congruent with institutional boundaries (Chapter 4).

    The contrast detailed here is one between organizational design and lived practice. From this perspective, there are two views of an organization like Alinsu:

    1. 1) the designed organization, which I will often call the “institution” to distinguish it from the organization as lived in practice

    2. 2) the practice (or, more accurately, the constellation of practices), which gives life to the organization and is often a response to the designed organization.

    Both aspects contribute to making the organization what it is. Indeed, the organization itself could be defined as the interaction of these two aspects. Besides corporations like Alinsu, this characterization applies to nonprofit organizations and even subunits such as agencies, departments, or business units.

  • Chapter 3 - Learning

  • from Part I - Practice
  • Etienne Wenger
  • Book:
    Communities of Practice
    Published online:
    05 July 2013
    Print publication:
    28 July 1998, pp 86-102

  • Summary

    The negotiation of meaning is a fundamentally temporal process, and one must therefore understand practice in its temporal dimension. Some communities of practice exist over centuries – for example, communities of artisans who pass their craft from generation to generation. Some are shorter-lived but intense enough to give rise to an indigenous practice and to transform the identities of those involved. For instance, such communities may form as people come together to handle a disaster. The development of practice takes time, but what defines a community of practice in its temporal dimension is not just a matter of a specific minimum amount of time. Rather, it is a matter of sustaining enough mutual engagement in pursuing an enterprise together to share some significant learning. From this perspective, communities of practice can be thought of as shared histories of learning.

    In this chapter I discuss the internal dynamics that constitute these shared histories of learning. Toward this end, I will take up the themes introduced in the last two chapters, but with a focus on time and learning.

    1. 1) I will first talk about participation and reification as forms of memory, as sources of continuity and discontinuity, and thus as channels by which one can influence the evolution of a practice.

    2. 2) I will then discuss the development of practice with reference to the three dimensions introduced in Chapter 2. I will argue that learning along these three dimensions is what produces practice as an emergent structure.

    3. 3) Finally, I will turn to the learning by which newcomers can join a practice, that is, by which generational discontinuities are also continuities.

  • 6 - Monochrome TV

  • Philip Hoff, California State University, Northridge
  • Book:
    Consumer Electronics for Engineers
    Published online:
    13 September 2019
    Print publication:
    28 July 1998, pp 171-252

  • Summary

    Monochrome or black & white (B/W) TV signals are transmitted by very few stations now. It is still well worth our while, however, to understand monochrome TV. There are several reasons for this:

  • (1) B/W TV circuitry is a subset of color TV circuitry. If we understand it, we have a 100%-usable foundation for understanding color.

  • (2) Although B/W transmission is rare, B/W receivers are still manufactured. It is with such receivers that we concern ourselves in this chapter. In Section 6.4 we analyze one of the VLSI chips that makes such receivers so economical. Color signals are compatible with B/W receivers because the receiver circuitry simply ignores the color information.

  • (3) The mechanisms of picture (video) signal generation and picture formation are much simpler in monochrome sets.

    • The nature of monochrome TV signals

    The television principle

    The picture to be transmitted is focused onto a small photosensitive area. One very small area within the photosensitive device called a pixel (picture element) is probed by a finely focused electron beam, which generates a signal dependent on the light intensity at the point of impact. The exact mechanisms involved in this process are well covered in many books for a variety of imaging devices (e.g., Neuhauser and Cope, 1992). In solid-state imaging arrays, the pixel is addressed digitally rather than by means of an electron beam.

    In either case, the end result is the same. The output voltage associated with each pixel is a single-valued function of the light intensity at that pixel. Having determined the light level at that pixel, another pixel - usually an adjacent one - is checked to determine its light level. This process continues over the whole screen until every pixel on it has been evaluated. Then the process starts all over again. The sequence of analog voltage levels corresponding to the pointby- point illumination levels is called the video signal. It should be obvious that we must know the light level at every pixel, in order to reproduce the picture. The video signal contains just that information and yet, by itself, it is useless. A little thought will show why this is so. If we have the video signal, we could use its value at a given moment to determine the light level at a pixel on the display device - but which pixel?

  • 3 - Modern receiver circuitry

  • Philip Hoff, California State University, Northridge
  • Book:
    Consumer Electronics for Engineers
    Published online:
    13 September 2019
    Print publication:
    28 July 1998, pp 109-121

  • Summary

    As indicated in the introduction, new types of receivers and receiver circuitry are being introduced continually. In this chapter we will look at some of them.

    An integrated AM/FM receiver

    The receiver we consider here is one of the Sony Walkman series that is designed to drive lightweight stereo headphones rather than a speaker. The headphones are so intrinsic to the design that their cord also serves as the FM antenna! The schematic is shown in Fig. 3.1.

    We begin by directing our attention to the lower right-hand corner of the schematic. Rather than returning one headphone lead from each channel directly to ground, the ground return for both channels is through L7. This has a reactance of about 1.4 kΩ in the FM band but less than an ohm for audio frequencies. Thus one side of each headphone is AC grounded for audio, but a significant FM signal is developed across L7 and coupled via C39 to the RF input of the receiver. This capacitor's reactance is less than 50Ω in the FM band. Diodes D1 and D2 serve to prevent overdriving IC1. For reception of distant FM stations, Sl-1 couples the FM antenna circuitry directly to a bandpass filter. For local reception, the coupling is via R16, which attenuates the larger local signals. In the AM position, C1 AC grounds any FM signal received by the FM antenna. The DC potential on this line is .85 V for FM, but it gets pulled down to zero in the AM position of 57-7. This line is tied to the internal voltage regulator of 1C1 and may be a shutdown line. The 3 V input to the regulator (pin 26 of IC1) provides a regulated 1.3 V output on pin 8 when the voltage on pin 15 is at the normal value of .85 V (for FM). When pin 15 is grounded in the AM position, the regulator output shuts down, removing supply voltage from the FM front-end portion of 1C1. This supply line is bypassed to ground by C2 and C40. The grounded end of each of the parallel tuned circuits is returned to this 1.3 V regulated supply line. Therefore, they are AC grounded but not DC grounded. This is analogous to the ZN414 TRF 1C receiver of Chapter 1.

  • Chapter 8 - Modes of belonging

  • from Part II - Identity
  • Etienne Wenger
  • Book:
    Communities of Practice
    Published online:
    05 July 2013
    Print publication:
    28 July 1998, pp 173-187

  • Summary

    In Chapter 6,1 talked about identity in terms of belonging to communities of practice. But to make sense of the formation of identity in a context such as the institutional non-participation described in Chapter 7, it is necessary to consider modes of belonging other than engagement in practice. The claims processors' experience of both participation and non-participation is deeply part of their daily practice, but it also reaches beyond the walls of their office. In order to do their job, they must align their activities and their interpretations of events with structures, forces, and purposes beyond their community of practice and so find their place in broader business processes. Their identities as workers are affected by the picture they build of their position. They see themselves as participants in social processes and configurations that extend beyond their direct engagement in their own practice. They have to make some sense of many artifacts they encounter coming from practices they do not have access to. They may have to use their imagination to get a picture of these broader connections. They have an image of Alinsu, for instance, even though they have not had direct involvement with most of the practices that constitute the corporation. Yet this image is no less significant and, in a sense, no less real than their daily involvement at work.

Communities of Practice
  • Learning, Meaning, and Identity
  • Etienne Wenger
  • Published online:
    05 July 2013
    Print publication:
    28 July 1998
  • This book presents a theory of learning that starts with the assumption that engagement in social practice is the fundamental process by which we get to know what we know and by which we become who we are. The primary unit of analysis of this process is neither the individual nor social institutions, but the informal 'communities of practice' that people form as they pursue shared enterprises over time. To give a social account of learning, the theory explores in a systematic way the intersection of issues of community, social practice, meaning, and identity. The result is a broad framework for thinking about learning as a process of social participation. This ambitious but thoroughly accessible framework has relevance for the practitioner as well as the theoretician, presented with all the breadth, depth, and rigor necessary to address such a complex and yet profoundly human topic.

Page 1656 of 1738