13.4 DISTANCE LEARNING TECHNOLOGIES

Until the advent of telecommunications technologies, distance educators were hard pressed to provide for two-way, real-time interaction, or time-delayed interaction between students and the instructor or among peers. In the correspondence model of distance education, which emphasized learner independence, the main instructional medium was print, and it was usually delivered using the postal service. Interaction between the student and the instructor usually took the form of correspondence of self-assessment exercises that the student completed and sent to the instructor for feedback. Formal group work or collaborative learning was very rare in distance education, even though attempts have been made to facilitate group activities at local study centers. Also, traditionally, distance education courses were designed with a heavy emphasis on learner independence and were usually self-contained. With the development of synchronous (two-way, real-time interactive) technologies, such as audio teleconferencing, audio graphics conferencing, and videoconferencing, it is now possible to link learners and instructors who are geographically separated for realtime interaction. However, the type of interaction that takes place is usually on a one-to-one basis, between one learner and another and between one learner and the instructor at one particular time. These technologies are not very suitable for promoting cooperative learning between groups of learners located at different sites. Also, the synchronous nature of these technologies may not be suitable or convenient for many distance learners.

The asynchronous (time delayed) feature of computer mediated communications (CMC; see 14.2.3), on the other hand, offers an advantage in that the CMC class is open 24 hours a day, 7 days a week, to accommodate the time schedules of distance learners. Although CMC systems may be either synchronous (real time) or asynchronous (time delayed), it is asynchronous CMC, because of its time-independent feature, that is an important medium for facilitating cooperative group work among distance learners.

Current developments in digital communications and the convergence of telecommunications technologies, exemplified by international standards such as ISDN (Integrated Services Digital Network), make available audio, video, graphic, and data communication through an ordinary telephone line on a desktop workstation. Therefore, as we look at distance learning technologies today and look to the future, it is important to think in terms of integrated telecommunication systems rather than simply video vs. audio vs. data systems. More and more institutions that teach at a distance are moving toward multimedia systems integrating a combination of technologies both synchronous and asynchronous that meets learner needs. Therefore, while in the 1970s 'and 1980s many distance education institutions throughout the world used print as a major delivery medium, by the year 2000 many institutions will probably have adopted telecommunications-based systems for the delivery of distance education. This does not necessarily mean that print will no longer be used in distance education. It is more likely that print will be used as a supplementary medium in most telecommunications-based systems, and better ways of communicating information through print will be investigated and incorporated into the design of study guides and other print-based media.

In order to describe the technologies used in distance education, we have selected "The 4-Square Map of Groupware Options" that was developed by Johansen et al. (1991) which is based on recent research in groupware (see Fig. 13-1). This model seemed most suitable to our purpose, because we see distance education moving from highly individualized forms of instruction, as in correspondence education, to formats that encourage teaching students as a group and collaborative learning among peers. The "4-square map of groupware option" model is premised on two basic configurations that teams must cope with as they work: time and place. Teams or groups of people who work together *on a common goal deal with their work in the same place at the same time as in face-to-face meetings, and sometimes they must work apart in different places and at different times, as in the use of asynchronous computer conferencing. They also need to handle two other variations: being in different places at the same time, as in the use of telephones for an audio teleconference, and at the same place at different times, as in workplaces, study centers, or laboratories. Based on these configurations, the 4 square model classifies four types of technologies that support the group process: (1) same time/same place, (2) different time/different place, (3) same time/different place, and (4) same place/different time. These four categories are used for describing technologies that currently support distance teaching and learning.

While we use the 4-square model to discuss the major distance education technologies currently being used, we feel that this model does not lend itself very well to discussing new and future developments in integrated telecommunications. Since these integrated systems incorporate many of the features that we classify separately in the 4-square model, we have decided to describe new and future developments in a separate section titled "Future Directions and Emerging Technologies" (p. 417).

Figure 13-1. The 4-square map of distance education technology options. (Adapted from R. Johansen et al, 1991, p. 16.)

13.4.1 Same Time/Same Place Instruction

Same Time/Same Place group interaction is the most familiar format of face-to-face meetings. Certain objectives in distance education programs can only be met by meeting face-to-face. The British Open University, which teaches entirely at a distance brings students on campus during the summer to participate in laboratory experiments. When course objectives require the careful demonstration, observation, practice and feedback of life threatening procedures such as a surgical procedure, it is important to organize face-to-face meetings. In a face-to-face setting accepted practices are only modified slightly to accommodate electronic media. Basic technologies that facilitate a face-to-face meeting involve an overhead projector, a flip chart, electronic blackboard or a projection system that displays computer screens via a LCD monitor. At the more sophisticated end are desk top workstations for each group member which run on special software that helps the group to brainstorm, generate ideas, rank solutions and vote. Also, a record of the group process can be produced at the conclusion of the groups' activities. IBM's Decision Conference Center in Bethesda, Maryland employs such sophisticated groupware to facilitate group decision making processes. However, innovative approaches are now being adopted to the design laboratory work at a distance by using technologies, as in the dissection of a fetal pig experiment that was designed by the University of Maine using a combination of two-way interactive television, videotape and group work at sites.

13.4.2 Same Time/Different Place Instruction

There are two kinds of Same Time/Different Place Instruction: 1. a meeting through a telecommunications medium or teleconferencing where participants who are separated by geographic distance can interact with each other simultaneously, and 2. the use of non-interactive media such as open broadcast television and radio to instruct a vast number of students at the same time without the ability for the students to call back and interact with the originators of the program. Teleconferencing can be classified into four separate categories depending on the technologies that they use: audio teleconferencing, audiographics teleconferencing, video teleconferencing and computer conferencing. There are two types of computer conferencing: synchronous computer conferencing when two or more computers are linked at the same time so that participants can interact with each other, and asynchronous computer conferencing when participants interact with each other at a time and place convenient to them. Asynchronous computer conferencing is described under Different Time/Different Place instruction. The four major types of teleconferencing vary in the types of technologies, complexity of use and cost. However, they have several features in common. All of them use a telecommunication channel to mediate the communication process, link individuals or groups of participants at multiple locations, and provide for live, two-way communication or interaction. One advantage of teleconferencing systems is that they can link a large number of people who are geographically separated. If satellite technology is used for the teleconference, then, there is no limit to the number of sites that can be linked through the combination of several communications satellites. In order to participate in a teleconference, participants usually have to assemble at a specific site in order to use the special equipment that is necessary for a group to participate in the conference. The only exceptions are audio teleconferences which can link up any individual who has access to a telephone, computer conferences that can link up individuals, their computers and modems at home, or direct broadcast satellites that can deliver information directly to participant's homes. However, if more than two people are present at a participating site then it is necessary for the participants to gather at a location which is equipped with teleconferencing equipment in order to participate in a teleconference. This may restrict access for some learners. In terms of control, participants will have control over the interaction that takes place in a teleconference only to the extent that the instructional design allows for it. However, if the teleconference is taped for later review, students will have more control in the use of the conference. The unique advantage of teleconferences is that they provide for two-way interaction between the originators and the participants. Teleconferences need to be designed to optimize the interaction that takes place during the conference. Interaction needs to be thought of not only as interaction that occurs during the teleconference but pre- and post conference activities that allow groups to interact. Monson (1978) describes four design components for teleconferences: humanizing, participation, message style and feedback. Humanizing is the process of creating an atmosphere which focuses on the importance of the individual and overcomes distance by generating group rapport. Participation is the process of getting beyond the technology by providing opportunities for the spontaneous interaction between participants. Message style is presenting what is to be said in such a way that it will be received, understood and remembered. Feedback is the process of getting information about the message which helps the instructor and the participants complete the communications loop. Monson (1978) offers excellent guidelines for incorporating these four elements into teleconferencing design. The symbolic characteristics and the interfaces that are unique to each medium are discussed with the description of each technology.

13.4.2.1. Audio Teleconferencing. Audio teleconferencing or audioconferencing is voice-only communication. Even though it lacks a visual dimension, audio teleconferencing has some major strengths: It uses the regular telephone system, which is readily available and a familiar technology; it can connect a large number of locations for a conference; the conferences can be set up at short notice; and it is relatively inexpensive to use when compared with other technologies.

The interconnection medium for an audio teleconference is usually the telephone, which can incorporate microwave, satellite, fiber optic, or coaxial cable transmission. The conference call between three or more persons at different locations is the simplest type of audio teleconferencing. For multipoint teleconferencing among three or more sites, an audio bridge is required to enable sites to interact clearly. The bridge links the telephone lines together so that parties at each location can hear and talk to each other. Olgren and Parker (1983) observe that there are many system options for audio teleconferencing, but the most common forms are: (1) user-initiated conference calls or ("ad lib" teleconferencing), (2) operator-initiated or dial-up or (dial-out) teleconferencing, (3) dial-in or meet-me teleconferencing, and (4) dedicated audio networks.

In order to facilitate group-to-group communication, audio teleconferencing requires the use of some type of amplified telephone equipment with a loudspeaker and microphones. The equipment may be built into the room or may be portable. Audio teleconferencing equipment can be described as simplex, quasi-duplex, or full-duplex, depending on the kind of interactivity and interruptibility of the conference connection.

Olgren and Parker (1983) observe that one should keep in mind that voice communication is the backbone of any teleconferencing system, with the exception of computer conferencing. Sophisticated video or graphics equipment can be added to any audio system. But it is the audio channel that is the primary mode of communication. If the audio is of poor quality, it will have a negative impact on users of even the most sophisticated graphics and video technologies. This is very important to keep in mind, because the evaluation of interactive television systems have shown (Dillon, Gunawardena & Parker, 1992) that the most often cited technical problem in television systems is the poor audio quality. While expensive investments have been made in video and graphics systems, very little attention has been paid to the improvement of audio quality in video and audiographics conferencing systems.

Audio teleconferences can be enhanced by adding a visual component to the conference by mailing ahead of time printed graphics, transparencies, or a videocassette to be used during the conference. Each site must be equipped with an overhead projector and a VCR if such graphical or video support is used.

13.4.2.2. Audiographics Conferencing. Audiographics systems use ordinary telephone lines for two-way voice communication and the transmission of graphics and written material. Audiographics add a visual element to audio teleconferencing while maintaining the flexibility and economy of using telephone lines. Audio teleconferencing is now combined with written, print, graphics, and still or full-motion video information. Most audiographics systems use two telephone lines, one for audio and one for the transmission of written, graphic, and video information.

Currently, the simplest audiographics system is the addition of a fax machine using a second telephone line to an audio teleconference. Printed information can be exchanged during the conference using the fax machine so that visuals can be shared between sites. As a result of recent developments in computer, digital, and video compression technology, fairly sophisticated computer-based audiographics systems are available in the market. These systems combine voice, data, graphics, and digitized still video to create a powerful communications medium. The PC-based systems have specially designed communications software that control a scanner: graphics tablet, pen, and key board; and video camera, printer, and a modem.

One of the key advantages of an audiographics system is the ability to use the screen-sharing feature of the system. Participants at different sites can use different colored pens to create a graphic on the same screen at the same time. This feature enables the use of collaborative learning methods that involve learners at the remote locations. Since each site is most often equipped with the same types of equipment, it is possible to originate instruction from any location. The systems allow for a higher degree of interaction than one-way video and two-way audio systems. If the system is equipped with a video camera, it is possible to bring video footage to the class or show three-dimensional objects. High-resolution, full-color still video images can quickly be transmitted through dial-up telephone lines. Some systems have incorporated a keypad device that is used for polling participant's opinions and feedback. When the instructor asks a multiple-choice question, participants can use the keypad to key in their response. A central computer tabulates these responses, and the instructor gets an instantaneous statistical summary of the entire group's responses, as well as how each site responded. This is a good way of soliciting and getting feedback from the participants, so that the instructor can adjust his or her presentation depending on the responses received.

Because audiographics systems use regular telephone lines, they are much more cost effective than full-motion video systems. Participants need to be present at locations equipped with the systems in order to participate in a conference, and this may be inconvenient to some learners.

The systems enable the transmission of audio, graphics, data, and still-video information and create a moderate sense of social presence. 'Me human-interface depends to a large degree on the type of communications software that has been designed for the system. Most graphic systems can be mastered by novices with about I hour's training on the system.

13.4.2.3. Video Teleconferencing. Video teleconferencing systems transmit voice, graphics, and images of people. They have the advantage of being able to show an image of the speaker, three-dimensional objects, motion, and preproduced video footage. The teleconference can be designed to take advantage of the three symbolic characteristics of the medium: iconic, digital, and analog, where the iconic or the visual properties of the medium which is television's foremost strength can be manipulated to convey a very convincing message. Because of its ability to show the images of people, video teleconferences can create a "social presence" that closely approximates face-to-face interaction. Video teleconferencing systems are fully interactive systems that either allow for two-way video and audio, where the presenters and the audience can see and hear each other, or one-way video and two-way audio, where the audience sees and hears the presenter, and the presenter hears only the audience. During a video teleconference, audio, video, and data signals are transmitted to distant sites using a single combined channel, as in the use of a fiberoptic line or on separate channels. Audio is most often transmitted over a dial-up telephone line. The transmission channel can be analog or digital; signals can be sent via satellite, microwave, fiber optics, or coaxial cable, or a combination of these delivery systems.

The term video teleconferencing has become popular as an ad hoc one-time, special-event conference that usually connects a vast number of sites in order to make the conference cost effective. A video teleconference is usually distinguished from interactive instructional television (ITV), which is generally used to extend the campus classroom and carries programming for a significant length of time, such as a semester. ITV may use the same transmission channels as a video teleconference but is distinguished from video teleconferencing because of its different applications: video teleconferencing, an ad hoc conference, and ITV extending the classroom over a longer period of time.

Video teleconferences can be classified into two broad areas according to the technology used for transmission: full-motion video teleconferencing or compressed (or near-motion) video teleconferencing. Full-motion video teleconferencing uses the normal TV broadcast method or an analog video channel that requires a wideband channel to transmit pictures. The range of frequencies needed to reproduce a high-quality motion TV signal is at least 4.2 million Hz (4.2 MHz). The cost of a full-motion video teleconference is therefore extremely high. In the 1970s, conversion of the analog video signal to a digital bit stream enabled the first significant reductions in video signal bandwidth, making video conferencing less cost prohibitive.

Therefore, in compressed- video, full video information is compressed by a piece of technology known as a Codec, in order to send it down the narrower bandwidth of a special telephone line. The compressed video method is cheaper and more flexible than the TV broadcast method.

13.4.2.4. Full-Motion Video Teleconferencing. Full motion video teleconferencing became popular with the advent of satellite technology. For the past decade, educational developers have provided credit courses via satellite television over networks such as the National Technological University (for graduate engineering course), the Arts & Sciences Teleconferencing Service at Oklahoma State University, the TI-IN Network in Texas (for advanced placement high school courses). Both remote and urban schools and businesses have found these educational services valuable enough for their students and employees to make the investment in satellite hardware and tuition fees. Standard C- or Ku-band satellite TV signals can be received by consumer-level hardware costing well under $2,000. For a producer of educational programming, satellite delivery is still more economical than any other format for point-to-multipoint video transmission. Video compression standards and the introduction of fiber-optic cable infrastructure by many telephone and cable companies promises to make terrestrial line transmission of video much cheaper in the near future.

There are, however, at least two reasons that satellite television will probably remain available and, in fact, increase in the foreseeable future. First, there are still many remote areas of the world, even in North America, where telephone service, if it exists at all, is supported by antiquated technology barely able to provide a usable audio or data signal, let alone carry video. These remote areas simply need to point a relatively inexpensive satellite dish powered by solar panels, batteries, or generators-at the appropriate satellite to receive its signal. Additionally, new higher-powered satellites are making it unnecessary to use today's large unwieldy satellite dishes. The new generation of Ku-band satellite is already offering direct broadcast service (DBS) to European households. These receivers, known as VSATs (or very small aperture terminals), are no larger than I to 3 feet in diameter and currently cost less than $500.

The proliferation of smaller, less-expensive satellite television reception technology, along with the continued launching of new, higher-powered satellites, will ensure a continuing niche for this technology to deliver instructional video and data to even the remotest areas of the world that lack other information infrastructure.

Fiber optics is gaining in popularity as a transmission medium for video teleconferencing. Fiber optics is a transmission technology using an attenuated glass fiber hardly thicker than a human hair, which conducts light from a laser source. A single glass fiber can carry the equivalent of 100 channels of television or 100,000 telephone calls, and even more capacity is possible by encasing many fibers within a cable. Fiber optics offers several advantages: It can carry a tremendous amount of data at high transmission speeds; it does not experience signal degradation over distance as does coaxial cable; and it is a multipurpose system that can transmit video, audio, data, and graphics into the school through a single cable. A single fiber-optic cable can carry over a billion bits per second, enabling several video teleconferences to run simultaneously. Many companies, universities, and states in the United States are building fiber-optic transmission networks to carry voice, data, and video.

Video teleconferencing can also use digital or analog microwave systems or dial-up digital transmission lines. Current developments center on converging the different transmission channels and using a combination of telecommunications channels, satellites, fiber optics, microwaves, and coaxial cables to deliver full-motion video teleconferencing.

13.4.2.5. Compressed Video Teleconferencing. Videocompression techniques have greatly reduced the amount of data needed to describe a video picture, and have enabled the video signal to be transmitted at a lower and less expensive data rate. The device used to digitize and compress an analog video signal is called a video codec, short for COder/DEcoder, which is the opposite of a modem (MOdulator/DEModulator). Reduction of transmission rate means trade-offs in picture quality. As the transmission rate is reduced, less data can be sent to describe picture changes. Lower data rates yield less resolution and less ability to handle motion. Therefore, if an image moves quickly, the motion will "streak" or "jerk" on the screen.

Currently most compressed video systems use either T- I or half a T- I channel. In a T- I channel, video is compressed at 1.536 Mbps, which is the digital equivalent of 24 voicegrade lines. Many users of T- I codecs opt for transmission at 768 kbps, which is half a T- I channel. The difference in video quality between transmission at 768 kbps and 1.536 Mbps is slight, but the cost savings are significant. With the proliferation of fiber-optic networks, some private video teleconferencing networks are taking advantage of high-quality 45 Mbps transmission. Digital video compression technology has allowed video teleconferencing to become less cost prohibitive. It is not as cost effective as audio teleconferencing and audiographics teleconferencing, but it may soon compete with more-sophisticated audiographics systems with future developments in video compression technology.

13.4.2.6. Desktop Video Teleconferencing. Future developments in video teleconferencing will move toward integrated desktop video teleconferencing combining audio, video, and data. A fusion of network, personal computer, and digital video has produced the field of desktop videoconferencing. Saba (1993) observes that several telecommunications companies have introduced integrated systems (voice, video, and data) that reside in a desktop computer and provide two-way synchronous communications with voice, image, and file-transfer and screen-share capabilities. This technology allows users to see each other, speak to each other, transfer application files, and work together on such files at a distance. Most systems do not require advanced digital communications technologies such as ISDN to operate. For those wanting to utilize ISDN, it is possible to purchase an ISDN card, while most systems are now being designed to work with telecommunications standards such as ISDN.

Education can use this technology as a method of presenting class material and forming work groups, even though they may be at a considerable distance from each other. An instructor could conceivably present material to the entire class either "live" or through delivery of an audio file to each student's electronic mail account. Students could then work together in real time if they wished to share information over telephone lines.

In one current example, German officials are making use of desktop videoconferencing to form what has been dubbed a "virtual government." As planing progresses to move offices from Bonn, the current capital, to Berlin, planners meet regularly using on-line workstations rather than traveling to meetings. The results provide faster interaction at a much lower cost (Merwyn, 1993).

As more technologies begin to dovetail, desktop videoconferencing becomes laptop videoconferencing. The use of cellular telephone technology combined with high-speed laptop modems will make it possible for people to hold meetings and work group sessions whether they are at home, in an office, or on the beach.

13.4.2.7. Interactive Instructional Television (ITV). Interactive instructional television (ITV) systems usually use a combination of "instructional television fixed service" (ITFS) and point-to-point microwave. They can transmit either two-way video and two-way audio, or one-way video and two-way audio, to several distant locations. The advantage of combining ITFS and microwave is that microwave is a point-to-point system, while ITFS is a point-to-multipoint system. Therefore, large geographical areas can be covered by the combination of the two technologies. Microwave connects one location to another electronically with its point-to-point signals, while ITFS distributes that signal to several receiving stations around a 20-mile radius. In the U.S., several states such as Iowa and Oklahoma support statewide networks that use a combination of ITFS, raicrowave, satellite, fiber optics, and coaxial cable.

In an ITFS and microwave television system, the course delivered over the system originates from a "studio classroom" on the campus. The classroom is specially designed to facilitate the extension of a conventional class through television. The audio feedback permits interaction between the teacher and students at distant locations. If a student viewing the class at a remote location has a question, he or she asks it through a talkback system, and it is heard by both on-campus and off-campus class members. The talkback system uses either the telephone or FM microwave technology, called radio talkback.

Interactive instructional television systems also use satellite, fiber optics, or compressed video to extend the traditional classroom. However, these systems are currently not as cost effective as systems that comprise of ITFS and point-to-point microwave.

13.4.2.8. Integrated Services Digital Network (ISDN).ISDN is a new international telecommunications standard that offers a future worldwide network capable of transmitting voice, data, video, and graphics in digital form over standard telephone lines or fiber optic cable. ISDN transmits media using digital rather than analog signals. In order to move toward a global network, ISDN promises end-to-end digital connectivity, multiple services over the same transmission path and standard interfaces or conversion facilities for ubiquitous or transparent user access. Saba (1988) points out ISDN's applications for distance education: convergence, multitasking and shared communications. Convergence refers to the convergence on audio, video and data media in an integrated telecommunication system. Instruction is possible through voice, data, graphics, and video images. Multitasking refers to the variety of telecomputing capabilities that are available to the learner through integrated telecommunication systems that are based on minicomputers or microcomputers. Learners can gain access to online databases worldwide, and explore multimedia libraries comprising of digital sound, text and images. The shared communications feature allows the teacher and a group of learners separated by distance to work interactively on the same screen, sharing graphics, text, or data at the same time. Therefore, it is possible to solve a problem together or draw a graphic together even though a group of learners may be at different geographic locations. Currently available audiographics systems and desktop video teleconferencing systems provide for the features that will be available in a more user friendly and cost effective manner with the development of ISDN systems.

13.4.2.9. Broadcast Television and Radio. Broadcast television (see 11.7) and radio (see 28.1.6.1) fall under the classification of same-time/different-place instruction. The difference between broadcast television and radio and the previously discussed technologies under the same category is that broadcast television and radio do not provide for real-time, two-way interaction between presenters and participants. These media, however, can be used to instruct a vast number of students at the same time, even though the students do not have the ability to call back and clarify a statement or ask a question in real time. Many distance education institutions in developing countries, as well as institutions in developed countries such as the British Open University, use broadcast television and radio extensively to deliver programming to a large number of distant learners.

In the United States, while television-both open broadcast cable and ITV-is the most popular media for delivering distance education, radio remains an underutilized medium (Gunawardena, 1988). It is in the developing countries that radio programming has been produced to either support and supplement print-based materials or to carry the majority of the course content.

In the United States, the most common pattern of open broadcast use for delivering distance education is for an institution to make arrangements with the Public Broadcasting Service (PBS) and/or a commercial television station to distribute the educational programming (see 11.7). One of the limitations of this type of distribution is that educational programming is confined to broadcast schedules predetermined by the broadcasting station, which may not be times convenient for students taking the course.

Bates (1984) observes that broadcasts are ephemeral, cannot be reviewed, are uninterruptable, and are presented at the same pace for all students. A student cannot reflect on an idea or pursue a line of thought during a fast-paced program without losing the thread of the program itself. A student cannot go over the same material several times until it is understood.

Therefore, it is difficult for the learner to integrate or relate broadcast material to other learning. Hence, the need for broadcast programming to be accompanied by support materials in the form of prebroadcast notes and follow-up exercises and activities. Research at the British Open University has indicated that "most students find it impossible to take notes while viewing, and those that do are usually very dissatisfied with their notes" (Bates, 1983, p. 61). Access to a videotape of the broadcast, however, will alleviate these problems by giving the learner control over the medium, with the ability to stop and rewind sections that were not clear.

Despite its ability to reach a large section of the student population, open-broadcast television is a one-way communication medium. It does not provide for interaction ,(two-way communication) between the student and the teacher and lacks flexibility and ability to respond to student feedback. Since students cannot question the instructor to clarify problems, and since professional broadcast production "makes the learner dependent on 'responsible' broadcasting" (Bates, 1983, p. 61), this system of distribution can encourage passive acceptance of the instruction. To make the system interactive, open-broadcast distribution requires an added system to provide either an audio or audio-video return circuit.

13.4.2.10. Cable Television. In the United States, cable television began in remote rural areas, expanded into the suburbs, and has now penetrated into large urban areas. Cable has evolved from a way of improving reception in rural areas to a technology capable of providing many channels and even two-way video communication. Microwave relays have enabled cable operators to pick up signals from television stations too distant to be picked up over the air. Satellite interconnection of cable systems makes possible the importation of programming from virtually any part of the world. Today, cable technology is readily available and reaches a large number of homes and apartment units in the United States.

Where cable can provide access to a large section of the population of a given geographic area, it can be used to distribute distance education. Cable can be used to replay Programming offered over open-broadcast television, usually at more convenient times for the students than open-broadcast schedules, or used as a means of delivering nationally distributed television programs, where terrestrial broadcasting facilities are not available.

Interactive cable in most cases is not two-way video. It is one-way video with telephone feedback from the viewer to the instructor, or a technology that provides viewers with one-way video and one-way audio feedback combined with keypads or polling devices with which they can transmit impulses to a central computer in response to questions posed by the instructor. Student responses, such as "yes," "no," "do not understand," "slow down," etc., are immediately summarized by a central computer for the instructor, and often for the viewing audience, thereby adding an element of interaction to the experience.

13.4.3 Different Time/Same Place Instruction

This type of instruction usually takes place in a lab or study center where distance learners gather at different times to interact with instructors, tutors, and other students. Certain types of instructional objectives can only be successfully met by arranging for learners to conduct an experiment in a lab and observing this experiment for evaluation purposes. Local study centers are used by major distance teaching universities such as the British Open University to support the distance learner by offering meetings with tutors, discussion with peer groups, and library facilities. A survey of distance teaching institutions in the United States (Gunawardena, 1988) found that only 41% of the total number of institutions surveyed used local study centers. The types of services provided by most of the institutions were student access to media equipment such as videocassette players and microcomputers, and library facilities such as books, tapes, and cassettes, rather than arrangements for tutor-student interaction.

13.4.4 Different Time/ Different Place Instruction

The technologies used in this category are further classified as those that transmit one-way information such as print, audio- and videocassettes, and those that provide for interaction. Technologies that provide for interaction are divided into two groups: (1) those that permit interaction between the instructor and the learner, and among groups of learners such as computer-mediated communication (CMC) (see Chapter 14); and (2) those that provide learner-machine interaction as in computer-assisted instruction (CAI)/ computer-based training (CBT) (see 12.2.3) and interactive video and videotex. CAI/CBT, interactive video., and videotex are highly individualized learning experiences that can be designed to give learners control over their learning. Since the technologies that provide learner-machine interaction are discussed elsewhere in this book, they will not be discussed in this chapter.

13.4.4.1. Print. Until the beginning of the 1970s and the advent of two-way telecommunications technologies, print and the mail system were the predominant delivery medium for distance education. Correspondence study relied primarily on print. to mediate the communication between the instructor and the learner. Currently, many distance education institutions in developing countries use print-based correspondence study as the main distance education medium, as the use of communications technologies is often cost prohibitive. Garrison (1990) refers to print-based correspondence study as the first generation of distance education technology. It is characterized by the mass production of educational materials, and Peters (1983) describes it as an industrial form of education. The difficulty with correspondence education has been the infrequent and inefficient form of communication between the instructor and the students. Also, it was difficult to arrange for peer interaction in correspondence-based distance education. The development of broadcast technologies and two-way interactive media have mitigated the limitations of correspondence study, especially in relation to facilitating two-way communication. However, print remains a very important support medium for electronically delivered distance education. Printed study guides have become a very important component of electronic distance education. In a survey of distance teaching institutions in the United States that use television as a main delivery medium, Gunawardena (1988) found that a majority of institutions cited the study guide, which provides printed lesson materials and guidelines for studying, the most important form of support for distance learners. A study guide can steer and facilitate the study of correspondence texts, television programs, and other components in a distance education course. A study guide, if well designed, can provide the integration between various media components and activate students to read and or listen to presentations of various kinds, to compare and criticize them, and to try to come to conclusions of their own. In a study guide or correspondence text, simulated conversation can be brought about by the use of a conversational tone, advance organizers, mathemagenic (see 30.4, 30.6) devices such as directions, and underlining, self-assessment, and self remediation exercises.

13.4.4.2. Audiocassettes. Audiocassettes afford the learner control over the learning material, because learners can stop, rewind, and fast-forward the tape. They offer great flexibility in the way they can be used, either at home or while driving a car. Since audiocassettes are a fairly cost-effective medium, they are easily accessible to students. Audiocassettes can be used to tape lectures or can be specially designed with clear stopping points in order to supplement print or video material. For example, in order to facilitate student learning, audiocassettes can be used to describe diagrams and abstract concepts that students encounter in texts. An audiocassette can be used to record the sound portion of a television program if a videocassette recorder is not available, and an audiocassette can provide a review of a television program in order to assist students to analyze the video material. The audiocassette can also be used to provide feedback to student assignments and is a very useful medium to check student pronunciation when languages are being taught at a distance. Audiocassettes can be an excellent supplementary medium to enrich print or other media and can provide resource material to distance learners. Since they can be produced and distributed without much cost, audiocassettes are also a very cost-effective medium for use in distance education.

13.4.4.3. Videocassettes. Videocassettes are like broadcast television in that they combine moving pictures and sound, but unlike broadcast television, videocassettes are distributed differently and viewed in different ways. An institution using videocassettes for distribution of video material to distant learners can use them as (a) a copy technology for open-broadcast, satellite, or cablecast programming; (b) a supplementary medium, for instance, providing the visual component for educational material carried over audio teleconferencing networks; (c) a specially designed video program that takes advantage of the cassette medium, e.g., its stop/review functions, so that students can be directed at the end of sequences to stop and take notes on, or discuss, what they have seen and heard.

An important advantage in using videocassettes is that students can exercise "control" over the programming by using the stop, rewind, replay, and fast-forward features to proceed at their own pace. Videocassettes are also a very flexible medium allowing students to use the cassettes at a time that is suitable to them. Bates (1987) observed that the "videocassette is to the broadcast what the book is to the lecture" (p. 13).

If videocassettes are designed to take advantage of their "control" characteristics and students are encouraged to use the "control" characteristics, then there is opportunity for students to interact with the lesson material. Students can repeat the material until they gain mastery of it by reflecting on and analyzing it. The control features that videocassettes afford the learner give course designers the ability to integrate video material more closely with other learning materials, so that learners can move between lesson material supplied by different media. "The ability to create 'chunks' of learning material, or to edit and reconstruct video material, can help develop a more-questioning approach to the presentation of video material. Recorded television therefore considerably increases the control of the learner (and the teacher) over the way video material can be used for learning purposes" (Bates, 1983, pp. 61-62).

Bates (1987) discusses the implications of the "control" characteristics for program design on videocassettes: (a) use of segments, (b) clear stopping points, (c) use of activities, (d) indexing, (e) close integration with other media (e.g., text, discussion), and (f) concentration on audiovisual aspects.

When videocassettes are used in a tutored video instruction (TVI) program, where tutors attend video-playback sessions at workplaces or study centers to answer questions and to encourage student discussion, students can take advantage of the features of a lecture (on videocassette) and a small-group discussion, which gives them the opportunity for personal interaction available in on-campus instruction.

13.4.4.4. Computer-Mediated Communication (CMC). CMC supports three types of on-line services: electronic mail (e-mail), computer conferencing, and on-line databases (see Chapter 14). In e-mail systems, a message is routed by the system to the addressee's mailbox on the host computer and remains there until it is read by the addressee. This message can be read, replied to, left in the mailbox for later perusal, saved to the hard disk on the microcomputer, deleted, or forwarded to someone else. Most e-mail systems have a bulletin board feature that allows users to read and post messages and documents to be seen by all. However, the messages in the bulletin board system are not linked to each other and provide for only a very limited form of group communication.

Computer conferencing systems, on the other hand, provide a conferencing feature in addition to e-mail, which supports group and many-to-many communication. In these systems, messages are linked to form chains of communication, and these messages are stored on the host computer until an individual logs on to read and reply to messages. Most conferencing systems offer a range of facilities for enhancing group communication and information retrieval. These include directories of users and conferences, conference management tools, search facilities, polling options, cooperative authoring, the ability to customize the system with special commands for particular groups, and access to databases (Kaye, 1989). Databases can be made available on the same host computer used for an e-mail or computer conferencing system, or users can access public or private databases resident on other computers. Some of the well-known computer conferencing systems are: EIES, PARTI, CAUCUS, CONFER, COSY, VAX NOTES, and TEAMATE. Recent developments in groupware, the design of software that facilitates group processes especially in the CMC environment, will have a tremendous impact on facilitating group work between participants who are separated in time and place.

The key features of computer conferencing systems that have an impact on distance education are the ability to support many-to-many interactive communication and the asynchronous (time-independent) and place-independent features. It offers the flexibility of assembling groups at times and places convenient to participants. The disadvantage, however, is that since on-line groups depend on text-based communication, they lack the benefit of nonverbal cues at facilitate interaction in a face-to-face meeting. Levinson (1990) notes that research into education via computer conferencing must be sensitive to the ways in which subtle differences in the technology can impact the social educational environment. "The importance of social factors suggests that 'computer conferencing' may be a better name for the process than is 'computer-mediated communication'; the term 'conferencing' accentuates the inherent 'groupness' of this educational medium" (p. 7). Harasim (1989) emphasizes the necessity to approach on-line education as a distinct and unique domain. "The group nature of computer conferencing may be the most fundamental or critical component underpinning theory building and the design and implementation of on-line educational activities" (p. 51). Gunawardena (1993) reviews research related to the essentially group or socially interactive nature of computer conferences, focusing on factors that impact collaborative learning and group dynamics.

Globaled, a project that linked graduate classes in six universities-San Diego State University, Texas A&M University, University of New Mexico, University of Oklahoma, University of Wisconsin-Madison, and the University of Wyoming-to engage in the discussion of research related to distance education, is an example of the potential of computer conferencing to link students and instructors in learning communities (Gunawardena, Campbell Gibson, Cochenour, Dean, Dillon, Hessmiller et a]., 1994). While the six major participating universities conducted research projects and moderated the discussions of their findings on Globaled, several interested students and faculty from other U.S. and overseas universities, including the Pennsylvania State University and the University of Wollongong in Australia, participated in the discussions. The Globaled community had approximately 90 participants. Globaled was premised on a learner-centered collaborative learning model in which the learner would be an active participant in the learning process involved in constructing knowledge through a process of interaction and discussion with learning peers and instructors.