A Teacher's Guide to Distance Learning
The ability to see and hear an instructor offers opportunities for behavior modeling, demonstrations, and instruction of abstract concepts. Video techniques for distance learning are often characterized by the transmission media (videotapes, satellites, television cables, computers, and microwave). Each of the media can be described as it relates to the direction of the video and audio signals -- one-way video; two-way video; one-way audio; and two-way audio (see Figure 15).
Figure 15. Three audio and video configurations.
Videotapes
Videotapes offer a popular, easy-to-use format for instructional materials. Almost all students have access to a videotape player in the homes, and they are also common at school. Videotapes can be used for demonstrations or documentaries. In addition, it is quite easy to videotape a lecture for a student who is unable to attend class. Videotapes have several advantages for the delivery of distance learning. In addition to easy access to the hardware, the tapes are quite inexpensive. If a video camcorder is available, videotapes are relatively easy to record (although professional staff and equipment provide in a much better product than will an amateur production team). Disadvantages of videotapes include the fact that they are not interactive. In addition, they wear out with continual use and can be costly to send via the mail.When using videotapes for instruction, be sure to record them using the best equipment available. If possible, employ professional videographers and editors to achieve professional quality. Interactions through voicemail, e-mail, fax, or other means should also be encouraged.
Satellite Videoconferencing
Full-motion video teleconferencing (referred to as videoconferencing) offers the "next best thing to being there." Satellite transmission is one of the oldest, most established techniques for videoconferencing. In most cases, satellite delivery offers one-way video and two-way audio.Two sets of equipment are needed for satellite systems. The uplink (a large satellite dish) transmits the video and audio signals to the satellite. The downlink (a small dish antenna) receives and displays the signals (see Figure 16).
Figure 16. Configuration for satellite videoconferences.
When satellite videoconferences are used for distance learning, a studio classroom must be properly wired for the lighting, microphones, and cameras needed to produce an acceptable lesson. The cameras are usually connected to a control room, where one or more technicians control the signals. The resulting television signal is then sent to the uplink transmitter. Uplink transmitters are very expensive and are often shared with other schools or businesses.
The receiving sites of satellite videoconferences (in most cases other schools) must have satellite downlinks. These dishes select, amplify, and feed the signals into the classrooms, where they can be displayed on standard television monitors. To provide two-way audio with interactions from the remote classrooms back to the teacher, a telephone bridge is usually employed.
Satellite videoconferencing is very expensive. It would not be cost-effective for most school systems to use uplinks to originate distance-education classes unless the school systems were in a position to market the classes over wide geographic areas. It is reasonable, however, for a school to use a downlink to receive commercial courses that are delivered through satellite channels. One example of an educational system that makes use of satellite communication is EMG (Educational Management Group).
Microwave Television Conferencing
Satellites are a popular method for enabling video communications over long distances. Microwave transmissions provide a cost-effective method for videoconferencing in more localized areas. Most microwave systems are designed to transmit video signals to areas that are not more than 20 miles apart (see Figure 17).
Figure 17. Configuration for microwave transmission.
The most common microwave systems use frequencies that have been designated by the Federal Communications Commission (FCC) as Instructional Television Fixed Service (ITFS) stations. When compared with satellite or commercial broadcast television, ITFS stations operate at a lower power, and the transmission equipment is relatively inexpensive. Reception equipment is also reasonably priced, as long as the receiving sites are located within 20 miles of the transmitter and there are no hills or tall buildings to block the line-of-sight signal.
One drawback of microwave ITFS communication involves the limited number of channels available in any one area. Many metropolitan areas already have all available channels in use, so no further expansion of ITFS teleconferencing is possible in these areas.
Cable and Broadcast Television
Cable and public broadcast television have been used to distribute instruction for years. In addition to the educational networks, such as CNN, the Learning Channel, and Jones Computer Program, almost all public cable television systems allow schools to transmit television courses. This type of connection can be used to transmit one-way video and one-way audio to the community at large or between specific schools. For example, if two area high schools do not each have enough students to justify an advanced math course, they might team up to teach a single course delivered through cable television. In one school, the teacher would conduct a regular class; in the other school, the students would watch and listen through a standard cable television channel.Distance learning through cable television systems requires both a studio and channels through which to broadcast. The cost depends largely on the "partnership" offered by the cable or broadcast system. Even though the broadcast will take place at a scheduled time, research shows that the majority of the students will tape the program and play it back at a convenient time.
Cable companies will soon be able to use the technology of digital video to offer hundreds of channels to each home and school. Although many of these channels will be used for commercial entertainment purposes, it is almost certain that a large number of channels will become available for education.
Digital (Desktop) Videoconferencing
Desktop videoconferencing uses a computer along with a camera and microphone at one site to transmit video and audio to a computer at another site or sites. The remote sites also transmit video and audio, resulting in two-way video and two-way audio communications.With digital videoconferencing, all of the computers involved must have a videoconferencing board installed. These boards often have the ability to compress and decompress the digitized video, and they are called codec boards (see Figure 18). PictureTel and Vtel are two well-known hardware/software companies that supply desktop video solutions for schools.
Figure 18. Configuration for desktop videoconferencing.
Although desktop videoconferencing is considerably less expensive than satellite or microwave systems, there are a couple of limitations. First, the images are usually transmitted at 15 images per second, half the normal video speed. This causes the video to appear somewhat jerky if any rapid motion takes place. A second concern is related to the connection between the computers. Most systems have been demonstrated either through local area networks (LANs) or through relatively fast connections, such as ISDN or T1 lines. Slower connections, such as a connection with a 28.8 modem, can negatively affect the quality of both audio and video.
Internet Videoconferencing
It is also possible to conduct videoconferences over the Internet. Two popular software programs that allow videoconferences are CUSee-Me from Cornell University and NetMeeting from Microsoft. In both cases, you need a video camera and digitizing card to transmit video signals. A microphone, speakers (or headset) and an audio card are required for audio (see Figure 19).
Figure 19. Configuration for Internet videoconferencing.
Internet videoconferencing usually results in a small image about 1/16th the size of a computer screen. The video is generally jerky (about 3 or 4 frames per second), depending on the speed of the Internet connection. In most cases, a regular modem is far too slow to transmit effective video.
While all of this sounds very exciting, it is still very early in the development process. The images that are produced by products like CU-SeeMe are extremely low in quality, and can not be used for many instructional purposes. With luck, it is possible to identify an individual if he or she fills the entire window, but even then, there may be poor synchronization between lips and sound.
Advantages of Video Technologies
- Allow both audio and video communications.
Video technologies can provide the visual and audio realism of a face-to-face class. It is generally considered the "next best thing to being there."
- Facilitate personal feelings.
Video technologies enable students and instructors to see facial expressions and body language, adding personalities to communication.
- Enable high levels of interaction. Most video communications are synchronous, allowing high degrees of interactions, questions and answers, etc.
Disadvantages of Video Technologies
- May be expensive.
Cameras and editing equipment can be expensive. In addition, the infrastructure at each site and the links between sites can be costly. For example, in Florida the rate is $400 per hour for satellite time.
- Require a great deal of planning and preparation.
To be effective, the camera crews and the instructor must practice and become a team. Faculty members generally need practice and training to be effective in this domain.
- Must be scheduled.
Most videoconferences are not spontaneous. Instead, they must be planned and the necessary resources must be scheduled.
- Require technical support team. Because of the complexity of video recording, mixing, and transmission, a technical support team is required. In addition, site facilitators are necessary to ensure the equipment works properly at the receiving stations.
Guidelines for Incorporating Video Technologies
- Avoid the "talking head."
"The early days of distance education witnessed the inclusion of the worst aspects of the old passive/lecture paradigm, which were even more deadly from a distance than in person" (Parker, 1997, 10). Talking head refers to simply videotaping the instructor while she or he is talking. Instead, try to vary the camera angle, include still images of appropriate graphics, and encourage student interactions.
- Practice with the cameras and the crew before the lesson.
It is important to plan practice times for the instructor and the camera crew. By working together, they can anticipate each other's needs and provide the best possible transmissions.
- Encourage interactions.
Interactions can be added to video-based delivery in many ways. If the lessons are two-way, questions and other types of interactions can be included. If they are one-way video, interactions can be added through e-mail messages or the telephone.
- Use the best cameras possible.
The old saying "garbage in; garbage out" is very true of video. The very best possible quality equipment should be used.
- Ensure quality audio. Losses in audio quality will be noticeable long before losses in video quality. Always ensure good recording, playback, and speaker quality.
Summary of Distance Learning Technologies
The following table summarizes the advantages and disadvantages of the major distance learning technologies.
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Produced by the Florida Center for Instructional Technology,
College of Education, University of South Florida © 1998, 1999.