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Audioconferencing
Audioconferencing is two-way voice communication between two or more groups or three or more individuals in separate locations. The two types of telephone formats currently used are analog and digital. Analog has been the traditional means of telephone communication, with the information encoded as a continuous electronic wave. On the other hand, digital is presented in discrete binary signals that enable faster switching and have the capacity to simultaneously transmit voice, data, and compressed video signals over the same line. When more than one person is in a single location, speakerphones or special audioconference terminal equipment should be used to reduce echo and other interference. When more than two locations are involved, multipoint network bridging equipment is used.
Components of an audioconferencing system include: 1) telephone handsets, speakerphones, or microphones; 2) an audio bridge that interconnects multiple phone lines and controls noise; and 3) a speaker device to facilitate multiple interactions. Institutions without an on-site bridge, may wish to use a bridging service. For more information you should contact your local phone company.
While audioconferencing is not as "glitzy" as some computer applications, it is a low cost, low tech solution that allows easy entry to distance education and does not require special technical skills or a technician. Telephones are ubiquitous, easy to use, familiar and comfortable with a minuscule learning curve that allows many people to interact in real-time and to build a sense of community and sharing in a familiar environment. While there may be some difficulties with participants occasionally speaking over each other, audioconferencing is certainly worth investigating as part of a total delivery package. As Moore (1994) states, "Audioconferencing is a learner-centered, relatively inexpensive, robust, and flexible medium that can be well integrated with other media in a distance program" (p.1).
Videoconferencing
Videoconferencing is electronic voice and video communication between two or more groups or three or more individuals. It can be fully interactive two-way voice and video, or two-way audio and one-way video. Pacific Bell, Education First Applications Design Team has a comprehensive list of videoconferencing information and resources to help teachers and librarians use videoconferencing effectively. To find videoconferencing sites contact the International Teleconferencing Association at 703-560-3280 for their directory of videoconferencing rooms. Also, VTEL Corporation recently launched its new and improved site featuring a wealth of information on videoconferencing and the videoconferencing industry. This information ranges from white papers on standards (T.120 and H.320) and worldwide organizations focused on interactive videoconferencing, to discussions on specific applications like distance learning and telemedicine.
Two-Way Video
This system comes the closest to bringing teacher and remote student into the same classroom. This feat is usually accomplished using digital transmission systems, such as digital telephone lines (ISDN or Switched 56) or fiber optics, although microwave and satellite may also be used. A Coder/Decoder (CODEC) is used to digitize the audio and video to send over the digital telephone line. The CODEC also converts the incoming audio and video from digital to analog. The CODEC compresses the data to fit the transmission system being used. For more information visit University of Wisconsin Extension Distance Learning Glossaries.
Each site in a two-way video system is equipped with a camera, microphones and monitors. When using a videoconferencing system such as CU-SeeMe each site may use a very small, inexpensive camera that sits on top of a computer. Activities at each site are transmitted simultaneously, so teachers and students across a wide area can see and hear each other "live".
Traditional two-way video can be very expensive. For instance, if transmission is by microwave and the terrain is rough or if there are weather difficulties, costs will rise. Newer, Internet-based videoconferencing systems may be less expensive.
One-way Video
One-way video with audio return resembles traditional educational television, except that students can interact with the teacher and students at other sites by telephone (audioconference) or fax. Common transmission systems include satellite and ITFS (Instructional Television Fixed Service). The students at remote sites can see the teacher on their television monitor, but the teacher cannot see them. Students may ask questions by phone, fax, or FM radio during class and sometimes by e-mail. Both the inquiry and the teacher's answers may be broadcast, although the large networks that distribute courses nationally use teaching assistants to help handle the large volume of student questions. The system can gain increased interactivity by faxing materials and using other computer enhancements. With its visual component, one-way TV can work effectively for large-group instruction featuring teacher presentations as well as small-group instruction.
Instructional Television Fixed Service (ITFS) is a terrestrial microwave distribution system in which an omnidirectional transmission tower is positioned on high ground in direct line-of-sight of sending and receiving locations (Weinstein, 1986). For this reason, ITFS is limited to locations within close geographic proximity, and without fog. Satellite delivery equipment includes a satellite (device orbiting the earth), an uplink antenna, and a Television Receive Only (TVRO) downlink station. Satellite transmission covers any space within an electronic "footprint". It costs as much to transmit to one site as to transmit to one hundred sites; transmission costs do not increase with the number of receive sites. However, satellite technology is complex, requiring a considerable capital investment and full-time technical personnel.
Compressed video is analog video signal converted into digital signal. The digitized signal is then transmitted along a narrower bandwidth, allowing many digital signals in the space of one analog signal. Therefore, compressed video provides a cost-effective delivery alternative. However, during compression the quality of the visual image is altered. This alteration may be more acceptable when crisp detail and full motion are not essential.
Computerconferencing
Computerconferencing is the use of electronic channels to facilitate communication among groups of people at two or more locations via computer. Therefore, computerconferencing includes IRC (Interactive Relay Chat), MOO (Multi-user Object Oriented), and MUD(Multi-User Domain) as well as videoconferencing systems such as CU-SeeMe.
For more information and current discussions on Computer Mediated Communication visit the CMC Magazine.