Teleconferencing means meeting through a telecommunications medium. It is a generic term for linking people between two or more locations by electronics. There are at least six types of teleconferencing: audio, audiographic, computer, video, business television (BTV), and distance education. The methods used differ in the technology, but common factors contribute to the shared definition of teleconferencing:


    • Use a telecommunications channel
    • Link people at multiple locations
    • Interactive to provide two-way communications
    • Dynamic to require users' active participation


Interactive Technologies

The new systems have varying degrees of interactivity - the capability to talk back to the user. They are enabling and satellites, computers, teletext, viewdata, cassettes, cable, and videodiscs all fit the same emerging pattern. They provide ways for individuals to step out of the mass audiences and take an active role in the process by which information is transmitted. The new technologies are de-massified so that a special message can be exchanged with each individual in a large audience. They are the opposite o mass media and shift control to the user.

Many are asynchronous and can send or receive a message at a time convenient for individuals without being in communication at the same time. This overcomes time as a variable affecting communication. A video, data and voice delivery system reduces travel costs. When the material is retrieved and saved to a video tape or disc, the material can be used at anytime or anyplace.

As more interactive technologies emerge, the value of being an independent learner will increase. Research shows that learning from new technologies is as effective as traditional methods. Large groups are cost-effective and everyone gets the same information.


Types of Teleconferences

Audio Teleconference: Voice-only; sometimes called conference calling. Interactively links people in remote locations via telephone lines. Audio bridges tie all lines together. Meetings can be conducted via audio conference. Preplanning is necessary which includes naming a chair, setting an agenda, and providing printed materials to participants ahead of time so that they can be reviewed.

Distance learning can be conducted by audio conference. In fact, it is one of the most underutilized, yet cost effective methods available to education. Instructors should receive training on how to best utilize audio conferences to augment other forms of distance learning.

Audiographics Teleconference: Uses narrowband telecommunications channels to transmit visual information such as graphics, alpha-numerics, documents, and video pictures as an adjunct to voice communication. Other terms are desk-top computer conferencing and enhanced audio. Devices include electronic tablets/boards, freeze-frame video terminals, integrated graphics systems (as part of personal computers), Fax, remote-access microfiche and slide projectors, optical graphic scanners, and voice/data terminals.

Audiographics can be used for meetings and distance learning.

Computer Teleconference: Uses telephone lines to connect two or more computers and modems. Anything that can be done on a computer can be sent over the lines. It can be synchronous or asynchronous. An example of an asychronous mode is electronic mail. Using electronic mail (E-Mail), memos, reports, updates, newsletters can be sent to anyone on the local area network (LAN) or wide area network (WAN). Items generated on computer which are normally printed and then sent by facsimile can be sent by E-Mail.

Computer conferencing is an emerging area for distance education. Some institutions offer credit programs completely by computer. Students receive texts and workbooks via mail. Through common files assigned to a class which each student can assess, teachers upload syllabi, lectures, grades and remarks. Students download these files, compose their assignment and remarks off-line, then upload them to the common files.

Students and instructors are usually required to log on for a prescribed number of days during the week. Interaction is a large component of the students' grades.

Through computers, faculty, students and administrators have easy access to one another as well as access to database resources provided through libraries. The academic resources of libraries and special resources can be accessed such as OCLC, ERIC, and Internet.

Administrators can access student files, retrieve institutional information from central repositories such as district or system offices, government agencies, or communicate with one another. Other resources can be created such as updates on state or federal legislation.

Video Teleconference: Combines audio and video to provide voice communications and video images. Can be one-way video/two-way audio, or two-way video/two-way audio. It can display anything that can be captured by a TV camera. The advantage is the capability to display moving images. In two-way audio/video systems, a common application is to show people which creates a social presence that resembles face-to-face meetings and classes and enables participants to see the facial expressions and physical demeanor of participants at remote sites. Graphics are used to enhance understanding. There are three basic systems: freeze frame, compressed, and full-motion video.

Video conferencing is an effective way to use one teacher who teaches to a number of sites. It is very cost effective for classes which may have a small number of students enrolled at each site. In many cases, video conferencing enables the institution or a group of institutions to provide courses which would be canceled due to low enrollment or which could not be supported otherwise because of the cost of providing an instructor in an unusual subject area. Rural areas benefit particularly from classes provided through video conferencing when they work with a larger metropolitan institution that has full-time faculty.

Through teleconferencing, institutions are able to serve all students equitably.


Why Use a Teleconference?

Videoconferencing increases efficiency and results in a more profitable use of limited resources. It is a very personal medium for human issues where face-to-face communications are necessary. When you can see and hear the person you are talking to on a television monitor, they respond as though you were in the same room together. It is an effective alternative to travel which can easily add up to weeks of non-productive time each year. With videoconferencing, you never have to leave the office. Documents are available, and experts can be on hand. A crisis that might take on major proportions if you are out of town, can be handled because you're on the job. Videoconferencing maximizes efficiency because it provides a way to meet with several groups in different locations, at the same time.

As the limited resource of funding has decreased, limited resources now include instructors, parking spaces and buildings. Students now include time as a limited resources. Teleconferencing enables institutions to share facilities and instructors which will increase our ability to serve students.


Move Information - Not People

Electronic delivery is more efficient than physically moving people to a site, whether it is a faculty member or administrator.

Save Time: Content presented by one or many sources is received in many places simultaneously and instantly. Travel is reduced resulting in more productive time. Communication is improved and meetings are more efficient. It adds a competitive edge that face-to-face meetings do not.

Lower Costs: Costs (travel, meals, lodging) are reduced by keeping employees in the office, speeding up product development cycles, improving performance through frequent meetings with timely information.

Accessible: Through any origination site in the world. Larger Audiences: More people can attend. The larger the audience, the lower the cost per person.

Larger Audiences: More people can attend. The larger the audience, the lower cost per person.

Adaptable: Useful for business, associations, hospitals, and institutions to discuss, inform, train, educate or present.

Flexible: With a remote receive or transmit truck, a transmit or receive site can be located anywhere.

Security: Signals can be encrypted (scrambled) when it is necessary. Encryption prevents outside viewers.

Unity: Provides a shared sense of identity. People feel more a part of the group...more often. Individuals or groups at multiple locations can be linked frequently.

Timely: For time-critical information, sites can be linked quickly. An audio or point-to-point teleconference can be convened in three minutes.

Interactive: Dynamic; requires the user's active participation. It enhances personal communication. When used well for learning, the interactivity will enhance the learning and the teaching experience.


Satellite Communications

Long distance telephone calls, national and international televised sporting events, and cable movie channels operate via satellites. Satellites have been used for years.

Geostationary Orbit: British physicist and science fiction writer, Sir Arthur C. Clarke, invented satellite communication in his 1954 paper Wireless World, which explained this east-west orbit, 22,300 miles above the equator; three satellites based in this orbit could provide world-wide communications. Today, many satellites are arrayed in the Clarke belt. To earth stations, they appear fixed in space.

Satellite Footprint: In geostationary orbit, communications satellites have direct line-of-sight to almost half the earth - a large "footprint" which is a major advantage. A signal sent via satellite can be transmitted simultaneously to every U.S. city. Many downlinks can be aimed at one satellite and each can receive the same program; this is called point to multipoint.

Transponders: Via an uplink, video, audio or data signals can be transmitted to a satellite transponder. There may be up to 40 transponders per satellite; each can amplify and relay signals to earth which are picked up by earth stations.

C/Ku-Band: Domestic communications satellites operate on two frequency ranges designated C- and Ku-band. Each requires specific electronic equipment. C-band is less expensive; operates at 4 kHz. Ku-band operates at 12 kHz. Some teleconferences are broadcast on both bands.

Receivers: Convert satellite signals into channels viewed (one at a time) on a TV monitor; designed to tune-in the format, bandwidth, and audio sub-carrier. Programs broadcast in code (encryption) are decoded at receive sites.

Basic Receivers: Lowest cost; limited (or manual) channel tuning capability; may use fixed antennas.

Multi-Format Receivers: Most versatile; adjusts for all broadcast formats; receive any satellite video program in six or more bandwidth selections, and two agile audio subcarrier switches; usually a motorized systems.

Fixed Position System: Low cost systems limited to reception from one satellite and one band.

Motorized System: Receives programs on different satellites by adjusting the dish position.

Automated Systems: Microprocessor controlled for instant movement to satellites (positions stored in memory).


International Satellite

Alpha Lyracom Space Communications/Pan American Satellite is the world's first private international satellite system. PAS-1 carries many specialized communications services including full and part-time video, low and high speed data, broadcast data and radio and business television to over 70 countries on three continents. It can be seen (received) by a 2.4 meter antenna. It has 18 C-band and six Ku-band transponders with a shared capacity that increases traffic.

PanAmSat handles all phases of an international broadcast as compared to INTELSAT (International Telecommunications Satellite Organization) where the customer must book the domestic and foreign half circuits and pay for each downlink. INTELSAT was established primarily to handle the PTT telephone transmissions, while PanAmSat was established to be easily accessible by distance education institutions and private enterprise. The FCC licenses PanAmSat transportables for years, as compared to the FCC special temporary authority (STA) license for INTELSAT. PanAmSat transportables can uplink from any location without a special license.

PanAmSat writes yearly contracts with customers. It does not charge for multiple downlinks. Time on PAS-1 books from between $960 to $2,400 per hour depending on the volume discount based on yearly usage. To book time on PAS-1, call the day-of-air or future event number, with the origination site, uplink, downlink sites, and conference time. PanAmSat handles the rest. By booking time through satellite brokers (EDS, PSN, Satellite Management International) ad hoc users can reduce time costs. PanAmSat is negotiating for three more satellites to be in place in 1994-95.


Compressed Video

Digital compression means that the codec compresses the video signal or data to a fraction of its original size so that the data rate is appropriate to transmit over low-cost terrestrial telephone lines or on a fraction of a satellite transponder. Codecs (COder/DECorder) compress the video and audio signal allowing it to be transmitted in a smaller bandwidth which reduces the cost of the transmission.

Standard transmission rates for video teleconferencing are multiples of 64 Kbs up to the T1 rate of 1.54 Mbs. Some codecs allow speed selection to match the circuit used. The speed selected is based on the content. When close to full motion video is needed, higher rates are needed.

T1 circuits connect PBXs to the telephone company's central office and can carry up to 24 voice channels at a lower cost than 24 voice circuits. A 56 Kb or 64 KBS codec operates in the range of one voice channel. A standard video signal digitized at 90 Mbs is comprised of about 1400 voice channels.


Freeze Frame Video

Freeze frame video uses telephone channels to transmit video information. Because of the narrow bandwidth, the image takes a few moments to reach the receive site where it appears on the TV as a still picture. The advantages are lower costs and flexibility in linking multiple sites. Slow scan systems are similar to freeze frame and the terms are often used synonymously.

Freeze frame technologies include a range of features; analog, digital, monochrome or color pictures, resolutions, transmission speeds, and extra memory. Newer models provide multiple send times to select the resolution and transmission time through digital circuits and compression coding. Some units transmit video information in digital format over a data circuit which reduces the transmission time to about nine seconds to a 56 kilobit link. Because of the faster transmission rates, many new freeze frame applications use data circuits.

Compressed video (near motion) and full-motion video differ; compressed video uses compression techniques to reduce channel bandwidth; images may not look as natural and may blur or lose background resolution. The advantage is that the significant reduction in bandwidth reduces costs. Compressed video uses a telephone data circuit - currently a T1 carrier or 1.5 or 3 megabits - to transmit video, voice and data. It reduces video information (NTSC Standard-color video) with a compression technique to eliminate redundant information and reduce the 100 million bits signal to 1.5 or 3 million bits.

Digital video signals are broken down into thousands of elements called pixels. Between frames, many are the same. A codec takes advantage of this duplication by sending complete information on the first pixel and a brief code to repeat the values. This reduces the information sent and the bandwidth required. Interframe coding for conditional replenishment compares the changes between two frames and transmits changes. Motion compensation predicts changes between frames and transmits only the difference. Software holds the compression algorithm which can be upgraded. The CCITT Px64 international standard requires rates to operate in multiples of 64.


Full-Motion Video

Standard TV signals are broadcast using a significant amount of the bandwidth of wideband channels - 4 to 6 megahertz for color analog - to send video, voice and data. Because of the large channel capacity, it transmits a picture with the full motion and resolution of broadcast TV. The bandwidth used is the digital equivalent of 80 Mbps or more which corresponds to a full satellite transponder or 1820 voice phone lines. This translates into high costs for signal transmission.


Compression for One-Way Video

Consumer application for compressed video systems use higher rates than two-way compressed video to achieve near-broadcast quality video image. A digitally compressed video signal can be broadcast over 1/20 of a regular transponder channel reducing costs to under $200 per hour.

One use of the technology is SKY PIX, a pay per view movie service based on a Compression Labs, Inc. codec marketed by NW Star Scan which offers viewers a choice of up to 40 movies. The picture quality is better than VHS transmission quality. Scientific Atlanta offers PrimeStar, a competing entertainment service, which transmits at a data rate of 4 to 4.5 Mbs. Using the same technology, they will offer B-Mac users compatibility with compressed video users at a lower price because the transmission uses a fraction of a regular transponder channel.

Compression Labs, Inc. has recently introduced the SpectrumSaver System which can broadcast a digital signal to a fraction of a satellite transponder. Because up to 15 or 18 signals can be carried on a transponder (depending upon the system configuration), the cost of satellite time is significantly reduced. The National Technological University (NTU) is using the system, as well as ITESM in Mexico. Each institution reports a savings of $1 million in satellite time during the first year of operation. The system is entirely digital.

Scientific Atlanta is about to bring its new digital satellite system to the market. This system is an upgrade to an existing Scientific Atlanta analog satellite system. As such, users will be able to broadcast in either analog or digital format.


Fiber Optic Systems

The transmission of voice, video and data by light wave signals inside a thin, transparent glass fiber cable, is providing more choices for telecommunications users and is rapidly bringing digital communication to the home and office. One pair of fibers can carry up to 10,000 telephone calls simultaneously. Advantages: transmission clarity, speed, accuracy, security, and volume. Disadvantages: Construction, installation and maintenance costs, but they are declining.

from "The Distance Learning Technology Resource Guide," by Carla Lane