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
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
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
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.
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.
Through any origination site in the world. Larger Audiences:
More people can attend. The larger the audience, the lower the
cost per person.
More people can attend. The larger the audience, the lower cost
Useful for business, associations, hospitals, and institutions
to discuss, inform, train, educate or present.
With a remote receive or transmit truck, a transmit or receive
site can be located anywhere.
Signals can be encrypted (scrambled) when it is necessary. Encryption
prevents outside viewers.
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.
For time-critical information, sites can be linked quickly. An
audio or point-to-point teleconference can be convened in three
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.
Long distance telephone calls, national
and international televised sporting events, and cable movie
channels operate via satellites. Satellites have been used for
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.
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.
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
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.
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.
Receives programs on different satellites by adjusting the dish
Microprocessor controlled for instant movement to satellites
(positions stored in memory).
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.
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.
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
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