Glossary of Selected Distance
Learning Terms and Phrases
Analog Communication. A
communication format in which
information is transmitted by
modulating a continuous signal, such as
a sound wave. Current TV and radio
signals are analog, as are many
telephone lines. See also Digital
Communication.
ASCII. American Standard Code
for Information Interchange. Standard 8
bit code used in data communications.
Many files interchanged from one
software program to another and from
IBM to Mac formats go through
translation into ASCII.
Asynchronous. A type of
two-way communication that occurs with
a time delay, allowing participants to
respond at their own convenience.
Literally not synchronous, in other
words, not at the same time. Example of
an application of asynchronous
communication is electronic bulletin
board.
Asynchronous Transfer Mode
(ATM). Communication technology
that uses high-bandwidth, low-delay
transport technology, and multiplexing
techniques. Through dedicated media
connections it provides simultaneous
transport of voice, video, and data
signals more than 50 times faster than
current technology. May be used in
phone and computer networks of the
future.
Audio Bridge. Specialized
equipment that interconnects three or
more telephone lines (usually operator
assisted) to enable conference calls.
The audioconferencing equipment needed
to connect multiple sites can be
provided by companies specializing in
bridge services.
Audioconference. An
electronic meeting in which
participants in different locations use
telephones or audioconferencing
equipment to interactively communicate
with each other in real time. The
number of participants may be as small
as 3 or as large as 100 or more.
Authoring Software/Tools.
High level computer programs designed
for use by non-programmers in the
creation of computer-based training,
interactive presentations, and
multimedia. The commands are presented
as simple terms, concepts, and icons.
The authoring software translates these
commands into the programming code
needed by the computer and related
hardware devices.
Bandwidth. Maximum frequency
that can be used to transmit a
communication signal without excessive
distortion. Measured in Hertz or cycles
per second. The more information
contained in a signal, the more
bandwidth it requires for
distortion-free transmission.
Baud Rate. The transmission
rate at which data flows between
computers. The baud rate is roughly
equivalent to the number of bits per
second (bps).
Bit (binary digit). The
smallest unit of information a computer
can use. A bit is represented as a "0"
or a "1" (also "on" or "off"). A group
of eight bits is called a byte. Bits
are often used to measure the speed of
digital transmission systems.
Bitnet. An academic and
research computer network that stores
and forwards messages sent between
users. This system was a precursor to
the Internet and its use today is
limited.
Browser. Software that allows
you to "surf " the Internet. Netscape,
Mosaic, and Internet Explorer are
examples of Web browsers. A browser
provides an easy to use interface for
accessing the information on the World
Wide Web.
Cache. Memory that holds
copies of recently accessed data.
Several Web browsers keep recently
viewed pages in a cache so users can
return to them quickly without
suffering network delays.
Computer-assisted Instruction
(CAI). See Computer-based Training
(CBT).
C-band. A type of satellite
transmission with less path loss than
other satellite standards such as
Ku-band. C-band, however, requires a
relatively large antenna. C-band
frequencies are shared with terrestrial
microwave transmissions, which can
cause interference with weaker
satellite signals in certain areas.
Chat. Two or more individuals
connected to Internet have real-time
text-based conversations by typing
messages into their computer. Groups
gather to chat about various subjects.
As you type, everything you type is
displayed to the other members of the
chat group.
Codec. Coder/decoder
equipment used to convert and compress
analog video and audio signals into a
digital format for transmission, then
convert them back to analog signals
upon reaching their destination.
Compact Disc (CD). High
density storage media based on a 4.75"
reflective optical disc. Can hold up to
650,000,000 bytes of data, that is
equivalent to 12,000 images or 200,000
pages of text. CDs may all look the
same, but there are numerous standards
for different applications. The most
common are defined below.
Compact Disc-Interactive
(CD-I). Interactive multimedia
platform developed for the consumer
market by Philips. It is a proprietary
version of the CD-ROM that delivers
data, text, audio, stills, and
video.
Compact Disc Read-Only Memory
(CD-ROM). Version of the CD that
allows the information to be stored and
retrieved. Once a CD-ROM is pressed,
new data cannot be stored and the disc
cannot be erased for reuse. Although
CD-ROMs look like music discs, they can
only be used with a computer equipped
with a CD-ROM drive.
Compact Disc-Recordable
(CD-R). CD-ROM recording systems
can be used to record data onto a
compact disc-recordable like any other
recordable media. However, they cannot
be erased and re-recorded. For
large-scale duplication of CD-ROMs, a
pressing facility is preferred.
Compressed Video. A digital
transmission process used to transmit a
video signal. When the vast amount of
information in a video transmission is
compressed into a fraction of its
former bandwidth by a codec, the
resulting compressed video can be
transmitted more economically and
through existing phone lines. While
compressed video requires less
bandwidth, signal quality may be
reduced. As a result, picture quality
is generally not as good as full-motion
video. Quick motions often appear
somewhat blurred. This quality issue is
becoming less of a concern as more and
more playback systems for compressed
video run at 30 frames per second.
Computer-based Training
(CBT). An interactive instructional
approach in which the computer, taking
the place of an instructor, provides a
series of stimuli to the student
ranging from questions to be answered
to choices or decisions to be made. The
CBT then provides feedback based on the
student's response.
Computer Conferencing. An
ongoing computer conversation via text
with others in different locations.
Conferencing can be done in "real
time," so that messages appear as they
are being keyed, or it can be
"asynchronous," which means the
complete message is keyed and then
stored for later use by the receiver or
sender.
DBS. Direct Broadcast
Satellite.
DDS. Digital Direct
Satellite.
Desktop Publishing. Software
programs that enable the user to use a
microcomputer and a laser or color
printer to produce relatively
high-quality publications.
Desktop Videoconferencing.
Videoconferencing on a personal
computer equipped with a fast Internet
connection (at least 28.8 Kbps modem),
a microphone, and a video camera .
There can be two-way or multi-way video
and audio depending upon the hardware
and software of participants. Most
appropriate for small groups or
individuals. Not yet presently
available in many parts of the country
due to bandwidth and equipment
limitations for this application.
Digital Communication. A
communications format used with both
electronic and light-based space
systems that transmits audio, video,
and data as bits ("1s" and "0s") of
information. Codecs are used to convert
traditional analog signals to digital
format and back again. Digital
technology also allows communications
signals to be compressed for more
efficient transmission. See Analog
Communication.
Dish. An earthbound
dish-shaped antenna used for receiving
satellite signals. Also referred to as
downlink dish and ground receiving
dish.
Distance Communication. Use
of telecommunication technology for the
implementation of administrative
activities such as meetings, focus
group, or job interviews when the
parties are located at two or more
locations.
Distance Education. See
Distance Learning. The term distance
education is often used synonymously
with distance learning. However,
distance education typically refers to
distributed learning resources in
academic settings.
Distance Learning. A system
and a process that connects learners
with distributed learning resources.
While distance learning takes a wide
variety of forms, all distance learning
is characterized by the following: 1)
separation of place and/or time between
instructor and learner, among learners,
and/or between learners and learning
resources, and 2) interaction between
the learner and the instructor, among
learners, and/or between learners and
learning resources conducted through
one or more media; use of electronic
media is not necessarily required.
Downloading. A procedure for
transferring or retrieving a file from
a distant computer. Opposite of
uploading. Many Web sites have links to
files such that you can simply click on
the link and your browser will handle
the downloading of the file(s) to your
computer.
Duplex Video. Two-way video
communication capable of simultaneous
origination and reception.
Earth Station. A
ground-placed antenna used to transmit
or receive signals to or from
satellites, typically located in
geostationary orbit.
Electronic Bulletin Boards.
Information services that can be
reached via computers connected by
modem and/or Internet. With these
services users can gather information,
place and read electronic messages from
other users, and download available
files.
Electronic Mail. More often
called E-Mail. E-mail is a fast, easy,
and inexpensive way to communicate with
individuals or groups on networked
computers and computers equipped for
Internet access. Besides basic
correspondence, with some systems you
can attach and send documents and other
files.
FAQ. List of frequently asked
questions and their answers.
Facsimile Machine (fax). A
telecopying device that electronically
transmits written or graphic material
over telephone lines to produce "hard
copy" at a remote location.
FCIF/QCIF. Standards-based
display format for communicating
between videoconference systems from
different vendors.
Fiber Optic Cable. Bundled
glass rods (fibers) that are extremely
thin and flexible and are capable of
transmitting voice, video, and data
signals in either analog or digital
formats. This is accomplished with very
little loss in signal quality. A single
glass fiber can carry the equivalent of
100 channels of television or 100,000
telephone calls, with even more
capacity possible by encasing many
fibers within a cable.
Footprint. The area of the
earth's surface where a particular
satellite's signal can be received. A
footprint can cover one-third of the
globe, but is usually less.
Frame rate. Frequency with
which video frames are displayed on a
monitor, typically described in
frames-per-second (fps). Higher frame
rates improve the appearance of video
motion. Broadcast TV (full-motion
video) is 30 frames-per-second.
Full-Motion Video. Equivalent
to broadcast television video with a
frame rate of 30 fps. Images are sent
in real time and motion is continuous.
Unlike compressed video signals (which
tend to be blurry), full-motion video
refers to high-quality signals, similar
to what is received over a television
set.
Geostationary Orbit. An earth
orbit located directly above the
equator, approximately 22,300 miles
above the surface. Satellites in this
orbit rotate at the same relative speed
as the earth itself. This allows earth
antennas to remain fixed.
Gopher. A menu-based system
for exploring the Internet. Users
locate resources by selecting resources
from menus.
H.320 Standard. A widely-used
video compression standard that allows
a wide variety of videoconferencing
systems to communicate. H.320 includes
a number of individual recommendations
for coding, framing, signaling, and
establishing connections.
Hard Drive (Hard Disk). A
rigid non-removable disk in a computer
and the drive that houses it. Hard
disks store more data and can be
accessed quicker than floppy disks.
High Definition TV (HDTV).
Regular NTSC signals have 525 lines of
resolution. HDTV has 1125 lines of
resolution having over five times the
video information than that of a
conventional NTSC-type TV set. In spite
of its obvious advantages, transmission
requires extraordinary bandwidth of
five times the capacity of a
conventional TV signal. TV receivers
are estimated to be 30% more expensive
than today's most costly sets.
Hypertext. Text with links to
other text. Documents written as
hypertext contain text that when
"clicked on" by the user with a mouse,
links to other documents.
HyperText Markup Language
(HTML). Set of programming commands
inserted around blocks of text that
describe how to display it. HTML
commands also display other media
(graphics, sound, and video). Documents
on the Web are often written in
HTML.
Instructional Multimedia. A
form of computer-based training that
incorporates a mix of media as the
stimulus to the student. Possible media
elements include sound, animation,
graphics, video, text; whatever it
takes to get the instructional message
across to the target audience. (See
Multimedia)
Instructional Systems
Development. Systematic approach to
the planning and development of a
product to meet instructional needs and
goals. All components of the system are
considered in relation to each other in
an orderly but flexible sequence of
processes. The resulting instructional
product is tried out and improved
before widespread use is
encouraged.
Instructional Television Fixed
Services (ITFS). A band of
low-power microwave frequencies set
aside by the Federal Communications
Commission (FCC) exclusively for the
transmission of educational
programming, and licensed to public
institutions. ITFS is typically used in
urban areas and requires a specialized
antenna. Receiving sites require a
converter capable of changing signals
to those used by a standard television
set.
Interactive Video.
Combination of a videodisc (usually
laserdisc) or videotape and computer
system that permits user response and
participation, allowing for direct
exchanges between user and software or
among people. This instructional medium
has limited use today.
Integrated Services Digital
Network (ISDN). Digital network
with higher speed than found on the
traditional telephone network. Even
though ISDN uses existing phone lines,
it does require specialized equipment.
Because the network is all digital it
can easily send voice, data, and video
over the same line simultaneously.
Internet. A worldwide network
of computer networks. It is an
interconnection of large and small
networks around the globe. The Internet
began in 1962 as a resilient computer
network for the U.S. military and over
time has grown into a global
communication tool of more than 12,000
computer networks that share a common
addressing scheme.
Internet Courses. Students
participate in the class by using the
Internet for all or part of the
coursework. The instructor posts a Web
page which contains all relevant course
information and assignments.
Communication between students and
instructors occurs by e-mail.
Intranet. Inter-connected
network within one organization that
uses Web technologies for the sharing
of information internally, not world
wide. Such information might include
organization policies and procedures,
announcements, or information about new
products.
Java. Programming language
developed by Sun Microsystems that
creates code for interactive
applications that is executable on web
pages by web browsers. These Java
applications can execute on any
platform--Mac, PC, etc.
JPEG (Joint Picture Expert
Group). Standard for the
compression of still pictures, such as
those that might be used on a Web
site.
Ku-band. Most popular type of
satellite transmission for uplinking
and downlinking. Ku-band operates on a
higher frequency than C-band
transmissions and requires smaller
antennas.
LAN (Local Area Network).
Communications network connecting
computers by wire, cable, or fiber
optics link. Usually serves parts of an
organization located close to one
another, generally in the same building
or within 2 miles of one another.
Allows users to share software,
hardware and data.
Links. A graphic, line of
text, or both on a Web page that
connects to another page on the same
Web site or to one on a Web server
located anywhere in the world. Links
are "clicked on" to go to the Web page
they specify.
ListServ. Mailing list
program for communicating with other
people who have subscribed to the same
list. Using E-mail, you can participate
in listservs pertaining to your topics
of interest. When you submit a message
to the server your message is relayed
to all those on the listserv. You
receive messages from other
participants via E-mail. It is similar
to computer conferencing, but a
listserv is asynchronous.
Logging On. Connecting to a
computer network, typically through the
use of a personalized identification
code.
Mainframe Computer. A large
relatively complex computer. Its
capacity far exceeds that of the
microcomputer.
Microcomputer. A computer
with a microprocessor chip-based
processing unit. Microcomputers are the
original personal computers that many
people use at home and at work.
Microwave. High-frequency
radio waves used for point-to-point and
omnidirectional communication of audio,
data, and video signals. Microwave
frequencies require direct line of
sight to operate. Obstructions in the
path usually distort or block the
signal. Growth of fiber optic networks
have tended to curtail the growth and
use of microwave relays.
Modem. Equipment that
converts digital signals into analog
signals for purpose of transmission
over a telephone line. Signal is then
converted back to digital form so that
it can be processed by a receiving
computer. Modems are typically used to
link computers via telephone lines.
Short for modulator-demodulator.
Typical modems for home use are 14.4
kbps. 14 kilobytes per second
translates into a transmission or
receiving rate of approximately 1600
bytes per second.
MPEG. Moving Picture Experts
Group. The standard for compression and
storage of motion video, for example,
videos available though the World Wide
Web.
Multimedia. Systems that
support the interactive use of text,
audio, still images, video, and
graphics. Each of these elements must
be converted in some way from analog
form to digital form before they can be
used in a computer application. Thus,
the distinction of multimedia is the
convergence of previously diverse
systems.
Multiplex. The act of
combining input signals from many
sources onto a single communications
path, or the use of a single path for
transmitting signals from several
sources. Advantages of multiplexing is
that it doubles the capacity of
television transmission and allows for
simultaneous feed of independent
programs for two audiences.
Multi-point videoconference.
A video conference with 3 or more
sites. Sites must connect via a video
bridge.
NTSC. National Television
Systems Committee. The American
engineering standard for horizontal
video resolution lines, 525.
Network. A configuration of
two or more computers linked to share
information and resources.
News Group. Discussion group
on the Internet. Similar to electronic
bulletin boards. Users are presented
with a summary of discussion topics and
can select from an organized menu and
sub-menu structure.
Node. An origination or
reception site.
One-Way Video/Two-Way Audio.
An interactive conference, class, or
meeting in which participants see and
hear the speaker(s) at the originating
site as well as hear participants at
other receiving sites. Two-way
audioconferencing is used for the
real-time verbal interaction.
Originating Site. The site
initiating the conference or meeting
that is to be distributed
simultaneously with technology such as
audioconferencing or
videoconferencing.
Rain Outage. Loss of signal
at Ku-band satellite frequencies due to
absorption and increased sky noise
caused by rainfall or ice crystals in
the upper atmosphere.
Real Time. An application in
which information is received and
immediately responded to without any
time delay. See Synchronous.
Receiving Sites. All sites,
other than the originating site,
participating in a course or meeting
that is distributed with technology
such as audioconferencing or
videoconferencing.
Resolution. The clarity of
the image on video display screen.
Three factors influence resolution:
lines of resolution (vertical and
horizontal), raster scan rate (number
of times per second the image on a
video screen can be refreshed or "lit
up" again), and bandwidth.
RGB Monitor. Video display
screen with colors Red, Green, Blue as
light waves. The three colors combined
in different ways produce all other
colors.
Satellite. An earth-orbiting
device used for receiving and
transmitting signals. Each satellite
has a number of transponders which
receive the signal and bounce it back
to earth, where it is received by any
of the dish-shaped earth stations, then
transmitted via cable, phone lines, or
microwave to its final receiver TV
set.
Search Engines. Permits
searching of documents and databases
accessible on the Internet. Search
engines can be set up to search only
content within one Web site or to
search the entire Internet. Many search
engine developers have their own web
sites such as Lycos and Alta Vista. In
addition to search engines there are
index sites such as Yahoo, where links
to Web sites are organized into
categories so that you can browse
categories rather than guessing at
search terms.
Shareware. Computer software
developed for the public domain, which
can be used or copied without
infringing copyright. Programmers
typically get paid a small one time fee
from users who find the software
useful.
Simplex Video. One-way video
communication capable of origination
and reception, though not
simultaneously.
Solar Outage. Solar outages
occur when an antenna is looking at a
satellite, and the sun passes behind or
near the satellite and within the field
of view of the antenna. The field of
view is usually wider than the
beamwidth. Solar outages can be exactly
predicted as to the timing of each
site.
Switched Network. A type of
system in which each user has a unique
address (such as a phone number) that
allows the network to connect any two
points directly.
Synchronous. A type of
two-way communication that occurs with
virtually no time delay, allowing
participants to respond in real time.
Also, a system in which regularly
occurring events in timed intervals are
kept in step using some form of
electronic clocking mechanism. (See
Asynchronous)
Telecommunication. The
process of transmitting or receiving
information over a distance by any
electrical or electromagnetic medium.
Information may take the form of voice,
video, or data.
Teleconference. Simultaneous
conference to multiple sites
distributed via audio (phone or other
audio). Satellite videoconferences and
videoconferences using compressed video
are sometimes referred to as
"teleconferences." To distinguish more
accurately between these frequently
used terms, using the term which
uniquely describes the communication is
preferred.
Telemedicine. Use of
telecommunications technology for
medical diagnosis and patient care when
the provider and client are separated
by distance. Telemedicine includes
pathology, radiology, and patient
consultation from the distance.
Touch Screen. Input device
over the television or a special
computer screen that is used to
simplify user input and response. The
user touches the screen rather than a
keyboard, keypad, or mouse to control
the output. Touch screens work best
with menus or multiple-choice decision
points, and also allow some simulation
of hands-on training, i.e. pointing to
parts of a body.
Transponder. The electronic
equipment on a satellite that receives
signals from an uplink, converts
signals to a new frequency, amplifies
the signal, and sends it back to earth.
Satellites are usually equipped with 12
to 14 transponders.
Two-Way Video/Two-Way Audio.
Interactive video in which all sites
are in visual contact with one another.
Some form of audioconferencing is used
for real-time verbal interaction.
Uplink/Downlink. Programs are
"uplinked" to the satellite transponder
and "downlinked" to the ground
receiving dish.
Uploading. The transfer of
copies of a file from the user's own
computer to a remote database or other
computer. The reverse of
downloading.
URLs (Uniform Resource
Locators). Pronounced "earls". The
address system used by the Internet to
locate resources such as web sites. An
URL includes the type of resource being
accessed such as gopher or hypertext),
the address of the server, and the
location of the file. For example, the
complete URL for the PHTN Web site is
<index.asp>. "http://" indicates
the access method as Hyper Text
Transfer Protocol. "www.cdc.gov" is the
address of the server. "/phtn/"
specifies the directory the file is
located. "index.aspl" is the initial
page of the PHTN Web site. Web browsers
will assume "http://" and "index.aspl",
so you can simply use
<www.cdc.gov/phtn> as the
URL.
USDLA. US Distance Learning
Association.
Videoconference. A meeting,
instructional session, or conversation
between people at different locations
relying on video technology as the
primary communication link.
Communication is 2-way audio with
either 1-way or 2-way video. The term,
videoconference, is sometimes used to
refer to conferences via compressed
video, conferences via land lines, and
broadcasts via satellite. To avoid
confusion, using the term or phrase
which uniquely describes the
communication technology is
recommended.
Video Bridge. Specialized
equipment that permits three locations
or more to be joined together in a
videoconference.
Web-based Training (WBT). A
form of computer-based training in
which the training material resides on
web pages accessible through the World
Wide Web. Typical media elements used
are text and graphics. Other media such
as animation, audio, and video can be
used, but require more bandwidth and in
some cases additional software. The
terms "on-line courses" and "web-based
instruction" are sometimes used
interchangeably with WBT.
Web-casting. Communicating to
multiple computers at the same time
over Internet by "streaming" live audio
and/or live video. Through compression
and decompression of the signal, audio
and video are experienced in real time
over Internet. Examples of commercial
products emerging in this area include
RealAudio, VDOLive, and VXtreme.
Web-site. Related collection
of web documents. The address for a web
site (see URL) takes you to the initial
page, or home page. From the home page
you can go to all the other pages on
the web site.
World Wide Web (WWW). A
hypertext-based, distributed
information system originally created
by researchers at CERN, the European
Laboratory for Particle Physics, to
facilitate sharing research
information. The Web presents the user
with documents, called web pages, full
of links to other documents or
information systems. Selecting one of
these links, the user can access more
information about a particular topic.
Web pages include text as well as
multimedia (images, video, animation,
sound). Servers are connected to the
Internet to allow users to traverse (or
"surf") the Web using a Web browser. In
addition, many other resource formats
such as Gopher are accessible by Web
browsers.
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This page last reviewed: August 24, 2004
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