Copyright © 2003 by P earson Education, Inc . All rights reserve Distance Education Systems
Copyright © 2003 by Pearson Education, Inc. All rights reserved. Distance Education Systems.
Mar 31, 2015
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Copyright © 2003 by Pearson Education, Inc. All rights reserved.
Distance Education Systems
Distance Education Systems
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
Distance Education SystemsDistance Education Systems
Asynchronous Communication:• Delayed interaction between
teacher and student.
Synchronous Communication• Real-time interaction between
teacher and student.
Asynchronous Communication:• Delayed interaction between
teacher and student.
Synchronous Communication• Real-time interaction between
teacher and student.
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
Asynchronous Technologies "Correspondence Study"
Asynchronous Technologies "Correspondence Study"
• Print-based• Audio-based
–radio–audiotape
• Video-based–broadcast television –videotape
• Print-based• Audio-based
–radio–audiotape
• Video-based–broadcast television –videotape
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
Print-based CorrespondencePrint-based Correspondence
Normally, learning materials (textbook, study guide) are delivered by mail.
Original form of distance education -- dates from mid-1800s.
Normally, learning materials (textbook, study guide) are delivered by mail.
Original form of distance education -- dates from mid-1800s.
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
Advantages–Learner-paced–Can be used anywhere–Low cost
Disadvantages–Limited interactivity–Motion cannot be shown–Tarnished reputation
Advantages–Learner-paced–Can be used anywhere–Low cost
Disadvantages–Limited interactivity–Motion cannot be shown–Tarnished reputation
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
“I opened a letter and read it. It offered me a six months' correspondence course in finger- printing at a special professional discount. I dropped it into the wastebasket…”
“I opened a letter and read it. It offered me a six months' correspondence course in finger- printing at a special professional discount. I dropped it into the wastebasket…”
The Big Sleep by Raymond ChandlerThe Big Sleep by Raymond Chandler
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
"Allied Commissioners' Courses; be a detective, send for a one-volume correspondence course. No tests, no instructors, no salesmen will call. Free handcuffs and badge included as a special bonus if you act now."
"Allied Commissioners' Courses; be a detective, send for a one-volume correspondence course. No tests, no instructors, no salesmen will call. Free handcuffs and badge included as a special bonus if you act now."
Good Behavior by Donald WestlakeGood Behavior by Donald Westlake
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
Audio and Video-based Correspondence StudyAudio and Video-based Correspondence Study
Learning materials include textbook and workbook, plus audio-or videotape
• Advantages: similar to print-based.with visual and/or audio component
• Disadvantage: limited interactivity
Learning materials include textbook and workbook, plus audio-or videotape
• Advantages: similar to print-based.with visual and/or audio component
• Disadvantage: limited interactivity
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
Interactive Telecommunications
Interactive Telecommunications
• Audioconferencing• Satellite• Microwave (ITFS)• Compressed video• Fiber-optics
• Audioconferencing• Satellite• Microwave (ITFS)• Compressed video• Fiber-optics
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
AudioconferencingAudioconferencing
Teacher and students linked by telephone --a "conference call."
• Advantages: relatively inexpensive, flexible
• Disadvantage: lacks visual component
Teacher and students linked by telephone --a "conference call."
• Advantages: relatively inexpensive, flexible
• Disadvantage: lacks visual component
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
Satellite-based Distance Education
Satellite-based Distance Education
"Uplink" transmits signal to satellite in geosynchronous orbit. Transponder amplifies signal, transmits it back to earth. Signal is received by "downlinks" (satellite dishes).
"Uplink" transmits signal to satellite in geosynchronous orbit. Transponder amplifies signal, transmits it back to earth. Signal is received by "downlinks" (satellite dishes).
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
SatelliteSatellite
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
Advantages• Huge "footprint" means programming can be
delivered virtually anywhere to virtually unlimited number of sites
Disadvantages• Very expensive to purchase and operate
• Normally, video is only one way and students use telephone to communicate with teacher
Advantages• Huge "footprint" means programming can be
delivered virtually anywhere to virtually unlimited number of sites
Disadvantages• Very expensive to purchase and operate
• Normally, video is only one way and students use telephone to communicate with teacher
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
Microwave-based (ITES) Distance Education
Microwave-based (ITES) Distance Education
• Essentially, low-powered TV• Special frequencies/channels• Point-to-point or multipoint• Line-of-sight, 25-30 miles max.• Usually one-way video, two-way audio
• Essentially, low-powered TV• Special frequencies/channels• Point-to-point or multipoint• Line-of-sight, 25-30 miles max.• Usually one-way video, two-way audio
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
AdvantagesAdvantages
• Full-motion video• Control over who receives signal• Excellent audio and video quality• No right-of-ways required
• Full-motion video• Control over who receives signal• Excellent audio and video quality• No right-of-ways required
Jones. et al., 1992Jones. et al., 1992
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
MicrowaveMicrowave
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
DisadvantagesDisadvantages
• Transmissions affected by weather• Line-of-site only• Limited number of frequencies available
• Transmissions affected by weather• Line-of-site only• Limited number of frequencies available
Jones. et al., 1992Jones. et al., 1992
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
Compressed Video-based Distance Education
Compressed Video-based Distance Education
• Analog video signal digitized, then:• Processed to reduce unnecessary
information transmitted• Copper telephone lines connect sites• Not full-motion--fewer than 30 images
per second
• Analog video signal digitized, then:• Processed to reduce unnecessary
information transmitted• Copper telephone lines connect sites• Not full-motion--fewer than 30 images
per second
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
Advantages• Easy to install and use• Can be cheaper than fiber or
microwave
Disadvantages:• Motion can be jerky• Video quality can be poor• Can't transmit full-motion video
Advantages• Easy to install and use• Can be cheaper than fiber or
microwave
Disadvantages:• Motion can be jerky• Video quality can be poor• Can't transmit full-motion video
Jones. et al., 1992Jones. et al., 1992
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
Compressed VideoCompressed Video
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
Fiber Optics-based Distance Education
Fiber Optics-based Distance Education
• Used for telephone and cable TV main trunk lines
• Only recently used for education• Cable uses optically pure glass• Transmits light energy
• Used for telephone and cable TV main trunk lines
• Only recently used for education• Cable uses optically pure glass• Transmits light energy
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
Fiber OpticsFiber Optics
Copyright © 2003 by Pearson Education, Inc. All rights reserved.
Advantages• Full-motion video• High quality• Unaffected by weather
Disadvantages• High start-up costs• Slow, expensive repairs• Right-of-way costs
Advantages• Full-motion video• High quality• Unaffected by weather
Disadvantages• High start-up costs• Slow, expensive repairs• Right-of-way costs
Jones. et al., 1992Jones. et al., 1992
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