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Copyright © 2003 by Pearson Education, Inc. All rights reserved. Distance Education Systems.

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1 Copyright © 2003 by Pearson Education, Inc. All rights reserved. Distance Education Systems

2 Copyright © 2003 by Pearson Education, Inc. All rights reserved. Distance 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.

3 Copyright © 2003 by Pearson Education, Inc. All rights reserved. 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

4 Copyright © 2003 by Pearson Education, Inc. All rights reserved. Print-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.

5 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

6 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… The Big Sleep by Raymond Chandler

7 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." Good Behavior by Donald Westlake

8 Copyright © 2003 by Pearson Education, Inc. All rights reserved. Audio 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

9 Copyright © 2003 by Pearson Education, Inc. All rights reserved. Interactive Telecommunications Audioconferencing Satellite Microwave (ITFS) Compressed video Fiber-optics Audioconferencing Satellite Microwave (ITFS) Compressed video Fiber-optics

10 Copyright © 2003 by Pearson Education, Inc. All rights reserved. Audioconferencing 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

11 Copyright © 2003 by Pearson Education, Inc. All rights reserved. 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).

12 Copyright © 2003 by Pearson Education, Inc. All rights reserved. Satellite

13 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

14 Copyright © 2003 by Pearson Education, Inc. All rights reserved. Microwave-based (ITES) Distance Education Essentially, low-powered TV Special frequencies/channels Point-to-point or multipoint Line-of-sight, miles max. Usually one-way video, two-way audio Essentially, low-powered TV Special frequencies/channels Point-to-point or multipoint Line-of-sight, miles max. Usually one-way video, two-way audio

15 Copyright © 2003 by Pearson Education, Inc. All rights reserved. Advantages 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., 1992

16 Copyright © 2003 by Pearson Education, Inc. All rights reserved. Microwave

17 Copyright © 2003 by Pearson Education, Inc. All rights reserved. Disadvantages 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., 1992

18 Copyright © 2003 by Pearson Education, Inc. All rights reserved. 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

19 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., 1992

20 Copyright © 2003 by Pearson Education, Inc. All rights reserved. Compressed Video

21 Copyright © 2003 by Pearson Education, Inc. All rights reserved. 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

22 Copyright © 2003 by Pearson Education, Inc. All rights reserved. Fiber Optics

23 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., 1992


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