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close this bookNew Training Technologies (ILO - UNEVOC, 1995, 95 p.)
View the document(introduction...)
View the documentIntroduction
View the documentChapter 1 New Technologies and Training
Open this folder and view contentsChapter 2 Delivery mechanisms and available NTTs
Open this folder and view contentsChapter 3 Selecting the appropriate NTTs
View the documentChapter 5 Trends in NTTs
View the documentConclusion
Open this folder and view contentsAppendix A Compatibility
View the documentAppendix B Suggested PC configurations
View the documentAppendix C Laser technology
View the documentAppendix D Digital versus analogue
View the documentAppendix E Digitizing
View the documentAppendix F Telecommunications and training
View the documentAppendix G More technologies for training
View the documentAppendix H Training the disabled
View the documentGlossary23

Appendix C Laser technology

Laser technology refers to the way disks are written and read:

· the videodisk (30 cm diameter) is an analogue technology; it allows one to record 54,000 high quality images on each side, as well as two sound tracks. There is a considerable amount of educational material recorded on videodisks; some of it has been recently digitized on other supports;

· the audio-CD was launched with the success we know. It contains high quality sound (44 Mhz) but can record nothing but sound. Little educational material exists on this support;

· the WORM was the first digital disk written (once only) and read (many times) by a computer. It had a rather small capacity of 200 Mb and a slow transfer rate; but a new generation of WORMs now records 400 or even 600 Mb;

· the CD-ROM came later; it contains all types of files: text, images, sound, compressed video, up to 600 Mb. Its transfer rate was 150 Kb/sec, but this has been doubled and even tripled in some recent drives. Data are not interlaced, which makes it almost impossible to run video and audio at the same time (loss of synchronisation);

· the CD-ROM XA ("extended architecture") is more recent; its characteristics are close to those of the CD-ROM, but this time the data are interlaced, which means that one can use them for perfectly synchronized video and audio. It has been presented as a bridge between the CD-ROM and the CD-I;

· the CD-I (a proprietary system of PHILIPS) is used for the same applications as the CD-ROM XA, with the particularity that it does not operate connected to a PC. It consists on a specific player which contains the necessary PC functions. The unit is connected to a normal TV set. This has the advantage of low cost but some limitations in interactivity compared to a PC;

· the photo-CD is a CD containing up to 100 high-quality images, which can be recorded by KODAK only, starting from existing slides or negatives of photographs. It is possible to add images up to the maximum in different "sessions"; which makes it important to use a player that runs multiple sessions, otherwise only the images written the first time can be accessed. It can be played on a KODAK specific player, on a CD-I or on a computer via any CD-ROM player, preferably multisession. The photo-CD player also plays audio CDs;

· the read-write optical diskette is a magneto-optical device, which records 127 Mb of data and needs a special drive to be written and/or read; it also exists in a "write once" form to store data. Its size is that of a 3.5" diskette, and its thickness is about twice the usual diskette; a very convenient system to transport or send multimedia applications; no standard is needed here: the optical diskette works like any diskette or hard disk.