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The New Communications Technologies, 5th Edition by Barbara Morgenstern, Michael Mirabito

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9        Information Storage: The Optical Disk and Holography

The optical disk emerged as an important information storage tool in the 1980s. A popular application is the compact disk (CD), a small, round disk that stores digital audio information in the form of microscopic pits. To retrieve this information, you place a CD in a player.1 A laser subsequently reads back or recovers the information.

A laser’s light scans the CD, and its beam is reflected to different degrees, in terms of its strength, when it passes over the pits and unpitted areas called lands. A light-sensitive detector picks up the reflected light, an optical representation of the stored information. After processing, the final output for a CD is an analog signal.

The CD and ...

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