Editing CD player (section)

==Mechanical components==
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[[File:Dismantled Philips EXP2582 portable CD player.jpg|thumb|[[Philips]] Portable CD player disassembled]]
A CD player has three major mechanical components: a '''drive motor''', a '''[[lens]] system''' or pickup head, and a '''tracking mechanism'''.
The drive motor (also called spindle) spins the disc to a scanning velocity of 1.2–1.4&nbsp;m/s ([[constant linear velocity]]) – equivalent to approximately 500 RPM at the inside of the disc, and approximately 200 RPM at the outside edge. (A disc played from beginning to end slows its rotation rate during playback.) The tracking mechanism moves the lens system along the spiral tracks in which information is encoded, and the lens assembly reads the information using a [[laser beam]] produced by a [[laser diode]]. The laser reads information by focusing a beam on the CD, which is reflected off the disc's mirrored surface back to a [[photodiode]] array sensor. The sensor detects changes in the beam, and a digital processing chain interprets these changes as binary data. The data are processed and eventually converted to [[sound]] using a [[digital-to-analog converter]] (DAC).

A TOC or Table of Contents is located after the ''lead-in'' area of the disc, which is located in an inner ring of the disc and contains roughly five kilobytes of available space. It is the first information that the player reads when the disc is loaded in the player and contains information on the total number of audio tracks, the running time on the CD, the running time of each track, and other information such as ISRC and the format structure of the disc. The TOC is of such vital importance for the disc that if it is not read correctly by the player, the CD could not be played back. That is why it is repeated three times before the first music program starts. The ''lead out'' area in the end (the outer peripheral) of the disc tells the player that disc has come to an end.