From: owner-ammf-digest@smoe.org (alt.music.moxy-fruvous digest) To: ammf-digest@smoe.org Subject: alt.music.moxy-fruvous digest V14 #4768 Reply-To: ammf@fruvous.com Sender: owner-ammf-digest@smoe.org Errors-To: owner-ammf-digest@smoe.org Precedence: bulk alt.music.moxy-fruvous digest Friday, August 14 2020 Volume 14 : Number 4768 Today's Subjects: ----------------- Take it with you on vacation, to the country, to the pool or work! ["Fly ] ---------------------------------------------------------------------- Date: Fri, 14 Aug 2020 05:56:51 -0400 From: "Fly Blocker" Subject: Take it with you on vacation, to the country, to the pool or work! Take it with you on vacation, to the country, to the pool or work! http://ligefreedom.guru/vtsDHiy09R9-dZtj984RQIkBHT_w-th3TUaSlhfb9UkO7cX8 http://ligefreedom.guru/0JfY7z8dm2avE8RF6OGoWYZgqPqd9fQvEzAGFto99IifdOTS A CD is read by focusing a 780 nm wavelength (near infrared) semiconductor laser through the bottom of the polycarbonate layer. The change in height between pits and lands results in a difference in the way the light is reflected. Because the pits are indented into the top layer of the disc and are read through the transparent polycarbonate base, the pits form bumps when read. The laser hits the disc, casting a circle of light wider than the modulated spiral track reflecting partially from the lands and partially from the top of any bumps where they are present. As the laser passes over a pit (bump), its height means that the part of the light reflected from its peak is 1/2 wavelength out of phase with the light reflected from the land around it. This causes partial cancellation of the laser's reflection from the surface. By measuring the reflected intensity change with a photodiode, a modulated signal is read back from the disc. To accommodate the spiral pattern of data, the laser is placed on a mobile mechanism within the disc tray of any CD player. This mechanism typically takes the form of a sled that moves along a rail. The sled can be driven by a worm gear or linear motor. Where a worm gear is used, a second shorter-throw linear motor, in the form of a coil and magnet, makes fine position adjustments to track eccentricities in the disk at high speed. Some CD drives (particularly those manufactured by Philips during the 1980s and early 1990s) use a swing arm similar to that seen on a gramophone. This mechanism allows the laser to read information from the center to the edge of a disc without having to interrupt the spinning of the disc itself.[further explanation needed] Philips CDM210 CD Drive The pits and lands do not directly represent the 0's and 1's of binary data. Instead, non-return-to-zero, inverted encoding is used: a change from either pit to land or land to pit indicates a 1, while no change indicates a series of 0's. There must be at least 2, and no more than 10 0's between each 1, which is defined by the length of the pit. This, in turn, is decoded by reversing the eight-to-fourteen modulation used in mastering the disc, and then reversing the cross-interleaved ReedbSolomon coding, finally revealing the raw data stored on the disc. These encoding techniques (defined in the Red Book) were originally designed for CD Digital Audio, but they later became a ------------------------------ End of alt.music.moxy-fruvous digest V14 #4768 **********************************************