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Phase-change Dual
Phase-change Dual is a CD-based optical disc technology as implemented in Panasonic’s patented PD system. It is recordable and can contain 650 megabytes of data. The DVD-RAM format has developed from PD. The PD also had a cartridge around the disc.
Similar to phase-change WORM technology (as used in CD-R) this uses an active layer with reversible properties allowing data to be overwritten in a single pass of the read/write head. This compares with the two-pass operation of conventional Magneto Optical devices.
Panasonic's PD technology is included by virtue the compatibility it offers with certain CD media formats - a Panasonic DVD-RAM device also being capable of reading and writing PD discs. New optical disc drives cannot read or write PD discs.
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