PD
full spelling ： Phase-change Dual
Phase-change Dual is an optical disc format for the storage of digital media. It is a rewritable optical disc format introduced by Panasonic in 1995. First Phase-change Dual disc has a capacity of 650 MB. It can be rewritten 500,000 times and is enclosed in a protective cartridge.
Phase-change Dual discs are compatible with first generation Panasonic DVD-RAM drives and Multi CD-R recorders as well as PD drives. Apart from read and write PD discs, PD drives can read and write CD-ROMs.