Phase-change Dual
 | |
 PD-M650 media produced by Teac | |
| Media type | Optical disk |
|---|---|
| Encoding | Digital signal |
| Developed by | Matsushita |
| Usage | Data storage |
| Extended to | DVD-RAM |
Phase-change Dual (or Phase-change Disc, commonly abbreviated as PD) is a rewritable optical disc format and storage standard introduced by Matsushita Electric Industrial Co., Ltd. in April 1995.
The media offers a capacity of 650 MB on a single side. The discs are 120 mm (4.7 inches) in diameter, identical in size to a standard CD or DVD, and are permanently housed within a protective caddy. PD utilizes phase-change recording technology with a red laser and supports approximately 500,000 rewrite cycles.
Matsushita and other manufacturers produced both internal and external PD drives, which were marketed as a novel "dual function" system capable of reading standard CD-ROMs while also operating as a rewritable phase-change drive. In August 1996, Matsushita integrated the technology into its laptop line by releasing the PRONOTE PD, a notebook computer featuring a built-in drive that functioned as both a 650 MB storage device and a 4× CD-ROM reader.