GLOSSARY 321 Organic light-emitting diodes (OLEDs): Light-emitting diodes built up from layers of organic materials. Light is emitted by electrons recombin- ing with a lack of electrons (electron holes). Peer-to-peer network (P2P): Several computers distribute content to one another. P2P is used in file-sharing systems and might also be used for digital signage applications to relieve the load on the content manage- ment server, which distributes content to only some of the media players, which then share content with the remaining players. Playlist: A list with instructions as to what files are to be displayed and for how long. The playlist is usually contained in its own file. Content speci- fied by a playlist is called "block." Playlog: A file containing information on what content has been shown on a specific screen. It is a kind of receipt of delivery of the content on the screens. It may include other technical status data. A return path is required to collect the playlogs if this is to be done automatically. Point of purchase: The physical location where the customer makes the purchase, such as in stores, restaurants, and hotels. Progressive scanning: All lines in a scanned picture are covered in one single scan, as opposed to interlaced scanning, where the scanning proc-