CD player in 1970. Following litigation, Sony and Philips licensed Russell's patents (then held by a Canadian company, Optical Recording Corp.) in the 1980s. The Compact Disc is an evolution of LaserDisc technology, where a focused laser beam is used that enables the high information density required for high-quality digital audio signals. Prototypes were developed by Philips and Sony independently in the late 1970s. In 1979, Sony and Philips set up a joint task force of engineers to design a new digital audio disc. After a year of experimentation and discussion, the "Red Book" CD-DA standard was published in 1980. After their
Philips Records the Philips Recording Center in Baarn, Netherlands, and formed Polyhymnia International (a recording and mastering company) and Pentatone Records (which specializes in SACD releases). Many of the Philips classical recordings have been reissued on the Eloquence label. Universal also released a "Philips 50" series marking the 50th anniversary of Philips Records in the early 2000s; some of those CDs are still in print. Pentatone has released Philips Quadraphonic sound recordings from the early and mid-1970s in 4-channel SACD format, as their RQR Series. Philips' classical catalog was issued on CD under the headings "Digital Classics", "Legendary Classics" and "Silver Line