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 PM5544 the most commonly used test cards, with only the SMPTE bars, the BBC Test Card F and the Snell & Wilcox Zone Plate coming close to its usage. The Philips Pattern was later incorporated into other test pattern generators from Philips themselves, as well as test pattern generators from various other manufacturers. The BBC occasionally used a slightly modified version called Test Card G from 1971 until the late-1990s in conjunction with Test Card F, and although it was also used by the IBA in the 1970s it eventually abandoned the Test Card G and developed its own test card