In the early 1970s, using video Laserdisc technology, Philips' researchers started experiments with "audio-only" optical discs, initially with wideband frequency modulation (FM) and later digitized PCM audio signals. At the end of the '70s, Philips, Sony, and other companies presented prototypes of digital audio discs.
In 1979 Philips and Sony decided to join forces, setting up a joint taskforce of engineers whose mission was to design the new digital audio disc. Prominent members of the taskforce were Kees Imminque and Toshitada Doi. After a year of experimentation and discussion, the taskforce produced the "Red Book", the Compact Disc standard. Philips contributed the general manufacturing process, based on the video Laserdisc technology. Philips alos contributed the Eight-to-Fourteen Modulation, EFM, which offers both a large playing time and a high resilience against disc handling damage such as scratches and fingerprints; while Sony contributed the error-correction method, CIRC.