Compact Disc

Recordable and erasable CDs will give the compact disc greater versatility. Compact disc recorders went on the market in 1997 and allow the user to record audio from various sources on CDs. The recorders require some finesse in use because the recording procedure used depends on the type, quality, and input device of the source material. If the source is a CD that can be played on a machine with digital optical output, it can be connected directly to the CD recorder as input and be dubbed much like audio tapes. The recorder evaluates the sonic range of the original and digitally synchronizes it; if tracks are recorded from several CDs, the recorder must resynchronize with each track. Also, the CD recorder does not erase, so care is needed during recording to copy the desired tracks only.

Erasable CDs became common by 2001. Erasable CDs or CD-RWs allow flexible data storage because they can be overwritten when the data on them becomes obsolete. CD-RWs are important as a publishing medium because they can be used to display multi-media presentations. Consequently, today's desktop-published newsletter may become text with audio and video displays. High-density CD-Rs and CD-RWs are also being developed.

Improvements are also coming to audio CDs as manufacturers seek new features that will improve sales. Enhanced audio CDs now include music videos, lyrics, scores that the home musician can play, and interviews with the musicians. Enhanced audio CDs can be played on a CD-ROM drive and viewed on a monitor or connected television set. High Definition Compatible Digitals, or HDCDs, are also being marketed. They produce more realistic sound but require a CD player with a builtin decoder.

Developments in technical and scientific uses of CDs are also being explored. One of the most promising is a portable medical laboratory called the LabCD. A drop of blood is placed on the CD near the center hole. As the CD spins, it acts like a centrifuge and separates the cells in the blood. They slip into receptacles in the CD that contain testing chemicals, and sensors read the results of a range of blood tests including DNA tests. This technology opens the possibility for ambulances to carry LabCDs and the CD-sensing machine and to perform on-the-spot analyses for drug and alcohol use or DNA tests at crime scenes.