User Manual

Chapter 1
Overview of CD Technology
CDs have become the standard in audio distribution. Due to the comprehensive set of CD industry standards and
formats, CDs have become the least expensive and most reliable vehicle for exchanging information.
Evolution of CD-R devices technology
To understand the CD-R (Compact Disc-Recordable) disc, it is first necessary to understand standard compact disc (CD-
ROM) technology and how it has evolved. A basic knowledge of this technology will deepen your understanding of what
occurs every time you listen to a CD or create your own.
Digital audio places enormous demands on the medium to which it is being recorded. For example, 60 minutes of music
that is recorded in stereo at a 16-bit quantization rate and 44.1 kHz sampling rate requires a capacity of just over five
billion bits. Luckily, compact discs were designed with this requirement in mind. Unfortunately, for many years musicians
were not able to utilize this storage technology.
Until 1988, the only means of placing music on a compact disc was through injection molding. This process required
musicians to do their testing by recording music to tape and then forwarding it on to the manufacturer. This requirement
resulted in a costly and time-consuming process.
In 1988, Phillips and Sony released the specifications for CD-R discs. It was under these standards that musicians were
given the tools to record information onto CDs at home or in the studio.
CD-ROM technology basics
A standard Compact Disc-Read Only Memory (CD-ROM) disc is 4¾ inches in diameter and consists of aluminum, lacquer,
and clear polycarbonate plastic. During CD molding process, the polycarbonate base has minute indentations stamped
into it. Next, a highly reflective layer of aluminum is applied to the polycarbonate base. The aluminum and polycarbonate
is then sealed with lacquer to protect the disc’s surface from scratching and dust.
How the information is stored
The information on CDs is represented by minute indentations in the polycarbonate base, called pits, separated by the
surface of the aluminum layer, called the land. Both pits and lands represent zeros and the transition from one to the
other represents a one.
Various lengths of pits and lands represent varying quantities of zeros, which represent the original audio signal.
Generally, the frequency of the audio signal is represented by the rate of change in the numbers and the amplitude is
represented by the magnitude of the numbers.
How the information is read
The CD player or drive directs a laser beam through the polycarbonate base and onto the aluminum layer. Because the CD
is actually read from the bottom, pits in the CD are viewed as bumps. Light from the laser reflects off the aluminum
surface and photo-detectors recognize the different intensities of the reflected light. The different intensities, caused by
the pits and lands, are processed into zeros and ones. The CD player or drive then processes this binary data into music.
Because nothing but light ever hits the discs, there is no degradation from repeated playings and the original audio signal
never wears out.
From CD-ROM to CD-R
Commercially produced CDs have pits molded into them during manufacturing, whereas CD-Rs are blank. CD-Rs consist
of a polycarbonate base and, instead of the reflective aluminum layer, CD-Rs contain a layer of organic dye. The organic
dye is to the CD-R what the aluminum is to the CD-ROM: the recording medium.
OVERVIEW OF CD TECHNOLOGY | 7