Cast iron

One is HMS 1, wich means Heavy Melting Scrap grade 1,and HMS 2, which means Heavy Melting Scrap grade 2. This may be in large degree due to its status as a Philips trademark under that spelling. For purposes of recycling, cast iron is classified into two types. Notwithstanding the variability of general usage between "disk" and "disc" [3], the customary spelling is "compact disc", rather than "compact disk". The properties are similar to malleable iron but parts can be cast with larger sections. Not all players allow this. Along with careful control of other elements and timing, this allows the carbon to separate as spheroidal particles as the material solidifies. To hear the hidden track, the listener must usually "rewind" the player past the beginning of the first listed track.

Tiny amounts of magnesium or cerium added to these alloys slow down the growth of graphite precipitates by bonding to the edges of the graphite planes. In this case, the hidden track is an unlisted track sandwiched between the two. A more recent development is nodular or ductile cast iron. On most discs, the location of the first track listed in the table of contents immediately follows the table of contents itself. There is a limit to how large a part can be cast in malleable iron, since it is made from white cast iron. Other discs hide the extra material at the beginning of the disc. In general, the properties of malleable cast iron are more like mild steel. Either way, the hidden portion is heard when the disc is played to the end.

They also have blunt boundaries, as opposed to flakes, which alleviates the stress concentration problems faced by grey cast iron. These may be an extension of the last audio track or a separate track hidden from the disc's table of contents. Due to their lower aspect ratio, spheroids are relatively short and far from one another, and have a lower cross section vis-a-vis a propagating crack or phonon. Some commercially released audio discs have a "secret" bonus track. Graphite separates out much more slowly in this case, so that surface tension has time to form it into spheroidal particles rather than flakes. This is commonly referred to as the analog hole. Malleable iron starts as a white iron casting, that is then heat treated at about 900 °C. Any loss of sound quality caused by this method is generally considered negligible.

High-chrome white iron alloys allow massive castings (for example, a 10t impeller) to be sand cast, i.e., a high cooling rate is not required, as well as providing impressive abrasion resistance. In any case, even if a disc cannot be directly ripped, it can still be played in audio mode, and the audio thence captured. White cast iron can also be made by using a high percentage of chromium in the iron; Cr is a stong carbide-forming element, so at high enough percentages of chrome, the precipitation of graphite out of the iron is suppressed. Other systems developed are Macrovision CDS-200 and Mediamax CD-3. The resulting casting, called a “chilled casting”, has the benefits of a hard surface and a somewhat tougher interior. The reason for this reuse is cost efficiency. However, rapid cooling can be used to solidify a shell of white cast iron, after which the remainder cools more slowly to form a core of grey cast iron. in car radios, have problems playing copy-protected media, mostly because they use hardware and firmware components also used in CD-ROM drives.

It is difficult to cool thick castings fast enough to solidify the melt as white cast iron all the way through. Also, many ordinary CD audio players, e.g. White iron is too brittle for most uses, but with good hardness and abrasion resistance and relatively low cost, it finds use in such applications as balls for rolling-element bearings, the wear surfaces (impeller and volute) of slurry pumps and the teeth of a backhoe's digging bucket. For example, audio tracks on such media cannot be easily added to a personal music collection on a computer's hard disk or a portable (non-CD) music player. Since carbide makes up a large fraction of the material, white cast iron could reasonably be classified as a cermet. However, there has been great public outcry over copy-protected discs because many see it as a threat to fair use. These precipitates inhibit plastic deformation by impeding the movement of dislocations through the ferrite matrix, offering hardness at the expense of toughness. It also seems likely that Philips' new models of CD recorders will be designed to be able to record from these "protected" discs.

With a lower silicon content and faster cooling, the carbon in white cast iron precipitates out of the melt as the metastable phase cementite, Fe₃C, rather than graphite. Philips has stated that such discs are not permitted to bear the trademarked Compact Disc Digital Audio logo because they violate the Red Book specification. Grey cast iron's high thermal conductivity and specific heat capacity are often exploited to make cast iron cookware. This is intended to prevent the data track from being ripped, but can be defeated by ignoring the table of contents and reading the disc sector by sector. It is also difficult to weld. Another copy protection method places a data track (usually containing bonus software for computer users) at the end of the disc and gives it an invalid size in the disc's table of contents. Easier initiation of cracks can be a drawback once an item is finished, however: grey cast iron has less tensile strength and shock resistance than steel. These discs are said to be more sensitive to disc pollution or surface damage (typically in the form of scratches) because they partially exhaust the error-correction thresholds incorporated into the Red Book standard right from the time of production.

The sharp edges of graphite flakes also tend to concentrate stress, allowing cracks to form much more easily, so that material can be removed much more efficiently. Some of these deliberately introduced error patterns into audio tracks severe enough to defeat the error-correcting code (and hence defeat most CD-ROM drives attempting to copy the tracks as data), but not so disruptive as to prevent interpolation from working (hence allowing the same tracks to be played in audio mode without overly affecting fidelity). All of the properties listed in the paragraph above ease the machining of grey cast iron. Starting in early 2002, attempts were made by record companies to market "copy-protected" compact discs. In practical terms, this means that cast iron tends to “damp” mechanical vibrations (including sound), which can help machinery to run more smoothly. Where error correction fails on larger defects, audio CD players are expected to apply interpolation algorithms to conceal the loss of audio data. Since ferrite is so different in this respect (having heavier atoms, bonded much less tightly) phonons tend to scatter at the interface between the two materials. An error-correcting code is included with Red Book audio to deal with small scratches or defects on the disc media.

The exceptionally high speed of sound in graphite gives cast iron a much higher thermal conductivity. Ripping is the process by which the contents of an audio disc is copied out verbatim to a duplicate disc or re-encoded into some other format, such as MP3 or Ogg Vorbis. Graphite acts as a lubricant, improving wear resistance. The Red Book audio specification does not include any copy protection mechanism. The graphite content also offers good corrosion resistance. A CD-RW does not have as great a difference in the reflectivity of lands and bumps as a pressed CD or a CD-R, and so many CD audio players cannot read CD-RW discs, although the majority of standalone DVD players can. The metal expands slightly on solidifying as the graphite precipitates, resulting in sharp castings. The write laser in this case is used to heat and alter the chemical properties of the alloy and hence change its reflectivity.

This structure has several useful properties. CD-RW is a re-recordable medium that uses a metallic alloy instead of a dye. Weak bonding between planes of graphite lead to a high activation energy for growth in that direction, resulting in thin, round flakes. The resulting discs can be read by most CD-ROM drives and played in most audio CD players. Silicon causes the carbon to rapidly come out of solution as graphite, leaving a matrix of relatively pure, soft iron. CD-R recordings are permanent. Silicon is essential to making of grey cast iron as opposed to white cast iron. The write laser of the CD recorder changes the characteristics of the dye to allow the read laser of a standard CD player to see the data as it would an injection molded compact disc.

. A photosensitive dye is then applied, and then the discs are metallized and lacquer coated. The color of a fracture surface can be used to identify an alloy: carbide impurities allow cracks to pass straight through, resulting in a smooth, "white" surface, while graphite flakes deflect a passing crack and initiate countless new cracks as the material breaks, resulting in a rough surface that appears grey. Recordable compact discs are injection molded with a "blank" data spiral. Cast iron tends to be brittle, unless the name of the particular alloy suggests otherwise. The disc is then metallized with aluminum and lacquer coated. Since cast iron has nearly this composition, its melting temperature of 1420 to 1470 K is about 300 K lower than the melting point of pure iron. Polycarbonate is liquified and injected into the mold cavity where the stamper transfers the pattern of pits and lands to the polycarbonate disc.

The iron-carbon eutectic point lies at 1403 kelvins and 4.3 mass % carbon. It is then plated to make a positive version of the CD. Other elements are then added to the melt before the final form is produced by casting. This dye is then etched, leaving the data track. Carbon and silicon content are reduced to the desired levels, which may be anywhere from 2% to 3.5% for carbon and 1% to 3% for silicon depending on the application. A "stamper" is made from the original media (audio tape, data disc, etc.) by writing to a glass disc (referred to as a glass master) coated with a photosensitive dye with a laser. It is made by remelting pig iron, often along with substantial quantities of scrap iron and scrap steel, and taking various steps to remove undesirable contaminants such as phosphorus and sulfur, which weaken the material. Injection moulding is used to mass produce compact discs.

Cast iron usually refers to grey cast iron, but can mean any of a group of iron-based alloys containing more than 2% carbon (alloys with less carbon are carbon steel by definition). However, in 1985 Yellow Book CD-ROM standard was established by Sony and Philips, which defined a non-volatile optical data storage medium using the same physical format as audio compact discs, readable by a computer with a CD-ROM drive.
. For its first few years of existence, the compact disc was purely an audio format.
. The originally CD-only label Ryko extended this system to the other media when it began making LPs and cassettes so that a digital recording on an LP would be DDA, and so forth.

A notable example is Herb Alpert's Rise album from 1979. A few examples of DAD recordings exist, mostly of works that were originally recorded digitally but later remixed by artists who preferred to work with analog technology. Two examples from 1982 are Signals by Rush and The Nightfly by Donald Fagen. By the time the compact disc was introduced worldwide digital recording and mixing was becoming commonplace among recording artists and producers known for their interest in fidelity.

An early example of an analog recording that was digitally mixed is Fleetwood Mac's 1979 release Tusk. Martin used digital mixing, however, to eliminate the distortion and noise that an analog master tape would introduce (thus ADD). Others, such as former Beatles producer George Martin, felt that the multitrack digital recording technology of the early 1980s had not reached the sophistication of analog systems. Stevie Wonder adopted the technology in early 1979 for Journey Through the Secret Life of Plants and used it on all later recordings.

Many other top recording artists were early adherents of digital recording. It was unmixed, being recorded straight to a two-track 3M digital recorder in the studio. The first digitally recorded (DDD) popular music album was Ry Cooder's Bop Till You Drop, recorded in late 1978. (Unmixed analog recordings are likewise usually described as ADD to denote a single generation of analog recording).

These unmixed digital recordings are still described as DDD since the technology involved is purely digital. In most cases there was no mixing stage involved; a stereo digital recording was made and used unaltered as the master tape for subsequent commercial release. The first 16-bit PCM recording in the United States was made by Thomas Stockham at the Santa Fe Opera in 1976 on a Soundstream recorder. Commercial digital recording of classical and jazz music began in the early 1970s, pioneered by Japanese companies such as Denon, although experimental recordings exist from the 1960s.

Often this code was accompanied by a short description such as "Full Digital Recording" for DDD and "Digitally Mixed Analog Recording" for ADD. Almost all early CDs are "AAD" (analog recording and mixing, digital transfer to CD) as a result. The first letter represents how the album was recorded, the second how it was mixed, and the third how it was transferred (inevitably a D, as the CD is a digital medium). Many CDs, especially classical music and many popular recordings, come with a three-letter code printed on the back known as the SPARS (acronym for Society of Professional Audio Recording Studios) Code, where "A" stands for analog and "D" stands for digital.

Note that the CD+G or “karaoke” extension also uses the R-W subchannels or subcodes to store low resolution graphics. ITTS is also used by Digital Audio Broadcasting or the MiniDisc. The text is stored in a format usable by the Interactive Text Transmission System (ITTS). About 31 megabytes of information can be stored there.

The information is stored in the lead-in area of the CD, where there is roughly five kilobytes of space available, or in the R through W Subchannels on the disc, which are not used by strict Red Book CDs. album name, song name, and artist) on a standards-compliant audio CD. It allows for storage of additional information (e.g. CD-Text is part of the CD+G extension to the Red Book standard for audio CDs.

Channels R…W are unused by Red-Book compliant CDs, and have been used for extensions to the standard. The ISRC is used by the media industry, and contains information about the country of origin, the year of publication, owner of the rights, as well as a serial number, and some additional tags:. It contains positioning information, the Media Catalog Number (MCN), and International Standard Recording Code (ISRC). Channel Q is used for control purposes of more sophisticated players.

Quite a few players ignore it in favor of the Q Channel. Channel P is a simple pause/music flag, which can be used for low-cost search systems. These streams are called "channels", and are labeled starting with the letter P, like so:. Each of these bits corresponds to a separate stream of information.

Each of the 96 subchannel data bytes can be thought of as being divided into eight bits. 1 byte for command, 1 byte for instruction, 2 bytes for parityQ, 16 bytes for data, and 4 bytes parityP. The 96 bytes of subchannel information in each sector contain four packets of 24 bytes apiece:. In each sector there are 2352 bytes (24×98) of audio content data and 96 bytes of subchannel data.

Thus each channel has a bit rate of 7.35 (=44.1/6) kbit/s. The eight bits are used as eight different subcoding channels, and given letters designating their usage: P, Q, …, W. The eight bits of a subcode byte are available for control and display. A frame comprises 33 bytes, of which 24 are audio bytes (six full stereo samples), eight error correction, CIRC-generated, bytes plus one subcode byte.

The data in a CD are arranged in frames. Besides digital audio, a CD contains digital data called "subcode", which is multiplexed with the digital audio. ... An audio CD has a very different structure:.

A CD-ROM (data) sector contains 2352 bytes:. A 1x speed CD drive reads 75 consecutive sectors per second. The playing time is 74 minutes, or 4440 seconds, so that the net capacity of a Mode-1 CD-ROM is 682 MB. The net byte rate of a Mode-1 CD-ROM is 44.1k×2048/(6×98) = 153.6 kB/s.

In a Mode-2 CD-ROM, which is mostly used for video files, there are 2336 user-available bytes per sector. A Mode-1 CD-ROM, which has the full third layer error correction capability, contains a net 2048 bytes of the available 2352 per sector. Note that the CIRC error correction system used in the CD audio format has two interleaved layers. In order to achieve improved error correction and detection, a CD-ROM has a third layer of Reed-Solomon error correction.

The CD-ROM is in essence a data disc, which cannot rely on error concealment, and it requires therefore a higher reliability of the retrieved data. A CD-ROM sector contains 98 frames, and holds 98×24 = 2352 bytes. The synchronization word cannot occur in the normal bit stream, and can thus be used to identify the beginning of a frame. A 27-bit unique synchronization word is added, so that the number of channel bit in a frame totals 588.

In total we have 33*(14+3) = 561 channel bits. The eight bits of a subcode byte are available for control and display. A frame comprises 33 bytes, of which 24 are audio bytes (six full stereo samples), eight error correction, CIRC-generated, bytes plus one subcode byte. Data in a CD-ROM are organized in both frames and sectors.

2×2×6 = 24 bytes. A frame can accommodate six complete 16-bit stereo samples, i.e. The smallest entity in the CD audio format is called a frame. Each 14-bit EFM word alternates with a 3-bit merging word.

Each 14 consecutive bits are grouped and decoded using Eight-to-Fourteen Modulation to get a byte. As bit-times are counted off, a transition (pit-to-land, or land-to-pit) is interpreted as a "1" bit, while a constant region (all-land or all-pit) is interpreted as a "0" bit. Under a microscope, all that is visible is a series of various-sized pits arranged in a long spiral, starting near the inner hole. A "4.7 GB" DVD has a nominal capacity of about 4.38 GiB.

But DVD capacities are given in decimal units. A "700 MB" (or "80 minute") CD has a nominal capacity of about 700 MiB. CD capacities are always given in binary units. However, attempts to combine double LPs onto one CD occasionally resulted in an opposing situation in which the CD would actually offer fewer tracks than the LP equivalent.

CDs would often be released with one or more bonus tracks, enticing consumers to buy the CD for the extra material. The 74-minute playing time of a CD, being more than that of most long-playing vinyl albums, was often used to the format's advantage during the early years when CDs and LPs vied for commerical sales. However, these discs can cause problems in playback when the end of the disc is reached. Another technique to increase the capacity of a disc is store data in the lead out groove that is normally used to indicate the end of a disk, and an extra minute or two of recording is often possible.

This is the limit for most conventional audio CDs today. Using a linear velocity of 1.2 m/s and a track pitch of 1.5 micrometre leads to a playing time of 80 minutes, or a capacity of 700 MB. A disc with data appearing slightly more densely is allowable. If the disc diameter were 115 mm, the maximum playing time would have been 68 minutes, i.e., six minutes less.

With a scanning speed of 1.2 m/s, the playing time is 74 minutes, or around 650 MB of data on a CD-ROM. The program area is 86.05 cm², so that the length of the recordable spiral is 86.05/1.6 = 5.38 km. The main parameters of the CD (taken from the September 1983 issue of the compact disc specification) are as follows:. The Sony PCM-1610 and PCM-1630 are well known examples of PCM adaptors used in conjunction with the Sony U-matic VCR.

There was a long debate over whether to use 14 or 16 bit samples and/or 44,056 or 44,100 samples/s when the Sony/Philips task force designed the compact disc; 16 bits and 44.1 kilo-samples/s prevailed. This system could either store 14-bit samples with some error correction, or 16-bit samples with almost no error correction. Similarly PAL has 294 lines and 50 fields, which gives 44,100 samples/s. A standard NTSC video signal has 245 usable lines per field, and 59.94 fields/s, which works out at 44,056 samples/s.

This technology could store six samples (three samples per each stereo channel) in a single horizontal line. A device that turns an analog audio signal into PCM audio, which in turn is changed into an analog video signal is called a PCM adaptor. The sampling rate of 44.1 kHz is inherited from a method of converting digital audio into an analog video signal for storage on video tape, which was the most affordable way to store it at the time the CD specification was being developed. Reed-Solomon error correction allows the CD to be scratched to a certain degree and still be played back.

In broad terms the format is a two-channel (four-channel sound is an allowed option within the Red Book format, but has never been implemented) stereo 16-bit PCM encoding at a 44.1 kHz sampling rate. Philips is responsible for the licensing program of the intellectual property pertinent to the Compact Disc including the "Compact Disc Digital Audio" logo that appears on the disc. The format of the audio disc, known as the "Red Book" / Sony standard, was laid out by Sony and Philips in 1981. Bulk packaging can be done before or after printing.

Sometimes the spindle of 150 discs are shrinkwrapped together in bulk. The finished assembly has security stickers applied, and is shrinkwrapped with marketing stickers applied. Printing and Packaging: The label is printed onto the disc using a one to six color process (in the case of silk screening), then the printed discs are loaded into a packaging macine that combines a jewel box, tray card, the disc, and booklet. The discs are sampled by QC to ensure quality product.

A laquer is spin coated onto the disc and the disc is tranfered to a spindle. At this point the disc is clear, so a coating of aluminum or gold is applied to the disc for reflectivity. The chamber opens and a robotic arm grabs the disc and transfers it to the next stage. Melted polycarbonate resin is injected into the chamber and the CD is pressed using up to 40 tons of pressure.

Pressing: Each stamper is mounted in an injection moulding machine. This process is also done in a clean room environment. Each stamper is quality checked. Multiple stampers can be made from one glass master.

Stamper Process: Next the glass master is used to create nickel stampers using an electroplating technique. The glass master produced is quality checked before it moves to the next stage. Source material is encoded into the appropriate format whereupon a computer controlled machine "burns" the pits into the emulsion layer of the glass master. The glass is coated with an emulsion.

The nickel is transfered by exciting the nickel to a plasma state whereupon a thin layer of nickel will adhere to the glass. Mastering Process: First, in a clean room, a glass master is prepared by coating a perfectly flat piece of half inch thick circular glass with a layer of nickel. Discs are consequently much easier to ruin by scratching the label side, whereas clear-side scratches can be repaired by refilling them with plastic of similar index of refraction. Pits are much closer to the label side of a disc so that defects and dirt on the clear side can be out of focus during playback.

Most CD manufacturers, dependent on the exact pit geometry such as the slope of the pit edges etc, choose a pit depth of around 90-100 nm, (which is around λ/6n) yielding a sound trade-off between the quality of the push-pull radial tracking and full aperture detection signal. For a maximum push-pull radial tracking signal the best choice is λ/8n = 65 nm. For a maximum full aperture signal, the optimum pit depth is λ/4n = 130 nm (refractive index n=1.5, λ=780 nm). However, the Red Book implicitly specifies the pit depth by specifying the strength of both the push-pull radial tracking signal and full aperture detection signal.

It specifies that the pit depth should be less than (and, thus, not equal) 130 nm. Figure 1, page 8a, of the Red Book specifies many mechanical parameters including the pit depth. This in turn is decoded by reversing the Eight-to-Fourteen Modulation used in mastering the disc, finally revealing the raw data stored on the disc. Instead a change from pit to land or land to pit indicates a one, while no change indicates a zero.

The pits and lands themselves do not represent the zeroes and ones of binary data. By measuring this intensity with a photodiode, one is able to read the data from the disc. The destructive interference thus reduces the intensity of the reflected light compared to when the laser is focused on just a land. The difference in height between pits and lands is one quarter to one sixth of the wavelength of the laser light, leading to a half-wavelength or less phase difference between the light reflected from a pit and from its surrounding land.

A CD is read by focusing a 780 nm wavelength semiconductor laser through the bottom of the polycarbonate layer. The spiral begins at the center of the disc and proceeds outwards to the edge, which allows the different size formats available. To grasp the scale of the pits and land of a CD, if the disc is enlarged to the size of a stadium, a pit would be approximately the size of a grain of sand. The spacing between the tracks is 1.6 μm.

(The areas between pits are known as lands.) Each pit is approximately 100 nm deep by 500 nm wide, and varies from 850 nm to 3.5 μm long. The information on a standard CD is encoded as a spiral track of pits moulded into the top of the polycarbonate layer. There is a 15 mm hole in the centre of the disc, usually used by some form of clamp or clip device within the player to hold it in place and allow it to be rotated by a motor. Some irregularly shaped discs will work with tray loading CD drives if they include a circular ridge on their underside which centers them on the part of the tray designed to hold 80 mm CDs, assuming the tray has such a feature.

Irregularly shaped, non rotationally symmetric discs with an offset centre of mass may also cause damaging vibration if played in computer CD drives, which can operate at a much higher rotational velocity than stand-alone audio CD players. Examples include Business Card CDs in the shape of a rectangular card and CDs shaped like the map of a country etc, although such discs are not always compatible with all CD players — they will work with any machine where the disc is inserted by manually clipping it onto the spindle (the mechanism used in virtually all portable CD players), but may not necessarily be inserted into drives which load the disc from a tray, or pull it into a slot. Other unique shapes and smaller form factors have also been sold or given away as promotional items. Each such "miniCD" or "Maxi CD" can hold 21 minutes of music, or 180 MB of data (this form factor has also been called "CD3", since it is about three inches across).

Japan), much like the old vinyl single. 80 mm discs are also available, a format which is mainly used for audio CD singles in some regions (e.g. Such a standard disc weighs 15 grams. By far the most common is 120 mm in diameter, with a 74-minute audio capacity and a 650 MB data or a 80-minute audio capacity and a 700 MB data (See storage capacity; this form factor has also erroneously been called "CD5" since it is 4 3/4 inches in diameter, about five inches across).

CDs are available in two sizes. Common printing methods for compact discs are silkscreening and offset printing. The lacquer can be printed with a label. Compact discs are made from a 1.2 mm thick disc of polycarbonate plastic coated with a much thinner layer of Super Purity Aluminium (or rarely, gold, used for its data longevity, such as in some limited-edition audiophile CDs) layer which is protected by a film of lacquer.

The CD and its later extensions have been extremely successful: in 2004 the annual worldwide sales of CD-Audio, CD-ROM, and CD-R reached about 30 billion discs. A user-recordable CD for data storage, CD-R, was introduced in the early 1990s, and it became the de facto standard for exchange and archiving of computer data and music. A CD can store around 640 megabytes of data. With this it was now possible to disseminate massive amounts (for the time) of computer data instead of digital sound.

Two years later, in 1985, the CD-ROM (read-only memory) was introduced. From its origins as a music format, Compact Disc has grown to encompass other applications. [2]. It spurred the sale of compact disc players like no other recording before it, helped to drive down the price of players, induced other acts and record labels to release more music on CD and firmly established the format in the mind of the average consumer.

One of the first all-digital rock recordings and the first by a major act, Brothers in Arms played to the strengths of the CD by offering more and longer tracks, running ten minutes longer than the album's concurrent LP and cassette releases. This "highbrow niche" status of the CD format changed dramatically in May, 1985, when UK rock band Dire Straits released the album Brothers in Arms. The far larger popular and rock music industries were slower to adopt the new format, especially in the huge consumer markets in Europe and the United States. The new audio disc was enthusiastically received, especially in the early-adopting classical music and audiophile communities and its handling quality received particular praise.

This event is often seen as the "Big Bang" of the digital audio revolution. The Compact Disc reached the market in late 1982 in Asia and early the following year in other markets. According to Philips, the Compact Disc was thus "invented collectively by a large group of people working as a team."[1]. The Compact Disc Story, told by a former member of the taskforce, gives background information on the many technical decisions made, including the choice of the sampling frequency, playing time, and disc diameter.

Philips also 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. Philips contributed the general manufacturing process, based on the video Laserdisc technology. After a year of experimentation and discussion, the taskforce produced the "Red Book", the Compact Disc standard. Prominent members of the task force were Kees Immink and Toshitada Doi.

In 1979 Philips and Sony decided to join forces, setting up a joint task force of engineers whose mission was to design the new digital audio disc. At the end of the 1970s, Philips, Sony, and other companies presented prototypes of digital audio discs. 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. .

Online services such as CDDB were developed to work around these shortcomings in the computer age. As a result, the original CD format has a number of limitations; no built-in track names or disc naming for example. Only later did the concept of an 'audio file' arise, and the generalising of this to any data file. The design of the CD was originally conceived as an evolution of the gramophone record, rather than primarily as a data storage medium.

Compact disc technology was later adapted for use as a data storage device, known as a CD-ROM. They hold about 20 minutes of audio. The 80 mm discs are used as "CD-singles" or novelty "business-card CDs". The 120 mm discs can hold 74 minutes of audio, and versions holding 80, 90 or even 99 minutes have been introduced.

Standard compact discs have a diameter of 120 mm, though 80 mm versions exist in circular and "business-card" forms. An audio CD consists of several stereo tracks stored using 16-bit PCM coding at a sampling rate of 44.1 kHz. A standard compact disc, often known as an "audio CD" to differentiate it from later variants, stores audio data in a format compliant with the red book standard. It is the standard playback format for commercial audio recordings today.

A compact disc (or CD) is an optical disc used to store digital data, originally developed for storing digital audio. ISBN 895793008. Middleton, Wisconsin: A-R Editions. The Compact Disc Handbook.

Pohlmann (1992). Kenneth C. 458-465, May 1998 [4]. Kees Immink, The Compact Disc Story, AES Journal, pp.

AAD: analog tape recorder used during session recording and subsequent mixing and/or editing, digital tape recorder used during mastering (transcription). ADD: analog tape record used during session recording, digital tape recorder used during subsequent mixing and/or editing and during mastering (transcription). DDD: digital tape recorder used during session recording, mixing and/or editing, and mastering (transcription). 276 bytes: error correction.

8 bytes: null. 4 bytes: error detection. 2 048 bytes: user data. 4 bytes: sector ID.

12 bytes: sync. Outer radius program area: 58 mm. Inner radius program area: 25 mm. Disc thickness: 1.2 mm.

Disc diameter 120 mm. Track pitch: 1.6 μm. Scanning velocity: 1.2–1.4 m/s (constant linear velocity) - Equivalent to about 500 rpm at the inside of the disc, or about 200 rpm at the outside edge.