Sound recording and reproduction（2）

Tape enabled the radio industry for the first time to pre-record many sections of program content such as advertising, which formerly had to be presented live, and it also enabled the creation and duplication of complex, high-fidelity(SONY VAIO VGN-FZ11m Battery), long-duration recordings of entire programs. It also, for the first time, allowed broadcasters, regulators and other interested parties to undertake comprehensive logging of radio broadcasts(SONY VAIO VGN-FZ11z Battery). Innovations like multitracking and tape echo enabled radio programs and advertisements to be pre-produced to a level of complexity and sophistication that was previously unattainable and tape also led to significant changes to the pacing of program content, thanks to the introduction of the endless-loop broadcast cartridge(SONY VAIO VGN-FZ11l Battery).

Stereo and hi-fi

See also: Stereophonic sound and High fidelity

In 1881, it was noted during experiments in transmitting sound from the Paris Opera that it was possible to follow the movement of singers on the stage if earpieces connected to different microphones were held to the two ears. However, this observation was not followed up or investigated further at the time(SONY VAIO VGN-FZ140E Battery).

In 1931 Alan Blumlein, a British electronics engineer working for EMI, designed a way to make the sound of an actor in a film follow their movement across the screen. In December 1931 he submitted a patent including the idea(SONY VAIO VGN-FZ260E Battery), and in 1933 this became UK patent number 394,325. Over the next two years, Blumlein developed stereo microphones and a stereo disc-cutting head, and recorded a number of short films with stereo soundtracks(SONY VAIO VGN-FZ150E Battery).

Magnetic tape enabled the development of the first practical commercial sound systems that could record and reproduce high-fidelity stereophonic sound. The experiments with stereo during the 1930s and 1940s were hampered by problems with synchronization(SONY VAIO VGN-FZ190 Battery). A major breakthrough in practical stereo sound was made by Bell Laboratories, who in 1937 demonstrated a practical system of two-channel stereo, using dual optical sound tracks on film. Major movie studios quickly developed three-track and four-track sound systems(SONY VAIO VGN-FZ460E Battery), and the first stereo sound recording for a commercial film was made by Judy Garland for the MGM movie Listen, Darling in 1938.

The first movie commercially released with a stereo soundtrack was Walt Disney's Fantasia, released in 1940(SONY VAIO VGN-FZ280E Battery). The original 1941 release of this production used the "Fantasound" sound system. This system employed a separate film for the sound, which ran in synchronism with the film carrying the picture. On this sound film were four double-width optical soundtracks, three of which carried left(SONY VAIO VGN-FZ440N Battery), center and right audio whilst the fourth was a "control" track on which were recorded three tones which controlled the playback volume of the three audio channels. Because of the complex equipment required to present it, it was shown as a roadshow, but only in the United States(SONY VAIO VGN-FZ32 Battery). Regular releases of the film were on standard mono optical 35 mm stock until 1956 when the film was released with a stereo soundtrack using the "Cinemascope" four-track magnetic sound system(sony vgp-bpl9 battery).

German audio engineers working on magnetic tape are reported to have developed stereo recording by 1943, but it was not until the introduction of the first commercial two-track tape recorders by Ampex in the late 1940s that stereo tape recording became commercially feasible(SONY vgp-bps9 battery). However, despite the availability of multitrack tape, stereo did not become the standard system for commercial music recording for some years and it remained a specialist market during the 1950s(SONY VAIO VGN-FZ11S Battery). This changed after the late 1957 introduction of the "Westrex stereo phonograph disc", which used the groove format developed earlier by Blumlein. Decca Records in England came out with FFRR (Full Frequency Range Recording) in the 1940s which became internationally accepted and a worldwide standard for higher quality recordings on vinyl records(SONY VAIO VGN-FZ Battery). The Ernest Ansermet recording of Igor Stravinsky's Petrushka was key in the development of full frequency range records and alerting the listening public to high fidelity in 1946(SONY VGP-BPS8 battery).

Most pop singles were mixed into monophonic sound until the mid 1960s, and it was common for major pop releases to be issued in both mono and stereo until the early 1970s(Sony VAIO PCG-5K1L battery). Many Sixties pop albums now available only in stereo were originally intended to be released only in mono, and the so-called "stereo" version of these albums were created by simply separating the two tracks of the master tape. In the mid Sixties, as stereo became more popular(Sony VAIO PCG-6W2L battery), many mono recordings (such as The Beach Boys' Pet Sounds) were remastered using the so-called "fake stereo" method, which spread the sound across the stereo field by directing higher-frequency sound into one channel and lower-frequency sounds into the other(Sony VAIO PCG-7112L battery).

1950s and beyond

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Magnetic tape transformed the recording industry, and by the late-1950s the vast majority of commercial recordings were being mastered on tape. The electronics revolution that followed the invention of the transistor brought other radical changes(Sony VAIO PCG-8Z2L battery), the most important of which was the introduction of the world's first "personal music device", the miniaturized transistor radio, which became a major consumer luxury item in the 1960s(Sony VAIO PCG-8Y2L battery), transforming radio broadcasting from a static group experience into a mobile, personal listening activity. An early multitrack recording made using magnetic tape was "How High the Moon" by Les Paul, on which Paul played eight overdubbed guitar tracks(Sony VAIO PCG-8Y1L battery). In the 1960s Brian Wilson of The Beach Boys, Frank Zappa and The Beatles (with producer George Martin) were among the first popular artists to explore the possibilities of multitrack techniques and effects on their landmark albums Pet Sounds, Freak Out! and Sgt. Pepper's Lonely Hearts Club Band(Sony VAIO PCG-7Z2L battery).

The next important innovation was small cartridge based tape systems of which the compact cassette, introduced by the Philips electronics company in 1964 is the best known. It eventually entirely replaced the competing formats(Sony VAIO PCG-7Z1L battery), the larger 8-track tape (used primarily in cars) and the fairly similar 'Deutsche Cassette' developed by the German company Grundig. This latter system was not particularly common in Europe and practically unheard of in America. The compact cassette became a major consumer audio format and advances in microelectronics eventually allowed the development of the Sony Walkman, introduced in the 1970s(Sony VAIO PCG-7133L battery), which was the first personal music player and gave a major boost to the mass distribution of music recordings. Cassettes became the first successful consumer recording/re-recording medium. The gramophone record was a pre-recorded playback only medium, and reel-to-reel tape was too difficult for most consumers and far less portable(Sony VAIO PCG-7113L battery).

A key advance in audio fidelity came with the Dolby A noise reduction system, invented by Ray Dolby and introduced in 1966. A competing system dbx, invented by David Blackmer, found most success in professional audio(Sony VAIO PCG-6W3L battery). A simpler variant of Dolby's noise reduction system, known as Dolby B greatly improved the sound of cassette tape recordings by reducing the practical effect of the recorded hiss inherent in the narrow tape used(Sony VAIO PCG-7111L battery). It, and variants, also eventually found wide application in the recording and film industries. Dolby B was crucial to the popularisation and commercial success of the compact cassette as a domestic recording and playback medium(Sony VAIO PCG-6W1L battery), and became a part of the booming "hi-fi" market of the 1970s and beyond. The compact cassette also benefited enormously from developments in the tape material itself as materials with wider frequency responses and lower inherent noise were developed, often based on cobalt and/or chrome oxides as the magnetic material instead of the more usual iron oxide(Sony VAIO PCG-6V1L battery).

The multitrack audio cartridge had been in wide use in the radio industry, from the late 1950s to the 1980s, but in the 1960s the pre-recorded 8-track cartridge was launched as a consumer audio format by Bill Lear of the Lear Jet aircraft company (and although its correct name was the 'Lear Jet Cartridge'(Sony VAIO PCG-6S3L battery), it was seldom referred to as such). Aimed particularly at the automotive market, they were the first practical, affordable car hi-fi systems, and could produce superior sound quality to the compact cassette(Sony VAIO PCG-6S2L battery). However the smaller size and greater durability — augmented by the ability to create home-recorded music "compilations" since 8-track recorders were rare — saw the cassette become the dominant consumer format for portable audio devices in the 1970s and 1980s(Sony VAIO PCG-5L1L battery).

There had been experiments with multi-channel sound for many years — usually for special musical or cultural events — but the first commercial application of the concept came in the early 1970s with the introduction of Quadraphonic sound(Sony VAIO PCG-5K2L battery). This spin-off development from multitrack recording used four tracks (instead of the two used in stereo) and four speakers to create a 360-degree audio field around the listener. Following the release of the first consumer 4-channel hi-fi systems, a number of popular albums were released in one of the competing four-channel formats(Sony VAIO PCG-5J2L battery); among the best known are Mike Oldfield's Tubular Bells and Pink Floyd's The Dark Side of the Moon. Quadraphonic sound was not a commercial success, partly because of competing and somewhat incompatible four-channel sound systems (e.g., CBS, JVC, Dynaco and others all had systems) (Sony VAIO PCG-5J1L battery) and generally poor quality, even when played as intended on the correct equipment, of the released music. It eventually faded out in the late 1970s, although this early venture paved the way for the eventual introduction of domestic Surround Sound systems in home theatre use(Sony VAIO PCG-5G3L battery), which have gained enormous popularity since the introduction of the DVD. This widespread adoption has occurred despite the confusion introduced by the multitude of available surround sound standards(Sony VAIO PCG-5G2L battery).

The replacement of the thermionic valve (vacuum tube) by the smaller, cooler and less power-hungry transistor also accelerated the sale of consumer high-fidelity "hi-fi" sound systems from the 1960s onward. In the 1950s most record players were monophonic and had relatively low sound quality(Sony VGP-BPS21A/B battery); few consumers could afford high-quality stereophonic sound systems. In the 1960s, American manufacturers introduced a new generation of "modular" hi-fi components — separate turntables, pre-amplifiers, amplifiers, both combined as integrated amplifiers, tape recorders, and other ancillary equipment (like the graphic equaliser) (Sony VGP-BPS21/S battery), which could be connected together to create a complete home sound system. These developments were rapidly taken up by Japanese electronics companies, which soon flooded the world market with relatively cheap, high-quality components. By the 1980s, corporations like Sony had become world leaders in the music recording and playback industry(Sony VGP-BPS21B battery).

Digital recording

Main article: Digital recording

See also: Pulse code modulation, Digital audio, Hard disk recorder, and Digital audio workstation(Sony VGP-BPS21 battery)

Graphical representation of a sound wave in analog (red) and 4-bit digital (black).

The invention of digital sound recording and later the compact disc in 1982 brought significant improvements in the durability of consumer recordings(Sony VGN-FW31J battery). The CD initiated another massive wave of change in the consumer music industry, with vinyl records effectively relegated to a small niche market by the mid-1990s(Sony VGP-BPS13A/S battery). However, the introduction of digital systems was initially fiercely resisted by the record industry which feared wholesale piracy on a medium which was able to produce perfect copies of original released recordings. However, the industry had to bow to the inevitable(Sony VGP-BPS13B/S battery), but not without using various protection system (principally Serial Copy Management System, or SCMS).

A digital sound recorder from Sony

The most recent and revolutionary developments have been in digital recording(Sony VGP-BPS13S battery), with the development of various uncompressed and compressed digital audio file formats, processors capable and fast enough to convert the digital data to sound in real time, and inexpensive mass storage(Sony VGP-BPS13/B battery). This generated a new type of portable digital audio player. The minidisc player, using ATRAC compression on small, cheap, re-writeable discs was introduced in the 1990s but became obsolescent as solid-state non-volatile flash memory dropped in price(Sony VGP-BPS13/S battery). As technologies which increase the amount of data that can be stored on a single medium, such as Super Audio CD, DVD-A, Blu-ray Disc and HD DVD become available, longer programs of higher quality fit onto a single disc(Sony VGP-BPS13A/B battery). Sound files are readily downloaded from the Internet and other sources, and copied onto computers and digital audio players. Digital audio technology is used in all areas of audio, from casual use of music files of moderate quality to the most demanding professional applications(Sony VGP-BPS13B/B battery). New applications such as internet radio and podcasting have appeared.

Technological developments in recording and editing have transformed the record, movie and television industries in recent decades. Audio editing became practicable with the invention of magnetic tape recording(Sony VGN-FZ11E battery), but digital audio and cheap mass storage allows computers to edit audio files quickly, easily, and cheaply. Today, the process of making a recording is separated into tracking(Sony VGN-FZ440N battery), mixing and mastering. Multitrack recording makes it possible to capture signals from several microphones, or from different 'takes' to tape or disc, with maximized headroom and quality(Sony Vaio VGN-FZ21J battery), allowing previously unavailable flexibility in the mixing and mastering stages for editing, level balancing, compressing and limiting, adding effects such as reverberation, equalisation, flanging, and much more(Sony Vaio VGN-FZ31J battery ).

Digital recording and processing software

There are many different digital audio recording and processing programs running under several computer operating systems for all purposes, from professional through serious amateur to casual user(Sony Vaio VGN-FZ31B battery).

A comprehensive list of digital recording applications is available on the digital audio workstation page(Sony VGN-FZ18L battery).

Digital dictation software for recording and transcribing speech has different requirements; intelligibility and flexible playback facilities are priorities, while a wide frequency range and high audio quality are not(Sony VGN-FW11M battery).

Sound recording and reproduction（1）

Sound recording and reproduction is an electrical or mechanical inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects(SONY Vaio VGN-FW31J Battery). The two main classes of sound recording technology are analog recording and digital recording. Acoustic analog recording is achieved by a small microphone diaphragm that can detect changes in atmospheric pressure (acoustic sound waves) (SONY Vaio VGN-FW32J Battery)and record them as a graphic representation of the sound waves on a medium such as a phonograph (in which a stylus senses grooves on a record) (SONY Vaio VGN-FW17W Battery). In magnetic tape recording, the sound waves vibrate the microphone diaphragm and are converted into a varying electric current, which is then converted to a varying magnetic field by an electromagnet(SONY Vaio VGN-FW31E Battery), which makes a representation of the sound as magnetized areas on a plastic tape with a magnetic coating on it. Analog sound reproduction is the reverse process, with a bigger loudspeaker diaphragm causing changes to atmospheric pressure to form acoustic sound waves(SONY Vaio VGN-FW139E Battery). Electronically generated sound waves may also be recorded directly from devices such as an electric guitar pickup or a synthesizer, without the use of acoustics in the recording process other than the need for musicians to hear how well they are playing during recording sessions(SONY Vaio VGN-FW139E/H Battery).

Digital recording and reproduction converts the analog sound signal picked up by the microphone to a digital form by a process of digitization, allowing it to be stored and transmitted by a wider variety of media(SONY Vaio VGN-FW465J Battery). Digital recording stores audio as a series of binary numbers representing samples of the amplitude of the audio signal at equal time intervals, at a sample rate so fast that the human ear perceives the result as continuous sound(SONY Vaio VGN-FW31M Battery). Digital recordings are considered higher quality than analog recordings not necessarily because they have higher fidelity (wider frequency response or dynamic range) (SONY VAIO VGN-FZ21E Battery), but because the digital format can prevent much loss of quality found in analog recording due to noise and electromagnetic interference in playback, and mechanical deterioration or damage to the storage medium. A digital audio signal must be reconverted to analog form during playback before it is applied to a loudspeaker or earphones(SONY VAIO VGN-FZ21Z Battery).

History

Origins

435 HZ

This 1859 phonautogram by Édouard-Léon Scott de Martinville is the earliest known modern sound recording(SONY VAIO VGN-FZ21J Battery).

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Au Clair de la Lune

This 1860 phonautogram by Édouard-Léon Scott de Martinville is the first known sound recording with a human voice.

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The automatic reproduction of music can be traced back as far as the 9th century, when the Banū Mūsā brothers invented "the earliest known mechanical musical instrument", in this case a hydropowered organ which played interchangeable cylinders automatically(SONY Vaio VGN-FW11M Battery). According to Charles B. Fowler, this "cylinder with raised pins on the surface remained the basic device to produce and reproduce music mechanically until the second half of the nineteenth century." The Banu Musa also invented an automatic flute player which appears to have been the first programmable machine(SONY Vaio VGN-FW11S Battery).

In the 14th century, Flanders introduced a mechanical bell-ringer controlled by a rotating cylinder. Similar designs appeared in barrel organs (15th century), musical clocks (1598), barrel pianos (1805), and musical boxes (1815) (SONY Vaio VGN-FW21E Battery).

All of these machines could play stored music, but they could not play arbitrary sounds, could not record a live performance, and were limited by the physical size of the medium. The first device that could record sound mechanically (but could not play it back) was the phonautograph(SONY Vaio VGN-FW21J Battery), developed in 1857 by Parisian inventor Édouard-Léon Scott de Martinville. The earliest known recordings of the human voice were phonautograms also made in 1857. These earliest known recordings include a dramatic reading in French of Shakespeare's Othello and music played on a guitar and trumpet(SONY Vaio VGN-FW21L Battery). The recordings consist of groups of wavy lines scratched by a stylus onto fragile paper that was blackened by the soot from an oil lamp.[4] One of his phonautograms of Au Clair de la Lune, a French folk song, was digitally converted to sound in 2008(SONY Vaio VGN-FW21M Battery). While this is an interesting playback that sounds like a girl singing, the creator of this recording, Patrick Feaster of Indiana University in Bloomington, reports that phonautograms his team had previously transcribed, using a laser as a virtual stylus, had been played back at twice the actual speed(SONY VGP-BPS13Q Battery). What sounded like a girl singing the French folksong was actually Léon Scott singing, Feaster concluded in May, 2009. Since the above recording was recovered, the same team have since recovered a recording of a 435-Hz tuning fork (at that time the French standard concert pitch for A' — now 440 Hz). The tuning fork is barely audible(SONY VGP-BPS13B/Q Battery).

The player piano, first demonstrated in 1876, used a punched paper scroll that could store an arbitrarily long piece of music. This piano roll moved over a device known as the 'tracker bar', which first had 58 holes, was expanded to 65 and then was upgraded to 88 holes (generally, one for each piano key) (SONY VGN NR11S/S battery). When a perforation passed over the hole, the note sounded. Piano rolls were the first stored music medium that could be mass-produced, although the hardware to play them was much too expensive for personal use(SONY VGN NR11M/S battery). Technology to record a live performance onto a piano roll was not developed until 1904. Piano rolls have been in continuous mass production since around 1898. A 1908 U.S. Supreme Court copyright case noted that, in 1902 alone(SONY VGN NR11Z/S battery), there were between 70,000 and 75,000 player pianos manufactured, and between 1,000,000 and 1,500,000 piano rolls produced. The use of piano rolls began to decline in the 1920s although one type is still being made today(SONY VGN NR11Z/T battery). The fairground organ, developed in 1892, used a similar system of accordion-folded punched cardboard books.

Phonograph

Main article: Phonograph

Phonograph cylinder

Frances Densmore recording Blackfoot chief Mountain Chief on a cylinder phonograph for the Bureau of American Ethnology (1916) (SONY VGP-BPS13A/Q Battery)

"Kham Hom" ("Sweet Words")

Phonograph cylinder recording of Siamese (Thai) musicians visiting Berlin, Germany in 1900.

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The first practical sound recording and reproduction device was the mechanical phonograph cylinder, invented by Thomas Edison in 1877 and patented in 1878. The invention soon spread across the globe and over the next two decades the commercial recording(SONY VGP-BPS21/S Battery), distribution and sale of sound recordings became a growing new international industry, with the most popular titles selling millions of units by the early 1900s. The development of mass-production techniques enabled cylinder recordings to become a major new consumer item in industrial countries and the cylinder was the main consumer format from the late 1880s until around 1910(SONY VGP-BPS21 Battery).

Disc phonograph

The next major technical development was the invention of the gramophone disc, generally credited to Emile Berliner and commercially introduced in the United States in 1889. Discs were easier to manufacture, transport and store(SONY VGP-BPS21B Battery), and they had the additional benefit of being louder (marginally) than cylinders, which by necessity, were single-sided(SONY VGP-BPS21A/B Battery). Sales of the Gramophone record overtook the cylinder ca. 1910, and by the end of World War I the disc had become the dominant commercial recording format. Edison, who was the main producer of cylinders, created the Edison Disc Record in an attempt to regain his market(SONY VAIO PCG-5K1L battery). In various permutations, the audio disc format became the primary medium for consumer sound recordings until the end of the 20th century, and the double-sided 78 rpm shellac disc was the standard consumer music format from the early 1910s to the late 1950s(SONY VAIO PCG-6W2L battery).

Although there was no universally accepted speed, and various companies offered discs that played at several different speeds, the major recording companies eventually settled on a de facto industry standard of nominally 78 revolutions per minute(SONY VAIO PCG-7112L battery), though the actual speed differed between America and the rest of the world. The specified speed was 78.26 rpm in America and 77.92 rpm throughout the rest of the world, the difference in speeds a result of the difference in cycle frequencies of the AC power driving the synchronous motor) and available gearing ratio(SONY VAIO PCG-8Z1L battery)s. The nominal speed of the disc format gave rise to its common nickname, the "seventy-eight" (though not until other speeds had become available). Discs were made of shellac or similar brittle plastic-like materials, played with needles made from a variety of materials including mild steel, thorn and even sapphire. Discs had a distinctly limited playing life which was heavily dependent on how they were reproduced(SONY VAIO PCG-8Z2L battery).

The earlier, purely acoustic methods of recording had limited sensitivity and frequency range. Mid-frequency range notes could be recorded but very low and very high frequencies could not. Instruments such as the violin transferred poorly to disc(SONY VAIO PCG-8Y2L battery); however this was partially solved by retrofitting a conical horn to the sound box of the violin. The horn was no longer required once electrical recording was developed(SONY VAIO PCG-8Y1L battery).

The Vinyl microgroove was invented by a Hungarian engineer Peter Carl Goldmark. The vinyl microgroove record was introduced in the late 1940s, and the two main vinyl formats — the 7-inch single turning at 45 rpm and the 12-inch LP (long-playing) record turning at 33 1/3 rpm — had totally replaced the 78 rpm shellac (SONY VAIO PCG-7Z2L battery) (sometimes vinyl) disc by the end of the 1950s. Vinyl offered improved performance, both in stamping and in playback, and came to be generally played with polished diamond styli, and when played properly (SONY VAIO PCG-7Z1L battery) (precise tracking weight, etc.) offered longer life. Vinyl records were, over-optimistically, advertised as "unbreakable". They were not, but were much less brittle and breakable than shellac. Nearly all were tinted black, but some were colored, as red, swirled, translucent, etc(SONY VAIO PCG-7133L battery).

Electrical recording

RCA-44, a classic ribbon microphone

Sound recording began as a mechanical process and remained so until the early 1920s (with the exception of the 1899 Telegraphone) when a string of groundbreaking inventions in the field of electronics revolutionised sound recording and the young recording industry(SONY VAIO PCG-7113L battery). These included sound transducers such as microphones and loudspeakers, and various electronic devices such as the mixing desk, designed for the amplification and modification of electrical sound signals(SONY VAIO PCG-6W3L battery).

After the Edison phonograph itself, arguably the most significant advances in sound recording, were the electronic systems invented by two American scientists between 1900 and 1924(SONY VAIO PCG-7111L battery). In 1906 Lee De Forest invented the "Audion" triode vacuum-tube, electronic valve, which could greatly amplify weak electrical signals, (one early use was to amplify long distance telephone in 1915) which became the basis of all subsequent electrical sound systems until the invention of the transistor(SONY VAIO PCG-6W1L battery). The valve was quickly followed by the invention of the Regenerative circuit, Super-Regenerative circuit and the Superheterodyne receiver circuit, all of which were invented and patented by the young electronics genius Edwin Armstrong between 1914 and 1922(SONY VAIO PCG-6V1L battery). Armstrong's inventions made higher fidelity electrical sound recording and reproduction a practical reality, facilitating the development of the electronic amplifier and many other devices; after 1925 these systems had become standard in the recording and radio industry(SONY VAIO PCG-6S3L battery).

While Armstrong published studies about the fundamental operation of the triode vacuum tube before World War I, inventors like Orlando R. Marsh and his Marsh Laboratories(SONY VAIO PCG-6S2L battery), as well as scientists at Bell Telephone Laboratories, achieved their own understanding about the triode and were utilizing the Audion as a repeater in weak telephone circuits(SONY VAIO PCG-5J2L battery). By 1925 it was possible to place a long distance telephone call with these repeaters between New York and San Francisco in 20 minutes, both parties being clearly heard. With this technical prowess, Joseph P. Maxfield and Henry C(SONY VAIO PCG-5L1L battery). Harrison from Bell Telephone Laboratories were skilled in using mechanical analogs of electrical circuits and applied these principles to sound recording and reproduction. They were ready to demonstrate their results by 1924 using the Wente condenser microphone and the vacuum tube amplifier to drive the "rubber line" wax recorder to cut a master audio disc(SONY VAIO PCG-5K2L battery).

Meanwhile, radio continued to develop. Armstrong's groundbreaking inventions (including FM radio) also made possible the broadcasting of long-range, high-quality radio transmissions of voice and music(SONY VAIO PCG-5J1L battery). The importance of Armstrong's Superheterodyne circuit cannot be over-estimated — it is the central component of almost all analog amplification and both analog and digital radio-frequency transmitter and receiver devices to this day(SONY VAIO PCG-5G3L battery).

Beginning during World War One, experiments were undertaken in the United States and Great Britain to reproduce among other things, the sound of a Submarine (u-boat) for training purposes(SONY VAIO PCG-5G2L battery). The acoustical recordings of that time proved entirely unable to reproduce the sounds, and other methods were actively sought. Radio had developed independently to this point, and now Bell Laboritories sought a marriage of the two disparate technologies(SONY VGP-BPS13B/S Battery), greater than the two separately. The first experiments were not very promising, but by 1920 greater sound fidelity was achieved using the electrical system than had ever been realized acoustically. One early recording made without fanfare or announcement was the dedication of the Tomb of the Unknown Soldier at Arlington Cemetery(SONY VGP-BPS13S Battery).

By early 1924 such dramatic progress had been made, that Bell Labs arranged a demonstration for the leading recording companies, the Victor Talking Machine Company, and the Columbia Phonograph Co. (SONY VGP-BPS13A/S Battery) (Edison was left out due to their decreasing market share and a stubborn Thomas Edison). Columbia, always in financial straits, could not afford it, and Victor, essentially leaderless since the mental collapse of founder Eldridge Johnson, left the demonstration without comment(Sony VAIO VGN-FZ15G Battery). English Columbia, by then a separate company, got hold of a test pressing made by Pathé from these sessions, and realized the immediate and urgent need to have the new system. Bell was only offering its method to United States companies, and to circumvent this, Managing Director Louis Sterling of English Columbia(Sony VAIO VGN-FZ15T Battery), bought his once parent company, and signed up for electrical recording. Although they were contemplating a deal, Victor Talking Machine was apprised of the new Columbia deal, so they too quickly signed. Columbia made its first released electrical recordings on February 25(SONY VGP-BPS13/B Battery), 1925, with Victor following a few weeks later. The two then agreed privately to "be quiet" until November 1925, by which time enough electrical repertory would be available(Dell N3010 Battery).

Other recording formats

In the 1920s, the early talkies featured the new sound-on-film technology which used photoelectric cells to record and reproduce sound signals that were optically recorded directly onto the movie film(Dell INSPIRON 1464 battery). The introduction of talking movies, spearheaded by The Jazz Singer in 1927 (though it used a sound on disk technique, not a photoelectric one) (Dell INSPIRON 1520 battery), saw the rapid demise of live cinema musicians and orchestras. They were replaced with pre-recorded soundtracks, causing the loss of many jobs. The American Federation of Musicians took out ads in newspapers, protesting the replacement of real musicians with mechanical playing devices, especially in theatres(Dell INSPIRON E1505 battery).

This period also saw several other historic developments including the introduction of the first practical magnetic sound recording system, the magnetic wire recorder, which was based on the work of Danish inventor Valdemar Poulsen(SONY VGP-BPS13B/B Battery). Magnetic wire recorders were effective, but the sound quality was poor, so between the wars they were primarily used for voice recording and marketed as business dictating machines(SONY VGP-BPS13 Battery). In the 1930s radio pioneer Guglielmo Marconi developed a system of magnetic sound recording using steel tape. This was the same material used to make razor blades, and not surprisingly the fearsome Marconi-Stille recorders were considered so dangerous that technicians had to operate them from another room for safety(SONY VAIO VGN-FZ31B Battery). Because of the high recording speeds required, they used enormous reels about one metre in diameter, and the thin tape frequently broke, sending jagged lengths of razor steel flying around the studio(SONY VAIO VGN-FZ31M Battery).

The K1 Magnetophon was the first practical tape recorder, developed by AEG in Germany in 1935. The other major invention in sound recording in this period was the optical sound-on-film system, also generally credited to Lee De Forest(SONY VAIO VGN-FZ31J Battery). Although famous early "Talkies" like The Jazz Singer used a sound-on-disc system, the film industry rapidly adopted the optical sound-on-film system and it revolutionised the movie industry in the 1930s(SONY VAIO VGN-FZ31E Battery), ushering in the era of 'talking pictures'. Optical sound-on-film, based on the photoelectric cell, became the standard film audio system throughout the world and remains so for theatrical release prints despite attempts in the 1950s to substitute magnetic recording methods(Sony Vaio VGN-FZ31S battery). Currently all release prints on 35mm film include an analogue optical soundtrack (usually stereo with Dolby SR noise reduction). In addition an optically recorded digital soundtrack in Dolby Digital and/or Sony SDDS form is likely to be present. Optically recorded timecode is also commonly found in order to synchronise CDROMs containing a DTS soundtrack(SONY VAIO VGN-FZ31z Battery).

Magnetic tape

Main article: magnetic tape sound recording

Other important inventions of this period were magnetic tape and the tape recorder (Telegraphone). Paper-based tape was first used but was soon superseded by polyester and acetate backing due to dust drop and hiss. Acetate was more brittle than polyester and snapped easily(SONY VAIO VGN-FZ38M Battery). This technology, the basis for almost all commercial recording from the 1950s to the 1980s, was invented by German audio engineers in the 1930s, who also discovered the technique of AC biasing, which dramatically improved the frequency response of tape recordings(SONY VAIO VGN-FZ210CE Battery). Tape recording was perfected just after the war by American audio engineer John T. Mullin with the help of Crosby Enterprises (Bing Crosby), whose pioneering recorders were based on captured German recorders, and the Ampex company produced the first commercially available tape recorders in the late 1940s(SONY VAIO VGN-FZ160 Battery).

A typical Compact Cassette

Magnetic tape brought about sweeping changes in both radio and the recording industry. Sound could be recorded, erased and re-recorded on the same tape many times, sounds could be duplicated from tape to tape with only minor loss of quality(SONY VAIO VGN-FZ21 Battery), and recordings could now be very precisely edited by physically cutting the tape and rejoining it. Within a few years of the introduction of the first commercial tape recorder, the Ampex 200 model, launched in 1948(SONY VAIO VGN-FZ410 Battery), American musician-inventor Les Paul had invented the first multitrack tape recorder, bringing about another technical revolution in the recording industry(SONY VAIO VGN-FZ21m Battery). Tape made possible the first sound recordings totally created by electronic means, opening the way for the bold sonic experiments of the Musique Concrète school and avant garde composers like Karlheinz Stockhausen, which in turn led to the innovative pop music recordings of artists such as Frank Zappa, The Beatles and The Beach Boys(SONY VAIO VGN-FZ18m Battery).

iPhone（2）

Multimedia

The layout of the music library is similar to that of an iPod or current Symbian S60 phones. The iPhone can sort its media library by songs, artists, albums, videos, playlists, genres, composers, podcasts, audiobooks, and compilations(Sony VAIO PCG-5K1L battery). Options are always presented alphabetically, except in playlists, which retain their order from iTunes. The iPhone uses a large font that allows users plenty of room to touch their selection(SONY VGP-BPS8 battery). Users can rotate their device horizontally to landscape mode to access Cover Flow. Like on iTunes, this feature shows the different album covers in a scroll-through photo library(SONY VAIO VGN-FZ Battery). Scrolling is achieved by swiping a finger across the screen. Alternatively, headset controls can be used to pause, play, skip, and repeat tracks. On the iPhone 3GS(SONY VAIO VGN-FZ11S Battery), the volume can be changed with the included Apple Earphones, and the Voice Control feature can be used to identify a track, play songs in a playlist or by a specific artist, or create a Genius playlist(SONY vgp-bps9 battery).

The photo display application supports both portrait and landscape orientations.

The iPhone supports gapless playback. Like the fifth generation iPods introduced in 2005, the iPhone can play digital video(sony vgp-bpl9 battery), allowing users to watch TV shows and movies in widescreen. Double-tapping switches between widescreen and fullscreen video playback(SONY VAIO VGN-FZ32 Battery).

The iPhone allows users to purchase and download songs from the iTunes Store directly to their iPhone. The feature originally required a Wi-Fi network, but now can use the cellular data network if one is not available(SONY VAIO VGN-FZ440N Battery).

The iPhone includes software that allows the user to upload, view, and e-mail photos taken with the camera. The user zooms in and out of photos by sliding two fingers further apart or closer together, much like Safari(SONY VAIO VGN-FZ280E Battery). The Camera application also lets users view the camera roll, the pictures that have been taken with the iPhone's camera. Those pictures are also available in the Photos application, along with any transferred from iPhoto or Aperture on a Mac, or Photoshop in Windows(SONY VAIO VGN-FZ460E Battery).

Internet connectivity

Wikipedia Main Page on the iPhone's Safari web browser in landscape mode

Internet access is available when the iPhone is connected to a local area Wi-Fi or a wide area GSM or EDGE network, both second-generation (2G) wireless data standards(SONY VAIO VGN-FZ190 Battery). The iPhone 3G introduced support for third-generation UMTS and HSDPA 3.6, but not HSUPA networks, and only the iPhone 3GS and iPhone 4 support HSDPA 7.2. AT&T introduced 3G in July 2004(SONY VAIO VGN-FZ150E Battery), but as late as 2007 Steve Jobs stated that it was still not widespread enough in the US, and the chipsets not energy efficient enough, to be included in the iPhone. Support for 802.1X, an authentication system commonly used by university and corporate Wi-Fi networks, was added in the 2.0 version update(SONY VAIO VGN-FZ260E Battery).

By default, the iPhone will ask to join newly discovered Wi-Fi networks and prompt for the password when required. Alternatively, it can join closed Wi-Fi networks manually. The iPhone will automatically choose the strongest network(SONY VAIO VGN-FZ140E Battery), connecting to Wi-Fi instead of EDGE when it is available. Similarly, the iPhone 3G, 3GS and 4 prefer 3G to 2G, and Wi-Fi to either. Wi-Fi, Bluetooth, and 3G (on the iPhone 3G, 3GS, and 4) can all be deactivated individually(SONY VAIO VGN-FZ11l Battery). Airplane mode disables all wireless connections at once, overriding other preferences. However, once in Airplane mode, one can explicitly enable Wi-Fi and/or Bluetooth modes to join and continue to operate over one or both of those networks while the cellular network transceivers remain off(SONY VAIO VGN-FZ11z Battery).

The iPhone 3GS has a maximum download rate of 7.2 Mbit/s. Furthermore, files downloaded over cellular networks must be smaller than 20 MB. Larger files, often email attachments or podcasts, must be downloaded over Wi-Fi (SONY VAIO VGN-FZ11m Battery) (which has no file size limits). If Wi-Fi is unavailable, one workaround is to open the files directly in Safari.

Safari is the iPhone's native web browser, and it displays pages similar to its Mac and Windows counterparts(SONY VAIO VGN-FZ18m Battery). Web pages may be viewed in portrait or landscape mode and supports automatic zooming by pinching together or spreading apart fingertips on the screen, or by double-tapping text or images. The iPhone supports neither Flash nor Java. Consequently(SONY VAIO VGN-FZ21m Battery), the UK's Advertising Standards Authority adjudicated that an advertisement claiming the iPhone could access "all parts of the internet" should be withdrawn in its current form, on grounds of false advertising(SONY VAIO VGN-FZ410 Battery). In a rare public letter in April 2010, Apple CEO Steve Jobs outlined the reasoning behind the absence of Flash on the iPhone (and iPad). The iPhone supports SVG, CSS, HTML Canvas, and Bonjour(SONY VAIO VGN-FZ21 Battery).

The maps application can access Google Maps in map, satellite, or hybrid form. It can also generate directions between two locations, while providing optional real-time traffic information(SONY VAIO VGN-FZ160 Battery). During the iPhone's announcement, Jobs demonstrated this feature by searching for nearby Starbucks locations and then placing a prank call to one with a single tap. Support for walking directions, public transit, and street view was added in the version 2.2 software update(SONY VAIO VGN-FZ210CE Battery), but no voice-guided navigation. The iPhone 3GS and iPhone 4 can orient the map with its digital compass. Apple also developed a separate application to view YouTube videos on the iPhone, which streams videos after encoding them using the H.264 codec. Simple weather and stock quotes applications also tap in to the Internet(SONY VAIO VGN-FZ38M Battery).

iPhone users can and do access the Internet frequently, and in a variety of places. According to Google, in 2008 the iPhone generated 50 times more search requests than any other mobile handset(SONY VAIO VGN-FZ31z Battery). According to Deutsche Telekom CEO René Obermann, "The average Internet usage for an iPhone customer is more than 100 megabytes. This is 30 times the use for our average contract-based consumer customers(Sony Vaio VGN-FZ31S battery)." Nielsen found that 98% of iPhone users use data services, and 88% use the internet. In China, the iPhone 3G and iPhone 3GS were built and distributed without Wi-fi(SONY VAIO VGN-FZ31E Battery).

With the introduction of the Verizon iPhone in January 2011, the issue of using internet while on the phone has been brought to the public's attention. Under the two US carriers, internet and phone could be used simultaneously on ATT networks, whereas the Verizon networks only support for the use of each separately(SONY VAIO VGN-FZ31J Battery).

Text input

The virtual keyboard on the original iPhone's touchscreen.

For text input, the iPhone implements a virtual keyboard on the touchscreen. It has automatic spell checking and correction, predictive word capabilities, and a dynamic dictionary that learns new words(SONY VAIO VGN-FZ31M Battery). The keyboard can predict what word the user is typing and complete it, and correct for the accidental pressing of keys near the presumed desired key. The keys are somewhat larger and spaced farther apart when in landscape mode(SONY VAIO VGN-FZ31B Battery), which is supported by only a limited number of applications. Touching a section of text for a brief time brings up a magnifying glass, allowing users to place the cursor in the middle of existing text(HP PAVILION DV6000 battery). The virtual keyboard can accommodate 21 languages, including character recognition for Chinese. The 3.0 update brought support for cut, copy, or pasting text, as well as landscape keyboards in more applications(SONY VGP-BPS13 Battery).

E-mail and text messages

The iPhone also features an e-mail program that supports HTML e-mail, which enables the user to embed photos in an e-mail message. PDF, Word, Excel, and Powerpoint attachments to mail messages can be viewed on the phone(SONY VGP-BPS13B/B Battery). Apple's MobileMe platform offers push email, which emulates the functionality of the popular BlackBerry email solution, for an annual subscription. Yahoo! offers a free push-email service for the iPhone(SONY VGP-BPS13/B Battery). IMAP (although not Push-IMAP) and POP3 mail standards are also supported, including Microsoft Exchange and Kerio Connect. In the first versions of the iPhone firmware, this was accomplished by opening up IMAP on the Exchange server(Sony VAIO VGN-FZ15T Battery). Apple has also licensed Microsoft ActiveSync and now supports the platform (including push email) with the release of iPhone 2.0 firmware. The iPhone will sync e-mail account settings over from Apple's own Mail application, Microsoft Outlook, and Microsoft Entourage(Sony VAIO VGN-FZ15G Battery), or it can be manually configured on the device itself. With the correct settings, the e-mail program can access almost any IMAP or POP3 account.

Text messages are presented chronologically in a mailbox format similar to Mail, which places all text from recipients together with replies(SONY VGP-BPS13A/S Battery). Text messages are displayed in speech bubbles (similar to iChat) under each recipient's name. The iPhone has built-in support for e-mail message forwarding, drafts, and direct internal camera-to-e-mail picture sending(SONY VGP-BPS13AS Battery). Support for multi-recipient SMS was added in the 1.1.3 software update. Support for MMS was added in the 3.0 update, but not for the original iPhone and not in the U.S. until September 25, 2009(SONY VGP-BPS13S Battery).

Third-party applications

See also: iPhone SDK and App Store

At WWDC 2007 on June 11, 2007 Apple announced that the iPhone would support third-party "web applications" written in Ajax that share the look and feel of the iPhone interface(SONY VGP-BPS13B/S Battery). On October 17, 2007, Steve Jobs, in an open letter posted to Apple's "Hot News" weblog, announced that a software development kit (SDK) would be made available to third-party developers in February 2008(SONY VAIO PCG-5G2L battery). The iPhone SDK was officially announced and released on March 6, 2008, at the Apple Town Hall facility. It is a free download, with an Apple registration, that allows developers to develop native applications for the iPhone and iPod Touch, then test them in an "iPhone simulator"(SONY VAIO PCG-5G3L battery). However, loading an application onto a real device is only possible after paying a Apple Developer Connection membership fee. Developers are free to set any price for their applications to be distributed through the App Store, of which they will receive a 70% share(SONY VAIO PCG-5J1L battery). Developers can also opt to release the application for free and will not pay any costs to release or distribute the application beyond the membership fee. The App Store was launched with the release of iOS 2.0, on July 11, 2008(SONY VAIO PCG-5K2L battery). The update was free for iPhone users; owners of older iPod Touches were required to pay US$10 for it.

Once a developer has submitted an application to the App Store, Apple holds firm control over its distribution(SONY VAIO PCG-5L1L battery). Apple can halt the distribution of applications it deems inappropriate, for example, I Am Rich, a US$1000 program that simply demonstrated the wealth of its user. Apple has been criticized for banning third party applications that enable a functionality that Apple does not want the iPhone to have(SONY VAIO PCG-5J2L battery): In 2008, Apple rejected Podcaster, which allowed iPhone users to download podcasts directly to the iPhone claiming it duplicated the functionality of iTunes. Apple has since released a software update that grants this capability(SONY VAIO PCG-6S2L battery).

NetShare, another rejected app, would have enabled users to tether their iPhone to a laptop or desktop, using its cellular network to load data for the computer. Many carriers of the iPhone later globally allowed tethering before Apple officially supported it with the upgrade to the iOS 3.0(SONY VAIO PCG-6S3L battery), with AT&T Mobility being a relative latecomer in the United States. In most cases, the carrier charges extra for tethering an iPhone(SONY VAIO PCG-6V1L battery).

Before the SDK was released, third-parties were permitted to design "Web Apps" that would run through Safari. Unsigned native applications are also available for "jailbroken" phones(SONY VAIO PCG-6W1L battery). The ability to install native applications onto the iPhone outside of the App Store is not supported by Apple, the stated reason being that such native applications could be broken by any software update, but Apple has stated it will not design software updates specifically to break native applications other than those that perform SIM unlocking(SONY VAIO PCG-7111L battery).

Legal action

In December 2010, Reuters reported that some iPhone and iPad users were suing Apple Inc because some applications were passing user information to third party advertisers without permission(SONY VAIO PCG-6W3L battery). Some makers of the applications such as Textplus4, Paper Toss, Weather Channel, Dictionary.com, Talking Tom Cat and Pumpkin Maker have also been named as co-defendants in the lawsuit(SONY VAIO PCG-7113L battery).

Accessibility

The iPhone can enlarge text to make it more accessible for vision-impaired users, and can accommodate hearing-impaired users with closed captioning and external TTY devices. The iPhone 3GS also features white on black mode(SONY VAIO PCG-7133L battery), VoiceOver (a screen reader), and zooming for impaired vision, and mono audio for limited hearing in one ear. Apple regularly publishes Voluntary Product Accessibility Templates which explicitly state compliance with the US regulation "Section 508"(SONY VAIO PCG-7Z1L battery).

Intellectual property

Apple has filed more than 200 patent applications related to the technology behind the iPhone(SONY Vaio VGN-FW31J Battery).

LG Electronics claimed the iPhone's design was copied from the LG Prada. Woo-Young Kwak, head of LG Mobile Handset R&D Center, said at a press conference, "We consider that Apple copied Prada phone after the design was unveiled when it was presented in the iF Design Award and won the prize in September 2006(SONY VAIO PCG-7Z2L battery)."

On September 3, 1993, Infogear filed for the U.S. trademark "I PHONE" and on March 20, 1996 applied for the trademark "IPhone". "I Phone" was registered in March 1998, and "IPhone" was registered in 1999(SONY VAIO PCG-8Y1L battery). Since then, the I PHONE mark had been abandoned. Infogear's trademarks cover "communications terminals comprising computer hardware and software providing integrated telephone, data communications and personal computer functions" (1993 filing) (SONY VAIO PCG-8Y2L battery), and "computer hardware and software for providing integrated telephone communication with computerized global information networks" (1996 filing). Infogear released a telephone with an integrated web browser under the name iPhone in 1998(SONY VAIO PCG-8Z2L battery). In 2000, Infogear won an infringement claim against the owners of the iphones.com domain name. In June 2000, Cisco Systems acquired Infogear, including the iPhone trademark. On December 18, 2006 they released a range of re-branded Voice over IP (VoIP) sets under the name iPhone(SONY VAIO PCG-8Z1L battery).

In October 2002, Apple applied for the "iPhone" trademark in the United Kingdom, Australia, Singapore, and the European Union. A Canadian application followed in October 2004 and a New Zealand application in September 2006. As of October 2006 only the Singapore and Australian applications had been granted(SONY VAIO PCG-7112L battery). In September 2006, a company called Ocean Telecom Services applied for an "iPhone" trademark in the United States, United Kingdom and Hong Kong, following a filing in Trinidad and Tobago(SONY VAIO PCG-6W2L battery). As the Ocean Telecom trademark applications use exactly the same wording as Apple's New Zealand application, it is assumed that Ocean Telecom is applying on behalf of Apple. The Canadian application was opposed in August 2005 by a Canadian company called Comwave who themselves applied for the trademark three months later. Comwave has been selling VoIP devices called iPhone since 2004(SONY VAIO PCG-5K1L battery).

Shortly after Steve Jobs' January 9, 2007 announcement that Apple would be selling a product called iPhone in June 2007, Cisco issued a statement that it had been negotiating trademark licensing with Apple and expected Apple to agree to the final documents that had been submitted the night before(SONY VGP-BPS21A/B Battery). On January 10, 2007 Cisco announced it had filed a lawsuit against Apple over the infringement of the trademark iPhone, seeking an injunction in federal court to prohibit Apple from using the name(SONY VGP-BPS21B Battery). More recently, Cisco claimed that the trademark lawsuit was a "minor skirmish" that was not about money, but about interoperability. On February 2, 2007, Apple and Cisco announced that they had agreed to temporarily suspend litigation while they held settlement talks(SONY VGP-BPS21 Battery), and subsequently announced on February 20, 2007 that they had reached an agreement. Both companies will be allowed to use the "iPhone" name in exchange for "exploring interoperability" between their security, consumer, and business communications products(SONY VGP-BPS21/S Battery).

The iPhone has also inspired several leading high-tech clones, driving both Apple's popularity and consumer willingness to upgrade iPhones quickly(SONY VGP-BPS13A/Q Battery).

On October 22, 2009 Nokia filed a lawsuit against Apple for infringement of its GSM, UMTS and WLAN patents. Nokia alleges that Apple has been violating ten of Nokia's patents since the iPhone's initial release(SONY VGN NR11Z/T battery).

Restrictions

Unlocked iPhone firmware version 3.0. The serial number and Wi-Fi address have been removed from the image(SONY VGN NR11Z/S battery).

Apple tightly controls certain aspects of the iPhone. The hacker community has found many workarounds, most of which are disallowed by Apple and threaten to void the device's warranty. "Jailbreaking" allows users to install apps not available on the App Store or modify basic functionality. SIM unlocking allows the iPhone to be used on a different carrier's network(SONY VGN NR11M/S battery).

Activation

The iPhone normally prevents access to its media player and web features unless it has also been activated as a phone with an authorized carrier. On July 3, 2007, Jon Lech Johansen reported on his blog that he had successfully bypassed this requirement and unlocked the iPhone's other features with a combination of custom software and modification of the iTunes binary(SONY VGN NR11S/S battery). He published the software and offsets for others to use.

Unlike the original, the iPhone 3G must be activated in the store in most countries. This makes the iPhone 3G more difficult, but not impossible, to hack. The need for in-store activation(SONY VGP-BPS13B/Q Battery), as well as the huge number of first-generation iPhone and iPod Touch users upgrading to iPhone OS 2.0, caused a worldwide overload of Apple's servers on July 11, 2008, the day on which both the iPhone 3G and iPhone OS 2.0 updates as well as MobileMe were released(SONY VGP-BPS13Q Battery). After the update, devices were required to connect to Apple's servers to authenticate the update, causing many devices to be temporarily unusable. Apple avoided this by releasing the 3.0 software two days before the iPhone 3GS(SONY Vaio VGN-FW21M Battery).

Users on the O2 network in the United Kingdom, however, can buy the phone online and activate it via iTunes as with the previous model. Even where not required, vendors usually offer activation for the buyer's convenience(SONY Vaio VGN-FW21L Battery). In the U.S., Apple has begun to offer free shipping on both the iPhone 3G and the iPhone 3GS (when available), reversing the in-store activation requirement. Best Buy and Wal-Mart will also sell the iPhone(SONY Vaio VGN-FW21J Battery).

Unlicensed third-party software and jailbreaking

See also: Jailbreaking for iOS and iPhone Dev Team

The iPhone's operating system is designed to only run software that has an Apple-approved cryptographic signature. This restriction can be overcome by "jailbreaking" the phone(SONY Vaio VGN-FW21E Battery), which involves replacing the iPhone's firmware with a slightly modified version that does not enforce the signature check. Doing so may be a circumvention of Apple's technical protection measures(SONY Vaio VGN-FW11S Battery). Apple, in a statement to the United States Copyright Office in response to EFF lobbying for a DMCA exception for this kind of hacking, claimed that jailbreaking the iPhone would be copyright infringement due to the necessary modification of system software. Jailbroken iPhones may be susceptible to computer viruses, but few such incidents have been reported(SONY Vaio VGN-FW11M Battery).

SIM unlocking

United States

iPhone 3G shown with the SIM tray partially ejected.

Most iPhones were and still are sold with a SIM lock, which restricts the use of the phone to one particular carrier, a common practice with subsidized GSM phones. Unlike most GSM phones however(SONY Vaio VGN-FW11 Battery), the phone cannot be officially unlocked by entering a code. The locked/unlocked state is maintained on Apple's servers per IMEI and is set when the iPhone is activated(SONY VAIO VGN-FZ21J Battery).

While the iPhone was initially sold in the US only on the AT&T network with a SIM lock in place, various hackers have found methods to "unlock" the phone from a specific network(SONY VAIO VGN-FZ21Z Battery). Although AT&T and Verizon are the only authorized iPhone carriers in the United States, unlocked iPhones can be used with other carriers after unlocking. More than a quarter of the original iPhones sold in the United States were not registered with AT&T(SONY VAIO VGN-FZ21E Battery). Apple speculates that they were likely shipped overseas and unlocked, a lucrative market before the iPhone 3G's worldwide release. iPhones are unlocked by users who wish to use networks other than AT&T's(SONY Vaio VGN-FW31M Battery).

AT&T has stated that the "iPhone cannot be unlocked, even if you are out of contract".On March 26, 2009 AT&T in the United States began selling the iPhone without a contract, though still SIM-locked to their network. The up-front purchase price of such iPhone units is often twice as expensive as those bundled with contracts(SONY Vaio VGN-FW465J Battery). Outside of the United States, policies differ, especially in US territories and insular areas like Guam, where GTA TeleGuam is the exclusive carrier for the iPhone, since neither AT&T nor Verizon have a presence in the area(SONY Vaio VGN-FW139E/H Battery).

United Kingdom

Operators O2, Orange, 3, Vodafone, T-Mobile, as well as MVNO Tesco Mobile sell the device in the UK under subsidised contracts, or for use on pay as you go. They are locked to network initially, though are usually able to be unlocked either after a certain period of contract length has passed, or for a small fee(SONY Vaio VGN-FW139E Battery). The iPhone 4 in the UK is also currently sold unlocked without a contract for full retail price for use on any network the user chooses, but only when bought directly from Apple (either online or in their physical shops) (SONY Vaio VGN-FW31E Battery).

Australia

Five major carriers in Australia, (Three, Optus, Telstra, Virgin Mobile, and Vodafone), offer legitimate unlocking, now at no cost for all iPhone devices, both current and prior models. The iPhone 3GS and the iPhone 4 can also be bought unlocked from a Apple Retail Store, or the Apple Online Store(SONY Vaio VGN-FW17W Battery).

Denmark

In Denmark it is unlocked after 6 months of contract have passed, or earlier if you pay DKK 500 (approx. €70) for unlocking(SONY Vaio VGN-FW32J Battery).

France

In France, the iPhone is locked on the Wireless purchased from (Orange, SFR, Bouygues Telecom or Virgin Mobile), but can also be bought unlocked in Apple stores. Phones that were initially locked to a carrier are unlocked for free after a certain portion of the bundled contract's fixed term is up, or for a fee at any time before that(Dell N3010 Battery).

Germany

In Germany, the iPhone 3GS or iPhone 4 may be purchased without a SIM-lock directly from Apple.The iPhone may also be purchased through three of the four major German mobile network carriers(Dell INSPIRON 1464 battery).

Other countries

The iPhone is also available without any SIM lock for full retail price in some countries. Vendors in Thailand, Austria, Belgium, Canada, South Africa, Ecuador, Singapore, Greece, Cyprus, Romania, Taiwan, China, Hong Kong, Italy, Israel, New Zealand, Vietnam, Finland and Russia sell iPhones not locked to any carrier(Dell INSPIRON E1505 battery).