Micron Document
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<title>Pulse-code modulation</title>
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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Pulse-code modulation</span></span>
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</style><div role="note" class="hatnote navigation-not-searchable">"PCM" redirects here. For other uses, see <a href="PCM_(disambiguation)" class="mw-disambig" title="PCM (disambiguation)">PCM (disambiguation)</a>.</div>
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</style><table class="infobox"><tbody><tr><th colspan="2" class="infobox-above" style="padding-bottom: 0.15em;">Pulse-code modulation</th></tr><tr><th scope="row" class="infobox-label" style="line-height: 1.2; padding-right: 0.65em;"><a href="Filename_extension" title="Filename extension">Filename extension</a></th><td class="infobox-data" style="line-height: 1.35;"><style data-mw-deduplicate="TemplateStyles:r886049734">
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.L16, .WAV, .AIFF, .AU, .PCM<sup id="cite_ref-rfc2586_1-0" class="reference"><a href="#cite_note-rfc2586-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup></div></td></tr><tr><th scope="row" class="infobox-label" style="line-height: 1.2; padding-right: 0.65em;"><a href="Media_type" title="Media type">Internet media&nbsp;type</a></th><td class="infobox-data" style="line-height: 1.35;"><div class="monospaced">
audio/L16, audio/L8,<sup id="cite_ref-rfc4856_2-0" class="reference"><a href="#cite_note-rfc4856-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> audio/L20, audio/L24<sup id="cite_ref-rfc3190_3-0" class="reference"><a href="#cite_note-rfc3190-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup></div></td></tr><tr><th scope="row" class="infobox-label" style="line-height: 1.2; padding-right: 0.65em;"><a href="Resource_fork#Types" title="Resource fork">Type code</a></th><td class="infobox-data" style="line-height: 1.35;">"AIFF" for L16,<sup id="cite_ref-rfc2586_1-1" class="reference"><a href="#cite_note-rfc2586-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> none<sup id="cite_ref-rfc3190_3-1" class="reference"><a href="#cite_note-rfc3190-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label" style="line-height: 1.2; padding-right: 0.65em;"><a href="File_format#Magic_number" title="File format">Magic number</a></th><td class="infobox-data" style="line-height: 1.35;">Varies</td></tr><tr><th scope="row" class="infobox-label" style="line-height: 1.2; padding-right: 0.65em;">Type of format</th><td class="infobox-data" style="line-height: 1.35;">Uncompressed <a href="Audio_file_format" title="Audio file format">audio</a></td></tr><tr><th scope="row" class="infobox-label" style="line-height: 1.2; padding-right: 0.65em;">Contained&nbsp;by</th><td class="infobox-data" style="line-height: 1.35;"><a href="Red_Book_(audio_CD_standard)" class="mw-redirect" title="Red Book (audio CD standard)">Audio CD</a>, <a href="AES3" title="AES3">AES3</a>, <a href="WAV" title="WAV">WAV</a>, <a href="Audio_Interchange_File_Format" title="Audio Interchange File Format">AIFF</a>, <a href="Au_file_format" title="Au file format">AU</a>, <a href="M2TS" class="mw-redirect" title="M2TS">M2TS</a>, <a href="VOB" title="VOB">VOB</a>, and many others</td></tr><tr><th scope="row" class="infobox-label" style="line-height: 1.2; padding-right: 0.65em;"><span class="nowrap"><a href="Open_file_format" title="Open file format">Open format</a>?</span></th><td class="infobox-data" style="line-height: 1.35;">Yes</td></tr><tr><th scope="row" class="infobox-label" style="line-height: 1.2; padding-right: 0.65em;"><span class="nowrap"><a href="Open_standard#Comparison_of_definitions" title="Open standard">Free format</a>?</span></th><td class="infobox-data" style="line-height: 1.35;">Yes<sup id="cite_ref-LOC_LPCM_5-0" class="reference"><a href="#cite_note-LOC_LPCM-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup></td></tr></tbody></table>
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</style><table class="sidebar nomobile nowraplinks skin-invert"><tbody><tr><th class="sidebar-title" style="background-color: #bdb"><a href="Passband" title="Passband">Passband</a> <a href="Signal_modulation" title="Signal modulation">modulation</a></th></tr><tr><td class="sidebar-image"><span typeof="mw:File"></span></td></tr><tr><th class="sidebar-heading" style="background-color: #cfc;">
<a href="Signal_modulation#Analog_modulation_methods" title="Signal modulation">Analog modulation</a></th></tr><tr><td class="sidebar-content hlist" style="color: black;">
<ul><li><a href="Amplitude_modulation" title="Amplitude modulation">AM</a>
<ul><li><a href="Space_modulation" title="Space modulation">SM</a></li>
<li><a href="Single-sideband_modulation" title="Single-sideband modulation">SSB</a></li></ul></li>
<li><a href="Angle_modulation" title="Angle modulation">Angle modulation</a>
<ul><li><a href="Frequency_modulation" title="Frequency modulation">FM</a></li>
<li><a href="Phase_modulation" title="Phase modulation">PM</a></li></ul></li>
<li><a href="Quadrature_amplitude_modulation" title="Quadrature amplitude modulation">QAM</a></li></ul></td>
</tr><tr><th class="sidebar-heading" style="background-color: #cfc;">
<a href="Signal_modulation#Digital_modulation_methods" title="Signal modulation">Digital modulation</a></th></tr><tr><td class="sidebar-content hlist" style="color: black;">
<ul><li><a href="Amplitude-shift_keying" title="Amplitude-shift keying">ASK</a></li>
<li><a href="Amplitude_and_phase-shift_keying" title="Amplitude and phase-shift keying">APSK</a></li>
<li><a href="Continuous_phase_modulation" title="Continuous phase modulation">CPM</a></li>
<li><a href="Frequency-shift_keying" title="Frequency-shift keying">FSK</a></li>
<li><a href="Multiple_frequency-shift_keying" title="Multiple frequency-shift keying">MFSK</a></li>
<li><a href="Minimum-shift_keying" title="Minimum-shift keying">MSK</a></li>
<li><a href="On%E2%80%93off_keying" title="On–off keying">OOK</a></li>
<li><a href="Pulse-position_modulation" title="Pulse-position modulation">PPM</a></li>
<li><a href="Phase-shift_keying" title="Phase-shift keying">PSK</a></li>
<li><a href="Quadrature_amplitude_modulation" title="Quadrature amplitude modulation">QAM</a></li>
<li><a href="Single-carrier_FDMA" title="Single-carrier FDMA">SC-FDE</a></li>
<li><a href="Trellis_coded_modulation" title="Trellis coded modulation">TCM</a></li>
<li><a href="TC-PAM" title="TC-PAM">TC-PAM</a></li>
<li><a href="Wavelet_modulation" title="Wavelet modulation">WDM</a></li></ul></td>
</tr><tr><th class="sidebar-heading" style="background-color: #cfc;">
<a href="Hierarchical_modulation" title="Hierarchical modulation">Hierarchical modulation</a></th></tr><tr><td class="sidebar-content hlist" style="color: black;">
<ul><li><a href="Quadrature_amplitude_modulation" title="Quadrature amplitude modulation">QAM</a></li>
<li><a href="Wavelet_modulation" title="Wavelet modulation">WDM</a></li></ul></td>
</tr><tr><th class="sidebar-heading" style="background-color: #cfc;">
<a href="Spread_spectrum" title="Spread spectrum">Spread spectrum</a></th></tr><tr><td class="sidebar-content hlist" style="color: black;">
<ul><li><a href="Chirp_spread_spectrum" title="Chirp spread spectrum">CSS</a></li>
<li><a href="Direct-sequence_spread_spectrum" title="Direct-sequence spread spectrum">DSSS</a></li>
<li><a href="Frequency-hopping_spread_spectrum" title="Frequency-hopping spread spectrum">FHSS</a></li>
<li><a href="Time-hopping" title="Time-hopping">THSS</a></li></ul></td>
</tr><tr><th class="sidebar-heading" style="background-color: #cfc;">
See also</th></tr><tr><td class="sidebar-content hlist" style="color: black;">
<ul><li>Capacity-approaching codes</li>
<li><a href="Demodulation" title="Demodulation">Demodulation</a></li>
<li><a href="Line_code" title="Line code">Line coding</a></li>
<li><a href="Modem" title="Modem">Modem</a></li>
<li><a href="Angle_modulation" title="Angle modulation">AnM</a></li>
<li><a href="Polar_modulation" title="Polar modulation">PoM</a></li>
<li><a href="Pulse-amplitude_modulation" title="Pulse-amplitude modulation">PAM</a></li>

<li><a href="Pulse-density_modulation" title="Pulse-density modulation">PDM</a></li>
<li><a href="Pulse-width_modulation" title="Pulse-width modulation">PWM</a></li>
<li><a href="Delta-sigma_modulation" title="Delta-sigma modulation">ΔΣM</a></li>
<li><a href="Orthogonal_frequency-division_multiplexing" title="Orthogonal frequency-division multiplexing">OFDM</a></li>
<li><a href="Frequency-division_multiplexing" title="Frequency-division multiplexing">FDM</a></li>
<li><a href="Multiplexing" title="Multiplexing">Multiplexing</a></li></ul></td>
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<p><b>Pulse-code modulation</b> (<b>PCM</b>) is a method used to <a href="Digital_signal_(signal_processing)" title="Digital signal (signal processing)">digitally</a> represent <a href="Analog_signal" title="Analog signal">analog signals</a>. It is the standard form of <a href="Digital_audio" title="Digital audio">digital audio</a> in computers, <a href="Compact_disc" title="Compact disc">compact discs</a>, <a href="Digital_telephony" class="mw-redirect" title="Digital telephony">digital telephony</a> and other digital audio applications. In a PCM <a href="Stream_(computing)" title="Stream (computing)">stream</a>, the <a href="Amplitude" title="Amplitude">amplitude</a> of the analog signal is <a href="Sampling_(signal_processing)" title="Sampling (signal processing)">sampled</a> at uniform intervals, and each sample is <a href="Quantization_(signal_processing)" title="Quantization (signal processing)">quantized</a> to the nearest value within a range of digital steps. <a href="Alec_Reeves" title="Alec Reeves">Alec Reeves</a>, <a href="Claude_Shannon" title="Claude Shannon">Claude Shannon</a>, <a href="Barney_Oliver" class="mw-redirect" title="Barney Oliver">Barney Oliver</a> and <a href="John_R._Pierce" title="John R. Pierce">John R. Pierce</a> are credited with its invention.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup>
</p><p><b>Linear pulse-code modulation</b> (<b>LPCM</b>) is a specific type of PCM in which the quantization levels are linearly uniform.<sup id="cite_ref-LOC_LPCM_5-1" class="reference"><a href="#cite_note-LOC_LPCM-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> This is in contrast to PCM encodings in which quantization levels vary as a function of amplitude (as with the <a href="A-law_algorithm" title="A-law algorithm">A-law algorithm</a> or the <a href="%CE%9C-law_algorithm" title="Μ-law algorithm">μ-law algorithm</a>). Though <i>PCM</i> is a more general term, it is often used to describe data encoded as LPCM.
</p><p>A PCM stream has two basic properties that determine the stream's fidelity to the original analog signal: the <a href="Sampling_rate" class="mw-redirect" title="Sampling rate">sampling rate</a>, which is the number of times per second that samples are taken; and the <a href="Audio_bit_depth" title="Audio bit depth">bit depth</a>, which determines the number of possible digital values that can be used to represent each sample.
</p>
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<div class="mw-heading mw-heading2"><h2 id="History">History</h2></div>
<p>Early electrical communications started to <a href="Sampling_(signal_processing)" title="Sampling (signal processing)">sample</a> signals in order to <a href="Multiplexing" title="Multiplexing">multiplex</a> samples from multiple <a href="Telegraphy" title="Telegraphy">telegraphy</a> sources and to convey them over a single telegraph cable. The American inventor <a href="Moses_G._Farmer" title="Moses G. Farmer">Moses G. Farmer</a> conceived telegraph <a href="Time-division_multiplexing" title="Time-division multiplexing">time-division multiplexing</a> (TDM) as early as 1853. Electrical engineer W. M. Miner, in 1903, used an electro-mechanical <a href="Commutator_(electric)" title="Commutator (electric)">commutator</a> for time-division multiplexing multiple telegraph signals; he also applied this technology to <a href="Telephony" title="Telephony">telephony</a>. He obtained intelligible speech from channels sampled at a rate above 3500–4300&nbsp;Hz; lower rates proved unsatisfactory.
</p><p>In 1920, the <a href="Bartlane_cable_picture_transmission_system" class="mw-redirect" title="Bartlane cable picture transmission system">Bartlane cable picture transmission system</a> used telegraph signaling of characters punched in paper tape to send samples of images <a href="Quantization_(image_processing)" title="Quantization (image processing)">quantized</a> to 5 levels.<sup id="cite_ref-digicamhistory_9-0" class="reference"><a href="#cite_note-digicamhistory-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> In 1926, Paul M. Rainey of <a href="Western_Electric" title="Western Electric">Western Electric</a> patented a <a href="Facsimile_machine" class="mw-redirect" title="Facsimile machine">facsimile machine</a> that transmitted its signal using 5-bit PCM, encoded by an opto-mechanical <a href="Analog-to-digital_converter" title="Analog-to-digital converter">analog-to-digital converter</a>.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> The machine did not go into production.<sup id="cite_ref-Vardalas_11-0" class="reference"><a href="#cite_note-Vardalas-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup>
</p><p>British engineer <a href="Alec_Reeves" title="Alec Reeves">Alec Reeves</a>, unaware of previous work, conceived the use of PCM for voice communication in 1937 while working for <a href="International_Telephone_and_Telegraph" class="mw-redirect" title="International Telephone and Telegraph">International Telephone and Telegraph</a> in France. He described the theory and its advantages, but no practical application resulted. Reeves filed for a French patent in 1938, and his US patent was granted in 1943.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> By this time Reeves had started working at the <a href="Telecommunications_Research_Establishment" title="Telecommunications Research Establishment">Telecommunications Research Establishment</a>.<sup id="cite_ref-Vardalas_11-1" class="reference"><a href="#cite_note-Vardalas-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup>
</p><p>The first transmission of <a href="Speech" title="Speech">speech</a> by digital techniques, the <a href="SIGSALY" title="SIGSALY">SIGSALY</a> encryption equipment, conveyed high-level <a href="Allies_of_World_War_II" title="Allies of World War II">Allied communications</a> during <a href="World_War_II" title="World War II">World War II</a>. In 1943 the <a href="Bell_Labs" title="Bell Labs">Bell Labs</a> researchers who designed the SIGSALY system became aware of the use of PCM binary coding as already proposed by Reeves. In 1949, for the Canadian Navy's <a href="DATAR" title="DATAR">DATAR</a> system, <a href="Ferranti_Canada" class="mw-redirect" title="Ferranti Canada">Ferranti Canada</a> built a working PCM radio system that was able to transmit digitized radar data over long distances.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup>
</p><p>PCM in the late 1940s and early 1950s used a <a href="Cathode_ray_tube" class="mw-redirect" title="Cathode ray tube">cathode-ray</a> coding tube with a <a href="Plate_electrode" title="Plate electrode">plate electrode</a> having encoding perforations.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> As in an <a href="Oscilloscope" title="Oscilloscope">oscilloscope</a>, the beam was swept horizontally at the sample rate while the vertical deflection was controlled by the input analog signal, causing the beam to pass through higher or lower portions of the perforated plate. The plate collected or passed the beam, producing current variations in binary code, one bit at a time. Rather than natural binary, the grid of Goodall's later tube was perforated to produce a glitch-free <a href="Gray_code" title="Gray code">Gray code</a> and produced all bits simultaneously by using a fan beam instead of a scanning beam.<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup>
</p><p>In the United States, the <a href="National_Inventors_Hall_of_Fame" title="National Inventors Hall of Fame">National Inventors Hall of Fame</a> has honored <a href="Bernard_M._Oliver" title="Bernard M. Oliver">Bernard M. Oliver</a><sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup>
and <a href="Claude_Shannon" title="Claude Shannon">Claude Shannon</a><sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup>
as the inventors of PCM,<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup>
as described in "Communication System Employing Pulse Code Modulation", <span><a rel="nofollow" class="external text" href="https://patents.google.com/patent/US2801281">U.S. patent 2,801,281</a></span> filed in 1946 and 1952, granted in 1956. Another patent by the same title was filed by <a href="John_R._Pierce" title="John R. Pierce">John R. Pierce</a> in 1945, and issued in 1948: <span><a rel="nofollow" class="external text" href="https://patents.google.com/patent/US2437707">U.S. patent 2,437,707</a></span>. The three of them published "The Philosophy of PCM" in 1948.<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup>
</p><p>The <a href="T-carrier" title="T-carrier">T-carrier</a> system, introduced in 1961, uses two twisted-pair transmission lines to carry 24 PCM <a href="Telephone" title="Telephone">telephone</a> calls sampled at 8&nbsp;kHz and 8-bit resolution. This development improved capacity and call quality compared to the previous <a href="Frequency-division_multiplexing" title="Frequency-division multiplexing">frequency-division multiplexing</a> schemes.
</p><p>In 1973, <a href="Adaptive_differential_pulse-code_modulation" title="Adaptive differential pulse-code modulation">adaptive differential pulse-code modulation</a> (ADPCM) was developed, by P. Cummiskey, <a href="Nikil_Jayant" title="Nikil Jayant">Nikil Jayant</a> and <a href="James_L._Flanagan" title="James L. Flanagan">James L. Flanagan</a>.<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup>
</p>
<div class="mw-heading mw-heading3"><h3 id="Digital_audio_recordings">Digital audio recordings</h3></div>
<div role="note" class="hatnote navigation-not-searchable">Main articles: <a href="Digital_audio" title="Digital audio">Digital audio</a> and <a href="Digital_recording" title="Digital recording">Digital recording</a></div>
<p>In 1967, the first PCM recorder was developed by <a href="NHK" title="NHK">NHK</a>'s research facilities in Japan.<sup id="cite_ref-Fine_21-0" class="reference"><a href="#cite_note-Fine-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> The 30&nbsp;kHz 12-bit device used a <a href="Compander" class="mw-redirect" title="Compander">compander</a> (similar to <a href="Dbx_(noise_reduction)" title="Dbx (noise reduction)">DBX Noise Reduction</a>) to extend the dynamic range, and stored the signals on a <a href="Video_tape_recorder" title="Video tape recorder">video tape recorder</a>. In 1969, NHK expanded the system's capabilities to 2-channel <a href="Stereo" class="mw-redirect" title="Stereo">stereo</a> and 32&nbsp;kHz 13-bit resolution. In January 1971, using NHK's PCM recording system, engineers at <a href="Denon" title="Denon">Denon</a> recorded the first commercial digital recordings.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>note 1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Fine_21-1" class="reference"><a href="#cite_note-Fine-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup>
</p><p>In 1972, Denon unveiled the first 8-channel digital recorder, the DN-023R, which used a 4-head open reel broadcast video tape recorder to record in 47.25&nbsp;kHz, 13-bit PCM audio.<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>note 2<span class="cite-bracket">]</span></a></sup> In 1977, Denon developed the portable PCM recording system, the DN-034R. Like the DN-023R, it recorded 8 channels at 47.25&nbsp;kHz, but it used 14-bits "with <a href="Emphasis_(telecommunications)" title="Emphasis (telecommunications)">emphasis</a>, making it equivalent to 15.5 bits."<sup id="cite_ref-Fine_21-2" class="reference"><a href="#cite_note-Fine-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup>
</p><p>In 1979, the first digital pop album, <a href="Bop_till_You_Drop" class="mw-redirect" title="Bop till You Drop">Bop till You Drop</a>, was recorded. It was recorded in 50&nbsp;kHz, 16-bit linear PCM using a 3M digital tape recorder.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup>
</p><p>The <a href="Compact_disc" title="Compact disc">compact disc</a> (CD) brought PCM to consumer audio applications with its introduction in 1982. The CD uses a <a href="44%2C100_Hz" title="44,100 Hz">44,100 Hz</a> sampling frequency and 16-bit resolution and stores up to 80 minutes of stereo audio per disc.
</p>
<div class="mw-heading mw-heading3"><h3 id="Digital_telephony">Digital telephony</h3></div>
<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Digital_telephony" class="mw-redirect" title="Digital telephony">Digital telephony</a></div>
<p>The rapid development and wide adoption of PCM <a href="Digital_telephony" class="mw-redirect" title="Digital telephony">digital telephony</a> was enabled by <a href="Metal%E2%80%93oxide%E2%80%93semiconductor" class="mw-redirect" title="Metal–oxide–semiconductor">metal–oxide–semiconductor</a> (MOS) <a href="Switched_capacitor" title="Switched capacitor">switched capacitor</a> (SC) circuit technology, developed in the early 1970s.<sup id="cite_ref-Allstot_25-0" class="reference"><a href="#cite_note-Allstot-25"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> This led to the development of PCM codec-filter chips in the late 1970s.<sup id="cite_ref-Allstot_25-1" class="reference"><a href="#cite_note-Allstot-25"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Gibson26_26-0" class="reference"><a href="#cite_note-Gibson26-26"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> The <a href="Silicon-gate" class="mw-redirect" title="Silicon-gate">silicon-gate</a> <a href="CMOS" title="CMOS">CMOS</a> (complementary MOS) PCM codec-filter chip, developed by <a href="David_A._Hodges" title="David A. Hodges">David A. Hodges</a> and W.C. Black in 1980,<sup id="cite_ref-Allstot_25-2" class="reference"><a href="#cite_note-Allstot-25"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> has since been the industry standard for digital telephony.<sup id="cite_ref-Allstot_25-3" class="reference"><a href="#cite_note-Allstot-25"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Gibson26_26-1" class="reference"><a href="#cite_note-Gibson26-26"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> By the 1990s, <a href="Telecommunication_network" class="mw-redirect" title="Telecommunication network">telecommunication networks</a> such as the <a href="Public_switched_telephone_network" title="Public switched telephone network">public switched telephone network</a> (PSTN) had been largely <a href="Digitized" class="mw-redirect" title="Digitized">digitized</a> with <a href="Very-large-scale_integration" title="Very-large-scale integration">very-large-scale integration</a> (VLSI) CMOS PCM codec-filters, widely used in <a href="Electronic_switching_system" title="Electronic switching system">electronic switching systems</a> for <a href="Telephone_exchanges" class="mw-redirect" title="Telephone exchanges">telephone exchanges</a>, user-end <a href="Modems" class="mw-redirect" title="Modems">modems</a> and a wide range of <a href="Digital_transmission" class="mw-redirect" title="Digital transmission">digital transmission</a> applications such as the <a href="Integrated_services_digital_network" class="mw-redirect" title="Integrated services digital network">integrated services digital network</a> (ISDN), <a href="Cordless_telephones" class="mw-redirect" title="Cordless telephones">cordless telephones</a> and <a href="Cell_phones" class="mw-redirect" title="Cell phones">cell phones</a>.<sup id="cite_ref-Gibson26_26-2" class="reference"><a href="#cite_note-Gibson26-26"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup>
</p>
<div class="mw-heading mw-heading2"><h2 id="Implementations">Implementations</h2></div>
<p>PCM is the method of encoding typically used for uncompressed digital audio.<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>note 3<span class="cite-bracket">]</span></a></sup>
</p>
<ul><li>The <a href="4ESS_switch" class="mw-redirect" title="4ESS switch">4ESS switch</a> introduced time-division switching into the US telephone system in 1976, based on medium scale integrated circuit technology.<sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup></li>
<li>LPCM is used for the lossless encoding of audio data in the compact disc <a href="Red_Book_(audio_CD_standard)" class="mw-redirect" title="Red Book (audio CD standard)">Red Book standard</a> (informally also known as <i>Audio CD</i>), introduced in 1982.</li>
<li><a href="AES3" title="AES3">AES3</a> (specified in 1985, upon which <a href="S/PDIF" title="S/PDIF">S/PDIF</a> is based) is a particular format using LPCM.</li>
<li><a href="LaserDisc" title="LaserDisc">LaserDiscs</a> with digital sound have an LPCM track on the digital channel.</li>
<li>On PCs, PCM and LPCM often refer to the format used in <a href="WAV" title="WAV">WAV</a> (defined in 1991) and <a href="Audio_Interchange_File_Format" title="Audio Interchange File Format">AIFF</a> audio container formats (defined in 1988). LPCM data may also be stored in other formats such as <a href="Au_file_format" title="Au file format">AU</a>, <a href="Raw_audio_format" title="Raw audio format">raw audio format</a> (header-less file) and various multimedia <a href="Digital_container_format" class="mw-redirect" title="Digital container format">container formats</a>.</li>
<li>LPCM has been defined as a part of the <a href="DVD" title="DVD">DVD</a> (since 1995) and <a href="Blu-ray" title="Blu-ray">Blu-ray</a> (since 2006) standards.<sup id="cite_ref-bd_29-0" class="reference"><a href="#cite_note-bd-29"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-31" class="reference"><a href="#cite_note-31"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> It is also defined as a part of various digital video and audio storage formats (e.g. <a href="DV_(video_format)" title="DV (video format)">DV</a> since 1995,<sup id="cite_ref-32" class="reference"><a href="#cite_note-32"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> <a href="AVCHD" title="AVCHD">AVCHD</a> since 2006<sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup>).</li>
<li>LPCM is used by <a href="HDMI" title="HDMI">HDMI</a> (defined in 2002), a single-cable digital audio/video connector interface for transmitting uncompressed digital data.</li>
<li><a href="RF64" title="RF64">RF64</a> container format (defined in 2007) uses LPCM and also allows non-PCM bitstream storage: various compression formats contained in the RF64 file as data bursts (Dolby E, Dolby AC3, DTS, MPEG-1/MPEG-2 Audio) can be "disguised" as PCM linear.<sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup></li></ul>
<div class="mw-heading mw-heading2"><h2 id="Modulation">Modulation</h2></div>

<p>In the diagram, a <a href="Sine_wave" title="Sine wave">sine wave</a> (red curve) is sampled and quantized for PCM. The sine wave is sampled at regular intervals, shown as vertical lines. For each sample, one of the available values (on the y-axis) is chosen. The PCM process is commonly implemented on a single <a href="Integrated_circuit" title="Integrated circuit">integrated circuit</a> called an <a href="Analog-to-digital_converter" title="Analog-to-digital converter">analog-to-digital converter</a> (ADC). This produces a fully discrete representation of the input signal (blue points) that can be easily encoded as digital data for storage or manipulation. Several PCM streams could also be multiplexed into a larger aggregate <a href="Data_stream" title="Data stream">data stream</a>, generally for transmission of multiple streams over a single physical link. One technique is called <a href="Time-division_multiplexing" title="Time-division multiplexing">time-division multiplexing</a> (TDM) and is widely used, notably in the modern public telephone system.
</p>
<div class="mw-heading mw-heading2"><h2 id="Demodulation">Demodulation</h2></div>
<p>The electronics involved in producing an accurate analog signal from the discrete data are similar to those used for generating the digital signal. These devices are <a href="Digital-to-analog_converter" title="Digital-to-analog converter">digital-to-analog converters</a> (DACs). They produce a <a href="Voltage" title="Voltage">voltage</a> or <a href="Electric_current" title="Electric current">current</a> (depending on type) that represents the value presented on their digital inputs. This output would then generally be filtered and amplified for use.
</p><p>To recover the original signal from the sampled data, a <i>demodulator</i> can apply the procedure of modulation in reverse. After each sampling period, the demodulator reads the next value and transitions the output signal to the new value. As a result of these transitions, the signal retains a significant amount of high-frequency energy due to imaging effects. To remove these undesirable frequencies, the demodulator passes the signal through a <a href="Reconstruction_filter" title="Reconstruction filter">reconstruction filter</a> that suppresses energy outside the expected frequency range (greater than the <a href="Nyquist_frequency" title="Nyquist frequency">Nyquist frequency</a> <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle f_{s}/2}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>f</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>s</mi>
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<mn>2</mn>
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<annotation encoding="application/x-tex">{\displaystyle f_{s}/2}</annotation>
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</math></span><img src="./9ec3aa7a5391f6df43f4893c2a0565d910b1fbb0.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:4.467ex; height:2.843ex;" alt="{\displaystyle f_{s}/2}" loading="lazy"></span>).<sup id="cite_ref-35" class="reference"><a href="#cite_note-35"><span class="cite-bracket">[</span>note 4<span class="cite-bracket">]</span></a></sup>
</p>
<div class="mw-heading mw-heading2"><h2 id="Standard_sampling_precision_and_rates">Standard sampling precision and rates</h2></div>
<p>Common sample depths for LPCM are 8, 16, 20 or 24 bits per <a href="Sample_(signal)" class="mw-redirect" title="Sample (signal)">sample</a>.<sup id="cite_ref-rfc2586_1-2" class="reference"><a href="#cite_note-rfc2586-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-rfc4856_2-1" class="reference"><a href="#cite_note-rfc4856-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-rfc3190_3-2" class="reference"><a href="#cite_note-rfc3190-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-36" class="reference"><a href="#cite_note-36"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup>
</p><p>LPCM encodes a single sound channel. Support for multichannel audio depends on file format and relies on synchronization of multiple LPCM streams.<sup id="cite_ref-LOC_LPCM_5-2" class="reference"><a href="#cite_note-LOC_LPCM-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> While two channels (stereo) is the most common format, systems can support up to 8 audio channels (7.1 surround)<sup id="cite_ref-rfc4856_2-2" class="reference"><a href="#cite_note-rfc4856-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-rfc3190_3-3" class="reference"><a href="#cite_note-rfc3190-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> or more.
</p><p>Common sampling frequencies are 48 <a href="KHz" class="mw-redirect" title="KHz">kHz</a> as used with <a href="DVD" title="DVD">DVD</a> format videos, or 44.1&nbsp;kHz as used in CDs. Sampling frequencies of 96&nbsp;kHz or 192&nbsp;kHz can be used on some equipment, but the <a href="High-resolution_audio#Controversy" title="High-resolution audio">benefits have been debated</a>.<sup id="cite_ref-38" class="reference"><a href="#cite_note-38"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup>
</p>
<div class="mw-heading mw-heading2"><h2 id="Limitations">Limitations</h2></div>
<p>The <a href="Nyquist%E2%80%93Shannon_sampling_theorem" title="Nyquist–Shannon sampling theorem">Nyquist–Shannon sampling theorem</a> shows PCM devices can operate without introducing distortions within their designed frequency bands if they provide a sampling frequency at least twice that of the highest frequency contained in the input signal. For example, in <a href="Telephony" title="Telephony">telephony</a>, the usable <a href="Voice_frequency" title="Voice frequency">voice frequency</a> band ranges from approximately 300 to 3400&nbsp;<a href="Hz" class="mw-redirect" title="Hz">Hz</a>.<sup id="cite_ref-39" class="reference"><a href="#cite_note-39"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> For effective reconstruction of the voice signal, telephony applications therefore typically use an 8000&nbsp;Hz sampling frequency which is more than twice the highest usable voice frequency.
</p><p>Regardless, there are potential sources of impairment implicit in any PCM system:
</p>
<ul><li>Choosing a discrete value that is near but not exactly at the analog signal level for each sample leads to <a href="Quantization_error" class="mw-redirect" title="Quantization error">quantization error</a>. When <a href="Dither" title="Dither">dithering</a> is used to compensate for this, it introduces additional noise.<sup id="cite_ref-40" class="reference"><a href="#cite_note-40"><span class="cite-bracket">[</span>note 5<span class="cite-bracket">]</span></a></sup></li>
<li>Between samples no measurement of the signal is made; the sampling theorem guarantees non-ambiguous representation and recovery of the signal only if it has no energy at frequency <i>f<sub>s</sub></i>/2 or higher (one half the sampling frequency, known as the <a href="Nyquist_frequency" title="Nyquist frequency">Nyquist frequency</a>); higher frequencies will not be correctly represented or recovered and add aliasing distortion to the signal below the Nyquist frequency.</li>
<li>As samples are dependent on time, an accurate clock is required for accurate reproduction. If either the encoding or decoding clock is not stable, these imperfections will directly affect the output quality of the device.<sup id="cite_ref-41" class="reference"><a href="#cite_note-41"><span class="cite-bracket">[</span>note 6<span class="cite-bracket">]</span></a></sup></li></ul>
<div class="mw-heading mw-heading2"><h2 id="Processing_and_coding">Processing and coding</h2></div>
<p>Some forms of PCM combine signal processing with coding. Older versions of these systems applied the processing in the analog domain as part of the analog-to-digital process; newer implementations do so in the digital domain. These simple techniques have been largely rendered obsolete by modern transform-based <a href="Audio_compression_(data)" class="mw-redirect" title="Audio compression (data)">audio compression</a> techniques, such as <a href="Modified_discrete_cosine_transform" title="Modified discrete cosine transform">modified discrete cosine transform</a> (MDCT) coding.
</p>
<ul><li>Linear PCM (LPCM) is PCM with linear quantization.<sup id="cite_ref-LOC_LPCM_5-3" class="reference"><a href="#cite_note-LOC_LPCM-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup></li>
<li><a href="Differential_PCM" class="mw-redirect" title="Differential PCM">Differential PCM</a> (DPCM) encodes the PCM values as differences between the current and the predicted value. An algorithm predicts the next sample based on the previous samples, and the encoder stores only the difference between this prediction and the actual value. If the prediction is reasonable, fewer bits can be used to represent the same information. For audio, this type of encoding reduces the number of bits required per sample by about 25% compared to PCM.</li>
<li><a href="Adaptive_differential_pulse-code_modulation" title="Adaptive differential pulse-code modulation">Adaptive differential pulse-code modulation</a> (ADPCM) is a variant of DPCM that varies the size of the quantization step, to allow further reduction of the required bandwidth for a given <a href="Signal-to-noise_ratio" title="Signal-to-noise ratio">signal-to-noise ratio</a>.</li>
<li><a href="Delta_modulation" title="Delta modulation">Delta modulation</a> is a form of DPCM that uses one bit per sample to indicate whether the signal is increasing or decreasing compared to the previous sample.</li></ul>
<p>In telephony, a standard audio signal for a single phone call is encoded as 8,000 <a href="Samples_per_second" class="mw-redirect" title="Samples per second">samples per second</a>, of 8 bits each, giving a 64&nbsp;kbit/s digital signal known as <a href="DS0" class="mw-redirect" title="DS0">DS0</a>. The default <a href="Signal_compression" title="Signal compression">signal compression</a> encoding on a DS0 is either <a href="Mu-law_algorithm" class="mw-redirect" title="Mu-law algorithm">μ-law (mu-law)</a> PCM (North America and Japan) or <a href="A-law" class="mw-redirect" title="A-law">A-law</a> PCM (Europe and most of the rest of the world). These are logarithmic compression systems where a 12- or 13-bit linear PCM sample number is mapped into an 8-bit value. This system is described by international standard <a href="G.711" title="G.711">G.711</a>.
</p><p>Where circuit costs are high and loss of voice quality is acceptable, it sometimes makes sense to compress the voice signal even further. An ADPCM algorithm is used to map a series of 8-bit μ-law or A-law PCM samples into a series of 4-bit ADPCM samples. In this way, the capacity of the line is doubled. The technique is detailed in the <a href="G.726" title="G.726">G.726</a> standard.
</p><p><a href="Audio_coding_formats" class="mw-redirect" title="Audio coding formats">Audio coding formats</a> and <a href="Audio_codecs" class="mw-redirect" title="Audio codecs">audio codecs</a> have been developed to achieve further compression. Some of these techniques have been standardized and patented. Advanced compression techniques, such as <a href="Modified_discrete_cosine_transform" title="Modified discrete cosine transform">modified discrete cosine transform</a> (MDCT) and <a href="Linear_predictive_coding" title="Linear predictive coding">linear predictive coding</a> (LPC), are now widely used in <a href="Mobile_phones" class="mw-redirect" title="Mobile phones">mobile phones</a>, <a href="Voice_over_IP" title="Voice over IP">voice over IP</a> (VoIP) and <a href="Streaming_media" title="Streaming media">streaming media</a>.
</p>
<div class="mw-heading mw-heading2"><h2 id="Encoding_for_serial_transmission">Encoding for serial transmission</h2></div>
<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Line_code" title="Line code">Line code</a></div>
<div role="note" class="hatnote navigation-not-searchable">See also: <a href="T-carrier" title="T-carrier">T-carrier</a> and <a href="E-carrier" title="E-carrier">E-carrier</a></div>
<p>PCM can be either <a href="Return-to-zero" title="Return-to-zero">return-to-zero</a> (RZ) or <a href="Non-return-to-zero" title="Non-return-to-zero">non-return-to-zero</a> (NRZ). For a NRZ system to be synchronized using in-band information, there must not be long sequences of identical symbols, such as ones or zeroes. For binary PCM systems, the density of 1-symbols is called <i>ones-density</i>.<sup id="cite_ref-42" class="reference"><a href="#cite_note-42"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup>
</p><p>Ones-density is often controlled using precoding techniques such as <a href="Run-length_limited" title="Run-length limited">run-length limited</a> encoding, where the PCM code is expanded into a slightly longer code with a guaranteed bound on ones-density before modulation into the channel. In other cases, extra <a href="Framing_bit" class="mw-redirect" title="Framing bit">framing bits</a> are added into the stream, which guarantees at least occasional symbol transitions.
</p><p>Another technique used to control ones-density is the use of a <a href="Scrambler" title="Scrambler">scrambler</a> on the data, which will tend to turn the data stream into a stream that looks <a href="Pseudo-random" class="mw-redirect" title="Pseudo-random">pseudo-random</a>, but where the data can be recovered exactly by a complementary descrambler. In this case, long runs of zeroes or ones are still possible on the output but are considered unlikely enough to allow reliable synchronization.
</p><p>In other cases, the long term DC value of the modulated signal is important, as building up a <a href="DC_bias" title="DC bias">DC bias</a> will tend to move communications circuits out of their operating range. In this case, special measures are taken to keep a count of the cumulative DC bias and to modify the codes if necessary to make the DC bias always tend back to zero.
</p><p>Many of these codes are <a href="Bipolar_code" class="mw-redirect" title="Bipolar code">bipolar codes</a>, where the pulses can be positive, negative or absent. In the typical <a href="Alternate_mark_inversion" class="mw-redirect" title="Alternate mark inversion">alternate mark inversion</a> code, non-zero pulses alternate between being positive and negative. These rules may be violated to generate special symbols used for framing or other special purposes.
</p>
<div class="mw-heading mw-heading2"><h2 id="Nomenclature">Nomenclature</h2></div>
<p>The word <i>pulse</i> in the term <i>pulse-code modulation</i> refers to the pulses to be found in the transmission line. This perhaps is a natural consequence of this technique having evolved alongside two analog methods, <a href="Pulse-width_modulation" title="Pulse-width modulation">pulse-width modulation</a> and <a href="Pulse-position_modulation" title="Pulse-position modulation">pulse-position modulation</a>, in which the information to be encoded is represented by discrete signal pulses of varying width or position, respectively. In this respect, PCM bears little resemblance to these other forms of signal encoding, except that all can be used in time-division multiplexing, and the numbers of the PCM codes are represented as electrical pulses.
</p>
<div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2></div>
<ul><li><a href="Beta_encoder" title="Beta encoder">Beta encoder</a></li>
<li><a href="Equivalent_pulse_code_modulation_noise" title="Equivalent pulse code modulation noise">Equivalent pulse code modulation noise</a></li>
<li><a href="Signal-to-quantization-noise_ratio" title="Signal-to-quantization-noise ratio">Signal-to-quantization-noise ratio</a> (SQNR), one method of measuring quantization error</li></ul>
<div class="mw-heading mw-heading2"><h2 id="Explanatory_notes">Explanatory notes</h2></div>
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<li id="cite_note-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-22">^</a></b></span> <span class="reference-text">Among the first recordings was <i>Uzu: The World Of Stomu Yamash'ta 2</i> by <a href="Stomu_Yamashta" title="Stomu Yamashta">Stomu Yamashta</a>.</span>
</li>
<li id="cite_note-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-23">^</a></b></span> <span class="reference-text">The first recording with this new system was recorded in <a href="Tokyo" title="Tokyo">Tokyo</a> during April 24–26, 1972.</span>
</li>
<li id="cite_note-27"><span class="mw-cite-backlink"><b><a href="#cite_ref-27">^</a></b></span> <span class="reference-text">Other methods exist such as <a href="Pulse-density_modulation" title="Pulse-density modulation">pulse-density modulation</a> used also on <a href="Super_Audio_CD" title="Super Audio CD">Super Audio CD</a>.</span>
</li>
<li id="cite_note-35"><span class="mw-cite-backlink"><b><a href="#cite_ref-35">^</a></b></span> <span class="reference-text">Some systems use <a href="Digital_filter" title="Digital filter">digital filtering</a> to remove some of the aliasing, converting the signal from digital to analog at a higher sample rate such that the analog <a href="Anti-aliasing_filter" title="Anti-aliasing filter">anti-aliasing filter</a> is much simpler. In some systems, no explicit filtering is done at all; as it is impossible for any system to reproduce a signal with infinite bandwidth, inherent losses in the system compensate for the artifacts — or the system simply does not require much precision.</span>
</li>
<li id="cite_note-40"><span class="mw-cite-backlink"><b><a href="#cite_ref-40">^</a></b></span> <span class="reference-text">Quantization error swings between -<i>q</i>/2 and <i>q</i>/2. In the ideal case (with a fully linear ADC and signal level &gt;&gt; <i>q</i>) it is <a href="Uniform_distribution_(continuous)" class="mw-redirect" title="Uniform distribution (continuous)">uniformly distributed</a> over this interval, with zero mean and variance of <i>q</i><sup>2</sup>/12.</span>
</li>
<li id="cite_note-41"><span class="mw-cite-backlink"><b><a href="#cite_ref-41">^</a></b></span> <span class="reference-text">A slight difference between the encoding and decoding clock frequencies is not generally a major concern; a small constant error is not noticeable. Clock error does become a major issue if the clock contains significant <a href="Jitter" title="Jitter">jitter</a>, however.</span>
</li>
</ol></div></div>
<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>
<div class="reflist">
<div class="mw-references-wrap mw-references-columns"><ol class="references">
<li id="cite_note-rfc2586-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-rfc2586_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-rfc2586_1-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-rfc2586_1-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">
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<div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2></div>
<ul><li><cite id="CITEREFFranklin_S._CooperIgnatius_Mattingly1969" class="citation journal cs1"><a href="Franklin_S._Cooper" title="Franklin S. Cooper">Franklin S. Cooper</a>; Ignatius Mattingly (1969). <a rel="nofollow" class="external text" href="https://doi.org/10.1121%2F1.1972688">"Computer-controlled PCM system for investigation of dichotic speech perception"</a>. <i>Journal of the Acoustical Society of America</i>. <b>46</b> (1A): 115. <a href="Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1969ASAJ...46..115C">1969ASAJ...46..115C</a>. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1121%2F1.1972688">10.1121/1.1972688</a></span>.</cite></li>
<li><cite id="CITEREFKen_C._Pohlmann1985" class="citation book cs1">Ken C. Pohlmann (1985). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/principlesofdigi00pohl"><i>Principles of Digital Audio</i></a></span> (2nd&nbsp;ed.). Carmel, Indiana: Sams/Prentice-Hall Computer Publishing. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a>&nbsp;<bdi>978-0-672-22634-2</bdi>.</cite></li>
<li><cite id="CITEREFD._H._Whalen,_E._R._Wiley,_Philip_E._Rubin,_and_Franklin_S._Cooper1990" class="citation journal cs1"><a href="Douglas_Whalen" title="Douglas Whalen">D. H. Whalen</a>, E. R. Wiley, <a href="Philip_Rubin" title="Philip Rubin">Philip E. Rubin</a>, and <a href="Franklin_S._Cooper" title="Franklin S. Cooper">Franklin S. Cooper</a> (1990). <a href="Haskins_Laboratories" title="Haskins Laboratories">"The Haskins Laboratories pulse code modulation (PCM) system"</a>. <i>Behavior Research Methods, Instruments, and Computers</i>. <b>22</b> (6): <span class="nowrap">550–</span>559. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.3758%2FBF03204440">10.3758/BF03204440</a></span>.</cite><span class="cs1-maint citation-comment"><code class="cs1-code">{{cite journal}}</code>: CS1 maint: multiple names: authors list (link)</span></li>
<li><cite id="CITEREFBill_Waggener1995" class="citation book cs1">Bill Waggener (1995). <i>Pulse Code Modulation Techniques</i> (1st&nbsp;ed.). New York, NY: Van Nostrand Reinhold. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a>&nbsp;<bdi>978-0-442-01436-0</bdi>.</cite></li>
<li><cite id="CITEREFBill_Waggener1999" class="citation book cs1">Bill Waggener (1999). <i>Pulse Code Modulation Systems Design</i> (1st&nbsp;ed.). Boston, MA: Artech House. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a>&nbsp;<bdi>978-0-89006-776-5</bdi>.</cite></li></ul>
<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>
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<div class="side-box-text plainlist">Wikimedia Commons has media related to <span style="font-weight: bold; font-style: italic;"><a href="https://commons.wikimedia.org/wiki/Category:Pulse-code_modulation" class="extiw external" title="commons:Category:Pulse-code modulation">Pulse-code modulation</a></span>.</div></div>
</div>
<ul><li><a rel="nofollow" class="external text" href="http://wiki.multimedia.cx/index.php?title=PCM">PCM description on MultimediaWiki</a></li>
<li><a rel="nofollow" class="external text" href="http://www.ralph-miller.org/">Ralph Miller</a> and Bob Badgley invented multi-level PCM independently in their work at Bell Labs on <a href="SIGSALY" title="SIGSALY">SIGSALY</a>: <span><a rel="nofollow" class="external text" href="https://patents.google.com/patent/US3912868">U.S. patent 3,912,868</a></span> filed in 1943: N-ary Pulse Code Modulation.</li>
<li><a rel="nofollow" class="external text" href="https://www.loc.gov/preservation/digital/formats/fdd/fdd000016.shtml">Information about PCM</a>: A description of PCM with links to information about subtypes of this format (for example <a href="Linear_pulse-code_modulation" class="mw-redirect" title="Linear pulse-code modulation">linear pulse-code modulation</a>), and references to their specifications.</li>
<li><a rel="nofollow" class="external text" href="https://www.loc.gov/preservation/digital/formats/fdd/fdd000011.shtml">Summary of LPCM</a> – Contains links to information about implementations and their specifications.</li>
<li><a rel="nofollow" class="external text" href="http://www.tactilemedia.com/info/MCI_Control_Info.html">How to control internal/external hardware using Microsoft's Media Control Interface</a> – Contains information about, and specifications for the implementation of LPCM used in WAV files.</li>
<li><a rel="nofollow" class="external text" href="http://tools.ietf.org/html/rfc4856">RFC 4856 – Media Type Registration of Payload Formats in the RTP Profile for Audio and Video Conferences</a> – audio/L8 and audio/L16 (March 2007)</li>
<li><a rel="nofollow" class="external text" href="http://tools.ietf.org/html/rfc3190">RFC 3190 – RTP Payload Format for 12-bit DAT Audio and 20- and 24-bit Linear Sampled Audio</a> (January 2002)</li>
<li><a rel="nofollow" class="external text" href="http://tools.ietf.org/html/rfc3551#page-27">RFC 3551 – RTP Profile for Audio and Video Conferences with Minimal Control</a> – L8 and L16 (July 2003)</li></ul>
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/* end https://en.wikipedia.org/ */
</style></div><div role="navigation" class="navbox" aria-labelledby="High-definition_(HD)301" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><div id="High-definition_(HD)301" style="font-size:114%;margin:0 4em">High-definition (HD)</div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Concepts</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="High-definition_television" title="High-definition television">High-definition television</a></li>
<li><a href="High-definition_video" title="High-definition video">High-definition video</a></li>
<li><a href="Ultra-high-definition_television" title="Ultra-high-definition television">Ultra-high-definition television</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Resolutions</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="720p" title="720p">720p (HD)</a></li>
<li><a href="1080i" title="1080i">1080i (HD)</a></li>
<li><a href="1080p" title="1080p">1080p (Full HD)</a></li>
<li><a href="1440p" title="1440p">1440p (Quad HD)</a></li>
<li><a href="4K_resolution" title="4K resolution">2160p (4K Ultra HD)</a></li>
<li><a href="8K_resolution" title="8K resolution">4320p (8K Ultra HD)</a></li>
<li><a href="16K_resolution" title="16K resolution">8640p (16K Ultra HD)</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Analog_high-definition_television_system" class="mw-redirect" title="Analog high-definition television system">Analog broadcast</a><br><span style="font-size: 85%;">(All defunct)</span></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Analog_high-definition_television_system" class="mw-redirect" title="Analog high-definition television system">819 line system</a></li>
<li><a href="Multiplexed_Analogue_Components" title="Multiplexed Analogue Components">HD MAC</a></li>
<li><a href="Multiple_sub-Nyquist_sampling_encoding" title="Multiple sub-Nyquist sampling encoding">MUSE (Hi-Vision)</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Digital broadcast</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="ATSC_standards" title="ATSC standards">ATSC</a></li>
<li><a href="Digital_Terrestrial_Multimedia_Broadcast" title="Digital Terrestrial Multimedia Broadcast">DMB-T/H</a></li>
<li><a href="Digital_Video_Broadcasting" class="mw-redirect" title="Digital Video Broadcasting">DVB</a></li>
<li><a href="ISDB" title="ISDB">ISDB</a></li>
<li><a href="ISDB-T_International" title="ISDB-T International">SBTVD</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Audio</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Dolby_Digital" title="Dolby Digital">Dolby Digital</a></li>
<li><a href="Surround_sound" title="Surround sound">Surround sound</a></li>
<li><a href="Direct_Stream_Digital" title="Direct Stream Digital">DSD</a></li>
<li><a href="Digital_eXtreme_Definition" title="Digital eXtreme Definition">DXD</a></li>
<li><a href="DTS_(sound_system)" class="mw-redirect" title="DTS (sound system)">DTS</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Filming and storage</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Digital_Cinema_Initiatives" title="Digital Cinema Initiatives">DCI</a></li>
<li><a href="HDV" title="HDV">HDV</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="High-definition_pre-recorded_media_and_compression" title="High-definition pre-recorded media and compression">HD media and<br>compression</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Archival_Disc" title="Archival Disc">Archival Disc</a></li>
<li><a href="AV1" title="AV1">AV1</a></li>
<li><a href="Blu-ray" title="Blu-ray">Blu-ray</a></li>
<li><a href="China_Blue_High-definition_Disc" title="China Blue High-definition Disc">CBHD</a></li>
<li><a href="D-VHS" title="D-VHS">D-VHS</a></li>
<li><a href="DVD-Audio" title="DVD-Audio">DVD-Audio</a></li>
<li><a href="Advanced_Video_Coding" title="Advanced Video Coding">H.264</a></li>
<li><a href="High_Efficiency_Video_Coding" title="High Efficiency Video Coding">H.265</a></li>
<li><a href="Versatile_Video_Coding" title="Versatile Video Coding">H.266</a></li>
<li><a href="HD_DVD" title="HD DVD">HD DVD</a></li>
<li><a href="Versatile_Multilayer_Disc" title="Versatile Multilayer Disc">HD VMD</a></li>
<li><a href="Laserdisc" class="mw-redirect" title="Laserdisc">Hi-Vision LD</a></li>
<li><a href="MPEG-2" title="MPEG-2">MPEG-2</a></li>
<li><a href="Multiview_Video_Coding" title="Multiview Video Coding">MVC</a></li>
<li><a href="Super_Audio_CD" title="Super Audio CD">Super Audio CD</a></li>
<li><a href="Ultra_HD_Blu-ray" title="Ultra HD Blu-ray">Ultra HD Blu-ray</a></li>
<li><a href="Uncompressed_video" title="Uncompressed video">Uncompressed</a></li>
<li><a href="VC-1" title="VC-1">VC-1</a></li>
<li><a href="W-VHS" title="W-VHS">W-VHS</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Connectors</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Component_video" title="Component video">Component</a></li>
<li><a href="DisplayPort" title="DisplayPort">DisplayPort</a></li>
<li><a href="Digital_Visual_Interface" title="Digital Visual Interface">DVI</a></li>
<li><a href="GPMI" title="GPMI">GPMI</a></li>
<li><a href="HDMI" title="HDMI">HDMI</a></li>
<li><a href="VGA_connector" title="VGA connector">VGA</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Deployments</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="List_of_digital_television_deployments_by_country" title="List of digital television deployments by country">List of digital television deployments by country</a></li></ul>
</div></td></tr></tbody></table></div>
<div class="skin-invert-image"><div class="navbox-styles"></div><div role="navigation" class="navbox" aria-labelledby="Line_coding_(digital_baseband_transmission)443" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="3"><div id="Line_coding_(digital_baseband_transmission)443" style="font-size:114%;margin:0 4em"><a href="Line_coding" class="mw-redirect" title="Line coding">Line coding</a> (digital baseband transmission)</div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Main articles</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Unipolar_encoding" title="Unipolar encoding">Unipolar encoding</a></li>
<li><a href="Bipolar_encoding" title="Bipolar encoding">Bipolar encoding</a></li>
<li><a href="On%E2%80%93off_keying" title="On–off keying">On–off keying</a></li>
<li><a href="Mark_and_space" title="Mark and space">Mark and space</a></li></ul>
</div></td><td class="noviewer navbox-image" rowspan="4" style="width:1px;padding:0 0 0 2px"><div><span typeof="mw:File"></span></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Basic <a href="Line_code" title="Line code">line codes</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Return-to-zero" title="Return-to-zero">Return to zero (RZ)</a></li>
<li><a href="Non-return-to-zero#Non-return-to-zero_level" title="Non-return-to-zero">Non-return-to-zero, level (NRZ/NRZ-L)</a></li>
<li><a href="Non-return-to-zero#Non-return-to-zero_inverted" title="Non-return-to-zero">Non-return-to-zero, inverted (NRZ-I)</a></li>
<li><a href="Non-return-to-zero#Non-return-to-zero_space" title="Non-return-to-zero">Non-return-to-zero, space (NRZ-S)</a></li>
<li><a href="Manchester_code" title="Manchester code">Manchester</a></li>
<li><a href="Differential_Manchester_encoding" title="Differential Manchester encoding">Differential Manchester/biphase (Bi-φ)</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Extended line codes</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Conditioned_diphase" class="mw-redirect" title="Conditioned diphase">Conditioned diphase</a></li>
<li><a href="4B3T" title="4B3T">4B3T</a></li>
<li><a href="4B5B" title="4B5B">4B5B</a></li>
<li><a href="2B1Q" title="2B1Q">2B1Q</a></li>
<li><a href="Bipolar_encoding#Alternate_mark_inversion" title="Bipolar encoding">Alternate mark inversion</a></li>
<li><a href="Modified_AMI_code" title="Modified AMI code">Modified AMI code</a></li>
<li><a href="Coded_mark_inversion" title="Coded mark inversion">Coded mark inversion</a></li>
<li><a href="MLT-3_encoding" title="MLT-3 encoding">MLT-3 encoding</a></li>
<li><a href="Hybrid_ternary_code" title="Hybrid ternary code">Hybrid ternary code</a></li>
<li><a href="6b/8b_encoding" title="6b/8b encoding">6b/8b encoding</a></li>
<li><a href="8b/10b_encoding" title="8b/10b encoding">8b/10b encoding</a></li>
<li><a href="64b/66b_encoding" title="64b/66b encoding">64b/66b encoding</a></li>
<li><a href="Eight-to-fourteen_modulation" title="Eight-to-fourteen modulation">Eight-to-fourteen modulation</a></li>
<li><a href="Delay_encoding" class="mw-redirect" title="Delay encoding">Delay/Miller encoding</a></li>
<li><a href="TC-PAM" title="TC-PAM">TC-PAM</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Optical line codes</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Carrier-suppressed_return-to-zero" class="mw-redirect" title="Carrier-suppressed return-to-zero">Carrier-suppressed return-to-zero</a></li>
<li><a href="Alternate-phase_return-to-zero" class="mw-redirect" title="Alternate-phase return-to-zero">Alternate-phase return-to-zero</a></li></ul>
</div></td></tr><tr><td class="navbox-abovebelow hlist" colspan="3"><div>
<ul><li><i>See also:</i> <a href="Baseband" title="Baseband">Baseband</a></li>
<li><a href="Baud" title="Baud">Baud</a></li>
<li><a href="Bit_rate" title="Bit rate">Bit rate</a></li>
<li><a href="Digital_signal" title="Digital signal">Digital signal</a></li>
<li><a href="Digital_transmission" class="mw-redirect" title="Digital transmission">Digital transmission</a></li>
<li><a href="Ethernet_physical_layer" title="Ethernet physical layer">Ethernet physical layer</a></li>
<li><a href="Modulation" class="mw-redirect" title="Modulation">Pulse modulation methods</a></li>
<li><a href="Pulse-amplitude_modulation" title="Pulse-amplitude modulation">Pulse-amplitude modulation</a> (PAM)</li>
<li> (PCM)</li>
<li><a href="Serial_communication" title="Serial communication">Serial communication</a></li>
<li>Category:Line codes</li></ul>
</div></td></tr></tbody></table></div></div>
<div class="navbox-styles"></div><div role="navigation" class="navbox" aria-labelledby="Telecommunications802" style="padding:3px"><table class="nowraplinks hlist mw-collapsible mw-collapsed navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><div id="Telecommunications802" style="font-size:114%;margin:0 4em"><a href="Telecommunications" title="Telecommunications">Telecommunications</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="History_of_telecommunication" title="History of telecommunication">History</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Beacon#For_defensive_communications" title="Beacon">Beacon</a></li>
<li><a href="History_of_broadcasting" title="History of broadcasting">Broadcasting</a></li>
<li><a href="Cable_protection_system" title="Cable protection system">Cable protection system</a></li>
<li><a href="Cable_television" title="Cable television">Cable TV</a></li>
<li><a href="Communications_satellite#History" title="Communications satellite">Communications satellite</a></li>
<li><a href="Computer_network#History" title="Computer network">Computer network</a></li>
<li><a href="Data_compression" title="Data compression">Data compression</a>
<ul><li><a href="Audio_coding_format" title="Audio coding format">audio</a></li>
<li><a href="Discrete_cosine_transform" title="Discrete cosine transform">DCT</a></li>
<li><a href="Image_compression" title="Image compression">image</a></li>
<li><a href="Video_coding_format" title="Video coding format">video</a></li></ul></li>
<li><a href="Digital_media" title="Digital media">Digital media</a>
<ul><li><a href="Internet_video" title="Internet video">Internet video</a></li>
<li><a href="Online_video_platform" title="Online video platform">online video platform</a></li>
<li><a href="Social_media" title="Social media">social media</a></li>
<li><a href="Streaming_media" title="Streaming media">streaming</a></li></ul></li>
<li><a href="Drums_in_communication" title="Drums in communication">Drums</a></li>
<li><a href="Edholm's_law" title="Edholm's law">Edholm's law</a></li>
<li><a href="Electrical_telegraph#History" title="Electrical telegraph">Electrical telegraph</a></li>
<li><a href="Fax#History" title="Fax">Fax</a></li>
<li><a href="Heliograph#History" title="Heliograph">Heliographs</a></li>
<li><a href="Hydraulic_telegraph#Greek_hydraulic_semaphore_system" title="Hydraulic telegraph">Hydraulic telegraph</a></li>
<li><a href="Information_Age" title="Information Age">Information Age</a></li>
<li><a href="Information_revolution" class="mw-redirect" title="Information revolution">Information revolution</a></li>
<li><a href="History_of_the_Internet" title="History of the Internet">Internet</a></li>
<li><a href="Mass_media#History" title="Mass media">Mass media</a></li>
<li><a href="History_of_mobile_phones" title="History of mobile phones">Mobile phone</a>
<ul><li><a href="Smartphone" title="Smartphone">Smartphone</a></li></ul></li>
<li><a href="Optical_communication" title="Optical communication">Optical telecommunication</a></li>
<li><a href="Optical_telegraph" title="Optical telegraph">Optical telegraphy</a></li>
<li><a href="Pager" title="Pager">Pager</a></li>
<li><a href="Photophone" title="Photophone">Photophone</a></li>
<li><a href="History_of_prepaid_mobile_phones" title="History of prepaid mobile phones">Prepaid mobile phone</a></li>
<li><a href="History_of_radio" title="History of radio">Radio</a></li>
<li><a href="Radiotelephone" title="Radiotelephone">Radiotelephone</a></li>
<li><a href="Communications_satellite" title="Communications satellite">Satellite communications</a></li>
<li><a href="Semaphore" title="Semaphore">Semaphore</a>
<ul><li><a href="Phryctoria" title="Phryctoria">Phryctoria</a></li></ul></li>
<li><a href="Semiconductor" title="Semiconductor">Semiconductor</a>
<ul><li><a href="Semiconductor_device" title="Semiconductor device">device</a></li>
<li><a href="MOSFET" title="MOSFET">MOSFET</a></li>
<li><a href="History_of_the_transistor" title="History of the transistor">transistor</a></li></ul></li>
<li><a href="Smoke_signal" title="Smoke signal">Smoke signals</a></li>
<li><a href="History_of_telecommunication" title="History of telecommunication">Telecommunications history</a></li>
<li><a href="Telautograph" title="Telautograph">Telautograph</a></li>
<li><a href="Telegraphy" title="Telegraphy">Telegraphy</a></li>
<li><a href="Teleprinter" title="Teleprinter">Teleprinter</a> (teletype)</li>
<li><a href="History_of_the_telephone" title="History of the telephone">Telephone</a></li>
<li><i><a href="The_Telephone_Cases" title="The Telephone Cases">The Telephone Cases</a></i></li>
<li><a href="History_of_television" title="History of television">Television</a>
<ul><li><a href="Digital_television" title="Digital television">digital</a></li>
<li><a href="Streaming_television" title="Streaming television">streaming</a></li></ul></li>
<li><a href="Submarine_communications_cable#Early_history:_telegraph_and_coaxial_cables" title="Submarine communications cable">Undersea telegraph line</a></li>
<li><a href="History_of_videotelephony" title="History of videotelephony">Videotelephony</a></li>
<li><a href="Whistled_language" title="Whistled language">Whistled language</a></li>
<li><a href="Wireless_revolution" class="mw-redirect" title="Wireless revolution">Wireless revolution</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Pioneers</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Nasir_Ahmed_(engineer)" title="Nasir Ahmed (engineer)">Nasir Ahmed</a></li>
<li><a href="Edwin_Howard_Armstrong" title="Edwin Howard Armstrong">Edwin Howard Armstrong</a></li>
<li><a href="Mohamed_M._Atalla" title="Mohamed M. Atalla">Mohamed M. Atalla</a></li>
<li><a href="John_Logie_Baird" title="John Logie Baird">John Logie Baird</a></li>
<li><a href="Paul_Baran" title="Paul Baran">Paul Baran</a></li>
<li><a href="John_Bardeen" title="John Bardeen">John Bardeen</a></li>
<li><a href="Alexander_Graham_Bell" title="Alexander Graham Bell">Alexander Graham Bell</a></li>
<li><a href="Emile_Berliner" title="Emile Berliner">Emile Berliner</a></li>
<li><a href="Tim_Berners-Lee" title="Tim Berners-Lee">Tim Berners-Lee</a></li>
<li><a href="Francis_Blake_(inventor)" title="Francis Blake (inventor)">Francis Blake</a></li>
<li><a href="Jagadish_Chandra_Bose" title="Jagadish Chandra Bose">Jagadish Chandra Bose</a></li>
<li><a href="Charles_Bourseul" title="Charles Bourseul">Charles Bourseul</a></li>
<li><a href="Walter_Houser_Brattain" class="mw-redirect" title="Walter Houser Brattain">Walter Houser Brattain</a></li>
<li><a href="Vint_Cerf" title="Vint Cerf">Vint Cerf</a></li>
<li><a href="Claude_Chappe" title="Claude Chappe">Claude Chappe</a></li>
<li><a href="Yogen_Dalal" class="mw-redirect" title="Yogen Dalal">Yogen Dalal</a></li>
<li><a href="Donald_Davies" title="Donald Davies">Donald Davies</a></li>
<li><a href="Daniel_Davis_Jr." title="Daniel Davis Jr.">Daniel Davis Jr.</a></li>
<li><a href="Amos_Dolbear" title="Amos Dolbear">Amos Dolbear</a></li>
<li><a href="Thomas_Edison" title="Thomas Edison">Thomas Edison</a></li>
<li><a href="Philo_Farnsworth" title="Philo Farnsworth">Philo Farnsworth</a></li>
<li><a href="Reginald_Fessenden" title="Reginald Fessenden">Reginald Fessenden</a></li>
<li><a href="Lee_de_Forest" title="Lee de Forest">Lee de Forest</a></li>
<li><a href="Elisha_Gray" title="Elisha Gray">Elisha Gray</a></li>
<li><a href="Oliver_Heaviside" title="Oliver Heaviside">Oliver Heaviside</a></li>
<li><a href="Robert_Hooke" title="Robert Hooke">Robert Hooke</a></li>
<li><a href="Erna_Schneider_Hoover" title="Erna Schneider Hoover">Erna Schneider Hoover</a></li>
<li><a href="Harold_Hopkins_(physicist)" title="Harold Hopkins (physicist)">Harold Hopkins</a></li>
<li><a href="Gardiner_Greene_Hubbard" title="Gardiner Greene Hubbard">Gardiner Greene Hubbard</a></li>
<li><a href="Bob_Kahn" class="mw-redirect" title="Bob Kahn">Bob Kahn</a></li>
<li><a href="Dawon_Kahng" title="Dawon Kahng">Dawon Kahng</a></li>
<li><a href="Charles_K._Kao" title="Charles K. Kao">Charles K. Kao</a></li>
<li><a href="Narinder_Singh_Kapany" title="Narinder Singh Kapany">Narinder Singh Kapany</a></li>
<li><a href="Hedy_Lamarr" title="Hedy Lamarr">Hedy Lamarr</a></li>
<li><a href="Roberto_Landell_de_Moura" title="Roberto Landell de Moura">Roberto Landell</a></li>
<li><a href="Innocenzo_Manzetti" title="Innocenzo Manzetti">Innocenzo Manzetti</a></li>
<li><a href="Guglielmo_Marconi" title="Guglielmo Marconi">Guglielmo Marconi</a></li>
<li><a href="Robert_Metcalfe" title="Robert Metcalfe">Robert Metcalfe</a></li>
<li><a href="Antonio_Meucci" title="Antonio Meucci">Antonio Meucci</a></li>
<li><a href="Samuel_Morse" title="Samuel Morse">Samuel Morse</a></li>
<li><a href="Jun-ichi_Nishizawa" title="Jun-ichi Nishizawa">Jun-ichi Nishizawa</a></li>
<li><a href="Charles_Grafton_Page" title="Charles Grafton Page">Charles Grafton Page</a></li>
<li><a href="Radia_Perlman" title="Radia Perlman">Radia Perlman</a></li>
<li><a href="Alexander_Stepanovich_Popov" class="mw-redirect" title="Alexander Stepanovich Popov">Alexander Stepanovich Popov</a></li>
<li><a href="Tivadar_Pusk%C3%A1s" title="Tivadar Puskás">Tivadar Puskás</a></li>
<li><a href="Johann_Philipp_Reis" title="Johann Philipp Reis">Johann Philipp Reis</a></li>
<li><a href="Claude_Shannon" title="Claude Shannon">Claude Shannon</a></li>
<li><a href="Almon_Brown_Strowger" title="Almon Brown Strowger">Almon Brown Strowger</a></li>
<li><a href="Henry_Sutton_(inventor)" title="Henry Sutton (inventor)">Henry Sutton</a></li>
<li><a href="Charles_Sumner_Tainter" title="Charles Sumner Tainter">Charles Sumner Tainter</a></li>
<li><a href="Nikola_Tesla" title="Nikola Tesla">Nikola Tesla</a></li>
<li><a href="Camille_Tissot" title="Camille Tissot">Camille Tissot</a></li>
<li><a href="Alfred_Vail" title="Alfred Vail">Alfred Vail</a></li>
<li><a href="Thomas_A._Watson" title="Thomas A. Watson">Thomas A. Watson</a></li>
<li><a href="Charles_Wheatstone" title="Charles Wheatstone">Charles Wheatstone</a></li>
<li><a href="Vladimir_K._Zworykin" title="Vladimir K. Zworykin">Vladimir K. Zworykin</a></li>
<li><i><a href="List_of_Internet_pioneers" title="List of Internet pioneers">Internet pioneers</a></i></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Transmission_medium" title="Transmission medium">Transmission<br>media</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Coaxial_cable" title="Coaxial cable">Coaxial cable</a></li>
<li><a href="Fiber-optic_communication" title="Fiber-optic communication">Fiber-optic communication</a>
<ul><li><a href="Optical_fiber" title="Optical fiber">optical fiber</a></li></ul></li>
<li><a href="Free-space_optical_communication" title="Free-space optical communication">Free-space optical communication</a></li>
<li><a href="Molecular_communication" title="Molecular communication">Molecular communication</a></li>
<li><a href="Radio_wave" title="Radio wave">Radio waves</a>
<ul><li><a href="Wireless" title="Wireless">wireless</a></li></ul></li>
<li><a href="Transmission_line" title="Transmission line">Transmission line</a>
<ul><li><a href="Telecommunication_circuit" title="Telecommunication circuit">telecommunication circuit</a></li></ul></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Network_topology" title="Network topology">Network topology</a><br>and switching</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Bandwidth_(computing)" title="Bandwidth (computing)">Bandwidth</a></li>
<li><a href="Telecommunications_link" title="Telecommunications link">Links</a></li>
<li><a href="Network_switch" title="Network switch">Network switching</a>
<ul><li><a href="Circuit_switching" title="Circuit switching">circuit</a></li>
<li><a href="Packet_switching" title="Packet switching">packet</a></li></ul></li>
<li><a href="Node_(networking)" title="Node (networking)">Nodes</a>
<ul><li><a href="Terminal_(telecommunication)" title="Terminal (telecommunication)">terminal</a></li></ul></li>
<li><a href="Telephone_exchange" title="Telephone exchange">Telephone exchange</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Multiplexing" title="Multiplexing">Multiplexing</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Space-division_multiple_access" title="Space-division multiple access">Space-division</a></li>
<li><a href="Frequency-division_multiplexing" title="Frequency-division multiplexing">Frequency-division</a></li>
<li><a href="Time-division_multiplexing" title="Time-division multiplexing">Time-division</a></li>
<li><a href="Polarization-division_multiplexing" title="Polarization-division multiplexing">Polarization-division</a></li>
<li><a href="Orbital_angular_momentum_multiplexing" title="Orbital angular momentum multiplexing">Orbital angular-momentum</a></li>
<li><a href="Code-division_multiple_access" title="Code-division multiple access">Code-division</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Concepts</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Communication_protocol" title="Communication protocol">Communication protocol</a></li>
<li><a href="Computer_network" title="Computer network">Computer network</a></li>
<li><a href="Data_communication" title="Data communication">Data transmission</a></li>
<li><a href="Store_and_forward" title="Store and forward">Store and forward</a></li>
<li><a href="Telecommunications_equipment" title="Telecommunications equipment">Telecommunications equipment</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Telecommunications_network" title="Telecommunications network">Types of network</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Cellular_network" title="Cellular network">Cellular network</a></li>
<li><a href="Ethernet" title="Ethernet">Ethernet</a></li>
<li><a href="Integrated_Services_Digital_Network" class="mw-redirect" title="Integrated Services Digital Network">ISDN</a></li>
<li><a href="Local_area_network" title="Local area network">LAN</a></li>
<li><a href="Mobile_telephony" title="Mobile telephony">Mobile</a></li>
<li><a href="Next-generation_network" title="Next-generation network">NGN</a></li>
<li><a href="Public_switched_telephone_network" title="Public switched telephone network">Public Switched Telephone</a></li>
<li><a href="Radio_network" title="Radio network">Radio</a></li>
<li><a href="Television_broadcasting" class="mw-redirect" title="Television broadcasting">Television</a></li>
<li><a href="Telex" title="Telex">Telex</a></li>
<li><a href="UUCP" title="UUCP">UUCP</a></li>
<li><a href="Wide_area_network" title="Wide area network">WAN</a></li>
<li><a href="Wireless_network" title="Wireless network">Wireless network</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Telecommunications_network" title="Telecommunications network">Notable networks</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="ARPANET" title="ARPANET">ARPANET</a></li>
<li><a href="BITNET" title="BITNET">BITNET</a></li>
<li><a href="CYCLADES" title="CYCLADES">CYCLADES</a></li>
<li><a href="FidoNet" title="FidoNet">FidoNet</a></li>
<li><a href="Internet" title="Internet">Internet</a></li>
<li><a href="Internet2" title="Internet2">Internet2</a></li>
<li><a href="JANET" title="JANET">JANET</a></li>
<li><a href="NPL_network" title="NPL network">NPL network</a></li>
<li><a href="TANet" title="TANet">TANet</a></li>
<li><a href="Toasternet" title="Toasternet">Toasternet</a></li>
<li><a href="Usenet" title="Usenet">Usenet</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Locations</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li>Africa</li>
<li>Americas
<ul><li>North</li>
<li>South</li></ul></li>
<li>Antarctica</li>
<li>Asia</li>
<li>Europe</li>
<li>Oceania</li>
<li><i><a href="List_of_telecommunications_regulatory_bodies" title="List of telecommunications regulatory bodies">Global telecommunications regulation bodies</a></i></li></ul>
</div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div>
<ul><li><span class="nowrap"><span class="noviewer" typeof="mw:File"><span></span></span> </span><a href="Portal%3ATelecommunication" title="Portal:Telecommunication">Telecommunication portal</a></li>
<li><span class="noviewer" typeof="mw:File"><span title="Category"></span></span> Category</li>
<li><span class="noviewer" typeof="mw:File"><span title="List-Class article"></span></span> <a href="Outline_of_telecommunication" title="Outline of telecommunication">Outline</a></li>
<li><span class="noviewer" typeof="mw:File"><span title="Commons page"></span></span> <a href="https://commons.wikimedia.org/wiki/Category:Telecommunications" class="extiw external" title="commons:Category:Telecommunications">Commons</a></li></ul>
</div></td></tr></tbody></table></div>
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</style></div><div role="navigation" class="navbox authority-control" aria-label="Navbox973" style="padding:3px"><table class="nowraplinks hlist navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="row" class="navbox-group" style="width:1%">Authority control databases: National </th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"><ul><li><span class="uid"><span class="rt-commentedText tooltip tooltip-dotted" title="Modulation par impulsions codées"><a rel="nofollow" class="external text" href="https://catalogue.bnf.fr/ark:/12148/cb136023289">France</a></span></span></li><li><span class="uid"><span class="rt-commentedText tooltip tooltip-dotted" title="Modulation par impulsions codées"><a rel="nofollow" class="external text" href="https://data.bnf.fr/ark:/12148/cb136023289">BnF data</a></span></span></li><li><span class="uid"><a rel="nofollow" class="external text" href="https://id.ndl.go.jp/auth/ndlna/00569065">Japan</a></span></li><li><span class="uid"><a rel="nofollow" class="external text" href="https://www.nli.org.il/en/authorities/987007548537305171">Israel</a></span></li></ul></div></td></tr></tbody></table></div></div><!--htdig_noindex--><div><div class="zim-footer">
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