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Available in 39 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-39" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">39 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D8%AA%D9%87%D8%A7%D8%AA%D9%81" title="تهاتف – Arabic" lang="ar" hreflang="ar" data-title="تهاتف" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-az mw-list-item"><a href="https://az.wikipedia.org/wiki/Telefoniya" title="Telefoniya – Azerbaijani" lang="az" hreflang="az" data-title="Telefoniya" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%A2%D1%8D%D0%BB%D0%B5%D1%84%D0%BE%D0%BD%D0%BD%D0%B0%D1%8F_%D1%81%D1%83%D0%B2%D1%8F%D0%B7%D1%8C" title="Тэлефонная сувязь – Belarusian" lang="be" hreflang="be" data-title="Тэлефонная сувязь" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%A2%D0%B5%D0%BB%D0%B5%D1%84%D0%BE%D0%BD%D0%B8%D1%8F" title="Телефония – Bulgarian" lang="bg" hreflang="bg" data-title="Телефония" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-bs mw-list-item"><a href="https://bs.wikipedia.org/wiki/Telefonija" title="Telefonija – Bosnian" lang="bs" hreflang="bs" data-title="Telefonija" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Telefonie" title="Telefonie – Czech" lang="cs" hreflang="cs" data-title="Telefonie" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Telefoni" title="Telefoni – Danish" lang="da" hreflang="da" data-title="Telefoni" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Telefonie" title="Telefonie – German" lang="de" hreflang="de" data-title="Telefonie" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Telefonside" title="Telefonside – Estonian" lang="et" hreflang="et" data-title="Telefonside" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%A4%CE%B7%CE%BB%CE%B5%CF%86%CF%89%CE%BD%CE%AF%CE%B1" title="Τηλεφωνία – Greek" lang="el" hreflang="el" data-title="Τηλεφωνία" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Telefonio" title="Telefonio – Esperanto" lang="eo" hreflang="eo" data-title="Telefonio" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D9%85%DA%A9%D8%A7%D9%84%D9%85%D9%87_%D8%B1%D8%A7%D9%87_%D8%AF%D9%88%D8%B1" title="مکالمه راه دور – Persian" lang="fa" hreflang="fa" data-title="مکالمه راه دور" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/T%C3%A9l%C3%A9phonie" title="Téléphonie – French" lang="fr" hreflang="fr" data-title="Téléphonie" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D5%80%D5%A5%D5%BC%D5%A1%D5%AD%D5%B8%D5%BD%D5%B8%D6%82%D5%A9%D5%B5%D5%B8%D6%82%D5%B6" title="Հեռախոսություն – Armenian" lang="hy" hreflang="hy" data-title="Հեռախոսություն" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Telefonija" title="Telefonija – Croatian" lang="hr" hreflang="hr" data-title="Telefonija" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Telefonia" title="Telefonia – Italian" lang="it" hreflang="it" data-title="Telefonia" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%98%D7%9C%D7%A4%D7%95%D7%A0%D7%99%D7%94" title="טלפוניה – Hebrew" lang="he" hreflang="he" data-title="טלפוניה" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%A2%D0%B5%D0%BB%D0%B5%D1%84%D0%BE%D0%BD%D0%B8%D1%8F" title="Телефония – Kazakh" lang="kk" hreflang="kk" data-title="Телефония" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target"><span>Қазақша</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Telefonija" title="Telefonija – Latvian" lang="lv" hreflang="lv" data-title="Telefonija" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target"><span>Latviešu</span></a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/Telefonija" title="Telefonija – Lithuanian" lang="lt" hreflang="lt" data-title="Telefonija" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-li mw-list-item"><a href="https://li.wikipedia.org/wiki/Tillefonie" title="Tillefonie – Limburgish" lang="li" hreflang="li" data-title="Tillefonie" data-language-autonym="Limburgs" data-language-local-name="Limburgish" class="interlanguage-link-target"><span>Limburgs</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%9F%E0%B5%86%E0%B4%B2%E0%B4%BF%E0%B4%AB%E0%B5%8B%E0%B4%A3%E0%B4%BF" title="ടെലിഫോണി – Malayalam" lang="ml" hreflang="ml" data-title="ടെലിഫോണി" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Telefonie" title="Telefonie – Dutch" lang="nl" hreflang="nl" data-title="Telefonie" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E9%9B%BB%E8%A9%B1" title="電話 – Japanese" lang="ja" hreflang="ja" data-title="電話" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Telefoni" title="Telefoni – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Telefoni" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-uz mw-list-item"><a href="https://uz.wikipedia.org/wiki/Telefoniya" title="Telefoniya – Uzbek" lang="uz" hreflang="uz" data-title="Telefoniya" data-language-autonym="Oʻzbekcha / ўзбекча" data-language-local-name="Uzbek" class="interlanguage-link-target"><span>Oʻzbekcha / ўзбекча</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Telefonia" title="Telefonia – Polish" lang="pl" hreflang="pl" data-title="Telefonia" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Telefonia" title="Telefonia – Portuguese" lang="pt" hreflang="pt" data-title="Telefonia" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%A2%D0%B5%D0%BB%D0%B5%D1%84%D0%BE%D0%BD%D0%B8%D1%8F" title="Телефония – Russian" lang="ru" hreflang="ru" data-title="Телефония" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-stq mw-list-item"><a href="https://stq.wikipedia.org/wiki/Telefonie" title="Telefonie – Saterland Frisian" lang="stq" hreflang="stq" data-title="Telefonie" data-language-autonym="Seeltersk" data-language-local-name="Saterland Frisian" class="interlanguage-link-target"><span>Seeltersk</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Telef%C3%B3nia" title="Telefónia – Slovak" lang="sk" hreflang="sk" data-title="Telefónia" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/%D0%A2%D0%B5%D0%BB%D0%B5%D1%84%D0%BE%D0%BD%D0%B8%D1%98%D0%B0" title="Телефонија – Serbian" lang="sr" hreflang="sr" data-title="Телефонија" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-kab mw-list-item"><a href="https://kab.wikipedia.org/wiki/Tamsawla" title="Tamsawla – Kabyle" lang="kab" hreflang="kab" data-title="Tamsawla" data-language-autonym="Taqbaylit" data-language-local-name="Kabyle" class="interlanguage-link-target"><span>Taqbaylit</span></a></li><li class="interlanguage-link interwiki-te mw-list-item"><a href="https://te.wikipedia.org/wiki/%E0%B0%9F%E0%B1%86%E0%B0%B2%E0%B0%BF%E0%B0%AB%E0%B1%8B%E0%B0%A8%E0%B1%80" title="టెలిఫోనీ – Telugu" lang="te" hreflang="te" data-title="టెలిఫోనీ" data-language-autonym="తెలుగు" data-language-local-name="Telugu" class="interlanguage-link-target"><span>తెలుగు</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B8%A3%E0%B8%B0%E0%B8%9A%E0%B8%9A%E0%B9%82%E0%B8%97%E0%B8%A3%E0%B8%A8%E0%B8%B1%E0%B8%9E%E0%B8%97%E0%B9%8C" title="ระบบโทรศัพท์ – Thai" lang="th" hreflang="th" data-title="ระบบโทรศัพท์" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Telefonculuk" title="Telefonculuk – Turkish" lang="tr" hreflang="tr" data-title="Telefonculuk" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%A2%D0%B5%D0%BB%D0%B5%D1%84%D0%BE%D0%BD%D0%BD%D0%B8%D0%B9_%D0%B7%D0%B2%27%D1%8F%D0%B7%D0%BE%D0%BA" title="Телефонний зв'язок – Ukrainian" lang="uk" hreflang="uk" data-title="Телефонний зв'язок" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-ur mw-list-item"><a href="https://ur.wikipedia.org/wiki/%D9%B9%DB%8C%D9%84%DB%8C_%D9%81%D9%88%D9%86%DB%8C" title="ٹیلی فونی – Urdu" lang="ur" hreflang="ur" data-title="ٹیلی فونی" data-language-autonym="اردو" data-language-local-name="Urdu" class="interlanguage-link-target"><span>اردو</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E7%94%B5%E8%AF%9D%E5%AD%A6" title="电话学 – Chinese" lang="zh" hreflang="zh" data-title="电话学" data-language-autonym="中文" data-language-local-name="Chinese" 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<div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Field of telecommunication services</div> <p><b>Telephony</b> (<span class="rt-commentedText nowrap"><span class="IPA nopopups noexcerpt" lang="en-fonipa"><a href="/wiki/Help:IPA/English" title="Help:IPA/English">/<span style="border-bottom:1px dotted"><span title="'t' in 'tie'">t</span><span title="/ə/: 'a' in 'about'">ə</span><span title="/ˈ/: primary stress follows">ˈ</span><span title="'l' in 'lie'">l</span><span title="/ɛ/: 'e' in 'dress'">ɛ</span><span title="'f' in 'find'">f</span><span title="/ə/: 'a' in 'about'">ə</span><span title="'n' in 'nigh'">n</span><span title="/i/: 'y' in 'happy'">i</span></span>/</a></span></span> <a href="/wiki/Help:Pronunciation_respelling_key" title="Help:Pronunciation respelling key"><i title="English pronunciation respelling">tə-<span style="font-size:90%">LEF</span>-ə-nee</i></a>) is the field of technology involving the development, application, and deployment of <a href="/wiki/Telecommunications_service" title="Telecommunications service">telecommunications services</a> for the purpose of electronic transmission of voice, <a href="/wiki/Fax" title="Fax">fax</a>, or <a href="/wiki/Data" title="Data">data</a>, between distant parties. The history of telephony is intimately linked to the invention and development of the <a href="/wiki/Telephone" title="Telephone">telephone</a>. </p><p>Telephony is commonly referred to as the construction or operation of telephones and telephonic systems and as a system of telecommunications in which telephonic equipment is employed in the transmission of speech or other sound between points, with or without the use of wires.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> The term is also used frequently to refer to <a href="/wiki/Computer_hardware" title="Computer hardware">computer hardware</a>, <a href="/wiki/Software" title="Software">software</a>, and <a href="/wiki/Computer_network" title="Computer network">computer network</a> systems, that perform functions traditionally performed by telephone equipment. In this context the technology is specifically referred to as Internet telephony, or <a href="/wiki/Voice_over_Internet_Protocol" class="mw-redirect" title="Voice over Internet Protocol">voice over Internet Protocol</a> (VoIP). </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Overview">Overview</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Telephony&action=edit&section=1" title="Edit section: Overview"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The first telephones were connected directly in pairs. Each user had a separate telephone wired to each locations to be reached. This quickly became inconvenient and unmanageable when users wanted to communicate with more than a few people. The invention of the <a href="/wiki/Telephone_exchange" title="Telephone exchange">telephone exchange</a> provided the solution for establishing telephone connections with any other telephone in service in the local area. Each telephone was connected to the exchange at first with one wire, later one wire pair, the <a href="/wiki/Local_loop" title="Local loop">local loop</a>. Nearby exchanges in other service areas were connected with <a href="/wiki/Trunking" title="Trunking">trunk lines</a>, and long-distance service could be established by relaying the calls through multiple exchanges. </p><p>Initially, exchange <a href="/wiki/Telephone_switchboard" title="Telephone switchboard">switchboards</a> were manually operated by an attendant, commonly referred to as the "<a href="/wiki/Switchboard_operator" title="Switchboard operator">switchboard operator</a>". When a customer cranked a handle on the telephone, it activated an indicator on the board in front of the operator, who would in response plug the operator headset into that jack and offer service. The caller had to ask for the called party by name, later by number, and the operator connected one end of a circuit into the called party jack to alert them. If the called station answered, the operator disconnected their headset and completed the station-to-station circuit. Trunk calls were made with the assistance of other operators at other exchangers in the network. </p><p>Until the 1970s, most telephones were permanently wired to the telephone line installed at customer premises. Later, conversion to installation of jacks that terminated the <a href="/wiki/On-premises_wiring" title="On-premises wiring">inside wiring</a> permitted simple exchange of telephone sets with <a href="/wiki/Telephone_plugs" class="mw-redirect" title="Telephone plugs">telephone plugs</a> and allowed portability of the set to multiple locations in the premises where jacks were installed. The inside wiring to all jacks was connected in one place to the <a href="/wiki/Drop_(telecommunication)" title="Drop (telecommunication)">wire drop</a> which connects the building to a cable. Cables usually bring a large number of drop wires from all over a district <a href="/wiki/Access_network" title="Access network">access network</a> to one wire center or telephone exchange. When a telephone user wants to make a <a href="/wiki/Telephone_call" title="Telephone call">telephone call</a>, equipment at the exchange examines the dialed <a href="/wiki/Telephone_number" title="Telephone number">telephone number</a> and connects that <a href="/wiki/Telephone_line" title="Telephone line">telephone line</a> to another in the same wire center, or to a trunk to a distant exchange. Most of the exchanges in the world are interconnected through a system of larger switching systems, forming the <a href="/wiki/Public_switched_telephone_network" title="Public switched telephone network">public switched telephone network</a> (PSTN). </p><p>In the second half of the 20th century, fax and data became important secondary applications of the network created to carry voices, and late in the century, parts of the network were upgraded with <a href="/wiki/ISDN" title="ISDN">ISDN</a> and <a href="/wiki/DSL" class="mw-redirect" title="DSL">DSL</a> to improve handling of such traffic. </p><p>Today, telephony uses digital technology (<a href="/wiki/Digital_telephony" class="mw-redirect" title="Digital telephony">digital telephony</a>) in the provisioning of telephone services and systems. Telephone calls can be provided digitally, but may be restricted to cases in which the <a href="/wiki/Last_mile_(telecommunications)" title="Last mile (telecommunications)">last mile</a> is digital, or where the conversion between <a href="/wiki/Digital_signal_(signal_processing)" title="Digital signal (signal processing)">digital</a> and <a href="/wiki/Analog_signal" title="Analog signal">analog signals</a> takes place inside the telephone. This advancement has reduced costs in communication, and improved the quality of voice services. The first implementation of this, <a href="/wiki/Integrated_Services_Digital_Network" class="mw-redirect" title="Integrated Services Digital Network">ISDN</a>, permitted all data transport from end-to-end speedily over telephone lines.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> This service was later made much less important due to the ability to provide digital services based on the <a href="/wiki/Internet_protocol_suite" title="Internet protocol suite">Internet protocol suite</a>.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p><p>Since the advent of personal computer technology in the 1980s, <a href="/wiki/Computer_telephony_integration" title="Computer telephony integration">computer telephony integration</a> (CTI) has progressively provided more sophisticated telephony services, initiated and controlled by the computer, such as making and receiving voice, fax, and data calls with <a href="/wiki/Telephone_directory" title="Telephone directory">telephone directory</a> services and <a href="/wiki/Caller_identification" class="mw-redirect" title="Caller identification">caller identification</a>. The integration of telephony software and computer systems is a major development in the evolution of office automation. The term is used in describing the computerized services of call centers, such as those that direct your phone call to the right department at a business you're calling. It is also sometimes used for the ability to use your personal computer to initiate and manage phone calls (in which case you can think of your computer as your personal call center).<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> </p> <div class="mw-heading mw-heading2"><h2 id="Digital_telephony"><span class="anchor" id="Digital_telephony"></span> Digital telephony</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Telephony&action=edit&section=2" title="Edit section: Digital telephony"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><b>Digital telephony</b> is the use of <a href="/wiki/Digital_electronics" title="Digital electronics">digital electronics</a> in the operation and provisioning of telephony systems and services. Since the late 20th century, a <a href="/wiki/Digital_electronics" title="Digital electronics">digital</a> <a href="/wiki/Core_network" class="mw-redirect" title="Core network">core network</a> has replaced the traditional <a href="/wiki/Analog_transmission" title="Analog transmission">analog transmission</a> and signaling systems, and much of the <a href="/wiki/Access_network" title="Access network">access network</a> has also been digitized. </p><p>Starting with the development of <a href="/wiki/Transistor" title="Transistor">transistor</a> technology, originating from <a href="/wiki/Bell_Telephone_Laboratories" class="mw-redirect" title="Bell Telephone Laboratories">Bell Telephone Laboratories</a> in 1947, to <a href="/wiki/Amplifier" title="Amplifier">amplification</a> and <a href="/wiki/Switching_circuit" class="mw-redirect" title="Switching circuit">switching circuits</a> in the 1950s, the <a href="/wiki/Public_switched_telephone_network" title="Public switched telephone network">public switched telephone network</a> (PSTN) has gradually moved towards <a href="/wiki/Solid-state_electronics" title="Solid-state electronics">solid-state electronics</a> and <a href="/wiki/Automation" title="Automation">automation</a>. Following the development of <a href="/wiki/Computer" title="Computer">computer</a>-based <a href="/wiki/Electronic_switching_system" title="Electronic switching system">electronic switching systems</a> incorporating <a href="/wiki/Metal%E2%80%93oxide%E2%80%93semiconductor" class="mw-redirect" title="Metal–oxide–semiconductor">metal–oxide–semiconductor</a> (MOS) and <a href="/wiki/Pulse-code_modulation" title="Pulse-code modulation">pulse-code modulation</a> (PCM) technologies, the PSTN gradually evolved towards the <a href="/wiki/Digital_signal" title="Digital signal">digitization of signaling</a> and <a href="/wiki/Digital_audio" title="Digital audio">audio transmissions</a>. Digital telephony has since dramatically improved the capacity, quality and cost of the network. Digitization allows <a href="/wiki/Wideband_voice" class="mw-redirect" title="Wideband voice">wideband voice</a> on the same channel, with improved quality of a wider analog voice channel. </p> <div class="mw-heading mw-heading3"><h3 id="History">History</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Telephony&action=edit&section=3" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The earliest end-to-end analog telephone networks to be modified and upgraded to transmission networks with <a href="/wiki/Digital_Signal_1" title="Digital Signal 1">Digital Signal 1</a> (DS1/T1) carrier systems date back to the early 1960s. They were designed to support the basic 3 kHz voice channel by sampling the bandwidth-limited analog voice signal and encoding using <a href="/wiki/Pulse-code_modulation" title="Pulse-code modulation">pulse-code modulation</a> (PCM). Early PCM <a href="/wiki/Codec" title="Codec">codec</a>-<a href="/wiki/Filter_(signal_processing)" title="Filter (signal processing)">filters</a> were implemented as passive <a href="/wiki/Resistor" title="Resistor">resistor</a>–<a href="/wiki/Capacitor" title="Capacitor">capacitor</a>–<a href="/wiki/Inductor" title="Inductor">inductor</a> filter circuits, with <a href="/wiki/Analog-to-digital" class="mw-redirect" title="Analog-to-digital">analog-to-digital</a> conversion (for digitizing voices) and <a href="/wiki/Digital-to-analog_conversion" class="mw-redirect" title="Digital-to-analog conversion">digital-to-analog conversion</a> (for reconstructing voices) handled by <a href="/wiki/Discrete_device" class="mw-redirect" title="Discrete device">discrete devices</a>. Early digital telephony was impractical due to the low performance and high costs of early PCM codec-filters.<sup id="cite_ref-Gibson26_5-0" class="reference"><a href="#cite_note-Gibson26-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Allstot_6-0" class="reference"><a href="#cite_note-Allstot-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>Practical <a href="/wiki/Digital_telecommunication" class="mw-redirect" title="Digital telecommunication">digital telecommunication</a> was enabled by the invention of the <a href="/wiki/Metal%E2%80%93oxide%E2%80%93semiconductor_field-effect_transistor" class="mw-redirect" title="Metal–oxide–semiconductor field-effect transistor">metal–oxide–semiconductor field-effect transistor</a> (MOSFET),<sup id="cite_ref-Colinge2005_7-0" class="reference"><a href="#cite_note-Colinge2005-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> which led to the rapid development and wide adoption of PCM digital telephony.<sup id="cite_ref-Allstot_6-1" class="reference"><a href="#cite_note-Allstot-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> In 1957, Frosch and Derick were able to manufacture the first silicon dioxide field effect transistors at Bell Labs, the first transistors in which drain and source were adjacent at the surface.<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> Subsequently, a team demonstrated a working <a href="/wiki/MOSFET" title="MOSFET">MOSFET</a> at Bell Labs 1960.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup><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> MOS technology was initially overlooked by Bell because they did not find it practical for analog telephone applications, before it was commercialized by <a href="/wiki/Fairchild_Semiconductor" title="Fairchild Semiconductor">Fairchild</a> and <a href="/wiki/RCA" title="RCA">RCA</a> for <a href="/wiki/Digital_electronics" title="Digital electronics">digital electronics</a> such as <a href="/wiki/Computers" class="mw-redirect" title="Computers">computers</a>.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Allstot_6-2" class="reference"><a href="#cite_note-Allstot-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>MOS technology eventually became practical for telephone applications with the MOS <a href="/wiki/Mixed-signal_integrated_circuit" title="Mixed-signal integrated circuit">mixed-signal integrated circuit</a>, which combines analog and <a href="/wiki/Digital_signal_processing" title="Digital signal processing">digital signal processing</a> on a single chip, developed by former Bell engineer <a href="/wiki/David_A._Hodges" title="David A. Hodges">David A. Hodges</a> with Paul R. Gray at <a href="/wiki/UC_Berkeley" class="mw-redirect" title="UC Berkeley">UC Berkeley</a> in the early 1970s.<sup id="cite_ref-Allstot_6-3" class="reference"><a href="#cite_note-Allstot-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> In 1974, Hodges and Gray worked with R.E. Suarez to develop MOS <a href="/wiki/Switched_capacitor" title="Switched capacitor">switched capacitor</a> (SC) circuit technology, which they used to develop a <a href="/wiki/Digital-to-analog_converter" title="Digital-to-analog converter">digital-to-analog converter</a> (DAC) chip, using <a href="/wiki/MOS_capacitor" class="mw-redirect" title="MOS capacitor">MOS capacitors</a> and MOSFET switches for data conversion.<sup id="cite_ref-Allstot_6-4" class="reference"><a href="#cite_note-Allstot-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> MOS <a href="/wiki/Analog-to-digital_converter" title="Analog-to-digital converter">analog-to-digital converter</a> (ADC) and DAC chips were commercialized by 1974.<sup id="cite_ref-US46_12-0" class="reference"><a href="#cite_note-US46-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p><p>MOS SC circuits led to the development of PCM codec-filter chips in the late 1970s.<sup id="cite_ref-Allstot_6-5" class="reference"><a href="#cite_note-Allstot-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Gibson26_5-1" class="reference"><a href="#cite_note-Gibson26-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> The <a href="/wiki/Silicon-gate" class="mw-redirect" title="Silicon-gate">silicon-gate</a> <a href="/wiki/CMOS" title="CMOS">CMOS</a> (complementary MOS) PCM codec-filter chip, developed by Hodges and W.C. Black in 1980,<sup id="cite_ref-Allstot_6-6" class="reference"><a href="#cite_note-Allstot-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> has since been the industry standard for digital telephony.<sup id="cite_ref-Allstot_6-7" class="reference"><a href="#cite_note-Allstot-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Gibson26_5-2" class="reference"><a href="#cite_note-Gibson26-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> By the 1990s, <a href="/wiki/Telecommunication_network" class="mw-redirect" title="Telecommunication network">telecommunication networks</a> such as the <a href="/wiki/Public_switched_telephone_network" title="Public switched telephone network">public switched telephone network</a> (PSTN) had been largely digitized with <a href="/wiki/Very-large-scale_integration" title="Very-large-scale integration">very-large-scale integration</a> (VLSI) CMOS PCM codec-filters, widely used in <a href="/wiki/Electronic_switching_system" title="Electronic switching system">electronic switching systems</a> for <a href="/wiki/Telephone_exchanges" class="mw-redirect" title="Telephone exchanges">telephone exchanges</a>, <a href="/wiki/Private_branch_exchange" class="mw-redirect" title="Private branch exchange">private branch exchanges</a> (PBX) and <a href="/wiki/Key_telephone_system" class="mw-redirect" title="Key telephone system">key telephone systems</a> (KTS); user-end <a href="/wiki/Modems" class="mw-redirect" title="Modems">modems</a>; <a href="/wiki/Data_transmission" class="mw-redirect" title="Data transmission">data transmission</a> applications such as <a href="/wiki/Digital_loop_carrier" title="Digital loop carrier">digital loop carriers</a>, <a href="/wiki/Pair_gain" title="Pair gain">pair gain</a> <a href="/wiki/Multiplexers" class="mw-redirect" title="Multiplexers">multiplexers</a>, telephone <a href="/wiki/ADSL_loop_extender" title="ADSL loop extender">loop extenders</a>, <a href="/wiki/Integrated_services_digital_network" class="mw-redirect" title="Integrated services digital network">integrated services digital network</a> (ISDN) terminals, digital <a href="/wiki/Cordless_telephones" class="mw-redirect" title="Cordless telephones">cordless telephones</a> and digital <a href="/wiki/Cell_phones" class="mw-redirect" title="Cell phones">cell phones</a>; and applications such as <a href="/wiki/Speech_recognition" title="Speech recognition">speech recognition</a> equipment, voice <a href="/wiki/Data_storage" title="Data storage">data storage</a>, <a href="/wiki/Voice_mail" class="mw-redirect" title="Voice mail">voice mail</a> and digital tapeless <a href="/wiki/Answering_machines" class="mw-redirect" title="Answering machines">answering machines</a>.<sup id="cite_ref-Gibson26_5-3" class="reference"><a href="#cite_note-Gibson26-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> The bandwidth of digital telecommunication networks has been rapidly increasing at an exponential rate, as observed by <a href="/wiki/Edholm%27s_law" title="Edholm's law">Edholm's law</a>,<sup id="cite_ref-Cherry_13-0" class="reference"><a href="#cite_note-Cherry-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> largely driven by the <a href="/wiki/MOSFET_scaling" class="mw-redirect" title="MOSFET scaling">rapid scaling</a> and <a href="/wiki/Miniaturization" title="Miniaturization">miniaturization</a> of MOS technology.<sup id="cite_ref-Jindal_14-0" class="reference"><a href="#cite_note-Jindal-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Allstot_6-8" class="reference"><a href="#cite_note-Allstot-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>Uncompressed PCM <a href="/wiki/Digital_audio" title="Digital audio">digital audio</a> with <a href="/wiki/Audio_bit_depth" title="Audio bit depth">8-bit depth</a> and 8<span class="nowrap"> </span><a href="/wiki/KHz" class="mw-redirect" title="KHz">kHz</a> <a href="/wiki/Sample_rate" class="mw-redirect" title="Sample rate">sample rate</a> requires a <a href="/wiki/Bit_rate" title="Bit rate">bit rate</a> of 64<span class="nowrap"> </span><a href="/wiki/Kbit/s" class="mw-redirect" title="Kbit/s">kbit/s</a>, which was impractical for early digital telecommunication networks with limited <a href="/wiki/Network_bandwidth" class="mw-redirect" title="Network bandwidth">network bandwidth</a>. A solution to this issue was <a href="/wiki/Linear_predictive_coding" title="Linear predictive coding">linear predictive coding</a> (LPC), a <a href="/wiki/Speech_coding" title="Speech coding">speech coding</a> <a href="/wiki/Data_compression" title="Data compression">data compression</a> algorithm that was first proposed by <a href="/wiki/Fumitada_Itakura" title="Fumitada Itakura">Fumitada Itakura</a> of <a href="/wiki/Nagoya_University" title="Nagoya University">Nagoya University</a> and Shuzo Saito of <a href="/wiki/Nippon_Telegraph_and_Telephone" title="Nippon Telegraph and Telephone">Nippon Telegraph and Telephone</a> (NTT) in 1966. LPC was capable of <a href="/wiki/Audio_data_compression" class="mw-redirect" title="Audio data compression">audio data compression</a> down to 2.4<span class="nowrap"> </span>kbit/s, leading to the first successful real-time conversations over digital networks in the 1970s.<sup id="cite_ref-Gray_15-0" class="reference"><a href="#cite_note-Gray-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> LPC has since been the most widely used speech coding method.<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> Another <a href="/wiki/Audio_data_compression" class="mw-redirect" title="Audio data compression">audio data compression</a> method, a <a href="/wiki/Discrete_cosine_transform" title="Discrete cosine transform">discrete cosine transform</a> (DCT) algorithm called the <a href="/wiki/Modified_discrete_cosine_transform" title="Modified discrete cosine transform">modified discrete cosine transform</a> (MDCT), has been widely adopted for speech coding in <a href="/wiki/Voice-over-IP" class="mw-redirect" title="Voice-over-IP">voice-over-IP</a> (VoIP) applications since the late 1990s.<sup id="cite_ref-Schnell_17-0" class="reference"><a href="#cite_note-Schnell-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </p><p>The development of transmission methods such as <a href="/wiki/SONET" class="mw-redirect" title="SONET">SONET</a> and <a href="/wiki/Fiber_optic" class="mw-redirect" title="Fiber optic">fiber optic</a> transmission further advanced digital transmission. Although analog carrier systems existed that multiplexed multiple analog voice channels onto a single transmission medium, digital transmission allowed lower cost and more channels <a href="/wiki/Multiplexing" title="Multiplexing">multiplexed</a> on the transmission medium. Today the end instrument often remains analog but the analog signals are typically converted to <a href="/wiki/Digital_signal_(signal_processing)" title="Digital signal (signal processing)">digital signals</a> at the <a href="/wiki/Serving_area_interface" title="Serving area interface">serving area interface</a> (SAI), <a href="/wiki/Telephone_exchange" title="Telephone exchange">central office</a> (CO), or other aggregation point. <a href="/wiki/Digital_loop_carrier" title="Digital loop carrier">Digital loop carriers</a> (DLC) and <a href="/wiki/Fiber_to_the_x" title="Fiber to the x">fiber to the x</a> place the digital network ever closer to the customer premises, relegating the analog <a href="/wiki/Local_loop" title="Local loop">local loop</a> to legacy status. </p> <div class="mw-heading mw-heading2"><h2 id="IP_telephony">IP telephony</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Telephony&action=edit&section=4" title="Edit section: IP telephony"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Voice_over_IP" title="Voice over IP">Voice over IP</a></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Cisco7960G.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/60/Cisco7960G.jpg/220px-Cisco7960G.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/60/Cisco7960G.jpg/330px-Cisco7960G.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/60/Cisco7960G.jpg/440px-Cisco7960G.jpg 2x" data-file-width="1600" data-file-height="1200" /></a><figcaption>A commercial IP telephone, with keypad, control keys, and screen functions to perform configuration and user features.</figcaption></figure> <p>The field of technology available for telephony has broadened with the advent of new communication technologies. Telephony now includes the technologies of Internet services and mobile communication, including video conferencing. </p><p>The new technologies based on <a href="/wiki/Internet_Protocol" title="Internet Protocol">Internet Protocol</a> (IP) concepts are often referred to separately as voice over IP (VoIP) telephony, also commonly referred to as IP telephony or Internet telephony. Unlike traditional phone service, IP telephony service is relatively unregulated by government. In the United States, the <a href="/wiki/Federal_Communications_Commission" title="Federal Communications Commission">Federal Communications Commission</a> (FCC) regulates phone-to-phone connections, but says they do not plan to regulate connections between a phone user and an IP telephony service provider.<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> </p><p>A specialization of digital telephony, Internet Protocol (IP) telephony involves the application of digital networking technology that was the foundation to the <a href="/wiki/Internet" title="Internet">Internet</a> to create, transmit, and receive telecommunications sessions over <a href="/wiki/Computer_network" title="Computer network">computer networks</a>. Internet telephony is commonly known as <a href="/wiki/Voice_over_Internet_Protocol" class="mw-redirect" title="Voice over Internet Protocol">voice over Internet Protocol</a> (VoIP), reflecting the principle, but it has been referred with many other terms. VoIP has proven to be a <a href="/wiki/Disruptive_technology" class="mw-redirect" title="Disruptive technology">disruptive technology</a> that is rapidly replacing traditional telephone infrastructure technologies. As of January 2005, up to 10% of telephone subscribers in <a href="/wiki/Japan" title="Japan">Japan</a> and <a href="/wiki/South_Korea" title="South Korea">South Korea</a> have switched to this digital telephone service. A January 2005 <i><a href="/wiki/Newsweek" title="Newsweek">Newsweek</a></i> article suggested that Internet telephony may be "the next big thing".<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> As of 2006, many VoIP companies offer service to <a href="/wiki/Consumer" title="Consumer">consumers</a> and <a href="/wiki/Business" title="Business">businesses</a>.<sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Manual_of_Style/Dates_and_numbers#Chronological_items" title="Wikipedia:Manual of Style/Dates and numbers"><span title="The date of the event predicted near this tag has passed. (September 2015)">needs update</span></a></i>]</sup> </p><p>IP telephony uses an Internet connection and hardware <a href="/wiki/IP_phone" class="mw-redirect" title="IP phone">IP phones</a>, analog telephone adapters, or <a href="/wiki/Softphone" title="Softphone">softphone</a> computer applications to transmit conversations encoded as <a href="/wiki/Data_packet" class="mw-redirect" title="Data packet">data packets</a>. In addition to replacing plain old telephone service (POTS), IP telephony services compete with <a href="/wiki/Mobile_phone" title="Mobile phone">mobile phone</a> services by offering free or lower cost connections via <a href="/wiki/WiFi" class="mw-redirect" title="WiFi">WiFi</a> <a href="/wiki/Hotspot_(Wi-Fi)" class="mw-redirect" title="Hotspot (Wi-Fi)">hotspots</a>. VoIP is also used on private networks which may or may not have a connection to the global telephone network. </p> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Fixed_telephone_lines_per_100_inhabitants_1997-2007_ITU.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/2d/Fixed_telephone_lines_per_100_inhabitants_1997-2007_ITU.png/300px-Fixed_telephone_lines_per_100_inhabitants_1997-2007_ITU.png" decoding="async" width="300" height="254" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/2d/Fixed_telephone_lines_per_100_inhabitants_1997-2007_ITU.png/450px-Fixed_telephone_lines_per_100_inhabitants_1997-2007_ITU.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/2d/Fixed_telephone_lines_per_100_inhabitants_1997-2007_ITU.png/600px-Fixed_telephone_lines_per_100_inhabitants_1997-2007_ITU.png 2x" data-file-width="956" data-file-height="810" /></a><figcaption>Fixed telephone lines per 100 inhabitants 1997–2007</figcaption></figure> <div class="mw-heading mw-heading2"><h2 id="Social_impact_research">Social impact research</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Telephony&action=edit&section=5" title="Edit section: Social impact research"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Direct person-to-person communication includes non-verbal cues expressed in facial and other bodily articulation, that cannot be transmitted in traditional voice telephony. <a href="/wiki/Video_telephony" class="mw-redirect" title="Video telephony">Video telephony</a> restores such interactions to varying degrees. Social Context Cues Theory is a model to measure the success of different types of communication in maintaining the non-verbal cues present in face-to-face interactions. The research examines many different cues, such as the physical context, different facial expressions, body movements, tone of voice, touch and smell. </p><p>Various communication cues are lost with the usage of the telephone. The communicating parties are not able to identify the body movements, and lack touch and smell. Although this diminished ability to identify social cues is well known, Wiesenfeld, Raghuram, and Garud point out that there is a value and efficiency to the type of communication for different tasks.<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> They examine work places in which different types of communication, such as the telephone, are more useful than face-to-face interaction. </p><p>The expansion of communication to mobile telephone service has created a different filter of the social cues than the <a href="/wiki/Land-line" class="mw-redirect" title="Land-line">land-line</a> telephone. The use of instant messaging, such as <i>texting</i>, on mobile telephones has created a sense of community.<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> In <i>The Social Construction of Mobile Telephony</i> it is suggested that each phone call and text message is more than an attempt to converse. Instead, it is a gesture which maintains the social network between family and friends. Although there is a loss of certain social cues through telephones, mobile phones bring new forms of expression of different cues that are understood by different audiences. New language additives attempt to compensate for the inherent lack of non-physical interaction. </p><p>Another social theory supported through telephony is the Media Dependency Theory. This theory concludes that people use media or a resource to attain certain goals. This theory states that there is a link between the media, audience, and the large social system.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> Telephones, depending on the person, help attain certain goals like accessing information, keeping in contact with others, sending quick communication, entertainment, etc. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Telephony&action=edit&section=6" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 0.9em;text-align:center}.mw-parser-output .side-box-imageright{padding:2px 0.9em 2px 0;text-align:center}@media(min-width:500px){.mw-parser-output .side-box-flex{display:flex;align-items:center}.mw-parser-output .side-box-text{flex:1;min-width:0}}@media(min-width:720px){.mw-parser-output .side-box{width:238px}.mw-parser-output .side-box-right{clear:right;float:right;margin-left:1em}.mw-parser-output .side-box-left{margin-right:1em}}</style><style data-mw-deduplicate="TemplateStyles:r1237033735">@media print{body.ns-0 .mw-parser-output .sistersitebox{display:none!important}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}</style><div class="side-box side-box-right plainlinks sistersitebox"><style data-mw-deduplicate="TemplateStyles:r1126788409">.mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0}</style> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/40px-Wiktionary-logo-en-v2.svg.png" decoding="async" width="40" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/60px-Wiktionary-logo-en-v2.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/80px-Wiktionary-logo-en-v2.svg.png 2x" data-file-width="512" data-file-height="512" /></span></span></div> <div class="side-box-text plainlist">Look up <i><b><a href="https://en.wiktionary.org/wiki/Special:Search/telephony" class="extiw" title="wiktionary:Special:Search/telephony">telephony</a></b></i> in Wiktionary, the free dictionary.</div></div> </div> <style data-mw-deduplicate="TemplateStyles:r1239009302">.mw-parser-output .portalbox{padding:0;margin:0.5em 0;display:table;box-sizing:border-box;max-width:175px;list-style:none}.mw-parser-output .portalborder{border:1px solid var(--border-color-base,#a2a9b1);padding:0.1em;background:var(--background-color-neutral-subtle,#f8f9fa)}.mw-parser-output .portalbox-entry{display:table-row;font-size:85%;line-height:110%;height:1.9em;font-style:italic;font-weight:bold}.mw-parser-output .portalbox-image{display:table-cell;padding:0.2em;vertical-align:middle;text-align:center}.mw-parser-output .portalbox-link{display:table-cell;padding:0.2em 0.2em 0.2em 0.3em;vertical-align:middle}@media(min-width:720px){.mw-parser-output .portalleft{clear:left;float:left;margin:0.5em 1em 0.5em 0}.mw-parser-output .portalright{clear:right;float:right;margin:0.5em 0 0.5em 1em}}</style><ul role="navigation" aria-label="Portals" class="noprint portalbox portalborder portalright"> <li class="portalbox-entry"><span class="portalbox-image"><span class="noviewer" typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Telecom-icon.svg/28px-Telecom-icon.svg.png" decoding="async" width="28" height="28" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Telecom-icon.svg/42px-Telecom-icon.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Telecom-icon.svg/56px-Telecom-icon.svg.png 2x" data-file-width="500" data-file-height="500" /></span></span></span><span class="portalbox-link"><a href="/wiki/Portal:Telecommunications" class="mw-redirect" title="Portal:Telecommunications">Telecommunications portal</a></span></li><li class="portalbox-entry"><span class="portalbox-image"><span class="noviewer" typeof="mw:File"><span><img alt="telephone icon" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b8/Telephone_icon_blue_gradient.svg/28px-Telephone_icon_blue_gradient.svg.png" decoding="async" width="28" height="28" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b8/Telephone_icon_blue_gradient.svg/42px-Telephone_icon_blue_gradient.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b8/Telephone_icon_blue_gradient.svg/56px-Telephone_icon_blue_gradient.svg.png 2x" data-file-width="722" data-file-height="722" /></span></span></span><span class="portalbox-link"><a href="/wiki/Portal:Telephones" title="Portal:Telephones">Telephones portal</a></span></li></ul> <ul><li><a href="/wiki/Extended_area_service" title="Extended area service">Extended area service</a></li> <li><a href="/wiki/History_of_the_telephone" title="History of the telephone">History of the telephone</a></li> <li><a href="/wiki/Invention_of_the_telephone" title="Invention of the telephone">Invention of the telephone</a></li> <li><a href="/wiki/List_of_telephony_terminology" title="List of telephony terminology">List of telephony terminology</a></li> <li><a href="/wiki/Stimulus_protocol" title="Stimulus protocol">Stimulus protocol</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Telephony&action=edit&section=7" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://dictionary.reference.com/browse/telephony">Dictionary.com</a> Telephony Definition</span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.communicationsmuseum.org.uk/emuseum/electronicswitching/digital/isdn/">"The Communications Museum Trust - eMuseum - History of Digital Switching -ISDN"</a>. <i>www.communicationsmuseum.org.uk</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2022-08-25</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.communicationsmuseum.org.uk&rft.atitle=The+Communications+Museum+Trust+-+eMuseum+-+History+of+Digital+Switching+-ISDN&rft_id=https%3A%2F%2Fwww.communicationsmuseum.org.uk%2Femuseum%2Felectronicswitching%2Fdigital%2Fisdn%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATelephony" class="Z3988"></span></span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://ingeniotech.co.uk/isdn-telephones-decline/">"Why ISDN telephones are in decline - Sussex, Surrey, Brighton | Ingenio"</a>. <i>ingeniotech.co.uk</i>. 2022-03-07<span class="reference-accessdate">. Retrieved <span class="nowrap">2022-08-25</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=ingeniotech.co.uk&rft.atitle=Why+ISDN+telephones+are+in+decline+-+Sussex%2C+Surrey%2C+Brighton+%7C+Ingenio&rft.date=2022-03-07&rft_id=https%3A%2F%2Fingeniotech.co.uk%2Fisdn-telephones-decline%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATelephony" class="Z3988"></span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://searchnetworking.techtarget.com/definition/CTI">What is CTI?</a> TechTarget</span> </li> <li id="cite_note-Gibson26-5"><span class="mw-cite-backlink">^ <a href="#cite_ref-Gibson26_5-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Gibson26_5-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Gibson26_5-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Gibson26_5-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFFloydHillman2018" class="citation book cs1">Floyd, Michael D.; Hillman, Garth D. 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(2016). "Switched Capacitor Filters". In Maloberti, Franco; Davies, Anthony C. (eds.). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20210930151716/https://ieee-cas.org/sites/default/files/a_short_history_of_circuits_and_systems-_ebook-_web.pdf"><i>A Short History of Circuits and Systems: From Green, Mobile, Pervasive Networking to Big Data Computing</i></a> <span class="cs1-format">(PDF)</span>. <a href="/wiki/IEEE_Circuits_and_Systems_Society" class="mw-redirect" title="IEEE Circuits and Systems Society">IEEE Circuits and Systems Society</a>. pp. 105–110. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9788793609860" title="Special:BookSources/9788793609860"><bdi>9788793609860</bdi></a>. Archived from <a rel="nofollow" class="external text" href="https://ieee-cas.org/sites/default/files/a_short_history_of_circuits_and_systems-_ebook-_web.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 2021-09-30<span class="reference-accessdate">. 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.navbox{display:none!important}}</style></div><div role="navigation" class="navbox" aria-labelledby="Telephony" style="padding:3px"><table class="nowraplinks mw-collapsible uncollapsed navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Telephony" title="Template:Telephony"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Telephony" title="Template talk:Telephony"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Telephony" title="Special:EditPage/Template:Telephony"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Telephony" style="font-size:114%;margin:0 4em"><a class="mw-selflink selflink">Telephony</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Types</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="/wiki/Landline" title="Landline">Landline</a></li> <li><a href="/wiki/Cable_telephony" title="Cable telephony">Cable telephony</a></li> <li><a href="/wiki/Mobile_phone" title="Mobile phone">Mobile phone</a></li> <li><a href="/wiki/Satellite_phone" title="Satellite phone">Satellite phone</a></li> <li><a href="/wiki/Photophone" title="Photophone">Photophone</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Accessories</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="/wiki/Answering_machine" title="Answering machine">Answering machine</a></li> <li><a href="/wiki/Caller_ID" title="Caller ID">Caller ID</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Connectivity</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="/wiki/Cable_protection_system" title="Cable protection system">Cable protection system</a></li> <li><a href="/wiki/Communications_satellite" title="Communications satellite">Communications satellites</a></li> <li><a href="/wiki/Fiber-optic_communication" title="Fiber-optic communication">Fibre-optical</a></li> <li><a href="/wiki/Free-space_optical_communication" title="Free-space optical communication">Free-space optical</a></li> <li><a href="/wiki/Integrated_Services_Digital_Network" class="mw-redirect" title="Integrated Services Digital Network">ISDN</a></li> <li><a href="/wiki/Mobile_phone_signal" title="Mobile phone signal">Mobile phone signal</a></li> <li><a href="/wiki/Plain_old_telephone_service" title="Plain old telephone service">POTS</a></li> <li><a href="/wiki/Public_switched_telephone_network" title="Public switched telephone network">PSTN</a></li> <li><a href="/wiki/Submarine_communications_cable" title="Submarine communications cable">Submarine cables</a></li> <li><a href="/wiki/Voice_over_IP" title="Voice over IP">VoIP</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Calls</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="/wiki/Missed_call" title="Missed call">Missed call</a></li> <li><a href="/wiki/Misdialed_call" title="Misdialed call">Misdialed call</a></li> <li><a href="/wiki/Nuisance_call" title="Nuisance call">Nuisance call</a></li> <li><a href="/wiki/Phone_tag" title="Phone tag">Phone tag</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Applications</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="/wiki/Fax" title="Fax">Fax transmission</a></li> <li><a href="/wiki/Telephone_call" title="Telephone call">Telephone calls</a></li> <li><a href="/wiki/Telephone_newspaper" title="Telephone newspaper">Telephone newspapers</a></li> <li><a href="/wiki/Th%C3%A9%C3%A2trophone" title="Théâtrophone">Théâtrophone</a></li> <li><a href="/wiki/Videotelephony" title="Videotelephony">Video calls</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div><span class="nowrap"><span class="noviewer" typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Telecom-icon.svg/28px-Telecom-icon.svg.png" decoding="async" width="28" height="28" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Telecom-icon.svg/42px-Telecom-icon.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Telecom-icon.svg/56px-Telecom-icon.svg.png 2x" data-file-width="500" data-file-height="500" /></span></span> </span><a href="/wiki/Portal:Telecommunication" title="Portal:Telecommunication">Telecommunication portal</a> <span class="nowrap"><span class="noviewer" typeof="mw:File"><span><img alt="telephone icon" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b8/Telephone_icon_blue_gradient.svg/28px-Telephone_icon_blue_gradient.svg.png" decoding="async" width="28" height="28" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b8/Telephone_icon_blue_gradient.svg/42px-Telephone_icon_blue_gradient.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b8/Telephone_icon_blue_gradient.svg/56px-Telephone_icon_blue_gradient.svg.png 2x" data-file-width="722" data-file-height="722" /></span></span> </span><a href="/wiki/Portal:Telephones" title="Portal:Telephones">Telephones portal</a></div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Telecommunications" 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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Telecommunications" title="Template:Telecommunications"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Telecommunications" title="Template talk:Telecommunications"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Telecommunications" title="Special:EditPage/Template:Telecommunications"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Telecommunications" style="font-size:114%;margin:0 4em"><a href="/wiki/Telecommunications" title="Telecommunications">Telecommunications</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/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="/wiki/Beacon#For_defensive_communications" title="Beacon">Beacon</a></li> <li><a href="/wiki/History_of_broadcasting" title="History of broadcasting">Broadcasting</a></li> <li><a href="/wiki/Cable_protection_system" title="Cable protection system">Cable protection system</a></li> <li><a href="/wiki/Cable_television" title="Cable television">Cable TV</a></li> <li><a href="/wiki/Communications_satellite#History" title="Communications satellite">Communications satellite</a></li> <li><a href="/wiki/Computer_network#History" title="Computer network">Computer network</a></li> <li><a href="/wiki/Data_compression" title="Data compression">Data compression</a> <ul><li><a href="/wiki/Audio_coding_format" title="Audio coding format">audio</a></li> <li><a href="/wiki/Discrete_cosine_transform" title="Discrete cosine transform">DCT</a></li> <li><a href="/wiki/Image_compression" title="Image compression">image</a></li> <li><a href="/wiki/Video_coding_format" title="Video coding format">video</a></li></ul></li> <li><a href="/wiki/Digital_media" title="Digital media">Digital media</a> <ul><li><a href="/wiki/Internet_video" title="Internet video">Internet video</a></li> <li><a href="/wiki/Online_video_platform" title="Online video platform">online video platform</a></li> <li><a href="/wiki/Social_media" title="Social media">social media</a></li> <li><a href="/wiki/Streaming_media" title="Streaming media">streaming</a></li></ul></li> <li><a href="/wiki/Drums_in_communication" title="Drums in communication">Drums</a></li> <li><a href="/wiki/Edholm%27s_law" title="Edholm's law">Edholm's law</a></li> <li><a href="/wiki/Electrical_telegraph#History" title="Electrical telegraph">Electrical telegraph</a></li> <li><a href="/wiki/Fax#History" title="Fax">Fax</a></li> <li><a href="/wiki/Heliograph#History" title="Heliograph">Heliographs</a></li> <li><a href="/wiki/Hydraulic_telegraph#Greek_hydraulic_semaphore_system" title="Hydraulic telegraph">Hydraulic telegraph</a></li> <li><a href="/wiki/Information_Age" title="Information Age">Information Age</a></li> <li><a href="/wiki/Information_revolution" class="mw-redirect" title="Information revolution">Information revolution</a></li> <li><a href="/wiki/History_of_the_Internet" title="History of the Internet">Internet</a></li> <li><a href="/wiki/Mass_media#History" title="Mass media">Mass media</a></li> <li><a href="/wiki/History_of_mobile_phones" title="History of mobile phones">Mobile phone</a> <ul><li><a href="/wiki/Smartphone" title="Smartphone">Smartphone</a></li></ul></li> <li><a href="/wiki/Optical_communication" title="Optical communication">Optical telecommunication</a></li> <li><a href="/wiki/Optical_telegraph" title="Optical telegraph">Optical telegraphy</a></li> <li><a href="/wiki/Pager" title="Pager">Pager</a></li> <li><a href="/wiki/Photophone" title="Photophone">Photophone</a></li> <li><a href="/wiki/History_of_prepaid_mobile_phones" title="History of prepaid mobile phones">Prepaid mobile phone</a></li> <li><a href="/wiki/History_of_radio" title="History of radio">Radio</a></li> <li><a href="/wiki/Radiotelephone" title="Radiotelephone">Radiotelephone</a></li> <li><a href="/wiki/Communications_satellite" title="Communications satellite">Satellite communications</a></li> <li><a href="/wiki/Semaphore" title="Semaphore">Semaphore</a> <ul><li><a href="/wiki/Phryctoria" title="Phryctoria">Phryctoria</a></li></ul></li> <li><a href="/wiki/Semiconductor" title="Semiconductor">Semiconductor</a> <ul><li><a href="/wiki/Semiconductor_device" title="Semiconductor device">device</a></li> <li><a href="/wiki/MOSFET" title="MOSFET">MOSFET</a></li> <li><a href="/wiki/History_of_the_transistor" title="History of the transistor">transistor</a></li></ul></li> <li><a href="/wiki/Smoke_signal" title="Smoke signal">Smoke signals</a></li> <li><a href="/wiki/History_of_telecommunication" title="History of telecommunication">Telecommunications history</a></li> <li><a href="/wiki/Telautograph" title="Telautograph">Telautograph</a></li> <li><a href="/wiki/Telegraphy" title="Telegraphy">Telegraphy</a></li> <li><a href="/wiki/Teleprinter" title="Teleprinter">Teleprinter</a> (teletype)</li> <li><a href="/wiki/History_of_the_telephone" title="History of the telephone">Telephone</a></li> <li><i><a href="/wiki/The_Telephone_Cases" title="The Telephone Cases">The Telephone Cases</a></i></li> <li><a href="/wiki/History_of_television" title="History of television">Television</a> <ul><li><a href="/wiki/Digital_television" title="Digital television">digital</a></li> <li><a href="/wiki/Streaming_television" title="Streaming television">streaming</a></li></ul></li> <li><a href="/wiki/Submarine_communications_cable#Early_history:_telegraph_and_coaxial_cables" title="Submarine communications cable">Undersea telegraph line</a></li> <li><a href="/wiki/History_of_videotelephony" title="History of videotelephony">Videotelephony</a></li> <li><a href="/wiki/Whistled_language" title="Whistled language">Whistled language</a></li> <li><a href="/wiki/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="/wiki/Nasir_Ahmed_(engineer)" title="Nasir Ahmed (engineer)">Nasir Ahmed</a></li> <li><a href="/wiki/Edwin_Howard_Armstrong" title="Edwin Howard Armstrong">Edwin Howard Armstrong</a></li> <li><a href="/wiki/Mohamed_M._Atalla" title="Mohamed M. Atalla">Mohamed M. Atalla</a></li> <li><a href="/wiki/John_Logie_Baird" title="John Logie Baird">John Logie Baird</a></li> <li><a href="/wiki/Paul_Baran" title="Paul Baran">Paul Baran</a></li> <li><a href="/wiki/John_Bardeen" title="John Bardeen">John Bardeen</a></li> <li><a href="/wiki/Alexander_Graham_Bell" title="Alexander Graham Bell">Alexander Graham Bell</a></li> <li><a href="/wiki/Emile_Berliner" title="Emile Berliner">Emile Berliner</a></li> <li><a href="/wiki/Tim_Berners-Lee" title="Tim Berners-Lee">Tim Berners-Lee</a></li> <li><a href="/wiki/Francis_Blake_(inventor)" title="Francis Blake (inventor)">Francis Blake</a></li> <li><a href="/wiki/Jagadish_Chandra_Bose" title="Jagadish Chandra Bose">Jagadish Chandra Bose</a></li> <li><a href="/wiki/Charles_Bourseul" title="Charles Bourseul">Charles Bourseul</a></li> <li><a href="/wiki/Walter_Houser_Brattain" title="Walter Houser Brattain">Walter Houser Brattain</a></li> <li><a href="/wiki/Vint_Cerf" title="Vint Cerf">Vint Cerf</a></li> <li><a href="/wiki/Claude_Chappe" title="Claude Chappe">Claude Chappe</a></li> <li><a href="/wiki/Yogen_Dalal" class="mw-redirect" title="Yogen Dalal">Yogen Dalal</a></li> <li><a href="/wiki/Daniel_Davis_Jr." title="Daniel Davis Jr.">Daniel Davis Jr.</a></li> <li><a href="/wiki/Donald_Davies" title="Donald Davies">Donald Davies</a></li> <li><a href="/wiki/Amos_Dolbear" title="Amos Dolbear">Amos Dolbear</a></li> <li><a href="/wiki/Thomas_Edison" title="Thomas Edison">Thomas Edison</a></li> <li><a href="/wiki/Lee_de_Forest" title="Lee de Forest">Lee de Forest</a></li> <li><a href="/wiki/Philo_Farnsworth" title="Philo Farnsworth">Philo Farnsworth</a></li> <li><a href="/wiki/Reginald_Fessenden" title="Reginald Fessenden">Reginald Fessenden</a></li> <li><a href="/wiki/Elisha_Gray" title="Elisha Gray">Elisha Gray</a></li> <li><a href="/wiki/Oliver_Heaviside" title="Oliver Heaviside">Oliver Heaviside</a></li> <li><a href="/wiki/Robert_Hooke" title="Robert Hooke">Robert Hooke</a></li> <li><a href="/wiki/Erna_Schneider_Hoover" title="Erna Schneider Hoover">Erna Schneider Hoover</a></li> <li><a href="/wiki/Harold_Hopkins_(physicist)" title="Harold Hopkins (physicist)">Harold Hopkins</a></li> <li><a href="/wiki/Gardiner_Greene_Hubbard" title="Gardiner Greene Hubbard">Gardiner Greene Hubbard</a></li> <li><a href="/wiki/List_of_Internet_pioneers" title="List of Internet pioneers">Internet pioneers</a></li> <li><a href="/wiki/Bob_Kahn" class="mw-redirect" title="Bob Kahn">Bob Kahn</a></li> <li><a href="/wiki/Dawon_Kahng" title="Dawon Kahng">Dawon Kahng</a></li> <li><a href="/wiki/Charles_K._Kao" title="Charles K. Kao">Charles K. Kao</a></li> <li><a href="/wiki/Narinder_Singh_Kapany" title="Narinder Singh Kapany">Narinder Singh Kapany</a></li> <li><a href="/wiki/Hedy_Lamarr" title="Hedy Lamarr">Hedy Lamarr</a></li> <li><a href="/wiki/Roberto_Landell_de_Moura" title="Roberto Landell de Moura">Roberto Landell de Moura</a></li> <li><a href="/wiki/Innocenzo_Manzetti" title="Innocenzo Manzetti">Innocenzo Manzetti</a></li> <li><a href="/wiki/Guglielmo_Marconi" title="Guglielmo Marconi">Guglielmo Marconi</a></li> <li><a href="/wiki/Robert_Metcalfe" title="Robert Metcalfe">Robert Metcalfe</a></li> <li><a href="/wiki/Antonio_Meucci" title="Antonio Meucci">Antonio Meucci</a></li> <li><a href="/wiki/Samuel_Morse" title="Samuel Morse">Samuel Morse</a></li> <li><a href="/wiki/Jun-ichi_Nishizawa" title="Jun-ichi Nishizawa">Jun-ichi Nishizawa</a></li> <li><a href="/wiki/Charles_Grafton_Page" title="Charles Grafton Page">Charles Grafton Page</a></li> <li><a href="/wiki/Radia_Perlman" title="Radia Perlman">Radia Perlman</a></li> <li><a href="/wiki/Alexander_Stepanovich_Popov" class="mw-redirect" title="Alexander Stepanovich Popov">Alexander Stepanovich Popov</a></li> <li><a href="/wiki/Tivadar_Pusk%C3%A1s" title="Tivadar Puskás">Tivadar Puskás</a></li> <li><a href="/wiki/Johann_Philipp_Reis" title="Johann Philipp Reis">Johann Philipp Reis</a></li> <li><a href="/wiki/Claude_Shannon" title="Claude Shannon">Claude Shannon</a></li> <li><a href="/wiki/Almon_Brown_Strowger" title="Almon Brown Strowger">Almon Brown Strowger</a></li> <li><a href="/wiki/Henry_Sutton_(inventor)" title="Henry Sutton (inventor)">Henry Sutton</a></li> <li><a href="/wiki/Charles_Sumner_Tainter" title="Charles Sumner Tainter">Charles Sumner Tainter</a></li> <li><a href="/wiki/Nikola_Tesla" title="Nikola Tesla">Nikola Tesla</a></li> <li><a href="/wiki/Camille_Tissot" title="Camille Tissot">Camille Tissot</a></li> <li><a href="/wiki/Alfred_Vail" title="Alfred Vail">Alfred Vail</a></li> <li><a href="/wiki/Thomas_A._Watson" title="Thomas A. Watson">Thomas A. Watson</a></li> <li><a href="/wiki/Charles_Wheatstone" title="Charles Wheatstone">Charles Wheatstone</a></li> <li><a href="/wiki/Vladimir_K._Zworykin" title="Vladimir K. Zworykin">Vladimir K. Zworykin</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/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="/wiki/Coaxial_cable" title="Coaxial cable">Coaxial cable</a></li> <li><a href="/wiki/Fiber-optic_communication" title="Fiber-optic communication">Fiber-optic communication</a> <ul><li><a href="/wiki/Optical_fiber" title="Optical fiber">optical fiber</a></li></ul></li> <li><a href="/wiki/Free-space_optical_communication" title="Free-space optical communication">Free-space optical communication</a></li> <li><a href="/wiki/Molecular_communication" title="Molecular communication">Molecular communication</a></li> <li><a href="/wiki/Radio_wave" title="Radio wave">Radio waves</a> <ul><li><a href="/wiki/Wireless" title="Wireless">wireless</a></li></ul></li> <li><a href="/wiki/Transmission_line" title="Transmission line">Transmission line</a> <ul><li><a href="/wiki/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="/wiki/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="/wiki/Bandwidth_(computing)" title="Bandwidth (computing)">Bandwidth</a></li> <li><a href="/wiki/Telecommunications_link" title="Telecommunications link">Links</a></li> <li><a href="/wiki/Node_(networking)" title="Node (networking)">Nodes</a> <ul><li><a href="/wiki/Terminal_(telecommunication)" title="Terminal (telecommunication)">terminal</a></li></ul></li> <li><a href="/wiki/Network_switch" title="Network switch">Network switching</a> <ul><li><a href="/wiki/Circuit_switching" title="Circuit switching">circuit</a></li> <li><a href="/wiki/Packet_switching" title="Packet switching">packet</a></li></ul></li> <li><a href="/wiki/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="/wiki/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="/wiki/Space-division_multiple_access" title="Space-division multiple access">Space-division</a></li> <li><a href="/wiki/Frequency-division_multiplexing" title="Frequency-division multiplexing">Frequency-division</a></li> <li><a href="/wiki/Time-division_multiplexing" title="Time-division multiplexing">Time-division</a></li> <li><a href="/wiki/Polarization-division_multiplexing" title="Polarization-division multiplexing">Polarization-division</a></li> <li><a href="/wiki/Orbital_angular_momentum_multiplexing" title="Orbital angular momentum multiplexing">Orbital angular-momentum</a></li> <li><a href="/wiki/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="/wiki/Communication_protocol" title="Communication protocol">Communication protocol</a></li> <li><a href="/wiki/Computer_network" title="Computer network">Computer network</a></li> <li><a href="/wiki/Data_communication" title="Data communication">Data transmission</a></li> <li><a href="/wiki/Store_and_forward" title="Store and forward">Store and forward</a></li> <li><a href="/wiki/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="/wiki/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="/wiki/Cellular_network" title="Cellular network">Cellular network</a></li> <li><a href="/wiki/Ethernet" title="Ethernet">Ethernet</a></li> <li><a href="/wiki/Integrated_Services_Digital_Network" class="mw-redirect" title="Integrated Services Digital Network">ISDN</a></li> <li><a href="/wiki/Local_area_network" title="Local area network">LAN</a></li> <li><a href="/wiki/Mobile_telephony" title="Mobile telephony">Mobile</a></li> <li><a href="/wiki/Next-generation_network" title="Next-generation network">NGN</a></li> <li><a href="/wiki/Public_switched_telephone_network" title="Public switched telephone network">Public Switched Telephone</a></li> <li><a href="/wiki/Radio_network" title="Radio network">Radio</a></li> <li><a href="/wiki/Television_broadcasting" class="mw-redirect" title="Television broadcasting">Television</a></li> <li><a href="/wiki/Telex" title="Telex">Telex</a></li> <li><a href="/wiki/UUCP" title="UUCP">UUCP</a></li> <li><a href="/wiki/Wide_area_network" title="Wide area network">WAN</a></li> <li><a href="/wiki/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="/wiki/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="/wiki/ARPANET" title="ARPANET">ARPANET</a></li> <li><a href="/wiki/BITNET" title="BITNET">BITNET</a></li> <li><a href="/wiki/CYCLADES" title="CYCLADES">CYCLADES</a></li> <li><a href="/wiki/FidoNet" title="FidoNet">FidoNet</a></li> <li><a href="/wiki/Internet" title="Internet">Internet</a></li> <li><a href="/wiki/Internet2" title="Internet2">Internet2</a></li> <li><a href="/wiki/JANET" title="JANET">JANET</a></li> <li><a href="/wiki/NPL_network" title="NPL network">NPL network</a></li> <li><a href="/wiki/Toasternet" title="Toasternet">Toasternet</a></li> <li><a href="/wiki/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><a href="/wiki/Category:Telecommunications_in_Africa" title="Category:Telecommunications in Africa">Africa</a></li> <li>Americas <ul><li><a href="/wiki/Category:Telecommunications_in_North_America" title="Category:Telecommunications in North America">North</a></li> <li><a href="/wiki/Category:Telecommunications_in_South_America" title="Category:Telecommunications in South America">South</a></li></ul></li> <li><a href="/wiki/Category:Communications_in_Antarctica" title="Category:Communications in Antarctica">Antarctica</a></li> <li><a href="/wiki/Category:Telecommunications_in_Asia" title="Category:Telecommunications in Asia">Asia</a></li> <li><a href="/wiki/Category:Telecommunications_in_Europe" title="Category:Telecommunications in Europe">Europe</a></li> <li><a href="/wiki/Category:Telecommunications_in_Oceania" title="Category:Telecommunications in Oceania">Oceania</a></li> <li>(<a href="/wiki/List_of_telecommunications_regulatory_bodies" title="List of telecommunications regulatory bodies">Global telecommunications regulation bodies</a>)</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><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Telecom-icon.svg/16px-Telecom-icon.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Telecom-icon.svg/24px-Telecom-icon.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Telecom-icon.svg/32px-Telecom-icon.svg.png 2x" data-file-width="500" data-file-height="500" /></span></span> </span><a href="/wiki/Portal:Telecommunication" title="Portal:Telecommunication">Telecommunication portal</a></li> <li><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <a href="/wiki/Category:Telecommunications" title="Category:Telecommunications">Category</a></li> <li><span class="noviewer" typeof="mw:File"><span title="List-Class article"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/d/db/Symbol_list_class.svg/16px-Symbol_list_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/d/db/Symbol_list_class.svg/23px-Symbol_list_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/d/db/Symbol_list_class.svg/31px-Symbol_list_class.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <a href="/wiki/Outline_of_telecommunication" title="Outline of telecommunication">Outline</a></li> <li><span class="noviewer" typeof="mw:File"><span title="Commons page"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/12px-Commons-logo.svg.png" decoding="async" width="12" height="16" class="mw-file-element" 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