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class="vector-toc-numb">3.1.1</span> <span>1950s</span> </div> </a> <ul id="toc-1950s-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-1960s" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#1960s"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1.2</span> <span>1960s</span> </div> </a> <ul id="toc-1960s-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-1970s" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#1970s"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1.3</span> <span>1970s</span> </div> </a> <ul id="toc-1970s-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-1980s" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#1980s"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1.4</span> <span>1980s</span> </div> </a> <ul id="toc-1980s-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-1990s" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#1990s"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1.5</span> <span>1990s</span> </div> </a> <ul id="toc-1990s-sublist" class="vector-toc-list"> <li id="toc-56_kbit/s_technologies" class="vector-toc-list-item vector-toc-level-4"> <a class="vector-toc-link" href="#56_kbit/s_technologies"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1.5.1</span> <span><span>56 kbit/s</span> technologies</span> </div> </a> <ul id="toc-56_kbit/s_technologies-sublist" class="vector-toc-list"> <li id="toc-Early_56k_dial-up_products" class="vector-toc-list-item vector-toc-level-5"> <a class="vector-toc-link" href="#Early_56k_dial-up_products"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1.5.1.1</span> <span>Early 56k dial-up products</span> </div> </a> <ul id="toc-Early_56k_dial-up_products-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Standardized_56k_(V.90/V.92)" class="vector-toc-list-item vector-toc-level-5"> <a class="vector-toc-link" href="#Standardized_56k_(V.90/V.92)"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1.5.1.2</span> <span>Standardized 56k (V.90/V.92)</span> </div> </a> <ul id="toc-Standardized_56k_(V.90/V.92)-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> </ul> </li> </ul> </li> <li id="toc-Evolution_of_dial-up_speeds" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Evolution_of_dial-up_speeds"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Evolution of dial-up speeds</span> </div> </a> <ul id="toc-Evolution_of_dial-up_speeds-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Compression" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Compression"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.3</span> <span>Compression</span> </div> </a> <ul id="toc-Compression-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Methods_of_attachment" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Methods_of_attachment"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.4</span> <span>Methods of attachment</span> </div> </a> <ul id="toc-Methods_of_attachment-sublist" class="vector-toc-list"> <li id="toc-Directly_connected_modems" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Directly_connected_modems"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.4.1</span> <span>Directly connected modems</span> </div> </a> <ul id="toc-Directly_connected_modems-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Acoustic_couplers" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Acoustic_couplers"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.4.2</span> <span>Acoustic couplers</span> </div> </a> <ul id="toc-Acoustic_couplers-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Automatic_calling_units" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Automatic_calling_units"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.5</span> <span>Automatic calling units</span> </div> </a> <ul id="toc-Automatic_calling_units-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Controller-based_modems_vs._soft_modems" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Controller-based_modems_vs._soft_modems"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.6</span> <span>Controller-based modems vs. soft modems</span> </div> </a> <ul id="toc-Controller-based_modems_vs._soft_modems-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Voice/fax_modems" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Voice/fax_modems"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.7</span> <span>Voice/fax modems</span> </div> </a> <ul id="toc-Voice/fax_modems-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Modem_Over_IP_(Modem_Relay)" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Modem_Over_IP_(Modem_Relay)"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.8</span> <span>Modem Over IP (Modem Relay)</span> </div> </a> <ul id="toc-Modem_Over_IP_(Modem_Relay)-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Cloud-based_Modems" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Cloud-based_Modems"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.9</span> <span>Cloud-based Modems</span> </div> </a> <ul id="toc-Cloud-based_Modems-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Popularity" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Popularity"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.10</span> <span>Popularity</span> </div> </a> <ul id="toc-Popularity-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-TTY/TDD" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#TTY/TDD"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.11</span> <span>TTY/TDD</span> </div> </a> <ul id="toc-TTY/TDD-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Leased-line_modems" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Leased-line_modems"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Leased-line modems</span> </div> </a> <ul id="toc-Leased-line_modems-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Broadband" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Broadband"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Broadband</span> </div> </a> <button aria-controls="toc-Broadband-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Broadband subsection</span> </button> <ul id="toc-Broadband-sublist" class="vector-toc-list"> <li id="toc-Terminology" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Terminology"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1</span> <span>Terminology</span> </div> </a> <ul id="toc-Terminology-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Radio" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Radio"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Radio</span> </div> </a> <button aria-controls="toc-Radio-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Radio subsection</span> </button> <ul id="toc-Radio-sublist" class="vector-toc-list"> <li id="toc-Mobile_broadband" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Mobile_broadband"> <div class="vector-toc-text"> <span class="vector-toc-numb">6.1</span> <span>Mobile broadband</span> </div> </a> <ul id="toc-Mobile_broadband-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Optical_modem" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Optical_modem"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>Optical modem</span> </div> </a> <ul id="toc-Optical_modem-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Home_networking" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Home_networking"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>Home networking</span> </div> </a> <ul id="toc-Home_networking-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Null_modem" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Null_modem"> <div class="vector-toc-text"> <span class="vector-toc-numb">9</span> <span>Null modem</span> </div> </a> <ul id="toc-Null_modem-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Short-haul_modem" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Short-haul_modem"> <div class="vector-toc-text"> <span class="vector-toc-numb">10</span> <span>Short-haul modem</span> </div> </a> <ul id="toc-Short-haul_modem-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">11</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Further_reading" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Further_reading"> <div class="vector-toc-text"> <span class="vector-toc-numb">12</span> <span>Further reading</span> </div> </a> <ul id="toc-Further_reading-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">13</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">14</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Modem</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 77 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-77" 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">77 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-af mw-list-item"><a href="https://af.wikipedia.org/wiki/Modem" title="Modem – Afrikaans" lang="af" hreflang="af" data-title="Modem" data-language-autonym="Afrikaans" data-language-local-name="Afrikaans" class="interlanguage-link-target"><span>Afrikaans</span></a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D9%85%D9%88%D8%AF%D9%85" title="مودم – Arabic" lang="ar" hreflang="ar" data-title="مودم" 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/Modem" title="Modem – Azerbaijani" lang="az" hreflang="az" data-title="Modem" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-azb mw-list-item"><a href="https://azb.wikipedia.org/wiki/%D9%85%D9%88%D8%AF%D9%85" title="مودم – South Azerbaijani" lang="azb" hreflang="azb" data-title="مودم" data-language-autonym="تۆرکجه" data-language-local-name="South Azerbaijani" class="interlanguage-link-target"><span>تۆرکجه</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%AE%E0%A6%A1%E0%A7%87%E0%A6%AE" title="মডেম – Bangla" lang="bn" hreflang="bn" data-title="মডেম" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%9C%D0%B0%D0%B4%D1%8D%D0%BC" title="Мадэм – Belarusian" lang="be" hreflang="be" data-title="Мадэм" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-be-x-old mw-list-item"><a href="https://be-tarask.wikipedia.org/wiki/%D0%9C%D0%B0%D0%B4%D1%8D%D0%BC" title="Мадэм – Belarusian (Taraškievica orthography)" lang="be-tarask" hreflang="be-tarask" data-title="Мадэм" data-language-autonym="Беларуская (тарашкевіца)" data-language-local-name="Belarusian (Taraškievica orthography)" class="interlanguage-link-target"><span>Беларуская (тарашкевіца)</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%9C%D0%BE%D0%B4%D0%B5%D0%BC" title="Модем – Bulgarian" lang="bg" hreflang="bg" data-title="Модем" 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/Modem" title="Modem – Bosnian" lang="bs" hreflang="bs" data-title="Modem" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/M%C3%B2dem" title="Mòdem – Catalan" lang="ca" hreflang="ca" data-title="Mòdem" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Modem" title="Modem – Czech" lang="cs" hreflang="cs" data-title="Modem" 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/Modem" title="Modem – Danish" lang="da" hreflang="da" data-title="Modem" 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/Modem" title="Modem – German" lang="de" hreflang="de" data-title="Modem" 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/Modem" title="Modem – Estonian" lang="et" hreflang="et" data-title="Modem" 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%9C%CF%8C%CE%BD%CF%84%CE%B5%CE%BC" title="Μόντεμ – Greek" lang="el" hreflang="el" data-title="Μόντεμ" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/M%C3%B3dem" title="Módem – Spanish" lang="es" hreflang="es" data-title="Módem" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Modemo" title="Modemo – Esperanto" lang="eo" hreflang="eo" data-title="Modemo" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Modem" title="Modem – Basque" lang="eu" hreflang="eu" data-title="Modem" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D9%85%D9%88%D8%AF%D9%85" title="مودم – Persian" lang="fa" hreflang="fa" data-title="مودم" 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/Modem" title="Modem – French" lang="fr" hreflang="fr" data-title="Modem" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ga mw-list-item"><a href="https://ga.wikipedia.org/wiki/M%C3%B3ideim" title="Móideim – Irish" lang="ga" hreflang="ga" data-title="Móideim" data-language-autonym="Gaeilge" data-language-local-name="Irish" class="interlanguage-link-target"><span>Gaeilge</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/M%C3%B3dem" title="Módem – Galician" lang="gl" hreflang="gl" data-title="Módem" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-gu mw-list-item"><a href="https://gu.wikipedia.org/wiki/%E0%AA%AE%E0%AB%8B%E0%AA%A1%E0%AA%AE" title="મોડમ – Gujarati" lang="gu" hreflang="gu" data-title="મોડમ" data-language-autonym="ગુજરાતી" data-language-local-name="Gujarati" class="interlanguage-link-target"><span>ગુજરાતી</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EB%AA%A8%EB%8E%80" title="모뎀 – Korean" lang="ko" hreflang="ko" data-title="모뎀" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%AE%E0%A5%89%E0%A4%A1%E0%A5%87%E0%A4%AE" title="मॉडेम – Hindi" lang="hi" hreflang="hi" data-title="मॉडेम" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Modem" title="Modem – Croatian" lang="hr" hreflang="hr" data-title="Modem" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Modem" title="Modem – Indonesian" lang="id" hreflang="id" data-title="Modem" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-is mw-list-item"><a href="https://is.wikipedia.org/wiki/M%C3%B3tald" title="Mótald – Icelandic" lang="is" hreflang="is" data-title="Mótald" data-language-autonym="Íslenska" data-language-local-name="Icelandic" class="interlanguage-link-target"><span>Íslenska</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Modem" title="Modem – Italian" lang="it" hreflang="it" data-title="Modem" 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%9E%D7%95%D7%93%D7%9D" title="מודם – Hebrew" lang="he" hreflang="he" data-title="מודם" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-jv mw-list-item"><a href="https://jv.wikipedia.org/wiki/Modem" title="Modem – Javanese" lang="jv" hreflang="jv" data-title="Modem" data-language-autonym="Jawa" data-language-local-name="Javanese" class="interlanguage-link-target"><span>Jawa</span></a></li><li class="interlanguage-link interwiki-krc mw-list-item"><a href="https://krc.wikipedia.org/wiki/%D0%9C%D0%BE%D0%B4%D0%B5%D0%BC" title="Модем – Karachay-Balkar" lang="krc" hreflang="krc" data-title="Модем" data-language-autonym="Къарачай-малкъар" data-language-local-name="Karachay-Balkar" class="interlanguage-link-target"><span>Къарачай-малкъар</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%9C%D0%BE%D0%B4%D0%B5%D0%BC" title="Модем – Kazakh" lang="kk" hreflang="kk" data-title="Модем" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target"><span>Қазақша</span></a></li><li class="interlanguage-link interwiki-sw mw-list-item"><a href="https://sw.wikipedia.org/wiki/Kiwiano" title="Kiwiano – Swahili" lang="sw" hreflang="sw" data-title="Kiwiano" data-language-autonym="Kiswahili" data-language-local-name="Swahili" class="interlanguage-link-target"><span>Kiswahili</span></a></li><li class="interlanguage-link interwiki-ky mw-list-item"><a href="https://ky.wikipedia.org/wiki/%D0%9C%D0%BE%D0%B4%D0%B5%D0%BC" title="Модем – Kyrgyz" lang="ky" hreflang="ky" data-title="Модем" data-language-autonym="Кыргызча" data-language-local-name="Kyrgyz" class="interlanguage-link-target"><span>Кыргызча</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Modems" title="Modems – Latvian" lang="lv" hreflang="lv" data-title="Modems" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target"><span>Latviešu</span></a></li><li class="interlanguage-link interwiki-lb mw-list-item"><a href="https://lb.wikipedia.org/wiki/Modem" title="Modem – Luxembourgish" lang="lb" hreflang="lb" data-title="Modem" data-language-autonym="Lëtzebuergesch" data-language-local-name="Luxembourgish" class="interlanguage-link-target"><span>Lëtzebuergesch</span></a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/Modemas" title="Modemas – Lithuanian" lang="lt" hreflang="lt" data-title="Modemas" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-lmo mw-list-item"><a href="https://lmo.wikipedia.org/wiki/Modem" title="Modem – Lombard" lang="lmo" hreflang="lmo" data-title="Modem" data-language-autonym="Lombard" data-language-local-name="Lombard" class="interlanguage-link-target"><span>Lombard</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/Modem" title="Modem – Hungarian" lang="hu" hreflang="hu" data-title="Modem" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-mk mw-list-item"><a href="https://mk.wikipedia.org/wiki/%D0%9C%D0%BE%D0%B4%D0%B5%D0%BC" title="Модем – Macedonian" lang="mk" hreflang="mk" data-title="Модем" data-language-autonym="Македонски" data-language-local-name="Macedonian" class="interlanguage-link-target"><span>Македонски</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%AE%E0%B5%8B%E0%B4%A1%E0%B4%82" title="മോഡം – Malayalam" lang="ml" hreflang="ml" data-title="മോഡം" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Modem" title="Modem – Malay" lang="ms" hreflang="ms" data-title="Modem" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-mn mw-list-item"><a href="https://mn.wikipedia.org/wiki/%D0%9C%D0%BE%D0%B4%D0%B5%D0%BC" title="Модем – Mongolian" lang="mn" hreflang="mn" data-title="Модем" data-language-autonym="Монгол" data-language-local-name="Mongolian" class="interlanguage-link-target"><span>Монгол</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Modem" title="Modem – Dutch" lang="nl" hreflang="nl" data-title="Modem" 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/%E3%83%A2%E3%83%87%E3%83%A0" title="モデム – Japanese" lang="ja" hreflang="ja" data-title="モデム" 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/Modem" title="Modem – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Modem" 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-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Modem" title="Modem – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Modem" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-oc mw-list-item"><a href="https://oc.wikipedia.org/wiki/Mod%C3%A8m" title="Modèm – Occitan" lang="oc" hreflang="oc" data-title="Modèm" data-language-autonym="Occitan" data-language-local-name="Occitan" class="interlanguage-link-target"><span>Occitan</span></a></li><li class="interlanguage-link interwiki-mhr mw-list-item"><a href="https://mhr.wikipedia.org/wiki/%D0%9C%D0%BE%D0%B4%D0%B5%D0%BC" title="Модем – Eastern Mari" lang="mhr" hreflang="mhr" data-title="Модем" data-language-autonym="Олык марий" data-language-local-name="Eastern Mari" class="interlanguage-link-target"><span>Олык марий</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Modem" title="Modem – Polish" lang="pl" hreflang="pl" data-title="Modem" 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/Modem" title="Modem – Portuguese" lang="pt" hreflang="pt" data-title="Modem" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/Modem" title="Modem – Romanian" lang="ro" hreflang="ro" data-title="Modem" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%9C%D0%BE%D0%B4%D0%B5%D0%BC" title="Модем – Russian" lang="ru" hreflang="ru" data-title="Модем" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-sah mw-list-item"><a href="https://sah.wikipedia.org/wiki/%D0%9C%D0%BE%D0%B4%D0%B5%D0%BC" title="Модем – Yakut" lang="sah" hreflang="sah" data-title="Модем" data-language-autonym="Саха тыла" data-language-local-name="Yakut" class="interlanguage-link-target"><span>Саха тыла</span></a></li><li class="interlanguage-link interwiki-sq mw-list-item"><a href="https://sq.wikipedia.org/wiki/Modemi" title="Modemi – Albanian" lang="sq" hreflang="sq" data-title="Modemi" data-language-autonym="Shqip" data-language-local-name="Albanian" class="interlanguage-link-target"><span>Shqip</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Modem" title="Modem – Simple English" lang="en-simple" hreflang="en-simple" data-title="Modem" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Modem" title="Modem – Slovak" lang="sk" hreflang="sk" data-title="Modem" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Modem" title="Modem – Slovenian" lang="sl" hreflang="sl" data-title="Modem" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-ckb mw-list-item"><a href="https://ckb.wikipedia.org/wiki/%D9%85%DB%86%D8%AF%DB%8E%D9%85" title="مۆدێم – Central Kurdish" lang="ckb" hreflang="ckb" data-title="مۆدێم" data-language-autonym="کوردی" data-language-local-name="Central Kurdish" class="interlanguage-link-target"><span>کوردی</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/%D0%9C%D0%BE%D0%B4%D0%B5%D0%BC" title="Модем – Serbian" lang="sr" hreflang="sr" data-title="Модем" 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-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Modem" title="Modem – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Modem" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-su mw-list-item"><a href="https://su.wikipedia.org/wiki/Modem" title="Modem – Sundanese" lang="su" hreflang="su" data-title="Modem" data-language-autonym="Sunda" data-language-local-name="Sundanese" class="interlanguage-link-target"><span>Sunda</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Modeemi" title="Modeemi – Finnish" lang="fi" hreflang="fi" data-title="Modeemi" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Modem" title="Modem – Swedish" lang="sv" hreflang="sv" data-title="Modem" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-ta mw-list-item"><a href="https://ta.wikipedia.org/wiki/%E0%AE%87%E0%AE%A3%E0%AE%95%E0%AF%8D%E0%AE%95%E0%AE%BF" title="இணக்கி – Tamil" lang="ta" hreflang="ta" data-title="இணக்கி" data-language-autonym="தமிழ்" data-language-local-name="Tamil" class="interlanguage-link-target"><span>தமிழ்</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B9%82%E0%B8%A1%E0%B9%80%E0%B8%94%E0%B9%87%E0%B8%A1" title="โมเด็ม – Thai" lang="th" hreflang="th" data-title="โมเด็ม" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-tg mw-list-item"><a href="https://tg.wikipedia.org/wiki/%D0%9C%D0%BE%D0%B4%D0%B5%D0%BC" title="Модем – Tajik" lang="tg" hreflang="tg" data-title="Модем" data-language-autonym="Тоҷикӣ" data-language-local-name="Tajik" class="interlanguage-link-target"><span>Тоҷикӣ</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Modem" title="Modem – Turkish" lang="tr" hreflang="tr" data-title="Modem" 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%9C%D0%BE%D0%B4%D0%B5%D0%BC" title="Модем – Ukrainian" lang="uk" hreflang="uk" data-title="Модем" 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/%D8%AA%D8%B6%D9%85%DB%8C%D9%84%D8%A7%D8%B5%DB%81" title="تضمیلاصہ – Urdu" lang="ur" hreflang="ur" data-title="تضمیلاصہ" data-language-autonym="اردو" data-language-local-name="Urdu" class="interlanguage-link-target"><span>اردو</span></a></li><li class="interlanguage-link interwiki-vec mw-list-item"><a href="https://vec.wikipedia.org/wiki/Modem" title="Modem – Venetian" lang="vec" hreflang="vec" data-title="Modem" data-language-autonym="Vèneto" data-language-local-name="Venetian" class="interlanguage-link-target"><span>Vèneto</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/Modem" title="Modem – Vietnamese" lang="vi" hreflang="vi" data-title="Modem" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-wuu mw-list-item"><a href="https://wuu.wikipedia.org/wiki/%E8%B0%83%E5%88%B6%E8%A7%A3%E8%B0%83%E5%99%A8" title="调制解调器 – Wu" lang="wuu" hreflang="wuu" data-title="调制解调器" data-language-autonym="吴语" data-language-local-name="Wu" class="interlanguage-link-target"><span>吴语</span></a></li><li class="interlanguage-link interwiki-yi mw-list-item"><a href="https://yi.wikipedia.org/wiki/%D7%9E%D7%90%D7%93%D7%A2%D7%9D" title="מאדעם – Yiddish" lang="yi" hreflang="yi" data-title="מאדעם" data-language-autonym="ייִדיש" data-language-local-name="Yiddish" class="interlanguage-link-target"><span>ייִדיש</span></a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/%E6%95%B8%E6%93%9A%E6%A9%9F" title="數據機 – Cantonese" lang="yue" hreflang="yue" data-title="數據機" data-language-autonym="粵語" data-language-local-name="Cantonese" class="interlanguage-link-target"><span>粵語</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E8%B0%83%E5%88%B6%E8%A7%A3%E8%B0%83%E5%99%A8" title="调制解调器 – Chinese" lang="zh" hreflang="zh" data-title="调制解调器" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit 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.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">"Computer modem" redirects here. Not to be confused with <a href="/wiki/Computer_Modern" title="Computer Modern">Computer Modern</a>.</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">For the French political party known as Modem, see <a href="/wiki/Democratic_Movement_(France)" title="Democratic Movement (France)">Democratic Movement (France)</a>. For the ancient Hebrew city, see <a href="/wiki/Modi%27in-Maccabim-Re%27ut" title="Modi'in-Maccabim-Re'ut">Modi'in-Maccabim-Re'ut</a>.</div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Analogue_modem_-_acoustic_coupler.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e5/Analogue_modem_-_acoustic_coupler.jpg/220px-Analogue_modem_-_acoustic_coupler.jpg" decoding="async" width="220" height="233" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e5/Analogue_modem_-_acoustic_coupler.jpg/330px-Analogue_modem_-_acoustic_coupler.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e5/Analogue_modem_-_acoustic_coupler.jpg/440px-Analogue_modem_-_acoustic_coupler.jpg 2x" data-file-width="538" data-file-height="569" /></a><figcaption><a href="/wiki/Acoustic_coupler" title="Acoustic coupler">Acoustic coupler</a> modems used a telephone handset as the audio medium, with the user dialing the desired number and then pressing the handset into the modem to complete the connection. These systems generally operated at a speed of 300 bits per second.</figcaption></figure> <style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:": "}.mw-parser-output .hlist dd::after,.mw-parser-output .hlist li::after{content:" · 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.sidebar-content{padding:0 0.5em 0.4em}.mw-parser-output .sidebar-content-with-subgroup{padding:0.1em 0.4em 0.2em}.mw-parser-output .sidebar-above,.mw-parser-output .sidebar-below{padding:0.3em 0.8em;font-weight:bold}.mw-parser-output .sidebar-collapse .sidebar-above,.mw-parser-output .sidebar-collapse .sidebar-below{border-top:1px solid #aaa;border-bottom:1px solid #aaa}.mw-parser-output .sidebar-navbar{text-align:right;font-size:115%;padding:0 0.4em 0.4em}.mw-parser-output .sidebar-list-title{padding:0 0.4em;text-align:left;font-weight:bold;line-height:1.6em;font-size:105%}.mw-parser-output .sidebar-list-title-c{padding:0 0.4em;text-align:center;margin:0 3.3em}@media(max-width:640px){body.mediawiki .mw-parser-output .sidebar{width:100%!important;clear:both;float:none!important;margin-left:0!important;margin-right:0!important}}body.skin--responsive .mw-parser-output .sidebar a>img{max-width:none!important}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}}</style><table class="sidebar nomobile nowraplinks"><tbody><tr><th class="sidebar-title" style="background-color: #bdb"><a href="/wiki/Passband" title="Passband">Passband</a> <a href="/wiki/Modulation" title="Modulation">modulation</a></th></tr><tr><td class="sidebar-image"><span typeof="mw:File"><a href="/wiki/File:Modulation_categorization.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e7/Modulation_categorization.svg/300px-Modulation_categorization.svg.png" decoding="async" width="300" height="72" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e7/Modulation_categorization.svg/450px-Modulation_categorization.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e7/Modulation_categorization.svg/600px-Modulation_categorization.svg.png 2x" data-file-width="1565" data-file-height="374" /></a></span></td></tr><tr><th class="sidebar-heading" style="background-color: #cfc"> <a href="/wiki/Modulation#Analog_modulation_methods" title="Modulation">Analog modulation</a></th></tr><tr><td class="sidebar-content hlist"> <ul><li><a href="/wiki/Amplitude_modulation" title="Amplitude modulation">AM</a></li> <li><a href="/wiki/Frequency_modulation" title="Frequency modulation">FM</a></li> <li><a href="/wiki/Phase_modulation" title="Phase modulation">PM</a></li> <li><a href="/wiki/Quadrature_amplitude_modulation" title="Quadrature amplitude modulation">QAM</a></li> <li><a href="/wiki/Space_modulation" title="Space modulation">SM</a></li> <li><a href="/wiki/Single-sideband_modulation" title="Single-sideband modulation">SSB</a></li></ul></td> </tr><tr><th class="sidebar-heading" style="background-color: #cfc"> <a href="/wiki/Modulation#Digital_modulation_methods" title="Modulation">Digital modulation</a></th></tr><tr><td class="sidebar-content hlist"> <ul><li><a href="/wiki/Amplitude-shift_keying" title="Amplitude-shift keying">ASK</a></li> <li><a href="/wiki/Amplitude_and_phase-shift_keying" title="Amplitude and phase-shift keying">APSK</a></li> <li><a href="/wiki/Continuous_phase_modulation" title="Continuous phase modulation">CPM</a></li> <li><a href="/wiki/Frequency-shift_keying" title="Frequency-shift keying">FSK</a></li> <li><a href="/wiki/Multiple_frequency-shift_keying" title="Multiple frequency-shift keying">MFSK</a></li> <li><a href="/wiki/Minimum-shift_keying" title="Minimum-shift keying">MSK</a></li> <li><a href="/wiki/On%E2%80%93off_keying" title="On–off keying">OOK</a></li> <li><a href="/wiki/Pulse-position_modulation" title="Pulse-position modulation">PPM</a></li> <li><a href="/wiki/Phase-shift_keying" title="Phase-shift keying">PSK</a></li> <li><a href="/wiki/Quadrature_amplitude_modulation" title="Quadrature amplitude modulation">QAM</a></li> <li><a href="/wiki/Single-carrier_FDMA" title="Single-carrier FDMA">SC-FDE</a></li> <li><a href="/wiki/Trellis_coded_modulation" title="Trellis coded modulation">TCM</a></li> <li><a href="/wiki/TC-PAM" title="TC-PAM">TC-PAM</a></li> <li><a href="/wiki/Wavelet_modulation" title="Wavelet modulation">WDM</a></li></ul></td> </tr><tr><th class="sidebar-heading" style="background-color: #cfc"> <a href="/wiki/Hierarchical_modulation" title="Hierarchical modulation">Hierarchical modulation</a></th></tr><tr><td class="sidebar-content hlist"> <ul><li><a href="/wiki/Quadrature_amplitude_modulation" title="Quadrature amplitude modulation">QAM</a></li> <li><a href="/wiki/Wavelet_modulation" title="Wavelet modulation">WDM</a></li></ul></td> </tr><tr><th class="sidebar-heading" style="background-color: #cfc"> <a href="/wiki/Spread_spectrum" title="Spread spectrum">Spread spectrum</a></th></tr><tr><td class="sidebar-content hlist"> <ul><li><a href="/wiki/Chirp_spread_spectrum" title="Chirp spread spectrum">CSS</a></li> <li><a href="/wiki/Direct-sequence_spread_spectrum" title="Direct-sequence spread spectrum">DSSS</a></li> <li><a href="/wiki/Frequency-hopping_spread_spectrum" title="Frequency-hopping spread spectrum">FHSS</a></li> <li><a href="/wiki/Time-hopping" title="Time-hopping">THSS</a></li></ul></td> </tr><tr><th class="sidebar-heading" style="background-color: #cfc"> See also</th></tr><tr><td class="sidebar-content hlist"> <ul><li><a href="/wiki/Category:Capacity-approaching_codes" title="Category:Capacity-approaching codes">Capacity-approaching codes</a></li> <li><a href="/wiki/Demodulation" title="Demodulation">Demodulation</a></li> <li><a href="/wiki/Line_code" title="Line code">Line coding</a></li> <li><a class="mw-selflink selflink">Modem</a></li> <li><a href="/wiki/Angle_modulation" title="Angle modulation">AnM</a></li> <li><a href="/wiki/Polar_modulation" title="Polar modulation">PoM</a></li> <li><a href="/wiki/Pulse-amplitude_modulation" title="Pulse-amplitude modulation">PAM</a></li> <li><a href="/wiki/Pulse-code_modulation" title="Pulse-code modulation">PCM</a></li> <li><a href="/wiki/Pulse-density_modulation" title="Pulse-density modulation">PDM</a></li> <li><a href="/wiki/Pulse-width_modulation" title="Pulse-width modulation">PWM</a></li> <li><a href="/wiki/Delta-sigma_modulation" title="Delta-sigma modulation">ΔΣM</a></li> <li><a href="/wiki/Orthogonal_frequency-division_multiplexing" title="Orthogonal frequency-division multiplexing">OFDM</a></li> <li><a href="/wiki/Frequency-division_multiplexing" title="Frequency-division multiplexing">FDM</a></li> <li><a href="/wiki/Multiplexing" title="Multiplexing">Multiplexing</a></li></ul></td> </tr><tr><td class="sidebar-navbar"><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:Modulation_techniques" title="Template:Modulation techniques"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Modulation_techniques" title="Template talk:Modulation techniques"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Modulation_techniques" title="Special:EditPage/Template:Modulation techniques"><abbr title="Edit this template">e</abbr></a></li></ul></div></td></tr></tbody></table> <p>A <b>modulator-demodulator</b>, commonly referred to as a <b>modem</b>, is a <a href="/wiki/Computer_hardware" title="Computer hardware">computer hardware</a> device that converts <a href="/wiki/Digital_data" title="Digital data">data from a digital format</a> into a format suitable for an analog <a href="/wiki/Transmission_medium" title="Transmission medium">transmission medium</a> such as telephone or radio. A modem transmits data by <a href="/wiki/Modulation#Digital_modulation_methods" title="Modulation">modulating</a> one or more <a href="/wiki/Carrier_wave" title="Carrier wave">carrier wave</a> signals to encode <a href="/wiki/Digital_information" class="mw-redirect" title="Digital information">digital information</a>, while the receiver <a href="/wiki/Demodulation" title="Demodulation">demodulates</a> the signal to recreate the original digital information. The goal is to produce a <a href="/wiki/Signal_(electronics)" class="mw-redirect" title="Signal (electronics)">signal</a> that can be transmitted easily and decoded reliably. Modems can be used with almost any means of transmitting analog signals, from <a href="/wiki/Light-emitting_diode" title="Light-emitting diode">LEDs</a> to <a href="/wiki/Radio" title="Radio">radio</a>. </p><p>Early modems were devices that used audible sounds suitable for transmission over traditional <a href="/wiki/Telephone" title="Telephone">telephone</a> systems and <a href="/wiki/Leased_line" title="Leased line">leased lines</a>. These generally operated at 110 or 300 bits per second (bit/s), and the connection between devices was normally manual, using an attached <a href="/wiki/Telephone_handset" class="mw-redirect" title="Telephone handset">telephone handset</a>. By the 1970s, higher speeds of 1,200 and 2,400 bit/s for asynchronous dial connections, 4,800 bit/s for synchronous leased line connections and 35 kbit/s for synchronous conditioned leased lines were available. By the 1980s, less expensive 1,200 and 2,400 bit/s dialup modems were being released, and modems working on radio and other systems were available. As device sophistication grew rapidly in the late 1990s, telephone-based modems quickly exhausted the available <a href="/wiki/Bandwidth_(computing)" title="Bandwidth (computing)">bandwidth</a>, reaching 56 kbit/s. </p><p>The rise of public use of the <a href="/wiki/Internet" title="Internet">internet</a> during the late 1990s led to demands for much higher performance, leading to the move away from audio-based systems to entirely new encodings on <a href="/wiki/Cable_television" title="Cable television">cable television</a> lines and short-range signals in <a href="/wiki/Subcarrier" title="Subcarrier">subcarriers</a> on telephone lines. The move to <a href="/wiki/Cellular_telephone" class="mw-redirect" title="Cellular telephone">cellular telephones</a>, especially in the late 1990s and the emergence of <a href="/wiki/Smartphone" title="Smartphone">smartphones</a> in the 2000s led to the development of ever-faster radio-based systems. Today, modems are ubiquitous and largely invisible, included in almost every mobile computing device in one form or another, and generally capable of speeds on the order of tens or hundreds of megabytes per second. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Speeds">Speeds</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=1" title="Edit section: Speeds"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Modems are frequently classified by the maximum amount of data they can send in a given <a href="/wiki/Time_unit" class="mw-redirect" title="Time unit">unit of time</a>, usually expressed in <a href="/wiki/Bits_per_second" class="mw-redirect" title="Bits per second">bits per second</a> (symbol <b>bit/s</b>, sometimes abbreviated "bps") or rarely in <a href="/wiki/Bytes_per_second" class="mw-redirect" title="Bytes per second">bytes per second</a> (symbol <b>B/s</b>). Modern broadband modem speeds are typically expressed in megabits per second (Mbit/s). </p><p>Historically, modems were often classified by their <a href="/wiki/Symbol_rate" title="Symbol rate">symbol rate</a>, measured in <a href="/wiki/Baud" title="Baud">baud</a>. The baud unit denotes symbols per second, or the number of times per second the modem sends a new signal. For example, the <a href="/wiki/ITU-T_V.21" class="mw-redirect" title="ITU-T V.21">ITU-T V.21</a> standard used <a href="/wiki/Frequency-shift_keying#Audio_FSK" title="Frequency-shift keying">audio frequency-shift keying</a> with two possible frequencies, corresponding to two distinct symbols (or one bit per symbol), to carry 300 bits per second using 300 baud. By contrast, the original <a href="/wiki/ITU-T_V.22" class="mw-redirect" title="ITU-T V.22">ITU-T V.22</a> standard, which could transmit and receive four distinct symbols (two bits per symbol), transmitted 1,200 bits by sending 600 symbols per second (600 baud) using <a href="/wiki/Phase-shift_keying" title="Phase-shift keying">phase-shift keying</a>. </p><p>Many modems are variable-rate, permitting them to be used over a medium with less than ideal characteristics, such as a telephone line that is of poor quality or is too long. This capability is often adaptive so that a modem can discover the maximum practical transmission rate during the connect phase, or during operation. </p> <figure class="mw-halign-center" typeof="mw:File/Thumb"><a href="/wiki/File:Australian-modems.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/50/Australian-modems.jpg/800px-Australian-modems.jpg" decoding="async" width="800" height="186" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/50/Australian-modems.jpg/1200px-Australian-modems.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/50/Australian-modems.jpg/1600px-Australian-modems.jpg 2x" data-file-width="2516" data-file-height="586" /></a><figcaption>Collection of modems once used in Australia, including dial-up, DSL, and cable modems</figcaption></figure> <div class="mw-heading mw-heading2"><h2 id="Overall_history">Overall history</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=2" title="Edit section: Overall history"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Modems grew out of the need to connect <a href="/wiki/Teleprinter" title="Teleprinter">teleprinters</a> over ordinary phone lines instead of the more expensive leased lines which had previously been used for <a href="/wiki/Current_loop" title="Current loop">current loop</a>–based teleprinters and automated <a href="/wiki/Telegraph" class="mw-redirect" title="Telegraph">telegraphs</a>. The earliest devices which satisfy the definition of a modem may have been the <a href="/wiki/Multiplexer" title="Multiplexer">multiplexers</a> used by <a href="/wiki/News_agency" title="News agency">news wire services</a> in the 1920s.<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> </p><p>In 1941, the <a href="/wiki/Allies_of_World_War_II" title="Allies of World War II">Allies</a> developed a voice <a href="/wiki/Encryption" title="Encryption">encryption</a> system called <a href="/wiki/SIGSALY" title="SIGSALY">SIGSALY</a> which used a <a href="/wiki/Vocoder" title="Vocoder">vocoder</a> to digitize speech, then encrypted the speech with one-time pad and encoded the digital data as tones using frequency shift keying. This was also a digital modulation technique, making this an early modem.<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> </p><p>Commercial modems largely did not become available until the late 1950s, when the rapid development of computer technology created demand for a method of connecting computers together over long distances, resulting in the <a href="/wiki/Bell_Telephone_Company" title="Bell Telephone Company">Bell Company</a> and then other businesses producing an increasing number of computer modems for use over both switched and leased telephone lines. </p><p>Later developments would produce modems that operated over <a href="/wiki/Cable_Internet_access" title="Cable Internet access">cable television lines</a>, <a href="/wiki/Power-line_communication" title="Power-line communication">power lines</a>, and various <a href="#Radio">radio technologies</a>, as well as modems that achieved <a href="/wiki/Broadband" title="Broadband">much higher speeds</a> over telephone lines. </p> <div class="mw-heading mw-heading2"><h2 id="Dial-up">Dial-up</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=3" title="Edit section: Dial-up"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A dial-up modem transmits computer data over an ordinary <a href="/wiki/Public_switched_telephone_network" title="Public switched telephone network">switched</a> telephone line that has not been designed for data use. It was once a widely known technology, mass-marketed globally <a href="/wiki/Dial-up_Internet_access" title="Dial-up Internet access">dial-up internet access</a>. In the 1990s, tens of millions of people in the United States alone used dial-up modems for internet access.<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>Dial-up service has since been largely superseded by <a href="/wiki/Broadband_Internet" class="mw-redirect" title="Broadband Internet">broadband internet</a>,<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> such as <a href="/wiki/DSL" class="mw-redirect" title="DSL">DSL</a>. </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=Modem&action=edit&section=4" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading4"><h4 id="1950s">1950s</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=5" title="Edit section: 1950s"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:TeleGuide-terminal.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5d/TeleGuide-terminal.jpg/220px-TeleGuide-terminal.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5d/TeleGuide-terminal.jpg/330px-TeleGuide-terminal.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/5d/TeleGuide-terminal.jpg/440px-TeleGuide-terminal.jpg 2x" data-file-width="1200" data-file-height="900" /></a><figcaption>TeleGuide terminal</figcaption></figure> <p>Mass production of telephone line modems in the United States began as part of the <a href="/wiki/Semi_Automatic_Ground_Environment" class="mw-redirect" title="Semi Automatic Ground Environment">SAGE</a> air-defense system in 1958, connecting terminals at various airbases, radar sites, and command-and-control centers to the SAGE director centers scattered around the United States and <a href="/wiki/Canada" title="Canada">Canada</a>. </p><p>Shortly afterwards in 1959, the technology in the SAGE modems was made available commercially as the <a href="/wiki/Bell_101" title="Bell 101">Bell 101</a>, which provided 110 bit/s speeds. Bell called this and several other early modems "datasets". </p> <div class="mw-heading mw-heading4"><h4 id="1960s">1960s</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=6" title="Edit section: 1960s"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Some early modems were based on <a href="/wiki/Touch-tone" class="mw-redirect" title="Touch-tone">touch-tone</a> frequencies, such as Bell 400-style touch-tone modems.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p><p>The <a href="/wiki/Bell_103_modem" class="mw-redirect" title="Bell 103 modem">Bell 103A</a> standard was introduced by <a href="/wiki/AT%26T" title="AT&T">AT&T</a> in 1962. It provided full-duplex service at 300 bit/s over normal phone lines. <a href="/wiki/Frequency-shift_keying" title="Frequency-shift keying">Frequency-shift keying</a> was used, with the call originator transmitting at 1,070 or 1,270 <a href="/wiki/Hertz" title="Hertz">Hz</a> and the answering modem transmitting at 2,025 or 2,225 Hz.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>The 103 modem would eventually become a de facto standard once third-party (non-AT&T) modems reached the market, and throughout the 1970s, independently made modems compatible with the Bell 103 de facto standard were commonplace.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> Example models included the <a href="/wiki/Novation_CAT" title="Novation CAT">Novation CAT</a> and the <a href="/wiki/Anderson-Jacobson" class="mw-redirect" title="Anderson-Jacobson">Anderson-Jacobson</a>. A lower-cost option was the <a href="/wiki/Pennywhistle_modem" title="Pennywhistle modem">Pennywhistle modem</a>, designed to be built using readily available parts.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p><p>Teletype machines were granted access to remote networks such as the <a href="/wiki/Teletypewriter_eXchange" class="mw-redirect" title="Teletypewriter eXchange">Teletypewriter Exchange</a> using the Bell 103 modem.<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> AT&T also produced reduced-cost units, the originate-only 113D and the answer-only 113B/C modems. </p> <div class="mw-heading mw-heading4"><h4 id="1970s">1970s</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=7" title="Edit section: 1970s"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <i>201A</i> <i>Data-Phone</i> was a synchronous modem using two-bit-per-symbol <a href="/wiki/Phase-shift_keying" title="Phase-shift keying">phase-shift keying</a> (PSK) encoding, achieving 2,000 bit/s half-duplex over normal phone lines.<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> In this system the two tones for any one side of the connection are sent at similar frequencies as in the 300 bit/s systems, but slightly out of phase. </p><p>In early 1973, <a href="/wiki/Racal" title="Racal">Vadic</a> introduced the <i>VA3400</i> which performed full-duplex at 1,200 bit/s over a normal phone line.<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> </p><p>In November 1976, AT&T introduced the 212A modem, similar in design, but using the lower frequency set for transmission. It was not compatible with the VA3400,<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> but it would operate with 103A modem at 300 bit/s. </p><p>In 1977, Vadic responded with the VA3467 triple modem, an answer-only modem sold to computer center operators that supported Vadic's 1,200-bit/s mode, AT&T's 212A mode, and 103A operation.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Hayes_300_Baud_Smartmodem_02.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/f9/Hayes_300_Baud_Smartmodem_02.jpg/220px-Hayes_300_Baud_Smartmodem_02.jpg" decoding="async" width="220" height="82" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/f9/Hayes_300_Baud_Smartmodem_02.jpg/330px-Hayes_300_Baud_Smartmodem_02.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/f9/Hayes_300_Baud_Smartmodem_02.jpg/440px-Hayes_300_Baud_Smartmodem_02.jpg 2x" data-file-width="2469" data-file-height="915" /></a><figcaption>The original 300-baud Hayes Smartmodem</figcaption></figure> <div class="mw-heading mw-heading4"><h4 id="1980s">1980s</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=8" title="Edit section: 1980s"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A significant advance in modems was the <a href="/wiki/Hayes_Microcomputer_Products#The_Smartmodem" title="Hayes Microcomputer Products">Hayes Smartmodem</a>, introduced in 1981. The Smartmodem was an otherwise standard 103A 300 bit/s direct-connect modem, but it introduced a command language which allowed the computer to make control requests, such as commands to dial or answer calls, over the same RS-232 interface used for the data connection.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> The command set used by this device became a de facto standard, the <a href="/wiki/Hayes_command_set" class="mw-redirect" title="Hayes command set">Hayes command set</a>, which was integrated into devices from many other manufacturers. </p><p>Automatic dialing was not a new capability—it had been available via separate <a href="#Automatic_Calling_Units_/_Dialers">Automatic Calling Units</a>, and via modems using the <a href="/wiki/X.21" title="X.21">X.21</a> interface<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup>—but the Smartmodem made it available in a single device that could be used with even the most minimal implementations of the ubiquitous RS-232 interface, making this capability accessible from virtually any system or language.<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> </p><p>The introduction of the Smartmodem made communications much simpler and more easily accessed. This provided a growing market for other vendors, who licensed the Hayes patents and competed on price or by adding features.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> This eventually led to legal action over use of the patented Hayes command language.<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>Dial modems generally remained at 300 and 1,200 bit/s (eventually becoming standards such as <a href="/wiki/ITU-T_V.21" class="mw-redirect" title="ITU-T V.21">V.21</a> and <a href="/wiki/ITU-T_V.22" class="mw-redirect" title="ITU-T V.22">V.22</a>) into the mid-1980s. </p><p>Commodore's 1982 <i>VicModem</i> for the <a href="/wiki/VIC-20" title="VIC-20">VIC-20</a> was the first modem to be sold under $100, and the first modem to sell a million units.<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> </p><p>In 1984, <a href="/wiki/ITU-T_V.22bis" class="mw-redirect" title="ITU-T V.22bis">V.22bis</a> was created, a 2,400-bit/s system similar in concept to the 1,200-bit/s Bell 212. This bit rate increase was achieved by defining four or sixteen distinct symbols, which allowed the encoding of two or four bits per symbol instead of only one. By the late 1980s, many modems could support improved standards like this, and 2,400-bit/s operation was becoming common. </p><p>Increasing modem speed greatly improved the responsiveness of online systems and made <a href="/wiki/File_transfer" title="File transfer">file transfer</a> practical. This led to rapid growth of <a href="/wiki/Online_service" class="mw-redirect" title="Online service">online services</a> with large file libraries, which in turn gave more reason to own a modem. The rapid update of modems led to a similar rapid increase in BBS use. </p><p>The introduction of <a href="/wiki/Microcomputer" title="Microcomputer">microcomputer</a> systems with internal <a href="/wiki/Expansion_slot" class="mw-redirect" title="Expansion slot">expansion slots</a> made small internal modems practical. This led to a series of popular modems for the <a href="/wiki/S-100_bus" title="S-100 bus">S-100 bus</a> and <a href="/wiki/Apple_II" title="Apple II">Apple II</a> computers that could directly dial out, answer incoming calls, and hang up entirely from software, the basic requirements of a <a href="/wiki/Bulletin_board_system" title="Bulletin board system">bulletin board system</a> (BBS). The seminal <a href="/wiki/CBBS" title="CBBS">CBBS</a> for instance was created on an S-100 machine with a Hayes internal modem, and a number of similar systems followed. </p><p><a href="/wiki/Echo_cancellation#Modems" class="mw-redirect" title="Echo cancellation">Echo cancellation</a> became a feature of modems in this period, which allowed both modems to ignore their own reflected signals. This way both modems can simultaneously transmit and receive over the full spectrum of the phone line, improving the available bandwidth.<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> </p><p>Additional improvements were introduced by <a href="/wiki/Quadrature_amplitude_modulation" title="Quadrature amplitude modulation">quadrature amplitude modulation</a> (QAM) encoding, which increased the number of bits per symbol to four through a combination of phase shift and amplitude. </p><p>Transmitting at 1,200 baud produced the 4,800 bit/s <a href="/wiki/V.27ter" class="mw-redirect" title="V.27ter">V.27ter</a> standard, and at 2,400 baud the 9,600 bit/s <a href="/wiki/ITU-T_V.32" class="mw-redirect" title="ITU-T V.32">V.32</a>. The <a href="/wiki/Carrier_frequency" class="mw-redirect" title="Carrier frequency">carrier frequency</a> was 1,650 Hz in both systems. </p><p>The introduction of these higher-speed systems also led to the development of the digital <a href="/wiki/Fax" title="Fax">fax</a> machine during the 1980s. While early fax technology also used modulated signals on a phone line, digital fax used the now-standard digital encoding used by computer modems. This eventually allowed computers to send and receive fax images. </p> <div class="mw-heading mw-heading4"><h4 id="1990s">1990s</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=9" title="Edit section: 1990s"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Fax_modem_antigo.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/3/38/Fax_modem_antigo.jpg/220px-Fax_modem_antigo.jpg" decoding="async" width="220" height="133" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/38/Fax_modem_antigo.jpg/330px-Fax_modem_antigo.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/38/Fax_modem_antigo.jpg/440px-Fax_modem_antigo.jpg 2x" data-file-width="3029" data-file-height="1838" /></a><figcaption><a href="/wiki/USRobotics" title="USRobotics">USRobotics</a> Sportster 14,400 Fax Modem (1994)</figcaption></figure> <p>In the early 1990s, V.32 modems operating at 9,600 bit/s were introduced, but were expensive and were only starting to enter the market when V.32bis was standardized, which operated at 14,400 bit/s. </p><p><a href="/wiki/Rockwell_International" title="Rockwell International">Rockwell International</a>'s chip division developed a new driver chip set incorporating the <a href="/wiki/V.32bis" class="mw-redirect" title="V.32bis">V.32bis</a> standard and aggressively priced it. <a href="/wiki/Supra,_Inc." class="mw-redirect" title="Supra, Inc.">Supra, Inc.</a> arranged a short-term exclusivity arrangement with Rockwell, and developed the <a href="/wiki/SupraFAXModem_14400" title="SupraFAXModem 14400">SupraFAXModem 14400</a> based on it. Introduced in January 1992 at <span style="white-space: nowrap">$399</span> (or less), it was half the price of the slower V.32 modems already on the market. This led to a price war, and by the end of the year V.32 was dead, never having been really established, and V.32bis modems were widely available for <span style="white-space: nowrap">$250</span>. </p><p>V.32bis was so successful that the older high-speed standards had little advantages. USRobotics (USR) fought back with a 16,800 bit/s version of HST, while AT&T introduced a one-off 19,200 bit/s method they referred to as <i>V.32ter</i>, but neither non-standard modem sold well. </p> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:ModemISAv34.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7c/ModemISAv34.jpg/170px-ModemISAv34.jpg" decoding="async" width="170" height="227" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7c/ModemISAv34.jpg/255px-ModemISAv34.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7c/ModemISAv34.jpg/340px-ModemISAv34.jpg 2x" data-file-width="1944" data-file-height="2592" /></a><figcaption>V.34 modem implemented as an internal <a href="/wiki/Industry_Standard_Architecture" title="Industry Standard Architecture">ISA</a> card</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:IBM_PCMCIA_Data-Fax_Modem_V.34_FRU_42H4326-8920.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/2b/IBM_PCMCIA_Data-Fax_Modem_V.34_FRU_42H4326-8920.jpg/170px-IBM_PCMCIA_Data-Fax_Modem_V.34_FRU_42H4326-8920.jpg" decoding="async" width="170" height="170" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/2b/IBM_PCMCIA_Data-Fax_Modem_V.34_FRU_42H4326-8920.jpg/255px-IBM_PCMCIA_Data-Fax_Modem_V.34_FRU_42H4326-8920.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/2b/IBM_PCMCIA_Data-Fax_Modem_V.34_FRU_42H4326-8920.jpg/340px-IBM_PCMCIA_Data-Fax_Modem_V.34_FRU_42H4326-8920.jpg 2x" data-file-width="3318" data-file-height="3318" /></a><figcaption>V.34 data/fax modem as <a href="/wiki/PC_card" class="mw-redirect" title="PC card">PC card</a> for <a href="/wiki/Notebook_Computer" class="mw-redirect" title="Notebook Computer">notebooks</a></figcaption></figure> <style data-mw-deduplicate="TemplateStyles:r1273380762/mw-parser-output/.tmulti">.mw-parser-output .tmulti .multiimageinner{display:flex;flex-direction:column}.mw-parser-output .tmulti .trow{display:flex;flex-direction:row;clear:left;flex-wrap:wrap;width:100%;box-sizing:border-box}.mw-parser-output .tmulti .tsingle{margin:1px;float:left}.mw-parser-output .tmulti .theader{clear:both;font-weight:bold;text-align:center;align-self:center;background-color:transparent;width:100%}.mw-parser-output .tmulti .thumbcaption{background-color:transparent}.mw-parser-output .tmulti .text-align-left{text-align:left}.mw-parser-output .tmulti .text-align-right{text-align:right}.mw-parser-output .tmulti .text-align-center{text-align:center}@media all and (max-width:720px){.mw-parser-output .tmulti .thumbinner{width:100%!important;box-sizing:border-box;max-width:none!important;align-items:center}.mw-parser-output .tmulti .trow{justify-content:center}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:100%!important;box-sizing:border-box;text-align:center}.mw-parser-output .tmulti .tsingle .thumbcaption{text-align:left}.mw-parser-output .tmulti .trow>.thumbcaption{text-align:center}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}</style><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:308px;max-width:308px"><div class="trow"><div class="tsingle" style="width:152px;max-width:152px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Dr._Neuhaus,_Smarty_28.8_TI-8923.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ef/Dr._Neuhaus%2C_Smarty_28.8_TI-8923.jpg/150px-Dr._Neuhaus%2C_Smarty_28.8_TI-8923.jpg" decoding="async" width="150" height="99" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ef/Dr._Neuhaus%2C_Smarty_28.8_TI-8923.jpg/225px-Dr._Neuhaus%2C_Smarty_28.8_TI-8923.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ef/Dr._Neuhaus%2C_Smarty_28.8_TI-8923.jpg/300px-Dr._Neuhaus%2C_Smarty_28.8_TI-8923.jpg 2x" data-file-width="4368" data-file-height="2882" /></a></span></div></div><div class="tsingle" style="width:152px;max-width:152px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Dr._Neuhaus,_Smarty_28.8_TI-8924.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/2/21/Dr._Neuhaus%2C_Smarty_28.8_TI-8924.jpg/150px-Dr._Neuhaus%2C_Smarty_28.8_TI-8924.jpg" decoding="async" width="150" height="98" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/21/Dr._Neuhaus%2C_Smarty_28.8_TI-8924.jpg/225px-Dr._Neuhaus%2C_Smarty_28.8_TI-8924.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/21/Dr._Neuhaus%2C_Smarty_28.8_TI-8924.jpg/300px-Dr._Neuhaus%2C_Smarty_28.8_TI-8924.jpg 2x" data-file-width="4236" data-file-height="2759" /></a></span></div></div></div><div class="trow" style="display:flex"><div class="thumbcaption">External V.34 modem with <a href="/wiki/RS-232" title="RS-232">RS-232</a> <a href="/wiki/Serial_port" title="Serial port">serial port</a></div></div></div></div> <p>Consumer interest in these proprietary improvements waned during the lengthy introduction of the <span class="nowrap"><span data-sort-value="7004288000000000000♠"></span>28,800 bit/s</span> <a href="/wiki/ITU-T_V.34" class="mw-redirect" title="ITU-T V.34">V.34</a> standard. While waiting, several companies decided to release hardware and introduced modems they referred to as <a href="/wiki/V.Fast" class="mw-redirect" title="V.Fast">V.Fast</a>. </p><p>In order to guarantee compatibility with V.34 modems once a standard was ratified (1994), manufacturers used more flexible components, generally a <a href="/wiki/Digital_signal_processor" title="Digital signal processor">DSP</a> and <a href="/wiki/Microcontroller" title="Microcontroller">microcontroller</a>, as opposed to purpose-designed <a href="/wiki/Application-specific_integrated_circuit" title="Application-specific integrated circuit">ASIC</a> modem chips. This would allow later firmware updates to conform with the standards once ratified. </p><p>The ITU standard V.34 represents the culmination of these joint efforts. It employed the most powerful coding techniques available at the time, including channel encoding and shape encoding. From the mere four bits per symbol (<span class="nowrap"><span data-sort-value="7003960000000000000♠"></span>9.6 <a href="/wiki/Kilobit_per_second" class="mw-redirect" title="Kilobit per second">kbit/s</a></span>), the new standards used the functional equivalent of 6 to 10 bits per symbol, plus increasing baud rates from 2,400 to 3,429, to create 14.4, 28.8, and <span class="nowrap"><span data-sort-value="7004336000000000000♠"></span>33.6 kbit/s</span> modems. This rate is near the theoretical <a href="/wiki/Shannon_limit" class="mw-redirect" title="Shannon limit">Shannon limit</a> of a phone line.<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> </p> <div class="mw-heading mw-heading5"><h5 id="56_kbit/s_technologies"><span id="56_kbit.2Fs_technologies"></span><span class="anchor" id="56k"></span> <span class="nowrap"><span data-sort-value="7004560000000000000♠"></span>56 kbit/s</span> technologies</h5><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=10" title="Edit section: 56 kbit/s technologies"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>While <span class="nowrap"><span data-sort-value="7004560000000000000♠"></span>56 kbit/s</span> speeds had been available for leased-line modems for some time, they did not become available for dial up modems until the late 1990s. </p> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Modem-bank-1.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Modem-bank-1.jpg/100px-Modem-bank-1.jpg" decoding="async" width="100" height="218" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Modem-bank-1.jpg/150px-Modem-bank-1.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Modem-bank-1.jpg/200px-Modem-bank-1.jpg 2x" data-file-width="469" data-file-height="1024" /></a><figcaption>Dial-up modem bank at an ISP</figcaption></figure> <p>In the late 1990s, technologies to achieve speeds above <span class="nowrap"><span data-sort-value="7004336000000000000♠"></span>33.6 kbit/s</span> began to be introduced. Several approaches were used, but all of them began as solutions to a single fundamental problem with phone lines. </p><p>By the time technology companies began to investigate speeds above <span class="nowrap"><span data-sort-value="7004336000000000000♠"></span>33.6 kbit/s</span>, telephone companies had switched almost entirely to all-digital networks. As soon as a phone line reached a local central office, a <i>line card</i> converted the analog signal from the subscriber to a digital one and conversely. While digitally encoded telephone lines notionally provide the same bandwidth as the analog systems they replaced, the digitization itself placed constraints on the <i>types</i> of waveforms that could be reliably encoded. </p><p>The first problem was that the process of analog-to-digital conversion is intrinsically lossy, but second, and more importantly, the digital signals used by the telcos were not "linear": they did not encode all frequencies the same way, instead utilizing a nonlinear encoding (<a href="/wiki/%CE%9C-law_algorithm" title="Μ-law algorithm">μ-law</a> and <a href="/wiki/A-law_algorithm" title="A-law algorithm">a-law</a>) meant to favor the nonlinear response of the human ear to voice signals. This made it very difficult to find a <span class="nowrap"><span data-sort-value="7004560000000000000♠"></span>56 kbit/s</span> encoding that could survive the digitizing process. </p><p>Modem manufacturers discovered that, while the analog to digital conversion could not preserve higher speeds, <i>digital-to-analog</i> conversions could. Because it was possible for an ISP to obtain a direct digital connection to a telco, a <i>digital modem</i> –  one that connects directly to a digital telephone network interface, such as T1 or PRI –  could send a signal that utilized every bit of bandwidth available in the system. While that signal still had to be converted back to analog at the subscriber end, that conversion would not distort the signal in the same way that the opposite direction did. </p> <div class="mw-heading mw-heading6"><h6 id="Early_56k_dial-up_products"><span class="anchor" id="X2"></span><span class="anchor" id="K56flex"></span> Early 56k dial-up products</h6><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=11" title="Edit section: Early 56k dial-up products"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The first 56k (56 kbit/s) dial-up option was a proprietary design from <a href="/wiki/USRobotics" title="USRobotics">USRobotics</a>, which they called "X2" because 56k was twice the speed (×2) of 28k modems. </p><p>At that time, USRobotics held a 40% share of the retail modem market, while Rockwell International held an 80% share of the modem <a href="/wiki/Chipset" title="Chipset">chipset</a> market. Concerned with being shut out, Rockwell began work on a rival 56k technology. They joined with <a href="/wiki/Lucent" class="mw-redirect" title="Lucent">Lucent</a> and <a href="/wiki/Motorola" title="Motorola">Motorola</a> to develop what they called "K56Flex" or just "Flex". </p><p>Both technologies reached the market around February 1997; although problems with K56Flex modems were noted in product reviews through July, within six months the two technologies worked equally well, with variations dependent largely on local connection characteristics.<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> </p><p>The retail price of these early 56k modems was about <span style="white-space: nowrap">US$200</span>, compared to <span style="white-space: nowrap">$100</span> for standard 33k modems. Compatible equipment was also required at the <a href="/wiki/Internet_service_provider" title="Internet service provider">Internet service providers</a> (ISPs) end, with costs varying depending on whether their current equipment could be upgraded. About half of all ISPs offered 56k support by October 1997. Consumer sales were relatively low, which USRobotics and Rockwell attributed to conflicting standards.<sup id="cite_ref-GS2006_23-0" class="reference"><a href="#cite_note-GS2006-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading6"><h6 id="Standardized_56k_(V.90/V.92)"><span id="Standardized_56k_.28V.90.2FV.92.29"></span>Standardized 56k (V.90/V.92)</h6><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=12" title="Edit section: Standardized 56k (V.90/V.92)"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In February 1998, The <a href="/wiki/International_Telecommunication_Union" title="International Telecommunication Union">International Telecommunication Union</a> (ITU) announced the draft of a new <span class="nowrap"><span data-sort-value="7004560000000000000♠"></span>56 kbit/s</span> standard <a href="/wiki/ITU-T_V.90" class="mw-redirect" title="ITU-T V.90">V.90</a> with strong industry support. Incompatible with either existing standard, it was an amalgam of both, but was designed to allow both types of modem by a firmware upgrade. The V.90 standard was approved in September 1998 and widely adopted by ISPs and consumers.<sup id="cite_ref-GS2006_23-1" class="reference"><a href="#cite_note-GS2006-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> </p><p>The <a href="/wiki/ITU-T_V.92" title="ITU-T V.92">ITU-T V.92</a> standard was approved by ITU in November 2000<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> and utilized digital <a href="/wiki/Pulse-code_modulation" title="Pulse-code modulation">PCM</a> technology to increase the upload speed to a maximum of <span class="nowrap"><span data-sort-value="7004480000000000000♠"></span>48 kbit/s</span>. </p><p>The high upload speed was a tradeoff. Use of the <span class="nowrap"><span data-sort-value="7004480000000000000♠"></span>48 kbit/s</span> upstream rate would reduce the downstream as low as <span class="nowrap"><span data-sort-value="7004400000000000000♠"></span>40 kbit/s</span> due to echo effects on the line. To avoid this problem, V.92 modems offer the option to turn off the digital upstream and instead use a plain 33.<span class="nowrap"><span data-sort-value="7003600000000000000♠"></span>6 kbit/s</span> analog connection in order to maintain a high digital downstream of <span class="nowrap"><span data-sort-value="7004500000000000000♠"></span>50 kbit/s</span> or higher.<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> </p><p>V.92 also added two other features. The first is the ability for users who have call waiting to put their <a href="/wiki/Dial-up_Internet" class="mw-redirect" title="Dial-up Internet">dial-up Internet</a> connection on hold for extended periods of time while they answer a call. The second feature is the ability to quickly connect to one's ISP, achieved by remembering the analog and digital characteristics of the telephone line and using this saved information when reconnecting. </p> <div class="mw-heading mw-heading3"><h3 id="Evolution_of_dial-up_speeds">Evolution of dial-up speeds</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=13" title="Edit section: Evolution of dial-up speeds"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>These values are maximum values, and actual values may be slower under certain conditions (for example, noisy phone lines).<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> For a complete list see the companion article <i><a href="/wiki/List_of_device_bandwidths" class="mw-redirect" title="List of device bandwidths">list of device bandwidths</a></i>. A <a href="/wiki/Baud" title="Baud">baud</a> is one symbol per second; each symbol may encode one or more data bits. </p> <table class="wikitable"> <tbody><tr> <th style="text-align:left;">Connection</th> <th><a href="/wiki/Modulation" title="Modulation">Modulation</a></th> <th><a href="/wiki/Bit_rate" title="Bit rate">Bit rate</a> [kbit/s]</th> <th>Year released </th></tr> <tr> <td>110 <a href="/wiki/Baud" title="Baud">baud</a> <a href="/wiki/Bell_101" title="Bell 101">Bell 101</a> modem</td> <td>FSK</td> <td>0.1</td> <td>1958 </td></tr> <tr> <td>300 baud (<a href="/wiki/Bell_103" title="Bell 103">Bell 103</a> or <a href="/wiki/ITU-T_V.21" class="mw-redirect" title="ITU-T V.21">V.21</a>)</td> <td>FSK</td> <td>0.3</td> <td>1962 </td></tr> <tr> <td>1,200 bit/s (1200 baud) (<a href="/wiki/Bell_202" title="Bell 202">Bell 202</a>)</td> <td>FSK</td> <td>1.2</td> <td>1976 </td></tr> <tr> <td>1,200 bit/s (600 baud) (<a href="/wiki/Bell_212A" title="Bell 212A">Bell 212A</a> or <a href="/wiki/ITU-T_V.22" class="mw-redirect" title="ITU-T V.22">V.22</a>)</td> <td>QPSK</td> <td>1.2</td> <td>1980<sup id="cite_ref-tldp-mod_28-0" class="reference"><a href="#cite_note-tldp-mod-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-29" class="reference"><a href="#cite_note-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td>2,000 bit/s (1000 baud) (Bell 201A)</td> <td>PSK</td> <td>2.0</td> <td>1962 </td></tr> <tr> <td>2,400 bit/s (600 baud) (<a href="/wiki/ITU-T_V.22bis" class="mw-redirect" title="ITU-T V.22bis">V.22bis</a>)</td> <td>QAM</td> <td>2.4</td> <td>1984<sup id="cite_ref-tldp-mod_28-1" class="reference"><a href="#cite_note-tldp-mod-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td>2,400 bit/s (1200 baud) (<a href="/w/index.php?title=ITU-T_V.26bis&action=edit&redlink=1" class="new" title="ITU-T V.26bis (page does not exist)">V.26bis</a>)</td> <td>PSK</td> <td>2.4</td> <td> </td></tr> <tr> <td>4,800 bit/s (1600 baud) (<a href="/wiki/ITU-T_V.27ter" class="mw-redirect" title="ITU-T V.27ter">V.27ter</a>)</td> <td>PSK</td> <td>4.8</td> <td>1976<sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-31" class="reference"><a href="#cite_note-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td>4,800 bit/s (1600 baud, Bell 208B)</td> <td>DPSK</td> <td>4.8</td> <td> </td></tr> <tr> <td>9,600 bit/s (2400 baud) (<a href="/wiki/ITU-T_V.32" class="mw-redirect" title="ITU-T V.32">V.32</a>)</td> <td><a href="/wiki/Trellis_coded_modulation" title="Trellis coded modulation">trellis</a></td> <td>9.6</td> <td>1984<sup id="cite_ref-tldp-mod_28-2" class="reference"><a href="#cite_note-tldp-mod-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td>14.4 kbit/s (2400 baud) (<a href="/wiki/ITU-T_V.32" class="mw-redirect" title="ITU-T V.32">V.32bis</a>)</td> <td>trellis</td> <td>14.4</td> <td>1991<sup id="cite_ref-tldp-mod_28-3" class="reference"><a href="#cite_note-tldp-mod-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td>19.2 kbit/s (2400 baud) (<a href="/wiki/V.32terbo" class="mw-redirect" title="V.32terbo">V.32terbo</a>)</td> <td>trellis</td> <td>19.2</td> <td>1993<sup id="cite_ref-tldp-mod_28-4" class="reference"><a href="#cite_note-tldp-mod-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td>28.8 kbit/s (3200 baud) (<a href="/wiki/ITU-T_V.34" class="mw-redirect" title="ITU-T V.34">V.34</a>)</td> <td>trellis</td> <td>28.8</td> <td>1994<sup id="cite_ref-tldp-mod_28-5" class="reference"><a href="#cite_note-tldp-mod-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td>33.6 kbit/s (3429 baud) (<a href="/wiki/ITU-T_V.34" class="mw-redirect" title="ITU-T V.34">V.34</a>)</td> <td>trellis</td> <td>33.6</td> <td>1996<sup id="cite_ref-32" class="reference"><a href="#cite_note-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td>56 kbit/s (8000/3429 baud) (<a href="/wiki/ITU-T_V.90" class="mw-redirect" title="ITU-T V.90">V.90</a>)</td> <td>digital</td> <td>56.0/33.6</td> <td>1998<sup id="cite_ref-tldp-mod_28-6" class="reference"><a href="#cite_note-tldp-mod-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td>56 kbit/s (8000/8000 baud) (<a href="/wiki/ITU-T_V.92" title="ITU-T V.92">V.92</a>)</td> <td>digital</td> <td>56.0/48.0</td> <td>2000<sup id="cite_ref-tldp-mod_28-7" class="reference"><a href="#cite_note-tldp-mod-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td>Bonding modem (two 56k modems) (<a href="/wiki/ITU-T_V.92" title="ITU-T V.92">V.92</a>)<sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup></td> <td></td> <td>112.0/96.0</td> <td> </td></tr> <tr> <td>Hardware compression (variable) (<a href="/wiki/ITU-T_V.90" class="mw-redirect" title="ITU-T V.90">V.90</a>/<a href="/wiki/ITU-T_V.42bis" class="mw-redirect" title="ITU-T V.42bis">V.42bis</a>)</td> <td></td> <td>56.0–220.0</td> <td> </td></tr> <tr> <td>Hardware compression (variable) (<a href="/wiki/ITU-T_V.92" title="ITU-T V.92">V.92</a>/<a href="/wiki/ITU-T_V.44" class="mw-redirect" title="ITU-T V.44">V.44</a>)</td> <td></td> <td>56.0–320.0</td> <td> </td></tr> <tr> <td>Server-side web compression (variable) (<a href="/wiki/Netscape#Netscape_Internet_Service" title="Netscape">Netscape ISP</a>)</td> <td></td> <td>100.0–1,000.0</td> <td> </td></tr></tbody></table> <div class="mw-heading mw-heading3"><h3 id="Compression">Compression</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=14" title="Edit section: Compression"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Many dial-up modems implement standards for <a href="/wiki/Data_compression" title="Data compression">data compression</a> to achieve higher effective throughput for the same bitrate. <a href="/wiki/ITU-T_V.44" class="mw-redirect" title="ITU-T V.44">V.44</a><sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> is an example used in conjunction with <a href="/wiki/ITU-T_V.92" title="ITU-T V.92">V.92</a> to achieve speeds greater than 56k over ordinary phone lines.<sup id="cite_ref-35" class="reference"><a href="#cite_note-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> </p><p>As telephone-based 56k modems began losing popularity, some Internet service providers such as <a href="/wiki/NetZero" title="NetZero">Netzero</a>/Juno, <a href="/wiki/Netscape" title="Netscape">Netscape</a>, and others started using pre-compression to increase apparent throughput. This server-side compression can operate much more efficiently than the on-the-fly compression performed within modems, because the compression techniques are content-specific (JPEG, text, EXE, etc.).The drawback is a loss in quality, as they use <a href="/wiki/Lossy_compression" title="Lossy compression">lossy compression</a> which causes images to become pixelated and smeared. ISPs employing this approach often advertised it as "accelerated dial-up".<sup id="cite_ref-36" class="reference"><a href="#cite_note-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> </p><p>These accelerated downloads are integrated into the <a href="/wiki/Opera_(web_browser)" title="Opera (web browser)">Opera</a><sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup> and <a href="/wiki/Amazon_Silk" title="Amazon Silk">Amazon Silk</a><sup id="cite_ref-:1_38-0" class="reference"><a href="#cite_note-:1-38"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup> web browsers, using their own server-side text and image compression requiring all data to pass through their own servers before reaching the user.<sup id="cite_ref-:1_38-1" class="reference"><a href="#cite_note-:1-38"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Methods_of_attachment">Methods of attachment</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=15" title="Edit section: Methods of attachment"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Dial-up modems can attach in two different ways: with an acoustic coupler, or with a direct electrical connection. </p> <div class="mw-heading mw-heading4"><h4 id="Directly_connected_modems">Directly connected modems</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=16" title="Edit section: Directly connected modems"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The case <i><a href="/wiki/Hush-A-Phone_Corp._v._United_States" title="Hush-A-Phone Corp. v. United States">Hush-A-Phone Corp. v. United States</a></i>, which legalized acoustic couplers, applied only to mechanical connections to a telephone set, not electrical connections to the telephone line. The <i><a href="/wiki/Carterfone" title="Carterfone">Carterfone</a></i> decision of 1968, however, permitted customers to attach devices directly to a telephone line as long as they followed stringent Bell-defined standards for non-interference with the phone network.<sup id="cite_ref-:0_39-0" class="reference"><a href="#cite_note-:0-39"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup> This opened the door to independent (non-AT&T) manufacture of direct-connect modems, that plugged directly into the phone line rather than via an acoustic coupler. </p><p>While <i>Carterfone</i> required AT&T to permit connection of devices, AT&T successfully argued that they should be allowed to require the use of a special device to protect their network, placed in between the third-party modem and the line, called a <a href="/w/index.php?title=Data_Access_Arrangement&action=edit&redlink=1" class="new" title="Data Access Arrangement (page does not exist)">Data Access Arrangement</a> or DAA. The use of DAAs was mandatory from 1969 to 1975 when the new FCC Part 68 rules allowed the use of devices without a Bell-provided DAA, subject to equivalent circuitry being included in the third-party device.<sup id="cite_ref-40" class="reference"><a href="#cite_note-40"><span class="cite-bracket">[</span>40<span class="cite-bracket">]</span></a></sup> </p><p>Virtually all modems produced after the 1980s are direct-connect. </p> <div class="mw-heading mw-heading4"><h4 id="Acoustic_couplers">Acoustic couplers</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=17" title="Edit section: Acoustic couplers"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable selfref">See also: <a href="/wiki/Acoustic_coupler" title="Acoustic coupler">Acoustic coupler</a></div><figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Acoustic_coupler_20041015_175456_1.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7c/Acoustic_coupler_20041015_175456_1.jpg/220px-Acoustic_coupler_20041015_175456_1.jpg" decoding="async" width="220" height="168" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7c/Acoustic_coupler_20041015_175456_1.jpg/330px-Acoustic_coupler_20041015_175456_1.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7c/Acoustic_coupler_20041015_175456_1.jpg/440px-Acoustic_coupler_20041015_175456_1.jpg 2x" data-file-width="1542" data-file-height="1178" /></a><figcaption>The <i>Novation CAT</i> acoustically coupled modem</figcaption></figure> <p>While Bell (AT&T) provided modems that attached via direct wire connection to the phone network as early as 1958, their regulations at the time did not permit the direct electrical connection of any non-Bell device to a telephone line. However, the <a href="/wiki/Hush-A-Phone_Corp._v._United_States" title="Hush-A-Phone Corp. v. United States">Hush-a-Phone ruling</a> allowed customers to attach any device <i>to a telephone set</i> as long as it did not interfere with its functionality. This allowed third-party (non-Bell) manufacturers to sell modems utilizing an <i>acoustic coupler</i>.<sup id="cite_ref-:0_39-1" class="reference"><a href="#cite_note-:0-39"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup> </p><p>With an acoustic coupler, an ordinary telephone handset was placed in a cradle containing a speaker and microphone positioned to match up with those on the handset. The tones used by the modem were transmitted and received into the handset, which then relayed them to the phone line.<sup id="cite_ref-41" class="reference"><a href="#cite_note-41"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup> </p><p>Because the modem was not electrically connected, it was incapable of picking up, hanging up or dialing, all of which required direct control of the line. Touch-tone dialing would have been possible, but touch-tone was not universally available at this time. Consequently, the dialing process was executed by the user lifting the handset, dialing, then placing the handset on the coupler. To accelerate this process, a user could purchase a <i>dialer</i> or <i>Automatic Calling Unit</i>. </p> <div class="mw-heading mw-heading3"><h3 id="Automatic_calling_units">Automatic calling units</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=18" title="Edit section: Automatic calling units"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Early modems could not place or receive calls on their own, but required human intervention for these steps. </p><p>As early as 1964, Bell provided automatic calling units that connected separately to a second serial port on a host machine and could be commanded to open the line, dial a number, and even ensure the far end had successfully connected before transferring control to the modem.<sup id="cite_ref-42" class="reference"><a href="#cite_note-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup> Later on, third-party models would become available, sometimes known simply as <i>dialers</i>, and features such as the ability to automatically sign in to time-sharing systems.<sup id="cite_ref-43" class="reference"><a href="#cite_note-43"><span class="cite-bracket">[</span>43<span class="cite-bracket">]</span></a></sup> </p><p>Eventually this capability would be built into modems and no longer require a separate device. </p> <div class="mw-heading mw-heading3"><h3 id="Controller-based_modems_vs._soft_modems">Controller-based modems vs. soft modems</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=19" title="Edit section: Controller-based modems vs. soft modems"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Softmodem" title="Softmodem">Softmodem</a></div><figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:WinmodemAndRegularModem.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/58/WinmodemAndRegularModem.jpg/220px-WinmodemAndRegularModem.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/58/WinmodemAndRegularModem.jpg/330px-WinmodemAndRegularModem.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/58/WinmodemAndRegularModem.jpg/440px-WinmodemAndRegularModem.jpg 2x" data-file-width="2592" data-file-height="1944" /></a><figcaption>A PCI Winmodem soft modem (on the left) next to a conventional ISA modem (on the right)</figcaption></figure> <p>Prior to the 1990s, modems contained all the electronics and intelligence to convert data in discrete form to an analog (modulated) signal and back again, and to handle the dialing process, as a mix of discrete logic and special-purpose chips. This type of modem is sometimes referred to as <i>controller-based</i>.<sup id="cite_ref-44" class="reference"><a href="#cite_note-44"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup> </p><p>In 1993, Digicom introduced the <i>Connection 96 Plus</i>, a modem which replaced the discrete and custom components with a general purpose digital signal processor, which could be reprogrammed to upgrade to newer standards.<sup id="cite_ref-45" class="reference"><a href="#cite_note-45"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup> </p><p>Subsequently, USRobotics released the <i>Sportster Winmodem</i>, a similarly upgradable DSP-based design.<sup id="cite_ref-46" class="reference"><a href="#cite_note-46"><span class="cite-bracket">[</span>46<span class="cite-bracket">]</span></a></sup> </p><p>As this design trend spread, both terms – <i>soft modem</i> and <i>Winmodem</i> – obtained a negative connotation in non-Windows-based computing circles because the drivers were either unavailable for non-Windows platforms, or were only available as unmaintainable closed-source binaries, a particular problem for Linux users.<sup id="cite_ref-47" class="reference"><a href="#cite_note-47"><span class="cite-bracket">[</span>47<span class="cite-bracket">]</span></a></sup> </p><p>Later in the 1990s, software-based modems became available. These are essentially sound cards, and in fact a common design uses the <a href="/wiki/AC%2797" title="AC'97">AC'97</a> audio codec, which provides multichannel audio to a PC and includes three audio channels for modem signals. </p><p>The audio sent and received on the line by a modem of this type is generated and processed entirely in software, often in a device driver. There is little functional difference from the user's perspective, but this design reduces the cost of a modem by moving most of the processing power into inexpensive software instead of expensive hardware <a href="/wiki/Digital_signal_processor" title="Digital signal processor">DSPs</a> or discrete components. </p><p>Soft modems of both types either are internal cards or connect over external buses such as <a href="/wiki/USB" title="USB">USB</a>. They never utilize RS-232 because they require high bandwidth channels to the host computers to carry the raw audio signals generated (sent) or analyzed (received) by software. </p><p>Since the interface is not RS-232, there is no standard for communication with the device directly. Instead, soft modems come with drivers which create an emulated RS-232 port, which standard modem software (such as an operating system dialer application) can communicate with. </p> <div class="mw-heading mw-heading3"><h3 id="Voice/fax_modems"><span id="Voice.2Ffax_modems"></span>Voice/fax modems</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=20" title="Edit section: Voice/fax modems"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>"Voice" and "fax" are terms added to describe any dial modem that is capable of recording/playing audio or transmitting/receiving faxes. Some modems are capable of all three functions.<sup id="cite_ref-48" class="reference"><a href="#cite_note-48"><span class="cite-bracket">[</span>48<span class="cite-bracket">]</span></a></sup> </p><p><a href="/wiki/Voice_modem_command_set" title="Voice modem command set">Voice modems</a> are used for <a href="/wiki/Computer_telephony_integration" title="Computer telephony integration">computer telephony integration</a> applications as simple as placing/receiving calls directly through a computer with a headset, and as complex as fully automated <a href="/wiki/Robocall" title="Robocall">robocalling</a> systems. </p><p>Fax modems can be used for computer-based faxing, in which faxes are sent and received without inbound or outbound faxes ever needing to ever be printed on paper. This differs from <a href="/wiki/Internet_fax" title="Internet fax">efax</a>, in which faxing occurs over the internet, in some cases involving no phone lines whatsoever. </p> <div class="mw-heading mw-heading3"><h3 id="Modem_Over_IP_(Modem_Relay)"><span id="Modem_Over_IP_.28Modem_Relay.29"></span>Modem Over IP (Modem Relay)</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=21" title="Edit section: Modem Over IP (Modem Relay)"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The ITU-T V.150.1 Recommendation defines procedures for the inter-operation of PSTN to IP gateways.<sup id="cite_ref-49" class="reference"><a href="#cite_note-49"><span class="cite-bracket">[</span>49<span class="cite-bracket">]</span></a></sup> In a classic example of this setup, each dial-up modem would connect to a modem relay gateway. The gateways are then connected to an IP network (such as the Internet). The analog connection from the modem is terminated at the gateway and the signal is demodulated. The demodulated control signals are transported over the IP network in an <a href="/wiki/Real-time_Transport_Protocol" title="Real-time Transport Protocol">RTP</a> packet type defined as <a href="/w/index.php?title=State_Signaling_Events&action=edit&redlink=1" class="new" title="State Signaling Events (page does not exist)">State Signaling Events</a> (SSEs). The data from the demodulated signal is sent over the IP network via a transport protocol (also defined as an RTP payload) called <a href="/w/index.php?title=Simple_Packet_Relay_Transport&action=edit&redlink=1" class="new" title="Simple Packet Relay Transport (page does not exist)">Simple Packet Relay Transport</a> (SPRT). Both the SSE and SPRT packet formats are defined in the V.150.1 Recommendation (Annex C and Annex B respectively). The gateway at the remote end that receives the packets uses the information to re-modulate the signal for the modem connected at that end. </p><p>While the V.150.1 Recommendation is not widely deployed, a pared down version of the recommendation called "Minimum Essential Requirements (MER) for V.150.1 Gateways" (SCIP-216) is used in <a href="/wiki/Secure_telephone" title="Secure telephone">Secure Telephony</a> applications.<sup id="cite_ref-50" class="reference"><a href="#cite_note-50"><span class="cite-bracket">[</span>50<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Cloud-based_Modems">Cloud-based Modems</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=22" title="Edit section: Cloud-based Modems"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>While traditionally a hardware device, fully software-based modems with the ability to be deployed in a cloud environment (such as <a href="/wiki/Microsoft_Azure" title="Microsoft Azure">Microsoft Azure</a> or <a href="/wiki/Amazon_Web_Services" title="Amazon Web Services">AWS</a>) do exist.<sup id="cite_ref-51" class="reference"><a href="#cite_note-51"><span class="cite-bracket">[</span>51<span class="cite-bracket">]</span></a></sup> Leveraging a <a href="/wiki/Voice_over_IP" title="Voice over IP">Voice-over-IP</a> (VoIP) connection through a <a href="/wiki/SIP_trunking" title="SIP trunking">SIP Trunk</a>, the modulated audio samples are generated and sent over an IP network via <a href="/wiki/Real-time_Transport_Protocol" title="Real-time Transport Protocol">RTP</a> and an uncompressed audio codec (such as <a href="/wiki/G.711" title="G.711">G.711</a> μ-law or a-law). </p> <div class="mw-heading mw-heading3"><h3 id="Popularity">Popularity</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=23" title="Edit section: Popularity"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A 1994 <a href="/wiki/Software_Publishers_Association" class="mw-redirect" title="Software Publishers Association">Software Publishers Association</a> found that although 60% of computers in US households had a modem, only 7% of households went online.<sup id="cite_ref-cgw199405_52-0" class="reference"><a href="#cite_note-cgw199405-52"><span class="cite-bracket">[</span>52<span class="cite-bracket">]</span></a></sup> A <a href="/wiki/Consumer_Electronics_Association" class="mw-redirect" title="Consumer Electronics Association">CEA</a> study in 2006 found that dial-up Internet access was declining in the US. In 2000, dial-up Internet connections accounted for 74% of all US residential Internet connections.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (May 2013)">citation needed</span></a></i>]</sup> The United States demographic pattern for dial-up modem users per capita has been more or less mirrored in Canada and Australia for the past 20 years. </p><p>Dial-up modem use in the US had dropped to 60% by 2003, and stood at 36% in 2006.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (May 2013)">citation needed</span></a></i>]</sup> Voiceband modems were once the most popular means of <a href="/wiki/Internet" title="Internet">Internet</a> access in the US, but with the advent of new ways of accessing the Internet, the traditional 56K modem was losing popularity. The dial-up modem is still widely used by customers in rural areas where DSL, cable, wireless broadband, satellite, or fiber optic service are either not available or they are unwilling to pay what the available broadband companies charge.<sup id="cite_ref-53" class="reference"><a href="#cite_note-53"><span class="cite-bracket">[</span>53<span class="cite-bracket">]</span></a></sup> In its 2012 annual report, <a href="/wiki/AOL" title="AOL">AOL</a> showed it still collected around $700 million in fees from about three million dial-up users. </p> <div class="mw-heading mw-heading3"><h3 id="TTY/TDD"><span id="TTY.2FTDD"></span>TTY/TDD</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=24" title="Edit section: TTY/TDD"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Telecommunications_device_for_the_deaf" title="Telecommunications device for the deaf">TDD</a> devices are a subset of the <a href="/wiki/Teleprinter" title="Teleprinter">teleprinter</a> intended for use by the deaf or hard of hearing, essentially a small teletype with a built-in dial-up modem and acoustic coupler. The first models produced in 1964 utilized <a href="/wiki/Frequency-shift_keying" title="Frequency-shift keying">FSK</a> modulation much like early computer modems. </p> <div class="mw-heading mw-heading2"><h2 id="Leased-line_modems">Leased-line modems</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=25" title="Edit section: Leased-line modems"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A <a href="/wiki/Leased_line" title="Leased line">leased line</a> modem also uses ordinary phone wiring, like dial-up and DSL, but does not use the same network topology. While dial-up uses a normal phone line and connects through the telephone switching system, and DSL uses a normal phone line but connects to equipment at the telco central office, leased lines do not terminate at the telco. </p><p>Leased lines are pairs of telephone wire that have been connected together at one or more telco central offices so that they form a continuous circuit between two subscriber locations, such as a business' headquarters and a satellite office. They provide no power or dialtone - they are simply a pair of wires connected at two distant locations. </p><p>A dialup modem will not function across this type of line, because it does not provide the power, dialtone and switching that those modems require. However, a modem with leased-line capability can operate over such a line, and in fact can have greater performance because the line is not passing through the telco switching equipment, the signal is not filtered, and therefore greater bandwidth is available. </p><p>Leased-line modems can operate in 2-wire or 4-wire mode. The former uses a single pair of wires and can only transmit in one direction at a time, while the latter uses two pairs of wires and can transmit in both directions simultaneously. When two pairs are available, bandwidth can be as high as 1.5 Mbit/s, a full data <a href="/wiki/T1_line" class="mw-redirect" title="T1 line">T1</a> circuit.<sup id="cite_ref-54" class="reference"><a href="#cite_note-54"><span class="cite-bracket">[</span>54<span class="cite-bracket">]</span></a></sup> </p><p>While the slower leased line modems used, e.g., <a href="/wiki/RS-232" title="RS-232">RS-232</a>, interfaces, the faster wideband modems used, e.g., <a href="/wiki/List_of_ITU-T_V-series_recommendations#Wideband_modems" title="List of ITU-T V-series recommendations">V.35</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Broadband">Broadband</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=26" title="Edit section: Broadband"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:T-DSL_Modem.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5f/T-DSL_Modem.jpg/220px-T-DSL_Modem.jpg" decoding="async" width="220" height="216" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5f/T-DSL_Modem.jpg/330px-T-DSL_Modem.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/5f/T-DSL_Modem.jpg/440px-T-DSL_Modem.jpg 2x" data-file-width="2032" data-file-height="1992" /></a><figcaption><a href="/wiki/DSL_modem" title="DSL modem">DSL modem</a></figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:ARRIS_CM820B_DOCSIS_Cable_Modem.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/19/ARRIS_CM820B_DOCSIS_Cable_Modem.jpg/220px-ARRIS_CM820B_DOCSIS_Cable_Modem.jpg" decoding="async" width="220" height="138" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/19/ARRIS_CM820B_DOCSIS_Cable_Modem.jpg/330px-ARRIS_CM820B_DOCSIS_Cable_Modem.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/19/ARRIS_CM820B_DOCSIS_Cable_Modem.jpg/440px-ARRIS_CM820B_DOCSIS_Cable_Modem.jpg 2x" data-file-width="3883" data-file-height="2429" /></a><figcaption>Cable modem</figcaption></figure> <p>The term <i><a href="/wiki/Broadband" title="Broadband">broadband</a></i> was previously<sup id="cite_ref-55" class="reference"><a href="#cite_note-55"><span class="cite-bracket">[</span>55<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-56" class="reference"><a href="#cite_note-56"><span class="cite-bracket">[</span>56<span class="cite-bracket">]</span></a></sup> used to describe communications faster than what was available on voice grade channels. </p><p>The term <i><a href="/wiki/Broadband" title="Broadband">broadband</a></i> gained widespread adoption in the late 1990s to describe internet access technology exceeding the 56 kilobit/s maximum of dialup. There are many broadband technologies, such as various DSL (<a href="/wiki/Digital_subscriber_line" title="Digital subscriber line">digital subscriber line</a>) technologies and cable broadband. </p><p>DSL technologies such as <a href="/wiki/Asymmetric_digital_subscriber_line" class="mw-redirect" title="Asymmetric digital subscriber line">ADSL</a>, <a href="/wiki/High-bit-rate_digital_subscriber_line" title="High-bit-rate digital subscriber line">HDSL</a>, and <a href="/wiki/VDSL" title="VDSL">VDSL</a> use telephone lines (wires that were installed by a telephone company and originally intended for use by a telephone subscriber) but do not utilize most of the rest of the telephone system. Their signals are not sent through ordinary phone exchanges, but are instead received by special equipment (a <a href="/wiki/Digital_subscriber_line_access_multiplexer" class="mw-redirect" title="Digital subscriber line access multiplexer">DSLAM</a>) at the telephone company central office. </p><p>Because the signal does not pass through the telephone exchange, no "dialing" is required, and the bandwidth constraints of an ordinary voice call are not imposed. This allows much higher frequencies, and therefore much faster speeds. ADSL in particular is designed to permit voice calls and data usage over the same line simultaneously. </p><p>Similarly, <a href="/wiki/Cable_modem" title="Cable modem">cable modems</a> use infrastructure originally intended to carry television signals, and like DSL, typically permit receiving television signals at the same time as broadband internet service. </p><p>Other broadband modems include <a href="/wiki/FTTx" class="mw-redirect" title="FTTx">FTTx</a> modems, <a href="/wiki/Satellite_modem" title="Satellite modem">satellite modems</a>, and <a href="/wiki/Power_line_communication" class="mw-redirect" title="Power line communication">power line</a> modems. </p> <div class="mw-heading mw-heading3"><h3 id="Terminology">Terminology</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=27" title="Edit section: Terminology"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Different terms are used for broadband modems, because they frequently contain more than just a modulation/demodulation component. </p><p>Because high-speed connections are frequently used by multiple computers at once, many broadband modems do not have direct (e.g. USB) PC connections. Rather they connect over a network such as Ethernet or Wi-Fi. Early broadband modems offered <a href="/wiki/Ethernet" title="Ethernet">Ethernet</a> handoff allowing the use of one or more public IP addresses, but no other services such as NAT and DHCP that would allow multiple computers to share one connection. This led to many consumers purchasing separate "broadband routers," placed between the modem and their network, to perform these functions.<sup id="cite_ref-57" class="reference"><a href="#cite_note-57"><span class="cite-bracket">[</span>57<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-58" class="reference"><a href="#cite_note-58"><span class="cite-bracket">[</span>58<span class="cite-bracket">]</span></a></sup> </p><p>Eventually, ISPs began providing <a href="/wiki/Residential_gateway" title="Residential gateway">residential gateways</a> which combined the modem and broadband router into a single package that provided routing, <a href="/wiki/Network_address_translation" title="Network address translation">NAT</a>, security features, and even <a href="/wiki/Wi-Fi" title="Wi-Fi">Wi-Fi</a> access in addition to modem functionality, so that subscribers could connect their entire household without purchasing any extra equipment. Even later, these devices were extended to provide "<a href="/wiki/Triple_play_(telecommunications)" title="Triple play (telecommunications)">triple play</a>" features such as telephony and television service. Nonetheless, these devices are still often referred to simply as "modems" by service providers and manufacturers.<sup id="cite_ref-59" class="reference"><a href="#cite_note-59"><span class="cite-bracket">[</span>59<span class="cite-bracket">]</span></a></sup> </p><p>Consequently, the terms "modem", "router", and "gateway" are now used interchangeably in casual speech, but in a technical context "modem" may carry a specific connotation of basic functionality with no routing or other features, while the others describe a device with features such as NAT.<sup id="cite_ref-60" class="reference"><a href="#cite_note-60"><span class="cite-bracket">[</span>60<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-61" class="reference"><a href="#cite_note-61"><span class="cite-bracket">[</span>61<span class="cite-bracket">]</span></a></sup> </p><p>Broadband modems may also handle authentication such as <a href="/wiki/Point-to-Point_Protocol_over_Ethernet" title="Point-to-Point Protocol over Ethernet">PPPoE</a>. While it is often possible to authenticate a broadband connection from a users PC, as was the case with dial-up internet service, moving this task to the broadband modem allows it to establish and maintain the connection itself, which makes sharing access between PCs easier since each one does not have to authenticate separately. Broadband modems typically remain authenticated to the ISP as long as they are powered on. </p> <div class="mw-heading mw-heading2"><h2 id="Radio">Radio</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=28" title="Edit section: Radio"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-Unreferenced_section plainlinks metadata ambox ambox-content ambox-Unreferenced" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This section <b>does not <a href="/wiki/Wikipedia:Citing_sources" title="Wikipedia:Citing sources">cite</a> any <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">sources</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/Modem" title="Special:EditPage/Modem">improve this section</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a>. Unsourced material may be challenged and <a href="/wiki/Wikipedia:Verifiability#Burden_of_evidence" title="Wikipedia:Verifiability">removed</a>.</span> <span class="date-container"><i>(<span class="date">October 2017</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Espressif_ESP-WROOM-32_Wi-Fi_%26_Bluetooth_Module.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/3/33/Espressif_ESP-WROOM-32_Wi-Fi_%26_Bluetooth_Module.jpg/220px-Espressif_ESP-WROOM-32_Wi-Fi_%26_Bluetooth_Module.jpg" decoding="async" width="220" height="220" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/33/Espressif_ESP-WROOM-32_Wi-Fi_%26_Bluetooth_Module.jpg/330px-Espressif_ESP-WROOM-32_Wi-Fi_%26_Bluetooth_Module.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/33/Espressif_ESP-WROOM-32_Wi-Fi_%26_Bluetooth_Module.jpg/440px-Espressif_ESP-WROOM-32_Wi-Fi_%26_Bluetooth_Module.jpg 2x" data-file-width="800" data-file-height="800" /></a><figcaption>A bluetooth radio module with built-in antenna (left)</figcaption></figure> <p>Any communication technology sending digital data wirelessly involves a modem. This includes <a href="/wiki/Direct_broadcast_satellite" class="mw-redirect" title="Direct broadcast satellite">direct broadcast satellite</a>, <a href="/wiki/WiFi" class="mw-redirect" title="WiFi">WiFi</a>, <a href="/wiki/WiMAX" title="WiMAX">WiMax</a>, <a href="/wiki/Mobile_phone" title="Mobile phone">mobile phones</a>, <a href="/wiki/Global_Positioning_System" title="Global Positioning System">GPS</a>, <a href="/wiki/Bluetooth" title="Bluetooth">Bluetooth</a> and <a href="/wiki/Near-field_communication" title="Near-field communication">NFC</a>. </p><p>Modern telecommunications and data networks also make extensive use of <a href="/wiki/Radio_modem" title="Radio modem">radio modems</a> where long distance data links are required. Such systems are an important part of the <a href="/wiki/PSTN" class="mw-redirect" title="PSTN">PSTN</a>, and are also in common use for high-speed <a href="/wiki/Computer_networking" class="mw-redirect" title="Computer networking">computer network</a> links to outlying areas where <a href="/wiki/Fiber-optic_communication" title="Fiber-optic communication">fiber optic</a> is not economical. </p><p>Wireless modems come in a variety of types, bandwidths, and speeds. Wireless modems are often referred to as transparent or smart. They transmit information that is modulated onto a carrier frequency to allow many wireless communication links to work simultaneously on different frequencies.<sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Writing_better_articles#Stay_on_topic" title="Wikipedia:Writing better articles"><span title="The near this tag may contain information that is not relevant to the article's main topic. I don't recognize any of this terminology and from a little googling I suspect it is too low-level for this consumer-electronics-oriented article. (August 2020)">relevant?</span></a></i>]</sup> </p><p>Transparent modems operate in a manner similar to their phone line modem cousins. Typically, they were <a href="/wiki/Half_duplex" class="mw-redirect" title="Half duplex">half duplex</a>, meaning that they could not send and receive data at the same time. Typically, transparent modems are polled in a round robin manner to collect small amounts of data from scattered locations that do not have easy access to wired infrastructure. Transparent modems are most commonly used by utility companies for data collection. </p><p>Smart modems come with media access controllers inside, which prevents random data from colliding and resends data that is not correctly received. Smart modems typically require more bandwidth than transparent modems, and typically achieve higher data rates. The IEEE <a href="/wiki/802.11" class="mw-redirect" title="802.11">802.11</a> standard defines a short range modulation scheme that is used on a large scale throughout the world. </p> <div class="mw-heading mw-heading3"><h3 id="Mobile_broadband">Mobile broadband</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=29" title="Edit section: Mobile broadband"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/Mobile_broadband" title="Mobile broadband">Mobile broadband</a> and <a href="/wiki/Mobile_broadband_modem" title="Mobile broadband modem">Mobile broadband modem</a></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Huawei_E173_3G_HSPA%2B_Modem_USB_Movistar_Colombia_(6).jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/0/08/Huawei_E173_3G_HSPA%2B_Modem_USB_Movistar_Colombia_%286%29.jpg/110px-Huawei_E173_3G_HSPA%2B_Modem_USB_Movistar_Colombia_%286%29.jpg" decoding="async" width="110" height="107" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/08/Huawei_E173_3G_HSPA%2B_Modem_USB_Movistar_Colombia_%286%29.jpg/165px-Huawei_E173_3G_HSPA%2B_Modem_USB_Movistar_Colombia_%286%29.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/08/Huawei_E173_3G_HSPA%2B_Modem_USB_Movistar_Colombia_%286%29.jpg/220px-Huawei_E173_3G_HSPA%2B_Modem_USB_Movistar_Colombia_%286%29.jpg 2x" data-file-width="2404" data-file-height="2337" /></a><figcaption><a href="/wiki/Huawei" title="Huawei">Huawei</a> <a href="/wiki/HSPA%2B" class="mw-redirect" title="HSPA+">HSPA+</a> (<a href="/wiki/Evolution-Data_Optimized" title="Evolution-Data Optimized">EVDO</a>) USB wireless modem from <a href="/wiki/Movistar" title="Movistar">Movistar</a> Colombia</figcaption></figure> <figure class="mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Huawei_4G%2B_Modem.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ea/Huawei_4G%2B_Modem.jpg/110px-Huawei_4G%2B_Modem.jpg" decoding="async" width="110" height="127" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ea/Huawei_4G%2B_Modem.jpg/166px-Huawei_4G%2B_Modem.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ea/Huawei_4G%2B_Modem.jpg/221px-Huawei_4G%2B_Modem.jpg 2x" data-file-width="2777" data-file-height="3196" /></a><figcaption>Huawei 4G+ Dual Band Modem</figcaption></figure> <p>Modems which use a mobile telephone system (<a href="/wiki/GPRS" class="mw-redirect" title="GPRS">GPRS</a>, <a href="/wiki/UMTS" title="UMTS">UMTS</a>, <a href="/wiki/High_Speed_Packet_Access" title="High Speed Packet Access">HSPA</a>, <a href="/wiki/Evolution-Data_Optimized" title="Evolution-Data Optimized">EVDO</a>, <a href="/wiki/WiMAX" title="WiMAX">WiMax</a>, <a href="/wiki/5G" title="5G">5G</a> etc.), are known as mobile broadband modems (sometimes also called wireless modems). Wireless modems can be embedded inside a <a href="/wiki/Laptop" title="Laptop">laptop</a>, mobile phone or other device, or be connected externally. External wireless modems include <a href="/wiki/Connect_card" class="mw-redirect" title="Connect card">connect cards</a>, USB modems, and <a href="/wiki/Cellular_router" class="mw-redirect" title="Cellular router">cellular routers</a>. </p><p>Most <a href="/wiki/GSM" title="GSM">GSM</a> wireless modems come with an integrated <a href="/wiki/SIM_card" title="SIM card">SIM cardholder</a> (i.e. <a href="/wiki/Huawei_E220" title="Huawei E220">Huawei E220</a>, Sierra 881.) Some models are also provided with a microSD memory slot and/or jack for additional external antenna, (Huawei E1762, Sierra Compass 885.)<sup id="cite_ref-62" class="reference"><a href="#cite_note-62"><span class="cite-bracket">[</span>62<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-63" class="reference"><a href="#cite_note-63"><span class="cite-bracket">[</span>63<span class="cite-bracket">]</span></a></sup> </p><p>The CDMA (EVDO) versions do not typically use <a href="/wiki/Removable_User_Identity_Module" title="Removable User Identity Module">R-UIM</a> cards, but use <a href="/wiki/Electronic_Serial_Number" class="mw-redirect" title="Electronic Serial Number">Electronic Serial Number</a> (ESN) instead. </p><p>Until the end of April 2011, worldwide shipments of USB modems surpassed embedded 3G and 4G modules by 3:1 because USB modems can be easily discarded. Embedded modems may overtake separate modems as tablet sales grow and the incremental cost of the modems shrinks, so by 2016, the ratio may change to 1:1.<sup id="cite_ref-64" class="reference"><a href="#cite_note-64"><span class="cite-bracket">[</span>64<span class="cite-bracket">]</span></a></sup> </p><p>Like mobile phones, mobile broadband modems can be SIM locked to a particular network provider. Unlocking a modem is achieved the same way as unlocking a phone, by using an <a href="/wiki/Subsidy_Password" title="Subsidy Password">'unlock code'</a>.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (July 2020)">citation needed</span></a></i>]</sup> </p> <div class="mw-heading mw-heading2"><h2 id="Optical_modem">Optical modem</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=30" title="Edit section: Optical modem"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Tellabs_ONT611_inside.jpeg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/b/bc/Tellabs_ONT611_inside.jpeg/220px-Tellabs_ONT611_inside.jpeg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/bc/Tellabs_ONT611_inside.jpeg/330px-Tellabs_ONT611_inside.jpeg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/bc/Tellabs_ONT611_inside.jpeg/440px-Tellabs_ONT611_inside.jpeg 2x" data-file-width="3072" data-file-height="2304" /></a><figcaption>An ONT providing data, telephone and television service</figcaption></figure> <p>A device that connects to a fiber optic network is known as an <a href="/wiki/Network_interface_device#Optical_network_terminals" title="Network interface device">optical network terminal</a> (ONT) or optical network unit (ONU). These are commonly used in <a href="/wiki/Fiber-to-the_home" class="mw-redirect" title="Fiber-to-the home">fiber to the home</a> installations, installed inside or outside a house to convert the optical medium to a copper Ethernet interface, after which a router or gateway is often installed to perform authentication, routing, NAT, and other typical consumer internet functions, in addition to "<a href="/wiki/Triple_play_(telecommunications)" title="Triple play (telecommunications)">triple play</a>" features such as telephony and television service. They are not a modem,<sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Disputed_statement" class="mw-redirect" title="Wikipedia:Disputed statement"><span title="This claim has reliable sources with contradicting facts (April 2024)">disputed</span></a> – <a href="/wiki/Talk:Modem" title="Talk:Modem">discuss</a></i>]</sup> although they perform a similar function and are sometimes referred to as a modem. </p><p>Fiber optic systems can use quadrature amplitude modulation to maximize throughput. 16QAM uses a 16-point constellation to send four bits per symbol, with speeds on the order of 200 or 400 gigabits per second.<sup id="cite_ref-65" class="reference"><a href="#cite_note-65"><span class="cite-bracket">[</span>65<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-66" class="reference"><a href="#cite_note-66"><span class="cite-bracket">[</span>66<span class="cite-bracket">]</span></a></sup> 64QAM uses a 64-point constellation to send six bits per symbol, with speeds up to 65 terabits per second. Although this technology has been announced, it may not yet be commonly used.<sup id="cite_ref-67" class="reference"><a href="#cite_note-67"><span class="cite-bracket">[</span>67<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-68" class="reference"><a href="#cite_note-68"><span class="cite-bracket">[</span>68<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-69" class="reference"><a href="#cite_note-69"><span class="cite-bracket">[</span>69<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Home_networking">Home networking</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=31" title="Edit section: Home networking"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1251242444"><table class="box-Unreferenced_section plainlinks metadata ambox ambox-content ambox-Unreferenced" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This section <b>does not <a href="/wiki/Wikipedia:Citing_sources" title="Wikipedia:Citing sources">cite</a> any <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">sources</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/Modem" title="Special:EditPage/Modem">improve this section</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a>. Unsourced material may be challenged and <a href="/wiki/Wikipedia:Verifiability#Burden_of_evidence" title="Wikipedia:Verifiability">removed</a>.</span> <span class="date-container"><i>(<span class="date">October 2017</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <p>Although the name <i>modem</i> is seldom used, some high-speed home networking applications do use modems, such as <a href="/wiki/Powerline_Ethernet" class="mw-redirect" title="Powerline Ethernet">powerline ethernet</a>. The <a href="/wiki/G.hn" title="G.hn">G.hn</a> standard for instance, developed by <a href="/wiki/ITU-T" title="ITU-T">ITU-T</a>, provides a high-speed (up to 1 Gbit/s) <a href="/wiki/Local_area_network" title="Local area network">local area network</a> using existing home wiring (power lines, phone lines, and <a href="/wiki/Ethernet_over_coax" title="Ethernet over coax">coaxial cables</a>). G.hn devices use <a href="/wiki/Orthogonal_frequency-division_multiplexing" title="Orthogonal frequency-division multiplexing">orthogonal frequency-division multiplexing</a> (OFDM) to modulate a digital signal for transmission over the wire. </p><p>As described above, technologies like Wi-Fi and Bluetooth also use modems to communicate over radio at short distances. </p> <div class="mw-heading mw-heading2"><h2 id="Null_modem">Null modem</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=32" title="Edit section: Null modem"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Null_modem.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/58/Null_modem.jpg/110px-Null_modem.jpg" decoding="async" width="110" height="115" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/58/Null_modem.jpg/165px-Null_modem.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/58/Null_modem.jpg/220px-Null_modem.jpg 2x" data-file-width="513" data-file-height="537" /></a><figcaption>Null modem adapter</figcaption></figure> <p>A <a href="/wiki/Null_modem" title="Null modem">null modem</a> cable is a specially wired cable connected between the <a href="/wiki/Serial_port" title="Serial port">serial ports</a> of two devices, with the transmit and receive lines reversed. It is used to connect two devices directly without a modem. The same software or hardware typically used with modems (such as Procomm or Minicom) could be used with this type of connection. </p><p>A null modem adapter is a small device with plugs at both ends which is placed on the termination of a normal "straight-through" serial cable to convert it into a null-modem cable. </p> <div class="mw-heading mw-heading2"><h2 id="Short-haul_modem">Short-haul modem</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=33" title="Edit section: Short-haul modem"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A "short haul modem" is a device that bridges the gap between leased-line and dial-up modems. Like a leased-line modem, they transmit over "bare" lines with no power or telco switching equipment, but are not intended for the same distances that leased lines can achieve. Ranges up to several miles are possible, but significantly, short-haul modems can be used for <i>medium</i> distances, greater than the maximum length of a basic serial cable but still relatively short, such as within a single building or campus. This allows a serial connection to be extended for perhaps only several hundred to several thousand feet, a case where obtaining an entire telephone or leased line would be overkill. </p><p>While some short-haul modems do in fact use modulation, low-end devices (for reasons of cost or power consumption) are simple "line drivers" that increase the level of the digital signal but do not modulate it. These are not technically modems, but the same terminology is used for them.<sup id="cite_ref-70" class="reference"><a href="#cite_note-70"><span class="cite-bracket">[</span>70<span class="cite-bracket">]</span></a></sup> </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=Modem&action=edit&section=34" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1184024115">.mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}</style><div class="div-col" style="column-width: 31em;"> <ul><li><a href="/wiki/56_kbit/s_line" title="56 kbit/s line">56 kbit/s line</a></li> <li><a href="/wiki/Handshake_(computing)" title="Handshake (computing)">Handshaking</a></li> <li><a href="/wiki/Raytheon_BBN" title="Raytheon BBN">Raytheon BBN</a></li> <li><a href="/wiki/Command_and_Data_modes_(modem)" class="mw-redirect" title="Command and Data modes (modem)">Command and Data modes (modem)</a></li> <li><a href="/wiki/Fax_demodulator" title="Fax demodulator">Fax demodulator</a></li> <li><a href="/wiki/List_of_interface_bit_rates" title="List of interface bit rates">List of interface bit rates</a></li> <li><a href="/wiki/List_of_ITU-T_V-series_recommendations" title="List of ITU-T V-series recommendations">List of ITU-T V-series recommendations</a></li> <li><a href="/wiki/Modulation" title="Modulation">Modulation</a></li> <li><a href="/wiki/RJ-11" class="mw-redirect" title="RJ-11">RJ-11</a></li> <li><a href="/wiki/Time_Independent_Escape_Sequence" title="Time Independent Escape Sequence">Time Independent Escape Sequence</a></li> <li><a href="/wiki/Wake-on-ring" title="Wake-on-ring">Wake-on-ring</a></li></ul></div> <div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=35" title="Edit section: Further reading"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><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://bitsavers.trailing-edge.com/pdf/datapro/Datapro_Reports_on_PC_and_LAN_Communications_1992/Vol1_570.pdf">"Modems: Market Overview"</a> <span class="cs1-format">(PDF)</span>. <i><a href="/wiki/Datapro_Research" class="mw-redirect" title="Datapro Research">Datapro Research</a></i>. Datapro Reports on PC & LAN Communications. <a href="/wiki/McGraw_Hill" class="mw-redirect" title="McGraw Hill">McGraw Hill</a>. September 1990.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Datapro+Research&rft.atitle=Modems%3A+Market+Overview&rft.date=1990-09&rft_id=https%3A%2F%2Fbitsavers.trailing-edge.com%2Fpdf%2Fdatapro%2FDatapro_Reports_on_PC_and_LAN_Communications_1992%2FVol1_570.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AModem" class="Z3988"></span></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=Modem&action=edit&section=36" 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 reflist-columns references-column-width" style="column-width: 33em;"> <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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBellis2017" class="citation web cs1">Bellis, Mary (2017-12-31). <a rel="nofollow" class="external text" href="https://www.thoughtco.com/history-of-the-modem-4077013">"History of the Modem"</a>. <i>ThoughtCo.com</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2021-04-05</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=ThoughtCo.com&rft.atitle=History+of+the+Modem&rft.date=2017-12-31&rft.aulast=Bellis&rft.aufirst=Mary&rft_id=https%3A%2F%2Fwww.thoughtco.com%2Fhistory-of-the-modem-4077013&rfr_id=info%3Asid%2Fen.wikipedia.org%3AModem" class="Z3988"></span></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.nsa.gov/about/cryptologic-heritage/historical-figures-publications/publications/wwii/sigsaly-start-digital/">"National Security Agency Central Security Service > About Us > Cryptologic Heritage > Historical Figures and Publications > Publications > WWII > Sigsaly – The Start of the Digital Revolution"</a>. <i>NSA.gov</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2020-08-13</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=NSA.gov&rft.atitle=National+Security+Agency+Central+Security+Service+%3E+About+Us+%3E+Cryptologic+Heritage+%3E+Historical+Figures+and+Publications+%3E+Publications+%3E+WWII+%3E+Sigsaly+%E2%80%93+The+Start+of+the+Digital+Revolution&rft_id=https%3A%2F%2Fwww.nsa.gov%2Fabout%2Fcryptologic-heritage%2Fhistorical-figures-publications%2Fpublications%2Fwwii%2Fsigsaly-start-digital%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AModem" 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 id="CITEREFManjoo2009" class="citation web cs1">Manjoo, Farhad (2009-02-24). <a rel="nofollow" class="external text" href="https://slate.com/technology/2009/02/the-unrecognizable-internet-of-1996.html">"The unrecognizable Internet of 1996"</a>. <i>Slate Magazine</i><span class="reference-accessdate">. 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IDG Enterprise.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Computerworld&rft.pub=IDG+Enterprise&rft.date=1981-04-27&rft.aulast=Enterprise&rft.aufirst=I.+D.+G.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DKbM9-s49yCMC%26q%3Dcomputerworld%2520hayes%2520smartmodem%25201981%26pg%3DRA1-PA42&rfr_id=info%3Asid%2Fen.wikipedia.org%3AModem" class="Z3988"></span></span> </li> <li id="cite_note-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-15">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFJennings1986" class="citation book cs1">Jennings, Fred (1986). <a rel="nofollow" class="external text" href="https://archive.org/details/practicaldatacom00jenn"><i>Practical data communications : modems, networks and protocols : Jennings, Fred : Free Download, Borrow, and Streaming</i></a>. 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Cambridge University Press. pp. <span class="nowrap">129–</span>132. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-139-46075-0" title="Special:BookSources/978-1-139-46075-0"><bdi>978-1-139-46075-0</bdi></a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20170324040643/https://books.google.com/books?id=3hMKHwUmaZ8C&pg=PA129">Archived</a> from the original on 2017-03-24.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Standards+and+Public+Policy&rft.pages=%3Cspan+class%3D%22nowrap%22%3E129-%3C%2Fspan%3E132&rft.pub=Cambridge+University+Press&rft.date=2006&rft.isbn=978-1-139-46075-0&rft.aulast=Greenstein&rft.aufirst=Shane&rft.au=Stango%2C+Victor&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3D3hMKHwUmaZ8C%26pg%3DPA129&rfr_id=info%3Asid%2Fen.wikipedia.org%3AModem" class="Z3988"></span></span> </li> <li id="cite_note-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-24">^</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="http://www.itu.int/newsarchive/press_releases/1998/04.html">"Agreement reached on 56K Modem standard"</a>. <i>International Telecommunication Union</i>. 9 February 1998. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20171002194141/http://www.itu.int/newsarchive/press_releases/1998/04.html">Archived</a> from the original on 2 October 2017<span class="reference-accessdate">. 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Retrieved <span class="nowrap">April 1,</span> 2022</span>. <q>Analog channels can be further characterized by bandwidth: narrowband channels (for example, 100 Hz, 200 Hz); voiceband channels (4 kHz);4 broadband channels (for example, 48 kHz, 240 kHz).</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=6.2.1+Basic+Concept&rft.btitle=Engineering+and+Operations+in+the+Bell+System&rft.pages=199&rft.edition=Second&rft.pub=AT%26T+Bell+Laboratories&rft.date=1984&rft_id=info%3Alccn%2F83-72956&rft.isbn=0-932764-04-5&rft_id=http%3A%2F%2Fbitsavers.org%2Fcommunications%2FwesternElectric%2Fbooks%2FEngineering_and_Operations_in_the_Bell_System_2ed_1984.pdf%23page%3D215&rfr_id=info%3Asid%2Fen.wikipedia.org%3AModem" class="Z3988"></span></span> </li> <li id="cite_note-57"><span class="mw-cite-backlink"><b><a href="#cite_ref-57">^</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://www.lifewire.com/difference-between-modem-and-router-4159854">"What's the Difference between a Modem and Router?"</a>. <i>Lifewire</i><span class="reference-accessdate">. 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Retrieved <span class="nowrap">2021-11-23</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Wirecutter%3A+Reviews+for+the+Real+World&rft.atitle=Modem+vs.+Router%3A+What%27s+the+Difference%3F&rft.date=2021-02-11&rft_id=https%3A%2F%2Fwww.nytimes.com%2Fwirecutter%2Fblog%2Fmodem-vs-router%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AModem" class="Z3988"></span></span> </li> <li id="cite_note-61"><span class="mw-cite-backlink"><b><a href="#cite_ref-61">^</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://www.xfinity.com/hub/internet/modem-vs-router">"Modem vs Router: What's the Difference?"</a>. <i>Xfinity</i><span class="reference-accessdate">. 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The Register. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20130104002944/http://www.reghardware.com/2008/07/16/review_sierra_compass_885/">Archived</a> from the original on 2013-01-04<span class="reference-accessdate">. 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IDG Consumer & SMB. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20160927225258/http://www.pcworld.com/article/226887/article.html">Archived</a> from the original on September 27, 2016<span class="reference-accessdate">. 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Optical Society of America: B784-9. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2011OExpr..19B.784O">2011OExpr..19B.784O</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1364%2Foe.19.00b784">10.1364/oe.19.00b784</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/22274103">22274103</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:32757398">32757398</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Optics+Express&rft.atitle=112+Gbit%2Fs+RF-assisted+dual+carrier+DP-16-QAM+transmitter+using+optical+phase+modulator&rft.volume=19&rft.issue=26&rft.pages=B784-9&rft.date=2011-12-06&rft_id=info%3Adoi%2F10.1364%2Foe.19.00b784&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A32757398%23id-name%3DS2CID&rft_id=info%3Apmid%2F22274103&rft_id=info%3Abibcode%2F2011OExpr..19B.784O&rft.au=Bengt-Erik+Olsson&rft.au=Anders+Djupsj%C3%B6backa&rft.au=Jonas+M%C3%A5rtensson&rft.au=Arne+Alping&rft_id=https%3A%2F%2Fdoi.org%2F10.1364%252Foe.19.00b784&rfr_id=info%3Asid%2Fen.wikipedia.org%3AModem" class="Z3988"></span></span> </li> <li id="cite_note-67"><span class="mw-cite-backlink"><b><a href="#cite_ref-67">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFStephen_Hardy2016" class="citation web cs1">Stephen Hardy (March 17, 2016). <a rel="nofollow" class="external text" href="http://www.lightwaveonline.com/articles/2016/03/clariphy-targets-400g-with-new-16-nm-dsp-silicon.html">"ClariPhy targets 400G with new 16-nm DSP silicon"</a>. LIGHTWAVE. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20161109085339/http://www.lightwaveonline.com/articles/2016/03/clariphy-targets-400g-with-new-16-nm-dsp-silicon.html">Archived</a> from the original on November 9, 2016.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=ClariPhy+targets+400G+with+new+16-nm+DSP+silicon&rft.pub=LIGHTWAVE&rft.date=2016-03-17&rft.au=Stephen+Hardy&rft_id=http%3A%2F%2Fwww.lightwaveonline.com%2Farticles%2F2016%2F03%2Fclariphy-targets-400g-with-new-16-nm-dsp-silicon.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AModem" class="Z3988"></span></span> </li> <li id="cite_note-68"><span class="mw-cite-backlink"><b><a href="#cite_ref-68">^</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="http://optics.org/press/3152">"ClariPhy Shatters Fiber and System Capacity Barriers with Industry's First 16nm Coherent Optical Networking Platform"</a>. <i>optics.org</i>. 17 Mar 2016.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=optics.org&rft.atitle=ClariPhy+Shatters+Fiber+and+System+Capacity+Barriers+with+Industry%27s+First+16nm+Coherent+Optical+Networking+Platform&rft.date=2016-03-17&rft_id=http%3A%2F%2Foptics.org%2Fpress%2F3152&rfr_id=info%3Asid%2Fen.wikipedia.org%3AModem" class="Z3988"></span></span> </li> <li id="cite_note-69"><span class="mw-cite-backlink"><b><a href="#cite_ref-69">^</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://web.archive.org/web/20161109090213/http://company.nokia.com/en/news/press-releases/2016/10/12/alcatel-lucent-submarine-networks-and-nokia-bell-labs-achieve-65-terabit-per-second-transmission-record-for-transoceanic-cable-systems">"Nokia Bell Labs achieve 65 Terabit-per-second transmission record for transoceanic cable systems"</a>. Noika. 12 October 2016. Archived from <a rel="nofollow" class="external text" href="http://company.nokia.com/en/news/press-releases/2016/10/12/alcatel-lucent-submarine-networks-and-nokia-bell-labs-achieve-65-terabit-per-second-transmission-record-for-transoceanic-cable-systems">the original</a> on 9 November 2016<span class="reference-accessdate">. Retrieved <span class="nowrap">8 November</span> 2016</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Nokia+Bell+Labs+achieve+65+Terabit-per-second+transmission+record+for+transoceanic+cable+systems&rft.pub=Noika&rft.date=2016-10-12&rft_id=http%3A%2F%2Fcompany.nokia.com%2Fen%2Fnews%2Fpress-releases%2F2016%2F10%2F12%2Falcatel-lucent-submarine-networks-and-nokia-bell-labs-achieve-65-terabit-per-second-transmission-record-for-transoceanic-cable-systems&rfr_id=info%3Asid%2Fen.wikipedia.org%3AModem" class="Z3988"></span></span> </li> <li id="cite_note-70"><span class="mw-cite-backlink"><b><a href="#cite_ref-70">^</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="http://www.trine2.net.au/Modem-Tutorial(YES!)/modem.htm#Short_Haul">"Modem"</a>. <i>www.trine2.net.au</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2020-08-13</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.trine2.net.au&rft.atitle=Modem&rft_id=http%3A%2F%2Fwww.trine2.net.au%2FModem-Tutorial%28YES%21%29%2Fmodem.htm%23Short_Haul&rfr_id=info%3Asid%2Fen.wikipedia.org%3AModem" class="Z3988"></span></span> </li> </ol></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Modem&action=edit&section=37" title="Edit section: External links"><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 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srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/Wikibooks-logo-en-noslogan.svg/60px-Wikibooks-logo-en-noslogan.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/df/Wikibooks-logo-en-noslogan.svg/80px-Wikibooks-logo-en-noslogan.svg.png 2x" data-file-width="400" data-file-height="400" /></a></span></div> <div class="side-box-text plainlist">Wikibooks has a book on the topic of: <i><b><a href="https://en.wikibooks.org/wiki/Transferring_Data_between_Standard_Dial-Up_Modems" class="extiw" title="wikibooks:Transferring Data between Standard Dial-Up Modems">Transferring Data between Standard Dial-Up Modems</a></b></i></div></div> </div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1235681985"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1237033735"><div class="side-box side-box-right plainlinks sistersitebox"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Commons-logo.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png" decoding="async" width="30" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/45px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/59px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376" /></a></span></div> <div class="side-box-text plainlist">Wikimedia Commons has media related to <span style="font-weight: bold; font-style: italic;"><a href="https://commons.wikimedia.org/wiki/Category:Modems" class="extiw" title="commons:Category:Modems">Modems</a></span>.</div></div> </div> <ul><li><a href="https://en.wikibooks.org/wiki/Serial_Programming/Modems_and_AT_Commands" class="extiw" title="b:Serial Programming/Modems and AT Commands">Hayes-compatible Modems and AT Commands</a> from the <a href="https://en.wikibooks.org/wiki/Serial_Programming" class="extiw" title="b:Serial Programming">Serial Data Communications Programming</a> <i><a href="/wiki/Wikibook" class="mw-redirect" title="Wikibook">Wikibook</a></i></li> <li><a rel="nofollow" class="external text" href="http://www.itu.int/rec/recommendation.asp?type=products&lang=e&parent=T-REC-V">International Telecommunication Union ITU</a>: Data communication over the telephone network</li> <li><a rel="nofollow" class="external text" href="http://www.3amsystems.com/wireline/hmo.htm">Basic handshakes & modulations</a> – V.22, V.22bis, V.32 and V.34 handshakes</li> <li><a rel="nofollow" class="external text" href="http://www.techradar.com/news/internet/getting-connected-a-history-of-modems-657479">Getting connected: a history of modems</a> – techradar</li> <li><a rel="nofollow" class="external text" href="https://www.bugswave.com/difference-between-modems-and-routers/">Difference between Modems and Routers</a> – Bugswave</li> <li><a rel="nofollow" class="external text" href="http://bitsavers.org/communications/westernElectric/books/Telecommunications_Transmission_Engineering_Vol_2_Facilities_1ed_1977.pdf">Telecommunications Transmission_Engineering Volume 2 Facilities</a> - AT&T</li> <li><a rel="nofollow" class="external text" href="https://proxy-hobbit-poland.com/en">Polish proxies made on 4G modems</a></li></ul> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1236075235">.mw-parser-output .navbox{box-sizing:border-box;border:1px solid #a2a9b1;width:100%;clear:both;font-size:88%;text-align:center;padding:1px;margin:1em auto 0}.mw-parser-output .navbox .navbox{margin-top:0}.mw-parser-output .navbox+.navbox,.mw-parser-output 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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 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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/Donald_Davies" title="Donald Davies">Donald Davies</a></li> <li><a href="/wiki/Daniel_Davis_Jr." title="Daniel Davis Jr.">Daniel Davis Jr.</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/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/Lee_de_Forest" title="Lee de Forest">Lee de Forest</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/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</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> <li><i><a href="/wiki/List_of_Internet_pioneers" title="List of Internet pioneers">Internet pioneers</a></i></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/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" class="mw-redirect" 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/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/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/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><i><a href="/wiki/List_of_telecommunications_regulatory_bodies" title="List of telecommunications regulatory bodies">Global telecommunications regulation bodies</a></i></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><span class="nowrap"><span class="noviewer" typeof="mw:File"><span><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, 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