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<div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Transmission of data at irregular intervals</div> <p>In <a href="/wiki/Telecommunications" title="Telecommunications">telecommunications</a>, <b>asynchronous communication</b> is <a href="/wiki/Data_communication" title="Data communication">transmission of data</a>, generally without the use of an external <a href="/wiki/Clock_signal" title="Clock signal">clock signal</a>, where data can be transmitted intermittently rather than in a steady stream.<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> Any timing required to recover data from the communication symbols is encoded within the symbols. </p><p>The most significant aspect of asynchronous communications is that data is not transmitted at regular intervals, thus making possible <a href="/wiki/Variable_bit_rate" class="mw-redirect" title="Variable bit rate">variable bit rate</a>, and that the transmitter and receiver <a href="/wiki/Clock_generator" title="Clock generator">clock generators</a> do not have to be exactly synchronized all the time. In asynchronous transmission, data is sent one <a href="/wiki/Byte" title="Byte">byte</a> at a time and each byte is preceded by <a href="/wiki/Asynchronous_serial_communication" title="Asynchronous serial communication">start and stop bits</a>. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Physical_layer">Physical layer</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Asynchronous_communication&action=edit&section=1" title="Edit section: Physical layer"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Asynchronous_serial_communication" title="Asynchronous serial communication">Asynchronous serial communication</a></div> <p>In <a href="/wiki/Asynchronous_serial_communication" title="Asynchronous serial communication">asynchronous serial communication</a> in the <a href="/wiki/Physical_protocol_layer" class="mw-redirect" title="Physical protocol layer">physical protocol layer</a>, the data blocks are code words of a certain <a href="/wiki/Word_length" class="mw-redirect" title="Word length">word length</a>, for example <a href="/wiki/Octet_(computing)" title="Octet (computing)">octets</a> (<a href="/wiki/Bytes" class="mw-redirect" title="Bytes">bytes</a>) or <a href="/wiki/ASCII_characters" class="mw-redirect" title="ASCII characters">ASCII characters</a>, <a href="/wiki/Delimited" class="mw-redirect" title="Delimited">delimited</a> by start bits and stop bits. A variable length space can be inserted between the code words. No bit synchronization signal is required. This is sometimes called <a href="/w/index.php?title=Character_oriented_communication&action=edit&redlink=1" class="new" title="Character oriented communication (page does not exist)">character oriented communication</a>. Examples include <a href="/w/index.php?title=MNP2&action=edit&redlink=1" class="new" title="MNP2 (page does not exist)">MNP2</a> and modems older than <a href="/wiki/ITU-T_V.2" class="mw-redirect" title="ITU-T V.2">V.2</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Data_link_layer_and_higher">Data link layer and higher</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Asynchronous_communication&action=edit&section=2" title="Edit section: Data link layer and higher"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Asynchronous communication at the <a href="/wiki/Data_link_layer" title="Data link layer">data link layer</a> or higher protocol layers is known as <a href="/wiki/Statistical_multiplexing" class="mw-redirect" title="Statistical multiplexing">statistical multiplexing</a>, for example <a href="/wiki/Asynchronous_Transfer_Mode" title="Asynchronous Transfer Mode">Asynchronous Transfer Mode</a> (ATM). In this case, the asynchronously transferred blocks are called <a href="/wiki/Data_packet" class="mw-redirect" title="Data packet">data packets</a>, for example ATM cells. The opposite is <a href="/wiki/Circuit_switching" title="Circuit switching">circuit switched</a> communication, which provides constant bit rate, for example <a href="/wiki/ISDN" title="ISDN">ISDN</a> and <a href="/wiki/SONET/SDH" class="mw-redirect" title="SONET/SDH">SONET/SDH</a>. </p><p>The packets may be encapsulated in a <a href="/wiki/Data_frame" class="mw-redirect" title="Data frame">data frame</a>, with a <a href="/wiki/Frame_synchronization" title="Frame synchronization">frame synchronization</a> bit sequence indicating the start of the frame, and sometimes also a <a href="/wiki/Bit_synchronization" class="mw-redirect" title="Bit synchronization">bit synchronization</a> bit sequence, typically 01010101, for identification of the bit transition times. Note that at the physical layer, this is considered as synchronous serial communication. Examples of packet mode data link protocols that can be/are transferred using synchronous serial communication are the <a href="/wiki/HDLC" class="mw-redirect" title="HDLC">HDLC</a>, <a href="/wiki/Ethernet" title="Ethernet">Ethernet</a>, <a href="/wiki/Point-to-point_protocol" class="mw-redirect" title="Point-to-point protocol">PPP</a> and <a href="/wiki/USB" title="USB">USB</a> protocols. </p> <div class="mw-heading mw-heading2"><h2 id="Application_layer">Application layer</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Asynchronous_communication&action=edit&section=3" title="Edit section: Application layer"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>An asynchronous communication service or application does not require a constant bit rate.<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> Examples are <a href="/wiki/File_transfer" title="File transfer">file transfer</a>, <a href="/wiki/Email" title="Email">email</a> and the <a href="/wiki/World_Wide_Web" title="World Wide Web">World Wide Web</a>. An example of the opposite, a synchronous communication service, is realtime <a href="/wiki/Streaming_media" title="Streaming media">streaming media</a>, for example <a href="/wiki/IP_telephony" class="mw-redirect" title="IP telephony">IP telephony</a>, <a href="/wiki/IPTV" class="mw-redirect" title="IPTV">IPTV</a> and <a href="/wiki/Video_conferencing" class="mw-redirect" title="Video conferencing">video conferencing</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Electronically_mediated_communication">Electronically mediated communication</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Asynchronous_communication&action=edit&section=4" title="Edit section: Electronically mediated communication"><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">Further information: <a href="/wiki/Computer-mediated_communication" title="Computer-mediated communication">Computer-mediated communication</a></div> <p>Electronically mediated communication often happens asynchronously in that the participants do not communicate concurrently. Examples include <a href="/wiki/Email" title="Email">email</a><sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> and <a href="/wiki/Bulletin-board_system" class="mw-redirect" title="Bulletin-board system">bulletin-board systems</a>, where participants send or post messages at different times than they read them. The term "asynchronous communication" acquired currency in the field of online learning, where teachers and students often exchange information asynchronously instead of synchronously (that is, simultaneously), as they would in face-to-face or in telephone conversations. </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=Asynchronous_communication&action=edit&section=5" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Synchronization_in_telecommunications" title="Synchronization in telecommunications">Synchronization in telecommunications</a></li> <li><a href="/wiki/Asynchronous_serial_communication" title="Asynchronous serial communication">Asynchronous serial communication</a></li> <li><a href="/wiki/Asynchronous_system" title="Asynchronous system">Asynchronous system</a></li> <li><a href="/wiki/Asynchronous_circuit" title="Asynchronous circuit">Asynchronous circuit</a></li> <li><a href="/wiki/Anisochronous" title="Anisochronous">Anisochronous</a></li> <li><a href="/wiki/Baud_rate" class="mw-redirect" title="Baud rate">Baud rate</a></li> <li><a href="/wiki/Plesiochronous" class="mw-redirect" title="Plesiochronous">Plesiochronous</a></li> <li><a href="/wiki/Plesiochronous_Digital_Hierarchy" class="mw-redirect" title="Plesiochronous Digital Hierarchy">Plesiochronous Digital Hierarchy</a> (PDH)</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=Asynchronous_communication&action=edit&section=6" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><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"><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 id="CITEREFBeal1996" class="citation web cs1">Beal, Vangie (September 1, 1996). <a rel="nofollow" class="external text" href="http://www.webopedia.com/TERM/A/asynchronous.html">"asynchronous"</a>. Webopedia. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110430051620/http://www.webopedia.com/TERM/A/asynchronous.html">Archived</a> from the original on 30 April 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">2011-04-27</span></span>. <q>The term asynchronous is usually used to describe communications in which data can be transmitted intermittently rather than in a steady stream.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=asynchronous&rft.pub=Webopedia&rft.date=1996-09-01&rft.aulast=Beal&rft.aufirst=Vangie&rft_id=http%3A%2F%2Fwww.webopedia.com%2FTERM%2FA%2Fasynchronous.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAsynchronous+communication" 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 id="CITEREFHargrave2001" class="citation book cs1">Hargrave, Frank (2001). <a rel="nofollow" class="external text" href="https://search.credoreference.com/"><i>Hargrave's Communication Dictionary</i></a>. Wiley.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Hargrave%27s+Communication+Dictionary&rft.pub=Wiley&rft.date=2001&rft.aulast=Hargrave&rft.aufirst=Frank&rft_id=https%3A%2F%2Fsearch.credoreference.com%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAsynchronous+communication" 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="CITEREFCalladine2006" class="citation book cs1">Calladine, Richard (2006). "A taxonomy of learning technologies: simplifying online learning for learners, professors, and designers". In Khosrowpour, Mehdi (ed.). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=ybzS-yylJfAC"><i>Emerging Trends and Challenges in Information Technology Management: 2006 Information Resources Management Association International Conference, Washington, DC, USA, May 21-24, 2006</i></a>. Vol. 1. Idea Group Inc (IGI). p. 249. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9781599040196" title="Special:BookSources/9781599040196"><bdi>9781599040196</bdi></a><span class="reference-accessdate">. Retrieved <span class="nowrap">2014-09-03</span></span>. <q>Email and Internet Chat provide a good example of the difference between synchronous and asynchronous technologies. Email is generally responded to at the discretion of the user and hence is described as asynchronous. However, when in a Chat session each participant knows that the others are waiting for their responses. The resulting "conversations" are synchronous [...]</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=A+taxonomy+of+learning+technologies%3A+simplifying+online+learning+for+learners%2C+professors%2C+and+designers&rft.btitle=Emerging+Trends+and+Challenges+in+Information+Technology+Management%3A+2006+Information+Resources+Management+Association+International+Conference%2C+Washington%2C+DC%2C+USA%2C+May+21-24%2C+2006&rft.pages=249&rft.pub=Idea+Group+Inc+%28IGI%29&rft.date=2006&rft.isbn=9781599040196&rft.aulast=Calladine&rft.aufirst=Richard&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DybzS-yylJfAC&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAsynchronous+communication" class="Z3988"></span></span> </li> </ol></div></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Asynchronous_communication&oldid=1255534413">https://en.wikipedia.org/w/index.php?title=Asynchronous_communication&oldid=1255534413</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/wiki/Category:Synchronization" title="Category:Synchronization">Synchronization</a></li><li><a href="/wiki/Category:Telecommunications_techniques" title="Category:Telecommunications techniques">Telecommunications techniques</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_is_different_from_Wikidata" title="Category:Short description is different from Wikidata">Short description is different from Wikidata</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 5 November 2024, at 12:18<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. 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