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<span class="vector-toc-numb">5</span> <span>References</span> </div> </a> <ul id="toc-References-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" > <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 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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">Sending control flow information in the same channel as data</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">For broader coverage of this topic, see <a href="/wiki/Signaling_(telecommunications)" title="Signaling (telecommunications)">Signaling (telecommunications)</a>.</div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid 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.mbox-text{padding:0!important;margin:0!important}.mw-parser-output .compact-ambox .ambox .mbox-text-span{display:list-item;line-height:1.5em;list-style-type:disc}body.skin-minerva .mw-parser-output .multiple-issues-text>.mw-collapsible-toggle,.mw-parser-output .compact-ambox .ambox .mbox-image,.mw-parser-output .compact-ambox .ambox .mbox-imageright,.mw-parser-output .compact-ambox .ambox .mbox-empty-cell,.mw-parser-output .compact-ambox .hide-when-compact{display:none}</style><table class="box-Multiple_issues plainlinks metadata ambox ambox-content ambox-multiple_issues compact-ambox" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/b/b4/Ambox_important.svg/40px-Ambox_important.svg.png" decoding="async" width="40" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/b/b4/Ambox_important.svg/60px-Ambox_important.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/b/b4/Ambox_important.svg/80px-Ambox_important.svg.png 2x" data-file-width="40" data-file-height="40" /></span></span></div></td><td class="mbox-text"><div class="mbox-text-span"><div class="multiple-issues-text mw-collapsible"><b>This article has multiple issues.</b> Please help <b><a href="/wiki/Special:EditPage/In-band_signaling" title="Special:EditPage/In-band signaling">improve it</a></b> or discuss these issues on the <b><a href="/wiki/Talk:In-band_signaling" title="Talk:In-band signaling">talk page</a></b>. <small><i>(<a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove these messages</a>)</i></small> <div class="mw-collapsible-content"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1251242444"><table class="box-More_citations_needed plainlinks metadata ambox ambox-content ambox-Refimprove" 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 article <b>needs additional citations for <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/In-band_signaling" title="Special:EditPage/In-band signaling">improve this article</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 removed.<br /><small><span class="plainlinks"><i>Find sources:</i> <a rel="nofollow" class="external text" href="https://www.google.com/search?as_eq=wikipedia&q=%22In-band+signaling%22">"In-band signaling"</a> – <a rel="nofollow" class="external text" href="https://www.google.com/search?tbm=nws&q=%22In-band+signaling%22+-wikipedia&tbs=ar:1">news</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?&q=%22In-band+signaling%22&tbs=bkt:s&tbm=bks">newspapers</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?tbs=bks:1&q=%22In-band+signaling%22+-wikipedia">books</a> <b>·</b> <a rel="nofollow" class="external text" href="https://scholar.google.com/scholar?q=%22In-band+signaling%22">scholar</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.jstor.org/action/doBasicSearch?Query=%22In-band+signaling%22&acc=on&wc=on">JSTOR</a></span></small></span> <span class="date-container"><i>(<span class="date">May 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> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1251242444"><table class="box-Expert_needed plainlinks metadata ambox ambox-content" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/b/b4/Ambox_important.svg/40px-Ambox_important.svg.png" decoding="async" width="40" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/b/b4/Ambox_important.svg/60px-Ambox_important.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/b/b4/Ambox_important.svg/80px-Ambox_important.svg.png 2x" data-file-width="40" data-file-height="40" /></span></span></div></td><td class="mbox-text"><div class="mbox-text-span">This article <b>needs attention from an expert in Telecommunications</b>. The specific problem is: <b>Too telecomm-specific, need broader theoretical perspectives..</b><span class="hide-when-compact"> <a href="/wiki/Wikipedia:WikiProject_Telecommunications" title="Wikipedia:WikiProject Telecommunications">WikiProject Telecommunications</a> may be able to help recruit an expert.</span> <span class="date-container"><i>(<span class="date">April 2017</span>)</i></span></div></td></tr></tbody></table> </div> </div><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>In <a href="/wiki/Telecommunications" title="Telecommunications">telecommunications</a>, <b>in-band signaling</b> is the sending of <a href="/wiki/Control_signal" class="mw-redirect" title="Control signal">control information</a> within the same band or channel used for data such as voice or video. This is in contrast to <a href="/wiki/Out-of-band_signal" class="mw-redirect" title="Out-of-band signal">out-of-band signaling</a> which is sent over a different channel, or even over a separate network. In-band signals may often be heard by telephony participants, while out-of-band signals are inaccessible to the user.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> The term is also used more generally, for example of computer data files that include both literal data, and <a href="/wiki/Metadata" title="Metadata">metadata</a> and/or instructions for how to process the literal data. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Telephony">Telephony</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=In-band_signaling&action=edit&section=1" title="Edit section: Telephony"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>When dialing from a land-line <a href="/wiki/Telephone" title="Telephone">telephone</a>, the <a href="/wiki/Telephone_number" title="Telephone number">telephone number</a> is encoded and transmitted across the telephone line in form of <a href="/wiki/Dual-tone_multi-frequency_signaling" class="mw-redirect" title="Dual-tone multi-frequency signaling">dual-tone multi-frequency signaling</a> (DTMF). The tones control the telephone system by instructing the <a href="/wiki/Telephone_switch" class="mw-redirect" title="Telephone switch">telephone switch</a> where to route the call. These control tones are sent over the same <a href="/wiki/Channel_(communications)" class="mw-redirect" title="Channel (communications)">channel</a>, the copper wire, and in the frequency range (300 Hz to 3.4 kHz) as the audio of the telephone call. In-band signaling is also used on older telephone carrier systems to provide <a href="/wiki/Interexchange_carrier" title="Interexchange carrier">inter-exchange</a> information for routing calls. Examples of this kind of in-band signaling system are the <a href="/wiki/Signaling_System_No._5" title="Signaling System No. 5">Signaling System No. 5</a> (SS5) and its predecessors, and <a href="/wiki/R2_signalling" class="mw-redirect" title="R2 signalling">R2 signalling</a>.<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><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><sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p>Separating the control signals, also referred to as the control plane, from the data, if a <a href="/wiki/Transparency_(telecommunication)" title="Transparency (telecommunication)">bit-transparent</a> connection is desired, is usually done by <a href="/wiki/Escape_sequence" title="Escape sequence">escaping</a> the control instructions. Occasionally, however, networks are designed so that data is, to a varying degree, garbled by the signaling. Allowing data to become garbled is usually acceptable when transmitting sounds between humans, since the users rarely notice the slight degradation, but this leads to problems when sending data that has very low error tolerance, such as information transmitted using a <a href="/wiki/Modem" title="Modem">modem</a>. </p><p>In-band signaling is insecure because it exposes control signals, protocols and management systems to <a href="/wiki/End_user" title="End user">end users</a>, which may result in <a href="/wiki/Falsing" title="Falsing">falsing</a>. In the 1960s and 1970s, so-called <i><a href="/wiki/Phreaking" title="Phreaking">phone phreaks</a></i> used <a href="/wiki/Blue_box" title="Blue box">blue boxes</a> for deliberate falsing, in which the appropriate tones for routing were intentionally generated, enabling the caller to abuse functions intended for testing and administrative use and to make free long-distance calls. </p><p>Modems may also interfere with in-band signaling, in which case a <a href="/wiki/Guard_tone" title="Guard tone">guard tone</a> may be employed to prevent this. </p> <div class="mw-heading mw-heading2"><h2 id="Voice_over_IP">Voice over IP</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=In-band_signaling&action=edit&section=2" title="Edit section: Voice over IP"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In <a href="/wiki/Voice_over_IP" title="Voice over IP">voice over IP</a> (VoIP), DTMF signals are transmitted in-band by two methods. When transmitted as audio tones in the voice stream, voice encoding must use a lossless coder, such as <a href="/wiki/%CE%9C-law" class="mw-redirect" title="Μ-law">μ-law</a> or <a href="/wiki/A-law" class="mw-redirect" title="A-law">A-law</a> <a href="/wiki/Pulse-code_modulation" title="Pulse-code modulation">pulse-code modulation</a>, to preserve the integrity of frequency signals. Still, this method proved often unreliable and was subject to interference from other audio sources. The standard method is to digitally remove DTMF tones from the audio at the source and from the <a href="/wiki/Real-time_Transport_Protocol" title="Real-time Transport Protocol">Real-time Transport Protocol</a> (RTP) voice stream and encode them separately as a digital information payload, often termed <i>named telephone events</i> (NTE), according to RFC 4733. Such DTMF frames are transmit in-band with all other RTP packets on the identical network path.<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>In contrast to in-band transmission of DTMF, VoIP signaling protocols also implement <a href="/wiki/Out-of-band" title="Out-of-band">out-of-band</a> method of DTMF transmission. For example, the <a href="/wiki/Session_Initiation_Protocol" title="Session Initiation Protocol">Session Initiation Protocol</a> (SIP), as well as the <a href="/wiki/Media_Gateway_Control_Protocol" title="Media Gateway Control Protocol">Media Gateway Control Protocol</a> (MGCP) define special message types for the transmission of digits. </p> <div class="mw-heading mw-heading2"><h2 id="Other_applications">Other applications</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=In-band_signaling&action=edit&section=3" title="Edit section: Other applications"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>As a method of in-band signaling, DTMF tones were also used by <a href="/wiki/Cable_television" title="Cable television">cable television</a> <a href="/wiki/Broadcasting" title="Broadcasting">broadcasters</a> to indicate the start and stop times of <a href="/wiki/Local_insertion" title="Local insertion">local insertion</a> points during station breaks for the benefit of cable companies. Until better, <a href="/wiki/Out-of-band_signaling" class="mw-redirect" title="Out-of-band signaling">out-of-band signaling</a> equipment was developed in the 1990s, fast, unacknowledged, and loud DTMF tone sequences could be heard during the commercial breaks of cable channels in the United States and elsewhere. </p><p>These DTMF sequences were sent by the originating cable network's equipment at the <a href="/wiki/Uplink" class="mw-redirect" title="Uplink">uplink</a> satellite facility, and were decoded by equipment at local cable companies. A specific tone sequence indicated the exact time that the feeds should be switched to and away from the master control feed, to locally-broadcast commercials. The following is an example of such a sequence by a cable company that communicated the following to the cable company's broadcast equipment: </p> <blockquote><p>SWITCH TO LOCAL NOW - SWITCH TO LOCAL NOW - PREPARE TO SWITCH BACK - PREPARE TO SWITCH BACK - SWITCH BACK TO NATIONAL NOW - SWITCH BACK TO NATIONAL NOW - "IF YOU HAVEN'T SWITCHED BACK TO NATIONAL NOW, DO SO IMMEDIATELY"</p></blockquote> <p>DTMF signaling in the cable industry was discontinued because it was distracting to viewers, and was susceptible to interference when DTMF tones were sounded by characters in television shows. For example, a character dialing a Touch-Tone telephone in a television show could cause the cable company computers to switch away from a "hot feed" to <a href="/wiki/Dead_air" title="Dead air">dead air</a>, and the cost of human-imperceptible signaling technologies decreased. </p><p>In-band signaling applies only to <a href="/wiki/Channel-associated_signaling" title="Channel-associated signaling">channel-associated signaling</a> (CAS). In <a href="/wiki/Common_channel_signaling" class="mw-redirect" title="Common channel signaling">common channel signaling</a> (CCS) separate channels are used for control and data, as opposed to the shared channel in CAS, so all control is out-of-band by definition. </p><p>In computer data, the term refers to embedding any kind of <a href="/wiki/Metadata" title="Metadata">metadata</a> directly within regular data. These uses have similar tradeoffs as in telecommunications, such as opening an <a href="/wiki/Attack_surface" title="Attack surface">attack surface</a> vs. simplifying processing. A few of many examples: </p> <ul><li>Embedding a <a href="/wiki/Magic_number_(programming)" title="Magic number (programming)">magic number</a> at the very start of files, to signal the format or language of the following data.</li> <li>Embedding a NULL character as in C strings, to signal the end of the string (as opposed to keeping that information outside the string).</li> <li>Embedding <a href="/wiki/Markup_language" title="Markup language">markup</a> within text, whether to categorize parts of the text, provide processing or formatting instructions, or for other purposes.</li> <li>Reserving some characters in <a href="/wiki/Regular_expressions" class="mw-redirect" title="Regular expressions">regular expressions</a>, such as "*", to have special processing meanings, rather than representing literals.</li> <li>Embedding <a href="/wiki/C0_and_C1_control_codes" title="C0 and C1 control codes">control codes</a> in <a href="/wiki/Computer_terminal" title="Computer terminal">computer terminal</a> input as a means of device control, allowing command-line users to issue single-character commands directly, e.g. <style data-mw-deduplicate="TemplateStyles:r1249182868">.mw-parser-output .keyboard-key{border:1px solid #aaa;border-radius:0.2em;box-shadow:0.1em 0.1em 0.2em rgba(0,0,0,0.1);background-color:var(--background-color-neutral-subtle,#f8f9fa);background-image:linear-gradient(to bottom,var(--background-color-neutral,#eaecf0),var(--background-color-neutral-subtle,#f8f9fa),var(--background-color-neutral,#eaecf0));color:var(--color-base,#202122);padding:0.1em 0.3em;font-family:inherit;font-size:0.85em}</style><kbd class="keyboard-key nowrap">Ctrl</kbd>+<kbd class="keyboard-key nowrap">d</kbd> issues a <code><a href="/wiki/End-of-transmission_character" class="mw-redirect" title="End-of-transmission character">^D</a></code> code, causing command-line programs to expect no further input from the user, and therefore to quit.</li></ul> <p>When <a href="/wiki/Out-of-band_data" title="Out-of-band data">out-of-band</a> communication is unavailable, one of two techniques may be used to preserve network <a href="/wiki/Transparency_(telecommunication)" title="Transparency (telecommunication)">transparency</a>. </p> <ul><li><a href="/wiki/Encapsulation_(networking)" title="Encapsulation (networking)">Encapsulation</a>: The bundling of the control data in the <a href="/wiki/Packet_(information_technology)" class="mw-redirect" title="Packet (information technology)">packet</a>'s <a href="/wiki/Header_(computing)" title="Header (computing)">header</a> and then removing the header (and/or footer) of the packet at the far end, restoring the data to be the same as the original.</li> <li><a href="/wiki/Bit_stuffing" title="Bit stuffing">Bit stuffing</a>: The insertion of non-information or <a href="/wiki/Escape_character" title="Escape character">escape characters</a> to modify, synchronize and justify the data so it never looks like signaling information (and remove the stuffed bits and escape codes at the far end, restoring the data to be the same as the original).</li></ul> <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=In-band_signaling&action=edit&section=4" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Control_character" title="Control character">Control character</a></li> <li><a href="/wiki/Escape_sequence" title="Escape sequence">Escape sequence</a></li> <li><a href="/wiki/In-band_control" title="In-band control">In-band control</a></li> <li><a href="/wiki/Line_signaling" title="Line signaling">Line signaling</a></li> <li><a href="/wiki/Out-of-band_control" title="Out-of-band control">Out-of-band control</a></li> <li><a href="/wiki/Quindar_tones" title="Quindar tones">Quindar tones</a></li> <li><a href="/wiki/%2B%2B%2B_(modem)" class="mw-redirect" title="+++ (modem)">+++ (modem)</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=In-band_signaling&action=edit&section=5" 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 class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.pcmag.com/encyclopedia/term/signaling-inout-of-band">"Definition of signaling in/out-of-band"</a>. <i>PCMAG</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2021-10-17</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=PCMAG&rft.atitle=Definition+of+signaling+in%2Fout-of-band&rft_id=https%3A%2F%2Fwww.pcmag.com%2Fencyclopedia%2Fterm%2Fsignaling-inout-of-band&rfr_id=info%3Asid%2Fen.wikipedia.org%3AIn-band+signaling" 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="CITEREFPetersen2002" class="citation book cs1">Petersen, J. K. (2002-05-29). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=YH_LBQAAQBAJ&q=signaling%2520system%2520ss4&pg=PA844"><i>The Telecommunications Illustrated Dictionary, Second Edition</i></a>. CRC Press. p. 844. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9781420040678" title="Special:BookSources/9781420040678"><bdi>9781420040678</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Telecommunications+Illustrated+Dictionary%2C+Second+Edition&rft.pages=844&rft.pub=CRC+Press&rft.date=2002-05-29&rft.isbn=9781420040678&rft.aulast=Petersen&rft.aufirst=J.+K.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DYH_LBQAAQBAJ%26q%3Dsignaling%252520system%252520ss4%26pg%3DPA844&rfr_id=info%3Asid%2Fen.wikipedia.org%3AIn-band+signaling" 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="CITEREFV.S.Bagad2009" class="citation book cs1">V.S.Bagad (2009). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=VfPST6NEggEC&q=ccitt%2520ss1&pg=SA4-PA8"><i>Telecommunication Switching Systems and Networks</i></a>. Technical Publications. p. 388. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9788184315905" title="Special:BookSources/9788184315905"><bdi>9788184315905</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Telecommunication+Switching+Systems+and+Networks&rft.pages=388&rft.pub=Technical+Publications&rft.date=2009&rft.isbn=9788184315905&rft.au=V.S.Bagad&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DVfPST6NEggEC%26q%3Dccitt%252520ss1%26pg%3DSA4-PA8&rfr_id=info%3Asid%2Fen.wikipedia.org%3AIn-band+signaling" class="Z3988"></span><sup class="noprint Inline-Template"><span style="white-space: nowrap;">[<i><a href="/wiki/Wikipedia:Link_rot" title="Wikipedia:Link rot"><span title=" Dead link tagged September 2024">permanent dead link</span></a></i><span style="visibility:hidden; color:transparent; padding-left:2px">‍</span>]</span></sup></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><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.cisco.com/c/en/us/support/docs/voice/digital-cas/5717-e1-r2-sig.html">"E1 R2 Signaling Theory"</a>. <i>Cisco</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2018-01-05</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Cisco&rft.atitle=E1+R2+Signaling+Theory&rft_id=https%3A%2F%2Fwww.cisco.com%2Fc%2Fen%2Fus%2Fsupport%2Fdocs%2Fvoice%2Fdigital-cas%2F5717-e1-r2-sig.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AIn-band+signaling" class="Z3988"></span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text">RFC 4733, <i>RTP Payload for DTMF Digits, Telephony Tones, and Telephony Signals</i>, Schulzrinne, Tayler (2006)</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=In-band_signaling&oldid=1259770877">https://en.wikipedia.org/w/index.php?title=In-band_signaling&oldid=1259770877</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:Network_management" title="Category:Network management">Network management</a></li><li><a href="/wiki/Category:Telephony_signals" title="Category:Telephony signals">Telephony signals</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:All_articles_with_dead_external_links" title="Category:All articles with dead external links">All articles with dead external links</a></li><li><a href="/wiki/Category:Articles_with_dead_external_links_from_September_2024" title="Category:Articles with dead external links from September 2024">Articles with dead external links from September 2024</a></li><li><a href="/wiki/Category:Articles_with_permanently_dead_external_links" title="Category:Articles with permanently dead external links">Articles with permanently dead external links</a></li><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_matches_Wikidata" title="Category:Short description matches Wikidata">Short description matches Wikidata</a></li><li><a href="/wiki/Category:Articles_needing_additional_references_from_May_2017" title="Category:Articles needing additional references from May 2017">Articles needing additional references from May 2017</a></li><li><a href="/wiki/Category:All_articles_needing_additional_references" title="Category:All articles needing additional references">All articles needing additional references</a></li><li><a href="/wiki/Category:Articles_needing_expert_attention_from_April_2017" title="Category:Articles needing expert attention from April 2017">Articles needing expert attention from April 2017</a></li><li><a href="/wiki/Category:All_articles_needing_expert_attention" title="Category:All articles needing expert attention">All articles needing expert attention</a></li><li><a href="/wiki/Category:Telecommunications_articles_needing_expert_attention" title="Category:Telecommunications articles needing expert attention">Telecommunications articles needing expert attention</a></li><li><a href="/wiki/Category:Articles_with_multiple_maintenance_issues" title="Category:Articles with multiple maintenance issues">Articles with multiple maintenance issues</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 26 November 2024, at 23:30<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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