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Crosstalk
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<h2 id="in-cabling">In cabling</h2> <p class="note">See also: <a href="/facts/Copper_cable_certification/whwntkoB">Copper cable certification § Tests</a></p> <p>In structured cabling, crosstalk refers to <a href="/facts/Electromagnetic_interference/gv3DlKNr">electromagnetic interference</a> from one unshielded <a href="/facts/Twisted_pair/L426Jk2C">twisted pair</a> to another twisted pair, normally running in parallel. Signals traveling through adjacent pairs of wire create magnetic fields that interact with each other, inducing interference in the neighboring pair. The pair causing the interference is called the <i>disturbing pair</i>, while the pair experiencing the interference is the <i>disturbed pair</i>. </p> Near-end crosstalk (NEXT) NEXT is a measure of the ability of a cable to reject crosstalk, so the higher the NEXT value, the greater the rejection of crosstalk at the local connection. It is referred to as <i>near end</i> because the interference between the two signals in the cable is measured at the same end of the cable as the interfering transmitter. The NEXT value for a given cable type is generally expressed in decibels per feet or decibels per 1000 feet and varies with the frequency of transmission. General specifications for cabling (such as CAT 5) usually include the minimum NEXT values.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> Power sum near-end crosstalk (PSNEXT) PSNEXT is a NEXT measurement which includes the sum of crosstalk contributions from all adjacent pairs as an algebraic sum of the NEXT of the three wire pairs as they affect the fourth pair in a four-pair cable (e.g., Category 6 cable).<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> The Superior Modular Products White paper<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> states that the testing process for PSNEXT consists of measuring all pair-to-pair crosstalk combinations and then summing all of the values for each pair. The specification was developed to directly address the effect of transmissions on multiple adjacent pairs on the pair being tested and is relevant to all connecting hardware and associated communications cables. Cabling bandwidth in excess of 100 MHz (<a href="/facts/Category_5_cable/hw2XHSh3">Category 5 cable</a> bandwidth) make consideration of PSNEXT more important as <a href="/facts/Gigabit_Ethernet/1ItIoV2w">Gigabit Ethernet</a> through <a href="/facts/Cat_6/qv2G0J8p">Cat 6</a> uses all four wire pairs simultaneously and bidirectionally. The additional wire pair usage and growing bandwidth increases the need to keep NEXT in check. Far-end crosstalk (FEXT) FEXT measures the interference between two pairs of a cable measured at the far end of the cable with respect to the interfering transmitter.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> Equal level far end crosstalk (ELFEXT) ELFEXT measures the FEXT with attenuation compensation.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> Alien crosstalk (AXT) AXT is interference caused by other cables routed close to the cable of interest as opposed to signals contained in the same cable.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> <h2 id="in-audio">In audio</h2> <p>In <a href="/facts/Stereo/z0vmJcGT">stereo</a> audio reproduction, crosstalk can refer to signal leakage across from one program channel to another, reducing channel separation and <a href="/facts/Stereo_imaging/gVB7Yn2h">stereo imaging</a>. Crosstalk between channels in mixing consoles, and between studio feeds is a much more noticeable problem, as these are likely to be carrying very different programs or material. </p><p>Crosstalk is an electrical effect and can be quantified with a crosstalk measurement. Crosstalk measurements are made on audio systems to determine the amount of signal leaking from one channel to another. The <a href="/facts/Independent_Broadcasting_Authority/r19NWSlY">Independent Broadcasting Authority</a> published a <a href="/facts/Weighting_curve/dFuW8xSV">weighting curve</a> for use in crosstalk measurement that gives due emphasis to the subjective audibility of different frequencies. In the absence of any international standards, this is still in use despite the demise of the IBA. </p><p>Good crosstalk performance for a stereo system is not difficult to achieve in today's <a href="/facts/Digital_audio/PgugcLAI">digital audio</a> systems, though it is difficult to keep below the desired figure of −30 dB or so on <a href="/facts/Vinyl_record/ccuFV9Af">vinyl recordings</a> and <a href="/facts/FM_radio/TpKl3FJv">FM radio</a>. </p> <h2 id="other-examples">Other examples</h2> <p>In <a href="/facts/Telecommunication/vxoj1cxR">telecommunication</a> or <a href="/facts/Telephony/2GwTTepw">telephony</a>, crosstalk is often distinguishable as pieces of speech or <a href="/facts/In-band_signaling/KAgeV09X">in-band signaling</a> tones leaking from other people's connections.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> If the connection is analog, <a href="/facts/Twisted_pair/L426Jk2C">twisted pair</a> cabling can often be used to reduce crosstalk. Alternatively, the signals can be converted to digital form, which is typically less susceptible to crosstalk. </p><p>In <a href="/facts/Wireless_communication/GfDoFwfo">wireless communication</a>, crosstalk is often denoted <a href="/facts/Co-channel_interference/I95JpU6Y">co-channel interference</a>, and is related to <a href="/facts/Adjacent-channel_interference/2SnGEybp">adjacent-channel interference</a>. </p><p>In <a href="/facts/Integrated_circuit_design/sE0qVzyo">integrated circuit design</a>, crosstalk normally refers to a signal affecting another nearby signal. Usually, the coupling is capacitive, and to the nearest neighbor, but other forms of coupling and effects on signal further away are sometimes important, especially in analog designs. See <a href="/facts/Signal_integrity/cqL8SVHd">signal integrity</a> for tools used to measure and prevent this problem, and <a href="/facts/Substrate_coupling/bUlAXCDE">substrate coupling</a> for a discussion of crosstalk conveyed through the <a href="/facts/Integrated_circuit/fjn6vg7C">integrated circuit</a> substrate. There are a wide variety of repair solutions, with increased spacing, wire re-ordering, and shielding being the most common. </p><p>In full-field optical coherence <a href="/facts/Tomography/HGqzMl2s">tomography</a>, "crosstalk" refers to the phenomenon that due to highly scattering objects, multiple scattered photons reach the image plane and generate a coherent signal after travelling a path length that matches that of the sample depth within a coherence length. </p><p>In <a href="/facts/3D_display/ahEDcbh3">stereoscopic 3D displays</a>, crosstalk refers to the incomplete isolation of the left and right image channels so that one bleeds into the other – like a <a href="/facts/Double_exposure/3F2RG2L0">double exposure</a>, which produces a <a href="/facts/Ghosting_(television)/oybe05LJ">ghosting</a> effect. </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Attenuation-to-crosstalk_ratio/owvdlhJA">Attenuation-to-crosstalk ratio</a></li> <li><a href="/facts/Audio_system_measurements/9hnslzGd">Audio system measurements</a></li> <li><a href="/facts/Print-through/E88a6JbU">Print-through</a></li> <li><a href="/facts/Signal_integrity/cqL8SVHd">Signal integrity</a></li> <li><a href="/facts/Signal-to-interference_ratio/lBQVMXmC">Signal-to-interference ratio</a> (SIR or <i>S</i>/<i>I</i>), also known as <a href="/facts/Carrier-to-interference_ratio/lBQVMXmC">carrier-to-interference ratio</a> (CIR or <i>C</i>/<i>I</i>)</li> <li><a href="/facts/Substrate_coupling/bUlAXCDE">Substrate coupling</a></li> <li><a href="/facts/Unger_model/aUlguSmL">Unger model</a></li></ul> <p> This article incorporates <a href="/facts/Copyright_status_of_works_by_the_federal_government_of_the_United_States/Q1jvr96g">public domain material</a> from <a href="https://web.archive.org/web/20220122224547/https://www.its.bldrdoc.gov/fs-1037/fs-1037c.htm"><i>Federal Standard 1037C</i></a>. <a href="/facts/General_Services_Administration/Np3opv9x">General Services Administration</a>. Archived from <a href="https://www.its.bldrdoc.gov/fs-1037/fs-1037c.htm">the original</a> on 2022-01-22. (in support of <a href="/facts/MIL-STD-188/D5rsvdsW">MIL-STD-188</a>). </p> <h2 id="external-links">External links</h2> Look up <i>crosstalk</i> in Wiktionary, the free dictionary. <ul><li><a href="https://web.archive.org/web/20120318040330/https://download.intel.com/education/highered/signal/ELCT762/class19_Crosstalk_overview.ppt">Crosstalk: Overview and Modes (ppt)</a> at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a> (archived 2012-03-18)</li> <li><a href="https://web.archive.org/web/20111002150401/http://www.ieee.li/pdf/viewgraphs/minimizing_crosstalk_wiring_cabling.pdf">Minimizing Crosstalk in Wiring and Cabling</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>LearnEMC Web Site: Common-Impedance Coupling <a href="http://learnemc.com/common-impedance-coupling" target="_blank">http://learnemc.com/common-impedance-coupling</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>K.-H. Gonschorek and R. Vick: Electromagnetic Compatibility for Device Design and System Integration, Springer, Berlin Heidelberg, 2009, ISBN 978-3-642-03289-9, page 90 <a href="/wiki/ISBN_(identifier)" target="_blank">/wiki/ISBN_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>"Category 5 / 5E & Cat 6 Cabling Tutorial and FAQ's". lanshack.com. Archived from the original on 2013-01-17. Retrieved 2013-01-05. <a href="http://www.lanshack.com/cat5e-tutorial.aspx" target="_blank">http://www.lanshack.com/cat5e-tutorial.aspx</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>"Category 5 / 5E & Cat 6 Cabling Tutorial and FAQ's". lanshack.com. Archived from the original on 2013-01-17. Retrieved 2013-01-05. <a href="http://www.lanshack.com/cat5e-tutorial.aspx" target="_blank">http://www.lanshack.com/cat5e-tutorial.aspx</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>"Component Level PowerSum Compliance and RJ21X Connectivity Solutions (Superior Modular Products White paper)" (PDF). Archived from the original (PDF) on July 16, 2006. Retrieved 2008-09-13. <a href="https://web.archive.org/web/20060716043452/http://www.superiormod.com/smp/pages/support/White%20Paper%20-%20RJ21X.pdf" target="_blank">https://web.archive.org/web/20060716043452/http://www.superiormod.com/smp/pages/support/White%20Paper%20-%20RJ21X.pdf</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>"Category 5 / 5E & Cat 6 Cabling Tutorial and FAQ's". lanshack.com. Archived from the original on 2013-01-17. Retrieved 2013-01-05. <a href="http://www.lanshack.com/cat5e-tutorial.aspx" target="_blank">http://www.lanshack.com/cat5e-tutorial.aspx</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>"Category 5 / 5E & Cat 6 Cabling Tutorial and FAQ's". lanshack.com. Archived from the original on 2013-01-17. Retrieved 2013-01-05. <a href="http://www.lanshack.com/cat5e-tutorial.aspx" target="_blank">http://www.lanshack.com/cat5e-tutorial.aspx</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Eliminating alien crosstalk, Communications News, February 2009, archived from the original on 2010-02-09 <a href="https://web.archive.org/web/20100209073156/http://www.comnews.com/features/2009_february/0209_web3_eliminating.aspx" target="_blank">https://web.archive.org/web/20100209073156/http://www.comnews.com/features/2009_february/0209_web3_eliminating.aspx</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>"crosstalk (XT)". Federal Standard 1037C glossary. Retrieved 2018-03-26. <a href="https://www.its.bldrdoc.gov/fs-1037/dir-009/_1340.htm" target="_blank">https://www.its.bldrdoc.gov/fs-1037/dir-009/_1340.htm</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> </ol>