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Circuit Merit
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<h2 id="delivered-audio-quality">Delivered Audio Quality</h2> <p>For use on digital voice telephone systems, the DAQ reference is used. This differs from Circuit Merit in that it adds definitions for digitized voice and a static SINAD for multipath fading, using levels described in TIA/EIA TSB-88-A.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p> <table><tbody><tr><th>Delivered Audio Quality</th><th>Definition</th></tr><tr><td>DAQ 5</td><td>Speech easily understood.</td></tr><tr><td>DAQ 4.5</td><td>Speech easily understood. Infrequent Noise/Distortion.</td></tr><tr><td>DAQ 4</td><td>Speech easily understood. Occasional Noise/Distortion.</td></tr><tr><td>DAQ 3.4</td><td>Speech understandable with repetition only rarely required. Some Noise/Distortion.</td></tr><tr><td>DAQ 3</td><td>Speech understandable with slight effort. Occasional repetition due to Noise/Distortion.</td></tr><tr><td>DAQ 2</td><td>Understandable with considerable effort. Frequent repetition due to Noise/Distortion.</td></tr><tr><td>DAQ 1</td><td>Unusable. Speech present but not understandable.</td></tr></tbody></table> <h2 id="history">History</h2> <p>The Circuit Merit system was developed early in the 20th Century by AT&T to quantifiably measure voice quality on the <a href="/facts/Public_switched_telephone_network/eVrCTDU7">PSTN</a>, and later adapted to include wireless telephone circuits, such as the early <a href="/facts/Mobile_Telephone_Service/l7bTdEDP">MTS</a> (which was first used in 1947), <a href="/facts/Improved_Mobile_Telephone_Service/KgpDAFUw">IMTS</a> and the later cellular telephone system (field trials date from 1976). It is intended to be used on a statistical basis, by collecting multiple data points (either subjective scores by human listeners, or by electronic measurements), to then produce a comprehensive report on the circuit quality. The system does not include any provision for reporting <a href="/facts/RF/aWku7h4R">RF</a> signal strength, and is thus inappropriate for routine use on non-telephone voice radio systems. </p><p>Circuit merit is specifically designed to report the signal-to-noise ratio<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> of a communications circuit, preferably by use of electronic test equipment. See also <a href="/facts/Figure_of_merit/kdSJ3Cpy">Figure of Merit</a> </p><p>The Circuit Merit system is also used mistakenly <a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a><a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> by some amateur radio operators<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> unfamiliar with its origins<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> to overcome perceived inadequacies in using the <a href="/facts/RST_code/jwTAG1va">R-S-T System</a>. This belief is contrary to the published description of the R-S-T System (which uses the same number of levels for readability), and of modern (as of 2006) requirement "...that plain language be used for multi-agency, multi-jurisdiction and multi-discipline events, such as major disasters and exercises..." instead of numeric codes in radio traffic in <a href="/facts/National_Incident_Management_System/mePBd9l6">NIMS</a>/<a href="/facts/Incident_command_system/UBzgNhTL">ICS</a>.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> As both Circuit Merit and the R-S-T System use numbers that are often difficult for operators to map to meanings, neither complies with the intent of the NIMS plain language directive. </p><p>There is at least one plain-language voice and signal strength reporting system that does meet the NIMS plain language directive—the <a href="/facts/Plain_language_radio_checks/D7jBGwlN">Plain Language Radio Checks</a> as described in section 611 of Allied Communications Procedure 125(F): Radio Checks, Signal Strength, and Readability. The best-possible radio check report possible under this system, "LOUD AND CLEAR", is commonly used in film, television, and literature depictions of radio communications. </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Absolute_Category_Rating/9ApkCaFs">Absolute Category Rating</a></li> <li><a href="/facts/Mean_opinion_score/EpY5TsQM">MOS</a> Mean Opinion Score</li> <li><a href="/facts/Perceptual_Evaluation_of_Speech_Quality/sJcUPedc">Perceptual Evaluation of Speech Quality</a> (PESQ)</li> <li><a href="/facts/Perceptual_Objective_Listening_Quality_Analysis/MMDB7FaN">Perceptual Objective Listening Quality Analysis</a> (POLQA)</li> <li><a href="/facts/Plain_language_radio_checks/D7jBGwlN">Plain Language Radio Checks</a></li> <li><a href="/facts/QSA_and_QRK_code/vRT6aH88">QSA and QRK code</a> (for Morse code only)</li> <li><a href="/facts/R-S-T_system/jwTAG1va">R-S-T system</a> (for Amateur radio only)</li> <li><a href="/facts/Signal_strength_and_readability_report/kPJSljTC">Signal strength and readability report</a></li> <li><a href="/facts/SINPO_code/pXMjYGq0">SINPO code</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"Mobile Radio Estimates of Expected Coverage". <a href="http://www.telephonecollectors.info/index.php/document-repository/doc_view/9894-940-230-100-i1" target="_blank">http://www.telephonecollectors.info/index.php/document-repository/doc_view/9894-940-230-100-i1</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Bucher, John (1991). "An Overview of Cellular Telecommunications thesis" (PDF). Archived (PDF) from the original on February 18, 2017. <a href="http://apps.dtic.mil/dtic/tr/fulltext/u2/a242951.pdf" target="_blank">http://apps.dtic.mil/dtic/tr/fulltext/u2/a242951.pdf</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Arokiamary, V.Jeyasri (2009). Cellular and Mobile Communications (First ed.). 1.4 Performance Criteria: Technical Publications Pune. p. 14. ISBN 978-81-8431-585-1. Retrieved 27 March 2015.{{cite book}}: CS1 maint: location (link) <a href="978-81-8431-585-1" target="_blank">978-81-8431-585-1</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Bucher, John (1991). "An Overview of Cellular Telecommunications thesis" (PDF). Archived (PDF) from the original on February 18, 2017. <a href="http://apps.dtic.mil/dtic/tr/fulltext/u2/a242951.pdf" target="_blank">http://apps.dtic.mil/dtic/tr/fulltext/u2/a242951.pdf</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Ballou, Glen (2015). Handbook for Sound Engineers. New York and London: Focal Press (Audio Engineering Society). p. 45. <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Federal Engineering, Inc. document. <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>"Calculating signal to noise ratio" (PDF). <a href="http://www.bhsu.edu/Portals/91/InstrumentalAnalysis/StudyHelp/LectureNotes/Chapter5.pdf" target="_blank">http://www.bhsu.edu/Portals/91/InstrumentalAnalysis/StudyHelp/LectureNotes/Chapter5.pdf</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>"Circuit merit silliness". <a href="http://wetnet.net/pipermail/seatcp/2011-October/011575.html" target="_blank">http://wetnet.net/pipermail/seatcp/2011-October/011575.html</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>"Wetnet.net discussion thread on Circuit Merit". <a href="http://wetnet.net/pipermail/seatcp/2014-May/014562.html" target="_blank">http://wetnet.net/pipermail/seatcp/2014-May/014562.html</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>"Signal Reporting Using the Circuit Merit System" (PDF). Information Papers. Virginia RACES, Inc. May 2004. Retrieved 2015-02-08. <a href="http://www.vistacert.org/resources/signal_quality_circuit_merit_system1.pdf" target="_blank">http://www.vistacert.org/resources/signal_quality_circuit_merit_system1.pdf</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>"Plain Language Signal Reporting". <a href="http://www.eham.net/ehamforum/smf/index.php/topic,44690.0.html" target="_blank">http://www.eham.net/ehamforum/smf/index.php/topic,44690.0.html</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>"Plain Language Frequently Asked Questions (FAQs)" (PDF). <a href="https://www.dhs.gov/sites/default/files/publications/PlainLanguageFAQs.pdf" target="_blank">https://www.dhs.gov/sites/default/files/publications/PlainLanguageFAQs.pdf</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> </ol>