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<title>Light characteristic</title>

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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Light characteristic</span></span>

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<p>A <b>light characteristic</b> is all of the properties that make a particular navigational light identifiable. Graphical and textual descriptions of navigational light sequences and colours are displayed on <a href="Nautical_chart" title="Nautical chart">nautical charts</a> and in <a href="Light_List" class="mw-redirect" title="Light List">Light Lists</a> with the chart symbol for a <a href="Lighthouse" title="Lighthouse">lighthouse</a>, <a href="Lightvessel" class="mw-redirect" title="Lightvessel">lightvessel</a>, <a href="Buoy" title="Buoy">buoy</a> or <a href="Sea_mark" title="Sea mark">sea mark</a> with a <a href="Light" title="Light">light</a> on it. Different lights use different colours, frequencies and light patterns, so mariners can identify which light they are seeing.<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>

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<div class="mw-heading mw-heading2"><h2 id="Standardisation">Standardisation</h2></div>

<p>The <a href="International_Association_of_Marine_Aids_to_Navigation_and_Lighthouse_Authorities" title="International Association of Marine Aids to Navigation and Lighthouse Authorities">International Association of Marine Aids to Navigation and Lighthouse Authorities</a> (IALA) publishes a recommendation R1001 <i>"The IALA Maritime Buoyage System (MBS)"</i><sup id="cite_ref-:0_2-0" class="reference"><a href="#cite_note-:0-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> which is stated within to be adopted by almost all marine <a href="Navigational_aid" title="Navigational aid">aids to navigation</a> authorities. This recommendation sets out recommended light characteristics for different types of marine aids to navigation within the categories of <a href="Lateral_mark" title="Lateral mark">lateral marks</a>, <a href="Cardinal_mark" title="Cardinal mark">cardinal marks</a>, <a href="Isolated_danger_mark" title="Isolated danger mark">isolated danger marks</a>, <a href="Safe_water_mark" title="Safe water mark">safe water marks</a>, <a href="Special_mark" title="Special mark">special marks</a>, emergency wreck marks and other marks such as lighthouses. Depending on the marine aid to navigation, this recommendation includes specification of light colours (such as "red") and light patterns (such as "Fl" for flashing).

</p><p>Light colours are defined in recommendation R0201 <i>"Marine Signal Lights-Colours (E200-1)"</i>.<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> This recommendation specifies for each named colour a polygon within the <a href="CIE_1931_color_space" title="CIE 1931 color space">CIE 1931 color space</a> for acceptable shades of the named colour a marine aid to navigation may exhibit.

</p><p>Light patterns, including abbreviations, are defined in recommendation R0110 <i>"Rhythmic Characters of Lights on Aids to Navigation"</i>.<sup id="cite_ref-:1_4-0" class="reference"><a href="#cite_note-:1-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading2"><h2 id="Abbreviations">Abbreviations</h2></div>

<p>While light characteristics can be described in prose, e.g. "Flashing white every two seconds", lists of lights and navigation chart annotations use abbreviations. The abbreviation notation is slightly different from one light list to another, with dots added or removed, but it usually follows a pattern similar to the following (see the chart to the right for examples).

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<ul><li>An abbreviation of the type of light, e.g. <b>"Fl."</b> for Flashing, <b>"F."</b> for Fixed.</li>

<li>The color of the light, e.g. <b>"W"</b> for White, <b>"G"</b> for Green, <b>"R"</b> for Red, <b>"Y"</b> for Yellow, <b>"Bu"</b> for Blue. If no color is given, a White light is generally implied.</li>

<li>The cycle period, e.g. <b>"10s"</b> for ten seconds.</li>

<li>Additional parameters are sometimes added:</li></ul>

<dl><dd><ul><li>The height of the light above the chart datum for height (usually based on <a href="Tide" title="Tide">high water</a>). e.g. <b>"15m"</b> for 15 metres.</li>

<li>The range in which the light is visible, e.g. <b>"10M"</b> for 10 <a href="Nautical_mile" title="Nautical mile">nautical miles</a>. (ca. 18.5 kilometers)</li>

<li>A light that only shines in one direction <b>"Dir."</b>. This is also indicated by a sector in which the light can be seen. In the figure of the lighthouse at "Egmond aan Zee" (Netherlands) two sectors are indicated; a white sector from 10° to 175° and a red sector from 175° to 188°</li></ul></dd></dl>

<p>An example of a complete light characteristic is <b>"Gp Oc(3) W 10s 15m 10M".</b> This indicates that the light is a <i>group occulting light</i> in which a group of three eclipses repeat every 10 seconds; the light is white; the light is 15 metres above the chart datum and the nominal range is 10 <a href="Nautical_mile" title="Nautical mile">nautical miles</a>.

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<div class="mw-heading mw-heading2"><h2 id="Light_patterns">Light patterns</h2></div>

<div class="mw-heading mw-heading3"><h3 id="Fixed_light">Fixed light</h3></div>

<p>Fixed lights, abbreviated "F",<sup id="cite_ref-:1_4-1" class="reference"><a href="#cite_note-:1-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> are a continuous and steady light. The IALA Marine Buoyage System does not include use of a fixed light pattern due to lack of differentiation as a marine aid to navigation light.<sup id="cite_ref-:0_2-1" class="reference"><a href="#cite_note-:0-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading3"><h3 id="Flashing_light">Flashing light</h3></div>

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</style><div role="note" class="hatnote navigation-not-searchable">"Flashing light" redirects here. For other uses, see <a href="Flashing_Lights_(disambiguation)" class="mw-redirect mw-disambig" title="Flashing Lights (disambiguation)">Flashing Lights (disambiguation)</a>.</div>

<div class="mw-heading mw-heading4"><h4 id="Single_flashing_light">Single flashing light</h4></div>

<p>Single flashing lights continuously repeat a flash of light of duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle l}">

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</mrow>

<annotation encoding="application/x-tex">{\displaystyle l}</annotation>

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</math></span><img src="./829091f745070b9eb97a80244129025440a1cfac.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.693ex; height:2.176ex;" alt="{\displaystyle l}" loading="lazy"></span> followed by an obviously longer duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle d}">

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<annotation encoding="application/x-tex">{\displaystyle d}</annotation>

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</math></span><img src="./e85ff03cbe0c7341af6b982e47e9f90d235c66ab.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.216ex; height:2.176ex;" alt="{\displaystyle d}" loading="lazy"></span> of darkness. Every repetition is identical. Single flashing lights are abbreviated as "Fl".<sup id="cite_ref-:1_4-2" class="reference"><a href="#cite_note-:1-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

</p><p>The IALA Marine Buoyage System allows (but does not mandate) single flashing lights to be used for the following purposes:<sup id="cite_ref-:0_2-2" class="reference"><a href="#cite_note-:0-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>

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<ul><li>Port hand lateral marks, if the single flashing light has a colour of red and the mark is in region "A".</li>

<li>Starboard hand lateral marks, if the single flashing light has a colour of green and the mark is in region "A".</li>

<li>Port hand lateral marks, if the single flashing light has a colour of green and the mark is in region "B".</li>

<li>Starboard hand lateral marks, if the single flashing light has a colour of red and the mark is in region "B".</li>

<li>Special marks, if the single flashing light has a colour of yellow.</li></ul>

<p>IALA recommendation R0110 specifies that a single flashing light should:<sup id="cite_ref-:1_4-3" class="reference"><a href="#cite_note-:1-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

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<ul><li>Have a period of repetition within the range of <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle 2\leq p\leq 15}">

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<annotation encoding="application/x-tex">{\displaystyle 2\leq p\leq 15}</annotation>

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</math></span><img src="./45a874f8f971002237efda07af4df535b5cb204b.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:10.854ex; height:2.509ex;" alt="{\displaystyle 2\leq p\leq 15}" loading="lazy"></span> seconds for countries which do not use "quick lights". This corresponds to frequency of 4 to 30 flashes per minute.</li>

<li>Have a period of repetition within the range of <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle 2.5\leq p\leq 15}">

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</mrow>

<annotation encoding="application/x-tex">{\displaystyle 2.5\leq p\leq 15}</annotation>

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</math></span><img src="./db3fc171fa25c96e7c031f8ce2456b8b684a9715.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:12.663ex; height:2.509ex;" alt="{\displaystyle 2.5\leq p\leq 15}" loading="lazy"></span> seconds for countries which do use "quick lights". This corresponds to frequency of 4 to 24 flashes per minute.</li>

<li>Have a duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle l}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle l}</annotation>

</semantics>

</math></span><img src="./829091f745070b9eb97a80244129025440a1cfac.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.693ex; height:2.176ex;" alt="{\displaystyle l}" loading="lazy"></span> of light less than 2 seconds within each period <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle p}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle p}</annotation>

</semantics>

</math></span><img src="./81eac1e205430d1f40810df36a0edffdc367af36.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; margin-left: -0.089ex; width:1.259ex; height:2.009ex;" alt="{\displaystyle p}" loading="lazy"></span>.</li>

<li>Have a duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle d}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle d}</annotation>

</semantics>

</math></span><img src="./e85ff03cbe0c7341af6b982e47e9f90d235c66ab.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.216ex; height:2.176ex;" alt="{\displaystyle d}" loading="lazy"></span> of darkness between two successive flashes being three times or more the duration of a flash <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle l}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle l}</annotation>

</semantics>

</math></span><img src="./829091f745070b9eb97a80244129025440a1cfac.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.693ex; height:2.176ex;" alt="{\displaystyle l}" loading="lazy"></span>. For example, if the frequency is 20 flashes per minute (period <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle p}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle p}</annotation>

</semantics>

</math></span><img src="./81eac1e205430d1f40810df36a0edffdc367af36.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; margin-left: -0.089ex; width:1.259ex; height:2.009ex;" alt="{\displaystyle p}" loading="lazy"></span> of 3 seconds), the duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle l}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle l}</annotation>

</semantics>

</math></span><img src="./829091f745070b9eb97a80244129025440a1cfac.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.693ex; height:2.176ex;" alt="{\displaystyle l}" loading="lazy"></span> of a flash may be 0.75 seconds and duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle d}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle d}</annotation>

</semantics>

</math></span><img src="./e85ff03cbe0c7341af6b982e47e9f90d235c66ab.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.216ex; height:2.176ex;" alt="{\displaystyle d}" loading="lazy"></span> of darkness following may be 2.25 seconds to satisfy constraint <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle d\geq 3l}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle d\geq 3l}</annotation>

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</math></span><img src="./b94d0401e65c8152911a0998ecc4a90381dac9ee.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:6.17ex; height:2.343ex;" alt="{\displaystyle d\geq 3l}" loading="lazy"></span>.</li></ul>

<p>If the duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle l}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle l}</annotation>

</semantics>

</math></span><img src="./829091f745070b9eb97a80244129025440a1cfac.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.693ex; height:2.176ex;" alt="{\displaystyle l}" loading="lazy"></span> of light is greater than or equal to 2 seconds, the flashing light may alternatively be classified as a "long flashing light".

</p><p>If the frequency is greater than or equal to 50 flashes per minute (a period <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle p}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle p}</annotation>

</semantics>

</math></span><img src="./81eac1e205430d1f40810df36a0edffdc367af36.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; margin-left: -0.089ex; width:1.259ex; height:2.009ex;" alt="{\displaystyle p}" loading="lazy"></span> less than or equal to 1.2 seconds), the flashing light may alternatively be classified as a "quick light".

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<div class="mw-heading mw-heading4"><h4 id="Long_flashing_light">Long flashing light</h4></div>

<p>Long flashing lights are a variant of single flashing lights where the duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle l}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle l}</annotation>

</semantics>

</math></span><img src="./829091f745070b9eb97a80244129025440a1cfac.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.693ex; height:2.176ex;" alt="{\displaystyle l}" loading="lazy"></span> of light is within the inclusive range of 2 to 5 seconds. Long flashing lights are abbreviated as "LFl",<sup id="cite_ref-:1_4-4" class="reference"><a href="#cite_note-:1-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> and in certain publications abbreviated alternatively as "L.Fl".

</p><p>The IALA Marine Buoyage System allows (but does not mandate) long flashing lights to be used wherever a single flashing light is allowed to be used. The long flashing light must be used for the same purpose and have the same light colour as an equivalent single flashing light.<sup id="cite_ref-:0_2-3" class="reference"><a href="#cite_note-:0-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>

</p><p>A white coloured long flashing light with a period <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle p}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle p}</annotation>

</semantics>

</math></span><img src="./81eac1e205430d1f40810df36a0edffdc367af36.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; margin-left: -0.089ex; width:1.259ex; height:2.009ex;" alt="{\displaystyle p}" loading="lazy"></span> of 10 seconds is additionally specified as an option for safe water marks.<sup id="cite_ref-:0_2-4" class="reference"><a href="#cite_note-:0-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>

</p><p>To satisfy the <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle d\geq 3l}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle d\geq 3l}</annotation>

</semantics>

</math></span><img src="./b94d0401e65c8152911a0998ecc4a90381dac9ee.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:6.17ex; height:2.343ex;" alt="{\displaystyle d\geq 3l}" loading="lazy"></span> constraint specified by IALA recommendation R0110, a long flashing light has a minimum period <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle p}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle p}</annotation>

</semantics>

</math></span><img src="./81eac1e205430d1f40810df36a0edffdc367af36.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; margin-left: -0.089ex; width:1.259ex; height:2.009ex;" alt="{\displaystyle p}" loading="lazy"></span> of 8 seconds. The recommendation also specifies a maximum period <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle p}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle p}</annotation>

</semantics>

</math></span><img src="./81eac1e205430d1f40810df36a0edffdc367af36.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; margin-left: -0.089ex; width:1.259ex; height:2.009ex;" alt="{\displaystyle p}" loading="lazy"></span> of 20 seconds for long flashing lights, restricting duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle l}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle l}</annotation>

</semantics>

</math></span><img src="./829091f745070b9eb97a80244129025440a1cfac.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.693ex; height:2.176ex;" alt="{\displaystyle l}" loading="lazy"></span> to be no greater than 5 seconds. A long flashing light is therefore specified by the recommendation to have a frequency within the inclusive range of 3 to 7.5 flashes per minute.<sup id="cite_ref-:1_4-5" class="reference"><a href="#cite_note-:1-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading4"><h4 id="Group_flashing_light">Group flashing light</h4></div>

<p>Group flashing lights continuously repeat a pattern consisting of a group of flashes followed by a duration of darkness between successive groups. The duration of darkness between successive groups must be obviously longer than the duration of darkness between flashes within a group. Every repetition is identical. Group flashing lights are abbreviated as "Fl(2)" for a group of two flashes,<sup id="cite_ref-:1_4-6" class="reference"><a href="#cite_note-:1-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> and in certain publications abbreviated additionally as "Gr Fl(2)".

</p><p>The IALA Marine Buoyage System specifies group flashing lights be used for isolated danger marks where each group consists of two flashes of white light.<sup id="cite_ref-:0_2-5" class="reference"><a href="#cite_note-:0-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>

</p><p>The IALA Marine Buoyage System allows (but does not mandate) group flashing lights to additionally be used wherever a single flashing light is allowed to be used. The group flashing light must be used for the same purpose and have the same light colour as an equivalent single flashing light.<sup id="cite_ref-:0_2-6" class="reference"><a href="#cite_note-:0-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>

</p><p>IALA recommendation R0110 specifies that a group flashing light should:<sup id="cite_ref-:1_4-7" class="reference"><a href="#cite_note-:1-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

</p>

<ul><li>Have a period of repetition <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle p}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle p}</annotation>

</semantics>

</math></span><img src="./81eac1e205430d1f40810df36a0edffdc367af36.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; margin-left: -0.089ex; width:1.259ex; height:2.009ex;" alt="{\displaystyle p}" loading="lazy"></span> of no more than 20 seconds if each group consists of two flashes.</li>

<li>Have a period of repetition <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle p}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle p}</annotation>

</semantics>

</math></span><img src="./81eac1e205430d1f40810df36a0edffdc367af36.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; margin-left: -0.089ex; width:1.259ex; height:2.009ex;" alt="{\displaystyle p}" loading="lazy"></span> of no more than 30 seconds if each group consists of three or more flashes.</li>

<li>Have between 2 to 5 flashes in a group. By exception, the recommendation also allows groups to have 6 flashes.</li>

<li>Have the same number of flashes in every group.</li>

<li>Have the same duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle l}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle l}</annotation>

</semantics>

</math></span><img src="./829091f745070b9eb97a80244129025440a1cfac.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.693ex; height:2.176ex;" alt="{\displaystyle l}" loading="lazy"></span> of each flash of light.</li>

<li>Have the same duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle d}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle d}</annotation>

</semantics>

</math></span><img src="./e85ff03cbe0c7341af6b982e47e9f90d235c66ab.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.216ex; height:2.176ex;" alt="{\displaystyle d}" loading="lazy"></span> of darkness between every flash in a group.</li>

<li>Have the same duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle d'}">

<msup>

</msup>

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle d'}</annotation>

</semantics>

</math></span><img src="./1f310a68106a9e308bdaf887ff8f7171c4cb9d96.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.903ex; height:2.509ex;" alt="{\displaystyle d'}" loading="lazy"></span> of darkness between every group of flashes.</li>

<li>Have a duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle d'}">

<msup>

</msup>

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle d'}</annotation>

</semantics>

</math></span><img src="./1f310a68106a9e308bdaf887ff8f7171c4cb9d96.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.903ex; height:2.509ex;" alt="{\displaystyle d'}" loading="lazy"></span> of darkness between groups which is at least three times the duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle d}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle d}</annotation>

</semantics>

</math></span><img src="./e85ff03cbe0c7341af6b982e47e9f90d235c66ab.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.216ex; height:2.176ex;" alt="{\displaystyle d}" loading="lazy"></span> of darkness between every flash in a group. For example, if duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle d}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle d}</annotation>

</semantics>

</math></span><img src="./e85ff03cbe0c7341af6b982e47e9f90d235c66ab.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.216ex; height:2.176ex;" alt="{\displaystyle d}" loading="lazy"></span> is 1 second of darkness between each flash in a group, duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle d'}">

<msup>

</msup>

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle d'}</annotation>

</semantics>

</math></span><img src="./1f310a68106a9e308bdaf887ff8f7171c4cb9d96.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.903ex; height:2.509ex;" alt="{\displaystyle d'}" loading="lazy"></span> must be 3 seconds or more of darkness between groups of flashes.</li>

<li>Have a duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle c}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle c}</annotation>

</semantics>

</math></span><img src="./86a67b81c2de995bd608d5b2df50cd8cd7d92455.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.007ex; height:1.676ex;" alt="{\displaystyle c}" loading="lazy"></span> of at least 1 second where <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle c=l+d}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle c=l+d}</annotation>

</semantics>

</math></span><img src="./0269ee701d69c70150a897752cab575354a2de91.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:8.855ex; height:2.343ex;" alt="{\displaystyle c=l+d}" loading="lazy"></span>, if each group consists of two flashes.</li>

<li>Have a duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle c}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle c}</annotation>

</semantics>

</math></span><img src="./86a67b81c2de995bd608d5b2df50cd8cd7d92455.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.007ex; height:1.676ex;" alt="{\displaystyle c}" loading="lazy"></span> of at least 2 seconds where <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle c=l+d}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle c=l+d}</annotation>

</semantics>

</math></span><img src="./0269ee701d69c70150a897752cab575354a2de91.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:8.855ex; height:2.343ex;" alt="{\displaystyle c=l+d}" loading="lazy"></span>, if each group consists of three or more flashes and the country deploying the group flashing light does not use "quick lights".</li>

<li>Have a duration <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle c}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle c}</annotation>

</semantics>

</math></span><img src="./86a67b81c2de995bd608d5b2df50cd8cd7d92455.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.007ex; height:1.676ex;" alt="{\displaystyle c}" loading="lazy"></span> of at least 2.5 seconds where <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle c=l+d}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle c=l+d}</annotation>

</semantics>

</math></span><img src="./0269ee701d69c70150a897752cab575354a2de91.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:8.855ex; height:2.343ex;" alt="{\displaystyle c=l+d}" loading="lazy"></span>, if each group consists of three or more flashes and the country deploying the group flashing light uses "quick lights".</li></ul>

<div class="mw-heading mw-heading4"><h4 id="Composite_group_flashing_light">Composite group flashing light</h4></div>

<p>Composite group flashing lights are a variant of group flashing lights with two groups of flashes in each period. Group flashing lights are abbreviated as "Fl(2+1)" for a group of two flashes followed by a single flash (group of one flash). There are three durations of darkness for composite group flashing lights:<sup id="cite_ref-:1_4-8" class="reference"><a href="#cite_note-:1-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

</p>

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle d}</annotation>

</semantics>

</math></span><img src="./e85ff03cbe0c7341af6b982e47e9f90d235c66ab.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.216ex; height:2.176ex;" alt="{\displaystyle d}" loading="lazy"></span> as the duration of darkness between flashes in the same group (unchanged from group flashing lights).</li>

<msup>

</msup>

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle d'}</annotation>

</semantics>

</math></span><img src="./1f310a68106a9e308bdaf887ff8f7171c4cb9d96.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.903ex; height:2.509ex;" alt="{\displaystyle d'}" loading="lazy"></span> as the duration of darkness between the first group of flashes and second group of flashes in a period.</li>

<msup>

</msup>

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle d''}</annotation>

</semantics>

</math></span><img src="./15e8c7dcc9a43913fde2c78b41e78e91897fc0af.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.355ex; height:2.509ex;" alt="{\displaystyle d''}" loading="lazy"></span> as the duration of darkness between the second group of flashes of one period, and the first group of flashes of the next period.</li></ul>

<p>The IALA Marine Buoyage System specifies composite group flashing lights be used for the following purposes:<sup id="cite_ref-:0_2-7" class="reference"><a href="#cite_note-:0-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>

</p>

<ul><li>Port hand preferred channel marks, if the composite group flashing light has a colour of red, there are 2 flashes followed by 1 flash and the mark is in region "A".</li>

<li>Starboard hand preferred channel marks, if the composite group flashing light has a colour of green, there are 2 flashes followed by 1 flash and the mark is in region "A".</li>

<li>Port hand preferred channel marks, if the composite group flashing light has a colour of green, there are 2 flashes followed by 1 flash and the mark is in region "B".</li>

<li>Starboard hand preferred channel marks, if the composite group flashing light has a colour of red, there are 2 flashes followed by 1 flash and the mark is in region "B".</li></ul>

<p>The IALA Marine Buoyage System allows (but does not mandate) composite group flashing lights to be used for special marks if the light colour if yellow.<sup id="cite_ref-:0_2-8" class="reference"><a href="#cite_note-:0-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>

</p><p>IALA recommendation R0110 specifies the following differences with group flashing lights:<sup id="cite_ref-:1_4-9" class="reference"><a href="#cite_note-:1-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

</p>

<ul><li>Composite group flashing lights have a period of repetition <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle p}">

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle p}</annotation>

</semantics>

</math></span><img src="./81eac1e205430d1f40810df36a0edffdc367af36.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; margin-left: -0.089ex; width:1.259ex; height:2.009ex;" alt="{\displaystyle p}" loading="lazy"></span> of no more than 30 seconds.</li>

<li>The first group of flashes in a composite group flashing light period should only consist of two flashes. By exception, the recommendation also allows the first group to consist of three flashes.</li>

<li>The second group of flashes in a composite group flashing light period should only consist of one flash.</li>

<li>Composite group flashing lights should adhere to constraint <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle d''\geq d'}">

<msup>

</msup>

<msup>

</msup>

</mstyle>

</mrow>

<annotation encoding="application/x-tex">{\displaystyle d''\geq d'}</annotation>

</semantics>

</math></span><img src="./9748971f271af4dc3a496a475a6454314b01ac54.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:7.357ex; height:2.676ex;" alt="{\displaystyle d''\geq d'}" loading="lazy"></span>. For a typical "Fl(2+1)" light, the period of darkness between a single flash and group of two flashes must be at least the same duration of darkness (but could be longer) as exists between a group of two flashes and a single flash.</li></ul>

<div class="mw-heading mw-heading3"><h3 id="Occulting_light">Occulting light</h3></div>

<p>An occulting light is a rhythmic light in which the duration of light in each period is longer than the total duration of darkness. In other words, it is the opposite to a flashing light where the total duration of darkness is longer than the duration of light. It has the appearance of flashing off, rather than flashing on. Like a flashing light, it can be used for a single occulting light that exhibits only a single period of darkness or the periods of darkness can be grouped and repeated at regular intervals (abbreviated "Oc"), a group (Oc(3)) or a composite group (Oc(2+1)).

</p><p>The term <a href="Occulting" class="mw-redirect" title="Occulting">occulting</a> is used because originally the effect was obtained by a mechanism (e.g. a vertical or rotating shutter) periodically shading the light from view.

</p>

<div class="mw-heading mw-heading3"><h3 id="Isophase_light">Isophase light</h3></div>

<p>An isophase light, abbreviated "Iso", is a light which has dark and light periods of equal length. The prefix derives from the Greek <i>iso-</i> meaning "same".

</p>

<div class="mw-heading mw-heading3"><h3 id="Quick_light">Quick light</h3></div>

<p>A quick light, abbreviated "Q", is a special case of a flashing light with a high frequency (more than 30<sup id="cite_ref-LLQuick_5-0" class="reference"><a href="#cite_note-LLQuick-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> or 50<sup id="cite_ref-LoL_6-0" class="reference"><a href="#cite_note-LoL-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> per minute). If the sequence of flashes is interrupted by regularly repeated eclipses of constant and long duration, the light is denoted "interrupted quick", abbreviated "I.Q".

</p><p>Group notation similar to flashing and occulting lights is also sometimes<sup id="cite_ref-LoL_6-1" class="reference"><a href="#cite_note-LoL-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> used, e.g. Q(9).

</p><p>Another distinction sometimes<sup id="cite_ref-LoL_6-2" class="reference"><a href="#cite_note-LoL-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> made is between quick (more than 50 and less than 80 <a href="Flashes_per_minute" class="mw-redirect" title="Flashes per minute">flashes per minute</a>), very quick (more than 80 and less than 160 flashes per minutes, abbreviated "V.Q") and ultra quick (no less than 160 flashes per minute, abbreviate "U.Q"). This can be combined with notations for interruptions, e.g. I.U.Q for interrupted ultra quick, or grouping, e.g. V.Q(9) for a very quick group of nine flashes. Quick characteristics can also be followed by other characteristics, e.g. VQ(6) LFl for a very quick group of six flashes, followed by a long flash.

</p>

<div class="mw-heading mw-heading3"><h3 id="Morse_code">Morse code</h3></div>

<p>A Morse code light is light in which appearances of light of two clearly different durations (dots and dashes) are grouped to represent a character or characters in the <a href="Morse_Code" class="mw-redirect" title="Morse Code">Morse Code</a>. For example, "Mo(A)" is a light in which in each period light is shown for a short period (dot) followed by a long period (dash), the Morse Code for "A".

</p>

<div class="mw-heading mw-heading3"><h3 id="Fixed_and_flashing">Fixed and flashing</h3></div>

<p>A fixed and flashing light, abbreviated "F. Fl", is a light in which a fixed low intensity light is combined with a flashing high intensity light.

</p>

<div class="mw-heading mw-heading3"><h3 id="Alternating">Alternating</h3></div>

<p>An alternating light, abbreviated "Al", is a light which shows alternating colors. For example, "Al WG" shows white and green lights alternately.

</p>

<div class="mw-heading mw-heading2"><h2 id="Class_of_light">Class of light</h2></div>

<caption>Table with Light Character examples

</caption>

<th style="background:#efefef; height:20px; width:120px;">Light Type

</th>

<th style="background:#efefef; width:40px">Abbr.

</th>

<th style="background:#efefef;">General Description

</th>

<th style="background:#efefef; width:100px">Example

</th>

<th style="background:#efefef; width:30px;">Dome

</th>

<th style="background:#efefef;"><span typeof="mw:File"></span><br><small><i>[Cycle period in seconds / Flash duration]</i></small>

</th></tr>

<tr>

<td align="left"><b>1. Fixed Light</b>

</td>

<td align="center">F

</td>

<td align="left">A continuous, steady, light.

</td>

</td>

</td>

<td>

</td></tr>

<tr>

</td></tr>

<tr>

<td><b>2. Occulting Light</b><br>The total duration of light in each period is greater than the total duration of darkness and the dark intervals (occultations) usually have the same duration.

</td></tr></tbody></table>

</td></tr>

<tr>

<td align="left"><b>2.1 Single-occulting</b>

</td>

<td align="center">Oc

</td>

<td align="left">A dark period is repeated regularly.

</td>

</td>

</td>

<td>

</td></tr>

<tr>

<td align="left"><b>2.2 Group-occulting</b>

</td>

<td align="center">Oc(x)

</td>

<td align="left">A group of dark periods are repeated regularly.

</td>

</td>

</td>

<td>

</td></tr>

<tr>

<td align="left"><b>2.3 Composite group-occulting</b>

</td>

<td align="center">Oc(x+y)

</td>

<td align="left">Light similar to group-occulting, except that successive groups in the same period contain different numbers of dark periods.

</td>

</td>

</td>

<td>

</td></tr>

<tr>

</td></tr>

<tr>

<td align="left"><b>3. Isophase Light</b>

</td></tr></tbody></table>

</td>

<td align="center">Iso

</td>

<td align="left">The duration of the light and dark periods are equal.

</td>

</td>

</td>

<td>

</td></tr>

<tr>

</td></tr>

<tr>

<td><b>4. Flashing Light</b><br>The total duration of light in each period is less than the total duration of the dark and light appearances (flashes) usually have the same duration.

</td></tr></tbody></table>

</td></tr>

<tr>

<td align="left"><b>4.1 Single-flashing</b>

</td>

<td align="center">Fl

</td>

<td align="left">A flash is repeated regularly at a rate below 50 per minute.

</td>

</td>

</td>

<td>

</td></tr>

<tr>

<td align="left"><b>4.2 Long-flashing</b>

</td>

<td align="center">L.Fl

</td>

<td align="left">A light flash, duration of more than 2 seconds (long flash) is repeated regularly.

</td>

</td>

</td>

<td>

</td></tr>

<tr>

<td align="left"><b>4.3 Group-flashing</b>

</td>

<td align="center">Fl(x)

</td>

<td align="left">A group of a specific number of flashes are repeated regularly.

</td>

</td>

</td>

</td></tr>

<tr>

<td align="left"><b>4.4 Composite group-flashing</b>

</td>

<td align="center">Fl(x+y)

</td>

<td align="left">Similar to group-flashing, but with several groups of flashes.

</td>

</td>

</td>

</td></tr>

<tr>

</td></tr>

<tr>

<td><b>5. Quick Flashing Light</b><br>flashes are at a frequency of between 50 and 79 flashes per minute.

</td></tr></tbody></table>

</td></tr>

<tr>

<td align="left"><b>5.1 Quick flashing</b><br>

</td>

<td align="center">Q

</td>

<td align="left">Quick flashes are repeated regularly.

</td>

</td>

</td>

</td></tr>

<tr>

<td align="left"><b>5.2 Group quick flashing</b><br>

</td>

<td align="center">Q(x)

</td>

<td align="left">Groups of a given number of quick flashes are repeated regularly.

</td>

</td>

</td>

</td></tr>

<tr>

</td>

<td align="center">Q(x)+L.Fl.

</td>

<td align="left">Groups of a given number of quick flashes are repeated regularly extended with a long Flash.

</td>

</td>

</td>

</td></tr>

<tr>

<td align="left"><b>5.3 Interrupted quick flashing</b><br>

</td>

<td align="center">I.Q

</td>

<td align="left">The sequence of flashes is regularly interrupted by dark intervals of constant duration.

</td>

</td>

</td>

</td></tr>

<tr>

</td></tr>

<tr>

<td><b>6. Very Quick Flashing Light</b><br>Flashes are repeated at a frequency between 80 and 159 flashes per minute.

</td></tr></tbody></table>

</td></tr>

<tr>

<td align="left"><b>6.1 Very Quick flashing</b><br>

</td>

<td align="center">VQ

</td>

<td align="left">Very quick flashes are repeated regularly.

</td>

</td>

</td>

</td></tr>

<tr>

<td align="left"><b>6.2 Group Very Quick flasing</b><br>

</td>

<td align="center">VQ(x)

</td>

<td align="left">Groups of a given number of very quick flashes are repeated regularly.

</td>

</td>

</td>

</td></tr>

<tr>

</td>

<td align="center">VQ(x)+LFl.

</td>

<td align="left">Groups of a given number of very quick flashes are repeated regularly and a long Flash.

</td>

</td>

</td>

</td></tr>

<tr>

<td align="left"><b>6.3 Interrupted Very quick flashing</b><br>

</td>

<td align="center">I.VQ

</td>

<td align="left">The sequence of flashes is regularly interrupted by dark intervals of constant duration.

</td>

</td>

</td>

</td></tr>

<tr>

</td></tr>

<tr>

<td><b>7. Ultra Quick flashing</b><br>The flashes are repeated at a frequency equal to or greater than 160 flashes per minute.

</td></tr></tbody></table>

</td></tr>

<tr>

<td align="left"><b>7.1 Ultra Quick flashing</b>

</td>

<td align="center">UQ

</td>

<td align="left">Ultra quick flashes are repeated regularly.

</td>

</td>

</td>

</td></tr>

<tr>

<td align="left"><b>7.2 Interrupted Ultra Quick flasing</b>

</td>

<td align="center">I.UQ

</td>

<td align="left">The sequence of ultra quick flashes is regularly interrupted by dark intervals of constant duration.

</td>

</td>

</td>

</td></tr>

<tr>

</td></tr>

<tr>

<td><b>8. Morse code</b>

</td></tr></tbody></table>

</td>

<td align="center">Mo(x)

</td>

<td align="left">The flashes have markedly different durations and are grouped together to form one or more characters in <a href="Morse_code" title="Morse code">Morse code</a>.

</td>

</td>

</td>

</td></tr>

<tr>

</td></tr>

<tr>

<td><b>9. Fixed and flashing</b><br>

</td></tr></tbody></table>

</td>

<td align="center">F.Fl

</td>

<td align="left">A light that combines a fixed light with a light flashing with a stronger intensity. The flashes of light may have any of the features described in above.

</td>

</td>

</td>

</td></tr>

<tr>

</td></tr>

<tr>

<td align="left"><b>10. Alternating</b>

</td></tr></tbody></table>

</td>

<td align="center">Al

</td>

<td align="left">Light that alternately displays different colors <br> Note - The alternating light can be used in conjunction with most of the lights earlier classes.

</td>

</td>

</td>

</td></tr></tbody></table>

/* start https://en.wikipedia.org/ */

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<ul><li><a href="Lighthouse" title="Lighthouse">Lighthouse</a></li>

<li><a href="Pilotage" class="mw-redirect" title="Pilotage">Pilotage</a></li>

<li><a href="Sector_light" title="Sector light">Sector light</a></li>

<li><a href="Signal_lamp" title="Signal lamp">Signal lamp</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2></div>

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/* start https://en.wikipedia.org/ */

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/* end https://en.wikipedia.org/ */

</style><cite id="CITEREFThompson" class="citation web cs1">Thompson, William. <a rel="nofollow" class="external text" href="https://zapatopi.net/kelvin/papers/on_lighthouse_characteristics.html">"On Lighthouse Characteristics"</a><span class="reference-accessdate">. Retrieved <span class="nowrap">21 August</span> 2022</span>.</cite></span>

</li>

<li id="cite_note-:0-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-:0_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:0_2-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-:0_2-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-:0_2-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-:0_2-4"><sup><i><b>e</b></i></sup></a> <a href="#cite_ref-:0_2-5"><sup><i><b>f</b></i></sup></a> <a href="#cite_ref-:0_2-6"><sup><i><b>g</b></i></sup></a> <a href="#cite_ref-:0_2-7"><sup><i><b>h</b></i></sup></a> <a href="#cite_ref-:0_2-8"><sup><i><b>i</b></i></sup></a></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.iala.int/product/r1001/">"R1001 The IALA Maritime Buoyage System"</a>. <i>International Association of Marine Aids to Navigation and Lighthouse Authorities</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2025-07-09</span></span>.</cite></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"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.iala.int/product/r0201/">"R0201 Marine Signal Lights-Colours (E200-1)"</a>. <i>International Association of Marine Aids to Navigation and Lighthouse Authorities</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2025-07-09</span></span>.</cite></span>

</li>

<li id="cite_note-:1-4"><span class="mw-cite-backlink">^ <a href="#cite_ref-:1_4-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:1_4-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-:1_4-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-:1_4-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-:1_4-4"><sup><i><b>e</b></i></sup></a> <a href="#cite_ref-:1_4-5"><sup><i><b>f</b></i></sup></a> <a href="#cite_ref-:1_4-6"><sup><i><b>g</b></i></sup></a> <a href="#cite_ref-:1_4-7"><sup><i><b>h</b></i></sup></a> <a href="#cite_ref-:1_4-8"><sup><i><b>i</b></i></sup></a> <a href="#cite_ref-:1_4-9"><sup><i><b>j</b></i></sup></a></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.iala.int/product/r0110/">"R0110 – Rhythmic Characters of Lights on Aids to Navigation"</a>. <i>International Association of Marine Aids to Navigation and Lighthouse Authorities</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2025-07-09</span></span>.</cite></span>

</li>

<li id="cite_note-LLQuick-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-LLQuick_5-0">^</a></b></span> <span class="reference-text"><i>Light List</i> states at one point that only "frequency not exceeding 30 flashes per minute" is considered "Flashing", yet at another that only "a rate of 60 flashes per minute" is considered "Quick", leaving the interval in-between undefined.</span>

</li>

<li id="cite_note-LoL-6"><span class="mw-cite-backlink">^ <a href="#cite_ref-LoL_6-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-LoL_6-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-LoL_6-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><i>List of Lights</i></span>

</li>

</ol></div></div>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

/* start https://en.wikipedia.org/ */

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<ul><li><cite class="citation book cs1"><a rel="nofollow" class="external text" href="https://msi.nga.mil/Publications/USCGLL"><i>Light List, Volumes 1-7</i></a>. <a href="United_States_Coast_Guard" title="United States Coast Guard">United States Coast Guard</a>.</cite> - Glossary to Aids of Navigation Terms in any of the volumes</li>

<li><cite id="CITEREFNGA" class="citation book cs1"><a rel="nofollow" class="external text" href="https://msi.nga.mil/Publications/NGALOL"><i>Limits of List of Lights, </i>Pubs. 110–116<i></i></a>. <a href="National_Geospatial-Intelligence_Agency" title="National Geospatial-Intelligence Agency">United States National Geospatial-Intelligence Agency</a>.</cite> p. XII - Characteristics of Lights, in any of the volumes</li>

<li><a rel="nofollow" class="external text" href="http://www.seathelights.com/other/glossary.html">Glossary of Lighthouse Terms </a></li></ul>

</div>

<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

<ul><li><a rel="nofollow" class="external text" href="https://www.enschrage.nl/tech/1characters.html">Light Characteristics</a></li>

<li><a rel="nofollow" class="external text" href="https://www.enschrage.nl/index.html">The Scottish Lighthouses</a></li></ul>

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</style></div><div role="navigation" class="navbox" aria-labelledby="Lighthouses676" style="padding:3px"><table class="nowraplinks hlist mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="3"><style data-mw-deduplicate="TemplateStyles:r1239400231">

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</style><div id="Lighthouses676" style="font-size:114%;margin:0 4em"><a href="Lighthouse" title="Lighthouse">Lighthouses</a></div></th></tr><tr><td class="navbox-abovebelow" colspan="3"><div>

<ul><li><a href="History_of_lighthouses" title="History of lighthouses">History of lighthouses</a></li>

<li><a href="Conservation_and_restoration_of_lighthouses" title="Conservation and restoration of lighthouses">Conservation of lighthouses</a></li>

<li><a href="Lighthouse_museum" title="Lighthouse museum">Museums</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Types</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%">Construction</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="Aerial_lighthouse" class="mw-redirect" title="Aerial lighthouse">Aerial</a></li>

<li><a href="Caisson_lighthouse" title="Caisson lighthouse">Caisson</a></li>

<li><a href="Integral_lighthouse" title="Integral lighthouse">Integral</a></li>

<li><a href="Screw-pile_lighthouse" title="Screw-pile lighthouse">Screw-pile</a></li>

<li><a href="Skeletal_tower" title="Skeletal tower">Skeletal tower</a></li>

<li><a href="Lightvessel" class="mw-redirect" title="Lightvessel">Vessel</a> (acting)</li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Navigational purpose</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="Daymark" title="Daymark">Daymark</a></li>

<li><a href="Leading_lights" title="Leading lights">Leading lights</a></li>

<li><a href="Sector_light" title="Sector light">Sector light</a></li></ul>

</div></td></tr></tbody></table><div></div></td><td class="noviewer navbox-image" rowspan="6" style="width:1px;padding:0 0 0 2px"><div><span typeof="mw:File"></span></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Fixtures</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="Aerobeacon" title="Aerobeacon">Aerobeacon</a></li>

<li><a href="Argand_lamp" title="Argand lamp">Argand lamp</a></li>

<li><a href="Automatic_lamp_changer" title="Automatic lamp changer">Automatic lamp changer</a></li>

<li><a href="Bird-cage_lantern" title="Bird-cage lantern">Bird-cage lantern</a></li>

<li><a href="Carcel_lamp" title="Carcel lamp">Carcel lamp</a></li>

<li><a href="Dal%C3%A9n_light" title="Dalén light">Dalén light</a></li>

<li><a href="Foghorn" title="Foghorn">Foghorn</a></li>

<li><a href="Fresnel_lens" title="Fresnel lens">Fresnel lens</a></li>

<li><a href="Lens_lantern" title="Lens lantern">Lens lantern</a></li>

<li><a href="Lewis_lamp" title="Lewis lamp">Lewis lamp</a></li>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Maintenance</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="Lighthouse_keeper" title="Lighthouse keeper">Keepers</a></li>

<li><a href="Light_dues" title="Light dues">Light dues</a></li>

<li><a href="Pharology" title="Pharology">Pharologists</a></li>

<li><a href="Lighthouse_tender" title="Lighthouse tender">Tender</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="Lists_of_lighthouses#Africa" title="Lists of lighthouses">Africa</a></li>

<li><a href="Lists_of_lighthouses#Antarctica" title="Lists of lighthouses">Antarctica</a></li>

<li><a href="Lists_of_lighthouses#Europe" title="Lists of lighthouses">Europe</a></li>

<li><a href="Lists_of_lighthouses#North_America" title="Lists of lighthouses">North America</a></li>

<li><a href="Lists_of_lighthouses#Oceania" title="Lists of lighthouses">Oceania</a></li>

<li><a href="Lists_of_lighthouses#South_America" title="Lists of lighthouses">South America</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Categories</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li>Lighthouse builders</li>

<li>Lighthouses by heritage register</li>

<li>Lighthouses by century of completion</li>

<li>Lighthouses by year of completion</li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Global<br>organizations</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="General_lighthouse_authority" title="General lighthouse authority">General lighthouse authority</a></li>

<li><a href="International_Association_of_Marine_Aids_to_Navigation_and_Lighthouse_Authorities" title="International Association of Marine Aids to Navigation and Lighthouse Authorities">International Association of Lighthouse Authorities</a></li>

<li><a href="International_Lighthouse_and_Lightship_Weekend" title="International Lighthouse and Lightship Weekend">International Lighthouse and Lightship Weekend</a></li>

<li><i><a href="Lighthouse_Digest" title="Lighthouse Digest">Lighthouse Digest</a></i></li></ul>

</div></td></tr><tr><td class="navbox-abovebelow" colspan="3" style="font-weight:bold;"><div>

<ul><li><span class="noviewer" typeof="mw:File"><span title="Category"></span></span> Category</li>

<li><span class="noviewer" typeof="mw:File"><span title="Commons page"></span></span> <a href="https://commons.wikimedia.org/wiki/Category:Lighthouses" class="extiw external" title="commons:Category:Lighthouses">Commons</a></li>

<li><span class="noviewer" typeof="mw:File"></span> <a href="https://en.wiktionary.org/wiki/lighthouse" class="extiw external" title="wikt:lighthouse">Wiktionary</a></li>

<li><span class="noviewer" typeof="mw:File"><span title="WikiProject"></span></span> WikiProject</li></ul>

</div></td></tr></tbody></table></div></div><div><div class="zim-footer">

This article is issued from <a class="external text" title="Last edited on 2025-07-26" href="https://en.wikipedia.org/wiki/?title=Light_characteristic&oldid=1302604005">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

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