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href="http://www.zytrax.com/security/" class="t-da">Security</a></li> </ul> </div>  </div>  <div class="l-c">  <p class="adv"> <script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>  <ins class="adsbygoogle" style="display:inline-block;width:728px;height:90px" data-ad-client="ca-pub-9419480011552853" data-ad-slot="9281933980"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> </p> <h1>Tech Stuff - Mechanical - Threads</h1> <p>The following notes apply to what are called <b>machine screws</b> or <b>fasteners</b> for commericial grade applications. Wood and other screw types are defined using slightly different terminology. Aerospace/Military applications have another level of <a href="#aerospace" class="t-db">detail</a> that defines the internal and external thread characteristics and it gets horribly complicated, very quickly.</p> <p>When you specify fasteners (a.k.a. screws to the rest of us) you have a lot of stuff to define:</p> <ol> <li>The <a title="" href="heads.htm" class="t-db">head style and type</a>.</li> <li>The length required specified in inches, fractions of inches or millimeters.</li> <li>The diameter - when measuring in inches for diameters less than 1/4" there is a gauge number (a.k.a. gage number), above that specify the diameter in fractions of an inch. For metric the diameter is specified in millimeters.</li> <li>The thread pitch - distance between threads. Defined as <b>Threads-per-Inch (TPI)</b> or frequently simply as the <b>Pitch</b> (though technically this the distance between adjacent threads). UNC, UNF and Metric define standard values. To convert from inches (TPI) to millimeters (pitch) divide 25.4 by the Thread-per-Inch (TPI) value, thus a fastener with a TPI of 32 will give 0.793mm (0.8) and one with a TPI of 56 will give 0.45mm.</li> <li>The material - brass, stainless steel, non-ferous such as nylon and other polyamides.</li> </ol> <h2>UNC, UNF and Metric</h2> <p>Inch sizes come in either Unified Coarse (UNC) or Unified Fine (UNF) which define the number of threads per inch (TPI) which are typically standardized based on the <a title="" href="#gauge" class="t-db">Gauge</a> (the fastener's diameter).</p> <p>So you could specify a small fastener as being 4-40 which from the table below indicates a Unified Coarse (UNC) (its UNF equivalent is 4-48) or 8-36 which is UNF (its UNC equivalent is 8-32). A larger fastener would be 1/4-28 (UNF) or 1/4-20 (UNC).</p> <p>The diameter is measured at the outside of the thread (some manufacturers refer to a pitch diameter which is measured to the inside of the thread).</p> <p>Metric screws are much simpler to specify being <b>Maa x bb</b> where <b>aa</b> is the diameter in millimeters (mm) and <b>bb</b> is the <b>pitch</b> - the distance in millimeters (mm) between threads. So <b>M3.5 x 0.6</b> has a 3.5mm diameter and a pitch of 0.6 mm. <a title="" href="#metric" class="t-db">Standard metric sizes with closest UNC and UNF equivalents</a>.</p> <p><b>Note:</b> British threads use the <b>Whitworth</b> (more correctly <b>BSW</b> - <b>British Standard Whitworth</b>) standard. Whitworth threads use a 55° with rounded ends, whereas UNC/UNF and metric threads use a 60° with flat ends.</p> <h2 id="gauge">Gauge and Inch Sizes</h2> <p>Gauge numbers are used for diameters less than 1/4" inch. Above that they are defined by the diameter in fractions of an inch in increments of 1/16 up to 5/8 then in increments of 1/8.</p> <p>The table below shows the normal standards but there are lots of exceptions and non-standard sizes offered by multiple manufacturers. TPI is threads per inch and is given for UNC (Unified Coarse) and UNF (Unified Fine). Nut sizes appear less codified but are typically given as size in fractions across the flats. Clearly, you also need to specify the threads per inch count for nuts.</p> <table class="t-m-s"> <tr class="g-h-n"> <td>Gauge No.</td> <td>Decimal<br>Inches<br>(Dia.)</td> <td>UNC TPI</td> <td>Short Form</td> <td>UNF TPI</td> <td>Short Form</td> <td>NUT Size</td> <td>Millimeters (mm)<br>Approx.</td> </tr> <tr > <td>No.0000</td> <td>0.021</td> <td>160</td> <td>-</td> <td>-</td> <td>-</td> <td>-</td> <td>0.53</td> </tr> <tr > <td>No.000</td> <td>0.034</td> <td>120</td> <td>-</td> <td>-</td> <td>-</td> <td>3/32"</td> <td>0.86</td> </tr> <tr > <td>No.00</td> <td>0.047</td> <td>90</td> <td>-</td> <td>-</td> <td>-</td> <td>3/32</td> <td>1.19</td> </tr> <tr > <td>No.0</td> <td>0.060</td> <td>-</td> <td>-</td> <td>80</td> <td>-</td> <td>5/32"</td> <td>1.524</td> </tr> <tr > <td>No.1</td> <td>0.073</td> <td>64</td> <td>UNC 1-64</td> <td>72</td> <td>UNF 1-72</td> <td>5/32"</td> <td>1.854</td> </tr> <tr > <td>No.2</td> <td>0.086</td> <td>56</td> <td>UNC 2-56</td> <td>64</td> <td>UNF 2-64</td> <td>3/16"</td> <td>2.184</td> </tr> <tr > <td>No.3</td> <td>0.099</td> <td>48</td> <td>UNC 3-48</td> <td>56</td> <td>UNF 3-56</td> <td>3/16"</td> <td>2.515</td> </tr> <tr > <td>No.4</td> <td>0.112</td> <td>40</td> <td>UNC 4-40</td> <td>48</td> <td>UNF 4-48</td> <td>1/4"</td> <td>2.845</td> </tr> <tr > <td>No.5</td> <td>0.125</td> <td>40</td> <td>UNC 5-40</td> <td>44</td> <td>UNF 5-44</td> <td>1/4"</td> <td>3.175</td> </tr> <tr > <td>No.6</td> <td>0.138</td> <td>32</td> <td>UNC 6-32</td> <td>40</td> <td>UNF 6-40</td> <td>5/16"</td> <td>3.505</td> </tr> <tr > <td>No.8</td> <td>0.164</td> <td>32</td> <td>UNC 8-32</td> <td>36</td> <td>UNF 8-36</td> <td>11/32"</td> <td>4.166</td> </tr> <tr > <td>No.10</td> <td>0.190</td> <td>24</td> <td>UNC 10-24</td> <td>32</td> <td>UNF 10-32</td> <td>3/8"</td> <td>4.826</td> </tr> <tr > <td>No.12</td> <td>0.216</td> <td>24</td> <td>UNC 12-24</td> <td>28</td> <td>UNF 12-28</td> <td>7/16"</td> <td>5.486</td> </tr> <tr > <td>1/4"</td> <td>0.250</td> <td>20</td> <td>-</td> <td>28</td> <td>-</td> <td>7/16"</td> <td>6.349</td> </tr> </table> <h2 id="metric">Metric Sizes</h2> <p>The metric size gives both the diameter and <b>Pitch</b> as <b>Maa x bb</b> where <b>aa</b> is the diameter in millimeters (mm) and <b>bb</b> is the <b>Pitch</b> - the distance in millimeters (mm) between threads. So <b>M3.5 x 0.6</b> has a 3.5mm diameter and a pitch of 0.6mm. To convert from inches to millimeters divide 25.4 by the Thread-per-Inch (TPI) value, thus a fastener with a TPI of 32 will give 0.793mm (0.8) and one with a TPI of 56 will give 0.45mm.</p> <p>For convenience we show the closest UNC and UNF sizes.</p> <table class="t-m-n"> <tr class="g-h-n"> <td>Metric</td> <td>UNC</td> <td>UNF</td> </tr> <tr> <td>M2 x 0.4</td> <td>1-64</td> <td>1-72</td> </tr> <tr > <td>M2.5 x 0.45</td> <td>3-48</td> <td>3-56</td> </tr> <tr > <td>M3 x 0.5</td> <td>4-40</td> <td>4-48</td> </tr> <tr > <td>M3.5 x 0.6</td> <td>6-32</td> <td>6-40</td> </tr> <tr > <td>M4 x 0.7</td> <td>8-32</td> <td>8-36</td> </tr> <tr > <td>M5 x 0.8</td> <td>10-24</td> <td>10-32</td> </tr> <tr> <td>M5.5 x 0.5</td> <td>12-24</td> <td>12-28</td> </tr> <tr > <td>M6 x 1</td> <td>1/4-20</td> <td>1/4-28</td> </tr> </table> <h2 id="aerospace">Aeropsace/Military Designations</h2> <p>The following - incomplete - list extends the normal UNC/UNF designations for aerospace/military applications:</p> <ul> <li>UNJC = Unified National Coarse thread with external thread controlled root radius</li> <li>UNJF = Unified National Fine thread with external thread controlled root radius</li> <li>UNEF = Unified National Extra Fine thread</li> <li>UNJEF = Unified National Extra Fine thread with external thread controlled root radius</li> </ul> <hr> <p class="p-m-n"><br>Problems, comments, suggestions, corrections (including broken links) or something to add? 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You will have a warm inner glow for the rest of the day.</p>  </div> <div class="l-l">  <div class="n-l"> <p class="c-g t-b t-o m-h5 t-r">Tech Stuff</p>  <ul class="n-l1p"> <li class="n-l1p-e"> <a href="http://www.zytrax.com/tech" class="n-l-c">tech home</a> </li> </ul> <ul class="n-l1p"> <li class="n-l1p-e"> <a title="Digital Audio - primers, calculators, equalization, frequency tables, file formats, glossary - a mere splash in the ocean" href="http://www.zytrax.com/tech/audio/" class="n-l-c">audio stuff</a> <ul class="n-l2"> <li class="n-l2-e"><a href="http://www.zytrax.com/tech/audio/sound.html" class="n-l-f">sound primer</a></li> <li class="n-l2-e"><a href="http://www.zytrax.com/tech/audio/digital-sound.html" class="n-l-f">digital primer</a></li> <li class="n-l2-e"><a href="http://www.zytrax.com/tech/audio/audio.html" class="n-l-f">note frequencies</a></li> <li class="n-l2-e"><a href="http://www.zytrax.com/tech/audio/equalization.html" class="n-l-f">eq, meters & fft</a></li> <li class="n-l2-e"><a href="http://www.zytrax.com/tech/audio/calculator.html" class="n-l-f">calculators</a></li> <li class="n-l2-e"><a href="http://www.zytrax.com/tech/audio/formats.html" class="n-l-f">files & codecs</a></li> <li class="n-l2-e"><a href="http://www.zytrax.com/tech/audio/glossary.html" class="n-l-f">glossary</a></li> </ul> </li> </ul> <ul class="n-l1p"> <li class="n-l1p-e"> <a title="Browser IDs, SSIs, Apache Configuration, regular expressions" href="http://www.zytrax.com/tech/web/" class="n-l-c">web stuff</a> <ul class="n-l2"> <li class="n-l2-e"><a href="http://www.zytrax.com/tech/web/browser_ids.htm" class="n-l-f">browser ids</a></li> <li class="n-l2-e"><a href="http://www.zytrax.com/tech/web/mobile_ids.html" class="n-l-f">mobile_ids</a></li> <li class="n-l2-e"><a href="http://www.zytrax.com/tech/web/env_var.htm" class="n-l-f">apache env vars</a></li> <li class="n-l2-e"><a href="http://www.zytrax.com/tech/web/ssi.htm" class="n-l-f">apache ssi</a></li> <li class="n-l2-e"><a href="http://www.zytrax.com/tech/css/workarounds.html#popout" class="n-l-f">css popout menus</a></li> <li class="n-l2-e"><a title="most of those annoying HTML entity codes that we forget all the time" href="http://www.zytrax.com/tech/web/entities.html" class="n-l-f">html entities</a></li> <li class="n-l2-e"><a title="Decimal to Hexidecimal to Binary conversion - even Octal!" href="http://www.zytrax.com/tech/protocols/hex.html" class="n-l-f">dec > hex > bin</a></li> </ul> </li> </ul> <ul class="n-l1p"> <li class="n-l1p-e"> <a href="http://www.zytrax.com/tech/dom/" class="n-l-c">dom stuff</a><br> <ul class="n-l2"> <li class="n-l2-e"><a href="http://www.zytrax.com/tech/dom/guide.html" class="n-l-f">dom guide</a></li> <li class="n-l2-e"><a href="http://www.zytrax.com/tech/dom/w3c_dom.html" class="n-l-f">page explorer</a></li> <li class="n-l2-e"><a href="http://www.zytrax.com/tech/dom/navigate.html" class="n-l-f">dom navigation</a></li> </ul> </li> </ul> <ul class="n-l1p"> <li class="n-l1p-e"> <a title="CSS is about a lot more than STYLE. 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even a description of Octal!" href="http://www.zytrax.com/tech/protocols/hex.html" class="n-l-c">dec > hex > bin</a> </li> </ul> <ul class="n-l1p"> <li class="n-l1p-e"> <a title="character sets ain't as simple as they look" href="http://www.zytrax.com/tech/codes.htm" class="n-l-c">character sets</a> <ul class="n-l2"> <li title="pretty much all the characters sets in the known universe including utf-7, 8 and 16" class="n-l2-e"><a href="http://www.zytrax.com/tech/characters/" class="n-l-f">character sets</a></li> <li title="ascii variant of international reference alphabet 5 (ira5)" class="n-l2-e"><a href="http://www.zytrax.com/tech/codes.htm" class="n-l-f">ascii codes</a></li> <li title="international reference alphabet 5 (ascii's cousin)" class="n-l2-e"><a href="http://www.zytrax.com/tech/ia5.html" class="n-l-f">ia5 codes</a></li> <li title="all that ™ & © stuff" class="n-l2-e"><a href="http://www.zytrax.com/tech/web/entities.html" class="n-l-f">html entities</a></li> <li title="silly page containing a bunch of fonts in various sizes including your PCs defaults" class="n-l2-e"><a href="http://www.zytrax.com/tech/web/fonts.html" class="n-l-f">web fonts</a></li> </ul> </li> </ul> <ul class="n-l1p"> <li class="n-l1p-e"> <a title="The T series, E series and J series and then all that optical stuff (OC-12 etc.)" href="http://www.zytrax.com/tech/data_rates.htm" class="n-l-c">data rate stuff</a> </li> </ul> <ul class="n-l1p"> <li class="n-l1p-e"> <a title="Even us electronic guys gotta know how to screw it together, if you get our drift" href="http://www.zytrax.com/tech/mech/" class="n-l-c">mechanical stuff</a> <ul class="n-l2"> <li title="fastener (screw) head styles - surprising number of choices" class="n-l2-e"><a href="http://www.zytrax.com/tech/mech/heads.htm" class="n-l-f">head styles</a></li> <li title="threads for imperial (UNF, UNC) & metric sizes" class="n-l2-e"><a href="http://www.zytrax.com/tech/mech/threads.htm" class="n-l-f">threads</a></li> </ul> </li> </ul> <ul class="n-l1p"> <li class="n-l1p-e"> <a title="A collection of howtos including Samba3 as PDC, FreeBSD firewalls" href="http://www.zytrax.com/tech/howtos/" class="n-l-c">howto stuff</a> </li> </ul> <ul class="n-l1p"> <li class="n-l1p-e"> <a title="A collection of survival guides - quick overviews - to popular software" href="http://www.zytrax.com/tech/survival/" class="n-l-c">survival stuff</a> <ul class="n-l2"> <li title="tls and x.509 (ssl) certificates - warning: headache inducing stuff" class="n-l2-e"><a href="http://www.zytrax.com/tech/survival/ssl.html" class="n-l-f">ssl/tls/x.509</a></li> <li title="Abstract Syntax Notation. 1 (ASN.!) and Distinguished Encoding Rules (DER) - 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Pass the pain medication, we feel a headache coming on." class="n-l2-e"><a href="http://www.zytrax.com/tech/survival/asn1.html" class="n-l-f">ASN.1 & DER</a></li> <li title="Kerberos is great - but tough, oh my, tough stuff" class="n-l2-e"><a href="http://www.zytrax.com/tech/survival/kerberos.html" class="n-l-f">kerberos</a></li> <li title="We've used postfix for years but always forget which of the 27 million parameters to use" class="n-l2-e"><a href="http://www.zytrax.com/tech/survival/postfix.html" class="n-l-f">postfix</a></li> <li title="Symetric, asymetric, MACs, hashes - eye watering stuff" class="n-l2-e"><a href="http://www.zytrax.com/tech/survival/encryption.html" class="n-l-f">encryption</a></li> <li title="Just what time is it in Kuala Lumpur, and what's that got to do with cron?" class="n-l2-e"><a href="http://www.zytrax.com/tech/survival/cron.html" class="t-db">cron</a></li> <li title="Gotta love wxWidgets - free, fantastic, flexible - but hard to see the wood for the trees sometimes" class="n-l2-e"><a href="http://www.zytrax.com/tech/survival/wxwidgets.html" class="n-l-f">wxWidgets</a></li> </ul> </li> </ul> <ul class="n-l1p"> <li class="n-l1p-e"> <a title="Our wireless overview, Calculators, Fresnel zones, links to 'heavy' stuff, some early 802.11 stuff (mostly wi-fi related)" href="http://www.zytrax.com/tech/wireless/" class="n-l-c">wireless stuff</a> <ul class="n-l2"> <li title="our irreverent general intro to wirelss - purist will not like this page" class="n-l2-e"><a href="http://www.zytrax.com/tech/wireless/intro.htm" class="n-l-f">overview</a></li> <li title="wireless calculators for system budgets, free-space loss, fresnel effects and a bunch of other stuff" class="n-l2-e"><a href="http://www.zytrax.com/tech/wireless/calc.htm" class="n-l-f">calculators</a></li> <li title="fresnel effect explanation - well, we can understand it" class="n-l2-e"><a href="http://www.zytrax.com/tech/wireless/fresnel.htm" class="n-l-f">fresnel effects</a></li> <li title="our outrageously biased description of frequency hopping versus direct sequence for spread spectrum" class="n-l2-e"><a href="http://www.zytrax.com/tech/wireless/fh_ds.htm" class="n-l-f">fh vs ds</a></li> <li title="some terminology covering 802 standards and modulation techniques" class="n-l2-e"><a href="http://www.zytrax.com/tech/wireless/soup.html" class="n-l-f">wireless soup</a></li> </ul> </li> </ul> <ul class="n-l1p"> <li class="n-l1p-e"> <a title="Pinouts - USB, DIN, Firewire, VGA, DVI, HDMI, DisplayPort and Thunderbolt, I/O interface speeds, Screen sizes including HD" href="http://www.zytrax.com/tech/pc/" class="n-l-c">pc stuff</a> <ul class="n-l2"> <li title="din and mini-din for older PCs" class="n-l2-e"><a href="http://www.zytrax.com/tech/pc/din.htm" class="n-l-f">din & mini-din</a></li> <li title="802.3 LAN stuff" class="n-l2-e"><a href="http://www.zytrax.com/tech/layer_1/cables/tech_lan.htm" class="n-l-f">802.3 lan</a></li> <li title="connection of monitors has changed over the years from clunky VGA to svelte HDMI - all the pinouts you could hope for" class="n-l2-e"><a href="http://www.zytrax.com/tech/pc/monitors.htm" class="n-l-f">monitor pinouts</a></li> <li title="serial (db9, db24) connections - slow but trusty" class="n-l2-e"><a href="http://www.zytrax.com/tech/layer_1/cables/tech_rs232.htm" class="n-l-f">serial stuff</a></li> <li title="usb pinouts and descriptions of power levels for usb 1, 2 and 3 - also includes firewire" class="n-l2-e"><a href="http://www.zytrax.com/tech/pc/serial.html" class="n-l-f">usb & firewire</a></li> <li title="pc interfaces are changing and getting faster - we can never keep up - list of interfaces and their speeds" class="n-l2-e"><a href="http://www.zytrax.com/tech/pc/interfaces.html" class="n-l-f">pc interfaces</a></li> <li title="we get confused about most things - just what is 1080p - pc and tv screen resolution table with some explanations" class="n-l2-e"><a href="http://www.zytrax.com/tech/pc/resolution.html" class="n-l-f">screen resolutions</a></li> </ul> </li> </ul> <ul class="n-l1p"> <li class="n-l1p-e"> <a title="Electronic glossary, some old experiments with 3.3/5V protection and early BGA designs" href="http://www.zytrax.com/tech/electronics/" class="n-l-c">electronic stuff</a> </li> </ul> <ul class="n-l1p"> <li class="n-l1p-e"> <a title="ragbag collection of links that we publish from time to time - maybe useful, maybe not" href="http://www.zytrax.com/links" class="n-l-c">tech links</a> </li> </ul> <ul class="n-l1p"> <li class="n-l1p-e"> <a title="Our DNS and LDAP for Rocket Scientists guides" href="http://www.zytrax.com/books" class="n-l-c">open guides</a> <ul class="n-l2"> <li title="dns for rocket scientists" class="n-l2-e"><a href="http://www.zytrax.com/books/dns/" class="n-l-f">dns guide</a></li> <li title="ldap for rocket scientists" class="n-l2-e"><a href="http://www.zytrax.com/books/ldap/" class="n-l-f">ldap guide</a></li> </ul> </li> </ul> <p class="t-r"> <a title="RSS (2.0) Feed - 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You could, at no charge, upgrade to a W3C standards compliant browser such as <a href="http://www.mozilla.org" class="t-db">Firefox</a></p> </div> </div> <div class="l-r">  <div class="w-150">  <p class="c-g t-b t-o m-h8">Search</p> <form class="f-b-n" method="get" action="http://www.google.com/custom" target="_top"> <table> <tr> <td style="white-space: nowrap"> <input type="hidden" name="domains" value="www.zytrax.com"> <input class="b-lg" type="text" name="q" size="16" maxlength="255" value=""> </td></tr> <tr> <td style="white-space: nowrap"> <table> <tr> <td> <input type="radio" name="sitesearch" value="" checked="checked"><span class="t-s">web</span> </td> <td> <input type="radio" name="sitesearch" value="www.zytrax.com" ><span class="t-s">zytrax.com</span> </td> </tr> </table> <input class="b-lg" type="submit" name="sa" value="Google Search"> <input type="hidden" name="client" value="pub-9419480011552853"> <input type="hidden" name="forid" value="1"> <input type="hidden" name="ie" value="ISO-8859-1"> <input type="hidden" name="oe" value="ISO-8859-1"> <input type="hidden" name="safe" value="active"> <input type="hidden" name="cof" value="GALT:#008000;GL:1;DIV:#336699;VLC:663399;AH:center;BGC:FFFFFF;LBGC:336699;ALC:0000FF;LC:0000FF;T:000000;GFNT:0000FF;GIMP:0000FF;LH:50;LW:355;L:http://www.zytrax.com/images/zytrax-info-google.gif;S:http://www.zytrax.com/tech;FORID:1;"> <input type="hidden" name="hl" value="en"> </td></tr></table> </form>   <div class="t-h"><p><span class="t-g">Share</span></p> <div class="t-h-1"> Icons made by <a href="https://www.flaticon.com/authors/icomoon" title="Icomoon">Icomoon</a> from <a href="https://www.flaticon.com/" title="Flaticon">www.flaticon.com</a> is licensed by <a href="http://creativecommons.org/licenses/by/3.0/" title="Creative Commons BY 3.0" target="_blank">CC 3.0 BY</a></div></div> <a href="http://www.facebook.com/share.php?u=http://www.zytrax.com/tech/mech/threads.htm&h=Tech%20Stuff%20-%20Mechanical%20-%20Threads"><img class="w-32" title="add page to facebook" src="http://www.zytrax.com/images/facebook.png" alt="share page via facebook"></a> <a href="http://twitter.com/home/?status=Useful%20page%20http://www.zytrax.com/tech/mech/threads.htm"><img class="w-32" title="tweet this page" src="http://www.zytrax.com/images/twitter.png" alt="tweet this page"></a> <p class="c-g t-b t-o m-h5">Page<p> <a class="a-n" href="http://www.zytrax.com/feedback.htm"><img class="w-32" title="Page comment feature" src="http://www.zytrax.com/images/mail.png" alt="email us"></a> <a class="a-n" href="http://www.zytrax.com/run/mailpage.php"><img class="w-32" title="Send to a friend" src="http://www.zytrax.com/images/mailfriend.png" alt="Send to a friend feature"></a> <a class="a-n" href="#" onclick="window.print();return false;"><img class="w-32" title="print page" src="http://www.zytrax.com/images/printpage.png" alt="print this page"></a> <a class="a-n" title="View page full width - suppresses left and right hand menus" href="http://www.zytrax.com/tech/mech/threads.htm?pf=yes"><img class="w-32" src="http://www.zytrax.com/images/fullwidth.png" alt="Display full width page"></a> <a class="a-n" href="#" onclick="fontchange('d');return false;"><img class="w-32" title="Decrease font size" src="http://www.zytrax.com/images/smaller.png" alt="Decrease font size"></a> <a class="a-n" href="#" onclick="fontchange('i');return false;"><img class="w-32" title="Increase font size" src="http://www.zytrax.com/images/bigger.png" alt="Increase font size"></a> <p class="c-g t-b t-o m-h5">Standards</p> <p> <a href="http://www.iso.org" title="International Standards Organisation" target="_blank" class="w-db">ISO (International)</a><br> <a href="http://www.iec.ch" title="International Electrotechnical Commission" target="_blank" >IEC (International)</a><br> <a href="http://www.ansi.org" target="_blank" class="w-db">ANSI (US)</a><br> <a href="http://www.din.de/en" target="_blank" class="w-db">DIN (Germany)</a><br> <a href="http://www.etsi.org/" target="_blank" class="w-db">ETSI (EU)</a><br> <a href="http://www.bsigroup.com/en-GB" target="_blank" class="w-db">BSI (UK)</a><br> <a href="http://www.afnor.org/en" target="_blank" class="w-db">AFNOR (France)</a><br> </p> <p class="c-g t-b t-o m-h5">Telecom</p> <p> <a href="http://www.tiaonline.org" title="RS232 etc" target="_blank" class="w-db">TIA (US)</a><br> <a href="http://www.ecianow.org" target="_blank" class="w-db">ECIA (US)</a><br> <a href="http://www.itu.int" target="_blank" class="w-db">ITU (International)</a><br> <a href="http://www.ieee.org" target="_blank" class="w-db">IEEE (US)</a><br> <a href="http://www.etsi.org/" target="_blank" class="w-db">ETSI (EU)</a><br> <a href="http://www.ofcom.gov.uk/" target="_blank" class="w-db">OFCOM (UK)</a><br> </p> <p class="c-g t-b t-o m-h5">Internet</p> <p> <a href="http://www.ietf.org/" target="_blank" class="w-db">IETF</a><br> <a href="http://www.ietf.org/rfc.html" target="_blank" class="w-db">IETF-RFCs</a><br> <a href="http://www.iana.org/" target="_blank" class="w-db">IANA</a><br> <a href="http://www.icann.org/" target="_blank" class="w-db">ICANN</a><br> <a href="http://www.w3c.org/" target="_blank" class="w-db">W3C</a><br> </p> <p class="c-g t-b t-o m-h5">Electronics</p> <p> <a href="http://www.jedec.org" title="chip pacakaging, testing etc." target="_blank" class="w-db">JEDEC</a><br> <a href="http://www.ecianow.org" target="_blank" class="w-db">ECIA (US)</a><br> </p> </div> <p class="c-g t-b t-o">Site</p> <a class="a-n" href="http://www.zytrax.com/about_site.htm#css"><img class="w-32" src="http://www.zytrax.com/images/css.png" alt="CSS Technology"></a> <a class="a-n" href="http://www.zytrax.com/security/spf.html"><img title="SPF Record Conformant Domain" class="w-32" src="http://www.zytrax.com/images/spf.png" alt="SPF Record Conformant Domain"></a> </div> <div class="l-f">  <table> <tr> <td class="p-f-s t-l"> Copyright © 1994 - 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