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<title>Called subscriber identification</title>
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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Called subscriber identification</span></span>
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<p>A <b>called subscriber identification</b> (abbreviated <b>CSID</b>) is a string that identifies a specific <a href="Fax" title="Fax">fax</a> machine as the recipient of a fax.<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>
</p><p>This string (typically less than 40 characters) is usually a combination of the fax machine's telephone number and identification of the fax machine's user.
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<div class="mw-heading mw-heading2"><h2 id="Origins">Origins</h2></div>
<p>The CSID (and related TSID) are part of the modern landline fax specification. The CSID is often the same as the same machine's <a href="Transmitting_subscriber_identification" title="Transmitting subscriber identification">transmitting subscriber identification</a> (TSID). A CSID and TSID are usually programmed into a fax machine when the machine is set up.
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<div class="mw-heading mw-heading2"><h2 id="How_it_works">How it works</h2></div>
<p>When a fax machine receives a fax, it sends its CSID to the transmitting machine. The CSID is displayed on the sending fax machine and is usually recorded in the transmitting machine's log of sent faxes and printed on a report or confirmation of the fax transmission. This helps to confirm that the fax is being sent to the correct recipient.
</p><p>Computer software sometimes emulates the functions of a fax machine.
</p><p>A CSID and TSID are programmed into the software when it is configured. The software uses them when it sends or receives faxes.
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<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>
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</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.itu.int/rec/T-REC-T.30-200509-I/en">"ITU T.30 specification"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20131222003547/http://www.itu.int/rec/T-REC-T.30-200509-I/en">Archived</a> from the original on 22 December 2013<span class="reference-accessdate">. Retrieved <span class="nowrap">6 May</span> 2014</span>.</cite></span>
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<div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2></div>
<ul><li><a href="Caller_ID" title="Caller ID">Caller ID</a></li>
<li><a href="Transmitting_Subscriber_Identification" class="mw-redirect" title="Transmitting Subscriber Identification">Transmitting Subscriber Identification</a> (TSID)</li></ul>
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