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Hook flash
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<h2 id="history">History</h2> <p>The <a href="/facts/Telephone_hook/UxEj6H0w">switchhook</a> is the device that senses whether the handset or receiver is in its cradle. The term "flash" originated from the <a href="/facts/Cord_circuit/9jhUTYC6">cord circuit</a> of the early <a href="/facts/Telephone_switchboard/Xu1xeItl">telephone switchboard</a> that telephone company operators used to connect calls. The <a href="/facts/Calling_party/Dcw0V4hJ">calling party</a> and <a href="/facts/Called_party/TxXCTuQT">called party</a> each had an indicator light on the <a href="/facts/Local_loop/rSRfLPaq">cord circuit</a>. When the subscriber cycled the telephone on-hook/off-hook, the light would flash. Actors in old movies often demonstrate this method, seeking the operator's attention. The user performs a <i>tap-tap-tap</i>. When an operator comes on the line, the actor says, "Hello? Operator? We've been cut off." Then the operator attempts to reestablish the connection. The flashing light of this early equipment is the origin of the phrase "flashing the switchhook". </p><p><a href="/facts/Centrex/eUUxYVrq">Centrex</a> telephones added a hook-flash button in the 1960s after some users attempted the attendant-recall function incorrectly and disconnected their calls inadvertently. </p> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>https://www.etsi.org/deliver/cept/20/2009CS.PDF [bare URL PDF] <a href="https://www.etsi.org/deliver/cept/20/2009CS.PDF" target="_blank">https://www.etsi.org/deliver/cept/20/2009CS.PDF</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>https://www.etsi.org/deliver/cept/20/2009CS.PDF [bare URL PDF] <a href="https://www.etsi.org/deliver/cept/20/2009CS.PDF" target="_blank">https://www.etsi.org/deliver/cept/20/2009CS.PDF</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>"GLOSSARY OF TELEPHONE TERMS - MF, Code "C"". <a href="https://www.britishtelephones.com/glossary.htm" target="_blank">https://www.britishtelephones.com/glossary.htm</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> </ol>