<div class="description">
Diagram depicting the passage of current in a needle telegraph system. One of the two main types of electromagnetic telegraphs, needle telegraphs use indicating needles moved electromagnetically as a means of displaying messages.</div>
1870 – 1900
This file was contributed to Wikimedia Commons by <a href="https://en.wikipedia.org/wiki/en:Science_History_Institute" class="extiw" title="w:en:Science History Institute"><span title="library, museum, and archive in Philadelphia, United States">Science History Institute</span></a> as part of a cooperation project. The donation was facilitated by the <a href="https://en.wikipedia.org/wiki/Digital_Public_Library_of_America" class="extiw" title="w:Digital Public Library of America">Digital Public Library of America</a>, via its partner PA Digital.<span style="text-align:left">
<ul><li><a rel="nofollow" class="external text" href="https://digital.sciencehistory.org/works/9k7bd7y">Record in source catalog</a></li>
<li>DPLA identifier: <a rel="nofollow" class="external text" href="https://dp.la/item/efc25d536fa975a4e3986cbed081ac97">efc25d536fa975a4e3986cbed081ac97</a></li>
<li>Science History Institute identifier: padig:SHI-9k7bd7y</li></ul></span>