Editing Relay (section)

== History ==

In 1809 an electrolytic relay was designed as an alarm for an electrochemical telegraph by [[Samuel Thomas von Sömmerring]].<ref>{{cite web | url=https://mysite.du.edu/~jcalvert/tel/morse/morse.htm#H1 | archive-url=http://web.archive.org/web/20210126030133/https://mysite.du.edu/~jcalvert/tel/morse/morse.htm#H1 | archive-date=26 January 2021 | title=The Electromagnetic Telegraph }}</ref>

Electrical relays got their start mainly in application to [[telegraph]]s. American scientist [[Joseph Henry]] is often cited to have invented a relay in 1835 in order to improve his version of the [[electrical telegraph]], developed earlier in 1831.<ref>{{cite book|title=Icons of Invention: The Makers of the Modern World from Gutenberg to Gates|publisher=ABC-CLIO|url=https://books.google.com/books?id=WKuG-VIwID8C&q=Invention+of+the+relay&pg=PA153|page=153|isbn=9780313347436|year=2009}}</ref><ref>{{cite web|title=The electromechanical relay of Joseph Henry|publisher=Georgi Dalakov|url=http://history-computer.com/ModernComputer/Basis/relay.html|access-date=2012-06-21|archive-url=https://web.archive.org/web/20120618121911/http://history-computer.com/ModernComputer/Basis/relay.html|archive-date=2012-06-18|url-status=dead}}</ref><ref>{{cite book|title=Scientific American Inventions and Discoveries: All the Milestones in Ingenuity--From the Discovery of Fire to the Invention of the Microwave Oven|publisher=John Wiley & Sons|url=https://books.google.com/books?id=pDbQVE3IdTcC&q=relay+Joseph+Henry+1835&pg=PA311|page=311|isbn=9780471660248|date=2005-01-28}}</ref><ref>{{cite book| title=Joseph Henry: His Life and Work| url=https://archive.org/details/josephhenryhisli0000coul| url-access=registration| author=Thomas Coulson | publisher =Princeton University Press| location = Princeton| year = 1950}}</ref> However, Henry never published any of these experiments and dating for his relay experiments is based solely on the words of Henry himself and his students, often decades later.<ref>{{cite book | url=https://books.google.com/books?id=2FXkBgAAQBAJ&q=joseph+henry+relay+1835&pg=SA4-PA6 | title=Practical Electronics: A Complete Introduction: Teach Yourself | isbn=978-1-4736-1408-6 | last1=Cooper | first1=Andy | date=5 May 2016 | publisher=John Murray Press }}</ref><ref> {{cite journal |url=https://www.worldradiohistory.com/Archive-Bell-System-Technical-Journal/30s/Bell-1932c.o.pdf |title=The Electrical Discoveries of Joseph Henry |first1=H.S. |last1=Osborne |first2=A.M. |last2=Dowling |journal=Bell System Technical Journal |issue=Supplement |date=July 1932|volume=11 |pages=1–22 |doi=10.1002/j.1538-7305.1932.tb00627.x }}</ref>

In March 1837 [[Edward Davy]] deposited a letter with the British Secretary for the Society of Arts containing his ideas for an electromagnetic relay, which, even if it was not the first, was considered more practical than previous designs, being a ‘make-and-break’ type rather than being based on the use of mercury. He did this two months before [[Charles Wheatstone]] and [[William Fothergill Cooke|William Cooke]] filed their first patent for their telegraph system and would file a patent for the same idea a year later.<ref>{{cite web | url=https://books.google.com/books?id=0Mo3AAAAMAAJ&q=Renewer | title=A History of Electric Telegraphy, to the Year 1837 | last1=Fahie | first1=John Joseph | date=1884 }}</ref><ref>{{cite book |first1=Donald |last1=McDonald |first2=Leslie B. |last2=Hunt |title=A History of Platinum and its Allied Metals |date=January 1982 |page=306 |publisher=Johnson Matthey Plc |isbn=0905118839}}</ref>

However, an official patent was not issued until 1840 to [[Samuel Morse]] for his telegraph, which is now called a relay. The mechanism described acted as a digital amplifier, repeating the telegraph signal, and thus allowing signals to be propagated as far as desired.<ref name="Patent1647">{{cite patent|country=US|number=1647|title=Improvement in the Mode of Communicating Information by Signals by the Application of Electromagnetism|pubdate=June 20, 1840|inventor1-last=Morse|inventor1-first=Samuel E.B.|url=http://www.google.com/patents?id=Xx5AAAAAEBAJ&printsec=abstract&zoom=4&dq=1647}} {{Cite book |url=http://www.google.com/patents?id=Xx5AAAAAEBAJ&printsec=abstract&zoom=4&dq=1647 |title=Patent US1647 - IMPROVEMENT IN THE MODE OF COMMUNICATING INFORMATION BY SIGNALS BY THE - Google Patents |access-date=September 6, 2011 |archive-date=May 24, 2012 |archive-url=https://web.archive.org/web/20120524081816/http://www.google.com/patents?id=Xx5AAAAAEBAJ&printsec=abstract&zoom=4&dq=1647 |url-status=bot: unknown }}</ref>

The word ''relay'' appears in the context of electromagnetic operations from 1860 onwards.<ref>{{cite web|title=Relay|url=http://www.etymonline.com/index.php?allowed_in_frame=0&search=relay&searchmode=none|website=EtymOnline.com}}</ref>