Editing Harry Nyquist (section)

== Technical contributions==
[[File:UND Nyquist Memorial.JPG|thumb|Memorial to Harry Nyquist at the University of North Dakota's College of Engineering and Mines]]As an engineer at Bell Laboratories, Nyquist did important work on thermal noise ("[[Johnson–Nyquist noise]]"),<ref>{{cite journal | last=Nyquist | first=H. | title=Thermal Agitation of Electric Charge in Conductors | journal=Physical Review | publisher=American Physical Society (APS) | volume=32 | issue=1 | date=1928-07-01 | issn=0031-899X | doi=10.1103/physrev.32.110 | pages=110–113| bibcode=1928PhRv...32..110N }}</ref> the stability of [[feedback]] [[amplifier]]s, telegraphy, [[fax|facsimile]], television, and other important communications problems.  With [[Herbert E. Ives]], he helped to develop AT&T's first facsimile machines that were made public in 1924. In 1932, he published a classic paper on stability of feedback amplifiers.<ref>{{cite journal|first=H. |last=Nyquist|title=Regeneration theory|journal=Bell System Technical Journal|volume=11|pages=126–147|year= 1932|doi=10.1002/j.1538-7305.1932.tb02344.x|s2cid=115002788 |url=https://archive.org/details/bstj11-1-126}}</ref>  The [[Nyquist stability criterion]] can now be found in many textbooks on feedback control theory.

His early theoretical work on determining the bandwidth requirements for transmitting information laid the foundations for later advances by [[Claude Shannon]], which led to the development of [[information theory]].  In particular, Nyquist determined that the number of independent pulses that could be put through a telegraph channel per unit time is limited to twice the [[Bandwidth (signal processing)|bandwidth]] of the channel, and published his results in the papers ''Certain factors affecting telegraph speed'' (1924)<ref>{{cite journal|last=Nyquist|first= Harry|title=Certain factors affecting telegraph speed|journal=[[Bell System Technical Journal]]|volume= 3|pages=324–346|year=1924|issue= 2|doi= 10.1002/j.1538-7305.1924.tb01361.x|s2cid= 51630538|url=https://archive.org/details/bstj3-2-324}}</ref> and ''Certain topics in Telegraph Transmission Theory'' (1928).<ref>{{cite journal | last=Nyquist | first=H. | title=Certain Topics in Telegraph Transmission Theory | journal=Transactions of the American Institute of Electrical Engineers | publisher=Institute of Electrical and Electronics Engineers (IEEE) | volume=47 | issue=2 | year=1928 | issn=0096-3860 | doi=10.1109/t-aiee.1928.5055024 | pages=617–644| bibcode=1928TAIEE..47..617N }} [https://web.archive.org/web/20060706192816/http://www.loe.ee.upatras.gr/Comes/Notes/Nyquist.pdf Reprint as classic paper in: ''Proc. IEEE, Vol. 90, No. 2, Feb 2002''].</ref>  This rule is essentially a [[Duality (mathematics)|dual]] of what is now known as the [[Nyquist–Shannon sampling theorem]].