&quot;Sixty cycles has ever since been the standard for alternating current&quot;<p>That&#x27;s incomplete. Los Angeles, for example, had 50 Hz power until the late 1940s.<p>(For references: <a href="http:&#x2F;&#x2F;www.oldradio.com&#x2F;archives&#x2F;stations&#x2F;LA&#x2F;mtwilson3.htm" rel="nofollow">http:&#x2F;&#x2F;www.oldradio.com&#x2F;archives&#x2F;stations&#x2F;LA&#x2F;mtwilson3.htm</a> says &quot;It is interesting to note that until early 1949 the Southern California Edison Company supplied 50 Hertz power to Mt. Wilson.&quot; and <a href="http:&#x2F;&#x2F;www.earlytelevision.org&#x2F;national_schools_camera.html" rel="nofollow">http:&#x2F;&#x2F;www.earlytelevision.org&#x2F;national_schools_camera.html</a> &quot;It should be noted that Los Angeles used 50 Hz power at that time.&quot;)