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