This looks interesting from what I can see, maybe someone can find the value in it. No it's not a riddle, it just caught my attention.
http://links.jstor.org/sici?sici=0080-4630%2819361102%29157:891%3c451:TEPOHP%3e2.0.CO%3b2-H&origin=ads (http://links.jstor.org/sici?sici=0080-4630%2819361102%29157:891%3c451:TEPOHP%3e2.0.CO%3b2-H&origin=ads)
tak
tak22, I found some research done on that subject that may come in handy for all of us working with frequencies and pulse motors.
DEPARTMENT OF PHYSICS
INDIAN INSTITUTE OF TECHNOLOGY MADRAS
CHENNAI, INDIA
MARCH 2007
http://www.physics.iitm.ac.in/research_files/synopsis/satyam.pdf