The invention provides an apparatus for controlling the rotation of a rotating body in a recording and/or reproducing apparatus. First, the apparatus detects the rotational speed of the rotating body, as it is driven by a DC motor. Detection is in terms of a frequency which is n times the speed, in which...http://www.google.co.uk/patents/US3934269?utm_source=gb-gplus-sharePatent US3934269 - Apparatus for controlling the rotation of a rotating body in a recording and/or reproducing apparatus
