A disc tolerance ring for centering a disc clamp on a spindle hub. The inputs may be disposed upon a retractable or removable surface so that they have an operative position, in which they are within reach of the fingers, and an inoperative position, in which they are stowed outside reach of the fingers, but in a manner otherwise convenient to the user. The call associated with the first prepaid services account may be any type of communication, including a telephone call, a message delivered via the internet, or any other voice or data message. The relative movement between the chart and the distortion region is triggered by different kinds of inputs from the user including, tilting of the device, swiping with a pointing device and selecting a particular data point. The front cooler is joined to a tilting mechanism having a lever arm pointing in the direction of travel of the tractor. An objective function is utilized to determine values for the feature extractor parameters and the acoustic model parameters.