Disclosed is a laser doppler velocity system that can easily change a focal length of laser beam, in order to measure the velocity of fluid. The initiator systems are useful for initiating polymerization of at least one monomer to form polymerized compositions. The height of the ripples on the receiving surface having a period of 200 to 500 microns is no more than 0. The feedback loop includes a non-linear transform circuit for each upper and lower output device to prevent the bias current reducing to zero. The method can, further comprise the steps of: displaying the previously dictated text in a first display window; sequentially displaying in a second display window a portion of the previously dictated text including the sequentially highlighted word; and, sequentially displaying in a third display window within the second display window the sequentially highlighted word. The insertion of an additional string array between the input terminals and the wiper, allows for the disconnection of a common string array and for the independent calibration of the resistance between each input terminal and the wiper.