Abstract: Method and apparatus for dividing a track on a magnetizable information storage disc into sectors by writing sector identification information into the track. In order to optimize the storage capacity of a track on a magnetizable information storage disc the track is first filled with information bytes in response to the occurrence of the leading edge of an index pulse (a) derived from the disc in such manner that a predetermined number of bytes fill a portion (ix) of the track, followed alternately by sector identification bytes and further bytes defining the data field of the relevant sector in portions SK and DT respectively until the final group of sector identification bytes has been written into portion SKn, followed by further bytes into portion z until the leading edge of the next index pulse occurs.

Abstract: During the reading of serial data signals, for example, from a so-termed magnetic floppy disc, a synchronized condition between the local oscillator of the reading device and the timing of the data stream must be reached as quickly as possible after the start of the read operation. When the initial synchronization has been reached, readjustment of phase and frequency may take place only slowly, because the instants at which the actual signal transitions occur may exhibit a large spread with respect to the nominal instants. Therefore, during a synchronization operation an element of a read clock pulse train is applied to the phase comparator at each status transition of the medium as well as at further instants. The data sample signal of the clock pulse generator is applied at twice the bit frequency to the other input of the phase comparator.