Self-clocking nrz recording and reproduction system

Claim 1

In a system for storing and retrieving data in a magnetic medium according to a binary code wherein first and second data quantities are represented by first and second discrete flux conditions in the medium; data writing means responsive to input data to produce a substantially continuous data pattern in the medium at a clocked rate thereby to produce a sequence of data cells each having a discrete flux condition; means operatively associated with said writing means for interrupting the data pattern after every n cells and inserting a sync cell having a flux condition which is opposite to the flux condition of the preceding cell; data reading means responsive to said flux conditions for producing output representative thereof and at a rate corresponding to said clock rate thereby to define discrete data bits corresponding to said data cells; and synchronizing means including a clock source operatively associated with said reading means for timing the reading of said flux conditions, said synchronizing means including means for resetting the clock source after the reading of said sync cell flux condition; and means responsive to the flux transitions in the data cells immediately proximate the sync cell for adjusting the timing of said clock source to compensate for sync cell shifting due to pulse crowding.