Coding method for magnetic data storage - using lf signal between data groups which are recorded by frequency or phase displacement (HU 28.1.81)

摘要

The reliability of recording and recovery of data on magnetic media is enhanced by using, in conjunction with conventional saturated frequency or phase displacement coding techniques, an interval between groups of code in which a signal is recorded at a lower frequency than the data recording frequency. This signal indicates clearly the start and finish of each code group and prevents noise introducing errors in the interval. The signal may also be used for rate correction of the data by measurement of its frequency.