Abstract: A "floppy" disc digital magnetic storage apparatus or subsystem includes a number of interrelated features permitting greatly increased data storage and good access time, while using relatively inexpensive parts. The features contributing to the greatly increased storage capacity include arrangements for providing one hundred tracks per inch, and for holding tolerances so that the position of the magnetic head in the radial direction is maintained within the required value of plus or minus 1.7 thousandths of an inch.

Abstract: A magnetic recording system is provided which encodes four bits of an eight bit "byte" at a time, and is thus compatible with most general purpose data processing systems which process eight bit bytes. Also, the special magnetic recording code groups which are formed have at least two "0's" between each "1", and always include at least one "1" in each code group, thereby increasing the average frequency of magnetic transitions and reducing the requirements for the phase lock oscillator timing circuit compared to previous methods. In addition, the conversion circuitry for converting from the short data groups to the longer code groups is simplified by the use of a small "Programmable read Only Memory" or "PROM" and "EXCLUSIVE-OR" circuit logic to insure proper code bit groupings of "1's" and "0's" within each code group and at the transitions between code groups.