Abstract: A disc of a magnetic disc cartridge is braked while the cartridge is outside of a receptacle of a magnetic disc memory unit by a radially extending leaf spring mounted on a wall of the cartridge so it has a free end engaging an aperture in a drive platter. The drive platter has an aperture that is engaged by a drive post of a drive disc connected to the memory drive shaft while the cartridge is inserted in the receptacle. The leaf spring is positioned so that the free end thereof is lifted out of the aperture by a post fixedly mounted on the memory unit to release the brake member while the cartridge is in place in the receptacle.

Abstract: Binary bits on a magnetic storage medium are read by a magnetic head that moves at approximately constant speed relative to the medium. The medium includes several elongated adjacent magnetic tracks, each including a succession of longitudinally positioned polarized magnetic flux variations arranged in elemental areas of equal length along the length of each track. Adjacent areas are susceptible to having like and unlike magnetic flux polarizations. The head and tracks are positioned so the head straddles a pair of the tracks and is simultaneously responsive to flux variations in the straddled tracks. The head and track move relative to each other so the head is responsive to successive flux variations as time progresses. The areas are arranged so there is always a magnetic flux polarization transition at predetermined equi-spaced positions along the track length at a boundary between a pair of elemental areas. The transition direction at each boundary indicates a binary bit value.

Abstract: Errors in reading data with a magnetic head from reference zones on tracks t differing radii of a magnetic memory disc rotating at constant angular velocity are determined. Each track includes at least one reference zone including a plurality of initial cells. Each initial cell has magnetic flux variations which when read by the head result in a first waveform that includes undulations enabling the head to be properly servo controlled to a position over the center of the track and a further undulation that is distinguishable from the head positioning undulations because it has a larger amplitude. The initial cells are followed by plural binary bit representing data cells each having magnetic flux variations which when read by the head result in a second waveform including a data representing undulation that has approximately the same amplitude as the further undulations. The undulations are susceptible of having varying amplitudes as the head is positioned at different positions of the disc.

Abstract: A magnetic recording disc includes a plurality of sectors, each of which includes a plurality of data tracks and a reference zone containing information for identifying the data tracks. Some of the sectors are standby sectors containing information which would normally be contained in the sectors containing the data tracks. The reference zones of all sectors contain binary fault indicating bits which indicate whether a particular sector contains faults, and parity bits having values dependent on the location of the parity bit and the value of the fault bit at the same location as the parity bit. A data processor commands a read out head for the disc to be located at a particular position. From the command position of the data processor and the value of the fault bit, the data processor computes an expected parity bit value. The expected parity bit value is compared with the parity bit value read from the disc to provide an indication as to whether the fault bit is accurate.

Abstract: A device for reading a binary coded magnetic recording. The device includes a reading head producing a reading signal, a digitizer, and a mechanism for modulating the reading signal to substantially reduce distortion caused by the physical characteristics of the reading head and magnetic recording.