Abstract: Clocking of Class IV partial response coded binary data is provided by way of circuit means that includes two analog threshold detectors. One detector is responsive to the analog read signal's positive-going amplitude corssing a a preset positive threshold value. The other detector is responsive to the read signal's negative-going amplitude crossing a preset negative value. The time of occurrence of both detector crossing transitions is phase-compared to a clock signal, and a phase error signal is generated for each detector, if a phase error exists. The two phase error signals are integrated by the use of a loop filter. The integrated phase error signal is then used to adjust the phase of a clock signal generator. The output of the clock signal generator is used to accurately clock, and to enable accurate recover of, the binary data that was originally encoded and written in accordance with the Class IV partial responsive coding convention.

Abstract: A magnetic disk provided with different digital bytes inside and outside of the center line of a magnetic track on the disk, and transducer and recording mechanism for detecting the passage of the digital bytes across the transducer and recording these bytes as the disk rotates so as to determine the distance the center of the transducer is spaced from the center line of the magnetic track. The recorded digital information is used for stepping a transducer stepping motor a distance corresponding to the stored digital information to move the transducer to have its center in correspondence with the center of the track. In one embodiment, the digital information is stored in a circular reference track adjacent the edge of the disk, and in another embodiment the digital information is stored in spiral tracks extending toward the center of the disk.

Abstract: A thin flexible magnetic disk rotatably disposed in a cartridge of rigid material and protected thereby. The disk is loosely mounted on a driving hub assembly and has an arrow shaped center hole surrounding a central round hub portion of the hub assembly. A drive pin is carried by the hub assembly and extends loosely through a corresponding hole located in the disk and spaced from the center of the hub assembly and located on a radial line preferably of about 90 degrees with respect to a radial line passing through the apex of the straight hole edges forming the arrow so that the disk is automatically centered on the hub assembly due to any restraint on the disk during its rotation.