Abstract: A magnetic head reads data from reference zones on tracks at differing ra of a magnetic memory disc rotating at constant angular velocity. Each track includes at least one reference zone, each of which includes a plurality of initial cells. Each 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. 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 is generally the same amplitude as the further undulations. The undulations are susceptible to having varying amplitudes as the head is positioned at different positions of the disc. The peak amplitude of the further undulations, for one reference zone, is detected.

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 read/write head moves relative to magnetic discs having track addresses corded thereon in Gray code in a plurality of reference zones. The head is moved by an electric motor and reads information as the head is shifted from a starting track to a destination track. The address of the destination track is expressed in weighted, i.e., standard, binary code, and is stored in a register. The address of the head is read by a read element of the head from the recording tracks. In response to the initial and destination tracks, an intermediate track C, approximately halfway between the initial and destination tracks, is calculated. The head is accelerated from the initial track to the intermediate track by feeding a motor for driving the head with a constant current. In response to the head detecting the address of the intermediate track, the current supplied to the motor is reversed so that the head is decelerated. The calculations and comparisons are performed in the weighted, binary code.

Abstract: Binary coded address information is written by a magnetic head on a magnetic recording medium, such as a disc, as a plurality of tracks, each having an address associated with it. Each track includes a reference zone containing a plurality of individual cells equal to the number of bits in the address. Each cell represents a binary value and includes two binary state transitions, each of which can occur at one of only two positions. One transition of each cell in each zone occurs at the same position within the cell, with adjacent zones having alternating positions of this transition. The other transition in the cells in each zone occurs at either position to represent the binary values.

Abstract: Items of information written in a binary code on a plurality of magnetic c tracks are read by a magnetic head. The address for each track is written in a reference zone having a plurality of cells equal to the number of bits in the address. A constant frequency cyclic reference signal H is divided by logic pulses from the head to produce a signal SYNCHRO. The bit of each address is determined by combining the SYNCHRO signals and a pulse representative of the binary value of each bit that depends on the temporal position of a pulse within a period of signal SYNCHRO. The number of cells is counted, each time a bit is determined. The address is sampled bit by bit and transferred to a storage member throughout the counting and sampling operations.