Patent GB-889430-A (GB)
Title: Magnetic data store
IPC: G11C7/02
Filed: 1959-12-21
Abstract: 889,430. Magnetic storage devices. BURROUGHS CORPORATION. Dec. 21, 1959 [Dec. 24, 1958], No. 43416/59. Class 38 (2). [Also in Group XXXIX] In a magnetic storage device comprising a conductor overlaid with ferromagnetic material having a helical path of easy magnetization about the axis of the conductor, information is stored in discrete portions of the ferromagnetic material by passing currents coincidently through the conductor and through coils encircling the discrete portions, while the stored information in any portion is non-destructively read-out by applying a current of larger amplitude to a short coil which is able to change the magnetic state of a part only of the datarecording portion. As shown in Fig. 1, a data store comprises a pair 21a, 21b of copper conductors having helical wrappings 22a, 22b of a molybdenum-nickel-iron alloy strip of the order of one eight-thousandth of an inch thick. Discrete storage portions of the wrapped conductors are defined by spaced coils 23a, 23b. The store is initially cleared by a source 103 which applies a strong " 0 " magnetizing current to the coils 23a, 23b. A unidirectional magnetic field is thereby set up along the easy axes of the wrapped conductors. Portions of the fields are selected for reversal to a " 1 " storage state by applying writing currents of lesser strength simultaneously from source 103 and a data source 102, the combined currents in a coil and in a conductor at a selected portion being necessary to reverse the magnetic state along that portion of easy magnetization axis. To read the stored data in the portions, a strong current is selectively applied by a source 105 to a short coil 24a or 24b. This current is sufficient by itself to change the magnetic state locally from " 1 " to " 0," and since the coils 24a, 24b are short compared with 23a, 23b, only a central part of a data-recording portion is so magnetized. If " 0 " is stored in the interrogated portion no flux reversal can take place, but if the portion stores a " 1 " the flux of the central part is reversed and an output pulse is induced in the associated conductor. As the conductor pairs are embraced by common coils each conductor produces an output or not indicative in the data stored in a respective portion, the outputs passing over separate leads 31a, 31b to a data utilization device 104 which is operative only during the interrogation period. The reversed fluxes along the easy axes in the parts of the data-recording portions are restored to their previous state by a " 1 " restore current from source 105, this current being of sufficient amplitude to restore this state in conjunction with the existing " 1 " fields on either side of the interrogated part. This amplitude is not, however, sufficient by itself to drive part of an " 0 " storing portion to the " 1 " state in opposition to the " 0 " fields on either side of the part. Sequential control of these operations is effected by a signal source 101. In a modification, an inhibiting " 0 " current is applied to unselected conductors during the writing phase to prevent spurious data registration. The selected portions may then be switched by large coil currents from writing source 103 without the need for a " 1 " magnetizing current in the selected conductors. After interrogation, the switched parts may either be restored by direct current which is continuously operative in a coil extending the entire length of the conductors, or by direct current applied at all times except during the writing phase to separate auxiliary coils. An alternative arrangement uses magnetic material of low coercive force which permits automatic restoration of an interrogated part by the magnetic state existing in the parts on either side. These conductors may comprise tungsten wires plated with a nickel-iron alloy coating which has a helical easy magnetic path. A copper wire plated with a magnetic layer and twisted to form the easy helical path may also be used in either embodiment.