Patent GB-877731-A (GB)
Title: Improvements in or relating to magnetic memory devices
IPC: G11C11/12
Filed: 1958-07-23
Abstract: 877,731. Magnetic storage devices. WESTERN ELECTRIC CO. Inc. July 23, 1958 [Aug. 1,  1957], No. 23716/58. Class 38 (2). [Also in Groups XIX and XXXIX] Binary information is stored in a magnetic conductor in the form of a polarized helical magnetization having rectangular hysteresis loop properties, the helical magnetization being established by simultaneously passing currents through the conductor and through a coil encircling the conductor. As shown in Fig. 1, the helical flux path 11 can be initially determined by torsionally stressing an unannealed nickel conductor 10 mounted between a clamp 7 and a friction block 8. Alternatively, the flux path may be established by annealing the conductor in a helical magnetic field. Information is stored by applying coincident current pulses from sources 16 and 17 to the conductor and to the coil 12 respectively, each pulse by itself being insufficient to establish a remanent polarization in the flux path. The stored information is read-out by applying similar coincident pulses of the opposite polarity to those representing binary one, and a voltage is developed in the conductor which is detected by a device 18 if the remanent magnetization in the flux path is reversed. The hysteresis loop of the conductor in the helical flux path is shown in Fig. 6, and the negative slopes in the saturation regions are stated to be advantageous in that negative noise signals are produced. Instead of a solid conductor, a composite wire may be used comprising a non-magnetic inner part of copper or nickel-chromium alloy on which a nickel sheath is formed by plating, evaporation or extrusion. In a modification, Fig. 2, the current source 16 is connected to a second coil 12<SP>1</SP> instead of the conductor. The conductor is unstressed or otherwise physically treated in the remaining embodiments. As shown in Fig. 3, the flux follows one or other of two helical paths 11, 11<SP>1</SP> depending on the polarity of the current pulse applied to the conductor from source 16, the coincident pulse from source 17 being the same for each write operation. Read-out is effected by a pulse of opposite polarity applied from source 17 to the coil, the pulse amplitude being sufficient to shift the flux from a helical to an axial path. As before, the read-out signal is detected by device 18. In an alternative arrangement, Fig. 4, a helical flux is defined by the use of a helical winding 14 of magnetic material on a non-magnetic conductor. The same effect is obtained by providing a magnetic conductor with a helical groove 15, Fig. 5. A number of conductors 10 1 -10 n , Fig. 7, may be arranged in association with insulated row wires 12 1 -12 n  to form a co-ordinate storage array. Information is written into various sections of the conductors by write pulses applied simultaneously from sources 20 and 21. Subsequently the stored information is read-out row-by-row by a pulse of opposite polarity and appropriate amplitude from source 21, the read-out signals being taken from the ends of the conductors by a circuit 21. It is stated that the array may be formed by a weaving technique.