Patent GB-912643-A (GB)
Title: Magnetic memory devices and arrays
IPC: G11C11/04
Filed: 1960-01-29
Abstract: 912,643. Circuits employing bi-stable magnetic elements. WESTERN ELECTRIC CO. Inc. Jan. 29, 1960 [Feb. 4, 1959], No. 3270/60. Class 40 (9). [Also in Group XIX] Binary information is stored in magnetic form in discrete regions along a magnetic wire having a helical flux path as described in Specification 877,731, the ends of the wire being connected by balancing impedances comprising centre-tapped transformer windings to the ends of an adjacent electrical conductor for the purpose of neutralizing spurious outputs. As shown in Fig. 1, a storage array comprises spaced magnetic wires 10 1 -10 n  each connected by centre-tapped transformer windings 13 to an adjacent conductor 12 and arranged in planes a, b . . . y, z. All the wires are continuously biased by current from a bias source 33 applied to the transformer centre-taps 14, the discrete regions then having stable remanent states 37 or 38, Fig. 3, according to the information stored. To write information into a plane, writing pulses are applied to the magnetic wires by way of the transformer centre taps from selected write-current pulse sources 17, and at the same time a vertical plane of wire regions is energized by a pulse in a selected looped conductor 26 1 -26 m  from a write-read pulse source 27, coincidence of currents at a region being necessary to change its stable state from point 37 (binary zero) to point 38 (binary one). For reading out, a pulse of opposite polarity from source 27 is applied to a selected loop conductor 26 1 -26 m  and the magnetic wires are unenergized, the same pulse amplitude being used as for writing in view of the now favourable bias current. As a result, discrete regions associated with the energized conductor are changed to the opposite remanent point 37 (binary zero) and output pulses are induced in the respective magnetic wires. These pulses pass in horizontal planes over the transformer windings 13 through series circuits comprising magnetic wires of other planes a, b . . . y, z, and are finally applied over transformer secondary windings 21 to respective output detection circuits 23 1 -23 n . During read-out, spurious outputs induced in the magnetic wires of the stores due to nearby flux reversals are suppressed by the provision of conductors 12, the equal voltages induced in an associated wire and conductor cancelling in the closed loop circuit formed by the transformer windings 13. In addition a " shuttle " suppression circuit is provided for overcoming spurious outputs due to flux excursions in magnetic wires between remanent point 37 and saturation point 40 of the same polarity, this type of output arising from non-rectangularity of the magnetization characteristic. The shuttle circuit comprises a further magnetic wire 11 and conductor 12 in each plane a, b ... y, z, the wire and associated conductor pairs being joined by transformer centre-tapped windings as before. No writing connections are provided, however, so that each shuttle wire remains in the binary zero state at all times. During read-out, flux excursion then takes place between points 37 and 40, and the minor outputs induced are applied through a series path of shuttle magnetic wires to a shuttle reference amplifier 25. This amplifier output is applied to transformer windings 21 in the output detection circuit and neutralizes the shuttle voltages induced in the storage magnetic wires 10 1  . . . 10 n . As all the transformers in a horizontal plane are effectively connected in series, the last one is terminated by a characteristic impedance 20. The write-read current pulse source 27 may be a co-ordinate array of magnetic cores, Fig. 2 (not shown). Mention is made of moulding a plurality of spaced magnetic wires in an insulating, preferably plastic, tape or belt.