Patent GB-1015323-A (GB)
Title: Magnetic flux control arrangements
IPC: H03K17/82
Filed: 1961-12-21
Abstract: 1,015,323. Magnetic information storage circuits. WESTERN ELECTRIC CO. Ltd. Dec. 21, 1961, [Dec. 30, 1960 (2)], No. 45785/61. Heading H3B.  A magnetic flux control arrangement comprises a plurality of magnetic storage legs associated with a drive leg, the storage legs each being associated with inductive means capable, when energized, of preventing a magnetic flux induced in the drive leg from passing through a storage leg, each storage leg including at discrete positions thereof magnetic storage regions. In Fig. 1 a magnetic plate is apertured to provide elements 14 on cross legs 13, and a drive leg 15, 16. The cross legs also have control apertures 20, 21. Flux induced in drive leg 15, 16 can pass through any of the cross legs unless current is flowing through one of the windings threading the control apertures 20, 21 of a cross leg. This current induces fluxes around apertures 20, 21 sufficient to saturate the material surrounding the apertures so preventing the passage of a drive flux. Initially a reset pulse is applied to winding 29, threading all the control apertures 20, 21; to clear the store by driving all parts to a neutral magnetic condition. Write pulse source 32 is then energized simultaneously with bit select conductors 22 and address windings x l , x 2 , x<SP>1</SP>1, x<SP>1</SP> 2 . Each address winding receives a positive pulse or no pulse so that drive flux is blocked in all but one of the cross legs 13. The bit conductors receive a negative pulse to write a " 1 " or no current to write a " 0." The write drive flux produced by energization of source 32 flows straight along the selected cross leg 13 except where a " 1 " is to be stored, where it flows round the U-portion of element 14 since the material around aperture 19 is saturated by current in conductor 22 (Fig. 4A). A further reset pulse is then supplied to winding 29 and all parts of the store are restored to the magnetically neutral condition, except where a " 1 " is stored. Here flux closes round element 14 (Fig. 4B). Read-out is achieved by addressing the store as before and pulsing read winding 43 to drive flux straight along the selected cross leg. This results in flux reversal in elements 14 which stored a " 1 " and a corresponding output occurs in winding 28. In a modification, Fig. 5, row selection is carried out by energizing address windings threading apertures 60, 61 during read-out. After read-out flux continues to flow through the selected cross-leg making further selection during writing unnecessary. Writing is achieved by energizing reset winding 69 simultaneously with bit conductors 62. In this case a positive pulse is used for a " 1 " and a negative pulse for a " 0." The reset flux restores the selected cross leg to a magnetically neutral condition except for clockwise or anticlockwise fluxes flowing around paths u, z, w and y. A read-out pulse in winding 73 then forces flux through a selected cross-leg to cause switching of flux in either minor leg y or minor leg z adjacent the left-hand aperture of each element 54 to induce an output in sensing conductor 65. The presence of a bit write current in a conductor 62 threading an element in an unselected cross leg does not destroy the stored information since flux is reversed only around the right-hand aperture of an element. Since the reset flux drives a selected cross leg to the threshold for switching the bit write pulses may have a low amplitude, but no upper limit is imposed. In a third embodiment (Fig. 7, not shown) the storage elements consist of the material surrounding single apertures in the cross legs and these apertures are threaded by both bit and sense conductors. Operation is similar to Fig. 5 and information is stored as clockwise or anticlockwise fluxes around apertures, but the bit write pulses must be limited in amplitude to prevent undesired switching in unselected rows. In this arrangement the absence of a bit current may be used for a " 0." In all the embodiments the major flux paths have the same cross-sectional area throughout and this area is at least equal to the sum of the areas of the minor flux paths on each side of an aperture. A multiplane arrangement is referred to.