Patent GB-1016254-A (GB)
Title: Improvements in or relating to magnetic devices
IPC: G06N20/00
Filed: 1961-12-18
Abstract: 1,016,254. Magnetic matrix stores; learning circuits. WESTERN ELECTRIC CO. Inc. Dec. 18, 1961 [Dec. 23, 1960], No. 45244/61. Headings G4C and G4R. [Also in Divisions H1 and H3] A storage device comprising a body of conductive magnetic material such as 4-79 Moly-permalloy has the writing and read-out currents passed directly through the body instead of using windings. Small, e.g. point, electrodes are used, and a multiple store is formed by providing a plurality of electrodes on opposing surfaces of a common body, or a plurality of electrodes on one surface and a ground plate on the opposite surface. Matrix store using bodies with ground plates. As shown in Fig. 3, a word store comprises conductive magnetic sheets 30 each having a matrix of small electrodes 32 1 -32 m  on one surface and a ground plate 31 on the opposite surface, discrete storage locations being defined by the magnetic material between each small electrode and the ground plate. To write a binary word, transistor gates 42 are selectively closed by signals from a bit-write selection switch 51 so as to earth the ground plates of those magnetic sheets 30 in which a binary one is to be written. At the same time a positive write pulse is applied from a word-write selection switch 35 over rectifiers 34 to a selected electrode, e.g. electrode 32 1 , on each of the magnetic sheets. A discrete storage location is therefore switched in each of the sheets having earthed ground plates. Read-out is effected by a word read selection switch 38 which passes a negative pulse through all the sheets 30 by way of rectifiers 37, a correspondingly-positioned electrode on each plate, and resistors 44 to earth. The selected storage locations are thus restored to the binary zero state, and characterizing outputs are produced across resistors 44 which control information utilization circuits 46 over amplifiers 45. Matrix store using bodies with a plurality of electrodes on both surfaces. As shown in Fig. 4a, a co-ordinate arrangement of copper strip electrodes 61a 1 -61b 5  and 62a 1 -62b 5  on opposite surfaces of a magnetic sheet 60 is provided, the electrodes 61a 1 -61a 5  and 61b 1 - 61b 5  being word electrodes attached to the sheet by PN and NP semi-conductor junctions respectively, Fig. 4b, which provide the circuit rectifiers. Two storage positions are used for each bit, the electrodes 62a 1 -62a 5  and 62b 1 - 62b 5  respectively defining the binary zero and binary one storage positions. To write a word, a positive pulse is applied to a selected word electrode 61a 1 -61a 5 . At the same time a selected electrode in each of the pairs of bit electrodes 62a 1 , 62b 1  . . . 62a 5 -62b 5  is earthed by closing a transistor gate 76 or 78. Only one gating circuit is shown, the selective connection to earth of a single bit electrode in a pair such as 62a 2 , 62b 2  being determined by an "0" or " 1 " pulse from a bit write selection switch 77 to a transistor gate. To read out, current is passed through the sheet in the opposite direction by applying a negative pulse from a word read selection switch 65 to a selected word electrode 61b 1 -61b 5 . Different currents are obtained in the two bit electrodes of each pair, the higher current value passing through the storage region in the binary zero state. This difference is detected by a differential transformer 70a which produces a positive or negative output pulse depending on the digit stored. Comparing two groups of random pulses for simultaneous coincidence. In this embodiment the body of conductive magnetic material consists of densely matted strands of conductive magnetic material 90, Fig. 5, to which many connections are randomly made by branched electrodes 91 1 -91n and 93 1 -93n. Each electrode branch such as 91b is insulated within the magnetic body up to the point 92 where electrical connection is made. The two random groups of pulses to be compared are obtained from sources A-N and A<SP>1</SP>-N<SP>1</SP> respectively, the A-N sources being positive and the A<SP>1</SP>-N<SP>1</SP> sources comprising switches capable of recurrently closing current paths to ground. Each time a coincidence occurs between the two groups of random pulses, current passes from a point 92<SP>1</SP> of positive potential within the body to an earthed point 92<SP>11</SP>. The current passes through a number of parallel paths i, i<SP>1</SP>, i<SP>11</SP> within the stranded body as shown in Fig. 6, and causes complete switching of the magnetic strands forming certain paths i and partial switching to various degrees of the magnetic strands forming other parallel paths i<SP>1</SP> of higher impedance. Subsequent current pulses between the same points 92<SP>1</SP>, 9211 complete the switching in some or all of the paths i<SP>1</SP> and partially switches the magnetic strands in further paths i<SP>11</SP>. Thus the number of complete and partially switched paths between any two points in the stranded body is representative of the number of current pulses passed in the same direction between those points. To read out, a positive voltage pulse is applied by an interrogate stepping switch 100 to each electrode 91 1 -91 n  in turn under the control of interrogate control circuits 102. Each voltage pulse produces a current in each of resistors 94 which are connected to respective electrodes 93 1 -93 n , and the magnitude of the resistive volt drops measured at terminals 95 1 -95 n  as the test proceeds is indicative of the degree of strand switching (and hence the number of current pulses registered) between any electrode 91 and any electrode 93. Thus the highest volt drop indicates the largest number of random pulse coincidences between a pair of electrodes and so on. When interrogation is completed, the stranded body is restored to an initial stable state by negative pulses from a reset switch 107. Alternatively, restoration may be effected by mechanically distorting the stranded body, Fig. 8 (not shown), so that the magnetic path conditions in the body are substantially disturbed and reorientated.