Patent GB-754891-A (GB)
Title: Magnetic core memory system
IPC: G11C8/02
Filed: 1954-07-21
Abstract: 754,891. Circuits employing bi-stable magnetic elements. RADIO CORPORATION OF AMERICA. July 21, 1954 [Aug. 20, 1953], No. 21320/54. Class 40 (4). [Also in Group XIX] A magnetic memory device comprises memory planes or spaced surfaces each providing magnetic cores for storage of information, and a memory core selection switch having magnetic switch cores and output coils which correspond in number to the number of memory cores in a plane or surface. As shown in Fig. 2, toroidal memory cores 10, which can be in either an " N " or the opposite, " P ", saturation condition to represent binary digits, are positioned in rows and columns of sheets 22 of non-magnetic material. The switch comprises a closely packed group 26 of similar sheets and a switch core is selected by energizing appropriate row and column coils 30 and 32, a biasing coil 34 causing the core to return to its original condition when the energization ceases. The switch output coils 36 comprise straight conductors each of which is threaded through corresponding memory cores, one in each plane or sheet 22. Also, a coil 38 is threaded through all the cores in a plane so as to be inductively coupled thereto. A binary number may be written in the memory by first selecting a series of memory cores by means of the switch, and subsequently selectively energizing the plane coils 38. The selected switch core is driven from condition " N " to " P " and the current in the associated coil 36 drives all the memory cores to " P ". When the selected switch core is restored by the coil 34, an opposite and weaker current is induced in the coil 36 which, only if augmented by energization of a plane winding 38, will cause a memory core to return to N. For reading a memory core, it is again driven to " P " by the switch; if it were previously in condition " N " a large output is induced in the corresponding plane winding which may be used to restore the core to " N ". Fig. 3 shows a reading and writing circuit for a single memory plane, the coil 38 being coupled to " read " and " write " transformer cores 40, 42. An output pulse induced in 38 during reading is applied through the " read " transformer to output means (not shown) and via an amplifier 46 to a bi-stable trigger circuit 48 whose output then opens pentode gate 54 to a clock pulse from source 60. Such pulse is applied through amplifier 62, delay circuit 64 and amplifier 66 to the " write " transformer to induce an "N"/2 pulse in coil 38 at a time when the memory core being read also receives an "N"/2 pulse from the switch 36. The memory core is thus restored to its original condition " N ". When the pulse from delay 64 ceases, the core 42 is restored to its initial condition by bias coil 70, thus inducing a "P"/2 pulse in coil 38 which is detected by the " read " transformer and resets the trigger 48. To write " N " in a memory core the trigger is actuated by a pulse from source 72 instead of from amplifier 46. In a modified writing procedure, the selected memory cores are all driven to " P " and are restored to " N " by the switch output "P" coil unless an inhibiting pulse is applied 2 from the plane coils. A modified memory device has a switch core plane at each end, the switch cores in each such plane being connected to alternate cores in a memory plane, thus enabling switch cores larger than the memory cores to be used. In another form (Fig. 5, not shown), pairs of memory planes are each connected to a push-pull type of circuit whereby corresponding cores in the pair are always in opposite conditions, thus maintaining a constant load on the switch. Various ways of constructing a core plane are described. For example, as illustrated in Fig. 6A, positioning pins 110 are driven in a matrix array into base plate 112. A removable perforated plate 114 is then placed on the base plate, a core 10 is placed over each pin, and the space between the cores is filled with plastic material 116. When this material hardens, the plate 114 may be picked up and separated from the core plane.