Patent GB-790422-A (GB)
Title: Improvements in memory systems and switching arrangements therefor
IPC: G11C11/22
Filed: 1954-11-12
Abstract: 790,422. Electrical digital data storage apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. Nov. 12, 1954 [Nov. 17, 1953], No. 32810/54. Class 106 (1). [Also in Groups XXXIX and XL (a)] A memory system comprises a matrix of binary storage elements X<SP>1</SP>, Y<SP>1</SP>, X<SP>2</SP>, Y<SP>2</SP> . . . and a pair of cathode-ray tubes Sx, Sy having secondary emissive targets 10 and secondary emission collectors 17, the targets of the two tubes being respectively connected to the rows and columns of the matrix, the beams being deflected to select a desired X n Y m  co-ordinate and for applying different potentials to the collectors of the two tubes (since V10 is tied to V17 and 17 are connected to flip-flop 26) so as to produce a potential difference of one sign for writing and of the opposite sign for reading at the position X n Y m . The beams are turned on only when the scanning regimes reach the desired X n Y m  co-ordinates and are turned off at other times. The memory storage system comprises a plurality of ferro-electric capacitors having four stable states of polarization, two of which are utilized to represent the stored information in terms of binary numbers " one " and " zero; " a barium titanate crystal as dielectric will give the capacitor ferro-electric properties. The two binary states can be distinguished by (a) comparison with a fixed value standard capacitor or preferably (b) by the magnitude of the output current produced by the read-out pulse. In one form, Fig. 2, a single dielectric crystal F is used having two sets of parallel lines X, Y, formed by etching or deposition, on opposite sides thereof respectively, the elementary ferro-electric capacitors being formed where the X, Y lines cross. In writing, the beams of the two cathode-ray switch tubes are turned on by a positive pulse applied to 35 and the beams are deflected to the desired coordinates X<SP>1</SP>, Y<SP>1</SP> of the elementary capacitor to be stored. Two pulses, one of voltage E E amplitude + - and the other of - - are thus 2 2 applied simultaneously to capacitor X<SP>1</SP>, Y<SP>1</SP> by the electron beams and a binary " one" is stored in this capacitor, E being the coercive force. The beams are now cut off and the targets return to ground potential. To ensure that the tube targets 10 are at the correct potentials they are made secondary emissive, grids 17 collecting the secondaries; it is shown that the potentials of 10 follow those of 17, and the potentials of 17 which are equal and opposite are determined by flip-flop 26. The deflecting plates 15, 16 are energized by sawtooth or staircase scanning waveforms and the scanning frequency of Sy is made to be n times the scanning frequency of Sx, where n is the number of columns of the storage matrix, so that all the targets of tube Sy are scanned while the beam in tube Sx is positioned at one target. For reading a pulse is applied to 28 to alter the condition of the flip-flop, and the beams are then turned E on by a pulse to 35. A voltage of - - is now 2 E applied to X<SP>1</SP> and + - to Y<SP>1</SP>, by the respective 2 beams and an output representing the binary " one " is obtained across capacitor 20, or no output results for a binary " zero." Alternatively the reading may be achieved by sensing the current flow in the circuits of collectors 17. In a modification, Fig. 3, there are a plurality of separate ferro-electric capacitors F connected as shown to rows of double leads X and columns of single leads Y. The double leads X are wound oppositely at one end on magnetic core 40 and a secondary winding 45 deriving the output. Reading and writing are effected as in Fig. 2. A number of cathode-ray tubes of the form shown can be used to control and drive the co-ordinate channels of a plurality of matrices of the form of Figs. 2 or 3, as described with reference to Fig. 4 (not shown) for a serial type system, e.g. one using a cubical array of matrices. Paralleltype operation is also possible, a separate flipflop being provided for each matrix.