Patent GB-1087642-A (GB)
Title: Improvements in or relating to apparatus for storing and retrieving information
IPC: G11C11/14
Filed: 1965-01-11
Abstract: 1,087,642. Pulse storage apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. Jan. 11, 1965 [Feb. 12, 1964], No. 1150/65. Heading H1T. [Also in Division H3] Apparatus for storing and retrieving information operated by non-coincident pulses and including non-destructive read out includes a memory element having four stable states. Each storage element comprises a film element 20 having two easy axes of magnetization arranged at right angles to each other, Fig. 1, the four directions having the binary values 0, 1<SP>1</SP> 0<SP>1</SP> and 1 as shown and the values 0, 0<SP>1</SP> and 1, 1<SP>1</SP> having the same binary significance. Associated with each storage element are three drive lines ABR, Figs. 2, 3 (not shown), A, B being arranged orthogonal and R at an angle to the element. When single pulses having a value between 0À27 Hk and Hk are applied to the lines there is no change in the binary digit stored, Fig. 5, although the directions of magnetization may be changed. Repetition of a particular pulse has the same effect as a single pulse on the state of magnetization of a storage element and are not effective to destroy or change the data stored, Fig. 9 (not shown). A sequence of two pulses the first on lines A or B and the second on line R is ineffective to change the initial state of magnetization of the element but during the sequence there are two flux changes which are used for read-out purposes. The pulse sequence ABR is employed to write a binary 0 and BAR to write a 1. Fig. 10 shows a two-dimensional nine element matrix. In order to write information into a particular element 20 the appropriate A and B selectors are energized and pulses are sent in the appropriate sequence over the respective A and B lines followed by a pulse from the reset driver R. Read out, Fig. 11 (not shown), is performed by first applying a timing pulse (48) to open gate 46 associated with the appropriate read out line 30 and coincidently applying a pulse to the A line coupled to the selected element 20. After the termination of pulse (48) a reset pulse 50 is supplied to the reset lines 23. If a " 1 " is stored the flux change acting on readout line 30 when the A line pulse is applied produces a signal in amplifier 45 and an output at timing gate 46. Since the latter is not activated during the reset pulse R fluxes acting on the read out line 30 due to the non-selected elements do not produce an output at 47. If a " 0 " is stored in the selected element there is no change in flux due to the A line pulse and hence no output at 47. Fig. 12 (not shown) illustrates a threedimensional array of elements. Figs. 6, 7 (not shown) illustrate the physical construction of the elements which comprises the drive wires superimposed but insulated from a disc of magnetic material on a substrate. Although a separate read out line is shown alternatively one of the drive lines may be used. Instead of being separate discs the elements may be a part of a continuous magnetic sheet. In the embodiment of Fig. 8 (not shown) the storage element comprises a pair of bi-stable electrical circuits the outputs of which provide four possible pairs of outputs, each pair representing one of the four different stable states.