Patent GB-1017541-A (GB)
Title: Improvements in or relating to data storage apparatus
IPC: G11C13/06
Filed: 1963-08-12
Abstract: 1,017,541. Electric digital data storage. INTERNATIONAL BUSINESS MACHINES CORPORATION. Aug. 12, 1963 [Aug. 15, 1962], No. 31751/63. Heading G4C. [Also in Division H3] In a two core per bit data storage apparatus the data stored in a storage location is read out by directing polarized light on to the two magnetic elements of the store and observing the variations in the intensity of the light reflected from the two elements. As shown in Fig. 3, two thin magnetic film elements 10.1 and 10.2 are provided with a word conductor W in the direction of easy magnetization of the films X and a bit conductor B transverse to the direction of easy magnetization, the conductors being connected to pulse sources 22, 26 respectively and provided with delay means 20, 24. Read-out of the data is by a Kerr magneto-optical apparatus comprising light source 27, polarizer 29 and analyser 30 for detecting the reflected polarized light from the films. If at time to, Fig. 4, film 10.1 is in its " 0 " state and film 10.2 is in its " 1 " state then the light reflected from the films is of a given intensity as shown by the datum line. At time t 1  a positive pulse is applied to conductor W so as to apply a transverse field Ht to the film 10.1 rotating the magnetization vector away from the easy axis into alignment with the field Ht. The Kerr apparatus is positioned so that only the light rotated from reflection off the film in the " 1 " state will cause an increase in intensity in the light reflected from the film. Thus at time t 1 , there is an increase in intensity. At time t 2  a positive pulse is applied to conductor B so as to apply a field parallel to the easy axis of the film 10À1 in a direction such as to reverse the magnetization of the film 10.1 from the binary " 0 " state to the binary " 1 " state. At the termination of the pulse from source 22 at time t3 the magnetization of the film is established in the binary " 1 " state, and the intensity of the reflected light reaches its maximum value. At time t 4  the pulse on conductor W delayed by device 20 applies a transverse field to the film 10.2 tending to rotate the magnetization out of the binary " 1 " stable state and so decreasing the intensity of the light detected. The pulse on conductor B is similarly delayed by interval #B such as to apply a field directed along the easy axis of the film 10.2 at time t 5  rotating the magnetization further towards the " 0 " state. Upon the collapse at t 6  of the transverse field the film 10À2 is established in the binary " 0 " state and the reflected light is of the original intensity. If initially the film 10.1 is in the " 1 " state whilst film 10.2 is in the " 0 " state then on the application of the pulses to conductors W and B as in the previous example the intensity of the reflected light falls on the application of the pulse from 22, and consequently returns to the datum condition on the collapse of the transverse field, remains at the datum level until after the time #W when the intensity rises again at time t 4  before finally falling to the datum level after the termination of the transverse field at time t 6 . Thus by observing the intensity of the light during interval #W - (t 3  - t 1 ) the respective states of the films can be determined. In the magnetic memory of Fig. 5 (not shown) information is entered into a selected word by coincidently energizing a selected one of the word row conductors W and a selected one of the bit column conductors B to established one of the magnetic elements in the " 1 " state and the associated magnetic element in the " 0 " state. Read-out is accomplished by energization of the same word row conductor W and sequentially energizing each column conductor B to establish the magnetic films 10.1, 10.3, 10.5, 10.7 in the " 1 " state and the films 10.2, 10.4, 10.6, 10.8 in the " 0 " state. Alternatively all the bit conductors B may be energized simultaneously.